Isotropic 3D fast FLAIR imaging of the brain in multiple sclerosis patients: initial experience

Abstract

The application of image registration and subtraction to detect change in multiple sclerosis (MS) disease burden on serial MR scans benefits from the use of isotropic voxels. An optimised 3D fast fluid-attenuated inversion recovery (FLAIR) sequence with 1.2- and 1.8-mm cubic voxels was compared with a 2D T2 SE sequence using standard 3-mm slices. Three-dimensional fast FLAIR and T2 SE series were obtained in 20 MS patients and 15 controls. Whole brain acquisition times for the 1.2- and 1.8-mm FLAIR were 21 and 10.5 min, respectively, for the interleaved T2 SE 16 min. Brain lesions were marked in consensus by two radiologists and the CNR was calculated in ten lesions. The mean number of lesions detected with the 1.2-mm FLAIR sequence was 115 +/- 76, compared with 85 +/- 59 for the T2 SE series ( p<0.001). The 1.8-mm FLAIR detected only 73 +/- 46 lesions. The CNR of the 1.2-mm FLAIR was significantly better than the T2 SE ( p<0.01), but not as good as the 1.8-mm FLAIR. In conclusion, isotropic 3D fast FLAIR using 1.2-mm cubic voxels is superior to the 2D T2 SE in the detection of brain lesions in MS patients. The isotropic 1.8-mm FLAIR is faster and has better contrast characteristics but lacks sensitivity.

Multi-contrast, isotropic, single-slab 3D MR imaging in multiple sclerosis

“…Small caps around the ventricles (Fig. 1) were also frequently seen, as described previously, for multi-slab 3D sequences [13,14]. On the 3D-MPRAGE images vascular structures were recognizable as circular areas of low signal intensity in and around the cortex.…”

“…A conducive factor is the decrease in slice thickness, which is strongly associated with increased lesion detection [26,27]. Several authors have previously reported increased detection of WM lesions using 3D multi-slab FLAIR sequences [12,13,26]. In our study, the highest number of WM lesions was Fig.…”

“…Delta arrows point out a mixed WM-GM matter lesion that invades the cortical mantle. Arrowheads point out an intracortical lesion clearly seen on 3D-DIR and to a lesser extent on the other images 3D-DIR and 3D-FLAIR images, which is in contrast with previously reported decreased detection in the posterior cranial fossa [10,12,13]. As stated above, this is related to the absence of blood and CSF flow artifacts in the 3D sequences, especially in the posterior cranial fossa (Fig.…”

“…Regarding the improvement of spatial resolution, three-dimensional (3D) MRI allows for the acquisition of smaller (isotropic) voxels while maintaining a good signal-to-noise ratio (SNR). Initially, FLAIR and DIR could only be implemented as multi-slab 3D sequences; nevertheless, FLAIR demonstrated an improved detection of WM lesions [12,13], and DIR showed an improved detection and classification of cortical lesions [14], all compared to 2D-T2SE. A recent paper showed that, aside from with DIR, cortical lesions could also be visualized employing a 3D T1-weighted sequence [15].…”

Comparison of 3D Cube FLAIR with 2D FLAIR for Multiple Sclerosis Imaging at 3 Tesla

“…Early studies on 3 D FLAIR described the feasibility of these sequences as well as their superiority in the detection of MS lesions compared to 2 D sequences [14,15]. In the beginning, however, 3 D sequences were acquired in a multi-slab mode which had several disadvantages including the occurrence of so-called venetian blind effects and long acquisition times.…”