Author: Philip Cutter, Mark D'Souza, Arman Sarfehnia 👨🔬
Affiliation: Toronto Metropolitan University, Sunnybrook Health Sciences Centre, Sunnybrook Health Science Center 🌍
Purpose: Water calorimetry (WC) serves as an important standard for measuring absorbed dose to water, an essential metric in radiation therapy. WC directly and absolutely quantifies energy deposition (and thus dose) by measuring radiation-induced temperature rise. Traditionally, hand blown borosilicate glass vessels are used to create controlled, sensitive volumes for measurement. However, these vessels are fragile, excessively expensive, and have long manufacturing lead time. Being handmade, these vessels often lack precise dimensional consistency, and their designs are limited to only a few feasible variations. This study evaluates the feasibility of 3D-printed plastic vessels coated with parylene-based polymers as durable, cost-effective alternatives to glass.
Methods: Two experiments evaluated polymer-coated plastic vessels under conditions of repeated irradiation. The first compared dose measurements from a hydrogen-saturated, parylene-N coated vessel to a standard glass vessel over 64 days. The second compared a hydrogen-saturated, parylene-C coated vessel to an argon-saturated, parylene-N coated vessel over 14 days. All vessels were prepared similarly, filled with high purity water (< 5 ppb) and saturated with high purity gas (> 99.999%). Dose measurements were validated against theoretical calculations as well as results from treatment planning software for the experimental setup.
Results: Dose measurements were consistent between glass and parylene-coated plastic vessels, and were in line with theoretical expectations, demonstrating their accuracy and reliability. Hydrogen-saturated vessels showed lower measurement variability compared to argon-saturated ones, attributed to hydrogen’s reactivity and impurity-scavenging effectiveness. Parylene coatings demonstrated stability and durability under repeated irradiation across all experiments.
Conclusion: 3D-printed, polymer-coated vessels offer a practical alternative to glass for water calorimetry-based dosimetry. Hydrogen saturation appears to offer superior measurement consistency than argon when other variables are controlled. Such vessels deliver equivalent accuracy, greater durability, and significantly reduce both cost and production limitations, establishing them as a promising alternative for water calorimetry in modern radiation dosimetry.