Objective: To explore readout architectures for the simultaneous high-resolution timing and bidimensional tracking of charged particles with Resistive Plate Chambers (TOF-tracker) and for the accurate detection of gamma rays for Positron Emission Tomography (PET).Materials and methods: Resistive plate chambers and their corresponding readout systems under evaluation were exposed to cosmic rays and β+ sources.Results: Over an active area of 625 cm2, we obtained a time resolution of 61 ps ơ and bidimensional position resolution below 150 μm ơ for the tracking and timing of charged particles from cosmic rays. The intrinsic precision for localising a small β+ source via the detection of its annihilation radiation was determined to be 0.49 mm FWHM.Conclusions: The proposed device exhibits excellent timing and position resolution for the tracking and timing of charged particles, with potential applications in nuclear and high-energy particle physics, as well as gamma imaging with applications in PET.

Muon tomography is one of several fields of applied physics that have witnessed the successful use of particle detection based on Resistive Plate Chambers (RPC). In this work, we report on an innovative project concerning transmission muography for geological characterization. For this purpose, a muon telescope built of four RPC planes was mounted on an adjustable structure and the telescope’s response to atmospheric muons was studied. Data acquisition campaigns took place at different locations for producing muographic images of the building of the Physics Department of the University of Coimbra, in Portugal. More recently, the detector was moved to an underground gallery of an old mine, where it is taking data that is being assessed in combination with the results from conventional geophysics techniques.

Robust methods to compute tissue displacements in optical coherence elastography (OCE) data are paramount, as they play a significant role in the accuracy of tissue elastic properties estimation. In this study, the accuracy of different phase estimators was evaluated on simulated OCE data, where the displacements can be accurately set, and on real data. Displacement (∆d) estimates were computed from (i) the original interferogram data (Δφori) and two phase-invariant mathematical manipulations of the interferogram: (ii) its first-order derivative (Δφd) and (iii) its integral (Δφint). We observed a dependence of the phase difference estimation accuracy on the initial depth location of the scatterer and the magnitude of the tissue displacement. However, by combining the three phase-difference estimates (Δdav), the error in phase difference estimation could be minimized. By using Δdav, the median root-mean-square error associated with displacement prediction in simulated OCE data was reduced by 85% and 70% in data with and without noise, respectively, in relation to the traditional estimate. Furthermore, a modest improvement in the minimum detectable displacement in real OCE data was also observed, particularly in data with low signal-to-noise ratios. The feasibility of using Δdav to estimate agarose phantoms' Young's modulus is illustrated.

We present the initial stages of development of a Finite Element Method-based time-dependent elastic numerical model which seeks to support the employment of our Optical Coherence Elastography system for assessing murine retinal elasticity. The current model is able to reconstruct displacement maps in both homogeneous and heterogeneous domains with errors up to a few hundredths relatively to a known exact displacement map, within 1 millisecond. The results demonstrate the robustness of the numerical algorithm under different elastic domains, and model parametrization with real Optical Coherence Elastography data is already in progress.

In this paper we address the numerical solution of the inverse elastography problem, from the knowledge of the excitation field on the boundary and the displacement field in a grid of points within the domain. We suggest using a representation of the solution by the method of fundamental solutions and using a Newton-type method to iteratively approximate the Lain coefficients of the medium from elastography displacement measurements. We consider a toy model to illustrate the performance of the method.

We present an Optical Coherence Elastography (OCE) system, based on a swept-source Optical Coherence Tomography (OCT) setup, and evaluate its performance in terms of phase stability and minimum detectable displacement. The ability to record sub-pixel movements in samples under dynamic conditions was also assessed. The OCE system has a time stability of 396.9 +/- 46.7 ps. The phase stability, given by the standard deviation of the measured phase difference, was 72.44 mrad, which corresponds to a minimum detectable displacement of 6.11 nm. Tests showed that the OCE system can detect and measure sub-pixel movements in samples under dynamic mechanical excitation.

