Fast 3D fMRI acquisition with high spatial resolutions over a reduced FOV

Abstract

AbstractPurposeTo develop and demonstrate a fast 3D fMRI acquisition technique with high spatial resolution over a reduced FOV, named k‐t 3D reduced FOV imaging (3D‐rFOVI).MethodsBased on 3D gradient‐echo EPI, k‐t 3D‐rFOVI used a 2D RF pulse to reduce the FOV in the in‐plane phase‐encoding direction, boosting spatial resolution without increasing echo train length. For image acceleration, full sampling was applied in the central k‐space region along the through‐slab direction (kz) for all time frames, while randomized undersampling was used in outer kz regions at different time frames. Images were acquired at 3T and reconstructed using a method based on partial separability. fMRI detection sensitivity of k‐t 3D‐rFOVI was quantitively analyzed with simulation data. Human visual fMRI experiments were performed to evaluate k‐t 3D‐rFOVI and compare it with a commercial multiband EPI sequence.ResultsThe simulation data showed that k‐t 3D‐rFOVI can detect 100% of fMRI activations with an acceleration factor (R) of 2 and ˜80% with R = 6. In the human fMRI data acquired with 1.5‐mm spatial resolution and 800‐ms volume TR (TRvol), k‐t 3D‐rFOVI with R = 4 detected 46% more activated voxels in the visual cortex than the multiband EPI. Additional fMRI experiments showed that k‐t 3D‐rFOVI can achieve TRvol of 480 ms with R = 6, while reliably detecting visual activation.Conclusionsk‐t 3D‐rFOVI can simultaneously achieve a high spatial resolution (1.5‐mm isotropically) and short TRvol (480‐ms) at 3T. It offers a robust acquisition technique for fast fMRI studies over a focused brain volume.