The dosimetric accuracy of a commercial model-based dose calculation algorithm in modeling a six-groove direction modulated brachytherapy tandem applicator

<i>Objective.</i>With advancements in high-dose rate brachytherapy, the clinical translation of intensity modulated brachytherapy (IMBT) innovations necessitates utilization of model-based dose calculation algorithms (MBDCA) for accurate and rapid dose calculations. This study uniquely benchmarks a commercial MBDCA, BrachyVision ACUROS^TM(BVA), against Monte Carlo (MC) simulations, evaluating dose distributions for a novel IMBT applicator, termed as the<i>six-groove</i>Direction Modulated Brachytherapy (DMBT) tandem, expanding beyond previous focus on partially shielded vaginal cylinder applicators, through a novel methodology.<i>Approach.</i>The DMBT tandem applicator, made of a tungsten alloy with six evenly spaced grooves, was simulated using the GEANT4 MC code. Subsequently, two main scenarios were created using the BVA and reproduced by the MC simulations: '<i>Source at the Center of the Water Phantom (SACWP)</i>' and '<i>Source at the Middle of the Applicator (SAMA)</i>' for three cubical virtual water phantoms (20 cm)³, (30 cm)³, and (40 cm)³. A track length estimator was utilized for dose calculation and 2D/3D scoring were performed. The difference in isodose surfaces/lines (i.e. coverage) at each voxel,<i>ΔD</i>_{Isodose Levels/Lines}, was thus calculated for relevant normalization points (<i>r</i>_ref).<i>Results.</i>The coverage was comparable, based on 2D scoring, between the BVA and MC isodose surfaces/lines for the region of clinical relevance, (i.e. within 5 cm radius from the source) with<i>ΔD</i>_{Isodose Lines}(<i>r</i>_ref: 1 cm from the source) falling within 2% for the two scenarios for all phantom sizes. For the phantom (20 cm)³,<i>ΔD</i>_{Isodose Levels}(3D scoring) recorded the range [-3.0% +6.5%] ([-7.4% +7.3%]) for 95% of the voxels of the same scoring volume for the SACWP (SAMA) scenario.<i>Significance.</i>The results indicated that the BVA could render comparable coverage as compared to the MC simulations in the region of clinical relevance for different phantom sizes.<i>ΔD</i>_{Isodose Lines}may offer an advantageous metric for evaluation of MBDCAs in clinical setting.