Abstract #3562

Evaluation of Multileaf Collimator performance in high magnetic fringe fields for MRI-Linac development

Bin Dong^1,2, Gary P. Liney^1,2,3,4, Kevin K. Zhang^1,4, Lois Holloway^1,2,3,4,5, Peter E. Metcalfe^1,2, and Paul J. Keall^1,5

¹Ingham Institute for Applied Medical Research, Liverpool, Australia, ²Centre for Medical Radiation Physics (CMRP), University of Wollongong, Wollongong, Australia, ³Department of Medical Physics, Cancer Therapy Centre, Liverpool Hospital, Liverpool, Australia, ⁴South Western Sydney Clinical School, University of New South Wales, Liverpool, Australia, ⁵Radiation Physics Laboratory, Sydney Medical School, The University of Sydney, Camperdown, Australia

Hybrid systems combining an MRI with a linear accelerator for image guided radiation treatment are being implemented world-wide. As part of our own development we investigated the effect of increasing magnetic field on the performance of a multi-leaf collimator (MLC) motor and encoder from the treatment head of a linear accelerator. Measurements were made at various locations in the fringe field of a 3T scanner with the MLC positioned to replicate both in-line and perpendicular treatment beam to B0 directions. Results show a static field threshold and speed reduction which is position dependent which can be improved significantly with shielding.

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