Microstructure with Diffusion MRI: What Scale We Are Sensitive to?

TL;DR

This review discusses the spatial and temporal scales of tissue microstructure detectable by various diffusion MRI techniques, emphasizing the balance between measurement sensitivity and interpretability.

Contribution

It provides a classification of diffusion phenomena and models in different measurement spaces, highlighting how advanced diffusion weighting techniques can target specific cellular geometries.

Findings

Diffusion MRI can probe different microstructural scales depending on measurement parameters.

Modern diffusion techniques incorporate multiple parameters to better match tissue geometries.

Understanding the measurement space helps optimize microstructural imaging accuracy.

Abstract

Diffusion-weighted MRI is the forerunner of the rapidly developed microstructural MRI aimed at in vivo evaluation of the cellular tissue architecture. This brief review focuses on the spatiotemporal scales of the microstructure that are accessible using different diffusion MRI techniques and the need to weight the measurability against the interpretability of results. Diffusion phenomena and models are first classified in two-dimensional space (the q-t-plane) of the measurement with narrow gradient pulses. Three-dimensional parameter space of the Stejskal--Tanner diffusion weighting adds more phenomena to this collection. Modern measurement techniques with larger number of parameters are briefly discussed under the overarching idea of diffusion weighting matching the geometry of the targeted cell species.