Patient specific pre-treatment QA verification using an EPID approach

Area of Science:

• Medical Physics
• Radiation Oncology
• Software Engineering

Background:

• Intensity modulated radiation therapy (IMRT) requires rigorous patient-specific quality assurance (QA) for safe and effective treatment.
• Electronic portal imaging devices (EPIDs) offer a method for measuring radiation fluence during treatment delivery.
• Accurate conversion of EPID measurements to treatment planning system (TPS) equivalent fluence maps is crucial for QA.

Purpose of the Study:

• To validate the MU-EPID software for patient-specific pre-treatment QA of IMRT.
• To assess the accuracy of fluence map reconstruction from EPID measurements using the MU-EPID software.
• To evaluate the software's capability in providing comprehensive 3D and 2D dosimetric analysis.

Main Methods:

• Developed MU-EPID software to convert EPID-acquired DICOM images to TPS-equivalent fluence maps.
• Processed Varian, Elekta, and Siemens EPID DICOM images.
• Validated the software using 20 IMRT plans from various treatment sites with a Varian a-Si 1000 EPID and Pinnacle TPS.
• Performed comparative analyses of isodose distributions, dose profiles, DVHs, and gamma index.

Main Results:

• The MU-EPID software successfully converted EPID images to equivalent fluence maps.
• Gamma analysis showed an average passing rate of 97.44% using a 3% and 3 mm criterion.
• Comparisons of isodose, DVH, and dose profiles demonstrated good agreement between calculated and reconstructed plans.
• The software supports Varian, Elekta, and Siemens EPID DICOM image formats.

Conclusions:

• The MU-EPID software is a clinically viable tool for patient-specific IMRT QA.
• It provides accurate 3D dosimetric evaluation through DVH comparison.
• Offers a 2D gamma analysis option for comprehensive treatment verification.