МЕГАГРАНТЫ

Научная лаборатория оптической когерентной томографии

О лаборатории

Наименование проекта Разработка новых технологий оптической когерентной томографии для задач индивидуальной терапии рака

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№ договора:
14.B25.31.0015

Наименование ВУЗа:
ГБОУ ВПО "Нижегородская государственная медицинская академия" Министерства здравоохранения Российской Федерации

Области научных исследований:
Медицинские технологии


Целями проекта являются:

1. разработка технологий многофункционального спектрального метода оптической когерентной томографии (МФ ОКТ) и проведение доклинических и клинических исследований по выявлению специфических маркеров и показателей ответа опухоли на различные виды противоопухолевого лечения, что обеспечит реализацию индивидуальной терапии рака.

2. создание высокотехнологичной лаборатории «Оптической когерентной томографии», способной решать задачи разработки современных методов оптической диагностики, мониторинга и индивидуализации лечения онкологических заболеваний, что обеспечит создание конкурентноспособных инновационных диагностических систем.

Задачами проекта являются:

1. Разработка многофункциональных спектральных методов ОКТ для обеспечения чувствительной оценки ответа тканей на различные виды терапии рака в ближнем ИК диапазоне с целью создания технологической платформы для доклинических и клинических исследований, для выработки показателей и устойчивых биомаркеров ответа тканей на различные виды терапии рака.

2. Проведение доклинических исследований по морфологической и патофизиологической индентификации данных ОКТ изображений. Проведение мониторирования индукции опухоли, ее роста и ответа на лечение на модельных животных с использованием многофункциональной ОКТ и других методов биофотоники.

3. Проведение клинических исследований с целью выявления OКT критериев эффективности противоопухолевой терапии по ответу на лечение и определения показаний к разным видам терапии.

 

 

Ведущий учёный

vitkin 

ФИО: Виткин Илья Алекс

 

Ученые степень и звание:
Доктор наук в области медицинской физики, профессор

Занимаемая должность:

Профессор кафедры медицинской физики и радиационной онкологии Университета Торонто, старший научный сотрудник отдела Биофизики и Биоимиджинга Института Рака (Онтарио) и физик по радиационной медицине Клиники им. принцессы Маргарет (Торонто, Онтарио, Канада).

Области научных интересов:

- Медицинская физика и биоимиджинг;
- Применение лазеров в медицине;
- Оптическая когерентная томография (ОКТ) биотканей.

Научное признание:

• Техническое развитие ОКТ (многоканальная ОКТ, Доплеровская ОКТ)
• Техническое развитие спекл-функциональной визуализации микроциркуляторного русла с помощью ОКТ.
• Использование в доклинических экспериментах и клинической онкологии визуализации микроциркуляторного русла биотканей с помощью ОКТ.
• Развитие и использование поляризационных оптических методов в оценке биотканей.
• Почетный член Американского оптического общества (OSA) и Международного общество оптики и инженерии (SPIE)
• Международный лектор OSA и SPIE.
• Редактор международного журнала «Оптикс Леттерс (Optics Letters)», ведущего в области лазеров и оптики.
• Эксперт грантовых комитетов разных стран (Канады, США, Голландии, Германии, Франции, Австралии, Новой Зеландии) в области оптики и онкологии.
• Премии Клиники им. принцессы Маргарет (Торонто, Канада) 2008 и 2013 год за исследовательскую работу в области радиационной медицины.
• Премия премьер-министра Канады за исследовательское мастерство (2003-2008).
• Автор 130 статей и 10 глав книг в области биофотоники.

  Optics Letters Munce NR, Mariampillai A, Standish BA, Pop M, Anderson KJ, Liu GY, Luk T, Courtney BK, Wright GA, Vitkin IA, Yang VXD Electrostatic forward-viewing scanning probe for optical coherence tomography using a dissipative polymer catheter 2008, 33, 7
  Medical Physics Rink A, Lewis DF, Varma S, Vitkin IA, Jaffray DA Temperature and hydration effects on absorbance spectra and radiation sensitivity of a radiochromic medium 2008, 35, 10
  Journal of Biomedical Optics Wood MFG, Côté D, Vitkin IA Combined optical intensity and polarization methodology for analyte concentration determination in simulated optically clear and turbid biological media 2008, 13, 4
  Optics Letters Mariampillai A, Standish BA, Moriyama EH, Khurana M, Munce NR, Leung MKK, Jiang J, Cable A, Wilson BC, Vitkin IA, Yang YXD Speckle variance detection of microvasculature using swept-source optical coherence tomography 2008, 33, 13
  Optics Express Liu GY, Mariampillai A, Standish BA, Munce NR, Gu X, Vitkin IA High power wavelength linearly swept mode locked fiber laser for OCT imaging 2008, 16, 18
  Applied Optics Spirou GM, Mandelis A, Vitkin IA, Whelan WM Frequency domain photothermoacustic signal amplitude dependence on the optical properties of water: Turbid polyvinyl chloride-plastisol system 2008, 47, 14
  Optics Communications Guo X, Wood MFG, Vitkin IA A Monte Carlo study of penetration depth and sampling volume of polarized light in turbid media 2008, 281, 3
  Clinical Cancer Research Lam S, Standish BA, Baldwin C, McWilliams A, leRiche J, Gazdar A, Vitkin IA, Yang VXD, Ideda N and MacAulay C In vivo optical coherence tomography imaging of pre-invasive brocnchial lesions 2008, 14, 7
 

Journal of Biomedical Optics

Ghosh N, Wood MFG, Vitkin IA Mueller matrix decomposition for extraction of individual polarization parameters from complex turbid media exhibiting multiple scattering, optical activity, and linear birefringence 2008, 13, 4
  Cancer Research Standish BA, Lee KKC, Jin X, Smolen J, Mariampillai A, Munce NR, Wilson BC, Vitkin IA, Yang VXD Interstitial Doppler optical coherence tomography as a local tumour necrosis predictor in photodynamic therapy of prostatic carcinoma: an in-vivo study 2008, 68, 23
  Lasers in Surgery and Medicine Douplik BA, Morofke D, Chiu S, Bouchelev V, Mao YI, Yang VXD, Vitkin IA In vivo real time monitoring of vasoconstriction and vasodilation by a combined diffuse reflectance spectroscopy and Doppler optical coherence tomography approach 2008, 40, 5
  European Heart Journal Courtney BK, Munce NR, Anderson KJ, Thind AS, Leung G, Radau PE, Foster FS, Vitkin IA, Schwartz RS, Dick AJ, Wright GA, Strauss BH Innovations in imaging for chronic total occlusions: A glimpse into the future of angiography’s blind spot 2008, 29, 5
  Journal of Applied Physics Mandelis A, Diebold GJ, Kitamori T, Hibara A, Vitkin IA Preface to Special Issue: Applied Biophysics 2009, 105, 10
  Journal of Biophotonics Ghosh N, Wood MFG, Li S, Weisel RD, Wilson BC, Li R-K, Vitkin IA Mueller matrix decomposition for polarized light assessment of complex turbid media such as biological tissues 2009, 2, 3
  Journal of Biomedical Optics Wood MFG, Ghosh N, Moriyama EH, Wilson BC, Vitkin IA Proof-of-principle demonstration of a Mueller matrix decomposition method for polarized light-based tissue characterization in vivo 2009, 14, 1
  Journal of Applied Physics Chin LCL, Lloyd B, Whelan WM, Vitkin IA Interstitial point radiance spectroscopy of turbid media 2009, 105, 10
  EMBO Molecular Medicine Sufan R, Moriyama EH, Mariampillai A, Roche O, Evans AJ, Lajez NM, Vitkin IA, Yang VXD, Liu FF, Wilson BC, Ohh M Oxygen-independent degradation of HIF-α via bioengineered VHL tumour suppressor complex 2009, 1, 1
  Journal of Applied Physics Ghosh N, Wood MFG, Vitkin IA Polarimetry in turbid, birefringent, optically active media: A Monte Carlo study of Mueller matrix decomposition in the backscattering geometry 2009, 105, 10
  Optics Letters Leung MKK, Mariampillai A, Standish BA, Lee KKC, Munce NR, Vitkin IA, Yang VXD High-power wavelength-swept laser in Littman telescope-less polygon filter and dual amplifier configuration for multichannel optical coherence tomography 2009, 34, 18
  Journal of Biophotonics Wilson BC, Vitkin IA, Matthews DL The potential of biophotonic techniques in stem cell tracking and monitoring of tissue regeneration applied to cardiac stem cell therapy 2009, 2, 11
  Journal of Biomedical Optics Munce NR, Wright GA, Mariampillai A, Standish BA, Leung MKK, Tan L, Lee KKC, Courtney BK, Teitelbaum AA, Strauss BH, Vitkin IA, Yang VXD Doppler optical coherence tomography for interventional cardiovascular guidance: in-vivo feasibility and forwardviewing probe flow phantom demonstration 2010, 15, 1
  Optics Communications Ghosh N, Wood MFG, Wallenberg MA, Vitkin IA Influence of the order of the constituent basis matrices on the Mueller matrix decomposition-derived polarization metrics in complex turbid media such as biological tissues 2010, 283, 6
  Physics in Medicine and Biology Standish BA, Lee KKC, Mariampillai A, Munce NR, Leung MKK, Yang VDX, Vitkin IA In-vivo endoscopic multi-beam optical coherence tomography 2010, 55, 3
  Applied Optics Guo X, Ghosh N, Wood MFG, Vitkin IA Depolarization of light in turbid media: A scattering event resolved Monte Carlo study 2010, 49, 2
  Optics Letters Mariampillai A, Leung MKK, Jarvi M, Standish BA, Lee KKC, Wilson BC, Vitkin IA, Yang YXD Optimized speckle variance OCT imaging of microvasculature 2010, 35, 8
  Optics Letters Wallenburg MA, Wood MFG, Vitkin IA Effect of optical axis orientation on polarimetry-based linear retardance measurements 2010, 35, 8
  Journal of Biomedical Optics Wood MFG, Ghosh N, Wallenburg MA, Li S, Weisel RD, Wilson BC, Li R-K, Vitkin IA Polarization birefringence measurements for characterizing the myocardium, including healthy, infracted, and stem cell regenerated tissues 2010, 15, 4
  Optics Letters Marika A. Wallenburg, Michael F. G. Wood, Nirmalya Ghosh, I. Alex Vitkin Polarimetry-based method to extract geometry-independent metrics of tissue anisotropy 2010, 35, 15
  Pramana-journal of Physics Nirmalya Ghosh, Jalpa Soni, M. F. G. Wood, M. A. Wallenberg, I. A. Vitkin Mueller matrix polarimetry for the characterization of complex random medium like biological tissues 2010, 75, 6
  Physics in Medicine and Biology Wood MFG, Vurgun N, Wallenburg MA, Vitkin IA Effect of formalin fixation on tissue optical polarization properties 2011, 56, 8
  Journal of Biophotonics Wallenburg MA, Li S, Li R-K, Vitkin IA Two photon microscopy of healthy, infracted, and regenerating myocardium (featured article on cover) 2011, 4, 5
  Biomedical Optics Express Ahmad M, Alali S, Kim AJ, Wood MFG, Vitkin IA Do different turbid media with matched bulk optical properties also exhibit similar polarization properties? 2011, 2, 12
  Laser Physics Letters Ullah H, Mariampillai A, Atif M, Vitkin IA Can temporal analysis of OCT statistics report on D-glucose levels in blood? 2011, 21, 11
  Journal of Biomedical Optics Ghosh N and Vitkin IA Concepts, challenges and applications of polarized light in biomedicine: a tutorial review 2011, 16, 11
  Laser Physics Ullah H, Davoudi B, Mariampillai A, Hussain G, Ikram M and Vitkin IA Quantification of glucose levels in flowing blood using Mmode swept-source optical coherence tomography 2012, 22, 4
  PLoS One Attique M, Ghulam Gilanie G, Ullah H, Malik S. Mehmood MS, Naweed MS, Ikram M, Javed A Kamran JA and Vitkin IA Colourization and automated segmentation of human T2 MR brain images for characterization of soft tissues 2012, 7, 3
  Optics Letters Conroy L, DaCosta R, Vitkin IA Quantifying tissue microvasculature with speckle variance optical coherence tomography 2012, 37, 15
  Journal of Biomedical Optics Alali S, Ahmad M, Kim AJ, Wood MFG, Vitkin IA Quantitative correlation between light depolarization and transport albedo of various porcine tissues 2012, 17, 4
  Biomedical Optics Express Davoudi B, Lindenmaier A, Standish BA, Bizheva K, Vitkin IA

Noninvasive in vivo structural and vascular imaging of human oral tissues with spectral domain optical coherence tomography

2012, 3, 5
  Journal of Biomedical Optics Alali S, Aitken K, Bagli D, Vitkin IA Optical assessment of tissue anisotropy in ex vivo distended rat bladders 2012, 17, 8
  Journal of Molecular and Cellular Cardiology Li SH, Sun Z, Guo L, Han M; Wood MFG, Ghosh N, Vitkin IA, Weisel RD, Li R-K

Elastin overexpression by cell-based gene therapy preserves matrix and prevents cardiac dilation

2012, 16, 10
  Optics Express Layden D, Wood MFG, Vitkin IA Optimum selection of input polarization states in determining the sample Mueller matrix: a dual photoelastic polarimeter approach 2012, 20, 18
  Journal of Biomedical Optics Ghosh N, Vitkin IA and Ossikovski R A comparative study of differential matrix and extended polar decomposition formalisms for polarimetric characterization of complex tissue-like turbid media 2012, 17, 10
  PLoS One Maeda A, Leung MKK, Conroy L, Chen E, Bu J, Lindsay P, Mintzberg S, Virtanen C, Tsao J, Winegarden NA, Wang Y, Morikawa L, Vitkin IA, Jaffray DA, Hill RP, DaCosta RS In vivo optical imaging of tumour and microvascular response to ionizing radiation 2012, 7, 8
  Biomedical Optics Express Grabchuk S, Palmer TJ, Vitkin IA and Whelan WM Radiance detection of non-scattering inclusions in turbid media 2012, 3, 11
  Optics Letters Das NK, Chatterjee S, Soni J, Jagdap J, Pradan A, Sengupta TK, Panigrahi PK, Vitkin IA and Ghosh N Probing multifractality in tissue refractive index: prospects for precancer detection 2013, 38, 2

Результаты исследований

1. Разработана оптическая часть системы поперечного сканирования для ММ ОКТ с увеличением диапазонов по координатам X, Y до 8 мм при приеме 20000 А-сканов в секунду. Разработаны, изготовлены и прошли экспериментальную апробацию в макетном исполнении контактный сканирующий объектив с телецентрическим ходом лучей на длине волны 1.3 мкм и его корпус. Исследована поляризационная анизотропия оптической системы с увеличенным диапазоном 3D сканирования при сканирующей системе на основе MEMS. Показана возможность эффективной компенсации поляризационной анизотропии сканирующей системы при помощи пластинки из кристалла MgF2 с Z- срезом.

