PUBLICATIONS
A place where ideas take shape and become publications—shared and created together with other authors.
Asymmetric Data Acquisition System for an Endoscopic PET-US Detector
Current studies on pancreatic cancer prognosis show that survival remains very low (around 6%), mainly due to late detection. To improve diagnosis, the EndoTOFPET-US project proposes a multimodal imaging technique for endoscopic examination of the pancreas, combining the high metabolic resolution of time-of-flight positron emission tomography (TOF-PET) with anatomical information from ultrasound (US).
The developed system includes two innovative detectors: one integrated into an ultrasound endoscope and another placed on the patient’s abdomen. Both produce distinct data streams that must be handled by a high-performance data acquisition (DAQ) system.
To manage this complexity, a distributed DAQ with multiple triggering levels is implemented, split between the detector electronics and an external reconstruction system. Results obtained with prototypes show that this approach is suitable for such applications and has potential for other systems with asymmetric data.
Performance evaluation of a PET/MR detector based on the ClearPEM technology
This work presents performance results for a PET detector prototype operating simultaneously inside a 7 tesla magnetic resonance system. The detectors are based on ClearPEM technology, designed for high-resolution imaging (especially breast) and compatible with combined PET/MR systems at very high magnetic fields.
To avoid electromagnetic interference between the two systems, the PET detectors and their electronics were carefully shielded, and a dedicated radiofrequency coil was designed to reduce electromagnetic coupling.
Noise measurements showed that although some interference exists between the RF signal and digital noise, shielding is highly effective. In addition, simultaneous tests with radioactive sources and experimental phantoms showed no distortion in MR images and no loss of PET detector performance.
In conclusion, both systems can operate at the same time without significant electromagnetic interference.
EndoTOFPET-US DAQ, designing the Data Acquisition System of a high resolution endoscopic PET-US detector
The EndoTOFPET-US project aims to develop a multimodal imaging technique for endoscopic examination of the pancreas and prostate, combining high-resolution metabolic information from time-of-flight positron emission tomography (TOF-PET) with anatomical information from ultrasound.
This PET system, tailored to regions of interest with an asymmetric architecture, requires a high-performance data acquisition (DAQ) system capable of managing multiple event-trigger levels and controlling different detectors in real time.
The paper presents an overview of the EndoTOFPET-US detector, focusing on DAQ-related aspects. It also analyzes the design of this system in detail, discussing key considerations and evaluating performance from tests with final prototypes of its components.
Validation of a highly integrated SiPM readout system with a TOF-PET demonstrator
Highly integrated, fast, compact readout electronics were developed for TOF-PET scanners based on silicon photomultipliers (SiPM). The system uses a dedicated integrated circuit (PETsys TOFPET1 ASIC) with 64 channels, each with amplifier, discriminator, time-to-digital converter (TDC), and amplitude measurement via time over threshold (TOT), achieving very high time resolution (25 ps).
The system is optimized for high data rates, good timing accuracy, low power, and low cost. For validation, a PET scanner prototype with 2,048 SiPM channels was built from 16 detector modules. Each module includes two ASICs reading 128 pixels coupled to LYSO crystals.
The data acquisition (DAQ) system collects data via front-end boards that aggregate information and send it to a DAQ board connected to a computer over PCIe. Results from this prototype demonstrate strong system performance.
EndoTOFPET-US data acquisition system
The EndoTOFPET-US system is a multimodal imaging technology that combines time-of-flight PET (200 ps resolution) and ultrasound in an endoscopic probe. The PET system has an asymmetric configuration with two detectors: an internal probe detector with very small LYSO crystals coupled to digital SiPMs, and an external plate detector on the body with larger crystals and SiPMs read out by a 64-channel ASIC.
The data acquisition (DAQ) system is compact and uses reconfigurable digital electronics. FPGAs on the front end collect event data and send it to a trigger system implemented on a PCIe card inside the computer. Part of the event processing runs directly on the trigger FPGA, while more complex analysis is done in software.
The system can handle high data rates, up to 40 MHz from the external detector and 200 kHz from the probe, demonstrating its ability to operate in demanding environments.
Asymmetric Data Acquisition System for an endoscopic PET-US detector
Current studies on pancreatic cancer show that survival remains very low (around 6%), mainly due to late detection. To improve diagnosis, the EndoTOFPET-US project proposes a multimodal imaging technique for endoscopic examination that combines high-resolution metabolic information from TOF-PET with anatomical information from ultrasound.
A system with these characteristics requires a high-performance data acquisition (DAQ) system designed specifically to control and collect information from two different detectors efficiently.
Oblique Incidence Design of Meander-Line Polarizers for Dielectric Lens Antennas
A method is presented for designing multilayer planar polarizers with meander-line patterns. It combines transmission-line theory with electromagnetic analysis of unit cells in the frequency domain, simplifying the design process and avoiding complex optimizations.
The technique targets polarizers used in lens antennas and is valid for waves incident from different angles. To validate the method, two Ka-band polarizers were fabricated: one for normal incidence and one for oblique incidence.
Results include design, prototypes, and measurements on a complete lens antenna system, demonstrating the effectiveness of the proposed method.
Circularly polarized multi-beam lens antenna system. Comparison between 2 polarizers
Two Ka-band circularly polarized multibeam antenna systems are compared. In both cases the system consists of a dielectric lens fed by circular waveguides with small horns.
