Patient-Specific Quality Assurance Protocol for Volumetric Modulated Arc Therapy using Dose Volume Histogram

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Quality Assurance

Background:

• Volumetric Modulated Arc Therapy (VMAT) is a complex radiotherapy technique requiring robust quality assurance.
• Traditional patient-specific quality assurance (PSQA) methods like point dose and gamma index may not detect all clinically significant dose errors.
• Dose Volume Histogram (DVH) metrics offer a more comprehensive assessment of dose distribution.

Purpose of the Study:

• To evaluate the utility of DVH metrics within a VMAT PSQA protocol.
• To identify cases where DVH analysis reveals dose errors missed by conventional methods.
• To assess the clinical relevance of DVH-based dose error detection.

Main Methods:

• Retrospective analysis of 14 head and neck and 10 brain cancer patients treated with VMAT.
• Application of a novel PSQA protocol incorporating Sun Nuclear 3DVH software for DVH error estimation.
• Comparison of DVH metrics with point dose and gamma index measurements for pretreatment verification.

Main Results:

• DVH metrics successfully complemented point dose and gamma index measurements in VMAT PSQA.
• Two cases with point dose discrepancies were attributed to phantom setup errors, with 3DVH confirming acceptable delivered doses.
• All analyzed cases demonstrated that DVH confirmed delivered doses to target volumes and organs at risk were within tolerance.

Conclusions:

• Integrating DVH metrics into VMAT PSQA provides clinically meaningful insights and enhances error detection.
• DVH analysis serves as a valuable investigative tool for diagnosing failed treatment plans by correlating dose errors with patient anatomy.
• DVH metrics are a valuable addition to existing VMAT QA protocols, improving patient safety and treatment accuracy.