A power efficient actively shielded two-channel transverse MRI gradient coil numerical design

Haile Baye Kassahun; Sadeq S Alsharafi; Ahmed M Badawi; AbdEl-Monem M El-Sharkawy

doi:10.1016/j.jmr.2023.107526

A power efficient actively shielded two-channel transverse MRI gradient coil numerical design

J Magn Reson. 2023 Sep:354:107526. doi: 10.1016/j.jmr.2023.107526. Epub 2023 Jul 26.

Authors

Haile Baye Kassahun¹, Sadeq S Alsharafi², Ahmed M Badawi², AbdEl-Monem M El-Sharkawy²

Affiliations

¹ Systems and Biomedical Engineering, Faculty of Engineering, Cairo University, Giza, Egypt. Electronic address: haile.kassahun.a@eng-st.cu.edu.eg.
² Systems and Biomedical Engineering, Faculty of Engineering, Cairo University, Giza, Egypt.

PMID: 37536091
DOI: 10.1016/j.jmr.2023.107526

Abstract

Large and fast electrical current pulses are typically applied to conventional single-channel transverse MR gradient coils. However, these pulses result in a significant amount of power losses and heating of the coils. Previously, we presented a cylindrical multi-channel Z-gradient coil design that has better power efficiency compared to the single-channel design. In this work, we further investigate the DC power advantage for a two-channel actively-shielded transverse cylindrical gradient coil over the single-channel design. The conventional coil quadrants are radially divided into two sections, one for each channel, for both the primary and shielding surfaces. The symmetric inner sections of both the primary and shielding coils are assigned to the first channel, while the outer enclosing sections for each quadrant are assigned to the second channel. Discrete wire design is employed, where quasi-elliptic functions are used to parameterize the turns of each section. The coil geometric parameters, section size, number of turns, and turn locations are used as the design optimization parameters. The coils are optimized to maximize the coil's efficiency while keeping the linearity error less than 10% and the shielding ratio above 85%. The design procedure is employed to design both the single and two-channel transverse gradient coils for comparison. Eleven different two-channel configurations having different section sizes were investigated. Results show that the power used to drive the most power-efficient two-channel coil is less than that of the single-channel design by ∼25%. Moreover, the two-channel configuration showed slightly better shielding efficiency.

Keywords: Discrete wire method; MRI transverse gradient coil; Power dissipation; Two-channel.