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The static random access memory (SRAM) of an ultralow power system-on-chip (SoC) was tested for single-event upsets (SEUs) using alpha particles and neutron beam sources. The measurements are compared to those of an SRAM-based field-programmable gate array (FPGA), built on a similar technology node. The results reveal opposite trends in the two devices regarding the upsets of the logic states, as well as differences in the dependence of SEU cross section (CS) on the operation voltage. The sensitivity of the SoC SRAM to multiple bit upsets with the different radiation sources is analyzed as well. The results demonstrate that the unique SoC design, which enables complete near/subthreshold operation, does not compromise the SoC bit upset tolerance compared to devices of similar technology node which operate at higher voltages.

The use of the Average Functional Group Approximation for self-shielding corrections at inelastic neutron spectrometers is discussed. By taking triptindane as a case study, we use the above-mentioned approximation to simulate a synthetic dynamic structure factor as measured on an indirect-geometry spectrometer, as well as the related total scattering cross section as a function of incident neutron energy and sample temperature, and the transmission spectra depending on the sample thickness. These quantities, obtained in a consistent way from the Average Functional Group Approximation, are used to calculate the energy-dependent self-shielding correction affecting the sample under investigation. The impact on the intensities of low-energy vibrational modes is discussed, showing that at typical experimental conditions the sample-dependent attenuation factor is about 15% higher compared to the correction at higher energies.

We provide a worked example on how to obtain the total neutron scattering cross section of organic polymers at thermal neutron energies by means of the Average Functional Group Approximation. Within this framework, a polymer is rationalised as composed of hydrogen atoms belonging to specific functional groups,therefore taking into account the material-specific incoherent inelastic scattering contributions to the thermal cross section. Such simplified model allows the calculation of thermal neutron cross sections for a broad variety of materials of interest in neutron applications, e.g., sample containers and shielding components. We discuss in detail the case of ABS, often available as a 3D-printing material, whereby three polymers (acrylonitrile, butadiene, and styrene) can be combined in several mass percentages depending on the final application. Results are obtained using the NCrystal module already featuring the Average Functional Group Approximation.

We present an experimental investigation of methylammonium lead tribromide single crystals in the orthorhombic, tetragonal, and cubic phases based on inelastic and deep inelastic neutron scattering experiments. We show how the average hydrogen nuclear kinetic energy, mainly affected by zero-point vibrational energies, shows differences larger compared to the changes simply related to temperature effects when moving from one phase to another. In particular, the Gaussian contribution to the average nuclear kinetic energy is larger in the tetragonal phase compared to the cubic and orthorhombic ones. Moreover, we find that the vibrational densities of states of MAPbBr3 single crystals in the orthorhombic phase are compatible with previously reported results on powder samples, and that the only vibrational modes that show slightly different frequencies compared to MAPbI3 are those in the energy range between 100 and 300 cm−1, related to librational/rotational modes. As these shifts are of about 10 cm−1 and do not affect any higher-energy vibrational mode, we conclude that the zero-point energies and average nuclear kinetic energies in the two-hybrid organic/inorganic perovskites are expected to be approximately the same within a harmonic framework.

The present study is focused on the development and characterization of innovative cementitious-based composite sensors. In particular, multifunctional cement mortar composites with enhanced functional, piezo-resistive, properties are designed with Multiwall Carbon Nanotube-MWCNTs and reduced Graphene Oxide-rGO dispersed in a natural-rubber latex aqueous dispersion, by exploiting both the concept of confining of the conductive filler in the polymeric phase. The manufactured cement-based composites were characterized by means of Inelastic Neutron Scattering to assess the hydration reactions and the interactions of natural rubber with the hydrated cement phases and by Electron Scanning Microscopy and X-Ray diffraction to evaluate the morphological and mineralogical structure, respectively. Piezo-resistive properties to assess electro-mechanical behavior in strain condition are also measured. The results show that the presence of natural-rubber latex permits to obtain a three-dimensional rGO/MWCNTs segregate structure which catalyzes the formation of hydrated phases of the cement and increases the piezo-resistive sensitivity of mortar composites, representing a reliable approach in developing innovative mortar-based piezoresistive strain sensors.