The main difference is how circular polarization is achieved: in one case via a polarizer integrated in the waveguide, and in the other via a meander-line polarizer placed outside the lens, for which an analytical design model is proposed.
Both systems were analyzed, fabricated, and measured, showing similar results. In both cases axial ratio below 3 dB is achieved over a 19% bandwidth, indicating good circular polarization performance.
A free-running, time-based readout method for particle detectors
In the EndoTOFPET-US experiment, the TOFPET ASIC was developed as readout electronics for silicon photomultipliers (SiPM). This chip enables time-of-flight information in PET scanners, helping reduce radiation dose to patients. It is designed for high event rates (up to 100 kHz) and offers high time resolution (50 ps). It also uses dual thresholds for accurate signal measurement and noise reduction, and can estimate signal charge via time over threshold (TOT).
The PASTA chip, used in the PANDA high-energy physics experiment, follows a similar time-based approach. It is employed in a silicon vertex detector for particle tracking. Although it shares the same philosophy as the TOFPET ASIC, it differs in important ways, such as amplification stages adapted to different signal types and protection for high-radiation environments.
Overall, both chips stand out for efficient, low-power, compact designs suited to demanding systems.
Design and performance of an ASIC for TOF applications
A low-power ASIC for SiPM readout in time-of-flight (TOF) applications was developed within the EndoTOFPET-US project. The chip integrates signal conditioning, discrimination circuits, and high-performance time-to-digital converters (TDCs) on 64 independent channels, with fully digital output and a target resolution of 25 ps.
This work presents preliminary results from electrical characterization and tests with SiPM arrays coupled to LYSO crystals. Intrinsic TDC jitter was measured at 21 ps. Testing an SiPM with a pulsed laser yielded 110 ps resolution for single photons and 32 ps when many photons are detected, showing high system performance.
Detection sensitivity and light collection studies of an APD-based high packing-fraction LYSO:Ce matrix for PET applications
ClearPEM is a dedicated APD-based PET detector designed for high-resolution imaging in breast cancer. Each detector module consists of 12 LYSO:Ce crystal matrices, each with 4×8 individual crystals (2×2×20 mm³), optically coupled at both ends to Hamamatsu S8550 APD arrays for scintillation light detection. Currently only 46% of the sensitive area is occupied by crystals, due to gaps between APD matrices, encapsulation, and BaSO₄ reflective walls.
To improve overall sensitivity, a new compact matrix geometry was designed, increasing the sensitive area fraction to 76% using crystals of three different sizes. This configuration requires studying how coincidence factors between crystals and APDs affect energy and time resolution, optical coupling between crystals, and depth-of-interaction capability.
The paper presents an experimental study of sensitivity improvement with the new compact matrix and its effect on overall detector performance.
EndoTOFPET-US: a novel multimodal tool for endoscopy and positron emission tomography
The EndoTOFPET-US project seeks to develop a multimodal detector to support creation of new biomarkers in prostate and pancreatic tumors. The detector has two main components: an external plate and a PET extension for an endoscopic ultrasound probe.
The external plate consists of an array of LYSO crystals read out by silicon photomultipliers (SiPMs) coupled to a dedicated integrated circuit (ASIC). The internal probe will be a highly integrated, miniaturized detector with LYSO crystals read by fully digital SiPMs combining photon sensors and digital readout on a single chip.
The position and orientation of both detectors will be tracked relative to the patient, enabling fusion of PET metabolic images with ultrasound anatomical images during the procedure. This combined information can guide further interventions such as biopsies or in vivo confocal microscopy.
Development of high-resolution detector module with depth of interaction identification for positron emission tomography
A high-resolution, time-of-flight (TOF) detector module suitable for small-footprint, commercially viable PET was developed. A novel approach encodes depth of interaction (DOI) in pixelated crystal matrices using single-sided readout and 4-to-1 coupling between scintillators and photodetectors. DOI information is estimated via light sharing.
The detector module consists of an 8×8 array of 1.53×1.53×15 mm³ LYSO crystals with optically ground side surfaces separated by reflective foils. The matrix is coupled to a 4×4 silicon photomultiplier (SiPM) array and read out by a high-performance ASIC with TDC capability (50 ps time resolution).
Results show excellent identification of all crystals in the matrix, 530 ps timing resolution, 5.17 mm FWHM average DOI resolution, and 18.29% FWHM average energy resolution.
A compact Detector Module for Time of Flight PET and the associated DAQ system
Within the EndoTOFPET-US project, a compact time-of-flight (TOF) PET detector module was developed integrating 128 gamma-ray detection pixels formed by 3.5×3.5×15 mm³ LYSO crystals coupled to MPPC photodetectors.
The module includes two 64-channel ASICs, each integrating signal conditioning, discrimination circuits, and high-performance per-channel TDCs with 25 ps r.m.s. intrinsic resolution and fully digital output (up to 640 Mb/s).
The data acquisition (DAQ) system uses front-end boards, each collecting data from 1024 channels (8 detector modules), transmitting assembled data over an electrical serial link (1.6 Gbps) or two high-speed optical links (2×6.4 Gb/s) to a single DAQ board connected to the acquisition computer’s PCIe bus.
The paper presents the detector module design and preliminary characterization results together with the associated DAQ system.