Control point analysis comparison for 3 different treatment planning and delivery complexity levels using a...

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Quality Assurance

Background:

• Volumetric-modulated arc therapy (VMAT) is a complex radiotherapy technique.
• Accurate dose delivery verification is crucial for patient safety and treatment efficacy.
• Control Point Analysis offers a method to assess VMAT delivery accuracy at a granular level.

Purpose of the Study:

• To evaluate the efficacy of Control Point Analysis for assessing VMAT plan delivery.
• To compare the delivery accuracy of VMAT plans across different treatment sites (lung SBRT, head-and-neck, prostate) and complexity levels.
• To investigate the impact of control point binning on gamma analysis results.

Main Methods:

• Thirty patient VMAT plans (10 lung SBRT, 10 head-and-neck, 10 prostate) were analyzed.
• Plans were delivered on a Varian linear accelerator and measured using an ArcCHECK phantom.
• Delivered dose was compared to planned dose using Sun Nuclear Patient 6 software with Control Point Analysis and gamma passing criteria (e.g., 3%, 3mm and 2%, 2mm).

Main Results:

• Prostate VMAT plans demonstrated the highest gamma passing percentages (e.g., 95.4%–98.3% for 3%, 3mm).
• Increasing the number of binned control points improved passing rates, particularly for the 2%, 2mm criteria.
• Lung SBRT (high MU/control point) and head-and-neck (high modulation) plans showed lower delivery accuracy per control point compared to prostate plans.

Conclusions:

• Control Point Analysis is a valuable tool for VMAT plan quality assurance.
• Treatment complexity, characterized by Monitor Unit (MU)/control point or modulation degree, impacts delivery accuracy.
• Prostate VMAT plans exhibit superior delivery accuracy compared to lung SBRT and head-and-neck VMAT plans.