V. Bexiga

Performance Failure Prediction Using Built-In Delay Sensors in FPGAs

The objective of this paper is to propose a performance failure prediction methodology for FPGA-based designs, based on the use of a novel built-in programmable delay sensor. Digital Clock Managers (DCM) is used to fine tune the unsafe observation interval. The design procedure is described, including the constrained placement of some delay sensors. The proposed technique is particularly useful to monitor parametric Process, supply Voltage and Temperature (PVT) and aging-induced variations. It can be used during product lifetime, as a predictive delay fault detection technique, either to avoid unreliable operation, or to guarantee correct functionality with lower power consumption. The usefulness of the proposed technique is demonstrated with part of the data processor of a complex design for a medical imaging system used in PET-based mammography, configured in a Virtex-4 FPGA device (xc4vfx60-11ff1152).

An overview of the Clear-PEM breast imaging scanner

We present an overview of the Clear-PEM breast imaging scanner. Clear-PEM is a unique dual-head Positron Emission Mammography scanner using APD-based detector modules that are capable of measuring depth-of-interaction (DOI) with a resolution of 2 mm in 20 mm long LYSO:Ce crystals. Such capability leads to an image spatial resolution of 1.2 mm and a high efficiency, foreseeing the detection of 3 mm breast lesions in less than 7 minutes exams. The full system comprises 192 detector modules in a total of 6144 LYSO:Ce crystals and 384 32-pixel APD arrays readout by ASICs with 192 input channels that represents an unprecedented level of integration in PET systems. Throughout the project and besides the detector module, we had developed dedicated Frontend and Data Acquisition electronics, the mechanical design and construction of the detector heads and the robotic gantry, as well as all the software that include calibration (energy, time and DOI), normalization and image reconstruction algorithms. In this work we will discuss the developments and present the commissioning results of the detector before the beginning of the clinical trials program, scheduled for the end of the present year.

Characterization of the Clear-PEM breast imaging scanner performance

We present results on the characterization of the Clear-PEM breast imaging scanner. Clear-PEM is a dual-head Positron Emission Mammography scanner using APD-based detector modules that are capable of measuring depth-of-interaction (DOI) with a resolution of 2 mm in LYSO:Ce crystals. The full system comprises 192 detector modules in a total of 6144 LYSO:Ce crystals and 384 32-pixel APD arrays readout by ASICs with 192 input channels, which represents an unprecedented level of integration in APD-based PET systems. The system includes Frontend and Data Acquisition electronics and a robotic gantry for detector placement and rotation. The software implements calibration (energy, time and DOI), normalization and image reconstruction algorithms. In this work, the scanner main technical characteristics, calibration strategies and the spectrometric performance in a clinical environment are presented. Images obtained with point sources and extended uniform sources are also presented. The first commissioning results show 99.7% active channels. After calibration, the dispersion of the channels absolute gain is 15.3%, which demonstrate that despite the large number of channels the system is rather uniform. The mean energy resolution at 511 keV is 15.9% for all channels, and the mean DOI constant is 5.9%/mm, which is consistent with a 2 mm DOI resolution, or better. The coincidence time resolution at 511 keV, for a energy window between 400 and 600 keV, is 5.2 ns FWHM. The image resolution measured with point sources was found to be of the order of 1.3 mm FWHM. The DOI capability was found to have a strong impact on the image sharpness. Images of extended uniform 68Ge sources, corrected for sensitivity and for the artifacts due detector dead spaces, have good uniformity. First clinical breast images are presented.

Experimental validation and performance analysis of the clear-PEM data acquisition electronics

Obtaining images with high resolution and contrast from short exams is crucial for the viability of Positron Emission Mammography as an early breast cancer detection technique. The Clear-PEM detector is a Positron Emission Mammography scanner, developed by the Portuguese Consortium in the framework of the Crystal Clear Collaboration at CERN, based on high-granularity avalanche photodiodes readout with 12288 channels, coupled to pixilated 2x2x20 mm3 LYSO:Ce crystals in a double readout configuration. The scanner features a high bandwidth three-level acquisition system with negligible dead time in order to minimize exam time. The frontend is instrumented with low-noise amplifier/discriminator/multiplexer ASICs (L0 trigger) and free-running ADCs while the off-ddetector electronics, implemented in FPGAs, computes the trigger primitives from the pulse amplitude and timing. With this information the readout electronics selects interesting photoelectric events and groups multi-hit events due to in-Compton scatter into possible coincidences. After a first-level trigger (L1) is generated, filtered data is read out over a high speed data link into a second-level (L2) software trigger which reprocesses the selected events in temporal coincidence with more accurate energy and time extraction algorithms. The DOI coordinate and the re-validated energy and time allow to achieve an improved reconstruction of in-detector Compton scattering and rejection of random and scattered coincidences. On this paper, we report on the experimental validation, characterization and optimization of the L1 data acquisition electronics, readout link and L2 software trigger and present performance results. We discuss the validation of the associated operation software.

