Validation for Sensitivity and Accuracy of EPID Dosimetry Algorithm in Radiotherapy

Background: In-vivo dosimetry (IVD) is a significant challenge in radiotherapy. As treatment complexity increases, more accurate and efficient strategies are needed to verify the dose delivered to patients. This study investigates the treatment of IMRT technique and validates its implementation using a-Si EPID. Materials and Methods: The EPID calibration curve and correction coefficients for field size were obtained. The off-axis response was calculated and measured for EPID pixels. The equivalent path length matrix was calculated using DRR images and slab phantoms. A verified back-projection algorithm was used to calculate the ۲D dose distribution matrix on the isocenter plate. Subsequently, the dose distribution of other treatment fractions was evaluated in terms of inter-fraction and intra-fraction variations. To assess the method's sensitivity in IMRT, errors were introduced in the patient's position and the MLC leaf positions, and the method's ability to detect these errors was investigated. Results: The dose distribution obtained from EPID was compared to the treatment planning system (TPS) results for a human prostate phantom. The inter-fraction results comparing between the first and other fraction ۹۹.۹۴% of points in average and in forms of intra-fraction for the first, second, third and fourth segments in average ۹۹.۹۱%, ۹۹.۹%, ۹۹.۸۲% and ۹۸% of points were passed the criteria respectively. Based on the results, the proposed method has acceptable sensitivity. Conclusion: The proposed method showed acceptable compatibility with TPS and can be used for real-time EPID dosimetry. The method does not require time-consuming computations, making it suitable for clinical use.

کلیدواژه ها:

Real-Time EPID Dosimetry ، Digitally Reconstructed Radiograph ، Radiotherapy