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SU‐E‐T‐183: Validation of COMPASS System for RapidArc Patient‐Specific QA
Author(s) -
Huang H,
Tsai P,
Huang Y,
Yeh C
Publication year - 2011
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 - 10.1118/1.3612133
Subject(s) - imaging phantom , compass , nuclear medicine , dosimetry , dose profile , image guided radiation therapy , medicine , medical imaging , medical physics , physics , radiology , quantum mechanics
Purpose: Patient specific QA, one of important QA in radiotherapy, was performed with different devices in hospitals. It was commonly conducted with 2D array devices. To quickly and accurately verify 3D dose delivered is a big issue in clinic. The aim of this study is to validate the COMPASS system for dose verification for rotational and conventional IMRT technique as part of our clinical RapidArc QA program. Methods: Several RapidArc and IMRT cases with different treatment sites were chosen in this study. Each case was measured with MatriXX mounted on the gantry to reconstruct the 3D dose distribution in MultiCube phantom. In order to verify the COMPASS system, 3D dose measured in phantom was compared to that calculated in TPS. The MatriXX was setup on the treatment couch to obtain the 2D dose distribution as well. The OmniPro IˈmRT software was used to compare the measured 2D dose distribution with the results from COMPASS. Results: With 3D dose study, the average GAI (gamma agreement index) was 99.4+−1.0 (96.9∼100.0) for the comparison between COMPASS and TPS. The comparison results showed GAI was 96.5+−3.0 (87.8∼99.6) without detectorˈs angular correction and 98.4+−1.3 (95.2∼99.9) with the correction for the comparison between COMPASS calculation and 2D dose measurements. Conclusions: The COMPASS was validated by 3D dose studies in phantom. And, MatriXX was mounted and fixed on accessory holder of gantry which rotated with gantry to take fields responses; there is no gantry angular correction of detectors. Although the detectors in the MatriXX are ionization chambers, it combined with OmniPro IˈMRT software which implemented with function to correct angular dependence. We applied the angular dependence in our studies to improve the measurement accuracy. In conclusion, the COMPASS system is reliable and can be used in clinical QA program.