Composite QA for intensity-modulated radiation therapy using individual volume-based 3D gamma indices

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Quality Assurance

Background:

• Intensity-modulated radiation therapy (IMRT) requires rigorous quality assurance (QA) to ensure accurate dose delivery.
• Composite dose-volume histogram (DVH)-based QA is crucial for complex treatment plans.
• Evaluating the sensitivity and feasibility of different QA metrics is essential for improving radiotherapy precision.

Purpose of the Study:

• To investigate the feasibility and sensitivity of individual volume-based 3D gamma indices for composite IMRT QA.
• To compare the performance of individual volume gamma indices against global gamma indices.
• To assess the correlation between gamma indices and dose-volume histogram (DVH) metrics.

Main Methods:

• Performed composite IMRT QA for 15 cervical cancer patients using ArcCHECK.
• Evaluated percentage dosimetric errors (%DEs) of DVH metrics and percentage gamma passing rates (%GPs) for individual volumes and global indices.
• Utilized receiver operating characteristic (ROC) curves to determine the sensitivity of gamma indices.

Main Results:

• Most DVH metric %DEs were within 3%.
• Individual volume-based %GPs showed a higher correlation with DVH metrics (%DEs) compared to global %GPs.
• Individual volume-based %GPs demonstrated higher sensitivity (Area Under the Curve) in ROC analysis than global %GPs.

Conclusions:

• Individual volume-based 3D gamma indices are feasible and sensitive for composite IMRT QA.
• These indices offer improved correlation with DVH metrics and enhanced sensitivity compared to global indices.
• The findings support the adoption of individual volume-based gamma indices for more robust IMRT QA.