English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The g-ratio, quantifying the comparative thickness of the myelin sheathencasing an axon, is a geometrical invariant that has high functional relevancebecause of its importance in determining neuronal conduction velocity. Advancesin MRI data acquisition and signal modelling have put in vivo mapping of theg-ratio, across the entire white matter, within our reach. This capacity wouldgreatly increase our knowledge of the nervous system: how it functions, and howit is impacted by disease. This is the second review on the topic of g-ratiomapping using MRI. As such, it summarizes the most recent developments in thefield, while also providing methodological background pertinent to aggregateg-ratio weighted mapping, and discussing pitfalls associated with theseapproaches. Using simulations based on recently published data, this reviewdemonstrates the relevance of the calibration step for three myelin-markers(macromolecular tissue volume, myelin water fraction, and bound pool fraction).It highlights the need to estimate both the slope and offset of therelationship between these MRI-based markers and the true myelin volumefraction if we are really to achieve the goal of precise, high sensitivityg-ratio mapping in vivo. Other challenges discussed in this review furtherevidence the need for gold standard measurements of human brain tissue from exvivo histology. We conclude that the quest to find the most appropriate MRIbiomarkers to enable in vivo g-ratio mapping is ongoing, with the potential ofmany novel techniques yet to be investigated.

Towards in vivo g-ratio mapping using MRI: unifying myelin and diffusion imaging