Commissioning and validation of a Monte Carlo algorithm for spine stereotactic radiosurgery

Area of Science:

• Medical Physics
• Radiotherapy Physics
• Computational Dosimetry

Background:

• Accurate dose calculation is crucial for effective spine stereotactic radiosurgery (SRS).
• Monte Carlo (MC) methods offer high accuracy but require rigorous commissioning and validation for clinical implementation.

Purpose of the Study:

• To commission and validate a 6FFF Monte Carlo (MC) dose calculation algorithm for spine SRS.
• To evaluate the model's accuracy in homogeneous and heterogeneous environments, including anthropomorphic phantoms.

Main Methods:

• Commissioning involved in-air and in-water measurements for model generation and validation.
• Model tuning adjusted light field offset (LO) to improve accuracy.
• Validation used phantoms (StereoPHAN, anthropomorphic spine, VIPAR gel) and patient plans.

Main Results:

• MC calculations showed excellent agreement with measurements (output factors, PDDs within 2%; field sizes within 0.5 mm).
• Dosimetric accuracy in phantoms was high (e.g., StereoPHAN targets within 0.26% ± 0.93%).
• Anthropomorphic phantom and VIPAR gel measurements confirmed accuracy in heterogeneous tissues.

Conclusions:

• The commissioned MC algorithm is validated for spine SRS, including complex heterogeneous cases.
• The algorithm demonstrates sufficient accuracy for clinical release and use in spine SRS treatments.