Patient QA systems for rotational radiation therapy: a comparative experimental study with intentional errors.

Area of Science:

• Medical Physics
• Radiation Oncology
• Quality Assurance

Background:

• Patient-specific quality assurance (QA) is crucial for rotational radiation therapy.
• Accurate detection of linear accelerator errors is essential for patient safety.

Purpose of the Study:

• To evaluate the efficacy of commercial patient QA systems in identifying linear accelerator-related errors.
• To compare the performance of four distinct QA systems: Delta(4®), OCTAVIUS(®), COMPASS, and Epiqa™.

Main Methods:

• Four rotational intensity modulated radiation therapy (IMRT) plans were analyzed.
• Intentional errors were introduced, including increased monitor units, wider MLC banks, and collimator rotation.
• Measurements were assessed using gamma evaluation (2%/2 mm and 3%/3 mm criteria) and dose-volume histograms.

Main Results:

• Significant variation in error detection rates was observed across systems, with failure rates ranging from 0% to 72%.
• Epiqa™ detected all 20 introduced errors, while Delta(4®) detected 15, and OCTAVIUS(®) and COMPASS detected 8 each.
• Calibration and measurement procedures require improvement for certain QA systems.

Conclusions:

• Commercial QA systems exhibit differential sensitivity to specific linear accelerator errors.
• The effectiveness of error detection is plan-dependent.
• A weak correlation exists between gamma evaluation pass rates and dose-volume histogram deviations.