Purpose: To investigate Acuros®XB and AAA algorithms with the presence of high-density prostheses commonly found in the body and to determine the optimal material and density assigned in treatment planning system (TPS).
Methods: Prosthetic devices (hip, knee, and dental implants) were utilized to develop patient-like phantoms. Prostheses were contoured in the TPS and divided into regions with assigned appropriate materials and densities. An iterative process determined the optimal assigned materials/densities for each phantom in the TPS. All treatment plans were computed using both algorithms to compare with the measured data. For the first hip prosthesis phantom two plans were generated, a single field plan and a clinical VMAT plan. The measured data were acquired using Sun Nuclear (SNC) ArcCHECK® with prothesis inside the central cavity. Measurement data for a second hip prosthesis phantom were acquired utilizing SNC MapCHECK® along with two pieces of Gafchromic film at two additional depths. The doses to the knee and dental phantoms were measured with Gafchromic film.
Results: The two hip prostheses phantoms yielded same optimal assigned materials, despite their different sizes. For the femoral head and acetabular components, optimal assigned material/density were Stainless Steel (7.24 g/cm³) and Aluminum (2.6113 g/cm³), respectively. The femoral stem was assigned Titanium Alloy. When the femoral stem was contoured to separate the “neck” and “body” regions the optimal assigned densities of the “neck” was 4.31g/cm³ and the “body” was 4.4001g/cm³. The optimal material/density for the “metal” of the knee prosthesis was Titanium Alloy (4.6144 g/cm³) and its “plastic liner” was PMMA (1.19 g/cm³). The dental fillings were assigned Stainless Steel (8.0 g/cm³).
Conclusion: This work indicates the advantage of contouring a prosthesis into regions to reflect the actual materials present and by assigning the appropriate densities to each region. The two algorithms yielded comparable pass rate results.
Prosthetics, Optimization, Dosimetry
TH- External Beam- Photons: treatment planning/virtual clinical studies