MR imaging of the hippocampus: measurement of T2 with four dual-echo techniques.

Abstract

To assess the effect of cerebrospinal fluid (CSF) signal nulling and different magnetic resonance (MR) imaging read-out implementations on the precision of T2 measurements in the hippocampus. Oblique coronal MR imaging was performed in 12 healthy volunteers by using four dual-echo MR sequences: conventional spin-echo (SE), fast SE, gradient-echo and SE (GRASE), and fast fluid-attenuated inversion-recovery (FLAIR) imaging. T2 measurements were obtained from T2 maps derived from regions of interest within the head of both hippocampi. T2 measurements obtained with the four MR sequences were compared, as were differences in T2 between right and left hippocampi. Interrater and test-retest consistency were determined. Fast FLAIR imaging provided the smallest normal range and SD of T2 measurements. Fast FLAIR and fast SE imaging provided the smallest coefficients of variation. GRASE imaging provided a lower coefficient of variation than that of conventional SE. The mean difference between left and right hippocampi was smallest at fast FLAIR imaging. Use of a CSF-nulling inversion prepulse, fast SE read-out, or GRASE read-out MR sequence helps improve the precision of the hippocampal T2 measurements in comparison with use of conventional SE imaging. T2 measurements obtained at dual-echo fast FLAIR imaging may help detect subtle hippocampal abnormalities.