Zhongping Chen, Thomas E. Milner, Shyam Srinivas, and J. Stuart Nelson, Beckman Laser Institute and Medical Clinic, Univ. of California at Irvine.
Direct visualization of physiological processes provides important information to the clinician for the diagnosis and treatment of disease. High spatial resolution noninvasive techniques for imaging in vivo blood flow dynamics and tissue structure are currently not available as a diagnostic tool in clinical medicine. Such techniques could have a significant impact for biomedical research and clinical diagnostics. Techniques such as Doppler ultrasound and laser Doppler flowmetry (LDF) are currently used in medical diagnostics for blood flow velocity determination. Doppler ultrasound uses the principle that the frequency of ultrasonic waves backscattered by moving particles are Doppler shifted. However, the relatively long acoustic wavelengths required for deep tissue penetration limits the spatial resolution to approximately 200 μm. Although LDF has been used to measure mean blood perfusion in the peripheral microcirculation, strong optical scattering in biological tissue limits spatially resolved flow measurements by LDF.
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