There are different techniques to measure the flow of blood in human body. Some of techniques are Magnetic Resonance Imaging, laser based techniques such as laser Doppler and laser speckle, Doppler Ultrasound technique and Positron Emission tomography (PET).
Magnetic Resonance test is carried on a slice of tissue; RF pulse is applied on tissue. This is divided in equal and opposite bipolar gradients. The protons experiences phase shift. This shift is observed and flow of blood is measured. In laser technique, light projected on skin irradiate, affects blood flow. Doppler affect causes frequency shift, moves red blood cells. Doppler frequency is measured and this detects status of blood flow in human body. PET is non-invasive image technique, this supports in extracting in-vivo cross images of body. In this a labelled compound is injected to human body, after certain time concentration of tracer is measured through scanner.