title: A comparison of HDR near source dosimetry using a treatment planning system, Monte Carlo simulation, and radiochromic film.
abstract: This study aimed to investigate the high-dose rate Iridium-192 brachytherapy, including near source dosimetry, of a catheter-based applicator from 0.5mm to 1cm along the transverse axis. Radiochromic film and Monte Carlo (MC) simulation were used to generate absolute dose for the catheter-based applicator. Results from radiochromic film and MC simulation were compared directly to the treatment planning system (TPS) based on the American Association of Physicists in Medicine Updated Task Group 43 (TG-43U1) dose calculation formalism. The difference between dose measured using radiochromic film along the transverse plane at 0.5mm from the surface and the predicted dose by the TPS was 24%±13%. The dose difference between the MC simulation along the transverse plane at 0.5mm from the surface and the predicted dose by the TPS was 22.1%±3%. For distances from 1.5mm to 1cm from the surface, radiochromic film and MC simulation agreed with TPS within an uncertainty of 3%. The TPS under-predicts the dose at the surface of the applicator, i.e., 0.5mm from the catheter surface, as compared to the measured and MC simulation predicted dose. MC simulation results demonstrated that 15% of this error is due to neglecting the beta particles and discrete electrons emanating from the sources and not considered by the TPS, and 7% of the difference was due to the photon alone, potentially due to the differences in MC dose modeling, photon spectrum, scoring techniques, and effect of the presence of the catheter and the air gap. Beyond 1mm from the surface, the TPS dose algorithm agrees with the experimental and MC data within 3%.
authors.affiliation: Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA. amousha@ccf.org
authors.forename: Ahmad
authors.initials: A
authors.lastname: Amoush
authors.forename: Marcus
authors.initials: M
authors.lastname: Luckstead
authors.forename: Michael
authors.initials: M
authors.lastname: Lamba
authors.forename: Howard
authors.initials: H
authors.lastname: Elson
authors.forename: William
authors.initials: W
authors.lastname: Kassing
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods*; D003198:Computer Simulation; D005373:Film Dosimetry / Q000295:instrumentation*; D006801:Humans; D015233:Models, Statistical; D009010:Monte Carlo Method; D009369:Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity