Quantification of the in vivo brain ultrashort-T2* component in healthy volunteers

Abstract

Purpose: Recent work has shown MRI is able to measure and quantify signals of phospholipid membrane-bound protons associated with myelin in the human brain. This work seeks to develop an improved technique for characterizing this brain ultrashort- (Formula presented.) component in vivo accounting for (Formula presented.) weighting. Methods: Data from ultrashort echo time scans from 16 healthy volunteers with variable flip angles (VFA) were collected and fitted into an advanced regression model to quantify signal fraction, relaxation time, and frequency shift of the ultrashort- (Formula presented.) component. Results: The fitted components show intra-subject differences of different white matter structures and significantly elevated ultrashort- (Formula presented.) signal fraction in the corticospinal tracts measured at 0.09 versus 0.06 in other white matter structures and significantly elevated ultrashort- (Formula presented.) frequency shift in the body of the corpus callosum at (Formula presented.) 1.5 versus (Formula presented.) 2.0 ppm in other white matter structures. Conclusion: The significantly different measured components and measured (Formula presented.) relaxation time of the ultrashort- (Formula presented.) component suggest that this method is picking up novel signals from phospholipid membrane-bound protons.