Assessment of combined use of ArcCheck^® detector and portal dosimetry for delivery quality assurance of head and neck and prostate volumetric‐modulated arc therapy

Abstract

PurposeTo assess the efficiency of combined use of ArcCheck® detector (AC) and portal dosimetry (PDIP) for delivery quality assurance of head and neck and prostate volumetric‐modulated arc therapy.Materials and methodsMeasurement processes were studied with the Gamma index method according to three analysis protocols. The detection sensitivity to technical errors of each individual or combined measurement processes was studied by inserting collimator, dose and MLC opening error into five head and neck and five prostate initial treatment plans. A total of 220 plans were created and 660 analyses were conducted by comparing measurements to error free planned dose matrix.ResultsFor head and neck localization, collimator errors could be detected from 2° for AC and 3° for PDIP. Dose and MLC errors could be detected from 2% and 0.5 mm for AC and PDIP. Depending on the analysis protocol, the detection sensitivity of total simulated errors ranged from 54% to 88% for AC vs 40% to 74% for PDIP and 58% to 92% for the combined process. For the prostate localization, collimator errors could be detected from 4° for AC while they could not be detected by PDIP. Dose and MLC errors could be detected from 3% and 0.5 mm for AC and PDIP. The detection sensitivity of total simulated errors ranged from 30% to 56% for AC vs 16% to 38% for PDIP and 30% to 58% for combined process.ConclusionThe combined use of the two measurement processes did not statistically improve the detectability of technical errors compared to use of single process.

Error sensitivity of a log file analysis tool compared with a helical diode array dosimeter for VMAT delivery quality assurance

“…The results obtained when trying to detect MLC errors of our AC protocols are comparable with the results of their study.Delta 4 shows the same behavior as the ArcCHECK Phantom for both global gamma protocols with 3%/3 mm and 2%/2 mm.Moliner et al investigated, among other QA tools, the AC detector. The results of this study, using collimator, dose and MLC errors, are in agreement with our investigation of gamma criteria 3%/3 mm and 2%/2 mm for all treatment sites 10. Log files are generated by the linac and therefore are insensitive to miscalibration of any component such as leaf position.…”

“…The agreement for both the reference and the non-error-free plans for AC gamma passing rate is consistent with previous research not using log files. 3,[9][10][11]13,14 Many studies evaluated the The essential strength of our investigation is that all measurements were performed with AC, LW and ionization chamber at the same time. Log files were generated during AC measurements of all plans.…”

“…AC is widely used, and standard gamma criteria (see Table 1) can be found in in the literature and were applied for AC evaluation. 10,11 For LW, no standard gamma criteria have been established yet in the literature. It was important for us that reference plans could be detected as such (specificity = 100%).…”

“…8 Numerous delivery QA methods have already been compared with each other. [9][10][11] However, the comparison of the sensitivity of 4 Hz log files of an Elekta Synergy linac with the sensitivity of a standard three-dimensional (3D) phantom for VMAT delivery QA has not yet been reported in literature. The aim of this study is to compare log file analysis (LINACWatch ® , Qualiformed) with a standard 3D phantom (ArcCHECK ® , Sun Nuclear) and ionization chamber using different kinds of treatment plans containing MLC, dose, and collimator errors.…”

Winston-Lutz-Gao Test on the True Beam STx Linear Accelerator

“…In the medical physics field, there appears to be some confusion between the Winston-Lutz test and the End-to-End test in the single iso-multiple mets treatment QA process. [13] demonstrated that even the linac collimator has 2˚ -3˚ mechanical error and MLC has 0.5 mm mechanical error, the patient specific QA still cannot 100% to detect the those errors.…”