Rapid high spatial resolution diffusion MRI at 7 Tesla using simultaneous multislice acquisition

摘要

Diffusion weighted MRI (dMRI) data with very high spatial resolution can be obtained using ultra high magnetic field strength MRI such as 7 Tesla(T). However, for extensive brain coverage a large number of imaging slices are required, which can result in long acquisition times (TA). Simultaneous Multi-Slice (SMS) acquisition technology enables increased temporal efficiency of MRI to permit rapid acquisition of dMRI. However, Multiband (MB) RF-pulses used for SMS acquisition can cause large energy deposition into the subject and limit the rate at which data can be acquired. Power Independent of Number of Slices (PINS) pulses can be used instead of MB pulse to reduce RF-power. However, this comes at a cost of reduced bandwidth and increased off-resonance dependency, which degrades image quality. We proposed a new RF pulse design, MultiPINS, by combining MB with PINS RF pulses to further decrease RF energy and/or shorten pulse lengths. Employing SMS technology and PINS/MultiPINS pulses, in-vivo dMRI results were recorded at high spatial resolutions at 7 T. The data shows that this method enables a 3-fold scan time reduction while preserving image quality.