Experimental characterization of magnetically focused electron contamination at the surface of a high‐field inline MRI‐linac

• DOI: 10.1002/mp.13847
• Publication Date: 2019-10-06T08:12:38Z
• Authors: Natalia F. Roberts; Elizabeth Patterson; Urszula Jelen; Trent Causer; Lois Holloway; Gary Liney; Michael Lerch; Anatoly B. Rosenfeld; Dean Cutajar; Bradley M. Oborn; Peter Metcalfe
• Keywords: Isocenter

Purpose The fringe field of the Australian MRI‐linac causes contaminant electrons to be focused along central axis resulting in a high surface dose. This work aims characterize this effect using Gafchromic film and high‐resolution detectors, MO Skin TM microDiamond. secondary aim is investigate influence inline magnetic on relative dose response these detectors. Methods has unique feature that linac mounted rails allowing for measurements performed at different strengths while maintaining constant source‐to‐surface distance (SSD). Percentage depth doses (PDD) were collected SSD 1.82 m solid water phantom positioned low region then isocenter MRI where 1 T. Measurements range sizes taken with , microDiamond, ® EBT3 film. detectors’ responses T compared near 0 PDD beyond electron contamination, is, 20 mm depth. inside bore among Results MRI, as measured was 104.5% 2.1 × 1.9 cm 2 185.6% 6.1 5.8 369.1% 11.8 11.5 711.1% 23.5 23 . detector contamination showed agreement between Film both detectors further demonstrating their unaffected by field. Conclusions Experimental characterization sizes. microDiamond region, confirmed 1‐T