Сверх плана выполнена - разработка пользовательской программы для одновременной визуализации микроциркуляторного русла и поляризационных изображений в процессе записи данных ОКТ

Для удобства использования мультимодальной ОКТ в клинике модифицированы способы фильтрации ОКТ сигнала, методы компенсации неоднородных искажений в исследуемой ткани и методы нормализации сигнала ОКТ перед применением ангиографической обработки, что позволило существенно снизить количество артефактов и вклад в итоговое ангиографическое изображение ярких сигналов от неподвижных участков изображения. В итоге на экране пользовательской программы в реальном времени записи данных ОКТ демонстрируется 9 изображений, позволяющие оперативно отслеживать артефакты на изображениях и своевременно дублировать необходимые изображения.

2. Апробировано несколько видов экспериментальных моделей для ММ ОКТ исследования. Установлено, что оптимальной моделью для изучения эффективности противоопухолевой терапии является карцинома СТ-26, локализованная на ухе мыши, что обусловлено простотой получения модели и высоким процентом качественных КП ОКТ и ОКТ МА изображений. Моделью для изучения реакции нормальных тканей на противоопухолевую терапию выбрана слизистая оболочка защечного мешка хомяка. Эта модель также оптимальна для ОКТ эластографии, поскольку является слоистой структурой.  Модели глиом мозга 101.8 и С6 могут быть исследованы методом ММ ОКТ для определения границ инфильтративно растущих глиальных опухолей головного мозга в ходе резекции опухоли, а также для оценки эффективности послеоперационной ФДТ.

3. Метод КП ОКТ отражает реакцию опухолевой паренхимы и стромы опухоли на ХТ Иринотеканом, а метод ОКТ МА – реакцию опухолевого микроокружения (микрососудов) на ХТ. Установлено, что опухолевая прогрессия характеризуется снижением ОКТ сигнала в ко- и кросс-каналах и развитием сосудистой сетки опухоли. Признаком опухолевого регресса на фоне ХТ является существенное усиление ОКТ сигнала в ко-и кросс-канале и исчезновение на ОКТ МА тонких и извилистых опухолевых сосудов. Показаны многообещающие возможности метода ОКТ МА с применением алгоритма выделения границ опухоли для обнаружения взаимосвязи реакции сосудистого русла опухолевого окружения с характером противоопухолевого ответа на ФДТ. Сформулированы критерии эффективности ФДТ: наличие выраженной сосудистой реакции на ОКТ МА изображениях в области опухоли и в опухолевом окружении в первые 24 часа после ФДТ, через 7 дней после ФДТ приводит к тотальному некрозу опухолей. Отсутствие реакции (или слабо выраженная реакция) сосудов в опухолевом окружении на ОКТ МА изображениях даже при наличии выраженной реакции сосудов в опухоли в первые 24 часа, после ФДТ свидетельствует о низкой эффективности ФДТ, поскольку к 7 дню после ФДТ в опухоли остается 60-80% жизнеспособных опухолевых клеток, что обеспечит продолжение роста опухолей. О гибели паренхимы опухоли свидетельствует повышение уровня кросс-рассеяния и возрастания значений ИФД. Предварительные исследования демонстрируют, что повышенный уровень фона между сосудами на ОКТ-ангиограммах в областях экстравазации может быть связан с присутствием межтканевой жидкости.

* В рамках проекта на 2017 год было запланировано проведение экспериментальным животным двух видов противоопухолевого лечения: фотодинамической и лучевой терапия. Лучевая терапия (ЛТ) была заменена на адекватную по механизму действия химиотерапию Иринотеканом или 5-фторурацилом – эти препараты обладают радиомиметическим действием (т.е. действием, подобным радиации). Замена лечения была связана с поломкой в Нижнем Новгороде аппарата лучевой терапии “Terabalt”, UJP, Czech Republic, источник 60Co. В аппарате заменялась плата, которую доставляли от производителя из Чехии, что заняло длительное время (несколько месяцев).

4. Методом ММ ОКТ проведен мониторинг развития мукозита слизистой оболочки защечного мешка хомяка на системную терапию 5-Фторурацилом. Мукозит проявляется в виде потери слоистости и снижение сигнала на 9 сутки после ХТ на КП ОКТ изображениях, и появлении извилистых мелких сосудов на ОКТ МА изображениях, отражающих развитие воспалительного процесса.

5. Разработан робастный и эффективный метод оценки деформируемости тканей, позволяющий оценить абсолютные величины жесткости (модуля Юнга) нормальной и опухолевой ткани экспериментальных животных в ходе противоопухолевой терапии. Показано, что контрастность изменений ткани в ответ на противоопухолевую терапию по жесткости значительно превышает изменения, видимые на структурных ОКТ изображениях. Установлено, что модуль упругости опухоли ~ в 5 и более раз выше, чем у окружающей нормальной ткани. На ранних сроках (через 1-2 дня) после сосудистого и клеточного видов ФДТ происходит снижение модуля упругости опухолевой ткани на несколько десятков процентов. Модуль упругости опухоли на поздних сроках после ФДТ зависел от эффекта терапии: в случае сосудистой ФДТ, которая приводила к полной гибели и некрозу опухоли, жесткость ткани повышалась вследствие формирования струпа на поверхности; в случае клеточной ФДТ жесткость ткани опухоли на поздних сроках изменялась незначительно, поскольку эффект терапии был слабым и большинство опухолевых клеток оставались жизнеспособными, при этом опухоль продолжала развиваться. При развитии мукозита слизистой оболочки защечного мешка хомяка после ХТ 5-Фторурацилом модуль упругости ткани повышался на несколько десятков процентов, отражая возникшее воспаление. Проведенные исследования убедительно показали, что модифицированный метод ОКТ эластографии с высокой чувствительность отражает индивидуальную реакцию опухоли на противоопухолевую терапию.

6. Проведен анализ двумерных проекций максимальной интенсивности сигнала трехмерных ОКТ ангиографических распределений путем бинаризации и дальнейшей скелетизации. Начата разработка методов квантификации сосудистых сеток в трехмерном пространстве, что позволило локализовать сосуды в трехмерном пространстве и анализировать их распределение по глубине. Разработаны новые подходы для количественной оценки васкуляризации на ОКТ МА изображениях, по которым могут быть рассчитаны такие параметры как общая длина всех сосудов, процентное соотношение сосудов разных диаметров, плотность и площадь сосудистой сетки. Вычисляемые параметры применены к обсчету сосудистых сеток, полученных в ходе различных экспериментов. Количественная оценка микроангиографических ОКТ изображений показала, что основное отличие злокачественной папилломы от доброкачественной состоит в увеличенном количестве 1-пиксельных сосудов (диаметр порядка 20 мкм), соответствующих новообразованным сосудам злокачественных опухолей; для описания сосудистой реакции слизистой оболочки полости рта при развитии лучевых мукозитов методом ОКТ МА информативным параметром является увеличение плотности сосудистой сетки и увеличение количества 1- пиксельных сосудов. Изменение этих показателей адекватно вписывается в теорию воспалительного патогенеза мукозита. Для характеристики реакции сосудов опухоли на химиотерапию информативным параметром является общая длина сосудов, которая уменьшается в виду инволюции опухоли.

7. За 2016 год опубликовано 7 статей в журналах, индексируемых в системе WoS (против 4 запланированных), 4 статьи в журналах, индексируемых Scopus и 1 статья в журнале, индексируемом РИНЦ (всего 12 статей).

8. В рамках выполнения Проекта разработан и прочитан спецкурс «Современные тенденции развития методов медицинской визуализации в онкологии» для студентов и аспирантов ФГБОУ ВО НижГМА Минздрава России в рамках Школы молодых ученых при НИИ БМТ. Презентации лекций – на сайте Лаборатории ОКТ НижГМА.

9. В 2016 году по направлению научного исследования была защищена диссертация на соискание ученой степени кандидата наук Карабут М.М. «Лазерный фототермолиз слизистой оболочки полости рта». Защита состоялась 22 декабря 2016 года на заседании Диссертационного совета № Д 501.001.65 при Московском государственном университете имени М.И. Ломоносова. Результаты защиты размещены на официальном сайте Биологического факультета МГУ им. М.И. Ломоносова по адресу http://www.bio.msu.ru/res/Dissertation/794/DISSERTATION_COUNCIL_CONCLUSION_FILENAME/Karabut_resultati.pdf.

10. С целью выполнения заявленных исследований в лабораторию «Оптической когерентной томографии» в 2016 году было приобретено следующее оборудование на общую сумму 17 261 294,2 руб.:

1. Титан-сапфировый фемтосекундный лазер с перестраиваемой длиной волны излучения, для микроскопа LSM 880 (Zeiss). Модернизация микроскопа данным лазером позволит проводить исследования со спектральной селекцией возбуждения автофлуоресценции. Такой подход даст более подробную информацию о морфофункциональном состоянии клеток и структуре коллагеновых волокон; 2. Адаптер для микроскопа Zeiss EXTRA 1 FLIM. Необходим для стыковки лазера с микроскопом и доставки лазерного излучения к объекту исследования; 3. Рабочая станция для блока сортировщика FACSAriaIII с предустановленным программным обеспечением. Необходим для управления сортировщиком FACSAriaIII, что необходимо для выполнения задач по сортингу культуры опухолевых клеток с целью отбора наиболее подходящих клонов; 4. Пикосекундный лазер BDL-488-SMN. Необходим возбуждения автофлуоресценции биологических тканей в узком диапазоне с целью изучения их функционального состояния. 5. Блокирующий фильтр O-FSP-680-22MM, волоконный манипулятор O-POS-FM и одномодовое волокно F100-SN-COLL-450-650 для работы пикосекундного лазера

Для выполнения запланированных исследований были приобретены следующие расходные материалы на общую сумму 1 157 808,74 руб.:

1. Химические реактивы для проведения гистологических исследований; 2. Культуральные среды и добавки для приготовления культур опухолевых клеток; 3. Культуральный пластик для наращивания культуры опухолевых клеток.

11-12. Члены творческого коллектива приняли участие в 8 международных и 8 российских конференциях. На базе лаборатории было проведен 17 семинаров, из них 9 с очным участием ведущего ученого Алекса Виткина.

В 2016 году происходил международный взаимообмен специалистами: стажировка н.с. лаборатории Оптической когерентной томографии НИИ БМТ Л.А. Матвеева в лаборатории ВУ Алекса Виткина в Торонто (University of Toronto, Canada – 21.07.16-13.08.16). Результаты визита были обсуждены на научном семинаре в лаборатории «Основные направления усовершенствования мультимодального оптического имиджинга на основе ОКТ».

13. В рамках выполнения научного исследования был заключен гражданско-правовой договор с Федеральным государственным бюджетным учреждением «Федеральный исследовательский центр Институт Прикладной Физики Российской академии наук» (ИПФ РАН) и выполнена научно-исследовательская работа на тему «Разработка новых технологий поперечного сканирования для ММ ОКТ с увеличенным полем обзора». Результаты представлены в п. 1.1 Отчета ВУ.

14. В рамках проекта подготовлена серия научно-образовательных лекций для сайта Открытого университета МГУ им. Ломоносова на тему «Оптическая когерентная томография: принцип и применение»: http://media.msu.ru/?p=9402; http://media.msu.ru/?p=9398; http://media.msu.ru/?p=11045.

1. Краткое описание полученных научных результатов за 2015 г.:

1.1. Создан скоростной вариант спектрального оптического когерентного томографа, оснащенного зондом с эффективной системой 3D сканирования и имеющего за счет ряда эффективных модификаций существенные преимущества в решении задач кросс-поляризационной ОКТ, ОКТ микроангиографии и ОКТ эластографии.

1.2. Разработан новый метод визуализации микрососудистой сети средствами ОКТ (ОКТ МА), сочетающий положительные особенности, присущие по отдельности известным ОКТ методам, использующим вариабельность интенсивности спеклов в сечениях сосудов на ОКТ сканах (SV-подход) и фазо-разрешающих (доплеровских) подходов. За счет этого создается возможность эффективной компенсации естественных движений живой ткани, выбора приемлемого компромисса между чувствительностью и скоростью ангиографического картирования, открываются возможности количественной градации сосудов по интенсивности движения рассеивателей в крови.

