Dosimetric verification for intensity-modulated arc therapy plans by use of 2D diode array, radiochromic film and radiosensitive polymer gel

Abstract

Several tools are used for the dosimetric verification of intensity-modulated arc therapy (IMAT) treatment delivery. However, limited information is available for composite on-line evaluation of these tools. The purpose of this study was to evaluate the dosimetric verification of IMAT treatment plans using a 2D diode array detector (2D array), radiochromic film (RCF) and radiosensitive polymer gel dosimeter (RPGD). The specific verification plans were created for IMAT for two prostate cancer patients by use of the clinical treatment plans. Accordingly, the IMAT deliveries were performed with the 2D array on a gantry-mounting device, RCF in a cylindrical acrylic phantom, and the RPGD in two cylindrical phantoms. After the irradiation, the planar dose distributions from the 2D array and the RCFs, and the 3D dose distributions from the RPGD measurements were compared with the calculated dose distributions using the gamma analysis method (3% dose difference and 3-mm distance-to-agreement criterion), dose-dependent dose difference diagrams, dose difference histograms, and isodose distributions. The gamma passing rates of 2D array, RCFs and RPGD for one patient were 99.5%, 96.5% and 93.7%, respectively; the corresponding values for the second patient were 97.5%, 92.6% and 92.9%. Mean percentage differences between the RPGD measured and calculated doses in 3D volumes containing PTVs were –0.29 ± 7.1% and 0.97 ± 7.6% for the two patients, respectively. In conclusion, IMAT prostate plans can be delivered with high accuracy, although the 3D measurements indicated less satisfactory agreement with the treatment plans, mainly due to the dosimetric inaccuracy in low-dose regions of the RPGD measurements.

Validation of a secondary dose check tool against Monte Carlo and analytical clinical dose calculation algorithms in VMAT

“…Gel and plastic dosimeters 24,25 have been developed to enable a full 3D dose verification matching more accurately the patient geometry. Unfortunately, such methods require time‐consuming procedures and significant human resources, which are not practical for busy treatment centers 26,27 . Moreover, instabilities caused by storage procedure and manufacturing processes, and limitations in repeated usage have been reported 28,29 .…”

“…Unfortunately, such methods require time-consuming procedures and significant human resources, which are not practical for busy treatment centers. 26,27 Moreover, instabilities caused by storage procedure and manufacturing processes, and limitations in repeated usage have been reported. 28,29 More recently, systems based on 2D measurements that allow pseudo-3D dose reconstruction have been proposed to overcome these limitations.…”

Three-dimensional dose comparison of flattening filter (FF) and flattening filter-free (FFF) radiation therapy by using NIPAM gel dosimetry

“…However, the sequential irradiation dependence is less pronounced if the time between the sequential beams had been reduced. Yao et al [12] showed that the treatment planning system (TPS) map can achieve higher conformity to the planning target volume than that of IMRT. Three-dimensional (3D) gel dosimetry was used to validate the dose distribution agreement of VMAT, and the results showed good performance [12].…”

“…Yao et al [12] showed that the treatment planning system (TPS) map can achieve higher conformity to the planning target volume than that of IMRT. Three-dimensional (3D) gel dosimetry was used to validate the dose distribution agreement of VMAT, and the results showed good performance [12]. The passing rate can be remarkably high at approximately 95% agreement compared with that of TPS, with 3%/3 mm criterion [13,14].…”

Patient-Specific quality assurance protocol for volumetric modulated arc therapy using dose volume histogram

“…[ 8 9 ] The desire to estimate the dose to a 3D volume that better approximates the patient geometry may be achieved with gel dosimeters, although such methods are time-consuming and require significant resources to make it feasible in a busy clinical environment. [ 10 11 ] In a similar way, 3D detector arrays allow the dose delivered to a volume to be estimated, outside the confines of a planar arrangement. [ 12 ]…”