# Mapping microglia and astrocyte activation in vivo using diffusion MRI

## TL;DR

This paper introduces a noninvasive MRI method to detect brain inflammation by imaging microglia and astrocyte activation in living organisms.

## Contribution

A novel noninvasive diffusion MRI technique is developed to quantify glial activation and neuroinflammation in vivo.

## Key findings

- Diffusion-weighted MRI captures distinct fingerprints of microglia and astrocyte activation in rat models.
- The method is sensitive to glial morphology and proliferation changes, independent of neuronal loss or demyelination.
- Significant associations between MRI and histological markers in humans confirm the method's translational potential.

## Abstract

While glia are increasingly implicated in the pathophysiology of psychiatric and neurodegenerative disorders, available methods for imaging these cells in vivo involve either invasive procedures or positron emission tomography radiotracers, which afford low resolution and specificity. Here, we present a noninvasive diffusion-weighted magnetic resonance imaging (MRI) method to image changes in glia morphology. Using rat models of neuroinflammation, degeneration, and demyelination, we demonstrate that diffusion-weighted MRI carries a fingerprint of microglia and astrocyte activation and that specific signatures from each population can be quantified noninvasively. The method is sensitive to changes in glia morphology and proliferation, providing a quantitative account of neuroinflammation, regardless of the existence of a concomitant neuronal loss or demyelinating injury. We prove the translational value of the approach showing significant associations between MRI and histological microglia markers in humans. This framework holds the potential to transform basic and clinical research by clarifying the role of inflammation in health and disease.

Diffusion-weighted MRI carries the fingerprint of glia activation and can image brain inflammation in vivo and noninvasively.