Dosimetric comparison of TG‐43 formalism and HU‐based AcurosBV algorithms in HDR brachytherapy for head‐and‐neck superficial lesions with H.A.M. applicators

Background TG‐43 formalism assumes homogeneous water media, potentially overlooking anatomical heterogeneities that affect dose accuracy. AcurosBV, a model‐based dose calculation algorithm, accounts for tissue and material heterogeneities. This study evaluates their dosimetric differences in high‐dose‐rate (HDR) brachytherapy using Harrison‐Anderson‐Mick (H.A.M.) applicators. Purpose To compare dose‐volume histogram (DVH) metrics calculated using TG‐43 formalism and AcurosBV in patients treated with HDR brachytherapy using H.A.M. applicators for superficial lesions in the head and neck regions. Methods Twenty patients (17 nasal, 3 non‐nasal) received HDR brachytherapy with H.A.M. applicators to a total dose of 40 Gy in eight fractions. Original plans calculated with TG‐43 formalism were retrospectively re‐calculated using AcurosBV (Eclipse v16.1), incorporating Hounsfield unit‐based heterogeneity corrections with dose‐to‐medium reporting. Planning target volumes (PTVs) were contoured by radiation oncologists; organs at risk (OARs) including brain, eyes, lens, optical nerve and skin were auto‐segmented using AutoContour (Radformation Inc., NY). DVH metrics (mean dose, D90%, V100%, V150%, V200%, D0.1cc, D0.2cc, D1cc and D2cc) were compared. The isodose distributions from both algorithms were also evaluated slice by slice. Statistical significance was assessed using a paired Student's t ‐test ( p < 0.05). Results AcurosBV consistently reported lower DVH value in PTV than TG‐43. The average PTV mean dose was 48.65 ± 1.22 Gy (AcurosBV) versus 50.78 ± 1.40 Gy (TG‐43), with significant difference in V100 (−6.43 ± 0.95%, p < 0.003). OAR dose differences were modest (∼1.5%) except for the skin, which showed larger reductions (∼4–5% in D0.1cc–D2cc, p < 10 − 8 ). Visual inspection revealed less conformal isodose distributions in AcurosBV plans due to air cavities and tissue inhomogeneities. Conclusion AcurosBV yielded lower and anatomically informed dose estimates compared with TG‐43 in HDR brachytherapy using H.A.M. applicators. These results support clinical adoption of model‐based algorithms but warrant caution, as dosimetric differences and prior TG‐43 experience may affect existing dose constraints and clinical outcomes.