Clinical Application of Patient-Specific Bolus Based on Molding and Casting Method in Radiotherapy

Background/Objectives: The use of a patient-specific bolus in radiation therapy is critical for achieving precise dose delivery, particularly for irregular anatomical surfaces. Conventional boluses often suffer from poor conformity and air gaps, leading to suboptimal dose distribution. This study aimed to develop and evaluate a novel bolus fabrication method using the mold-and-casting (M&C) technique, which integrates 3D printing and flexible silicone materials to address these limitations. Methods: The proposed workflow includes CT imaging, 3D modeling, mold fabrication via 3D printing, and silicone casting to produce a patient-specific bolus. The process is followed by quality assurance steps and clinical application. Geometric accuracy was assessed through surface matching and cross-sectional comparisons, and dosimetric performance was evaluated using in vivo measurements with MOSFET detectors. The biocompatibility of the silicone material was tested according to standardized cytotoxicity, skin sensitization, and irritation protocols. Results: The fabricated boluses demonstrated high geometric fidelity, with volumetric and surface discrepancies of less than 3% compared to the planned structures. Dosimetric evaluations indicated that maximum dose differences remained within the clinically acceptable range of ±5%, confirming accurate dose delivery. Biocompatibility tests confirmed that the silicone material is safe for clinical use. Conclusions: The M&C method offers a streamlined approach to patient-specific bolus fabrication that integrates well into existing clinical workflows. Compared to traditional sheet boluses, it significantly reduces air gaps and enhances surface dose uniformity. These findings support the clinical potential of this technique to improve both precision and efficiency in radiation therapy.