1.3. Разработан оригинальный вариант компрессионной ОКТ эластографии (ОКТ ЭГ), сочетающий использование фазовых измерений на масштабах меньших длины оптической волны и трекинг/компенсацию смещений на масштабах, превышающих не только длину волны, но и длину когерентности излучения ОКТ сканера. Особенности метода обеспечивают его беспрецендентно высокую устойчивость к шумам и позволяет достаточно уверенно осуществлять эластографическое картирование, используя всего одну пару сравниваемых ОКТ сканов. Это открывает возможности для проведения эластографического картирования при работе «с руки» и получения эластографических изображений в режиме реального времени даже без использования специальных средств параллелизации вычислений.

1.4. Проведены доклинические исследования идентификации ОКТ изображений, полученных на модельных животных, путем морфологических и патофизиологических сопоставлений. Проведено мониторирование индукции опухоли, ее роста и ответа на лечение с использованием ММ ОКТ и других методов биофотоники.

1.4.1. Изучен процесс естественного роста опухолевого узла у экспериментальных животных с помощью оптических методов. Установлено, что:

А) Оптимальной моделью экспериментальной опухоли для оценки естественного роста и эффективности противоопухолевого лечения является опухоль СТ26, прививаемая на ушной раковине мышей Balb/c.

Б) Основными закономерностями морфологических изменений экспериментальной опухоли в ходе естественного роста являются одновременное присутствие двух процессов: формирование опухоли как морфологического субстрата и развитие спонтанных регрессивных изменений в ней. Установлены сроки пика митотической активности опухолей, которые определяют эффективные сроки начала противоопухолевой терапии.

В) Установлена характерная динамика изменений КП ОКТ изображений в ходе естественного роста опухоли.

Г) Оценка динамики микроциркуляции экспериментальной опухоли в ходе естественного роста, полученная с помощью ОКТ МА, показала ее совпадение с гистологическими данными.

1.4.2. Изучен процесс ответа опухолевого узла на проводимую фотодинамическую терапию (ФДТ) у экспериментальных животных с помощью оптических методов.

А) Основными закономерностями морфологических изменений экспериментальной опухоли в ходе фотодинамической терапии (лечебный патоморфоз) являются два процесса: 1) выраженная сосудистая реакция: полнокровие, стаз, единичные эритроцитарные тромбы; 2) необратимые изменения ядра и цитоплазмы опухолевых клеток вплоть до образования очагов некроза. У животных наблюдалась различная степень патоморфоза по шкале Mandard – от слабой (4 степень) до выраженной (1-2 степень), которая зависела как от степени васкуляризации опухоли, так и от степени накопления фотосенсибилизатора в сосудах опухоли.

Б) Показаны многообещающие возможности метода ОКТ МА в визуализации сосудов как нормальной, так и опухолевой ткани. Выявлена различная степень проявления реакции сосудистой сети в ответ на ФДТ – от полного исчезновения сосудов на ОКТ МА-изображениях до отсутствия видимой реакции, коррелирующие со степенью лечебного патоморфоза. МА ОКТ позволяет предсказывать эффект терапии, а значит корректировать и индивидуализировать противоопухолевое лечения.

1.5. Показаны многообещающие возможности метода ОКТ МА в визуализации сосудов как нормальной, так и опухолевой ткани. Выявлена различная степень проявления реакции сосудистой сети в ответ на фотодинамическую терапию (ФДТ) – от полного исчезновения сосудов на ОКТ МА-изображениях до отсутствия видимой реакции, коррелирующие со степенью лечебного патоморфоза. МА ОКТ позволяет предсказывать эффект терапии, а значит корректировать и индивидуализировать курс лечения.

1.6. Разработан ряд методов автоматической интерпретации КП ОКТ изображений и ОКТ микроангиограмм и их количественной оценки, которые могут быть использованы для дифференциальной диагностики состояний тканей и создания критериев эффективности противоопухолевого лечения для его индивидуализации, а именно:

А) На основе таких количественных характеристик КП ОКТ изображений как: объём и расположение опухоли; глубина визуализации; мощность ОКТ-сигнала в исходной поляризации, усредненная по глубине визуализации; мощность ОКТ-сигнала в ортогональной поляризации, усредненная по глубине визуализации; коэффициенты экстинкции на глубине визуализации, вычисляемые для А-сканов в исходной и ортогональной поляризации; фактор деполяризации, а также характер границы нормальной и патологической ткани, разработаны следующие алгоритмы обработки КП ОКТ изображений:

− алгоритм (способ) оценки функционального состояния коллагенсодержащей ткани на основе численной обработки ОКТ-сигналов изображений в ортогональной и исходной поляризациях;

− алгоритм сегментации (выделения) патологических зон, построенный на основе методов машинного обучения с учителем с использованием в качестве обучающих данных серии КП ОКТ-изображений, размеченных группой экспертов по результатам гистологических исследований;

− алгоритм выделения патологических зон, проецирующихся на фронтальную поверхность тела и построенных путем преобразования трехмерных КП ОКТ-изображений, включающих вычисляемые количественные параметры (перечисленные в пункте 2.1.5.1) таким образом, что каждый количественный параметр независимо вычисляется для каждого А-скана; 

Б) На основе характеристик ОКТ изображений микроциркуляторного русла, полученных новым методом визуализации сосудов, разработан следующий алгоритм:

− алгоритм сегментации ОКТ микроангиограмм, который позволяет дифференцировать и раздельно визуализировать сосуды патологически измененной ткани (опухоли, области воспаления) и здоровой ткани. Характеристики данных сосудистых сеток используются в качестве критериев эффективности для индивидуализации лечения.

1.7. Проведены пилотные клинические исследования с целью выявления OКT-критериев эффективности противоопухолевой терапии по ответу на лечение и определения показаний к разным видам терапии.

А) Визуальная оценка КП ОКТ изображений опухоли не выявляет видимых изменений в ответ на лучевую терапию опухолей рта и глотки, однако обнаруживает реакцию нормальной слизистой, попавшей в зону облучения;

Б) Динамика КП ОКТ изображений здоровой слизистой оболочки полости рта, попавшей в зону облучения, у пациентов в процессе лучевой терапии новообразований полости рта и глотки коррелирует с тяжестью развивающегося радиационного мукозита. Разработаны оптические способы превентивной диагностики тяжелых мукозитов на основе КП ОКТ изображений.

В) КП ОКТ способна детектировать ключевые морфологические изменения в ходе фотодинамической терапии опухолей кожи и слизистой шейки матки (отек, некроз с последующим восстановлением структуры ткани в поздние сроки).

Г) ОКТ микроангиограммы отражают различную степень проявления реакции сосудистой сети в ответ на фотодинамическую терапию опухолей кожи – от полного исчезновения сосудов на ОКТ МА-изображениях до отсутствия видимой реакции, коррелирующие со степенью лечебного патоморфоза.

Д) Параметры изображений мультимодальной ОКТ, включающие 3D КП ОКТ изображения и 3D сосудистые сетки ОКТ микроангиографии, могут быть использованы для создания критериев ответа опухолевой ткани на фотодинамическую терапию и применены для оценки эффективности терапии и индивидуализации лечения рака.

2. Опубликовано 4 статьи в научной периодике, индексируемой в Web of Science и 8 статей в научной периодике, индексируемой в Scopus.

3. Подготовлен и выпущен спецвыпуск журнала «Современные технологии в медицине», посвященный оптической когерентной томографии: “Optical coherence tomography: novel methodologies and emerging biomedical applications”.

Научные редакторы выпуска – проф. Алекс Виткин; проф. Наталья Гладкова

  1. За 2014 год опубликовано 5 работ в журналах, индексируемых в системе WoS и 2 статьи, индексируемые Scopus.

  2.  В научной лаборатории «Оптической когерентной томографии» в 2014 году приобретено и введено в эксплуатацию лабораторное оборудование. Лаборатория эффективно функционирует.

  3.  Члены творческого коллектива лаборатории приняли участие в 10 международных и 6 российских конференциях. На базе лаборатории был проведен 21 семинар, из них 12 с очным участием ведущего ученого Алекса Виткина.

  4. В 2014 году происходил международный взаимообмен специалистами: 1) стажировка м.н.с. НИИ БМТ И.Н. Дружковой в лаборатории ВУ Алекса Виткина в Торонто, (Princess Margaret Hospital, University Health Network, Toronto, Canada – 18.01.14-01.02.14); 2) Визит научного сотрудника лаборатории ВУ Алекса Виткина Valentin Demidov (Research Assistant of Biomedical Optics Laboratory of Professor A. Vitkin, University of Toronto) в НИИ БМТ – был проведен Международный семинар на тему «Подходы к количественной обработке ОКТ изображений».

  5. В рамках проекта на базе научной лаборатории были проведены курсы тематического усовершенствования врачей и специалистов «Оптическая когерентная томография» (объем аудиторной нагрузки 72 часа) по направлению научного исследования. Лекции были прочитаны участниками проекта. По окончании курса сертификаты и удостоверения о прохождении профессиональной переподготовки получили 9 врачей и 1 специалист-исследователь из сторонних организаций.

  6.  В рамках проекта в 2014 году разработан и проведен спецкурс «Оптическая когерентная томография в ряду методов оптических методов визуализации» для студентов НижГМА в рамках элективных занятий на кафедре медицинской физики и информатики.

  7.  Подготовлена английская версия сайта лаборатории.

  8. Сверх плана: Подготовлен международный спецвыпуск по ОКТ журнала «Современные технологии в медицине», выпускаемого НижГМА: №1, за 2015 год, который включает 14 статей авторов из 6 стран мира (Россия, Великобритания, Австрия, США, Канада, Новая Зеландия).

  1. по результатам исследования опубликованы/приняты к печати 3 статьи;
  2. подана заявка на патент по результатам исследования;
  3. создана научная лаборатория «Оптическая когерентная томография», закончен ремонт вновь выделенных помещений лаборатории проводится закупка оборудования, материалов и комплектующих для проведения исследований;
  4. подготовлены и проведены 9 семинаров; члены творческого коллектива приняли участие в 11 конференциях по тематике исследований; в лаборатории подготовлены и проведены курсы повышения квалификации по ОКТ.
  5. Определены три новых направления международного сотрудничества:
  • организован международный Комитет «Scientific Advisory Board» для рецензии, контроля и критической оценки проводимых исследований;
  • обсуждена возможность научных межлабораторных исследований и поездок в зарубежные лаборатории с целью ускорения достижения научных результатов;
  • положено начало обсуждениям технологических возможностей и совместных направлений дальнейшего развития и совершенствования разрабатываемой в рамках проекта высокоэффективной технологии МФ ОКТ с NIH-funded Center forBiomedical OCT Research (an NIH-funded Biotechnology Resource Centre at the Massachusetts General Hospital,Boston,  MA,USA, directed by Professor Brent Bouma, PhD).

There was shown a possibility of realization of the method of optical coherent tomography with the scheme of parallel acceptance of the interference signal (P-OCT) based on spatial paralleling of the phase diffraction of reference wave grating for creation of temporal delay in Mach–Zehnder interferometer.

1. Publication: Morozov A.N., Turchin I.V. Method of Optical Coherent Tomography with Parallel Acceptance of the Signal from Depth and Optical Phase Modulators. Radiophys. and Quantum electronics, 2013 43(12), 1165-1169.

Морозов А.Н., Турчин И.В. Метод оптической когерентной томографии с параллельным приемом сигнала с глубины и волоконно-оптическими модуляторами фазы. Квантовая электроника, 2013.

The method of optical coherence tomography with the scheme of parallel reception of the interference signal (P-OCT) is developed on the basis of spatial paralleling of the reference wave by means of a phase diffraction grating producing the appropriate time delay in the Mach – Zehnder interferometer. The absence of mechanical variation of the optical path difference in the interferometer essentially reduces the time required for 2D imaging of the object internal structure, as compared to the classical OCT that uses the time-domain method of the image construction, the sensitivity and the dynamic range being comparable in both approaches. For the resulting field of the interfering object and reference waves an analytical expression is derived that allows the calculation of the autocorrelation function in the plane of photodetectors. For the first time a method of linear phase modulation by 2p is proposed for P-OCT systems, which allows the use of compact high-frequency (a few hundred kHz) piezoelectric cell-based modulators. For the demonstration of the P-OCT method an experimental setup was created, using which the images of the inner structure of biological objects at the depth up to 1 mm with the axial spatial resolution of 12 mm were obtained.

 
Figure. Scheme of the experimental P-OCT setup on the basis of the Mach – Zehnder interferometer: (1) superluminescent diode; ( 2 ) fibre-optic power splitter; ( 3 ) piezoelectric phase modulators; ( 4 ) saw-tooth voltage generator; ( 5 ) diffraction grating; ( 6 ) aspherical lenses; ( 7 ) semitransparent beam splitter; ( 8 ) object; ( 9 ) diffraction slit; ( 10 ) photodetector; ( 11 ) and ( 12 ) systems of in-depth scanning (with linear displacement of the photodetector) and lateral scanning (with linear displacement of the object).

A new approach to elastographic mapping in optical coherence tomography has been developed based on comparison of correlation stability in different regions of consequently acquired structural OCT images of the studied deformed tissue. 

2. Publication: Vladimir Y. Zaitsev, Lev A. Matveev, Alexandr L. Matveyev, Grigory V. Gelikonov, and Valentin M. Gelikonov.Elastographic mapping in optical coherence tomography using an unconventional approach based on correlation stability. Journal of Biomedical Optics, 19(2), 021107(1-12) (2014).

