Time-resolved plastic scintillator dosimetry in MR linear accelerators without image distortion

One of the newest developments within radiotherapy is integration Magnetic Resonance (MR) scanners and Megavoltage X-rays from linear accelerators into new MR-Linacs. Some MR-Linacs are able to perform gated treatments based on continuously acquired 2D MR images taken during dose delivery, which has potential reduce margins required for tumor coverage. We have developed a dosimetry system that can provide time-resolved, dose-per-pulse, without distorting in order characterize this technology. The plastic BCF-60 scintillation detector (PSD) coupled an optical PMMA fiber cable. was placed tube filled with water inserted piston dynamic MRI compatible phantom be treated ViewRay MRIdian 0.35 T MR-Linac. performed sinusoidal movement simulate breathing cycle either 4 or 8 s. demonstrate real-time dose-per-pulse measurements causing distortions images. time-resolved revealed systematic rate transients lasted about 1 s every gating sequence where beam turned off. Detection such effects require real time does not interfere gating. • Plastic scintillator alanine dosimeters do show image Time-resolved MR-Linac treatment. Dose at start on, likely affecting homogeneity delivery. Scintillator agree (0.17 ± 0.11) Gy.