Laser speckle contrast imaging (LSCI) is becoming an established method for full-field imaging of blood flow dynamics
in animal models. Blood flow pulsation originated from heart beat affects blood flow measurement results of LSCI and it
is considered as major physiology noise source for most biomedical applications. But in some biomedical applications,
the details of the pulsation process might provide useful information for disease diagnostics. In this study, we
investigated the ability as well as the limitation of LSCI in monitoring flow pulsation in phantom study. Both intralipid
(2% - 5%) and human whole blood samples are used in phantom study. A syringe pump is controlled by a computer-programmable
motor controller and liquid phantom is pushed through a 400 μm ID capillary tube by the pump at
different pulsation patterns, varied in frequency (1-7 Hz),
valley-to-peak ratio (10%-50%), acceleration/deceleration rate,
etc. Speckle contrast images are acquired at 15-30
frames-per-seconds. Our results show: (1) it is very hard for LSCI to
pick up signals from high frequency pulsation (5-7 Hz), which is close to the heart back frequency of rats. This might be
caused by the nature of fluid dynamics of blood during pulsation. LSCI might not work well for animal models in
detecting pulsation. (2) With low frequency pulsation (1 Hz, close to human normal pulsation rate), our experimental
results shows from most pulsation patterns, LSCI could catch the fine details of the blood flow change in a cycle. LSCI
might be used for studying human blood flow pulsation.
Recent advances in catheter-based optical coherence tomography (OCT) have provided the necessary resolution and acquisition speed for high-quality intravascular imaging. Complications associated with clearing blood from the vessel of a living patient have prevented its wider acceptance. We identify a surgical application that takes advantage of the vascular imaging powers of OCT but that circumvents the difficulties. Coronary artery bypass grafting (CABG) is the most commonly performed major surgery in America. A critical determinant of its outcome has been postulated to be injury to the conduit vessel incurred during the harvesting procedure or pathology preexistent in the harvested vessel. As a test of feasibility, intravascular OCT imaging is obtained from the radial arteries (RAs) and/or saphenous veins (SVs) of 35 patients scheduled for CABG. Pathologies detected by OCT are compared to registered histological sections obtained from discarded segments of each graft. OCT reliably detects atherosclerotic lesions in the RAs and discerns plaque morphology as fibrous, fibrocalcific, or fibroatheromatous. OCT is also used to assess intimal trauma and residual thrombi related to endoscopic harvest and the quality of the distal anastomosis. We demonstrate the feasibility of OCT imaging as an intraoperative tool to select conduit vessels for CABG.
Optical contrast is often the limiting factor in the imaging of live biological tissue. Studies were conducted in postmortem human brain to identify clinical applications where the structures of interest possess high intrinsic optical contrast and where the real-time, high-resolution imaging capabilities of optical coherence tomography (OCT) may be critical. Myelinated fiber tracts and blood vessels are two structures with high optical contrast. The ability to image these two structures in real time may improve the efficacy and safety of a neurosurgical procedure to treat Parkinson's disease called deep brain stimulation (DBS). OCT was evaluated as a potential optical guidance system for DBS in 25 human brains. The results suggest that catheter-based OCT has the resolution and contrast necessary for DBS targeting. The results also demonstrate the ability of OCT to detect blood vessels with high sensitivity, suggesting a possible means to avoid their laceration during DBS. Other microscopic structures in the human brain with high optical contrast are pathological vacuoles associated with transmissible spongiform encephalopathy (TSE). TSE include diseases such as Mad Cow disease and Creutzfeldt-Jakob disease (CJD) in humans. OCT performed on the brain from a woman who died of CJD was able to detect clearly the pathological vacuoles.