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Compared with other existing imaging technologies, laser speckle contrast imaging has several obvious advantages. It can uses simple and cost-effective instrument to return excellent spatial and temporal resolution imaging. And due to these strengths, laser speckle contrast imaging has been involved in mapping blood flow for decades.
Therefore, there is an urgent need for a way to measure blood flow. However, blood flow is difficult to measure because of sensitivity and stability of the measurement as it depends on magnitude of flow, location, and the diameter of individual vessels. [2] Current imaging modalities used to measure blood flow include Doppler ultrasound, PET ...
Laser Doppler imaging (LDI) is an imaging method that uses a laser beam to image live tissue. When the laser light reaches the tissue, the moving blood cells generate Doppler components in the reflected (backscattered) light. The light that comes back is detected using a photodiode that converts it into an electrical signal.
Laser Doppler velocimetry is used in hemodynamics research as a technique to partially quantify blood flow in human tissues such as skin or the eye fundus. Within the clinical environment, the technology is often referred to as laser Doppler flowmetry; when images are made, it is referred to as laser Doppler imaging.
The photoacoustic Doppler effect is a type of Doppler effect that occurs when an intensity modulated light wave induces a photoacoustic wave on moving particles with a specific frequency. The observed frequency shift is a good indicator of the velocity of the illuminated moving particles. A potential biomedical application is measuring blood flow.
Initial efforts to measure blood flow using OCT utilized the Doppler effect. [41] [42] By comparing the phase of successive A-mode scans, the velocity of blood flow can be determined via the Doppler equation. This was deemed Optical Doppler Tomography; the development of spectral domain OCT (SD-OCT) and swept-source OCT (SS-OCT) greatly ...
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SV-OCT uses the inter-frame variance of image intensities to compute blood flow. Areas that have high flow will have higher motion of scattering particles and this information is encoded in the speckle pattern. [citation needed] SV-OCT has advantages for microvasculature imaging due to its high sensitivity and independence to the Doppler angle.
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