Alex Vitkin

At a Glance

• Fellow, OSA and SPIE
• Medical Biophysics Excellence in Mentorship Award
• Radiation Oncology Sustained Excellence in Research Award
• Radiation Medicine Research Productivity Award (2x)
• International Visiting Lecturer (invited seminars in 21 countries)
• Board certification, radiation oncology physics (M-CCPM)
• 180 peer-reviewed papers, 6 patents
• Research interest in multi-functional optical coherence tomography (OCT) – using OCT to measure tissue morphology, its blood and lymphatic microcirculation, and its biomechanical properties in vivo.
• Research interest in polarized light in biomedicine – using polarimetric techniques to quantify biophysical properties of tissues (anisotropy, heterogeneity, chirality).

Short Bio

Dr. Alex Vitkin is an engineering physicist/biomedical engineer by training, with further specialization in medical physics and biomedical optics.  He is currently a professor of Medical Biophysics and Radiation Oncology at the University of Toronto, a senior scientist at the Ontario Cancer Institute (Biophysics and Bio-imaging division), and a clinical medical physicist at Princess Margaret Cancer Centre (all in Toronto, Ontario, Canada).  He has published over 180 papers and book chapters on diagnostic and therapeutic uses of light in biomedicine, consults for several biophotonics companies, and currently serves as a topical editor of Optics Letters (2^nd 3-year term).  He has lectured widely at national and international levels, including delivering special seminars and summer school modules on biophotonics in Mexico, Brazil, Taiwan, Colombia, New Zealand, Ukraine, Germany, USA, Cyprus, and Russia; he is currently an active participant in the SPIE Visiting Lecturer and OSA Travelling Lecturer programs.  Dr. Vitkin is also a board-certified medical physicist thru the Canadian College of Physicists in Medicine (CCPM), and is a Fellow of the Optical Society of America (OSA) and of the Society of Photo-Optical Instrumentation Engineers (SPIE).

Research Synopsis

Biophotonics, or the convergence of light + life, is an active research field that encompasses fundamental science, bio-instrumentation engineering, pre-clinical testing, and a variety of clinical applications. The common core theme is biomedical optics – lasers, optical fibers, photodetectors, light propagation in tissue, diagnostic and therapeutic interactions – and the applications range from early disease detection to functional tissue assessment to light-based therapies to treatment response monitoring. Light is versatile and is of great importance to human life and health, and the range of research projects in MBP Biophotonics Lab reflects that versatility!

Recent work in the Vitkin Laboratory has focused on (1) functional tissue assessment for treatment response monitoring using optical coherence tomography (OCT), and (2) tissue pathology detection using polarized light. Briefly:

(1) OCT is an emerging medical imaging modality that is essentially an in-vivo microscope without the bulky equipment; owing to advances in photonics and fiber optics technologies, small practical systems can be engineered for use in live animal and patients. Like a microscope, it enables micron-scale resolution but can also image below the tissue surface to a depth of 1-3 mm (hence the “tomography” part of the OCT name). We and others have extended OCT’s contrast mechanisms to visualize tissue microvascular blood flow, tissue biomechanical stiffness properties, and more recently lymphatic microcirculation. Importantly, these exciting functional imaging capabilities do not require injection of potentially toxic contrast agents. We are further developing these methods, and exploring their biomedical use. For example, can OCT “shed light” on radiotherapy? Here, we are using functional OCT for quantifying the radiobiological response of irradiated microvasculature to understand, optimize and personalize cancer radiotherapy treatments.

(2) Polarization properties of light remain relatively unexplored in biomedicine, yet contain a wealth of potentially useful tissue biophysical information. We are developing novel polarimetric methods suitable for bulk tissue analysis, primarily focusing on the so-called Mueller Matrix (MM) formalism. Work in this space encompasses the development of advanced experimental polarimetry point-sensing and imaging systems, accurate modelling of polarized light propagation through / interaction with biological tissues, and validation testing in ex-vivo bulk tissues (both animal and human). A recent illustrative clinical example is the use of polarimetry for detecting residual tumour at the margins of the resection cavity during breast-conserving surgery (lumpectomy). Here, we propose to use MM-derived metrics to rapidly identify regions of breast tissue heterogeneity and anisotropy that correspond to pathology, and use another technology of mass spectrometry (very accurate but very slow, hence its need for polarimetric guidance) to perform localized definitive diagnosis. If successful, this hybrid technology approach would enable breast surgeons to perform lumpectomies more successfully, minimizing the risk of recurrence due to tumour inadvertently left behind.

