Measurement of isocenter alignment accuracy and image distortion of an 0.35 T MR-Linac system.

摘要: For hybrid devices combining magnetic resonance (MR) imaging and a linac for radiation treatment, the isocenter accuracy as well image distortions have to be checked. This study presents new phantom investigate MR-Linacs in single measurement terms of (i) isocentricity irradiation (ii) alignment relative each other using polymer dosimetry gel (iii) 3-dimensional (3D) geometric MR distortions. The evaluation irradiated was performed immediately after with component 0.35 T MR-Linac T2-weighted turbo spin-echo sequence. Eight plastic grid sheets within allow 3D by comparing positions intersections (control points) MR-image their nominal position obtained from CT-scan. distance found (0.8  ±  0.9) mm measurements 32 acquisitions. mean distortion over whole (0.60  ±  0.28) 99.8% evaluated control points had below 1.5 mm. These geometrical uncertainties considered additional safety margins.