Speaker
Description
Developed within the Medipix4 Collaboration, the Timepix4 ASIC is a versatile hybrid pixel detector featuring a 448×512 pixel matrix with 55 µm pitch and supporting both data-driven and frame-based readout [1], making it suitable for photon-counting and spectrally resolved imaging. This contribution describes the implementation and performance evaluation of Timepix4 assemblies equipped with GaAs and CdTe sensors at the INFN-PEPI facility in Trieste [2]. This laboratory is equipped with a compact micro Computed Tomography (μCT) system that allows the use of different detectors (see Fig. 1a for the setup configuration) and has been extensively used for spectral CT studies [3,4].
After a thorough characterization of a 500 µm-thick GaAs assembly operated in frame-based mode at INFN Ferrara [4], the detector was integrated into the PEPI setup. μCT scans of test phantoms (QRM μCT bar-pattern, see Fig. 1b) and sample objects (coffee bean, see Fig. 1c) were carried out in frame-based mode, achieving isotropic voxel sizes of a few tens of micrometers with scan times of a few hours, compatible with standard laboratory workflows.
In parallel, the spectroscopic imaging capabilities were investigated using a previously characterized 1 mm-thick CdTe-Timepix4 assembly. In data-driven mode, the detector records individual photon interactions together with their Time-of-Arrival and energy-related Time-over-Threshold information. A dedicated clustering pipeline using the framework DataPix4 [6] was implemented to mitigate charge-sharing and fluorescence escape effects, enabling the first full-spectral μCT scans acquired with Timepix4. System performance was assessed using a multi-material phantom containing silver, iodine, and gadolinium. By applying basis material decomposition to the reconstructed energy-resolved datasets, the three contrast agents were successfully separated in three dimensions, as illustrated in Fig. 2.
In conclusion, these studies show that Timepix4 can already support both frame-based and data-driven μCT in the laboratory. This is a first step toward a combined approach in which a high-resolution frame-based scan is used to recover morphology, while a data-driven single scan provides spectral information that can be overlaid on the same volume.
[1] X. Llopart et al., Journal of Instrumentation, 17 (2022) C01044.
[2] L Brombal et al. Scientific Reports 13 (2023) 4206.
[3] S. Fantoni et al. European Physics Journal Plus 139 (2024) 735.
[4] V. Di Trapani et al. Optics Express 30 (2022) 42995-43011.
[5] S. Velardita et al., Journal of Instrumentation, 21 (2026) C01023.
[6] V. Cavallini et al., Computer Physics Communications, 313 (2025) 109658.
Acknowledgements
This work was supported by the TIMEPIX4 project funded by the INFN-CSN5. We also acknowledge financial support under the National Recovery and Resilience Plan (PNRR), Mission 4, Component 2, Investment 1.1, Call for tender No. 1409 published on 14.9.2022 by the Italian Ministry of University and Research (MUR), funded by the European Union – NextGenerationEU – Project P2022X5ALY – CUP J53D23014070001- Grant Assignment Decree No. 1383 adopted on 1.9.2023 by the MUR.