An approach to elastographic mapping in optical coherence tomography (OCT) using comparison of correlation stability of sequentially obtained intensity OCT images of the studied strained tissue is discussed. The basic idea is that for stiffer regions, the OCT image is distorted to a smaller degree. Consequently, cross-correlation maps obtained with compensation of trivial translational motion of the image parts using a sliding correlation window can represent the spatial distribution of the relative tissue stiffness. An important advantage of the proposed approach is that it allows one to avoid the stage of local-strain reconstruction via error-sensitive numerical differentiation of experimentally determined displacements. Another advantage is that the correlation stability (CS) approach intrinsically implies that for deformed softer tissue regions, cross-correlation should already be strongly decreased in contrast to the approaches based on initial reconstruction of displacements. This feature determines a much wider strain range of operability than the proposed approach and is favorable for its free-hand implementation using the OCT probe itself to deform the tissue. The CS approach can be implemented using either the image elements reflecting morphological structure of the tissue or performing the speckle-level cross-correlation. Examples of numerical simulations and experimental demonstrations using both phantom samples and in vivo obtained OCT images are presented.

 

 
Figure. An example of elastographic CS mapping performed at the speckle level for a two-layer silicone phantom. (a) Initial OCT image exhibiting peculiar speckle structure. The boundary between the upper softer and lower stiffer layers is visible due to somewhat different scattering properties of the subresolved scatterers. (b) The resulting elastographic CS image obtained by averaging over 10 consequent B-scans of the same parity for the forthand-back motion of the scanning beam (five images before and five ones after the reference B-scan). Panels (c) through (f) show individual CS maps obtained via cross-correlation of a reference image with several consequent ones obtained for monotonically increasing strain. The stiffer layer demonstrates clearly slower decrease in the cross-correlation coefficient.

Feasibility of creating a multimodal OCT scanner has been analyzed and the corresponding approaches have been discussed. Such a scanner should allows for performing several complementary functionally different types of visualization – polarization-sensitive imaging, microvascular imaging and elastographic mapping without the necessity of an extra source for excitation of vibrations or shear/surface waves.

3. Publication: V.Y. Zaitsev, V. M. Gelikonov, L. A. Matveev, G. V. Gelikonov, A. L. Matveyev, P.A. Shilyagin, and I. A. Vitkin. Recent trends in multimodal optical coherence tomography. I. Polarization-sensitive oct and conventional approaches to OCT elastography. Radiophys. and Quantum Electron., V.57 (1), 52-66 (2014)  

В.Ю. Зайцев, В.М. Геликонов, Л.А. Матвеев, Г.В. Геликонов, А.Л. Матвеев, И.А. Виткин. Современные тенденции в многофункциональной оптической когерентной томографии. 1. Поляризационно-чувствительная окт и традиционные подходы к окт-эластографии. Изв. вузов. Радиофизика. 2014, Т. 57, № 1, С.59-74.

We discuss physical principles of obtaining polarization-sensitive images, elastographic mapping and visualization of blood circulation/vasculature in optical coherence tomography (OCT). Along with the general overview of the respective methods, we perform comparative critical analysis of some of them from the viewpoint of their feasibility and requirements to OCT systems destined for combining the above-mentioned different image modalities.

ris33
Figure. OCT-images of a sclera of the human eye. I- traditional image (co-channel), II –image in orthogonal polarization (cross-channel) (left).Right - (a) Schematically shown subresolution dispensers within the range of one volume of resolution and giving scattered waves , the interference of which lead to the appearance of specific speckle structure of OCT images and blinking of speckles in the process of deformation of medium (b) The scheme of creating the deformation in biotissue via pressing the solid surface of the probe.

4. Publication: V. Y. Zaitsev, I. A. Vitkin, L. A. Matveev, V. M. Gelikonov, A. L. Matveyev, and G. V. Gelikonov. Recent trends in multimodal optical coherence tomography. II. The correlation-stability approach in OCT elastography and methods for visualization of microcirculation. Radiophys. and Quant. Electron., V.57 (3), 210-225 (2014).  

В.Ю. Зайцев, И.А. Виткин, Л.А. Матвеев, В.М. Геликонов, А.Л. Матвеев, Г.В. Геликонов. Современные тенденции в многофункциональной оптической когерентной томографии - современные тенденции. 2: Использование корреляционной стабильности в ОКТ эластографии и методы визуализации кровотока. Изв. вузов. Радиофизика. 2014, Т. 57, № 3, С. 231 - 250.

The second part of this paper continues the discussion of possibilities for combining functionally different types of biomedical characterization of tissues using optical coherence tomography (OCT). In the first part, polarization-sensitive imaging and conventional approaches to elastographic mapping in OCT were considered. Here, we consider an unconventional approach to elastographic mapping based on the analysis of variability of OCT images of the deformed tissue, omitting the stage of the displacement-field reconstruction. We also discuss methods for quantification of blood flow and visualization of microvasculature, some of which have much in common with the elastographic approach based on the analysis of temporal variability of OCT frames. This similarity looks especially promising in the context of combining multiple contrast mechanisms to enable prospective multimodal OCT scanners, as is essential for biomedical progress given the complex and heterogeneous nature of real biological tissues.

 
Figure. Elucidation of interframe pixel analysis of structural OCT images to segment out blood (fluid) pixels based on their lower viscosity and thus faster temporal decorrelation (developed by the Canadian participants of the project in the group of A. Vitkin at the University of Toronto).

A convenient for detailed numerical simulations model has been developed to describe formation and evolution of speckle structure of OCT images

5. Publication: V.Y. Zaitsev, L.A. Matveev, A.L. Matveyev, G.V Gelikonov, and V.M. Gelikonov. A model for simulating speckle-pattern evolution based on close to reality procedures used in spectral-domain OCT. Laser Physics Letters, 11, 105601(1-8) (2014).

A robust model for simulating speckle-pattern evolution in optical coherence tomography (OCT) depending on the OCT system parameters and tissue deformation is reported. The model is based on the application of close to reality procedures used in spectral-domain OCT scanners. It naturally generates images reproducing properties of real images in spectral domain OCT, including the pixelized structure and finite depth of unambiguous imaging, influence of the optical spectrum shape, dependence on the optical wave frequency and coherence length, influence of the tissue straining, etc. Good agreement with generally accepted speckle features and properties of real OCT images is demonstrated.  

 
Figure. Fragments (10 Ч 10 pixels) of simulated speckle patterns for N = 256 pixels in an A-scan for randomly distributed Nsc scatterers in each A-scan with the density Nsc/N = 0.5, 1, 2 and 4 (plots (a)–(d), respectively). To exclude the trivial increase of brightness with increasing density of scatterers, the amplitudes of the images are normalized (divided) by (Nsc/N)1/2.

Earlier proposed in our group correlation-stability approach to elastographic mapping has been further advanced in order to complement qualitative visualization of stiffness differences with their quantitative characterization

6. Publication: L. A. Matveev, V. Y. Zaitsev, A. L. Matveyev, G. V Gelikonov, and V. M. Gelikonov. "Combining the correlation-stability approach to OCT elastography with the speckle-variance evaluation for quantifying the stiffness differences". Biophotonics: Photonic Solutions for Better Health Care IV, Edited by Jurgen Popp, Valery V. Tuchin, Dennis L. Matthews, Francesco S. Pavone, Proc. of SPIE Vol. 9129, (2014), Vol. 9129, pp. 91290I (1-7).

We discuss an advanced variant of the correlation-stability (CS) approach to OCT elastography that is capable of quantifying the stiffness differences. The modified variant is based on natural combination of CS approach with the speckle-variance (SV) approach. It allows one to determine the strain dependence of the normalized speckle intensity variance function for two compared subsets taken from the OCT images corresponding to the initial and deformed states of the tissue. In previous studies we considered the basic dependence of the normalized speckle intensity variance function on the tissue strain under the assumption that the influence of translational displacements can be excluded, so that the residual speckle-intensity variations should be produced only by speckle blinking determined by local strains. In the present report we discuss the corresponding algorithms allowing one to exclude the above-mentioned influence of translational displacements. We demonstrate numerically the efficiency of such processing that allows for quantification of stiffness differences in the elastographic mapping based on the CS approach.

 
Figure. Speckle-variance map in a 0.5 strained three-layer tissue map simulated using the developed model of speckle-pattern formation/evolution and the depth-dependence of the normalized speckle variance along one of A-scans. The middle layer with reduced speckle variance is 4 times stiffer than the surrounding tissue. Square root of the ratio of the corresponding speckle variances in the softer and stiffer regions well agree with the inverse ratio of the stiffness parameters of the layers.

Comparative discussion and analysis of several recently proposed unconventional elastographic OCT methods has been performed. Further prospects of their development have been pointed out. 

7.  Publication: L.A. Matveev, V.Y. Zaitsev, A.L. Matveev, G.V. Gelikonov, V.M. Gelikonov, I.A. Vitkin. Recently proposed unconventional methods for elasticity characterization using Optical Coherence Tomography: a brief review and further prospects. Photonics and Lasers in Medicine. V. 3(4), 295–309 (2014)

In this paper, a brief overview of several recently proposed approaches to elastographic characterization of biological tissues using optical coherence tomography is presented. A common feature of these “unconventional” on a two-step process of first reconstructing the particle displacements and then performing its error-prone differentiation in order to determine the local strains. Further, several variants of these new approaches were proposed and demonstrated essentially independently and are based on significantly different principles. Despite the seeming differences, these techniques open up interesting prospects not only for independent usage, but also for combined implementation to provide a multifunctional investigation of elasticity of biological tissues and their rheological properties in a wider sense.

 
Figure. An example of qualitative visualization of sub-skin tissue stiffness for a BulbC mouse obtained via the correlation stability approach using natural motions of the living tissue (due to the animal breathing) as a source for tissue deformation. The measurements were made in contact mode (the motionless glass surface of the OCT probe was in contact with the tissue).

Achromatic registration of quadrature components of the optical spectrum in spectral domain optical coherence tomography

8.  Publication: P.A. Shilyagin, G.V. Gelikonov, V.M. Gelikonov, A.A. Moiseev, D.A. Terpelov Achromatic registration of quadrature components of the optical spectrum in spectral domain optical coherence tomography. Quantum Electronics. 2014. 44 (7) 664 –669.

We have thoroughly investigated the method of simultaneousreception of spectral components with the achromatisedquadrature phase shift between two portions of a reference wave,designed for the effective suppression of the ‘mirror’ artefact in theresulting image obtained by means of spectral domain opticalcoherence tomography (SD OCT). We have developed and experimentallytested a phase-shifting element consisting of a beamdivider, which splits the reference optical beam into the two beams,and of delay lines being individual for each beam, which create amutual phase difference of p/2 in the double pass of the referencebeam. The phase shift achromatism over a wide spectral range isachieved by using in the delay lines the individual elements with differentdispersion characteristics. The ranges of admissible adjustmentparameters of the achromatised delay line are estimated forexact and inexact conformity of the geometric characteristics of itscomponents to those calculated. A possibility of simultaneousrecording of the close-to-quadrature spectral components with asingle linear photodetector element is experimentally confirmed.The suppression of the artefact mirror peak in the OCT-signal byan additional 9 dB relative to the level of its suppression is experimentallyachieved when the air delay line is used. Two-dimensionalimages of the surface positioned at an angle to the axis of the probebeam are obtained with the correction of the ‘mirror’ artefact whilemaintaining the dynamic range of the image.

 
Figure. Images of the scattering surface positioned at an angle to the probe beam axis, by using (top) an inclined reflector and (bottom) the phaseshifting element

An analogy between spectral-domain optical coherence tomography (SD OCT) data and broadband digital holography data is considered. Based on this analogy, a method for processing SD OCT data, which makes it possible to construct images with a lateral resolution in the whole investigated volume equal to the resolution in the in-focus region, is developed. Several issues concerning practical application of the proposed method are discussed.

9.  Publication: Moiseev, A. A., Gelikonov, G. V., Terpelov, D. A., Shilyagin, P. A., & Gelikonov, V. M. (2014). Improvement of lateral resolution of spectral domain optical coherence tomography images in out-of-focus regions with holographic data processing techniques. Quantum Electronics, 44(8), 732-739.

Based on the analogy between the SD OCT and broadband digital holography data, we described a method for processing SD OCT data, which provides images with a lateral resolution throughout the entire volume under study corresponding to the resolution in the in-focus region. A technique for determining the parameters (dependent on the medium studied) that are necessary for efficient application of the proposed methods was developed. The problem of phase stability between lateral measurements in SD OCT was considered and a way of compensating for possible phase instability was proposed.

 
Figure. Image of an array of point scatterers in a homogeneous medium, obtained by scanning a sample with a tightly focused beam using (a) conventional data processing, (b) processing data according to formula (6) with optimal values of algorithm parameters, (c) processing data (6) with values of algorithm parameters differing from optimal by 10%, and (d–f) after numerical transfer of the focal region. The images in panels (d) and (f) were obtained for refractive indices differing by ±20% from the value specified for the image in panel (e).

Speckle statistics of experimental and simulated OCT images of media with arbitrary optical properties was analyzed. It was shown that Gamma distribution function gives a good analytical fit to image histograms.

10. Publication: M.Yu. Kirillin, G. Farhat, E.A. Sergeeva, M.C. Kolios, and A. Vitkin “Speckle statistics in OCT images: Monte Carlo simulations and experimental studies”, Optics Letters, 39(12), 3472-3475 (2014)

The speckle pattern of an optical coherence tomography (OCT) image carries potentially useful sample information that may assist in tissue characterization.  Recent biomedical results in vivo indicate that the distribution of signal intensities within an OCT tissue image is well described by a log-normal-like (Gamma) function:

To fully understand and exploit this finding, an OCT Monte Carlo model that accounts for speckle effects was developed. The resultant Monte Carlo speckle statistics predictions agree well with experimental OCT results from a series of control phantoms with variable scattering properties; the Gamma distribution provides a good fit to both the theoretical and experimental results. The ability to quantify sub-resolution tissue features via OCT speckle analysis may prove useful in diagnostic photomedicine. 

 fig11
Figure. (a) Representative histograms (markers) and Gamma distribution fits (lines) for Sample 1. (b) Gamma distribution parameters extracted from experimental and simulated signal intensity histograms.  Shape α (left) and scale β (right) parameters are plotted as a function of particle concentration for both sized microspheres.