Extra virgin olive oil (EVOO) is defined as a functional food as it contains numerous phenolic components with well-recognized health-beneficial properties, such as high antioxidant and anti-inflammatory capacity. These characteristics depend on their structural/conformational behavior, which is largely determined by intra- and intermolecular H-bond interactions. While the vibrational dynamics of isolated compounds have been studied in a number of recent investigations, their signal in a real-life sample of EVOO is overwhelmed by the major constituent acids. Here, we provide a full characterization of the vibrational spectroscopic signal from commercially available EVOO samples using Inelastic Neutron Scattering (INS) and Raman spectroscopies. The spectra are dominated by CH2 vibrations, especially at about 750 cm−1 and 1300 cm−1. By comparison with the spectra from hydroxytyrosol and other minor phenolic compounds, we show that the best regions in which to look for the structure–activity information related to the minor polar compounds is at 675 and 1200 cm−1 for hydroxytyrosol, and around 450 cm−1 for all minor polar compounds used as reference, especially if a selectively deuterated sample is available. The regional origin of the EVOO samples investigated appears to be related to the different amount of phenolic esters versus acids as reflected by the relative intensities of the peaks at 1655 and 1747 cm−1.

Extra virgin olive oil (EVOO) is one of the most important ingredients as well as the main source of lipids in the Mediterranean diet. It is known to contain biologically relevant phenolic componen...

Muon tomography is a very promising imaging technique for the control of cargo containers. It takes advantage of cosmic muons and their interaction mechanisms to reconstruct images of the volume traversed by these particles. In the present work, the imaging performance of a novel muon tomography scanner based on resistive plate chambers detectors is investigated. By means of several Monte Carlo simulations, some imaging parameters are evaluated. The results in terms of spatial resolution, field-of-view and volume and material recognition make the presented scanner and its geometry suitable for muon tomography.

This paper presents a Python-based algorithm, named INSCorNorm, to correct the inelastic neutron scattering (INS) spectra for both sample and container self-shielding and to normalize the experimental spectral intensity to an absolute physical scale (barn/energy unit) facilitating the comparison with computer simulations and interpretation. The algorithm is benchmarked against INS measurements of ZrH

This paper presents a Python-based algorithm, named INSCorNorm, to correct the inelastic neutron scattering (INS) spectra for both sample and container self-shielding and to normalize the experimental spectral intensity to an absolute physical scale (barn/energy unit) facilitating the comparison with computer simulations and interpretation. The algorithm is benchmarked against INS measurements of ZrH2 performed on the TOSCA spectrometer at the ISIS Facility. We also apply the algorithm to the INS spectra from l-lysine, a system of broad interest in biology and medicine, and we discuss how corrected INS data provide an experimental benchmark for theoretical calculations of nuclear anisotropic displacement parameters in molecular systems. The total neutron sample cross section to use for the self-shielding corrections is discussed, as well as the best approach to derive experimentally the cross section at the VESUVIO spectrometer, together with the experimental value of the hydrogen nuclear mean kinetic energy, ⟨Ek⟩. The algorithm is made available to the neutron user community within the MANTID software.

Every year, 700 million twenty-foot (container) equivalent units pass through the container terminals of the harbours all over the world. Only a small percentage (34%) are scanned to inspect the presence of radioactive materials. The need for controls is hampered essentially by three factors: the amount of both time and personnel necessary to control each container and the use of scanning methods based on systems potentially harmful for the personnel itself. Muon tomography can become a strategy for fast and reliable inspection of containers without using ionizing radiation. This technology takes advantage of multiple Coulomb scattering of the muons (particle produced by cosmic rays) through media to understand the composition and the geometry of the scanned volume. The TECNOMUSE project has the purpose to realize a muon tomography scanner based on a novel geometry and, for the first time, using Resistive Plate Chambers detectors. In this work, the preliminary results from the TECNOMUSE scanner are evaluated via Monte Carlo simulations. Many different simulations have been made with the aim to assess the detection capabilities of the device, its spatial resolution and the time required to reconstruct and distinguish different materials.

