A comprehensive evaluation of advanced dose calculation algorithms for brain stereotactic radiosurgery

Area of Science:

• Medical Physics
• Radiotherapy
• Radiation Oncology

Background:

• Accurate dose calculation is critical in brain stereotactic radiosurgery (SRS) for both target coverage and normal tissue sparing.
• Advanced algorithms are employed to improve dose calculation accuracy in complex treatment scenarios.

Purpose of the Study:

• To evaluate and compare the dosimetric accuracy of two advanced dose calculation algorithms, Voxel Monte Carlo (VMC) and Acuros XB (AXB), for brain SRS.
• To assess the performance of these algorithms in both clinical patient plans and phantom studies.

Main Methods:

• A retrospective analysis of 138 SRS patient plans (443 targets) using VMC, followed by recalculation with AXB.
• Comparison of target dose metrics (Dref, D95, Dmean) and analysis of dose differences relative to distance from the skull.
• Validation using cylindrical and head phantoms with ion chamber and EBT3 film measurements.

Main Results:

• VMC calculations were generally higher than AXB, with >5% differences in Dref for small targets (<0.3 cm³).
• Dose differences (Dmean, D95) were more pronounced for smaller targets.
• Phantom studies indicated VMC had better agreement with measurements for point dose and high dose spread compared to AXB.

Conclusions:

• Acuros XB may underestimate target dose for small targets in brain SRS compared to Voxel Monte Carlo.
• Voxel Monte Carlo demonstrates a slightly closer agreement with measured doses, suggesting potential advantages for small target accuracy in SRS.