Field-cycling imaging yields repeatable brain R dispersion measurement at fields strengths below 0.2 Tesla with optimal fitting routine.

OBJECTIVES

By rapidly changing magnetic field strength between 0.2 and 200 mT during the pulse sequence Field-Cycling Imaging (FCI) makes it possible to identify and evaluate new quantitative markers of pathology derived from dispersion of spin-lattice relaxation rate (R) in vivo. The aim of this work was to determine the most effective approach to reliably estimate multi-field R dispersion measurements in brain tissue using FCI.

MATERIALS AND METHODS

This repeatability study consisted of twenty participants with moderate or severe small vessel disease. Each participant underwent 3 T MRI and FCI scans, repeated 30 days apart. After R maps were generated at 0.2, 2, 20, and 200 mT, co-registered tissue labels generated from 3 T MRI were used to extract tissue averaged values of R dispersion from regions of white matter (WM) and WM hyperintensities (WMHs).

RESULTS

The fitted model which yielded best overall image contrast between WM and WMH regions and R dispersion model adherence was determined. Tissue averaged values of R (0.2 mT) and R dispersion slope exhibited Cohen's d effect sizes of 3.07 and 1.48, respectively, between regions of WM and WMH. The cohort study results were repeatable between study visits.

DISCUSSION

Differences in R measurements could repeatably be discerned between normal and abnormal appearing brain tissues.