Premium
SU‐F‐T‐238: Analyzing the Performance of MapCHECK2 and Delta4 Quality Assurance Phantoms in IMRT and VMAT Plans
Author(s) -
Lu SH,
Tsai YC,
Lan HT,
Wen SY,
Chen LH,
Kuo SH,
Wang CW
Publication year - 2016
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4956378
Subject(s) - imaging phantom , ionization chamber , nuclear medicine , quality assurance , radiation treatment planning , dosimetry , radiation therapy , significant difference , delta , medicine , physics , ion , radiology , external quality assessment , pathology , quantum mechanics , ionization , astronomy
Purpose: Intensity‐modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) have been widely investigated for use in radiotherapy and found to have a highly conformal dose distribution. Delta 4 is a novel cylindrical phantom consisting of 1069 p‐type diodes with true treatments measured in the 3D target volume. The goal of this study was to compare the performance of a Delta 4 diode array for IMRT and VMAT planning with ion chamber and MapCHECK2. Methods: Fifty‐four IMRT (n=9) and VMAT (n=45) plans were imported to Philips Pinnacle Planning System 9.2 for recalculation with a solid water phantom, MapCHECK2, and the Delta4 phantom. To evaluate the difference between the measured and calculated dose, we used MapCHECK2 and Delta 4 for a dose‐map comparison and an ion chamber (PTW 31010 Semiflex 0.125 cc) for a point‐dose comparison. Results: All 54 plans met the criteria of <3% difference for the point dose (at least two points) by ion chamber. The mean difference was 0.784% with a standard deviation of 1.962%. With a criteria of 3 mm/3% in a gamma analysis, the average passing rates were 96.86%±2.19% and 98.42%±1.97% for MapCHECK2 and Delta 4 , respectively. The student t‐test of MapCHECK2/Delta 4 , ion chamber/Delta 4 , and ion chamber/MapCHECK2 were 0.0008, 0.2944, and 0.0002, respectively. There was no significant difference in passing rates between MapCHECK2 and Delta 4 for the IMRT plan (p = 0.25). However, a higher pass rate was observed in Delta 4 (98.36%) as compared to MapCHECK2 (96.64%, p < 0.0001) for the VMAT plan. Conclusion: The Pinnacle planning system can accurately calculate doses for VMAT and IMRT plans. The Delta 4 shows a similar result when compared to ion chamber and MapCHECK2, and is an efficient tool for patient‐specific quality assurance, especially for rotation therapy.