Effects of gamma irradiation on collagen damage and remodeling

11. Publication: Maslennikova A., Kochueva M., Ignatieva N., Vitkin A., Zakharkina O., Kamensky V., Sergeeva E., Kiseleva E., Bagratashvili V. Effects of gamma irradiation on collagen damage and remodeling. International Journal of Radiation Biology, 91(3), 240-247 (2015)

Purpose: To evaluate the dose-time dependences of structural changes occurring in collagen within 24 hours to three months after gamma-irradiation at doses from 2–40 Gy in vivo.

Materials and methods: Rat’s tail tendon was chosen as in vivo model, with its highly ordered collagen structure allowing the changes to be interpreted unambiguously. Macromolecular level (I) was investigated by differential scanning calorimetry (DSC); fibers and bundles level (II) by laser scanning microscopy (LSM), and bulk tissue microstructural level (III) by cross-polarization optical coherence tomography (CP-OCT).

Results: For (I), the formation of molecular cross-links and breaks appeared to be a principal mechanism of collagen remodeling, with the cross-links number dependent on radiation dose. Changes on level (II) involved primary, secondary and tertiary bundles splitting in a day and a week after irradiation. Bulk collagen microstructure (III) demonstrated early widening of the interference fringes on CP-OCT images observed to occur in the tendon as result of this splitting. At all three levels, the observed collagen changes demonstrated complete remodeling within a month following irradiation.

Conclusion: The time course and dose dependencies of the observed collagen changes at different levels of its hierarchy further contribute to elucidating the role of connective tissue in the radiotherapy process.

 
Figure. Cross-polarization optical coherence tomography (CP OCT) images of tendon samples for various irradiation doses and times following treatment. Uniform stripes demonstrate the absence of significant changes in general tendon microstructure, but detailed quantitative analysis did in fact reveal subtle changes (see Table II). Scale bar = 1 mm on all panels.

 

 
Figure. SHG images of rat tail tendon control sample (a) and samples irradiated at a dose of 20 Gy after 24 h (b), 30 Gy after 24 h (c), 20 Gy one week (d–f), one (g), two (h) and three (k) months. (a) Fascicle (secondary bundle); arrowhead indicates collagen fiber; asterisk is in a primary bundle; arrow indicates sharp crimp; smooth crimped area is shown in the circle; (b) The increasing of a bundle cleavage in crimped (arrow) and smooth folding (arrowheads) areas; (c) A displacement of split half-planes in smooth folding region (arrowhead); (d) A displacement of split half-planes (arrowheads) and a bundle cleavage in crimped area (arrows); (e, f ) Closely packed primary bundles (arrows) in a crimped area (e) and in a smooth folding region (f ); (g, h, k) Thin collagen fibers (arrows) overgrown in splits between primary bundles. Depth of confocal plane for each image is 100 mm, slice thickness ∼ 5 µm.

Hybrid M-mode-like OCT imaging of three-dimensional microvasculature in vivo using reference-free processing of complex valued B-scans

12. Publication: Matveev L., Zaitsev V., Gelikonov G., Matveyev A., Moiseev A., Ksenofontov S., Gelikonov V., Sirotkina M., Gladkova N., Demidov V., Vitkin A. Hybrid M-mode-like OCT imaging of three-dimensional microvasculature in vivo using reference-free processing of complex valued B-scans. Optics letters, 40 (7), 1472-1475 (2015)

We propose a novel OCT-based method for visualizing microvasculature in three-dimension using reference-free processing of individual complex valued B-scans with highly overlapped A-scans. In the lateral direction of such a B-scan, the amplitude and phase of speckles corresponding to vessel regions exhibit faster variability and, thus, can be detected without comparison with other B-scans recorded in the same plane. This method combines elements of several existing OCT angiographic approaches and exhibits: (1) enhanced robustness with respect to bulk tissue motion with frequencies up to tens of Hz, (2) resolution of microcirculation images equal to that of structural images, and (3) possibility of quantifying the vessels in terms of their decorrelation rates.

 

 
Figure. Principle of operation of the MMLSV approach: (a), a stack of dense B-scans with strongly overlapped A-scans; (b) a single B-scan before and after equalization of average phases of neighboring A-scans; (c) a spatial spectrum of a single horizontal array of pixels in a dense B-scan, where low-frequency components correspond to slowly varying motionless scatterers; (d) an experimental B-scan fragment with an encircled region of rapidly varying speckles corresponding to a vessel cross section (top) and a schematic B-scan with speckles slowly and rapidly varying in the horizontal direction (bottom); (e) the same as (d), but after high-pass filtering (only vessel cross sections are now visible); (f) a photo of a mouse dorsal window chamber and an example of en face depthencoded view of a 2 mm × 2 mm (lateral) 0–0.6 mm (depth) region of the detected mouse microvasculature

Differential diagnosis of human bladder mucosa pathologies in vivo with cross-polarization optical coherence tomography

13. Publication: Kiseleva E., Kirillin M., Feldchtein F., Vitkin A., Sergeeva E., Zagaynova E., Streltzova O., Shakhov B., Gubarkova E., Gladkova N. Differential diagnosis of human bladder mucosa pathologies in vivo with cross-polarization optical coherence tomography. Biomedical Optics Express, 6(4), 1464-1476 (2015)

Quantitative image analysis and parameter extraction using a specific implementation of polarization-sensitive optical coherence tomography (OCT) provides differential diagnosis of mucosal pathologies in in-vivo human bladders. We introduce a cross-polarization (CP) OCT image metric called Integral Depolarization Factor (IDF) to enable automatic diagnosis of bladder conditions (assessment the functional state of collagen fibers). IDF-based diagnostic accuracy of identification of the severe fibrosis of normal bladder mucosa is 79%; recurrence of carcinoma on the post-operative scar is 97%; and differentiation between neoplasia and acute inflammation is 75%. The promising potential of CP OCT combined with image analysis in human urology is thus demonstrated in vivo.

 

 
Figure. The results of IDF calculation in the cohort groups clustered for different clinical tasks: a – identification of fibrosis: Group 1 – normal, Group 2 – severe fibrosis at chronic cystitis, Group 3 – post-operation scar; b – identification and separation of different types of neoplasia: Group 1 – normal, Group 4 – acute inflammation, Group 5 – carcinoma in situ, Group 6 – invasive urothelial carcinoma with the beginning invasive growth; c – recognition of carcinoma recurrence on the scar: Group 3 – post-operation scar, Group 7 – recurrence of carcinoma on the post-operation scar.

 

 
Figure. IDF values for all studied states of CF in bladder mucosa (normalized by their normal state results). See discussion in the text.

Scan-pattern and signal processing for microvasculature visualization with complex SD-OCT: tissue-motion artifacts robustness and decorrelation time – blood vessel characteristics

14. Publication: Matveev L., Zaitsev V., Gelikonov G., Matveyev A., Moiseev A., Ksenofontov S., Gelikonov V., Demidov V., Vitkin A. Scan-pattern and signal processing for microvasculature visualization with complex SD-OCT: tissue-motion artifacts robustness and decorrelation time – blood vessel characteristics. Procceedings of SPIE, 9448, 94481M-1-6 (2015).

We propose a modification of OCT scanning pattern and corresponding signal processing for 3D visualizing blood microcirculation from complex-signal B-scans. We describe the scanning pattern modifications that increase the methods’ robustness to bulk tissue motion artifacts, with speed up to several cm/s. Based on these modifications, OCT-based angiography becomes more realistic under practical measurement conditions. For these scan pattern, we apply novel signal processing to separate the blood vessels with different decorrelation times, by varying of effective temporal diversity of processed signals.

 

 
Figure. Panel (a) demonstrates the fragment of the B-scan with vessel. The speckles on the vessel are spatially distorted in compare to surroundings tissue. This distortion related to transformation of the speckle temporal blinking to its spatial distortion due to M-Mode like acquisition (slow scanning beam speed Vbeam=0.6 mm/s). After applying the high pass filtering to suchwise formed 3D data set only distorted speckles are remained. The resulting B-scan after filtering is demonstrated on panel (b) for the high pass square filter threshold equals to 40 Hz. It means that only speckles with blinking rate from 40 Hz and higher are remained. By varying this filter threshold the vessels can be separated by its detected blinking rate. To detect its minimal speckle blinking rate panel (c) represents the six plots corresponds to the different filter threshold. The maximal decorrelation time corresponds to each case of filtering threshold can be estimated using equation (3). It is clearly seen from panel (c) that more vessels are appear at reduction filtering threshold.

Optical Coherence Tomography as a Tool in Reproductive Gynecology

15. Publication:  Panteleeva O., Kuznetsova I., Kachalina O., Eliseeva D., Grebenkina E., Gamayunov S., Kuznetsov S., Yunusova E., Gubarkova E., Kirillin M., Shakhova N. Femtosecond Biophotonics Laboratory5Optical Coherence Tomography as a Tool in Reproductive Gynecology. Sovremennye tehnologii v medicine, 7(1), 89-96 (2015)

The objective of the investigation was to show the advisability of using optical coherence tomography (OCT) for noninvasive diagnostics and monitoring of treatments in gynecological practice for female patients of reproductive age. OCT studies were performed during standard gynecological procedures like laparoscopy and colposcopy, as well as in course of pelvic inflammatory diseases of cervical neoplasia, with the use of an OKT1300U (BioMedTech, Russia). 330 patients of reproductive age (aged 18–45) were examined. The methods used for numeric processing of the OCT images were based on an analysis of histograms and on calculation of the first derivative of the OCT signal over depth. The use of OCT with numeric processing of the images increases the sensitivity of laparoscopy diagnosis of latent chronic salpingitis from 43.5 to 96.0%. In the case of minimal endometriosis, OCT can be used as a substitute for excisional biopsy for the visualization and verification of endometrioid heterotopias. The use of OCT in the case of cervical neoplasia in female patients of reproductive age enables a considerable decrease in surgical aggression during the diagnosis and treatment of cervical intraepithelial neoplasia and early forms of cancer. The use of OCT helps to maximize individualization and organ preservation during the diagnosis and treatment of gynecological pathology, and therefore to preserve the reproductive potential of young female patients.

 

 
Figure. OCT images: (а) unaltered fallopian tube, with moderate intensity of the signal, a structureless image, and decreased intensity with depth of the image; (b) chronic salpingitis, morphologically — the prevalence of edema, the heterogeneity of the image with zones of irregular form having low signal levels; (c) chronic salpingitis, morphologically — the prevalence of fibrosing, and local increases in signal intensity.

 

f20158 
Figure. OCT image of CIN III: (a) before PDT, with typical signs of pre-cancer of the cervix — a lack of structure with a slight decrease in the signal depth; (b) immediately after PDT, and the appearance of a boundary between the epithelium and the stroma due to these layers contrasting with the interstitial fluid; (c) one day after PDT, with increased signs of tissue edema, expansion and congestion of the vessels; (d) 6 days after PDT, showing total necrosis of the tumor, a structureless image with a sharp decrease in the signal depth; (e) one month after PDT — repair of the exocervix, with signs of the typical image of cervix, moderate scattering by the upper layer corresponding to the stratified squamous epithelium, and the lower layer — with more effectively scattering by the stroma, blurred boundary between the layers showing the presence of weakly scattering linear inclusions in the lower layer, corresponding to the reactive inflammation.

Development of the Methodology of Monitoring Experimental Tumors Using Multimodal Optical Coherence Tomography: the Choice of an Optimal Tumor Model

16. Publication: Sirotkina M., Buyanova N., Kalganova T., Karabut M., Elagin V., Kuznetsov S., Snopova L., Gelikonov G., Zaitsev V., Matveev L., Zagaynova E., Vitkin A., Gladkova N. Development of the Methodology of Monitoring Experimental Tumors Using Multimodal Optical Coherence Tomography: the Choice of an Optimal Tumor Model. Sovremennye tehnologii v medicine, 7(2), 7-13 (2015)

The objective of the research was to study the features of transplantation, growth and visualization of experimental tumors of animals, using multimodal optical coherence tomography (OCT) to develop the methodology of evaluation of individual tumor response to anti-cancer therapy. The research was carried out using an experimental high-speed spectral-domain multimodal OCT system developed at the Institute of Applied Physics of the Russian Academy of Sciences (Russia). The technical characteristics of the system are the following: speed of information acquisition, 20,000 А-scans per second; 1.3 μm wavelength; frame size, approximately 4×2 mm; lateral resolution, 25 μm; and depth resolution, 10 μm. We evaluated cross-polarized (CP) and microangiopathic (МА) OCT images. We performed an OCT study of the experimental tumor model of colon adenocarcinoma of mice Colo-26 on BALB/с mice (transplanted by suspension of tumor cells culture) inoculated subcutaneously into the thigh, intradermally into auricle, and in a dorsal skinfold window chamber. In the case of a deep subcutaneous location of a nodule, skin flap over the tumor was surgically opened. CP OCT images were compared with histological preparations (stained using hematoxylin and eosine). It was established that a Colo-26 tumor growing subcutaneously is not suitable with OCT monitoring investigations. Applying of tumor model with opened skin flap made it possible considerably to increase the visualization depth; however, it is not feasible to use this method for everyday OCT monitoring. The tumor grown within a dorsal window chamber is optimal for the visualization of blood vessels by means the OCT. Nevertheless, the inflammation and edema sometimes observed at the tumor site impeded the МА OCT study. Superficial tumors on the auricle are available for OCT investigation throughout their entire depth if the size of nodule does not exceed 1.5 mm. The tumor model on the auricle is convenient for physiological studies of the state of the vessels during the tumor growth. The optimal tumor model for dynamic multimodal OCT observation is a tumor on the auricle. Unlike a tumor located on the thigh it is characterized by a subcutaneous location of the nodule yet one which still remains accessible for visualization. The tumor evolving in the ear can be studied using dynamics which would be impossible for the tumor with opened skin flap. Tumors in the dorsal skin window can also be used for research, but the monitoring of their growth is limited to those that are no larger than 5–7 mm, as the nodule goes beyond the window due to the decreased elasticity of the skin, typical of these mice.