On restoring data coherence in a GALS system for medical imaging

Globally Asynchronous, Locally Synchronous (GALS) systems are widely used in medical applications. Typically, they exhibit high number of node-to-node communication channels that must transmit high data volume at high data rates and maintain data time coherence. The purpose of this paper is to present two structures for restoring data coherence in node-to-node communication, which may be lost due to different (unknown) delays introduced by the various communication channels. Both solutions allow differences among the channel delays larger than one clock cycle. Comparison of their most relevant characteristics is provided. Based on this comparison, one of the structures has been implemented to guarantee synchronism in a medical imaging system, namely in the Data Acquisition Electronics (DAE) of a PEM (Positron Emission Mammography) system. The DAE is a multi-board, multiple-FPGA platform (9 Xilin™ xc2v4000-4bf957 FPGA). The effectiveness of the solution has been validated in a hardware prototype. Test results are presented.

ITER prototype fast plant system controller based on ATCA platform

The ITER Fast Plant System Controllers (FPSC) are based on embedded technologies and will be devoted to both data acquisition tasks (sampling rates >1 kSPS) and control purposes in closed-control loops whose cycle times are below 1 ms. Fast Controllers will be dedicated industrial controllers with the ability to: i) supervise other fast and/or slow controllers; ii) interface to actuators and sensors and high performance networks. This contribution presents an FPSC prototype, specialized for data acquisition, based on the ATCA (Advanced Telecommunications Computing Architecture) standard. This prototyping activity contributes to the ITER Plant Control Design Handbook (PCDH) effort of standardization, specifically regarding fast controller characteristics. For the prototype, IPFN is developing a new family of ATCA modules targeting ITER requirements. The modules comprise an AMC carrier/data hub/timing hub compliant with the upcoming ATCA extensions for Physics and a multi-channel with galvanic isolation hot-swappable digitizer designed for serviceability. The design and test of a peer-to-peer communications layer for the implementation of a reflective memory over PCI Express and the design and test of an IEEE-1588 transport layer over a high performance serial link was also performed. In this work, a complete description of the solution is presented as well as the integration of the controller into the standard CODAC environment. The most relevant results of real tests will be addressed, focusing in the benefits and limitations of the applied technologies.

High-speed Data Acquisition Electronics for a PEM scanner

Positron Emission based mammography systems are expected to constitute a significant breakthrough in the early diagnosis of breast cancer. This may lead to a significant enlargement in the horizon of women life, since breast cancer is considered to be among the most deadly types. With this purpose, a consortium has been built to develop a mammography PET system in the framework of the Clear-PEM Collaboration. The Clear-PEM scanner is a unique Positron Emission Mammography (PEM) scanner using APD-based detectors. It is capable of measuring Depth-of-Interaction (DoI) with a resolution of 2 mm in LYSO:Ce crystals, enabling a spatial resolution of 1.2 mm. An important part of the PEM scanner is a high-speed DAE (Data Acquisition Electronics) system. DAE has been developed to process and acquire data coming from the 12,288 front-end (FE) photo-detector channels. In this paper, an overview of this scanner (system and board-level electronics, mechanical design, service and image reconstruction software) is presented, focusing on the specification and implementation of the DAE which is responsible for real-time retrieving, analyzing, filtering and formatting the data coming from the front-end. The objective is to identify relevant data and after conditioning, according to pre-defined protocols, send the data to an acquisition PC for image reconstruction. Communication between DAE and PC is carried out using the S-Link (proprietary of CERN) protocol. Experimental results of validation and test of the DAE system are presented.

Implementation of an ATCA/AXIe board for fast control and data acquisition systems of nuclear fusion devices

The implementation of an ATCA/AXIe board, developed for fast control and data acquisition systems of nuclear fusion devices, is presented. The implemented board was designed for systems requiring high levels of reliability and availability, such as those of long duration discharges or steady-state operation nuclear fusion experiments. Following ITER instrumentation guidelines for rear signals interfaces, the board comprises a passive rear transition module allowing analogue IO cabling connectivity and cable-less hop-swap maintenance of the front board. Onboard ADC modules have differential input, galvanic isolation and an ADC chopper circuit which assures offset compensation over time for integrators used on magnetic diagnostics. Classical clock and trigger synchronism as well as IEEE-1588/IRIG timing are supported. Full ATCA redundancy and management are also provided.