ABSTRACT
OBJECTIVE: In diffusing alpha-emitters radiation therapy (DaRT), the diffusion-leakage (DL) model is used to determine the spatial distributions of the emitters and the corresponding alpha dose, critical for a successful treatment. This work presents how variations over realistic ranges of the DL model parameters related to desorption, diffusion and leakage processes affect the alpha dose distribution and the position of the clinically significant alpha particle 10 Gy isodose. This work also presents the effects of three modeling approximations: two source geometry approximations (solid cylinder instead of hollow, pixelized cross section instead of circular), and the single-source dose superposition (instead of the multiple sources direct dose calculation). Approach. A finite volume approach was used to develop numerical schemes to simulate the DL model in one, two and three dimensions and obtain the spatial distributions of the emitters. The corresponding alpha dose distributions were calculated under the assumption of a local deposition of the alpha particles' energies. Variation ranges of the DL model parameters were based on previously published data. For each modeling approximation studied, the error and relative error on the alpha dose distribution were calculated and the displacement of the 10 Gy isodose was evaluated. Main results. Over realistic ranges, the desorption probabilities, diffusion lengths, and leakage probabilities respectively affect the position of the alpha particle 10 Gy isodose by â¼ 0.1 mm, â¼ 1.5 mm and â¼ 0.5 mm. The three modeling approximations studied have a negligible effect on the alpha particle 10 Gy isodose position, with displacements ≤ 0.01 mm. Significance. This work quantitatively evaluates the relative importance of different parameters and approximations in DaRT alpha dose calculations based on their impact not only on the dose variation at a given distance from the source but also on the displacement of clinically significant isodoses. .
