Journal Article Research Support, Non-U.S. Gov't Ppublish 10 citations
PubMed: 37794847 DOI: 10.1002/mrm.29845
Head-and-neck multichannel B1 mapping and RF shimming of the carotid arteries using a 7T parallel-transmit head coil.
Magn Reson Med 91(1):190-204
Authors: Matthijs H S de Buck, James L Kent, Peter Jezzard, Aaron T Hess
Affiliations
- FMRIB Division, Nuffield Department of Clinical Neurosciences, Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, UK.
Abstract
PURPOSE
Neurovascular MRI suffers from a rapid drop in B into the neck when using transmit head coils at 7 T. One solution to improving B magnitude in the major feeding arteries in the neck is to use custom RF shims on parallel-transmit head coils. However, calculating such shims requires robust multichannel B maps in both the head and the neck, which is challenging due to low RF penetration into the neck, limited dynamic range of multichannel B mapping techniques, and B sensitivity. We therefore sought a robust, large-dynamic-range, parallel-transmit field mapping protocol and tested whether RF shimming can improve carotid artery B magnitude in practice.
METHODS
A pipeline is presented that combines B mapping data acquired using circularly polarized (CP) and CP2-mode RF shims at multiple voltages. The pipeline was evaluated by comparing the predicted and measured B for multiple random transmit shims, and by assessing the ability of RF shimming to increase B in the carotid arteries.
RESULTS
The proposed method achieved good agreement between predicted and measured B in both the head and the neck. The B magnitude in the carotid arteries can be increased by 43% using tailored RF shims or by 37% using universal RF shims, while also improving the RF homogeneity compared with CP mode.
CONCLUSION
B in the neck can be increased using RF shims calculated from multichannel B maps in both the head and the neck. This can be achieved using universal phase-only RF shims, facilitating easy implementation in existing sequences.
MeSH
Carotid Arteries, Arteries
Cited by
- An 8Tx/32Rx head-neck coil at 7T by combining 2Tx/32Rx Nova coil with 6Tx shielded coaxial cable elements. Magn Reson Med, 2024
- Simultaneous whole-brain and cervical spine imaging at 7 T using a neurovascular head and neck coil with 8-channel transceiver array and 56-channel receiver array. Magn Reson Med, 2025
- Dynamic B field shimming for improving pseudo-continuous arterial spin labeling at 7 T. Magn Reson Med, 2025
- Head-and-neck multichannel B1 mapping and RF shimming of the carotid arteries using a 7T parallel-transmit head coil. Magn Reson Med, 2023
- Accurate MRF-Based 3D Multi-Channel B 1 + Mapping in the Human Body at 7 T. NMR Biomed, 2025