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PINS RF pulses combined with multiband imaging reduce SAR sufficiently to enable routine TSE imaging at 7T within clinically acceptable acquisition times. In general, the combination of multiband imaging with PINS RF pulses represents a method to reduce total RF power deposition.

A whole brain, multiband spin-echo (SE) echo planar imaging (EPI) sequence employing a high spatial (1.5 mm isotropic) and temporal (TR of 2 s) resolution was implemented at 7 Tesla. Its overall performance (tSNR, sensitivity and CNR) was assessed and compared to a geometrically matched gradient-echo (GE) EPI multiband sequence (TR of 1.4 s) using a colour-word Stroop task. PINS RF pulses were used for refocusing to reduce RF amplitude requirements and SAR, summed and phaseoptimized standard pulses were used for excitation enabling a transverse or oblique slice orientation. The distortions were minimized with the use of parallel imaging in the phase encoding direction and a post-acquisition distortion correction. In general, GE-EPI shows higher efficiency and higher CNR in most brain areas except in some parts of the visual cortex and superior frontal pole at both the group and individual-subject levels. Gradient-echo EPI was able to detect robust activation near the air/tissue interfaces such as the orbito-frontal and subcortical regions due to reduced intra-voxel dephasing because of the thin slices used and high in-plane resolution.

Purpose To obtain whole‐brain high‐resolution T2 maps in 2 minutes by combining simultaneous multislice excitation and low‐power PINS (power independent of number of slices) refocusing pulses with undersampling and a model‐based reconstruction. Methods A multi‐echo spin‐echo sequence was modified to acquire multiple slices simultaneously, ensuring low specific absorption rate requirements. In addition, the acquisition was undersampled to achieve further acceleration. Data were reconstructed by subsequently applying parallel imaging to separate signals from different slices, and a model‐based reconstruction to estimate quantitative T2 from the undersampled data. The signal model used is based on extended phase graph simulations that also account for nonideal slice profiles and B1 inhomogeneity. In vivo experiments with 3 healthy subjects were performed to compare accelerated T2 maps to fully sampled single‐slice acquisitions. The accuracy of the T2 values was assessed with phantom experiments by comparing the T2 values to single‐echo spin‐echo measurements. Results In vivo results showed that conventional multi‐echo spin‐echo, simultaneous multislice, and undersampling result in similar mean T2 values within regions of interest. However, combining simultaneous multislice and undersampling results in higher SDs (about 7 ms) in comparison to a conventional sequence (about 3 ms). The T2 values were reproducible between scan and rescan (SD < 1.2 ms) within subjects and were in similar ranges across subjects (SD < 4.5 ms). Conclusion The proposed method is a fast T2 mapping technique that enables whole‐brain acquisitions at 0.7‐mm in‐plane resolution, 3‐mm slice thickness, and low specific absorption rate in 2 minutes.

MB-MS 3D-TOF-MRA can appreciably accelerate image acquisition and combines the high spatial resolution of 3D imaging with the additional inflow contrast advantage of thinner slab acquisitions without introducing excessive noise arising from the MB reconstruction.