Robust Estimation of Changes in Transverse Relaxation from Magnitude MRI Data: Application to Vessel Size Imaging

Simon Walker-Samuel¹, Matthew Orton¹, Lesley D. McPhail¹, Simon P. Robinson¹

Vessel size imaging using USPIO contrast agents has recently been utilised in a range of contexts, but has been reported to suffer from over-estimation of vessel size index (VSI). In this study, a novel Bayesian maximum a posteriori (MAP) approach is presented for estimating R2 and R2* and ADC. This is compared with a conventional approach (least-squares, LS). By conditioning data with the removal of parameter estimates with high uncertainties or non-significant enhancement, VSI was estimated at 8329m by LS and 6325m by MAP (difference significant, p<0.01), compared with 676m from histological measurements.