3D Double Inversion Recovery for High Resolution Gray Matter Brain Imaging

Gray matter (GM) images with high spatial resolution are obtained at 1.5T with a new multislab 3D double inversion recovery sequence that selectively suppresses cerebrospinal fluid (CSF) and white matter (WM). Images show a clear delineation of GM from WM and CSF, also for small GM structures such as the entorhinal cortex, of importance in Alzheimer's disease. Feasibility is demonstrated for the distinction between cortical and WM lesions in a patient with multiple sclerosis (MS). Introduction Selective gray matter imaging with double inversion recovery (DIR) is based on nulling of both CSF and WM using a long and short inversion time TIi,,l, and TIsl,ort, respectively [ 1,2]. Current DIR techniques are performed in 2D multislice mode, but 3D methods allow imaging at a higher spatial resolution. For instance, it has been shown that 3D fluid attenuated inversion recovery (FLAIR) imaging is more sensitive than 2D for small lesions in patients with MS [3] and for small GM and WM structures in general [4]. Another application of high resolution GM imaging might be volume determination of small GM structures such as hippocampus and entorhinal cortex that are affected early in Alzheimer's disease. The aim of this study was to develop a 3D DIR by inserting a second inversion pulse in 3D multislab FLAIR [3,5] and to acquire high resolution GM images of the brain. Methods The 3D DIR turbo-spin-echo was developed on a 1 S T Siemens Sonata MR scanner. ETL 27, BW 167 Hzipixel, echo spacing 9.7, TEee 97, TR 71 00, TIs~,,fi 330, TII,,~, 2480. In transverse orientation whole brain coverage was obtained with 2 interleaved sets, each containing 4 slabs. Spatial resolution was 1.2x1.2x1.8 (160x256 matrix, FOV 3 10 mm, slab thickness 18 mm, divided into 10 slices, with 60% oversampling in slice select direction). In addition, fat saturation and an iiiferior saturation slab to reduce flow artifacts were applied. Scan time was 1 1.5 min for 1 set of 4 slabs. The sequence was optimized with regard to TR and TI on healthy young volunteers, resulting in the abovementioned parameters. Initial experience was obtained with a patient with MS.