MRI quality control for low-field MR-IGRT systems: Lessons learned.

Autor: Michael Gach H; Department of Radiation Oncology, Washington University in St. Louis, St. Louis, Missouri, 63110, USA.; Department of Radiology, Washington University in St. Louis, St. Louis, Missouri, 63110, USA.; Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, 63110, USA., Curcuru AN; Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, 63110, USA., Wittland EJ; Department of Radiation Oncology, Barnes Jewish Hospital, St. Louis, Missouri, 63110, USA., Maraghechi B; Department of Radiation Oncology, Washington University in St. Louis, St. Louis, Missouri, 63110, USA., Cai B; Department of Radiation Oncology, Washington University in St. Louis, St. Louis, Missouri, 63110, USA., Mutic S; Department of Radiation Oncology, Washington University in St. Louis, St. Louis, Missouri, 63110, USA., Green OL; Department of Radiation Oncology, Washington University in St. Louis, St. Louis, Missouri, 63110, USA.
Jazyk: angličtina
Zdroj: Journal of applied clinical medical physics [J Appl Clin Med Phys] 2019 Oct; Vol. 20 (10), pp. 53-66. Date of Electronic Publication: 2019 Sep 21.
DOI: 10.1002/acm2.12713
Abstrakt: Purpose: To present lessons learned from magnetic resonance imaging (MRI) quality control (QC) tests for low-field MRI-guided radiation therapy (MR-IGRT) systems.
Methods: MRI QC programs were established for low-field MRI- 60 Co and MRI-Linac systems. A retrospective analysis of MRI subsystem performance covered system commissioning, operations, maintenance, and quality control. Performance issues were classified into three groups: (a) Image noise and artifact; (b) Magnetic field homogeneity and linearity; and (c) System reliability and stability.
Results: Image noise and artifacts were attributed to room noise sources, unsatisfactory system cabling, and broken RF receiver coils. Gantry angle-dependent magnetic field inhomogeneities were more prominent on the MRI-Linac due to the high volume of steel shielding in the gantry. B 0 inhomogeneities measured in a 24-cm spherical phantom were <5 ppm for both MR-IGRT systems after using MRI gradient offset (MRI-GO) compensation on the MRI-Linac. However, significant signal dephasing occurred on the MRI-Linac while the gantry was rotating. Spatial integrity measurements were sensitive to gradient calibration and vulnerable to shimming. The most common causes of MR-IGRT system interruptions were software disconnects between the MRI and radiation therapy delivery subsystems caused by patient table, gantry, and multi-leaf collimator (MLC) faults. The standard deviation (SD) of the receiver coil signal-to-noise ratio was 1.83 for the MRI- 60 Co and 1.53 for the MRI-Linac. The SD of the deviation from the mean for the Larmor frequency was 1.41 ppm for the MRI- 60 Co and 1.54 ppm for the MRI-Linac. The SD of the deviation from the mean for the transmitter reference amplitude was 0.90% for the MRI- 60 Co and 1.68% for the MRI-Linac. High SDs in image stability data corresponded to reports of spike noise.
Conclusions: There are significant technological challenges associated with implementing and maintaining MR-IGRT systems. Most of the performance issues were identified and resolved during commissioning.
(© 2019 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.)
Databáze: MEDLINE
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