Correlation analysis between 2D and quasi-3D gamma evaluations for both intensity-modulated radiation therapy and volumetric modulated arc therapy

Abstract

The aim of this work was to investigate correlations between 2D and quasi-3D gamma passing rates. A total of 20 patients (10 prostate cases and 10 head and neck cases, H&N) were retrospectively selected. For each patient, both intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans were generated. For each plan, 2D gamma evaluation with radiochromic films and quasi-3D gamma evaluation with fluence measurements were performed with both 2%/2 mm and 3%/3 mm criteria. Gamma passing rates were grouped together according to delivery techniques and treatment sites. Statistical analyses were performed to examine the correlation between 2D and quasi-3D gamma evaluations. Statistically significant difference was observed between delivery techniques only in the quasi-3D gamma passing rates with 2%/2 mm. Statistically significant differences were observed between treatment sites in the 2D gamma passing rates (differences of less than 8%). No statistically significant correlations were observed between 2D and quasi-3D gamma passing rates except the VMAT group and the group including both IMRT and VMAT with 3%/3 mm (r = 0.564 with p = 0.012 for theVMAT group and r = 0.372 with p = 0.020 for the group including both IMRT and VMAT), however, those were not strong. No strong correlations were observed between 2D and quasi-3D gamma evaluations.

Plan-Class Specific Reference Quality Assurance for Volumetric Modulated Arc Therapy

“…Figure 5 shows the daily distributions of the maxRMS by DFV for 5 different pcsr QA plans and 12 real treatment plans which were grouped into the corresponding plan class. Similar MLC position error was revealed by different other previous works [10][11][12][13].…”

Three-dimensional dose reconstruction-based pretreatment dosimetric verification in volumetric modulated arc therapy for prostate cancer

“…Secondly, the degree of modulation in VMAT plans for prostate cancers can also be lower than that for other cancers due to the small treatment field size and less irregular shape of the target volume. Although there has been no concern about the cancer-or structure-specific acceptance criteria for gamma analysis, the degree of modulation may affect the quantity and magnitude of errors, and several studies have reported similar results to ours [14][15][16]. In the study by Vieillevigne et al [16], which performed pretreatment verification for VMAT plans using three different detectors in 15 cases of prostate cancer, the GFRs were less than 2% and less than 7% for the acceptance criteria of 3%/3 mm and 2%/2 mm in all detectors, respectively.…”

Gamma analysis with a gamma criterion of 2%/1 mm for stereotactic ablative radiotherapy delivered with volumetric modulated arc therapy technique: a single institution experience

“…Several studies recently showed irrelevance of the 2D gamma passing rates toward the changes in the clinically relevant dose-volumetric parameters between the treatment plan and actual delivery [ 22 , 25 ]. Information of the 2D gamma evaluation is not enough to detect errors affecting delivered doses which are three-dimensional inside a patient's body [ 26 ]. Moreover, since gamma evaluation is a comprehensive evaluation tool for a plan as a whole and not an evaluation tool for the delivered doses to each organ individually, the dose delivery accuracy to each structure including the target volumes and OARs, could not be verified individually with gamma evaluation [ 13 ].…”

“…However, the accuracy of the various 3D gel dosimeters is not adequate to be used in the clinic yet, owing to the high uncertainty. Some dosimeters recently introduced in the clinic are capable of measuring quasi-3D dose distributions, such as COMPASS™ system (IBA Dosimetry GmbH, Schwarzenbruck, Germany), ArcCHECK™ (Sun Nuclear Corporation, Melbourne, FL, USA), and OCTAVIUS 4D™ system (PTW, Freiburg, Germany) [ 22 , 26 , 28 ]. Although these dosimetry systems can provide more information than the 2D dosimeters, they have their own limitations.…”