Purpose
We investigated the properties of platinum-catalyzed silicones with suitable characteristics for a biocompatible patient-specific elastic bolus.
Materials & Methods
We applied a platinum-catalyzed silicone (Ecoflex™ 0030) and a platinum cure liquid silicone (Dragon Skin™ 10 MEDIUM) to fabricate a biocompatible bolus using a mold and casting method with a 3D printer. We conducted physical evaluations including the shore hardness, cure time, transparency, and mixed viscosity. The dosimetric characteristics were basically investigated with surface dose and beam quality. For dosimetric evaluations using humanoid phantom, the dose differences between calculated dose and measured dose were compared with those of Dragon skin. To evaluate which boluses fit best, the volume of unwanted air gaps between the bolus and phantom was obtained from CT images. Biological evaluations were conducted on the skin sensitization, skin irritation, and cytotoxicity to ensure safe patient application.
Results
Ecoflex were biologically evaluated as safety materials. In addition, Ecoflex shows excellent physical properties with respect to a low shore hardness (00–30), short curing time (4 h), and low mixed viscosity (3,000). For the dosimetric properties using humanoid phantom, the average dose difference between the calculated dose and measured dose for Ecoflex is about 0.5% better than that of Dragon skin. In addition, a relatively smaller volume of unwanted air gaps for Ecoflex also showed than for Dragon skin, which these results tended to be the same as the dosimetric results.
Conclusion
The physical properties of Ecoflex including excellent adhesive strength, lower shore hardness reduces unwanted air gaps and ensures an accurate dose distribution. Therefore, it is a suitable material for fabricating biocompatible patient-specific elastic bolus. It would be an alternative to other materials of bolus and thus improve the efficiency for clinical use.