# Promise and pitfalls of g-ratio estimation with MRI

## TL;DR

This paper reviews the development, methodology, and challenges of MRI-based g-ratio imaging, highlighting its potential for advancing understanding and diagnosis of neurological health and disease.

## Contribution

It provides a comprehensive overview of the g-ratio MRI imaging technique, including its methodology, limitations, and future prospects.

## Key findings

- MRI g-ratio imaging has potential for in vivo brain studies
- Methodological challenges limit current accuracy
- Future applications could enhance neurological diagnostics

## Abstract

The fiber g-ratio is the ratio of the inner to the outer diameter of the myelin sheath of a myelinated axon. It has a limited dynamic range in healthy white matter, as it is optimized for speed of signal conduction, cellular energetics, and spatial constraints. In vivo imaging of the g-ratio in health and disease would greatly increase our knowledge of the nervous system and our ability to diagnose, monitor, and treat disease. MRI based g-ratio imaging was first conceived in 2011, and expanded to be feasible in full brain with preliminary results in 2013. This manuscript reviews the growing g-ratio imaging literature and speculates on future applications. It details the methodology for imaging the g-ratio with MRI, and describes the known pitfalls and challenges in doing so.