A new method of time-resolved volumetric (4D) dosimetry combining transversal projected view scintillation imaging with the multi-leaf collimator (MLC) geometry information is presented and demonstrated in a magnetic resonance (MRI) guided linear accelerator (linac). The setup consisted of a time gated intensified camera and a cylindrical plastic scintillator phantom. Positioning the camera outside the 0.35 T magnetic field suppresses the interference between the MRI-linac and dosimeter camera. Transversal view images of the scintillation light were recorded at 20 Hz framerate and the light distribution along optical axis was decoded from the MLC data by Fourier algorithm. Considering scintillation light as dose surrogate, the dose volume was reconstructed with sub-millimeter resolution, and this was tested on an intensity modulated delivery of a TG119 C-shape plan. 3D gamma analysis of the recorded cumulative dose volume as compared to a Monte-Carlo simulation reported 95% pass rate at 3%/3mm criteria. By enabling the use of measurement-based 3D beam comparison metrics, the presented method may provide a comprehensive solution for volumetric end-to-end dosimetry and fast machine performance checks in this challenging environment of an MRI-linac.
|Journal||Journal of Physics: Conference Series|
|State||Published - Aug 29 2019|
|Event||10th International Conference on 3D Radiation Dosimetry, IC3DDose 2018 - Kunshan, China|
Duration: Sep 16 2018 → Sep 19 2018