Time Of Flight PET is a promising technique that can improve the image quality of a PET scanner. A TOF PET detector must be designed by optimizing its energy and time resolution. Present study aims to assess the overall performances of a detector composed by LSO:Ce,Ca crystal coupled with SiPM, connected to a transimpedence amplifier. Simulation and measurements have been performed focusing on the influence of the Ca codoping concentration in the detector energy and time resolution.

CMOS multichannel front-end electronics suitable for Silicon Photomultiplier detectors has been developed, mainly intended for medical imaging applications. The architecture of the analog channel, DC coupled to the detector, is based on a full current-mode approach, which allows to achieve a wide input dynamic range of about 70pC while retaining very fast self-triggering capabilities. An 8-channel ASIC with on-chip ADC and a 32-channel prototype have been designed and manufactured, both featuring serial and sparse readout capabilities and a fast-OR circuit, able to generate a high-speed trigger signal from the discriminator outputs of the analog channels. Measurements obtained by coupling the 8-channel prototypes to an injection capacitance have been carried out for characterization purposes. The circuit has been also used to read-out SiPMs coupled to different kinds of light sources, such as a blue LED and a small LYSO scintillation crystal excited by gamma photons with different energies. The results obtained from these tests are presented and discussed, confirming the effectiveness of the proposed front-end architecture.

Cardiovascular diseases are the most common cause of death in western countries. Understanding the rupture of vulnerable atherosclerotic plaques and monitoring the effect of innovative therapies of heart failure is of fundamental importance. A flexible, high resolution, high sensitivity detector system for molecular imaging with radionuclides on small animal models has been designed for this aim. A prototype has been built using tungsten pinhole and LaBr3(Ce) scintillator coupled to Hamamatsu Flat Panel PMTs. Compact individual-channel readout has been designed, built and tested. Measurements with phantoms as well as pilot studies on mice have been performed, the results show that the myocardial perfusion in mice can be determined with sufficient precision. The detector will be improved replacing the Hamamatsu Flat Panel with Silicon Photomultipliers (SiPMs) to allow integration of the system with MRI scanners. Application of LaBr3(Ce) scintillator coupled to photosensor with high photon detection efficiency and excellent energy resolution will allow dual-label imaging to monitor simultaneously the cardiac perfusion and the molecular targets under investigation during the heart therapy.

As a result of a comprehensive study aimed at the development of integrated front-end electronics suitable for Silicon Photomultiplier detectors, a 32-channel self-triggered ASIC has been designed in a standard 0.35μm CMOS technology. Characterization measurements, carried out exploiting an external injection capacitance, demonstrate that the architecture of the analog channel, based on a full current-mode approach, allows to achieve very good performance in terms of dynamic range (around 70pC), bandwidth and timing accuracy (σ@118ps). The ASIC has been used in self-triggered mode to read-out a SiPM from Hamamatsu, coupled to a small LYSO scintillator, and the resulting spectra obtained by exposing the detector to different radiation sources confirm the effectiveness of our design approach. Eventually, some modifications to the architecture of the ASIC are proposed to improve its performance in the detection of low light levels and to enhance the effectiveness of the sparse read-out acquisition mode. These new features have been implemented in a further version of the ASIC, containing also an 8-bit, 20Ms/s embedded ADC designed on purpose, which has been already submitted for fabrication.

Introduction: We describe an open and flexible detector system for studying cardiovascular diseases on mice, namely the detection of atherosclerotic plaques and stem cell therapy of heart infarction. Tests with a prototype on phantom, perfusion SPECT imaging on mice, with different routes of the radiotracer and detection of atherosclerotic plaques on mice have been performed. Methods: A Geant4 code has been used to design a detector system optimized for studying cardiovascular disease on mice, open and flexible enough to be able to host detectors with different modalities (MRI). In order to perform test measurements on detection of atherosclerotic plaques and on perfusion SPECT imaging of mouse heart two prototype modules of the detector made of CsI (Tl) and NaI (Tl) pixellated scintillators coupled to pinhole collimators and PSPMTs. A readout electronics capable of reading out 4096 channels individually at 10-20 KHz was specifically designed and built. Results: Tests performed on phantom show a spatial resolution of 0.8 mm. It can be improved down to 0.3 mm as tradeoff with needed sensitivity. Measurement on transgenic mice after injection of 99Tc-AnnexinV showed suspicious focal activity indicating possible plaques. Myocardial perfusion SPECT study with two different routes of delivery (tail vein and peritoneum) showed that also injecting the radiotracer trough the peritoneum gives good images making possible the use of this technique to monitor the effects of stem cell therapy of infarction on mice. To fully accomplish the objectives of the study will probably require the integration of other modalities (MRI) with significant modifications of the layout, and of the materials and components.

