USE OF 3D PRINTING TECHNOLOGIES IN EXTERNAL RADIOTHERAPY FOR THE FABRICATION OF CUSTOMIZED BOLUS

Abstract

Radiotherapy has challenges for irregular tumors that extend to the skin surface; thus, boluses that act as tissue compensators are used in practice. However, conventional boluses are not adapted to the patient's anatomy or lack a dosimetry characterization, decreasing their effectiveness and precision. Given this situation, this study aimed to develop a method of characterization, design, and manufacturing boluses using 3D printing to improve dose coverage in the target volume in patients with head and neck cancer in photon beams. For this, a dosimetry characterization of the 3D printing material was performed through Hounsfield Units, and a novel experimental setup was proposed to determine the depth dose profiles depending on the 3D printing parameter: infill. Subsequently, a workflow was developed to fabricate bolus through the radiotherapy plan files, and finally, the effect of a printed bolus was evaluated with an anthropomorphic phantom. The results showed that the selected 3D printing material has similar characteristics to water (1.01 ± 0.04 g/cm³ and -115.39 ± 20 HU), making it suitable for clinical use and achieving a maximum dose of 7.8 mm with a 6 MeV beam. The ability of the workflow to generate and manufacture customized boluses adaptable to the patient's anatomy was also validated with an anthropomorphic head phantom manufactured in-house; the 95 % isodose curve in the simulation was on the target volume. It can be concluded that 3D printing technologies can design and manufacture structures comparable to commercial boluses, thus eliminating the discrepancy between the planned treatment and its execution in therapy.