Introducing the 3D printed Montreal Mail applicator for surface brachytherapy: A comparative study

In surface brachytherapy, commercial applicators assist with catheter placement, but significant opportunities remain to further improve clinical efficiency. This study introduces the Montreal Mail, a novel modular 3D printed surface brachytherapy applicator, and compares its performance to that of two reference devices.

The Montreal Mail applicator features three generic components, including a 3D printed chainmail, impression paste, and a silicone pad. Each component was characterized radiologically using computed tomography (CT). An anthropomorphic hand phantom, configured to replicate the complex flexion deformity characteristic of Dupuytren's disease, was used to evaluate the Montreal Mail alongside two reference applicators: the Freiburg Flap (Elekta) and the Nova Surface (Adaptiiv Medical Technologies). For each applicator, the distance between catheter centers and the skin surface was quantified. Dosimetric accuracy was assessed using gamma index analysis of radiochromic film (Gafchromic EBT4) measurements.

The radiological response of each component of the Montreal Mail applicator was found to be comparable to that of human tissues. The variability in source-to-skin distance was quantified using the interquartile range, which measured 1.8 mm for the Freiburg Flap, 1.4 mm for the Montreal Mail, and 0.6 mm for the Nova Surface applicator. Film-based dosimetric analysis demonstrated that all three applicators achieved gamma index passing rates above 96%, using the 3%/3 mm criterion relative to the planned dose distribution.

This study demonstrates that the Montreal Mail applicator is a practical solution that performs comparably to reference clinical devices in terms of surface adhesion and dose delivery. Moreover, its modular design offers a novel approach with the potential to enhance clinical efficiency.