A fast FLAIR dual‐echo technique for hippocampal T2 relaxometry: First experiences in patients with temporal lobe epilepsy

Abstract

To evaluate the use of cerebrospinal fluid (CSF) signal nulling in MR T2 measurements of the hippocampus in normal control subjects and patients with temporal lobe epilepsy (TLE), dual-echo acquisitions covering the whole brain were used. T2 relaxation times were estimated in 12 standard Eurospin II MR test objects and in the hippocampi of 10 control subjects, using T2 maps constructed from conventional spin-echo (CSE), fast spin-echo (FSE), and fast FLAIR (FF) dual-echo sequences on a 1.5-T MR scanner. Hippocampal T2 values (HCT2) were measured on contiguous coronal 5-mm slices throughout the antero-posterior extent of each hippocampus in the 10 controls and 12 TLE patients, using both CSE and FF. Scan-rescan reproducibility in Eurospin II standard MR test objects was high for all sequences. There was a good correlation between T2 values from CSE, FF, and FSE sequences in test objects and in control hippocampi. In controls, the coefficient of variation of mean HCT2 values differed between slice positions, but was lowest for FF, followed by CSE data. The intrarater coefficient of reliability between repeated measurements in control subjects was lowest for FF HCT2, at 2.3%. The interrater coefficient of reliability for CSE HCT2 measurements in controls (4.8%) was slightly lower than the interrater coefficient for FF HCT2 (5.4%). HCT2 measurement with both CSE and FF identified abnormal values in the same 10 hippocampi of 12 patients. Hippocampal dualecho T2 relaxometry using CSF nulling is reliable in control subjects, and identifies the abnormal hippocampi in patients with TLE. The increases in hippocampal T2 signal demonstrated using FF HCT2 measurements are unlikely to be partial volume effects from CSF. J. Magn. Reson. Imaging 2001;13:547-552.

T 2 : The Transverse Relaxation Time

“…Similar results were obtained by the same group (Woermann et al, 2001), using a CSF-suppressed, fast FLAIR sequence. This sequence has the added bonus that any changes in measured T 2 are not confounded by partial volume contamination from CSF.…”

“…Psychiat. Copyright 1998 BMJ Publishing Group demonstrated in the same number of patients as a nonCSF-nulled sequence, suggesting that parenchymal change, rather than CSF contamination, is the predominant determinant for prolonged HCT2 times in hippocampal sclerosis (Woermann et al, 2001;Figure 6.25). …”

“…Often, changes in T 2 of grey matter (GM) are attributed to CSF contamination and the experimenter needs to be clear that this is not an issue. One way to remove the effects of CSF is to employ a FLAIR sequence, which nulls the CSF signal (Hajnal, et al, 1992;Woermann et al, 2001). …”

Whole-brain T2 mapping demonstrates occult abnormalities in focal epilepsy

“…This latter limitation is, at least partly, overcome by using thin slices and sequences that suppress the signal from CSF, such as fluid-attenuated inversion recovery (FLAIR) imaging. 10 Furthermore, objective voxel-based methods are able to evaluate the whole brain without bias. 5,11,12 Quantitative T2 mapping has previously been applied to cerebral neoplasia, 13 neurodegenerative conditions, 14 ischemia, 15 head injury, 16 encephalitis, 17 and, most frequently, multiple sclerosis (MS), where increased T2 signal has been observed within lesions as well as in cerebral tissue that appeared normal on conventional MRI.…”

Combined MR data acquisition of multicontrast images using variable acquisition parameters and K -space data sharing

“…Multicontrast acquisitions include multiecho 0278-0062/03$17.00 © 2003 IEEE spin echo (SE), dual-contrast gradient-spin echo (GRASE) [27], dual-echo fast fluid-attenuated inversion recovery (fFLAIR) [28], and dual-contrast FSE [29] sequences. The reconstruction of two images of different contrasts from different signal components in a steady-state gradient echo sequence was first reported in [30].…”