Three‐dimensional reduced field‐of‐view imaging (3D‐rFOVI)

Abstract Purpose This study aimed at developing a 3D reduced field‐of‐view imaging (3D‐rFOVI) technique using a 2D radiofrequency (RF) pulse, and demonstrating its ability to achieve isotropic high spatial resolution and reduced image distortion in echo planar imaging (EPI). Methods The proposed 3D‐rFOVI technique takes advantage of a 2D RF pulse to excite a slab along the conventional slice‐selection direction (i.e., z ‐direction) while limiting the spatial extent along the phase‐encoded direction (i.e., y ‐direction) within the slab. The slab is phase‐encoded in both through‐slab and in‐slab phase‐encoded directions. The 3D‐rFOVI technique was implemented at 3T in gradient‐echo and spin‐echo EPI pulse sequences for functional MRI (fMRI) and diffusion‐weighted imaging (DWI), respectively. 3D‐rFOVI experiments were performed on a phantom and human brain to illustrate image distortion reduction, as well as isotropic high spatial resolution, in comparison with 3D full‐FOV imaging. Results In both the phantom and the human brain, image voxel dislocation was substantially reduced by 3D‐rFOVI when compared with full‐FOV imaging. In the fMRI experiment with visual stimulation, 3D isotropic spatial resolution of (2 × 2 × 2 mm 3 ) was achieved with an adequate signal‐to‐noise ratio (81.5) and blood oxygen level‐dependent (BOLD) contrast (2.5%). In the DWI experiment, diffusion‐weighted brain images with an isotropic resolution of (1 × 1 × 1 mm 3 ) was obtained without appreciable image distortion. Conclusion This study indicates that 3D‐rFOVI is a viable approach to 3D neuroimaging over a zoomed region.