The Carpet-3 experiment for investigation of gamma-radiation with energy above 100 TeV is currently being prepared at the Baksan Neutrino Observatory of the Institute for Nuclear Research, RussianAcademy of Sciences. At present the plastic scintillation counters with a total continuous area of 410 m2 are installed in the muon detector (MD) underground tunnel, and they are totally equipped with electronics. The counters’ gains and thresholds have been adjusted. Fifteen modules of shower detectors are placed on the surface of the MD absorber. Ten of them contain 9 standard plastic counters with an area of 1 m2 each. Also 24 modules without counters are arranged on the territory of the array. These modules will accomplish a surface part of the Carpet-3 array. The preliminary estimates show that the new array will have the best sensitivity to the flux of primary gamma rays with energy

Introduction: Ebstein's anomaly is traditionally described as an isolated anomaly of the right valvular apparatus.In the last decade, associations with left side anomalies have been described, specifically ventricular non-compaction.More recently, the link between this association and the presence of mutations contractile apparatus proteins has been described.Case description: A 34-year-old woman with Ebstein's anomaly diagnosed since childhood had regular follow-up until 2010.The last TTE (2009) describes apical insertion (þ/-25mm;15.4mm/m2 of the crux plane) of the septal leaflet of the tricuspid valve, compatible with Ebstein's anomaly, and minimal tricuspid regurgitation and norma biventricular function.She returned in August 2014 with complains of de novo palpitations.The ECG showed Sinus Rhythm with incomplete RBBB and 24h HOLTER was unremarkable.At this time the TTE showed, in addition to Ebstein's anomaly, a dilated left ventricle with echocardiographic criteria of non-compaction and moderate systolic dysfunction and standard HF therapy was initiated.In October 2014 she reported a pregnancy (unplanned) and ACE inhibitor was suspended.Pregnancy was complicated by pre-eclampsia requiring induction of normal delivery at 39 weeks.In the immediate postpartum, she developed Supra-Ventricular Taquicardia at 190bpm with reversion to sinus after iv labetalol and a few hours later she developed acute pulmonary oedema with severly compromissed LVEF.She responded to vasodilator and diuretic therapy and was discharged from ICU in day 5. Cardiac MRI showed a dilated LV (LVDV 199ml; 122ml/m2) with apical hypertrabeculation with criteria for non-compaction.The LVEF was severely compromised with a LVEF of 30% without edema or late enhancement.and a normal RV global size and function.She was at home at 15th day postpartum on NYHA II-III under standard HF therapy and anticoagulation.After 6 months therapy she was in NYHA II, although and with no improvement of LVEF, so a decision to implant an ICD was made.She maintained palpitations and although HOLTER was normal, episodes of tachycardia (SVT vs VT) were detected in ICD interrogation and she is currnelty being evaluated for and invasive EPS with intent of ablation.At 3 months, her male child was diagnosed with DCM with moderate to severe LVEF compromise and hypertrabeculation and LV lateral wall and apex.The fetal echocardiogram had been normal.Prognostic modifying therapy was initiated, with improvement of LVEF (48% at 14 months).The genetic study of the child identified heterozygosity in a variant of the MYH7 gene (recently related to the association between Ebstein's anomaly þ non-compacted myocardium), later also confirmed in the mother.Conclusions This case describes the importance to look for left size lesions in Ebstein patients, some of the can only become apparent in the adult life.The association with LVNC has particular importance, because of the dismal prognosis and autosomal dominant inheritance.

Optical Coherence Tomography (OCT) is a high-resolution, non-invasive and contactless imaging technique based on optical interferometry. After the Time Domain (TD) and the Spatially Encoded Frequency Domain (SEFD), the Swept-Source (SS) OCT, also known as Time Encoded Frequency Domain (TEFD) OCT, is the latest technology available. It is based on a fast wavelength-sweeping of a narrow laser line over the bandwidth of the source. SWEEP TRIGGER and K-CLOCK signals are provided by the laser source and establish the time base for the overall system. Data acquisition and the two-dimensional scanning of the object of interest must be accurately synchronized after those signals. The proposed solution for the overall scanning/acquisition/sweeping synchronism is an integrated and dedicated FPGA-based control system that is being developed and will generate the automatic, programmable and flexible operation that will replace the present, manually adjustable, system. This way, complete reproducibility of experimental conditions will be obtained, along with the possibility of optimizing the galvanometer /mirrors control. This system is being built around a Xilinx XC6SLX45 FPGA and will be integrated in the already developed control software of the OCT system.

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, 1550×1250 mm2, 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.

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 high-sensitivity 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 virtually 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.

The evaluation of corneal nerve morphology by optical methods may form the basis of a simple, non-invasive technique for early diagnosis and accurate assessment of peripheral diabetic neuropathy. Currently, corneal nerves can be imaged in vivo using corneal confocal microscopy, an expensive technique that is only available at large medical units. Our goal is to develop an optical technique for peripheral neuropathy assessment, through corneal nerves imaging, based on simple, easy to operate and widespread instrumentation. This technique will be built upon automatic algorithms for corneal nerves segmentation and morphometric analysis and an optical confocal module for recording corneal nerves images using a standard slit-lamp, the most commonly used instrument in ophthalmic practice to observe the anterior eye. Here we present the current status and results of this ongoing project.

