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TitleIs there a difference between laser speckle and laser Doppler in depth sensitivity?
Publication TypeConference Paper
Year of Publication2011
AuthorsThompson, O.B., Hirst E.R., and Andrews M.K.
Conference NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
Date Published2011
KeywordsClassifiers, Depth sensitivity, Detectors, Doppler effect, Effective distance, Field imaging, Histology, Laser doppler, Laser Doppler systems, Laser speckle, Laser speckle contrast, Measurements, Modulated imaging, Optical properties, Optical set-up, Perfusion measurements, Phantom measurements, Physical phenomena, Point illumination, Probe-based, Scanning lasers, Speckle, Tissue
AbstractLaser speckle and laser Doppler perfusion measurements apply different analyses to the same physical phenomenon and so should produce the same results. However, there is some evidence that laser Doppler can measure perfusion at greater depths than laser speckle. Using phantom measurements and comparison to spatially modulated imaging, we show why this might be the case. Various implementations of imaging laser Doppler and speckle systems have different optical setups, producing different effective distances between the illumination and detector points on the surface of the tissue. Separating the effective source and detector regions in tissue measurements biases the measurements towards deeper tissues, and when the effective source and detector regions coincide, the measurement is biased towards surface tissues. Probe-based or scanning laser Doppler systems with point illumination can separate the source and detector regions to interrogate deeper tissues, while whole-field imaging laser Doppler systems and laser speckle contrast systems have broad illumination covering the measurement areas. The volume of tissue informing a measurement at any point in a whole-field system, and hence the depth sensitivity, is determined by the optical properties of the tissue at the working wavelength.

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