Simultaneous multislice (SMS) imaging techniques

Abstract

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.

Denoising spinal cord fMRI data: Approaches to acquisition and analysis

“…These multi-echo functional imaging techniques (Kundu et al, 2012) have shown great promise for improving the quality of fMRI data acquired from the brain, but have yet to be exploited for imaging the spinal cord. One might also use simultaneous multi-slice (or "multi-band") EPI, which allows a shortening of the TR due to the simultaneous excitation of several slices (Barth et al, 2016; interestingly, this approach has recently been combined with a multi-echo technique: Boyacioğlu et al, 2015); this approach requires a certain coil geometry, but would potentially allow one to critically sample cardiac and respiratory artefacts and thus remove them based on frequency spectra (which is not possible with standard TRs due to the aliasing that occurs). An alternative approach to improving the specificity of spinal cord fMRI is to reduce voxel sizes, which has been shown to reduce the influence of physiological noise (Hutton et al, 2011).…”

High‐resolution gradient‐recalled echo imaging at 9.4T using 16‐channel parallel transmit simultaneous multislice spokes excitations with slice‐by‐slice flip angle homogenization

“…The application of SMS is also rapidly extending to the clinical domain for anatomical T 2 ‐ and ${\mathrm{normalT}}_2^{*}$‐weighted imaging and below the neck. [For a review of technique and applications, see Barth et al 40 and Setsompop et al 41]. SMS is particularly attractive for high‐resolution 2D multislice imaging, which is time‐consuming due to the high number of phase‐encoding lines and slices that need to be acquired.…”

Safety of Simultaneous Scalp or Intracranial EEG during MRI: A Review

“…Therefore the distribution and amount of tissue heating with or without any conductive components placed in or near the RF coil is greatly affected by the coil size and design. For example, SAR values can be decreased by careful transmit coil design [62][63][64][65][66][67][68]. Kangarlu and co-workers performed simulations and experiments to study the impact of coil length on localized heating at 8T, showing greater heating for longer coils [69].…”