Comprehensive quality assurance for base of skull IMRT

Area of Science:

• Medical Physics
• Radiation Oncology
• Medical Imaging

Background:

• Intensity-modulated radiation therapy (IMRT) is a precise form of radiotherapy used for complex cancer cases.
• Accurate dose delivery verification is crucial for ensuring patient safety and treatment efficacy in radiation oncology.
• Base-of-skull treatments present unique challenges due to nearby critical structures.

Purpose of the Study:

• To perform quality assurance (QA) verification of base-of-skull IMRT treatment plans.
• To assess the accuracy of 3D dosimetry data acquired using the Duke Large Optical-CT Scanner (DLOS) system.
• To compare the measured dose distribution with the planned dose distribution from the Eclipse treatment planning system.

Main Methods:

• Six base-of-skull IMRT plans were delivered to Presage dosimeters in the RPC Head and Neck Phantom.
• Optical-CT scanning with the DLOS system was used to acquire isotropic 2mm 3D dosimetry data.
• Normalized Dose Distribution (NDD) analysis was performed, comparing acquired data to the Eclipse treatment plan.

Main Results:

• The DLOS system provided high-quality 3D dosimetry data, visualized through colormaps, isodose lines, and profiles.
• Excellent agreement was observed between the measured and planned dose distributions.
• NDD analysis showed >90% pass rates for the (3%, 2mm) criteria, with system noise below 0.5%.

Conclusions:

• The study confirms the high accuracy of base-of-skull IMRT treatment delivery in the clinic.
• The DLOS system is a reliable tool for 3D dosimetry QA verification in IMRT.
• These findings support the clinical implementation of precise IMRT for base-of-skull radiation therapy.