Assessment of a carbon fibre MRI flatbed insert for radiotherapy treatment planning

• Published in: British journal of radiology 2016-06, Vol.89 (1062), p.20160108-20160108
• Main Authors: Jafar, Maysam M, Reeves, Jonathan, Ruthven, Matthieu A, Dean, Christopher J, MacDougall, Niall D, Tucker, Arthur T, Miquel, Marc E
• Format: Article
• Language: English
• Subjects: Beds; Carbon; Equipment Design; Equipment Failure Analysis; Hot Temperature; Magnetic Resonance Imaging - instrumentation; Materials Testing; Patient Positioning - instrumentation; Physics and Technology; Radiotherapy Planning, Computer-Assisted - instrumentation; Radiotherapy, Image-Guided - instrumentation
• ISSN: 0007-1285; 1748-880X
• DOI: 10.1259/bjr.20160108

The purpose of this work was to assess heating and radiofrequency (RF) deposition and image quality effects of a prototype three-section carbon fibre flatbed insert for use in MRI. RF deposition was assessed using two different thermometry techniques, infrared thermometry and Bragg-grating thermometry. Image quality effects were assessed with and without the flatbed insert in place by using mineral oil phantoms and a human subject. Neither technique detected heating of the insert in typical MRI examinations. We found that the insert was less suitable for MRI applications owing to severe RF shielding artefact. For spin-echo (SE), turbo spin-echo (TSE) and gradient-echo sequences, the reduction in signal-to-noise ratio (SNR) was as much as 89% when the insert was in place compared with the standard couch, making it less suitable as a patient-support material. Turning on the MultiTransmit switch together with using the scanner's quadrature body coil improved the reduction in SNR from 89% to 39% for the SE sequence and from 82% to 12% for the TSE sequence. No evidence was found to support reports in the literature that carbon fibre is an unsuitable material for use in MRI because of heating. This study suggests that carbon fibre is less suitable for large-scale MRI applications owing to it causing severe RF shading. Further research is needed to establish the suitability of the flatbed for treatment planning using alternative sequences or whether an alternative carbon fibre composite for large-scale MRI applications or a design that can minimize shielding can be found.