Simultaneous multislice imaging (SMS) using parallel image reconstruction has rapidly advanced to become a major imaging technique. The primary benefit is an acceleration in data acquisition that is equal to the number of simultaneously excited slices. Unlike in‐plane parallel imaging this can have only a marginal intrinsic signal‐to‐noise ratio penalty, and the full acceleration is attainable at fixed echo time, as is required for many echo planar imaging applications. Furthermore, for some implementations SMS techniques can reduce radiofrequency (RF) power deposition. In this review the current state of the art of SMS imaging is presented. In the Introduction, a historical overview is given of the history of SMS excitation in MRI. The following section on RF pulses gives both the theoretical background and practical application. The section on encoding and reconstruction shows how the collapsed multislice images can be disentangled by means of the transmitter pulse phase, gradient pulses, and most importantly using multichannel receiver coils. The relationship between classic parallel imaging techniques and SMS reconstruction methods is explored. The subsequent section describes the practical implementation, including the acquisition of reference data, and slice cross‐talk. Published applications of SMS imaging are then reviewed, and the article concludes with an outlook and perspective of SMS imaging. Magn Reson Med 75:63–81, 2016. © 2015 The Authors. Magnetic Resonance in Medicine Published by Wiley Periodicals, Inc. on behalf of International Society of Medicine in Resonance.

Functional MRI (fMRI) generally employs gradient‐echo echo‐planar imaging (GE‐EPI) to measure blood oxygen level‐dependent (BOLD) signal changes that result from changes in tissue relaxation time T between activation and rest. Since T strongly varies across the brain and BOLD contrast is maximal only where the echo time (TE) equals the local T, imaging at a single TE is a compromise in terms of overall sensitivity. Furthermore, the long echo train makes EPI very sensitive to main field inhomogeneities, causing strong image distortion. A method is presented that uses accelerated parallel imaging to reduce image artifacts and acquire images at multiple TEs following a single excitation, with no need to increase TR. Sensitivity gains from the broadened T coverage are optimized by pixelwise weighted echo summation based on local T or contrast‐to‐noise ratio (CNR) measurements. The method was evaluated using an approach that allows differential BOLD CNR to be calculated without stimulation, as well as with a Stroop experiment. Results obtained at 3 T showed that BOLD sensitivity improved by 11% or more in all brain regions, with larger gains in areas typically affected by strong susceptibility artifacts. The use of parallel imaging markedly reduces image distortion, and hence the method should find widespread application in functional brain imaging. Magn Reson Med, 2006.

Purpose MRI methods sensitive to functional changes in cerebral blood volume (CBV) may map neural activity with better spatial specificity than standard functional MRI (fMRI) methods based on blood oxygen level dependent (BOLD) effect. The purpose of this study was to develop and investigate a vascular space occupancy (VASO) method with high sensitivity to CBV changes for use in human brain at 7 Tesla (T). Methods To apply 7T VASO, several high-field-specific obstacles must be overcome, e.g., low contrast-to-noise ratio (CNR) due to convergence of blood and tissue T₁, increased functional BOLD signal change contamination, and radiofrequency field inhomogeneities. In the present method, CNR was increased by keeping stationary tissue magnetization in a steady-state different from flowing blood, using slice-selective saturation pulses. Interleaved acquisition of BOLD and VASO signals allowed correction for BOLD contamination. Results During visual stimulation, a relative CBV change of 28% ± 5% was measured, confined to gray matter in the occipital lobe with high sensitivity. Conclusion By carefully considering all the challenges of high-field VASO and filling behavior of the relevant vasculature, the proposed method can detect and quantify CBV changes with high CNR in human brain at 7T. Magn Reson Med 72:137–148, 2014.