TRITONE: a Radio-Frequency Field (B1) Insensitive T1 Estimator for MRI at High Magnetic Fields.

摘要

Fast, high resolution, longitudinal relaxation time (T1) mapping is invaluable in clinical and research applications. It has been shown that two spoiled gradient recalled echo (SPGR) images acquired in steady state with variable flip angles is an attractive alternative to the multi-image sets previously acquired with inversion or saturation recovery. The known sensitivity of the two-point method to transmit radio-frequency field (B1) inhomogeneity exacerbated at 3 Tesla and above, however, mandates its combination with an additional, time consuming and possibly SAR intensive B1 measurement, preventing direct migration of the method to these fields. To address this we introduce a method designed to be free of systematic errors caused by B1 inhomogeneity in which the value of T1 is extracted from three SPGR images acquired with EPI readout. The precision of the T1 maps produced is found to be comparable to the two-point method while the accuracy is greatly improved in the same time and spatial resolution. A welcome byproduct of the method is a map of B1 that can be used to correct other acquisitions in the same session. Tables of the optimal acquisition protocols are provided for several total imaging times.