First Evaluation of External Development Sequences for 7 T Parallel-Transmit MRI in a Self-Built RF Coil

Williams, S. N. , Ding, B., Dragonu, I., Liebig, P. and Porter, D. A. (2022) First Evaluation of External Development Sequences for 7 T Parallel-Transmit MRI in a Self-Built RF Coil. 14th Scottish Imaging Network: A Platform for Scientific Excellence Annual Scientific Meeting (SINAPSE), Glasgow, United Kingdom, 13-14 June 2022.

Abstract

Parallel transmission (pTx) MRI is an increasingly popular tool to overcome the inhomogeneous RF transmit field at ultra-high field (UHF, ≥7 T). However, the use of pTx requires dedicated RF coils and sequences including measurement of subject-specific RF maps and optimization of pulse waveforms. These extra obligations have historically caused the benefits of pTx to be shadowed by cumbersome workflows requiring high levels of expertise. Fortunately, the UHF community has endeavored to find solutions for “push-and-play” pTx MRI in a step towards one-day clinical integration. In this abstract, we report our experience with two such development pTx sequences. In both cases, the pTx protocols were developed for a commercially available pTx coil, and were tested with the 7T setup in Glasgow using a self-built pTx coil of similar design. The first development sequence investigated was the pTx Direct Signal Control with Variable Excitation and Refocusing (DiSCoVER) method for 2D Turbo Spin-Echo (TSE) imaging, developed by colleagues at King’s College London and Siemens Healthcare UK and Germany. DiSCoVER uses the TSE signal model to modify relative amplitudes and phases (shims) in each transmit channel during the TSE pulse train to generate a homogeneous signal. For T2w imaging, we compared DiSCOVER to conventional single transmission and standard volumetric shimming (fixed channel shims for all excitation and refocusing pulses) in the same volunteer. The second development protocol used 3D MPRAGE and MP2RAGE sequences from the Package of Anatomical Sequences using parallel Transmission UniveRsal kT-point pulses (PASTeUR) developed by CEA Neurospin, Paris-Saclay, France. Figure 2 compares T1w images of a second volunteer from MPRAGE and the composite MP2RAGE UNI image using Universal Pulses (UPs) from PASTeUR. In this initial investigation, both development pTx sequences were user-friendly and showed promising results with a few caveats. Further investigation could improve their performance with the Glasgow 7T pTx setup.

• Item Type: Conference or Workshop Item
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Liebig, Patrick and Williams, Dr Sydney and Porter, Professor David and Ding, Ms Belinda
• Authors: Williams, S. N., Ding, B., Dragonu, I., Liebig, P., and Porter, D. A.
• College/School: College of Medical Veterinary and Life Sciences; College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
• Research Group: Imaging Centre of Excellence
• Copyright Holders: Copyright © The Author(s) 2022
• Publisher Policy: Reproduced with the permission of the publisher

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