Speaker
Description
The INFN SPECTRE (Single Photon Emission Computed Tomography Readout Electronics) project aims to design, assemble, and characterize a complete detection module based on CZT sensors for medical applications. For readout, SPECTRE uses the electronics developed for a high-capacitance gas detector (CGEM@BESIII, IHEP, Beijing): the TIGER (Torino Integrated GEM Electronics for Readout) ASIC for on-detector electronics and the off-detector FPGA-based GEMROC module for power and data processing. The readout circuit is compact, modular, and meets the high-speed requirements of CZT sensors, with the advantage of scalability. We present the CZT detection module and initial results of its characterization using X-rays.
Summary (500 words)
The INFN SPECTRE (Single Photon Emission Computed Tomography Readout Electronics) project aims to design, assemble, and characterize a complete detection module based on CZT sensors for medical applications. SPECT has been an established imaging technique in nuclear medicine for many years. Hal Anger's gamma camera is the reference system and is based on the indirect conversion of gamma rays to electrons by low-energy photons. In contrast, semiconductor materials convert gamma photons directly into electrical signals. Cadmium telluride (CdTe) and Cadmium Zinc Telluride (CZT) are among the most established room-temperature semiconductors for ionizing radiation detection. As the demand for SPECT systems with higher spatial resolution, energy resolution, and sensitivity continues to grow, there is an increasing need to develop high-performance CZT detectors with small pixels and corresponding high-speed readout electronics [1,2].
For readout, SPECTRE uses electronics developed for a high-capacitance gas detector (CGEM@BESIII, IHEP, Beijing [3]): the TIGER (Torino Integrated GEM Electronics for Readout) ASIC for on-detector electronics and the off-detector FPGA-based GEMROC module for power and data processing [4]. TIGER is a mixed-signal chip with 64 channels on an area of 5 × 5 mm². Each channel has a complete readout chain with amplification, signal conditioning, and discrimination, as well as a data payload containing the time and charge information for each event. TIGER is versatile for the readout of radiation sensors up to 50 fC and for high rates up to 70 kHz. The TIGER/GEMROC readout circuit is compact, modular, scalable, and highly customizable.
In typical CZT applications today, spectroscopic systems operate at rates of about 1 kcps/mm² because extracting energy information requires more processing time [5]. However, our system can acquire each sensor pixel at a rate of up to 70 kHz, or approximately 16 kcps/mm². This can lead to a significant reduction in patient exposure during examinations and a significant improvement in sensitivity, as image artifacts are reduced, given that the proposed readout exceeds the improvement already observed with CZT/SPECT technology compared to conventional SPECT.
In this presentation, we will cover all phases of the project to date, including CZT sensor and electronics simulation with the Allpix Squared package [6], based on Geant4, current-voltage characterization of the CZT sensors, system design and construction, assembly of four modules onto an adapter board, and initial system characterization using X-rays.
[1] Ritt P., 2022-Recent Developments in SPECT/CT, doi:10.1053/j.semnuclmed.2022.01.004
[2] Israel O. et al., 2019- Two decades of SPECT/CT – the coming of age of a technology: An updated review of literature evidence, DOI:10.1007/s00259-019-04404-6
[3] Melendi FM on behalf of the CGEM-IT Working Group, 2026 The CGEM-IT detector of the BESIII experiment JINST 21 C01045
[4] Amoroso A et al 2021 The CGEM-IT readout chain JINST 16 P08065
[5] Nakanishi K. et al., 2024-A simple method to shorten the apparent dead time in the dosimetry of Lu-177 for targeted radionuclide therapy using a gamma camera, DOI: 10.1016/j.ejmp.2024.103298
[6] https://allpix-squared.docs.cern.ch/