bioRxiv (Cold Spring Harbor Laboratory)
Deciphering the fibre-orientation independent component of R<sub>2</sub>* (R<sub>2,iso</sub>*) in the human brain with a single multi-echo gradient-recalled-echo measurement under varying microstructural conditions
March 2022 • Francisco J. Fritz, Laurin Mordhorst, Mohammad Ashtarayeh, João Periquito, Andreas Pohlmann, Markus Morawski, Carsten Jaeger, Thoralf Niendorf, Kerri…
Abstract The effective transverse relaxation rate (R 2 *) is sensitive to the microstructure of the human brain, e.g. the g-ratio characterising the relative myelination of axons. However, R 2 * depends on the orientation of the fibres relative to the main magnetic field degrading its reproducibility and that of any microstructural derivative measure. To decipher its orientation-independent part (R 2,iso *), a second-order polynomial in time (M2) can be applied to single multi-echo gradient-recalled-echo (meGRE) m…