iShim and Water Excitation Improves the Signal-to-Noise Ratio on q-Space Imaging: A Single-Center Clinical Study

Abstract

Purpose: This study aimed to examine whether the signal-to-noise ratio (SNR) could be increased by combining integrated slice-by-slice shimming (iShim) with a fat suppression (FS) method other than short-tau inversion recovery (STIR) in diffusion-weighted imaging (DWI) and q-space imaging (qsi). Methods: We acquired DWI images (b-values: 0 and nine steps from 400 to 10,000 s/mm 2 for six axes) using a prototypical single-shot echo planar imaging sequence by combining two types of shimming (3D Shim and iShim) and two types of FS (STIR and water excitation [WE]) in 10 volunteers. In the DWI study, the SNR for each b-value, FS effect in the b0 image, and distortion in the added image (b0-b10,000) were evaluated for the above-mentioned four imaging methods. qsi involved original DWI images. In the qsi study, the SNR was evaluated. Results: With regard to both 3D Shim and iShim, the SNRs were significantly higher when using WE than when using STIR in b0-b900 images (p < 0.01). For 3D Shim, however, the SNR increase effect of WE disappeared (p < 0.01) at b1600 or higher. For iShim, the SNR increase effect of WE was maintained up to b3600 (p < 0.01). The FS effect of STIR was superior to that of WE (p < 0.01). Although WE had a weak FS effect, its FS effect was greater with iShim than with 3D Shim (p < 0.01). In added images, with iShim, the spinal cord area became significantly smaller (p < 0.

Detecting Mild Lower-limb Skeletal Muscle Fatigue with Stimulated-echo q-space Imaging

“…1 In qsi, which uses more data than standard DWI, the restricted space is examined indirectly from the distribution of the measured water molecule displacement. [2][3][4] This approach enables the determination of subtle structural changes and the generation of information distinct from the apparent diffusion coefficient and FA.…”