# Myelin water fraction mapping with joint inversion of gradient-echo and spin-echo data

## TL;DR

A new method combines gradient-echo and spin-echo data to improve the accuracy of myelin-water imaging in the brain.

## Contribution

A novel joint inversion method that enhances myelin-water estimation by combining gradient-echo and spin-echo data.

## Key findings

- Joint inversion of gradient-echo and spin-echo data improves simulation accuracy of myelin-water imaging.
- In vivo experiments show sharper and more distinct myelin-water images with joint inversion.
- The method improves reliability by addressing the ill-posed inversion problem using complementary data.

## Abstract

Accurate estimation of brain myelin-water content from multi-echo data is challenging due to the inherent ill-posedness of the inversion problem. In this study, we propose a novel method for myelin-water imaging that jointly utilizes gradient-echo and spin-echo imaging data to enhance the accuracy of myelin-water estimation.

Multi-echo gradient-echo and spin-echo data were simulated and acquired in vivo. The simulations are based on a parameterized myelin and free water signal model, which is also used for the inversion by means of nonlinear local-search optimization. Single inversions of the individual datasets as well as joint inversion of the combined datasets were performed on simulated and real data. While single inversions estimate either the \documentclass[12pt]{minimal}
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Simulation results show that the accuracy of myelin-water imaging improves when jointly inverting gradient-echo and spin-echo synthetic data. In vivo experiments show that the joint inversion of both datasets leads to sharper and more distinct myelin-water images as compared to the individual inversions.

Our method addresses the ill-posed nature of the myelin-water inversion problem by leveraging complementary information from multi-echo gradient-echo and multi-echo spin-echo imaging sequences, thus improving the reliability of myelin-water quantification.

The online version contains supplementary material available at 10.1007/s10334-025-01235-5.