 
Figure. Model of Colo-26 tumor in the ear: (а) and (b) CP OCT images on days 5 and 11 after transplantation; the upper OCT image is the initial polarization, size 2.7×1.7 mm; the lower OCT image is the orthogonal polarization, size 2.7×1.7 mm; scale bar 1 mm; (c) histological preparations, stained with hematoxylin and eosine, frame size 3745×2809 μm, scale bar 50 μm; (d) and (e) МА OCT images on days 5 and 11 after transplantation, size of image 2×2 mm

Fluorescent Monitoring of Photodynamic Therapy for Skin Cancer in Clinical Practice

17. Publication: Gamayunov S., Grebenkina E., Ermilina A., Karov V., König K., Korchagina K., Skrebtsova R., Terekhov V., Turchin I., Shakhova N. Fluorescent Monitoring of Photodynamic Therapy for Skin Cancer in Clinical Practice. Sovremennye tehnologii v medicine, 7(2), 75-81 (2015)

The aim of the investigation was to assess the fluorescent imaging capabilities to monitor photodynamic therapy (PDT) of non-melanoma skin cancer, and study the correlation of PS (photosensitizer) fluorescence value (accumulation and photobleaching rate) and efficacy of the treatment provided. The study was conducted in the Nizhny Novgorod Regional Oncologic Hospital. We analyzed fluorescent images and PDT outcomes in 226 patients with non-melanoma skin carcinomas. The assessment of short-term treatment results revealed the relationship between PS photobleaching and tumor complete response rate: a complete response was found in 89% cases in complete photobleaching, in 87% cases — in partial photobleaching, and in 81% — in no photobleaching (p>0.05). However, we found no effect of PS accumulation rate on complete response rate. The analysis of long-term results with significant difference (p=0.044) showed tumor recurrence rate in low PS concentration (tumor/norm) to be 9.5%, while in moderate and high concentrations the recurrence rate appeared to be 4.1%. There was revealed the tendency for recurrence rate increase — 10.4% with no PS photobleaching versus 4.4% in PS complete and partial photobleaching (p=0.051). The patients with high accumulation rate and complete PS photobleaching had the best clinical findings, the observation period being from 4 to 40 months. Fluorescent monitoring enables to maintain noninvasive control of PS accumulation and photobleaching that can contribute to the selection of individual laser exposure parameters. It is reasonable to develop multimodal bioimaging for follow-up real-time monitoring of basic photodynamic reactions and treatment results.

 

f201510 
Table. The dependence of short- and long-term results on fluorescent parameters of a photosensitizer

Deformation-induced speckle pattern evolution and feasibility of correlational speckle tracking in optical coherence elastography

18. Publication: Zaitsev V.Y., Matveyev A.L., Matveev L.A., Gelikonov G.V., Gelikonov V.M., Vitkin A. Deformation-induced speckle pattern evolution and feasibility of correlational speckle tracking in optical coherence elastography. Journal of Biomedical Optics, 20(7), 075006 (2015)

Feasibility of speckle tracking in optical coherence tomography (OCT) based on digital image correlation (DIC) is discussed in the context of elastography problems. Specifics of applying DIC methods to OCT, compared to processing of photographic images in mechanical engineering applications, are emphasized and main complications are pointed out. Analytical arguments are augmented by accurate numerical simulations of OCT speckle patterns. In contrast to DIC processing for displacement and strain estimation in photographic images, the accuracy of correlational speckle tracking in deformed OCT images is strongly affected by the coherent nature of speckles, for which strain-induced complications of speckle “blinking” and “boiling” are typical. The tracking accuracy is further compromised by the usually more pronounced pixelated structure of OCT scans compared with digital photographic images in classical DIC applications. Processing of complex-valued OCT data (comprising both amplitude and phase) compared to intensity-only scans mitigates these deleterious effects to some degree. Criteria of the attainable speckle tracking accuracy and its dependence on the key OCT system parameters are established.

 

 
Figure. (a–1),(b–1), and (c–1) Simulated cross-correlation maps and (a–2), (b–2), and (c–2) corresponding speckle-tracking error based on the reference and uniaxially strained images. The speckle-tracking error as a function of depth in the right column is given for a fixed lateral position of the correlation window in the middle of the scan (i.e., not laterally averaged over the entire scan width). The correlation-window size is 16×16 pixels, and the spectral width ratio Δk∕k0 1∕8 (typ- ical of many OCT scanners). Displacements close to 0.5 px cause maximal speckle-splitting at z 165 px. Panels (a-1) and (a–2) are obtained via maximizing the cross-correlation by moving the correla- tion window in integer-pixel steps, and demonstrate strong tracking errors (up to 0.5 px) and strong decorrelation near the depth z 165 px. Panels (b–1) and (b–2) are obtained for complex-valued data using spectral sub pixel back-shift procedure which correctly compensates speckle splitting over the entire scan area, thus ensur- ing uniform correlation map and minimal tracking errors. Panels (c–1) and (c–2) correspond to the same subpixel tracking procedure, but applied to amplitude-only data with lost phase (label A), as well as to amplitude-only data with pseudophase found via Hilbert transform (label H). Compared to full complex-valued signals (b–1 and b–2), these give significantly larger residual decorrelation and tracking errors due to incorrectly compensated speckle splitting. Note that the color bars are not identical for all three correlation maps, to emphasize the spatial inhomogeneity of the residual decorrelation; furthermore, the vertical scale in plot (a–2) is 10 times larger than in (b–2) and (c–2).

 

 
Figure. Simulated cross-correlation maps and correlational speckle tracking results from complex-valued scans obtained for uniaxially strained sample for three different spectral parameters of the source. The image size is 256×256 pixels. The middle imbedded depth layer (50 pixels in thickness) is two times stiffer than the surrounding media. The average vertical strain is 0.5%, and consequently the displace- ments of the scatterers range from zero at the surface (imitating the rigid OCT probe) to 1.28 pixels at the bottom. The number of scatterers in the presented examples is 104 for each A-scan and correlation- window size is 16×16 pixels in all cases. Speckle tracking utilizes complex-valued data using the sub- pixel spectral back-shift procedure as per Fig. 2. Row (a) is for the source spectral width ratio Δk∕k0 ¼1∕16; (b) is for Δk∕k0 ¼1∕8; and (c) is for super-broadband source with Δk∕k ¼1∕2. Correspondingly, the effect of speckle blinking is much weaker for correlation plot (c–1) than for (a– 1) and (b–1). (a–2), (b–2), and (c–2) show the reconstructed displacements, with the thin dashed lines showing the difference in the slopes between the twice-stiffer layer and surrounding tissue. (a–3), (b–3), and (c–3) The derivative of the displacement (local strain) found via simplest one-pixel finite differences in the depth direction for a fixed horizontal coordinate of the correlation-window center (blue lines); red lines are the averaged values of strain found for 16 adjacent cuts in the vertical direction. (c–3) For super-broadband case, the reduced strain within the stiffer layer is fairly well-visible for the averaged (red) curve. All plots correspond to zero additive noise except for the inset in (c–3) that is calculated in the presence of −20 dB noise.

19. Publication: Kalganova T.I., Gubarkova E.V., Gamayunov S.V., Kiseleva E.V., Grebenkina E.B., Kuznetsov S.S., Finagina E.S., Shakhova N.М., Maslennikova A.V., Zagaynova E.V., Vitkin A., Gladkova N.D. The use of cross-polarization OCT in determining the dynamics of the state of pathological and normal tissues during radiation and photodynamic therapy. Modern tehnologies in medicine, 7(3), 119-129 (2015).

The results of the study of the medical pathomorphism of different kinds of tumors performed on the 14 patients showed that visual evaluation of CP OCT images of a tumor does not reveal any visible changes in response to RT, however it does register the reaction of the normal mucosa in the area exposed to the radiation. during the PdT of tumors of the skin and cervix mucosa CP OCT was capable of detecting the key morphological changes (edema, necrosis, and structural recovery). it can be applied most effectively at later stages of the follow-up observation (at 30–35 days after PdT) to evaluate the completeness of the recovery of the stromal component of the tissues. The use of CP OCT contributes to realization of non-invasive monitoring of the responses of tumors and the adjacent normal tissues to PDT and to RT that can be useful for evaluation of the effectiveness of therapy and to help in choosing optimal tactics for the treatment.

 
Figure. CP OCT images (a–c) of healthy mucosa of the mouth cavity from three volunteers. Here: CP OCT image in the initial polarization — the lower part of the image and in the orthogonal polarization — the upper part of the image, bar — 1 mm

Patterns of morphological changes in cT-26 experimental tumors during their natural growth

20. Publication: Kuznetsov S.S., Snopova L.B., Karabut M.M., Sirotkina M.A., Buyanova N.L., Kalganova T.I., Elagin V.V., Senina-Volzhskaya I.V., Barbashova L.N., Shumilova A.V., Zagaynova E.V., Vitkin A., Gladkova N.D. Features of morphological changes in experimental cT-26 tumors growth. Modern tehnologies in medicine, 7(3), 32-39 (2015)

The study began with investigation of the tumors on day 4 after the inoculation. At this early stage we could already see the formation of a tumor as a substrate node with an average volume of 0.8–1.0 mm3. Tumors in the early development stages were not immediately adjacent to the epidermis, a thin layer of dermis with blood-filled vessels could be detected between tumor cells and the basal layer. The carcinoma was of a histioid type and according to its microscopic structure was undifferentiated of degree IV malignancy (G) (Figure 1 (a)). As expected for a histioid tumor, stromal component was scarce, constituting only of an area of 0.35±0.2% of the neoplasm area while the parenchyma accounted for 99.6±0.3%. In deep parts of the tumor it was possible to identify individual sinusoidal blood-filled capillaries with diameters from 7 to 20 µm, accounting for 0.15±0.05% of the tumor, together with small arterioles which belonged to the dermis, and located within the carcinoma due to its growth infiltration (these were not taken into account in the calculation of the volume of the tumor vascular component). The tumor was characterized by a high level of proliferative activity, which was evidenced by the high number of mitotic cells — from 9 to 11 in the view field. No division pathology was recorded (Figure 1 (b)).

 
Figure. Growth of the CT-26 tumor, day 4 after inoculation. Hematoxylin and eosin staining; (a) ×10; (b) ×40

 

 
Figure. Growth of the CT-26 tumor, day 8 after inoculation. Hematoxylin and eosin staining; (a) ×10; (b) ×40

 

 
Figure. Growth of the CT-26 tumor, day 11 after inoculation. Hematoxylin and eosin staining; ×10

Towards advanced OCT clinical applications.

21. Publication: Kirillin M., Panteleeva O., Agrba P., Pasukhin M., Sergeeva E., Plankina E., Dudenkova V., Gubarkova E., Kiseleva E., Gladkova N., Shakhova N., Vitkin A. Towards advanced OCT clinical applications. Proc. of SPIE, 9542, 954201-17 (2015)

In this paper we report on our recent achievement in application of conventional and cross-polarization OCT (CP OCT) modalities for in vivo clinical diagnostics in different medical areas including gynecology, dermatology, and stomatology. In gynecology, CP OCT was employed for diagnosing fallopian tubes and cervix; in dermatology OCT for monitoring of treatment of psoriasis, scleroderma and atopic dermatitis; and in stomatology for diagnosis of oral diseases. For all considered application, we propose and develop different image processing methods which enhance the diagnostic value of the technique. In particular, we use histogram analysis, Fourier analysis and neural networks, thus calculating different tissue characteristics as revealed by OCT’s polarization evolution. These approaches enable improved OCT image quantification and increase its resultant diagnostic accuracy.

 
Figure. OCT-images of fallopian tube tissue in vivo:  norm (а), with prevalence of edema (b), and chronic alterations with fibrosis (c). Numerical processing of OCT images (scores S1 and S2 correspond to histogram and derivative analysis, respectively) for training (large symbols) and test (small symbols) groups. Rectangular zone demonstrates area indicating norm.

 

 
Figure. OCT-images of psoriasis (a-c) and scleroderma (d-f) skin sites before (a, d), in course (b, e) and after (c, f) treatment obtained with contact OCT probe with pressure of 0.07 N/mm2

An approach to OCT-based microvascular imaging using reference-free processing of complex-valued B-scans

22. Publication: Lev A. Matveev, Grigory V. Gelikonov, Alexandr L. Matveyev, Alexander A. Moiseev, Sergey Ksenofontov, Valentin M. Gelikonov, Marina A. Sirotkina, Natalia L. Buyanova, Natalia D. Gladkova, Valentin Demidov, Alex Vitkin, Vladimir Yu. Zaitsev. An approach to OCT-based microvascular imaging using reference-free processing of complex-valued B-scans. Proc. of SPIE, 9541, 954101-5 (2015)

We describe a modification of a recently proposed unconventional OCT approach to 3D microvasculature imaging based on high-pass filtering of B-scans in the lateral direction. The B-scans are acquired in M-mode-like regime with highly overlapped A-scans. The goal of the described modification is to suppress non-fluid artifacts in the resultant microcirculation images. The modification is based on the amplitude normalization procedure of complex-valued OCT signal before subsequent processing. This allows one to efficiently suppress imaging degradation due to the influence of very bright spots/lines (e.g. from hairs on the surface) and retain images of real flows inside the tissue without any artificial cut-off of the surface signal, or application of pixel-intensity thresholds, or signal classification approaches.

