Proof-of-principle of 3D-printed track-end detectors for dosimetry in proton therapy

Background: Dosimetric equipment in particle therapy (PT) is associated with high costs. There is a lack of versatile, tissue-equivalent detectors suitable for in-vivo dosimetry. Faraday-cup (FC) type detectors are sensitive to stopped protons, that is, to track-ends (TEs). They experience a renaissance in PT as they can cope with high dose rates. Owing to their simple functional principle, production of FC could benefit from the dynamic technological developments in additive manufacturing of sensors.

Purpose: To build FC-type detectors for PT by standard 3D-printing. This study seeks to build an integrating, single-channel (SC) FC for replacement of a traditional FC and a $2\times 2$ array of FC elements indicating the feasibility of a spatially resolving detector.

Methods: Samples of FCs were produced with a dual-extruder 3D-printer with polylactic-acid filaments, which contained graphite in the conductive parts of the detector. Production was optimized in terms of materials and printing temperature. Samples were characterized by electrical tests and non-destructive 3D x-ray imaging. Beam tests were conducted at a clinical PT machine.

Results: Operational FC-type detectors for proton fields were printed. The detected charge of the SC FC corresponded qualitatively to the one of a traditional FC. A $2\times 2$ FC array was fabricated in a single run. There was a linear relationship between the response of the individual FC elements and the machine output.

Conclusions: 3D-printing is a viable method for producing low-cost, tissue-equivalent, FC-type detectors for PT. They could potentially be used as TE detectors in anthropomorphic phantoms.