Commissioning and quality control of a dedicated wide bore 3T MRI simulator for radiotherapy planning

Abstract

The purpose of this paper is to describe a practical approach to commissioning and quality assurance (QA) of a dedicated wide-bore 3 Tesla (3T) magnetic resonance imaging (MRI) scanner for radiotherapy planning. Methods: A comprehensive commissioning protocol focusing on radiotherapy (RT) specific requirements was developed and performed. RT specific tests included: uniformity characteristics of radio-frequency (RF) coil, couch top attenuation, geometric distortion, laser and couch movement and an end-to-end radiotherapy treatment planning test. General tests for overall system performance and safety measurements were also performed. Results: The use of pre-scan based intensity correction increased the uniformity from 61.7% to 97% (body flexible coil), from 50% to 90% (large flexible coil) and from 51% to 98% (small flexible coil). RT flat top couch decreased signal-to-noise ratio (SNR) by an average of 42%. The mean and maximum geometric distortion was found to be 1.25 mm and 4.08 mm for three dimensional (3D) corrected image acquisition, 2.07 mm and 7.88 mm for two dimensional (2D) corrected image acquisition over 500 mm × 375 mm × 252 mm field of view (FOV). The accuracy of the laser and couch movement was less than ±1 mm. The standard deviation of registration parameters for the end-to-end test was less than 0.41 mm. An on-going QA program was developed to monitor the system's performance. Conclusion: A number of RT specific tests have been described for commissioning and subsequent performance monitoring of a dedicated MRI simulator (MRI-Sim). These tests have been important in establishing and maintaining its operation for RT planning.

Sensitivity analysis of different quality assurance methods for magnetic resonance imaging in radiotherapy

“…RT-specific demands like patient positioning (flat tabletop-inserts) and immobilization devices needed to replicate patient treatment position also affect MR image quality. For example, by using a flat tabletop-insert and coil holder, Brynolfsson et al [9] reported that SNR reduced to 66% whilst Xing et al [10] , had an average SNR decrease of 42%. Batumalai et al [11] , showed that for supine RT-specific imaging of the breast, a switch from the standard diagnostic 16-channel prone coil to an 18-channel surface coil decreased SNR by 41% and 45% for supine flat and supine inclined (10°) respectively.…”

An assessment of set up position for MRI scanning for the purposes of rectal cancer radiotherapy treatment planning

“…By adding the bellyboards onto an already raised surface of having a flat couch top, it is not surprising that the signal and image quality suffer from reduced image quality. Xing et al demonstrated a 40% reduction in SNR with the use of a RT flat couch top. McJury et al also demonstrated that adding a structure such as the flat couch can lead to a reduction in SNR from 14% to 40%.…”

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

“…The recommendations given by the American Association of Physicists in Medicine 14 and Institute of Physics and Engineering in Medicine 15 provide guidelines for image quality assurance in diagnostic radiology. In a recent work by Xing et al, 16 the authors demonstrated 40% reduction in SNR using a commercially available fibreglass flatbed specifically designed for treatment planning.…”