Showing papers by "Matteo Perenzoni published in 2013"

An 8×16-pixel 92kSPAD time-resolved sensor with on-pixel 64ps 12b TDC and 100MS/s real-time energy histogramming in 0.13µm CIS technology for PET/MRI applications

Abstract: Positron-Emission Tomography (PET) is a nuclear imaging technique that provides functional 3-dimensional images of the body, finding its key applications in clinical oncology and brain-function analyses. The typical PET scanner is composed of a ring of scintillator crystals that absorb gamma rays and emit photons as a result, coupled to photon-sensing devices. The photons hit the sensors with a certain spread in space and time, depending on the material and geometry of the crystals. The sensors must then estimate the energy, the time of arrival (ToA), and the axial position of incoming gamma rays. Most commercially available scanners use photomultiplier tubes (PMTs), which are sensitive to magnetic fields, as the sensing element, making the integration of these systems with Magnetic-Resonance Imaging (MRI) impossible. A significant amount of research has focused on replacing PMTs with solid-state detectors, such as Silicon photomultipliers (SiPMs) [1], which can be integrated with MRI while maintaining the high-sensitivity of PMTs.

SPADnet: A fully digital, networked approach to MRI compatible PET systems based on deep-submicron CMOS technology

Abstract: This paper is the first comprehensive presentation of the SPADnet concept. SPADnet is a fully digital, networked MRI compatible time-of-flight PET system, exploiting the speed and integration density of deep-submicron CMOS technologies. The core enabling technologics of SPADnet are a sensor device comprising an array of 8×16 pixels, each composed of 4 mini-SiPMs with in situ time-to-digital conversion, a multi-ring network to filter, carry, and process data produced by the sensor devices at 2Gbps, and a 130nm CMOS process enabling mass-production of photonic modules that are optically interfaced to scintillator crystals. The SPADnet photonic modules comprise a matrix of tightly packed sensor devices; each module is networked in multiple rings, where coincidence pairs are identified and readily used in reconstruction algorithms, enabling scalable, MRI compatible pre-clinical PET systems for multi-modal imaging.

First characterization of the SPADnet sensor: a digital silicon photomultiplier for PET applications

Abstract: Silicon Photomultipliers have the ability to replace photomultiplier tubes when used as light sensors in scintillation gamma-ray detectors. Their timing properties, compactness, and magnetic field compatibility make them interesting for use in Time-of-Flight Magnetic Resonance Imaging compatible Positron Emission Tomography. In this paper, we present a new fully digital Single Photon Avalanche Diode (SPAD) based detector fabricated in CMOS image sensor technol- ogy. It contains 16x8 pixels with a pitch of 610x571.2 mm 2 .

A 92k SPAD Time-Resolved Sensor in 0.13μm CIS Technology for PET/MRI Applications

Abstract: This paper presents a 92k SPAD, 16×8 pixel sensor for PET imaging, implemented in 0.13μm low voltage CIS technology. Within each pixel, 720 SPAD s are organized into high fill factor mini-SiPMs placed around a central logic block. The sensor demonstrates a ne w architecture for this application, providing a 100Msamples/s real time energy histogramming capability, as well as an on-chip discriminator for the recognition of gamma events and integration control for the automatic acquisition of event data. Preliminar y gamma measurements demonstrate an energy resolution of 13.1% at 20oC, improving to 11.3% at -20oC.

Complete characterization of SPADnet-I - a digital 8×16 SiPM array for PET applications

Abstract: This paper presents the complete gamma characterization of the SPADnet-I sensor, a novel, fully digital SiPM array for PET applications. Each SPADnet-I pixel contains 720 SPADs and counting and timestamping logic, resulting in pixel dimensions of 0.6 × 0.6 mm2 and 42.6% fill-factor. Moreover, the sensor provides a real-time output of the total detected energy at up to 100 Msamples/s, which is internally used by a discriminator to distinguish gamma events from background noise. Results for the pile-up identification, crystal image and discriminator efficiency are presented. An energy resolution of 10.8% and a coincidence resolution time of 288 ps are reported.

Analysis of CMOS 0.13µm test structures for 0.6 to 1.5 THz imaging

Abstract: Test structures comprehending several combinations of FET detector sizes and bow-tie antennas were designed and fabricated in a 0.13 μm standard CMOS technology. Measurement results from these structures provide a quantitative comparison basis for the design of a future real-time high-frame rate THz camera, providing an insight on the optimization of the FET size.

Effects of DCR, PDE and saturation on the energy resolution of digital SiPMs for PET

Abstract: In this paper, we use the SPADnet-I sensor, a fully digital 8×16 SiPM array with per-SPAD SRAMs, to analyze the effects of photon detection efficiency (PDE), dark count rate (DCR) and saturation on the energy resolution of PET systems We show that the mini-SiPM compression schemes of SPADnet-I result in a total photon loss of about 6% for a 511 keV gamma scintillation in a 3×3×5 mm3 LYSO crystal The behavior of the sensor energy resolution with respect to variations in PDE and DCR is measured and modeled The optimum operation point is found to be at circa 4% of the high-DCR SPADs disabled, resulting in 106% energy resolution Moreover, from the described model, we show that integrating per-SPAD SRAMs on-chip actually has a negative effect in the sensor energy resolution, as the DCR decrease is not sufficient to compensate the reduced fill-factor Finally, we show that below a certain level of DCR, the optimum operation point shifts to 100% of the SPADs enabled, completely eliminating any gains from integrating per-SPAD SRAMs

Characterizing single- and multiple-timestamp time of arrival estimators with digital SiPM PET detectors

Abstract: In this paper, we make use of a recently proposed fully digital 8×16 SiPM array with per-pixel time-to-digital converters (TDCs), the SPADnet-I, to compare hardware-friendly, single- and multiple-timestamp time-of-arrival (ToA) estimators for PET Two SPADnet-I sensors are used in coincidence, each coupled to a 3×3×5 mm3 LYSO crystal wrapped in Teflon We acquired and processed 100k coincidence events to extract the coincidence resolving time (CRT) of the system Pre-processing steps were applied to the data to remove low-energy events and correct the TDC values Results show a 8% improvement in CRT of the suggested multiple timestamp estimator with respect to the best performing single-timestamp estimator (from 313 ps to 288 ps)

Electronics-Based 3D Sensors

Abstract: The conventional photodiode, available in every CMOS process as a PN junction, can be enriched by smart electronics and therefore achieve interesting performance in the implementation of 3D Time-Of-Flight imagers. The high level of integration of deep submicron technologies allows the realization of 3D pixels with interesting features while keeping reasonable fill-factors.