Dosimetric characteristics of LinaTech DMLC H multi leaf collimator: Monte Carlo simulation and experimental study

Abstract

This study evaluated the basic dosimetric characteristics of a Dynamic Multi Leaf Collimator (DMLC) using a diode detector and film measurements for Intensity Modulated Radiation Therapy Quality Assurance (IMRT QA). The EGSnrc Monte Carlo (MC) simulation system was used for the determination of MLC characteristics. Radiation transmission and abutting leaf leakage relevant to the LinaTech DMLC H were measured using an EDGE detector and EBT3 film. In this study, the BEAMnrc simulation code was used for modeling. The head of Siemens PRIMUS linac (6 MV) with external DMLC H was entered into a BEAMnrc Monte Carlo model using practical dosimetry data. Leaf material density, as well as interleaf and abutting air gaps were determined according to the computed and measured dose profiles. The IMRT QA field was used to evaluate the dose distribution of the simulated DMLC H. According to measurements taken with the EDGE detector and film, the total average measured leakage was 1.60 ± 0.03% and 1.57 ± 0.05%, respectively. For these measurements, abutting leaf transmission was 54.35 ± 1.85% and 53.08 ± 2.05%, respectively. To adapt the simulated leaf dose profiles with measurements, leaf material density, interleaf and abutting air gaps were adjusted to 18 g/cm3, 0.008 cm and 0.108 cm, respectively. Thus, the total average leakage was estimated to be about 1.59 ± 0.02%. The step‐and‐shoot IMRT was implemented and 94% agreement was achieved between the film and MC, using 3%‐3 mm gamma criteria. The results of this study showed that the dosimetric characteristics of DMLC H satisfied international standards.

Impact of Dose Calculation Algorithms and Radiobiological Parameters on Prediction of Cardiopulmonary Complications in Left Breast Radiation Therapy

“…Although PB, an undeveloped model-based algorithm, calculates dose in less time than other algorithms, it does not accurately consider the distribution of secondary electrons in heterogeneous environments via simulation of electron dispersions in one dimension. Therefore, this algorithm is known as a flounce map in the TPS, used in IMRT treatment for plan optimization, but it is not widely used in 3D-CRT plans [ 32 , 33 ]. In contrast, the CC algorithm performs better in modeling secondary electron dispersions, especially in longitudinal and lateral directions.…”

Monte Carlo methods for device simulations in radiation therapy

“…In 2004, EGS5 was introduced, which included improvements in electron and photon physics models and the merged EGS and PEGS (Hirayama et al 2005). The family of EGS codes became the codes of choice in medical applications including brachytherapy, gamma knife, as well as intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), which require 4D simulation capabilities (Jones et al 2003, Stapleton et al 2005, Pourfallah et al 2009, Lobo and Popescu 2010, Belec and Clark 2013, Granton and Verhaegen 2013, Breitkreutz et al 2017, Ishihara et al 2017, Molazadeh et al 2017.…”

Monte Carlo-based analysis of the photon beam fluence with air gap thickness between Linac head exit window and patient’s skin in radiotherapy treatments

“…Therefore, it is important to determine the changes in these properties of the beam with air gap thickness and its effects on the dosimetry quality and subsequently on the radiotherapy treatment quality. The air gap effects on the beam are assessed by the photon interactions with air atoms that will be more negative if the particles contamination number is higher and their energy is lower [5].…”