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

Project description and contents of the submitted manuscript:

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, i.e. to trackends. 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 FC for replacement of a traditional FC and a 2×2 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 optimizied 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 single-channel FC corresponded qualitatively to the one of a traditional FC. A 2 × 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 track-end detectors in anthropomorphic phantoms.

Shared files:

2x2_FC_matrix: design CAD files of FC array

Single_channel_FC: design CAD files of simplified, single-channel FC

CT_matrix: high-resolution x-ray CT image set of the 2x2 FC array

Measured_values_for_MedPhys_technical_note: Excel sheet of the data presented in the paper