   
 Figure. A small fragment of high-density B-scan illustrating the distinction between the “long-dash” speckles corresponding to the solid tissue with motionless scatterers and “short-dash” speckles corresponding to moving scatterers within a vessel cross section (encircled in the figure). The size of the imaged region is about 70 μm in depth and 120 μm in the lateral direction.  Figure. An example of resultant B-scan after high-pass filtering and downsampling to the natural resolution of the OCT scanner. Only vessel cross sections containing moving scatterers are retained in the image. The size of the imaged region is about 700 μm in depth and 2000 μm in the lateral direction.

 

 
Figure. Demonstration of the efficiency of the proposed normalization for reducing the artifacts arising from hotspot areas on the tissue surface. Panel (a) - en face OCT image of mouse’s ear surface; panel (b) - en face  microvasculature maximum-intensity projection (MIP) image obtained by HP filtering of the full complex signal; panel (c) en face microvasculature MIP image obtained by filtering of the normalized signal. The MIP’s depth range is 600 μm and the chosen threshold frequency of the high-pass filter is 96 Hz. Significant reduction of artifacts related to surface hotspots is clearly seen in panel (c) in comparison with panel (b).

Photodynamic therapy monitoring with optical coherence angiography

23. Publication: Sirotkina M.A., Matveev L.A., Shirmanova M.V., Zaitsev V.Y., Buyanova N.L., Elagin V.V., Gelikonov G.V., Kuznetsov S.S., Kiseleva E.B., Moiseev A.A., Gamayunov S.V., Zagaynova E.V., Feldchtein F.I., Vitkin A., Gladkova N.D. Photodynamic therapy monitoring with optical coherence angiography. Scientific Reports. 2017. Принята к печати.

Photodynamic therapy (PDT) is a promising modern approach for cancer therapy with low normal tissue toxicity. This study was focused on a vascular-targeting Chlorine E6 mediated PDT. A new angiographic imaging approach known as M-mode-like optical coherence angiography (MML-OCA) was able to sensitively detect PDT-induced microvascular alterations in the mouse ear tumour model CT26. Histological analysis showed that the main mechanisms of vascular PDT was thrombosis of blood vessels and hemorrhage, which agrees with angiographic imaging by MML-OCA. Relationship between MML-OCA-detected early microvascular damage post PDT (within 24 hours) and tumour regression/regrowth was confirmed by histology. The advantages of MML-OCA such as direct image acquisition, fast processing, robust and affordable system opto-electronics, and label-free high contrast 3D visualization of the microvasculature suggest attractive possibilities of this method in practical clinical monitoring of cancer therapies with microvascular involvement.

Optimized phase gradient measurements and phase-amplitude interplay in optical coherence elastography

24. Publication: Zaitsev V.Y., Matveyev A.L., Matveev L.A., Gelikonov G.V., Sovetsky A.A., Vitkin A. Optimized phase gradient measurements and phase-amplitude interplay in optical coherence elastography. J Biomed Opt. 2016. 21(11):116005. doi: 10.1117/1.JBO.21.11.116005.

In compressional optical coherence elastography, phase-variation gradients are used for estimating quasistatic strains created in tissue. Using reference and deformed optical coherence tomography (OCT) scans, one typically compares phases from pixels with the same coordinates in both scans. Usually, this limits the allowable strains to fairly small values <10−4 to 10−3, with the caveat that such weak phase gradients may become corrupted by stronger measurement noises. Here, we extend the OCT phase-resolved elastographic methodology by (1) showing that an order of magnitude greater strains can significantly increase the accuracy of derived phase-gradient differences, while also avoiding error-phone phase-unwrapping procedures and minimizing the influence of decorrelation noise caused by suprapixel displacements, (2) discussing the appearance of artifactual stiff inclusions in resultant OCT elastograms in the vicinity of bright scatterers due to the amplitude-phase interplay in phase-variation measurements, and (3) deriving/evaluating methods of phase-gradient estimation that can outperform conventionally used least-square gradient fitting. We present analytical arguments, numerical simulations, and experimental examples to demonstrate the advantages of the proposed optimized phase-variation methodology.

Figure. Strain maps obtained from processing a pair of compared OCT scans of human biological tissue excised during a gynecological operation. Panel (a) is from Ref. 22 where the least-square fitting was used for determining the strain gradient. Panel (b) is the result of applying the currently proposed vector method for phase gradient estimation, with the same size of the processing window 16×16pixels as in panel (a); note that the “patchy” strain errors are now significantly reduced. Panel (c) is also reproduced from Ref. 22, to illustrate that histology confirmed the presence of the three-layer structure revealed in the elastographic maps. [(a) and (c) reproduced with permission].

Optical coherence tomography for visualizing transient strains and measuring large deformations in laser-induced tissue reshaping

25. Publication: Zaitsev V.Y., Matveyev A.L., Matveev L.A., Gelikonov G.V., Omelchenko A.I., Shabanov D.V., Baum O.I., Svistushkin V.M., Sobol E.N. Optical coherence tomography for visualizing transient strains and measuring large deformations in laser-induced tissue reshaping. Laser Physics Letters 2016, 13(11):115603

In the context of the development of emerging laser-assisted thermo-mechanical technologies for non-destructive reshaping of avascular collagenous tissues (cartilages and cornea), we report the first application of phase-sensitive optical coherence tomography (OCT) for visualizing transient strains involving supra-wavelength inter-frame displacements of scatterers. Usually phase-sensitive OCT assumes the visualization of sub-pixel and even sub-wavelength displacements of scatterers and fairly small strains (say, <10−3), which conventionally implies the necessity of averaging for enhancing the effective signal-to-noise ratio and, correspondingly, the application of small-amplitude actuators producing periodic deformations. The original approach used here allows for direct estimation of elevated strains ~10−2 (close to onset of intense speckle blinking) obviating the necessity of averaging and phase unwrapping for supra-wavelength inter-frame displacements. We demonstrate the possibility of mapping aperiodic thermally-induced transient strains with resultant large deformations on order of tens per cent. Such strains are typical in laser tissue reshaping, but are far beyond the range of conventionally discussed OCT-based strain mapping.

image2

Figure. Structural images, inter-frame variations in the OCT signal phase and reconstructed dynamic strains corresponding to laser-induced heating and subsequent cooling of the hydrogel phantom imitating eye cornea. Column (a) shows the structural images demonstrating formation and then disappearance of thermo-mechanically formed indentation at the glass-gel interface; (b) is the corresponding inter-frame phase variations; and (c) shows the reconstructed dynamic strain maps. Row 1 corresponds to the beginning of the IR-laser pulse, when initial local heating causes thermal expansion of the material. Row 2 is obtained 300 ms later when expansion is changed to contraction due to water redistribution. Row 3 is obtained another 5 s later about the end of the IR pulse when the indentation depth and the contraction of the surrounding material were maximal. Row 4 is obtained 3 s later when the sample temperature is almost equilibrated down to the initial room temperature and the phantom is recovering its initial shape, so that earlier contracted tissue in the center still is expanding.

Quantitative evaluation of atherosclerotic plaques using cross-polarization optical coherence tomography, nonlinear, and atomic force microscopy

26. Publication: Gubarkova EV, Kirillin MY, Dudenkova VV, Timashev PS, Kotova SL, Kiseleva EB, Timofeeva LB, Belkova GV, Solovieva AB, Moiseev AA, Gelikonov GV, Fiks II, Feldchtein FI, Gladkova ND. Quantitative evaluation of atherosclerotic plaques using cross-polarization optical coherence tomography, nonlinear, and atomic force microscopy. J Biomed Opt. 2016; 21(12):126010. doi: 10.1117/1.JBO.21.12.126010.

A combination of approaches to the image analysis in cross-polarization optical coherence tomography (CP OCT) and high-resolution imaging by nonlinear microscopy and atomic force microscopy (AFM) at the different stages of atherosclerotic plaque development is studied. This combination allowed us to qualitatively and quantitatively assess the disorganization of collagen in the atherosclerotic arterial tissue (reduction and increase of CP backscatter), at the fiber (change of the geometric distribution of fibers in the second-harmonic generation microscopy images) and fibrillar (violation of packing and different nature of a basket-weave network of fibrils in the AFM images) organization levels. The calculated CP channel-related parameters are shown to have a statistically significant difference between stable and unstable (also called vulnerable) plaques, and hence, CP OCT could be a potentially powerful, minimally invasive method for vulnerable plaques detection.

image3

Figure. Visualisation of different stages of a plaque development by CP OCT, histology, SHG, and AFM. (a–f) CP OCT images (upper panel = copolarization channel, lower panel = CP channel), (g–l) histological slides stained with H&E, (m–r) SHG images, and (s–x) AFM images. The rectangles in the CP OCT images indicate the area covered by histological slides and SHG images, respectively. The arrow points to accumulations of foam and inflammatory cells at the border of the fibrous cap and the lipid core. The square in the SHG images indicates the area studied by AFM.

Multimodal Optical Coherence Tomography in Visualization of Brain Tissue Structure at Glioblastoma (Experimental Study)

27. Publication: Yashin К.S., Karabut M.M., Fedoseeva V.V., Khalansky A.S., Matveev L.A., Elagin V.V., Kuznetsov S.S., Kiseleva E.B., Kravets L.Ya., Medyanik I.А., Gladkova N.D. Multimodal Optical Coherence Tomography in Visualization of Brain Tissue Structure at Glioblastoma (Experimental Study). Sovremennye tehnologii v medicine 2016. 8(1): 73–81. http://dx.doi.org/10.17691/stm2016.8.1.10

Multimodal OCT including cross-polarization and microangiographic OCT modes is a promising method of intraoperative diagnosis of gliomas. The possibility to combine several investigation modes allows to simultaneously receive information on both the tissue structure and the state of the microvasculature. Such an OCT technique has great potential as a method for determination of the boundaries of infiltrative gliomas, based on an evaluation of the structure of the tissue and the specific details of different aspects of the microvascular network.

image4

Figure. CP OCT visualization of rat brain with an inoculated glioma 101.8: (а) image in co-polarization; (b) image in cross-polarization: blue dotted line — area of destruction of the cortex with a tumor node; green dotted line — peritumoral area; yellow dotted line — area of the normal cortex; images (а) and (b) consist of several CP OCT images, the length of each being 13.5 mm; (c)–(h) three dimensional (3D) reconstructions of the cortex areas in co- (c)–(e) and cross-polarization (f)–(h): (c), (f) area of destruction with a tumor node; (d), (g) peritumoral area; (e), (h) region of normal cortex.

Multiphoton Tomography and Cross-Polarization Optical Coherence Tomography for Diagnosing Brain Gliomas: Pilot Study

28. Publication: Dudenkova V.V., Yashin K.S., Kiseleva E.B., Kuznetsov S.S., Timofeeva L.B., Khalansky A.S., Elagin V.V., Gubarkova E.V., Karabut M.M., Pavlova N.P., Medyanik I.A., Kravets L.Ya., Gladkova N.D. Multiphoton Tomography and Cross-Polarization Optical Coherence Tomography for Diagnosing Brain Gliomas: Pilot Study. Sovremennye tehnologii v medicine 2016. 8(4): 64–73

The combination of MPT and OCT offer great potential for intraoperative diagnostics during the surgery of glial tumors. MPT is characterized by its high spatial resolution and could become a fully-fledged method for express-biopsy, because it allows visualization of all the diagnostically relevant structural elements of the tissues. Nevertheless, in its existing form, the possibilities for its use in determining the boundaries of tumor invasion are limited due to its small scanning area, its relatively low speed and the need for special conditions in the operating theater. By contrast, the spatial resolution of CP OCT is sufficient to determine tumor infiltration, and the accuracy of the method increases when cross-polarization mode is used. The wide application of these methods in clinical practice requires more extensive studies to clarify the criteria for differentiation between the tumor and the surrounding tissues.

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Figure. Rat glioblastoma 101.8 (a)–(d) and the cerebral cortex immediately adjacent to the tumor (e)–(h). Comparative study with MPT methods in two-photon excitation autofluorescence mode with an excitation wavelength of 750 nm and detection in the range 409–660 nm (d), (h), and CP OCT (а), (e): in co-polarization — upper part of the image; in cross-polarization — lower part of the image. White rectangle — area, corresponding to histological images (b), (f); green rectangle — area, corresponding to histological images (c), (g). The histological specimens (c), (g) contain the area from which the MPT images were obtained. Histologically stained with hematoxylin and eosin.

Ex vivo Visualization of Human Gliomas with Cross-Polarization Optical Coherence Tomography: Pilot Study

29. Publication: Yashin K.S., Gubarkova E.V., Kiseleva E.B., Kuznetsov S.S., Karabut M.M., Timofeeva L.B., Snopova L.B., Moiseev A.A., Medyanik I.А., Kravets L.Ya., Gladkova N.D.. Ex vivo Visualization of Human Gliomas with Cross-Polarization Optical Coherence Tomography: Pilot Study. Sovremennye tehnologii v medicine 2016. 8(4): 14–21

The histological features of white matter and of gliomas of different grades of malignancy can be differentiated in CP OCT images according to characteristics of their OCT signal such as intensity, homogeneity and the dynamics of signal decay in co- and cross-polarization.

The spatial resolution of OCT (about 10 µm depth wise and 15 µm along the transverse axis) is sufficient to differentiate diagnostically relevant changes in the microstructure of brain tissue: the different density/correlation between cellular and fibrous structures in the tissue, the presence of necrosis and hemorrhages as well as the presence of myelinated fibers in the tissue. High heterogeneity along the transverse axis of the OCT signal or its complete absence in cross-polarization is a direct indicator of highly malignant glioblastomas.

