Deployment and performance of model-based dose calculation algorithm in ¹⁹²Ir shielded cylinder brachytherapy.

Area of Science:

• Medical Physics
• Radiation Oncology
• Brachytherapy Dosimetry

Background:

• Traditional brachytherapy planning for heterogeneous cases, like shielded cylinders, relied on templates.
• These template-based methods may lack the precision required for complex dose distributions.
• Integrating advanced algorithms is crucial for improving treatment accuracy in radiation oncology.

Purpose of the Study:

• To integrate a model-based dose calculation algorithm (MBDCA) with 3-D planning for clinical brachytherapy cases.
• Specifically, to address shielded cylinder brachytherapy, previously managed with templates.
• To validate the MBDCA's accuracy against established benchmarks and historical clinical data.

Main Methods:

• AcurosBV (Varian Medical Systems) was implemented as the MBDCA.
• Validation was performed against the AAPM WG reference Test Case #4 for a shielded cylinder.
• Clinical plans generated with ABACUS templates were compared against MBDCA results for various cylinder sizes and prescription doses.

Main Results:

• AcurosBV demonstrated excellent agreement (<1% deviation) with the WG reference plan at reference points.
• Deviations were minimal and primarily confined within the applicator.
• Historical template plans showed higher point doses (3-4% or 2-3%) compared to MBDCA calculations.

Conclusions:

• The MBDCA algorithm accurately calculates doses for shielded cylinder brachytherapy, verified against WG data.
• A 3-4% dose difference was observed compared to historical template methods.
• The MBDCA provides a validated tool for assessing and improving existing brachytherapy treatment plans.