Development of integration mode proton imaging with a single CMOS detector for a small animal irradiation platform

Schnürle, Katrin ; Bortfeldt, Jonathan ; Englbrecht, Franz Siegfried ; Gianoli, Chiara; Hartmann, Jens; Hofverberg, Petter; Meyer, Sebastian ; Niepel, Katharina; Yohannes, Indra; Vidal, Marie; Landry, Guillaume ; Herault, Joel ; Schreiber, Jörg ; Parodi, Katia und Würl, Matthias (12. Januar 2023): Development of integration mode proton imaging with a single CMOS detector for a small animal irradiation platform. In: Frontiers in Physics, Bd. 10, 1044156.

Abstract

A novel irradiation platform for preclinical proton therapy studies foresees proton imaging for accurate setup and treatment planning. Imaging at modern synchrocyclotron-based proton therapy centers with high instantaneous particle flux is possible with an integration mode setup. The aim of this work is to determine an object’s water-equivalent thickness (WET) with a commercially available large-area CMOS sensor. Image contrast is achieved by recording the proton energy deposition in detector pixels for several incoming beam energies (here, called probing energies) and applying a signal decomposition method that retrieves the water-equivalent thickness. A single planar 114 mm × 65 mm CMOS sensor (49.5 µm pixel pitch) was used for this study, aimed at small-animal imaging. In experimental campaigns, at two isochronous cyclotron-based facilities, probing energies suitable for small-animal-sized objects were produced once with built-in energy layer switching and the other time, using a custom degrader wheel. To assess water-equivalent thickness accuracy, a micro-CT calibration phantom with 10 inserts of tissue-mimicking materials was imaged at three phantom-to-detector distances: 3 mm, 13 mm, and 33 mm. For 3 mm and 13 mm phantom-to-detector distance, the average water-equivalent thickness error compared to the ground truth was about 1 and the spatial resolution was 0.16(3) mm and 0.47(2) mm, respectively. For the largest separation distance of 33 mm air gap, proton scattering had considerable impact and the water-equivalent thickness relative error increased to 30, and the spatial resolution was larger than 1.75 mm. We conclude that a pixelated CMOS detector with dedicated post-processing methods can enable fast proton radiographic imaging in a simple and compact setup for small-animal-sized objects with high water-equivalent thickness accuracy and spatial resolution for reasonable phantom-to-detector distances.

• Dokumententyp: Zeitschriftenartikel
• EU Funded Grant Agreement Number: 725539
• EU-Projekte: Horizon 2020 > ERC Grants > ERC Consolidator Grant > ERC Grant 725539: SIRMIO - Small Animal Ion Irradiator for Research in Molecular Image-Guided Radio-Oncology
• Publikationsform: Publisher's Version
• Keywords: proton imaging; small animal; particle therapy; integration mode; CMOS
• Fakultät: Physik
• Themengebiete: 500 Naturwissenschaften und Mathematik > 530 Physik ; 600 Technik, Medizin, angewandte Wissenschaften > 610 Medizin und Gesundheit
• ISSN: 2296-424X
• Sprache: Englisch