Effectiveness of EPID-based in-vivo dosimetry with EPIgray® Software for head and neck VMAT treatments.

Objectives: To evaluate the effectiveness of in-vivo dosimetry (IVD) utilizing an electronic portal imaging device (EPID) in conjunction with EPIgray^® software (DOSIsoft, Cachan, France) for assessing the accuracy of dose delivery for the patient when undertaking head and neck (H&N) treatments.

Methods: Using cross-sectional analysis, data were collected from the linear accelerator of twenty patients undergoing (H&N) radiotherapy treatments using the Volumetric Modulated Arc Therapy (VMAT) modality from June 2019 to October 2023 at Gleneagles Hospital Penang, Penang, Malaysia. EPIgray^® software reconstructed the delivered dose based on EPID images. These reconstructed doses were compared with the planned doses to evaluate dose accuracy, specifically looking at how many patient doses fell within the set tolerance range. In addition, RTsafe PseudoPatient™ phantom was involved in this study, and the reconstructed dose with EPIgray^® was compared with the delivered dose and was established as a benchmark for accuracy.

Results: The percentage difference between the reconstructed doses and planned doses (ΔD%) for patients ranged from (1.96) to (-11.1), and the results showed that 60% of the patients' doses were within the tolerance range (±5%). The phantom study resulted in a percentage dose difference (ΔD%) of -1.73%, and this was established as a benchmark for accuracy.

Conclusion: The study proves that using EPID-based in-vivo dosimetry with EPIgray^® software is a precise way to check that the right amount of radiation is being delivered for patients during radiotherapy to head and neck (H&N) treatments. Integrating EPIgray^® into clinical practice enhances dose accuracy and patient safety.