Intra-coil interactions in split gradient coils in a hybrid MRI-LINAC system

Tang, Fangfang, Freschi, Fabio, Sanchez Lopez, Hector, Repetto, Maurizio, Liu, Feng and Crozier, Stuart (2016) Intra-coil interactions in split gradient coils in a hybrid MRI-LINAC system. Journal of Magnetic Resonance, 265 52-58. doi:10.1016/j.jmr.2016.01.013

Author Tang, Fangfang
Freschi, Fabio
Sanchez Lopez, Hector
Repetto, Maurizio
Liu, Feng
Crozier, Stuart
Title Intra-coil interactions in split gradient coils in a hybrid MRI-LINAC system
Journal name Journal of Magnetic Resonance   Check publisher's open access policy
ISSN 1096-0856
Publication date 2016-04-01
Sub-type Article (original research)
DOI 10.1016/j.jmr.2016.01.013
Open Access Status Not Open Access
Volume 265
Start page 52
End page 58
Total pages 7
Place of publication Maryland Heights, MO, United States
Publisher Academic Press
Language eng
Abstract An MRI–LINAC system combines a magnetic resonance imaging (MRI) system with a medical linear accelerator (LINAC) to provide image-guided radiotherapy for targeting tumors in real-time. In an MRI–LINAC system, a set of split gradient coils is employed to produce orthogonal gradient fields for spatial signal encoding. Owing to this unconventional gradient configuration, eddy currents induced by switching gradient coils on and off may be of particular concern. It is expected that strong intra-coil interactions in the set will be present due to the constrained return paths, leading to potential degradation of the gradient field linearity and image distortion. In this study, a series of gradient coils with different track widths have been designed and analyzed to investigate the electromagnetic interactions between coils in a split gradient set. A driving current, with frequencies from 100 Hz to 10 kHz, was applied to study the inductive coupling effects with respect to conductor geometry and operating frequency. It was found that the eddy currents induced in the un-energized coils (hereby-referred to as passive coils) positively correlated with track width and frequency. The magnetic field induced by the eddy currents in the passive coils with wide tracks was several times larger than that induced by eddy currents in the cold shield of cryostat. The power loss in the passive coils increased with the track width. Therefore, intra-coil interactions should be included in the coil design and analysis process.
Keyword Eddy currents
Electromagnetic interactions
Gradient coil
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: HERDC Pre-Audit
School of Information Technology and Electrical Engineering Publications
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