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Updated: Sep 15, 2025
Radiation Planning Assistant - A Streamlined, Fully Automated Radiotherapy Treatment Planning System
Published on: April 11, 2018
Evaluation of a Monte Carlo based EPID system for patient-specific IMRT and VMAT quality assurance
Wuji Sun1, Chao Ge1, Yinghua Shi1
1Department of Radiation Oncology & Therapy, The First Hospital of Jilin University, Changchun, China.
Purpose:
This study aims to evaluate the performance of a new electronic portal imaging device (EPID) system with a Monte Carlo (MC) based algorithm for patient-specific quality assurance (PSQA), ensuring its reliability and effectiveness in treatment verification efficiency and precision.
Methods:
Sixteen patients with various tumor sites were divided evenly into two groups for dynamic intensity-modulated radiation therapy and volumetric modulated arc therapy verification. Measurements were performed on a UIH uRT-linac 506c linear accelerator with a Varex Imaging XRD 1642 EPID. The performance of the EPID was assessed for sensitivity to errors in monitor units, collimator angle, field offset, field size, and multi-leaf collimator functionality. Treatment plans were modified for each error and verified to determine the capability of the system to detect perturbations from the planned dose distribution, which was quantitatively analyzed using γ index analysis (2%/2 mm, 10% low-dose threshold). Additionally, the ArcCHECK phantom was employed to validate the EPID system for PSQA and induced error detection. Pearson's correlation coefficient was employed to assess correlations between γ passing rates and induced errors.
Results:
The EPID system showed high accuracy in dose linearity and error detection, with γ passing rates consistently above 95% for original plans. Sensitivity tests indicated strong correlations between induced errors and γ passing rates, confirming the capability of this system to detect subtle dosimetric discrepancies and supporting its application for PSQA. Both EPID and ArcCHECK demonstrated comparable γ passing rates in PSQA of standardized plans and treatment plans, with EPID showing higher or comparable sensitivity to tested errors.
Conclusion:
The EPID Plan QA system showed promising accuracy and sensitivity in detecting errors, proving to be a reliable tool for PSQA. Its seamless integration into clinical workflows is expected to enhance treatment verification efficiency and ensure precise radiotherapy delivery.
