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Validation of Delivery Consistency for Intensity-Modulated Radiation Therapy and Volumetric-Modulated Arc Therapy
Wui Ann Woon1,2, Paul B Ravindran2,3, Piyasiri Ekayanake2
1Department of Radiation Oncology, The Brunei Cancer Center, Bandar Seri Begawan, Brunei Darussalam.
Journal of Medical Physics
|July 3, 2018
Summary
The Varian Edge linear accelerator consistently delivers intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) plans for nasopharynx carcinoma and prostate cancer. Electronic portal imaging device and trajectory log files confirmed high accuracy, unlike other commercial systems.
Area of Science:
- Medical Physics
- Radiation Oncology
- Radiotherapy Technology
Background:
- Nasopharynx carcinoma (NPC) and prostate cancer treatments often utilize intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT).
- Ensuring consistent dose delivery from linear accelerators throughout lengthy treatment courses is critical for patient outcomes.
- Evaluating the reliability of various quality assurance (QA) systems for advanced radiotherapy techniques is essential.
Purpose of the Study:
- To investigate the delivery consistency of a Varian Edge linear accelerator for IMRT and VMAT plans in NPC and prostate cancer.
- To compare the accuracy of different measurement systems (EPID, MapCheck2, ArcCheck, log files) for daily QA.
- To assess the long-term reliability of the Varian Edge 120 HD MLC for complex treatment deliveries.
Main Methods:
- Four distinct methods were employed to assess delivery consistency over 34 (NPC) and 29 (prostate) days.
- Measurements included electronic portal imaging device (EPID), MapCheck2, and ArcCheck systems, with gamma analysis against patient-specific QA.
- In-house software analyzed daily log files to reconstruct delivered doses, comparing them to planned doses.
Main Results:
- Trajectory log file and EPID methods demonstrated excellent agreement with minimal daily dose deviations.
- MapCheck2 and ArcCheck systems showed statistically significant differences (P < 0.001) compared to EPID, indicating greater daily fluctuations.
- Concerns were raised regarding the performance and reliability of MapCheck2 and ArcCheck for identifying dosimetric inaccuracies in IMRT/VMAT plans.
Conclusions:
- The Varian Edge linear accelerator with a 120 HD MLC consistently delivers IMRT and VMAT plans throughout extended treatment courses.
- EPID and trajectory log file analysis are reliable methods for verifying daily dose delivery accuracy.
- Further investigation is needed into the discrepancies observed with MapCheck2 and ArcCheck systems for advanced radiotherapy QA.
Keywords:
Dosimetryintensity-modulated radiation therapyquality assurancevolumetric-modulated arc therapyMore Related Videos
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