MR-IMAGING OF THE HIPPOCAMPUS - MEASUREMENT OF T2 WITH 4 DUAL-ECHO TECHNIQUES

Purpose: To assess the effect of cerebrospinal fluid (CSF) signal null ing and different magnetic resonance (MR) imaging read-out implementat ions on the precision of T2 measurements in the hippocampus. Materials and methods: Oblique coronal MR imaging was performed in 12 healthy v olunteers by using four dual-echo MR sequences: conventional spin-echo (SE), fast SE, gradient-echo and SE (GRASE), and fast fluid-attenuate d inversion-recovery (FLAIR) imaging. T2 measurements were obtained fr om T2 maps derived from regions of interest within the head of both hi ppocampi. T2 measurements obtained with the four MR sequences were com pared, as were differences in T2 between right and left hippocampi. In terrater and test-retest consistency were determined. Results: Fast FL AIR imaging provided the smallest normal range and SD of T2 measuremen ts. 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 rig ht hippocampi was smallest at fast FLAIR imaging. Conclusion: Use of a CSF-nulling inversion prepulse, fast SE read-out, or GRASE read-out M R sequence helps improve the precision of the hippocampal T2 measureme nts in comparison with use of conventional SE imaging. T2 measurements obtained at dual-echo fast FLAIR imaging may help detect subtle hippo campal abnormalities.