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- Coincidence detection in PETPublication . ClemĂȘncio, Filomena; Landeck, JorgeA complex task for PET cameras is the design of a coincidence detection system that allows for a very tight time window. This brings us necessarily to discussing the concept of coincidence in PET (including the concepts of single, prompt and multiple events in a PET chamber), the different options for coincidence sorting and the concept of Field of View (FOV). We present results from a coincidence system we implemented in a Xilinx Virtex-5 FPGA with coincidence time windows of the order of a few hundred picoseconds and capable of FOV selection and multiple coincidence rejection implemented in real-time.
- An easy procedure for calibrating data acquisition systems using interleavingPublication . ClemĂȘncio, Filomena; Loureiro, CustĂłdio F. M.; Correia, Carlos M. B. A.Interleaving data acquisition channels is a well-known and interesting technique to achieve higher acquisition rates. However, to obtain the expected benefits, a careful look at the interleaving technique and to mismatches that can lead to unwanted harmonic distortion and noise is essential. In this paper we discuss the methods used to interleave existing high-speed, 250 MSPS 8-bit acquisition channels, and the results obtained. The methods presented allowed a good relative channel calibration in amplitude (amplitude mismatch under 0.1 lsb) and in time (time mismatch between acquisition channels in the ps range, under the specified maximum jitter for the ADC used). A dynamic, by software, amplitude level signal-dependent adjustment procedure is also suggested for signals with rich frequency content that can substantially improve the quality of the acquired signal when using interleaved channels. The techniques presented provide good results even in the presence of noise.
- The SHiP timing detector based on MRPCPublication . Blanco, Alberto; Franco, Celso; Loureiro, CustĂłdio; ClemĂȘncio, Filomena; Soares, Guilherme; Saraiva, JoĂŁo; Lopes, LuĂs; Leonardo, Nuno; Fonte, Paulo
- The design of a digital coincidence-detection trigger system for a RPC-based petPublication . ClemĂȘncio, Filomena M. C.; Loureiro, CustĂłdio F. M.; Correia, Carlos M. B. A.A complex task for PET cameras is the design of an appropriate coincidence-detection trigger as it usually encompasses coincidences in a large number of channels and tight time specifications. Those requirements are even greater for a resistive plate chamber (RPC)-based detector technology as the time window specification is quite small (in the order of a few hundred picoseconds) and the number of coincidence-channels can be quite large (more than 100 in a large camera). In this work we discuss on-going work aimed at implementing the coincidence-detection algorithm inside a FPGA along with the necessary TDCs. The use of the developed solution in a first prototype of an RPC-based small animal PET and its scalability to the case of a human, all-body, PET, is discussed.
- An easy procedure for calibrating data systems using interleavingPublication . ClemĂȘncio, Filomena; Loureiro, CustĂłdio F. M.; Correia, Carlos M. B. A.Interleaving data acquisition channels is a well-known and interesting technique to achieve higher acquisition rates. However, to obtain the expected benefits, a careful look at the interleaving technique and to mismatches that can lead to unwanted harmonic distortion and noise is essential. In this paper we discuss the methods used to interleave existing high-speed, 250 MSPS 8-bit acquisition channels, and the results obtained. The methods presented allowed a good channel calibration in amplitude (amplitude mismatch under 0.1 lsb) and in time (time mismatch between acquisition channels in the ps range, under the specified maximum jitter for the ADC used). A dynamic, by software, amplitude level signal-dependent adjustment procedure is also suggested for signals with reach frequency content that can substantially improve the quality of the acquired signal when using interleaved channels. The techniques presented provide good results even in the presence of noise.
- A fast, high-throughput digital coincidence detection system for a large RPC-PET cameraPublication . ClemĂȘncio, Filomena; Loureiro, C.F.M.; Landeck, J.Current work aiming at studying the feasibility of a resistive plate chamber (RPC)- PET camera for human whole-body screening indicates that a very cost-effective and highsensitivity camera can be built. Such a camera will use the high intrinsic time resolution (better than 300 ps full width at half maximum (FWHM) of the RPC technology to implement a time of flight (TOF)-PET camera that, along with its very large field of view, can reach a sensitivity exceeding the present crystal-based PET technology by a factor up to 20 with a spatial resolution near 2 mm. Due to the large number of RPC plates forming such a system (in the order of 100 RPC plates, or even more) and to the large amount of data generated it is essential to have an effective on-line trigger that helps reducing the pressure on the data saving and processing system. In this work we present simulation results of an all-digital coincidence-detection system implemented in a Field Programmable Gate Array (FPGA) that can cope with the task of generating the high speed trigger for such a camera. The method implemented for coincidence detection is vir tually dead-time free and very fast. It is shown the trigger system can process all the events inside the RPC-PET camera in real-time. This will allow a better understanding of the camera and will contribute to its optimization, simplifying significantly the design of its data acquisition system.
