Research on the Clinical Application Possibility of Silicone as a Tissue Filler in Radiotherapy

Abstract

Background: Due to its good softness, silica gel is now widely used in radiotherapy tissue compensation adhesives, but its relative electron density is high and its CT value is high, so many experts have doubts about its clinical application. This study aimed to explore how silicone can be used as a radiotherapy tissue filler. Methods: Based on the 6-megavolt (MV) X-ray phase-space file, 30 × 30 × 30 cm cube models of water, silicone, and different human tissues were constructed in Geant4 Monte Carlo (MC) software to simulate the transport process of X-rays in those media. The study obtained the central axial energy deposition in silicone and the particle-phase-space information at a depth of 1 cm and 2 cm when the rays passed through all the media. Results: The radiation attenuation in silicone was greater than in water. At a depth of 5 cm, the thickness of the silicone was equivalent to 1.12 times the thickness of the water. In dose built-up area and approximate charged-particle equilibrium, the particle-phase-space composition in silicone were similar to that in water, skin, soft tissue, and adipose tissue, although the particle-phase-space concentration of positrons was slightly higher, and the energy spectrum of each particle was distributed more uniformly. The particle-phase-space composition in silicone was quite different from that in compact bone and cortical bone, and the particle-phase-space concentration of positrons was lower in silicone than in the two bones media. The MC and Pinnacle algorithms were in good agreement in terms of the dose calculation behind the silicone. After the rays had passed through the different thicknesses of silicone, the differences in the two algorithms were within 2.5%. Conclusion: There was negligible impact of secondary dose build-up between the silicone and the bodys surface, and the values calculated by the different treatment planning system (TPS) algorithms were in good agreement. Therefore, silicone is deemed suitable for use as a tissue filler from the perspective of dosage.