Comparison of the dose perturbation arising from conventional and the novel PEEK prosthesis materials during high energy radiotherapy with 15 MV photons

Aim: This study aimed to evaluate the dosimetric effects of the metal prosthesis in radiotherapy by Siemens Primus 15 MV linac accelerator. In addition, it proposed the new material could lead to less dose perturbation. Materials and methods: The depth dose distributions of typical hip prostheses were calculated for 15 MV photons by MCNP-4C code. Five metal prostheses were selected to reveal the correlation between material type, density and dose perturbations of prostheses. Furthermore, the effects of the location and thickness of the prosthesis on the dose perturbation were also discussed and analysed. Results: The results showed that the Co-Cr-Mo alloy as the prosthesis had more influence on the dose at the interface of metal tissue. The dose increased at the entrance of this prosthesis and experienced the reduction when passed through it. Finally, the impact of the new PEEK biomedical polymer materials was also investigated, and the lowest dose perturbations were introduced based on the obtained results. Conclusion: It was found that the mean relative dose before and after of PEEK prosthesis was 99·2 and 97·1%, respectively. Therefore, this new biomedical polymer material was proposed to replace the current metal implants.

A comparison of Monte Carlo, anisotropic analytical algorithm (AAA) and Acuros XB algorithms in assessing dosimetric perturbations during enhanced dynamic wedged radiotherapy deliveries in heterogeneous media

BackgroundA comparison of anisotropic analytical algorithm (AAA) and Acuros XB (AXB) dose calculation algorithms with Electron Gamma Shower (EGSnrc) Monte Carlo (MC) for modelling lung and bone heterogeneities encountered during enhanced dynamic wedged (EDWs) radiotherapy dose deliveries was carried out.Materials and methodsIn three heterogenous slab phantoms: water–bone, lung–bone and bone–lung, wedged percentage depth doses with EGSnrc, AAA and AXB algorithms for 6 MV photons for various field sizes (5×5, 10×10 and 20×20 cm2) and EDW angles (15°, 30°, 45° and 60°) have been scored.ResultsFor all the scenarios, AAA and AXB results were within ±1% of the MC in the pre-inhomogeneity region. For water–bone AAA and AXB deviated by 6 and 1%, respectively. For lung–bone an underestimation in lung (AAA: 5%, AXB: 2%) and overestimation in bone was observed (AAA: 13%, AXB: 4%). For bone–lung phantom overestimation in bone (AAA: 7%, AXB: 1%), a lung underdosage (AAA: 8%, AXB: 5%) was found. Post bone up to 12% difference in the AAA and MC results was observed as opposed to 6% in case of AXB.ConclusionThis study demonstrated the limitation of the AAA (in certain scenarios) and accuracy of AXB for dose estimation inside and around lung and bone inhomogeneities. The dose perturbation effects were found to be slightly dependent on the field size with no obvious EDW dependence.