Potential research projects in the Vitkin Lab deal with photonic engineering, signal processing and image analysis (including AI / machine learning methods), light propagation in tissue modeling, radiation therapy delivery and dosimetry, pre-clinical validation and testing in mice, surgical specimens imaging, and clinical system engineering and use.

Recent Publications

OCT

• Demidov V, Maeda A, Sugita M, Madge V, Sadanand S, Flueraru C and Vitkin IA Preclinical longitudinal imaging of tumor microvascular radiobiological response with functional optical coherence tomography, Sci Reports 8 38 (2018)
• Demidov V, Demidova N, Pires L, Demidova O, Flueraru C, Wilson B, and Vitkin IA Volumetric tumor delineation and assessment of its early response to radiotherapy with optical coherence tomography, J Biomed Opt 23 087003 - doi: 10.1364/BOE.424045 (2021)
• Demidov V, Zhao X, Demidova O, Pang HYM, Flueraru C, Liu F-F, and Vitkin IA Preclinical quantitative in-vivo assessment of skin tissue vascularity in radiation-induced fibrosis with optical coherence tomography, J Biomed Opt 23 087003 - 9 (2018)
• Weatherbee A, Popov I and Vitkin IA Accurate viscosity measurements of flowing aqueous glucose solutions with suspended scatterers using a dynamic light scattering approach with optical coherence tomography, J Biomed Opt 22 087003 – doi: 10.1117/1.JBO.22.8.087003 (2017)
• Maslennikova A, Sirotkina M, Moiseev A, Finagina E, Ksenofontov S, Gelikonov G, Matveev L, Kiseleva E, Zaitsev V, Zagaynova E, Feldchtein F, Gladkova N and Vitkin IA In-vivo longitudinal imaging of microvascular changes in irradiated oral mucosa of radiotherapy cancer patients using optical coherence tomography, Sci Reports 7 16505 – doi: 10.1038/s41598-017-16823-2 (2017)
• Zaitsev VY, Matveyev AL, Matveev LA, Gubarkova EV, Sovetsky AA, Sirotkina MA, Gelikonov GV, Zagaynova EV, Gladkova ND and Vitkin IA Practical obstacles and their mitigation strategies in compressional optical coherence elastography of biological tissues, J Innov Opt Health Sci 10 1742006–13 (2017)

Polarimetry

• Fung KB, Samim M, Gribble A, Bazdra V and Vitkin IA Monte Carlo simulation of polarization-sensitive second harmonic generation and propagation in biological tissue J Biophotonics 11 e201800036 – 11, doi:10.1002/jbio.201800036 (2018)
• Forward S, Gribble A, Lindenmayer A, Alali S and Vitkin IA Flexible polarimetric probe for 3x3 Mueller matrix measurements of tissue, Sci Reports 7 11958 – doi: 10.1038/s41598-017-12099-8 (2017)
• Ahmad I, Gribble A, Murtza I, Ikram M, Pop M and Vitkin IA Polarization image segmentation of radiofrequency ablated porcine myocardial tissue, PLoS One 12 e0175173 – doi: 10.1371/journal.pone.0175173 (2017)
• Woolman M, Gribble A, Bluemke E, Zou J, Ventura M, Bernards N, Wu M, Howard J. Ginsberg HJ, Sunit Das S, Vitkin IA and Zarrine-Afsar A, Optimized mass spectrometry analysis workflow with polarimetric guidance for ex vivo and in situ sampling of biological tissues Sci Reports 7 468 – doi: 10.1038/s41598-017-00272-y (2017)
• Tata A, Gribble A, Ventura M, Ganguly M, Bluemke E, Ginsberg H, Jaffray DA, Ifa DR, Vitkin IA and Zarrine-Afsar A, Wide-field tissue polarimetry allows efficient localized mass spectrometry imaging of biological tissues, Chem Sci 7 2162-9 (2016)

For a complete list, including PDF's of most papers, click here.

Graduate Students

Nader Allam
Jigar Lad
Michael Singh
Jeffrey Zabel