In this work, an experimental comparison of the capabilities of a scintillation detector based on a NaI:Tl and a LaBr 3 :Ce monolithic crystals is presented. The main advantage of LaBr 3 :Ce respect to NaI:Tl is its very high light yield (i.e. 63photons/keV versus 38photons/keV), allowing a considerable improvement of the statistical factor affecting light collection and, consequently, Spatial Resolution (SR) and Energy Resolution (ER). Nevertheless, the following results show that the improvement of the SR with the LaBr 3 :Ce is smaller than expected. As analyzed, it could be due to the LaBr 3 :Ce refractive index higher than the NaI:Tl one, that leads to a loss of scintillation light. In fact, the measurements produce similar imaging results (SR at crystal center is about 1.1mm for both crystals), while the ER is slightly better for the LaBr 3 :Ce, as expected (7.6% and 8.8% for LaBr 3 :Ce and NaI:Tl, respectively). This work encourages a further and more specific analysis about how the refractive index affects the amount and the shape of crystal light distribution.

[EN] We present the first results of the MINDVIEW project. An innovative imaging system for the human brain examination, allowing simultaneous acquisition of PET/MRI images, has been designed and constructed. It consists of a high sensitivity and high resolution PET scanner integrated in a novel, head-dedicated, radio frequency coil for a 3T MRI scanner. Preliminary measurements from the PET scanner show sensitivity 3 times higher than state-of-the-art PET systems that will allow safe repeated studies on the same patient. The achieved spatial resolution, close to 1 mm, will enable differentiation of relevant brain structures for schizophrenia. A cost-effective and simple method of radiopharmaceutical production from C-11-carbon monoxide and a mini-clean room has been demonstrated. It has been shown that C-11-raclopride has higher binding potential in a new VAAT null mutant mouse model of schizophrenia compared to wild type control animals. A significant reduction in TSPO binding has been found in gray matter in a small sample of drug-naive, first episode psychosis patients, suggesting a reduced number or an altered function of immune cells in brain at early stage schizophrenia. (c) 2018 Elsevier Masson SAS. All rights reserved., This project is funded by EU grant FP7-HEALTH-F2-2013-603002.

The present and future developments of time-resolved prompt-gamma activation analysis (T-PGAA) at pulsed neutron sources is discussed in the framework of the successful history of neutron-activation techniques. A brief description of the state of the art and the most important user facilities using standard prompt-gamma activation analysis (PGAA) is provided. Then, we discuss the challenges and the opportunities for T-PGAA at pulsed neutron sources, and the potential impact for applications to cultural heritage, radiation protection, and security. We notice some inversions of trend needed for the further development of T-PGAA with epithermal and fast neutrons, such as the possibility to use fast and high-efficiency γ-ray scintillators with lower energy resolution (compared to usual high-purity germanium detectors) when the signal from neutron capture resonance is selected. We also suggest how detection systems often used in other fields, such as medical physics, can be of interest and inspiration also in the case of neutron-based investigations. Finally, we present new data of T-PGAA measurements on VESUVIO using neutron energies up to the keV using the scintillators available on the instrument, for samples of gold (of interest in cultural heritage), cadmium (for environmental safety), and tantalum (a material used in biomedical implants).

Achieved spatial resolution of the PET systems is often limited by the parallax error due to the lack of information about the Depth of Interaction (DoI) inside the crystal of the incoming 511 keV annihilation photons. The smaller the diameter of the PET ring and the thicker the scintillator are, the more this error affects imaging performance. In this work, a DoI calculator suitable for monolithic scintillation crystals and based on the shape of the scintillation light distribution at the photodetector surface has been proposed. To test the estimator performance, a test PET module with a $50 \times 50 \times 20\; \hbox{mm}$ monolithic LYSO crystal coupled to a $12 \times 12$ SiPM array has been employed. In addition, for calibration and validation of the method, Geant4 simulations have been also used. The key result of the application of the proposed DoI estimator is obtaining a continuous DoI estimation with an average DoI resolution of about 5 mm in the 20 mm-thick crystal. Benefiting from the DoI estimation capabilities of the method, it has been also possible to achieve additional important goals, first of all reducing the parallax error. First, because the scintillation light collection varies as a function of the 3D position of the interaction of the annihilation photon inside the crystal, a method to correct this response variation via a proper 3D look-up-table is proposed. This has led to an improvement of about 35% in energy resolution. Moreover, a DoI-dependent position algorithm has been proposed, allowing an improvement of both planar (X-Y) position linearity and planar spatial resolution. This algorithm is specifically developed for the rows/columns multi-channel readout logic, that reduces the number of independent channels from ${\rm N} \times {\rm N}$ to ${\rm N} + {\rm N}$ , where N is the number of SiPM photodetection elements (12 in our case) in each row and column. This development was performed in the framework of the MindView PET/MRI brain imaging project.

