A Dosimetric Parameter Reference Look-Up Table for GRID Collimator-Based Spatially Fractionated Radiation Therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Physics

Background:

• Calculating dose heterogeneity parameters in GRID therapy is complex for treatment planning systems (TPS).
• Accurate dose computation is crucial for effective and safe GRID therapy delivery.

Purpose of the Study:

• To develop and validate reference dose tables for a standard GRID collimator to address computational challenges.
• To assess the accuracy and consistency of dosimetric parameters derived from these tables for various tumor configurations.

Main Methods:

• Implemented a .decimal Inc. GRID collimator in the Eclipse TPS and validated dose calculation accuracy.
• Simulated ellipsoidal tumors of varying sizes and depths, treated with 6MV photons to a 20 Gy prescription dose.
• Derived GRID therapy dosimetric parameters (D5-D95, EUD, PVDR) and compared them with profile measurements.

Main Results:

• Tumor size and depth variations resulted in dose parameter differences within 5% of the prescription dose.
• PVDR differed from D10/D90, but D10/D90 variations remained within 11% for similar tumor depths.
• Developed three approximation equations for calculating equivalent uniform doses (EUDs) for different radiosensitivity levels.

Conclusions:

• The developed reference dose tables provide consistent and predictable dosimetric parameters for GRID therapy.
• These tables serve as a valuable reference tool for improving dose calculations in treatment planning systems.
• The findings support the clinical application of GRID therapy with enhanced computational accuracy.