Comparative evaluation of zoomed and parallel diffusion-weighted imaging: A phantom study

Objectives: Single-shot echo-planar imaging sequences with parallel imaging are widely used for diffusion-weighted imaging (DWI). However, when small fields of view and higher phase-encoding reduction ratios (PRs) are applied, image quality may deteriorate because of imperfections in the unfolding process of parallel imaging. Previous studies have suggested that Zoomed DWI (Zoom-DWI) may address this limitation. Therefore, we compared Zoom-DWI with parallel DWI (Parallel-DWI) across different PRs to evaluate image quality. Material and Methods: Zoom-DWI and Parallel-DWI were performed using identical acquisition times and imaging parameters at different PRs. Signal-to-noise ratio (SNR), image uniformity, slice thickness, spatial resolution, and image distortion were evaluated. Results: At a PR of 66.6%, the SNR of Zoom-DWI was approximately 1.4–3.3-fold higher than that of Parallel-DWI at the image center, where reconstruction errors in parallel imaging become more pronounced as PR increases. Image uniformity was also higher in Zoom-DWI than in Parallel-DWI, and the difference increased by approximately 41.0% at a PR of 66.6%. Slice thickness, spatial resolution, and image distortion were comparable between the two methods. Conclusion: In this phantom study, Zoom-DWI demonstrated higher SNR and greater image uniformity than Parallel-DWI, particularly at higher PRs and in the central image region.