We present experimental results and FLUKA Monte-Carlo simulations reproducing the counting efficiency and the energy resolution of the cerium-activated yttrium-aluminium-perovskite photon detectors installed on the VESUVIO neutron spectrometer at the ISIS Pulsed Neutron and Muon Source. In particular, we investigate the performance of these detectors in the energy range between 100 keV and 300 keV. In this range, the γ -emission of the 197Au resonant analyser foils, installed on VESUVIO to select the energy of scattered neutrons, is predominant. Such photons are currently discarded by the low-level discrimination threshold of the acquisition electronics set to 600 keV. Here, we model the detector crystals for a series of thickness values, and we discuss how 2-cm-thick crystals would significantly reduce the acquisition times with respect to the 6-mm-thick crystals employed at present. Additionally, we show how the signal-to-background ratio can be substantially enhanced by shielding the scintillators with 0.5-mm-thick Pb foils. We finally discuss the improved detection performance on a model sample of interest for Cultural-Heritage applications.

We propose the characterization of a first array of 10×10 Lutetium Yttrium Orthoaluminate Perovskite (LuYAP:Ce) crystals, 2 mm×2 mm×10 mm pixel size, with an innovative assembling designed to enhance light output, uniformity and detection efficiency. The innovation consists of the use of 0.015 mm thick dielectric coating as inter-pixel light-insulators, manufactured by Crytur (Czech Republic) intended to improve crystal insulation and then light collection. Respect to the traditional treatment with 0.2 mm of white epoxy, a thinner pixel gap enhances packing fraction up to 98% with a consequent improvement of detection efficiency. Spectroscopic characterization of the array was performed by a Hamamatsu R6231 photomultiplier tube. A pixel-by-pixel scanning with a collimated 99mTc radioisotope (140 keV photon energy) highlighted a deviation in pulse height close to 3.5% respect to the overall mean value. Meanwhile, in term of energy resolution a difference between the response of single pixel and the array of about 10% was measured. Results were also supported and validated by Monte Carlo simulations performed with GEANT4. Although the dielectric coating pixel insulator cannot overcome the inherent limitations of LuYAP crystal due to its self-absorption of light (still present), this study demonstrated that the new coating treatment allows better light collection (nearly close to the expected one) with in addition a very good uniformity between different pixels. These results confirm the high potentiality of this coating for any other crystal array suited for imaging application and new expectations for the use of LuYAP for PET systems. © 2015 Elsevier B.V.

Magnetic Resonance (MR) guided Focused Ultrasound Surgery (MRgFUS) technology, combined with High Intensity Focused Ultrasound (HIFU) beams, has opened to new therapeutic protocols for various pathological conditions. The success of this therapy relies on the accuracy of the guidance for therapy provided by thermal mapping of sonication, which is obtained with MR imaging. In addition, in recent years, multimodality Positron Emission Tomography and Magnetic Resonance Imaging (PET/MRI) imaging has been developed. This technique is able to provide simultaneous functional and soft tissue morphological imaging and, for this reason, it is particularly engaging for brain imaging. The key concept behind this work is to assess the feasibility of a brain-dedicated PET- and MRI-guided FUS device providing real-time evaluation of the outcome of the HIFU therapy. At first, a method to improve imaging capabilities of small-ring PET scanners will be presented. It will be showed that thanks to this method it is possible to obtain high tomographic spatial resolution with an affordable, brain-dedicated, PET scanner based on monolithic scintillation crystals and able to work as an insert in a MRI system. Moreover, simulations of an anthropomorphic phantom will be made in order to evaluate the effect of different HIFU protocols and, in addition, to investigate the capability of thermal maps provided by MRI for assessing the effect of the HIFU treatment. Finally, from the comparison of the spatial resolutions provided by each imaging technique (PET, MRI and thermal MRI) and the HIFU therapy, it will be possible to assess the feasibility of the proposed multimodality device. The system suggested in this work should be composed of a MRI scanner with a PET insert and a customized MRI-compatible focused ultrasound applicator. It could be very useful for the diagnosis and therapy of brain tumors thanks to the possibility of a real-time evaluation of the effect of the HIFU treatment. The protocol for the therapy could be executed in three main steps: the diagnosis of the pathological condition by means of fused anatomical imaging from MRI and functional imaging from PET (with different radiotracers) that allow to identify the region where apply the therapy, the ablation of the tumor by means of HIFU beams and the simultaneous evaluation of the thermal response of the tissues by means MRI thermal maps and, finally, the assessment of the outcome of the therapy by means, again, of PET/MRI hybrid imaging. The results suggest that PET-and MRI-guided focused ultrasound surgery (PET/MRgFUS) could be an innovative, feasible and engaging technique for tumor ablation in the brain.

