Feasibility of polymer gel-based measurements of radiation isocenter accuracy in magnetic fields.

Feasibility of polymer gel-based measurements of radiation isocenter accuracy in magnetic fields.
Phys Med Biol. 2018 May 03;:
Authors: Dorsch S, Mann P, Lang C, Häring P, Runz A, Karger CP
Abstract
For conventional irradiation devices, the radiation isocenter accuracy is determined by star shot measurements on films. In magnetic resonance (MR)-guided radiotherapy devices, the results of this test may be altered by the magnetic field and the need to align radiation and imaging isocenter may require a modification of measurement procedures. Polymer dosimetry gels (PG) may offer a way to perform both, radiation and imaging isocenter test, however, it has to be shown first that PG reveals comparable results as the conventionally applied films. Therefore star shot measurements were performed at a linear accelerator using PG as well as radiochromic films. PG were evaluated by MR imaging and the isocircle radius and the distance between the isocircle center and the room isocenter were determined. Two different types of experiments were performed: i) a standard star-shot isocenter test and (ii) a star shot, where the detectors were placed between the pole shoes of an experimental electro magnet operated either at 0 T or 1 T. For the standard star shot, PG evaluation was independent of the time delay after irradiation (1h, 24h, 48h and 216h) and the results were comparable to those of film measurements. Within the electro magnet, the isocir...

Source: Physics in Medicine and Biology - May 3, 2018 Category: Physics Authors: Dorsch S, Mann P, Lang C, Häring P, Runz A, Karger CP Tags: Phys Med Biol Source Type: research