- Trigger system for a large area RPC TOF-trackerPublication . ClemĂȘncio, Filomena; Blanco, Alberto; Carolino, Nuno; Loureiro, Custodio F. M.The TOF-tracker concept, the simultaneous measurement of accurate time and bi-dimensional space coordinates in a single gaseous detector, has been previously demonstrated. Recently, a larger area, 1550Ă1250 mm 2 , RPC detector has been constructed. Signals are induced in metallic strips located in each side of the RPC active volume and coupled to both charge-sensitive and timing circuits, that can be used to generate a coincidence trigger. In this work, the architecture and performance of the trigger system of the detector is reported. The system is based on off-the-shelf inexpensive modules and in a custom program written in VHDL running in a Xilinx Spartan-6 FPGA. It is fast, fully parameterized and supports several trigger strategies, allowing at the same time the collection of several information referring to the operating condition of the detector, relevant for tests and detector maintenance.
- Online trigger processing for a small-animal RPC-PET cameraPublication . ClemĂȘncio, Filomena M. C.; Loureiro, CustĂłdio F. M.; Landeck, JorgeA complex task for positron emission tomography (PET) cameras is the design of an appropriate coincidence-detec tion trigger system as it usually encompasses coincidences in a large number of channels and requires tight time specifications. Those requirements are even greater for a resistive plate chamber (RPC)-based detector technology since the time window specifica tion is quite small (in the order of a few hundred picoseconds) and the number of coincidence-channels can be quite large. Previous work showed that the time resolution for gamma photon pairs of a detector based on resistive plate chamber technology is under 300 ps full width at half maximum. This allows for a very tight time window for coincidence detection, with the corresponding benefits in reducing the number of random coincidences observed and, hence, the overall noise on the acquired image. In this paper, we first show experimental results of a coincidence-detection algo rithm implemented inside a Xilinx Virtex-5 field-programmable gate array for a small-animal RPC-PET camera being built.
- A data acquisition architecture for a RPC-based small animal petPublication . ClemĂȘncio, Filomena; Loureiro, CustĂłdio F. M.; Correia, Carlos M. B. A.On-going work suggests that a RPC-based small animal pet camera can be built with a FWHM resolution below 0.5 mm and at a very competitive cost. The camera being developed demands a high-resolution data acquisition system along with very good trigger coincidence detection and on-line data reduction. In this paper the actual system specifications are given and a solution is discussed. The elected solution includes the development of four similar data acquisition modules, each with 16 channels based on 12-bit, 70 MSPS ADCs with LVDS outputs, dedicated memory, trigger logic, processing unit, and a USB 2.0 interface. The trigger and data processing logic of each module were placed inside a Xilinx-4 Virtex FGPA. The proposed solution allows a cheap and efficient system to be constructed in a PC-centric way.
- A large area TOF-tracker device based on multi-gap Resistive Plate ChambersPublication . Assis, P.; Bernardino, A.; Blanco, A.; Luz, R.; Mendes, L.; Michel, J.; Neiser, A.; Pereira, A.; Pimenta, M.; Shellard, R.; Traxler, M.; ClemĂȘncio, Filomena; Carolino, N.; Cunha, O.; Ferreira, M.; Fonte, P.; Lopes, L.; Loureiro, C.The TOF-tracker concept, the simultaneous measurement of accurate time and bi-dimensional space coordinates in a single gaseous detector, has been previously demonstrated. The detector yielded a time resolution of 77 ps Ï along with a bi-dimensional position resolution of 38 ÎŒm Ï over a full active area of 60 Ă 60 mm2. In here, we report about a large area, 1550 Ă 1250 mm2, TOF-tracker device, tested by tracking cosmic muons, yielding a position resolution down to 1.33 mm Ï, a simultaneous time resolution of 150 ps Ï and 92% detection efficiency, over the entire area of the detector. The sub-millimetre electronic resolution of the readout chain suggests that the position resolution here reported could be dominated by non-corrected systematic effects and therefore it could be yet significantly improved.