Measurement of water motion (apparent diffusion) in biological systems

This work describes the basics of diffusion measurement in biological systems. The first portion is dedicated to providing an understandable, classical-mechanical description of the Stejskal–Tanner pulse sequence to give the reader an intuitive understanding of the measurement. This is followed by a description of the various aspects of water motion in biological systems that should be taken into account when making and interpreting apparent diffusion coefficient (ADC) measurements. These include free diffusion, restricted diffusion, diffusion anisotropy, population weighting, and the difference between diffusion-weighted imaging (DWI) and ADC maps.