The production of custom bolus using 3D printers for applications in radiation therapy.

The nature of this work was to determine whether it was feasible to produce 3D printed bolus in a clinical setting and determine the most water equivalent 3D printed material for use as a bolus. Predictions of the water equivalence of multiple 3D printed plastics were made based on their electron density and effective Z. TMR and point dose measurements were carried out to estimate the attenuation properties of the plastics. CT, mass attenuation coefficients and PDDs were compared as methods for determining the radiation properties of the 3D printed plastics. To find the optimal depth scaling factor, the difference between the PDDs measured in the 3D printed plastics and the PDD measured in water were minimised. It was determined that ABS was the most water equivalent 3D printing plastic and could be printed to a sufficient quality for use a bolus material in a clinical setting. A methodology was developed to export a bolus structure created in the clinical treatment planning system and generate a file printable by the 3D printer. ABS was then used to produce an example of clinical bolus and when compared to other clinical bolus materials, the 3D printed bolus shifted the dose distribution by the same amount but provided a higher surface dose