A series of small size 22Na point sources have been simulated using GATE, following the NEMA protocol, and applied to the geometry of a brain dedicated PET so-called MindView. The simulated scanner geometry is currently composed by one ring of 20 detector blocks with a distance of about 330 mm between opposite detectors. Each detector module includes a monolithic LYSO crystal of 50 × 50 × 20 mm3 and a custom 12 × 12 SiPM array (TSV-type, SensL). The system defines an axial and trans-axial fields of view (FoV) of about 46 mm and 240 mm, respectively. The scintillation light inside the monolithic block was simulated in GEANT4 and is sampled following the readout scheme providing information on each SiPM array row and column (12 + 12). Out of this, three different approaches for the determination of the impact coordinates within the monolithic crystals have been considered. A first approach makes use of the center of gravity (CoG) calculation for the planar XY coordinates but the photon impact depth of interaction (DoI) is not considered. The other methods obtain the XY coordinates using the Raise to Power algorithm (RTP) before CoG calculation, with both discrete (second method) and continuous (third one) DoI information. The data is introduced on the STIR platform for reconstruction using a filtered back projection 3D re-projected algorithm (FBP3DRP). Spatial resolutions ranging in the intervals [2 mm, 3.4 mm], [2.3 mm, 3.3mm] and [2.2 mm, 2.3 mm] have been obtained for the radial, tangential and axial directions, respectively. The points sources were positioned at a radial offset of 100 mm radially out of the center.

Purpose Proton therapy is a radiotherapy technique particularly engaging since it allows for a well-defined penetration and dose delivery. The estimation of the beam penetration is essentially based on the preliminary treatment planning. Real-time and in vivo estimation of the range of the proton beam will be very useful [1] : in this context, imaging from gamma-prompt plays a key role for therapy assessment [2] . Methods In this work we propose a novel geometry for gamma-prompt (see Figure). The setup is based on two detectors placed, along a rail, perpendicularly to the proton beam. Each detector is composed by a knife-edge collimator and a small Field-of-View (50 × 50 mm2) Gamma-camera based on a LYSO crystal and a position-sensitive photodetector. This detection geometry has been studied through Monte Carlo simulations developed with GATE and GEANT4. Results Many tests have been made in order to obtain the optimal detection configuration. With the best one, the following results have been achieved: proper counting-rate (about 50 kHz) and spatial resolution (about 4 mm). Conclusions The proposed geometry allows a good trade-off between counting rate and achievable spatial resolution in the region of interest undergoing to proton therapy. Further experimental measurements of clinical protocols are planned.

Purpose Spatial resolution (SR) and counting efficiency (CE) are two pivotal parameters for Nuclear Medicine devices based on scintillation crystals. These parameters are in conflict with one another: the smaller the thickness of the scintillation crystal, the better (the worse) the resolution (the efficiency). In this work, a phoswich approach is reported, allowing devices to provide information optimized for both parameters. Methods In [1] , [2] a parameter to solve the Depth-of-Interaction (DoI) in scintillation detectors has been presented. As proved in [3] , it allows to distinguish the layer of a two-layers phoswich in which gamma-photons interact with the detector, too. The experimental response of a 50 × 50 mm2, 20 mm-thick, LYSO detector has been compared with a simulated detector of the same area based on two 10 mm-thick layers, coupled through optical grease (see Figure). Results The 20 mm-thick experimental detector exhibits a SR ranging from 2.85 (upper 10 mm) to 2.51 (lower 10 mm). With the proposed phoswich approach, the resolution improves up to 2.32 mm for the upper layer (again, 10 mm-thick) and 1.50 mm for the lower layer. With this approach, one can basically choose between the configuration showed in Table. Anyway, the phoswich approach improves the overall SR. Conclusions The proposed method, applied to phoswich detectors, allows to arbitrarily improve either CE or SR. The first is enhanced by selecting events from both layers, whereas the latter improves by selecting events from the lower layer.

