Wu, Qiuwen

AbstractThis article investigates the performance of a commercial BeO optically stimulated luminescent (OSL) dosimetry system (myOSLchip, RadPro GmbH International, Remscheid, Germany) through the application of the commissioning framework for luminescent dosimeters as described in the American Association of Physicists in Medicine Task Group 191 (AAPM TG191) report. Initial clinical experiences and dosimetric results are also presented. The following properties of the system were characterized: linearity correction factors ranged from ‐0.5% to +3% for dose levels spanning 0.1 to 20 Gy. Beam quality correction factors (relative to 6 MV) ranged from ‐4.5% (2.5FFF) to +4.5% (15MV) for photon beams and +1.9% (6 MeV) to +4.3% (20 MeV) for electron beams. An average (µ) signal loss per reading of ‐2.13% ± 0.20% was measured, however greater signal loss was observed in the first reading (µ = ‐2.6% ± 0.46%). An initial decline in individual element sensitivity relative to baseline was observed from 0–15 Gy cumulative dose (µ = ‐1.98% ± 0.55%), with negligible further deterioration from 15–32 Gy (µ = ‐2.38% ± 0.85%). Post‐irradiation, there was a transient OSL signal which faded with a half‐life of 1.8 min; this signal enhancement was +5% at 5 min post‐irradiation and +1% at 15 min relative to 24 h. Dosimeter response was not dependent on average dose rate in the range of 100–2500 MU/min. With respect to clinical testing, equal or superior performance compared with aluminum oxide OSLs (nanoDots) is shown for a range of clinical techniques and modalities including TSET, TBI, en‐face electrons, and pacemaker/out‐of‐field measurements. The feasibility of myOSLchip to serve as a primary clinical in vivo dosimetry system and direct replacement for Landauer's microStar system is demonstrated.

AbstractUse of magnetic resonance (MR) imaging in radiation therapy has increased substantially in recent years as more radiotherapy centers are having MR simulators installed, requesting more time on clinical diagnostic MR systems, or even treating with combination MR linear accelerator (MR‐linac) systems. With this increased use, to ensure the most accurate integration of images into radiotherapy (RT), RT immobilization devices and accessories must be able to be used safely in the MR environment and produce minimal perturbations. The determination of the safety profile and considerations often falls to the medical physicist or other support staff members who at a minimum should be a Level 2 personnel as per the ACR. The purpose of this guidance document will be to help guide the user in making determinations on MR Safety labeling (i.e., MR Safe, Conditional, or Unsafe) including standard testing, and verification of image quality, when using RT immobilization devices and accessories in an MR environment.