Optical Coherence Tomography Optical Coherence Tomography (OCT) is a novel imaging technique that is analogous to ultrasound imaging with low coherence, near-infrared light waves. It holds the potential to provide researchers and medical clinicians with in vivo, real-time images with sub-cellular resolution (5 - 10 microns). These images can be acquired non-invasively and without damage to the sample. OCT promises to advance state-of-the-art microstructural and functional imaging for bio-medical applications with in vivo visualization of individual cells or cell clusters in intact tissues. The ability to perform real-time, non-invasive "histopathology" can have a major impact on research and clinical management.
Doppler optical coherence tomography (DOCT) is a powerful tool for providing not only subsurface microstructural, but also functional information. Our group's system is able to image blood vessels as small as ~ 30 μm in diameter, with blood flows as slow as ~ 20 μm/s. Photodynamic therapy (PDT), once a "novel" cancer treatment, is now a major research field in biophotonics and is gaining clinical popularity. The highly sensitive DOCT system was used to image microcirculation in normal rat colon and a rat prostate cancer model before, during, and after PDT. The results demonstrate that DOCT can monitor the vascular changes during PDT and that DOCT can highlight the differences in tissue response with different treatment protocols. Furthermore, DOCT demonstrated differences in response between normal and cancerous tissues.
Renee Korol, Babajide Togonu-Bickersteth, Victor Yang, Stamen Dimov, Pracha Vatsya, Maggie Gordon, Alex Vitkin, Liying Liu, Peter Canham, Sharon Clarke, Alexandra Lucas
Atherosclerosis is the underlying vascular pathology that initiates arterial thromboembolic occlusions (myocardial infarctions, strokes and peripheral vessel blockage). Two imaging modalities, Optical Coherence Tomography (OCT) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), were investigated for detection and compositional analysis of unstable plaque associated with plaque erosion and sudden occlusion. OCT produces high resolution images
whereas mass spectrometry images provide information on the spatial distribution of chemical elements. Diseased carotid arteries taken from patients with high-risk lesions were imaged with OCT and ToF-SIMS to give molecular and metabolic information, and matched with histopathology. OCT results show clear indications of vascular remodeling by the presence of fatty acid deposits, fibrous tissue and calcifications. ToF-SIMS further characterized changes based on
secondary ion topography analysis where a high 23Na/39K ratio was indicative of arterial tissue degradation and the amount of 40Ca corresponded with late stage atherosclerosis. This pilot experiment has demonstrated that in vitro OCT imaging and ToF-SIMS of diseased carotid arteries have scientific merit for targeting clinically relevant morphology and metabolic changes to compare stable and unstable plaque. These optical techniques provide complimentary metabolic and molecular information on unstable plaque, specifically cell break-down with altered ion ratios of 23Na, 39K and 40Ca.
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