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

Abstract

PurposeThe purpose of the study was to integrate model-based dose calculation algorithm (MBDCA) and 3-D planning into our institutional capabilities for clinical cases with inherent heterogeneities, namely shielded cylinder cases, which were previously performed using templates. Methods and MaterialsAcurosBV (Varian Medical Systems) was selected as MBDCA, and we compared results against the American Association of Physicists in Medicine working group (WG) reference Test Case #4, which contains a 36-mm-diameter 180-degree shielded cylinder. The last five clinically used template plans, as generated with ABACUS (Varian Medical Systems), were compared against MBDCA results. Clinical plans used 20-, 23-, and 26-mm-diameter cylinders, prescribed from 5 to 7 Gy, 50- to 110-mm active length, 7 to 21 dwell positions, with 5- or 10-mm spacing. ResultsCompared with the WG reference plan, AcurosBV produced excellent agreement, within 1% at reference points. Larger deviations arose only within the applicator itself. Historical plans generated using ABACUS had higher point dose than AcurosBV by 3–4% or 2–3% using transport within medium at prescription points, with dose to medium or water, respectively. ConclusionsTo verify the accuracy of our MBDCA algorithm, we benchmarked against the WG data set available for shielded cylinders. We discovered a 3–4% difference in dose from our established historical templates, which is easily outweighed by daily positioning uncertainties. Dose distributions from MBDCA were used to assess and validate existing historical templates.