Plastic scintillation dosimeter with a conical mirror for measuring 3D dose distribution

Abstract

To test the measurement technique of the three-dimensional (3D) dose distribution measured image by capturing the scintillation light generated using a plastic scintillator and a scintillating screen. Methods: Our imaging system constituted a column shaped plastic scintillator covered by a Gd 2 O 2 S:Tb scintillating screen, a conical mirror and a cooled CCD camera. The scintillator was irradiated with 6 MV photon beams. Meanwhile, the irradiated plan was prepared for the static field plans, two-field plan (2F plan) and the conformal arc plan (CA plan). The 2F plan contained 16 mm 2 and 10 mm 2 fields irradiated from gantry angles of 0 • and 25 • , respectively. The gantry was rotated counterclockwise from 45 • to 315 • for the CA plan. The field size was then obtained as 10 mm 2 . A Monte Carlo simulation was performed in the experimental geometry to obtain the calculated 3D dose distribution as the reference data. Dose response was acquired by comparing between the reference and the measurement. The dose rate dependence was verified by irradiating the same MU value at different dose rates ranging from 100 to 600 MU/min. Deconvolution processing was applied to the measured images for the correction of light blurring. The measured 3D dose distribution was reconstructed from each measured image. Gamma analysis was performed to these 3D dose distributions. The gamma criteria were 3% for the dose difference, 2 mm for the distance-to-agreement and 10% for the threshold. Results: Dose response for the scintillation light was linear. The variation in the light intensity for the dose rate ranging from 100 to 600 MU/min was less than 0.5%, while our system presents dose rate independence. For the 3D dose measurement, blurring of light through deconvolution processing worked well. The 3D gamma passing rate (3D GPR) for the 10 × 10 mm 2 , 16 × 16 mm 2 , and 20 × 20 mm 2 fields were observed to be 99.3%, 98.8%, and 97.8%, respectively. Reproducibility of measurement was verified. The 3D GPR results for the 2F plan and the CA plan were 99.7% and 100%, respectively. Conclusions: We developed a plastic scintillation dosimeter and demonstrated that our system concept can act as a suitable technique for measuring the 3D dose distribution from the gamma results. In the future, we will attempt to measure the 4D dose distribution for clinical volumetric modulated arc radiation therapy (VMAT)-SBRTplans.

PyMedPhys: A community effort to develop an open, Python-based standard library for medical physics applications

“…Many of these tools are in use clinically at affiliated sites, and additionally, aspects of PyMedPhys are implemented around the world for some applications. Many parties have embraced the gamma analysis module (Castle et al, 2022;Cronholm et al, 2020;Gajewski et al, 2021;Galić et al, 2020;Lysakovski et al, 2021;Milan et al, 2019;Pastor-Serrano & Perkó, 2021;Rodrıǵuez et al, 2020;Spezialetti et al, 2021;Tsuneda et al, 2021;Yang et al, 2022), while implementations of the electron cutout factor module and others (Baltz & Kirsner, 2021;Douglass & Keal, 2021;Rembish, 2021) have also been reported. Additionally, the work has been recognized by the European Society for Radiotherapy and Oncology (ESTRO) and referenced as recommended literature in their 3rd Edition of Core Curriculum for Medical Physics Experts in Radiotherapy (Bert et al, 2021).…”

High spatiotemporal resolution scintillation imaging of pulsed pencil beam scanning proton beams produced by a gantry‐mounted synchrocyclotron

“…In the field of radiation oncology clinical physics, scintillation dosimetry has been used for several decades. [7][8][9][10][11][12][13][14] Recently, scintillation imaging, [15][16][17][18][19][20][21][22][23] Cherenkov radiation imaging, [24][25][26][27][28][29] and radioluminescent imaging of un-doped materials [30][31][32][33] have been subject of investigation for potential applications in high spatiotemporal resolution dosimetry.…”

Development of a novel delivery quality assurance system based on simultaneous verification of dose distribution and binary multi-leaf collimator opening in helical tomotherapy

“…Recently, many studies have been conducted on IMRT verification, and various methods for measuring dose distribution using plastic scintillator (PS) emissions have been reported [ 13 – 18 ]. In these studies, a cooled charge-coupled device (CCD) camera or plenoptic camera was used to detect the scintillation light, which can be recorded using these cameras to obtain real-time information on the dose distribution.…”