  Diffusion-encoded magnetic resonance (MR) experiments can provide important
insights into the microstructural characteristics of a variety of biological
tissues and other fluid- or gas-filled porous media. The physics of diffusion
encoding has been studied extensively over the span of many decades, and many
excellent descriptions can be found in the literature -- see, e.g., Refs.
[1-5]. However, many of these descriptions spend relatively little time
focusing on random process descriptions of the diffusion process, instead
relying on different abstractions. In this primer, we describe
diffusion-encoded MR experiments from a random process perspective. While the
results we derive from this perspective are quite standard (and match the
results obtained with other arguments), we expect that the alternative
derivations may be insightful for some readers. This primer is intended for
technical readers who have a graduate-level understanding of random processes.
Readers are also expected to already have good familiarity with the basics of
MR, and we anticipate that a signal processing perspective on MR [6] will be
especially complementary to the random process perspectives presented herein.