Purpose We intend to develop an efficient method to assess in-vivo the corneal respiratory function in order to diagnose corneal cells dysfunction prior to its pathologic expression. Methods Metabolic alterations can be assessed by measuring the amount of the metabolic co-factors flavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide (NADH). FAD has advantages over NADH, like being present only in the mitochondria. Furthermore, using fluorescence lifetime imaging microscopy (FLIM) we are able to discriminate between its free or protein-bound states. We resorted to a PicoQuant MicroTime 100 (PicoQuant GmbH, Berlin, Germany) coupled to an Olympus BX51 Microscope (Olympus Corporation, Tokyo, Japan). This setup uses a pulsed blue diode laser with a trigger frequency of 40 MHz with an excitation filter of 440±10 nm. Intensity decay curves were processed with SymPhoTime v5.3 Software (PicoQuant GmbH). The instrument response function was acquired to improve data analysis precision. Results We successfully acquired ex-vivo autofluorescence images of male Wistar rat and Bovine corneas. A bi-exponential decay was observed in both cases with a fast decay around 1 ns and a longer one around 4 ns, which correspond to protein-bound and free FAD, respectively. These results are in accordance with other studies, although there is some controversy regarding FAD lifetimes. Conclusion We showed that it is possible, with our apparatus, to acquire metabolic images of the cornea using FAD autofluorescence. We intend to modify the instrument optical setup in order to acquire reflectance and fluorescence lifetime images simultaneously for corneal layer identification.

We intend to develop an efficient method of measuring respiratory function of the cornea. With this purpose, we resorted to fluorescence lifetime imaging microscopy (FLIM) to monitor the metabolic co-factor flavin adenine dinucleotide (FAD). FAD and nicotinamide adenine dinucleotide (NADH) are co-factors of the electron transport chain. Therefore alterations in amount of these molecules reflect alterations in the metabolism. For assessing the potential of FLIM for metabolic imaging of the cornea, we performed a series of experiments using a time-correlated single photon counting (TCSPC) fluorescence lifetime microscope (Picoquant to MicroTime 100 coupled to an Olympus BX51 Microscope). In this technique, the acquired signal is the convolution between the instrument response function (IRF) and the fluorescence signal from the sample. IRF was acquired using an Erythrosin B solution. In this work we show that it is possible to acquire fluorescence lifetime images of rat and bovine corneas using FAD autofluorescence.

A complex task for positron emission tomography (PET) cameras is the design of an appropriate coincidence-detection 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 specification 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 algorithm implemented inside a Xilinx Virtex-5 field-programmable gate array for a small-animal RPC-PET camera being built.

The time resolution for gamma photon pairs of a detector based on resistive plate chamber technology is close to 300 ps FWHM. This allows a tight time window for coincidence detection, reducing the number of random coincidences observed and the overall noise of the acquired image. We implemented, inside a Xilinx Virtex-5 field programmable gate array, a fully programmable coincidence-trigger system with sub-nanosecond resolution and low latency for a small animal RPC-PET camera being built. An automatic procedure to construct a histogram of coincidences was implemented that helps characterizing the camera and allows compensating for different delays in the time channels. The time window for coincidences can then be placed at the optimal position helping to reject coincidences from undesired sources.

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 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.

A general data acquisition architecture, allowing a clean conceptual separation of the fundamental blocks in a data acquisition setup, is presented. The approach taken surfaced from a study of several modern architectures and from experience acquired while developing an object-oriented programming solution for a previously developed high-speed architecture. This process of software development leaded naturally to a concept where a net separation between data transfer, and control and trigger signals, suggested a similar general decomposition of the data acquisition hardware, in such a way that the same fundamental hardware blocks can be used in several different configurations.In this paper we report on the strategy and results obtained while developing in VHDL such an important and fundamental unit of the data acquisition chain as the data acquisition saving block. The solution proposed for the data saving block, tested using field programmable gate arrays, implements pre- and post-trigger functionality, supports continuous data streams up to hundreds of MHz, has a large memory pool (hundreds of megabytes), and has an interface capable of providing, upon request, a block of data from a specified address without interfering with the data saving process.