An 8-bit Analog-to-Digital Converter (ADC), suitable to be integrated in multi-channel ASICs for the read-out of SiPM arrays, has been designed in a standard 0.35mm CMOS process. The circuit implements two 8-bit interleaved ADCs with a two-step flash architecture. Each ADC has a sub-ranging mode of operation, and the overall frequency of conversion is of 20MHz. Clock boosting techniques have been exploited to improve the performance of the transmission gates used as switches and a pre-coarse conversion phase has been introduced to improve the conversion accuracy for signals close to the limits of the input dynamic range. Much care has been devoted to the design of the resistor ladder used to generate the voltage references for the comparators. In particular a statistical approach has been adopted to optimize the standard deviations of the voltage references due to resistor mismatch. A test chip containing a prototype of the ADC has been manufactured and the first characterization measurements are here presented and discussed.

The design and first test results of new readout electronics for a Multi Anode PhotoMultiplier Tube (MAPMT) array is reported. The system has been developed to perform the readout of arrays of 64 or 256-channels MAPMTs, used in single photon imaging applications, such as Single Photon Emission Computed Tomography (SPECT) for medical studies on stem cells or clinical diagnosis of breast-cancer.

The Hall A RICH at Jefferson Lab is undergoing an upgrade to adapt to the higher momentum kinematics of the neutron spin structure Transversity experiments planned to run in 2008.The JLab RICH is a proximity focusing detector using liquid C6F14 as Cherenkov radiator, a thin layer of CsI as photon converter, evaporated on segmented pad panels of a proportional chamber. The original RICH had a superior hadron identification up to 2 GeV/c with pion/kaon rejection at the level of 1:1000 at similar to 90% intrinsic efficiency. The upgrade will extend this performance above 2.4 GeV/c by means of a larger photon detector (a multiwire-multipad proportional chamber) and a longer proximity gap which will improve the photon detection geometrical efficiency and the angular resolution, respectively. (C) 2008 Elsevier B.V. All rights reserved.

We describe the design, fabrication and test results of a segmented Hybrid Photon Detector with integrated auto-triggering front-end electronics. Both the photodetector and its VLSI readout electronics are custom designed and have been tailored to the requirements of a recently proposed novel geometrical concept of a Positron Emission Tomograph. Emphasis is laid on the PET specific features of the device. The detector has been fabricated in the photocathode facility at CERN.

The design of a data acquisition system (DAQ) for a positron emission tomography scanner is reported. The PET system, based on long axially oriented scintillation crystals, read out by hybrid photon detectors (HPD), allows 3D parallax-error free Compton enhanced gamma reconstruction. The DAQ system is composed of several readout cards, each one associated with a module of the PET scanner, and of a main card that controls the whole system. Using fast triggering signals from the silicon sensor backplanes, the main card performs the coincidence analysis and, in case of coincidence, it enables the read-out of the two modules involved. The other modules are left free to perform new acquisitions. This concept based on several independent, events driven and parallel read-out chains, drastically reduces the acquisition dead time. The DAQ system here reported, designed for a two module demonstrator set-up, was developed to study and optimize the essential design parameters

We describe the design, fabrication and test results of a segmented hybrid photon detector with integrated auto-triggering front-end electronics. Both the photodetector and its VLSI readout electronics are custom designed and have been tailored to the requirements of a recently proposed novel geometrical concept of a positron emission tomograph. Emphasis is put on the PET-specific features of the device. The detector has been fabricated in the photocathode facility at CERN.