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Figure. CP OCT and the corresponding histological images of ex vivo brain tissue specimens: (а)–(c) brain white matter at the edge of tumor resection; (d)–(o) astrocytic tumors of different grades of malignancy. (а), (d), (g), (j), (m) CP OCT images in co-polarization — upper part of the image, in cross-polarization — lower part of the image. White rectangle — area corresponding to histological images (b), (e), (g), (k), (n); green rectangle — area corresponding to histological images (c), (f), (i), (l), (o). Histologically stained with hematoxylin and eosin.

Robust strain mapping in optical coherence elastography by combining local phase-resolved measurements and cumulative displacement tracking

30. Publication: Zaitsev V.Y., Matveyev A.L., Matveev L.A., Gelikonov G.V., Gubarkova E., Gladkova N.D., Vitkin A. Robust strain mapping in optical coherence elastography by combining local phase-resolved measurements and cumulative displacement tracking. Proc. SPIE 9710, Optical Elastography and Tissue Biomechanics III, 97100O (March 15, 2016) doi:10.1117/12.2211117

We report a novel hybrid method of robust strain mapping in compressional optical coherence elastography using combined phase measurements on sub-wavelength-scale and cumulative pixel-scale displacement tracking. This hybrid nature significantly extends the range of measurable displacements and strains in comparison with conventional direct phase-resolved measurements. As a result, the proposed strain-mapping method exhibits significantly increased robustness with respect to both additive noise and decorrelation noise produced by displacements and strains. The main advantages of the proposed approach are illustrated by numerical simulations. Experimental examples of obtained strain maps for phantoms and real biological tissues are also presented.

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Figure. A real example demonstrating that the strain map obtained by the developed method based on fitting local strain gradients is able to reveal structural features of the sample that are not distinguishable in the conventional morphological image. Panel (a) is such a conventional structural image of a hamster's cheek-pouch tissue representing two layers of the pouch wall one above another. The interface between the two layers indistinguishable in the structural scan is clearly visualized as an inter-layer with increased strain in the strain map shown in panel (b) (see the region labelled by the dashed-line rectangle). The lower parts of both plots are intentionally masked since the signal in these region is exclusively due to system noises. The processing-window size is 10 px in the vertical and 16px in the horizontal direction.

Vessel-contrast enhancement in label-free optical coherence angiography based on phase and amplitude speckle variability

31. Publication: Matveev L.A., Demidov V., Moiseev A.A., Gelikonov G.V., Matveyev A.L., Gelikonov V.M., Karabut M.M., Gubarkova E.V., Finagina E.S., Sirotkina M.A., Maslennikova A.V., Gladkova N.D., Vitkin A., Zaitsev V.Y. Vessel-contrast enhancement in label-free optical coherence angiography based on phase and amplitude speckle variability. Proceedings of the SPIE. 2016. Volume 9917, id. 99171S 9 pp.

Recently proposed in vivo label-free optical coherence angiography techniques based on phase and amplitude speckle variability often require additional signal pre- and post processing operations to enhance vessel-contrast. We observe here 1) contrast enhancement by optimizing the signal normalization/weighing before processing; 2) algorithm based on Kasai estimator for phase compensation between processed A-scans to reduce masking role of motion artifacts; and 3) image projection through the imaging depth for en face plotting. We demonstrate the efficiency of proposed additional algorithms as for the microcirculation imaging of hamsters cheek in vivo as for the preliminary microcirculation imaging of patients after radiotherapy. This technical framework complete in details our recent publications on M-Mode like OCT algorithms and its implementation.

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Figure. Examples of efficiency of phase equalization procedure applied to dataset acquired from hamster cheek that was affected by the animal breathing, heart-beating and other translational motions. Panel (a) is the en face MIP of OCT angiogram of the hamster cheek acquired and processed without preliminary phase compensation; panel (b) is one of the By-scan (along the processing Y-direction) corresponding angiogram (a) and labeled there with a white dashed line. Panel (c) is en-face MIP and panel (d) is By-scan of the same volumetric dataset but pre-processed with the phase compensation algorithm.

Characterization of atherosclerotic plaques by cross-polarization optical coherence tomography

32. Publication: Gubarkova E.V., Dudenkova V.V., Feldchtein F.I., Timofeeva L.B., Kiseleva E.B.,. Kuznetsov S.S, Moiseev A.A., Gelikonov G.V., Vitkin A.I., Gladkova N.D. Characterization of atherosclerotic plaques by cross-polarization optical coherence tomography. Proc. SPIE. 9689, Photonic Therapeutics and Diagnostics XII, 96893F. doi: 10.1117/12.2210822

We combined cross-polarization optical coherence tomography (CP OCT) and non-linear microscopy based on second harmonic generation (SHG) and two-photon-excited fluorescence (2PEF) to assess collagen and elastin fibers in the development of the atherosclerotic plaque (AP). The study shows potential of CP OCT for the assessment of collagen and elastin fibers condition in atherosclerotic arteries. Specifically, the additional information afforded by CP OCT, related to birefringence and cross-scattering properties of arterial tissues, may improve the robustness and accuracy of assessment about the microstructure and composition of the plaque for different stages of atherosclerosis.

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Figure 1. The stage of lipid pool in the intimal thickening coronary artery. Histological slides stained with Van Gieson (A), Orcein (B) and H&E (C). SHG (D), 2PEF (E) and combined SHG-2PEF (F) images. CP OCT image (G).Foam cells (arrow) in the intima in (C) which form the lipid streak with a weak OCT signal in cross-polarization (white arrow) and a high-level homogeneous OCT signal in co-polarization (green arrow) in (G). Here and after: top = co-polarization CP OCT image, middle = cross-polarization CP OCT image, bottom = Pythagorean sum of the two polarization channels — the bottom image. The images in (A)–(F) correspond to the region indicated by squares in (G).

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Figure 2. The stage of “mature” vulnerable atherosclerotic plaque. Histological slides stained with Van Gieson (A), Orcein (B) and H&E (С). SHG (D), 2PEF (E) and combined SHG-2PEF (F) images. CP OCT image (G). FC - fibrous cap, NC- necrotic core. The accumulations of foam and inflammatory cells (arrows) at the border of the FC and the NC in (C). The images in (A)–(F) correspond to the region indicated by squares in (G).

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Figure 3. The stage of “mature” stable atherosclerotic plaque. Histological slides stained with Van Gieson (A), Orcein (B) and H&E (C). SHG (D), 2PEF (E) and combined SHG-2PEF (F) images. CP OCT image (G). FC - fibrous cap. The imagesin (A)–(F) correspond to the region indicated by squares in (G).

OCT-based approach to local relaxations discrimination from translational relaxation motions

33. Publication: Matveev L., Matveyev A, Gubarkova E., Gelikonov G., Sirotkina M., Kiseleva E., Gelikonov V., Gladkova N., Vitkin A., Zaitsev V. OCT-based approach to local relaxations discrimination from translational relaxation motions. Proc. of SPIE 2016. Vol. 9887, 98870C

Multimodal optical coherence tomography (OCT) is an emerging tool for tissue state characterization. Optical coherence elastography (OCE) is an approach to mapping mechanical properties of tissue based on OCT. One of challenging problems in OCE is elimination of the influence of residual local tissue relaxation that complicates obtaining information on elastic properties of the tissue. Alternatively, parameters of local relaxation itself can be used as an additional informative characteristic for distinguishing the tissue in normal and pathological states over the OCT image area. Here we briefly present an OCT-based approach to evaluation of local relaxation processes in the tissue bulk after sudden unloading of its initial pre-compression. For extracting the local relaxation rate we evaluate temporal dependence of local strains that are mapped using our recently developed hybrid phase resolved/displacement-tracking (HPRDT) approach. This approach allows one to subtract the contribution of global displacements of scatterers in OCT scans and separate the temporal evolution of local strains. Using a sample excised from of a coronary arteria, we demonstrate that the observed relaxation of local strains can be reasonably fitted by an exponential law, which opens the possibility to characterize the tissue by a single relaxation time. The estimated local relaxation times are assumed to be related to local biologically-relevant processes inside the tissue, such as diffusion, leaking/draining of the fluids, local folding/unfolding of the fibers, etc. In general, studies of evolution of such features can provide new metrics for biologically-relevant changes in tissue, e.g., in the problems of treatment monitoring.

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Figure. Spatial distribution of the relaxation rate. Panel (a) represents variations in the lateral directions of local relaxation rate inside the coronary vessel wall on the depth ~ 150 mcm from the top of the vessel surface. This cross-section is indicated by dashed line on Panel (b) represents OCT image (B-scan).

Применение мультимодальной оптической когерентной томографии в оценке эффективности терапии рака

34. Publication: Сироткина М.А., Киселева Е.Б., Губарькова Е.В., Буянова Н.Л., Елагин В.В., Зайцев В.Ю., Матвеев Л.А., Матвеев А.Л., Кириллин М.Ю., Геликонов Г.В., Геликонов В.М., Кузнецов С.С., Загайнова Е.В., Гладкова Н.Д. Применение мультимодальной оптической когерентной томографии в оценке эффективности терапии рака. Вестник РГМУ. № 4, 2016, с. 4-11

Поиск новых способов прижизненной функциональной визуализации биологических тканей, которые позволяют выявлять ранний ответ опухоли на выбранную терапию с целью коррекции курса лечения, актуальная задача современной медицины. В качестве такого способа в работе предложена мультимодальная оптическая когерентная томография (ММ ОКТ), которая сочетает в себе кросс-поляризационную ОКТ (КП ОКТ) для визуализации структуры ткани и оценки состояния соединительнотканного компонента, ОКТ-микроангиографию (ОКТ МА) для визуализации сосудистого русла и ОКТ-эластографию для изучения жесткости ткани. Эффективность метода проверяли на примере действия фотодинамической терапии (ФДТ), поскольку основными мишенями ФДТ являются клеточный и сосудистый компоненты опухоли. В качестве объекта исследования была выбрана карцинома кишечника мыши СТ26, локализованная на ухе мыши. Показано, что с помощью ММ ОКТ можно оценить эффективность ФДТ, а именно: по КП ОКТ отличить опухоль с некрозом от интактной опухоли, по ОКТ МА выявить расстройства кровообращения, приводящие к замедлению или остановке кровотока и дальнейшей гибели опухоли, а по ОКТ-эластографии определить жесткость нормальной и патологической ткани.

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Рисунок. Пример визуализации реакции сосудов карциномы кишечникаCT26, локализованной на ухе мыши, на фотодинамическую терапию методом ОКТ МА (А–В) и методом флуоресцентной микроскопии (Г, Д). (А) и (Г)— опухоль до терапии, (Б)— опухоль сразу после терапии, (В) и(Д)— опухоль через 24 ч после терапии. Размер бара— 0,5 мм. Область опухоли обведена пунктирным кружком.

35. Publication: Gubarkova E.V., Dudenkova V.V., Feldchtein F.I., Timofeeva L.B., Kiseleva E.B., Kuznetsov S.S., Shakhov B.E., Moiseev A.A., Gelikonov V.M., Gelikonov G.V., Vitkin A., Gladkova N.D. Multi-modal optical imaging characterization of atherosclerotic plaques. Journal of Biophotonics. 2016; 9(10): 1009-1020. doi: 10.1002/jbio.20150022

We combined cross-polarization optical coherence tomography (CP OCT) and non-linear microscopy based on second harmonic generation (SHG) and two-photon-excited fluorescence (2PEF) to assess collagen and elastin fibers and other vascular structures in the development of atherosclerosis, including identification of vulnerable plaques, which remains an important clinical problem and imaging application. CP OCT’s ability to visualize tissue birefringence and cross-scattering adds new information about the microstructure and composition of the plaque. However its interpretation can be ambiguous, because backscattering contrast may have a similar appearance to the birefringence related fringes. Our results represent a step towards minimally invasive characterization and monitoring of different stages of atherosclerosis, including vulnerable plaques.

Figure. CP OCT image of intimal thickening in the human coronary artery. The dark stripe in the cross-polarization channel (arrow) is a polarization fringe related to the phase retardation between two eigen polarization states. It is histologically located in the area of the lipid pool, however this stripe is a polarization artifact, rather than direct visualization of the lipid pool.

Hybrid method of strain estimation in optical coherence elastography using combined sub-wavelength phase measurements and supra-pixel displacement tracking

36. Publication: Zaitsev V. Y., Matveyev A. L., Matveev L. A., Gelikonov G. V., Gubarkova E. V., Gladkova N. D., Vitkin A. Hybrid method of strain estimation in optical coherence elastography using combined sub-wavelength phase measurements and supra-pixel displacement tracking. Journal of Biophotonics. 2016; 9(5): 499–509. doi: 10.1002/jbio.201500203

A novel hybrid method which combines sub-wavelengthscale phase measurements and pixel-scale displacement tracking for robust strain mapping in compressional optical coherence elastography is proposed. Unlike majority of OCE methods it does not rely on initial reconstruction of displacements and does not suffer from the phasewrapping problem for super-wavelength displacements. Its robustness is enabled by direct fitting of local phase gradients obviating the necessity of phase unwrapping and error-prone numerical differentiation. Furthermore, axial displacements significantly exceeding not only the optical wavelength, but pixel scales (i.e., multiple wavelengths) can be efficiently tracked and compensated. This feature strongly reduces errors in phase-gradient estimation and ensures high robustness with respect to both additive and decorrelation noises.

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Figure. Illustration of exceptionally high tolerance of the proposed method to noises: contrast of only 25% in the stiffness of the layers is clearly seen in the strain map even for equal intensities of the OCT signal and additive noise (SNR = 0 dB).

 

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