Blood flow measurements
Laser Doppler Flowmetry (LDF) is a non invasive method to measure the microcirculatory blood flow based on the fact that a very small frequency shift arises in light that has been scattered by moving red blood cells, known as the Doppler effect.
Main content
In other words, by illuminating a tissue sample with single-frequency light (monochromatic) and processing the frequency distribution of the backscattered light an estimate of the blood perfusion can be achieved. LDF technique can yet not measure absolute perfusion but can have excellent temporal resolution and therefore measure blood flow changes in the tissues. Practically, the tissue of interest should be immobilised and a probe connected to a laser Doppler flowmeter (780 nm, near-infrared laser) is placed on or very close to the tissue (Link to http://www.imt.liu.se/bit/ldf/ldfmain.htm).