Magnetic resonance imaging is effective for non-invasive detection of myocardial diseases by extracellular volume fraction (ECV) estimation. A new methodology for T1 and ECV mapping is tested in this work, comparing results with other well-consolidated methods. The associated level of uncertainty for data was also estimated, to assess the reliability of the technique. A phantom with known T1 values was used for reference, and 60 subjects (40 controls, 20 diseased patients) were examined, using the modified look-locker inversion-recovery (MOLLI) method. Obtained T1 data were studied in terms of accuracy (difference with reference T1), paired comparisons with other methods, and Gamma-tool analysis with tolerances criteria of 4.21 mm for distance-to-agreement, and between 2%-5% for T1 difference. Accuracy and precision of the T1 mapping was analysed by phantom measurements, and the uncertainty of the ECV was estimated by T1 error propagation. Differences (in paired comparisons) of T1 datasets were not significant neither for statistical tests, nor for Bland-Altman analysis. T1 accuracy was between -12% and -1% across methods, slightly better for the tested method (mean accuracy in the T1 range of interest better than 2%). The Gamma analysis confirm slightly better results for the tested method than other methodologies. The new method improves the computational efficiency by a factor of 25 (at least), revealing to be also more suitable for Big Data-related applications.

A whole-body PET device is sometimes not suitable for brain studies because the achieved image resolution is typically not sufficient to investigate small size structures. Thus, a dedicated brain PET insert system with high performance would overcome such limitations. Moreover, these functional studies lack of anatomical information. It is shown elsewhere the convenience of simultaneously acquisition of PET and MR data. In this work we show the final design and first pilot evaluation tests of a novel brain PET insert. Each detector block is based on a monolithic scintillation crystal, an array of SiPMs and a readout allowing characterizing the scintillation light distribution in the X and Y detector axes. The scintillators have a parallelepiped geometry with dimensions of 50×50×20 mm3. Their lateral walls are black painted and with the entrance face coupled to a retroreflector optical layer. We have determined an average (XYZ) detector spatial resolution through the FWHM of 1.2 mm (whole scintillator volume). The DOI resolution was measured with lateral incidence experiments and found to be about 3.5 mm, also on average for all photons depth of interactions and crystal positions. Thanks to the retroreflector, the energy resolution improves when compared to a case with all surfaces black painted, resulting on an average value of 13%. The tomographic reconstruction of the data was evaluated using different algorithms, including analytical (FBP STIR-3D), iterative (MLEM and List Mode OS) and a novel method that provides images by directly tracing the measured LORs. The minimum pixel/voxel sizes that were tried are 0.8/0.4 mm, 1.0/0.5 mm and 0.16/0.16 mm, respectively. All methods made it possible to show the PET system capabilities to resolve 1.6 mm rods in a Derenzo-like phantom filled with 150 uCi and scanned for 20 minutes. Pilot tests of the PET insert inside a clinical 3T MR showed a good system performance for most of the sequences typically used for brain imaging.

In recent years, a new generation of compact gamma cameras, based on monolithic scintillation crystals, has become increasingly widespread. The main advantages of small FoV gamma cameras with respect to the standard ones are high portability, low cost and low weight, allowing several clinical applications, from scintimammography to intraoperative tumor localization. In gamma cameras based on continuous scintillation crystals, intrinsic Spatial Resolution (SR) is mainly affected by two factors: scintillation light collection efficiency and overall crystal thickness. The first affects the counting statistics, the latter impacts on the light distribution width. To fully investigate the potentiality of these devices we took advantage of Monte Carlo simulations as a valuable tool to physically characterize the imaging systems and to establish a priori reference values. GEANT4 toolkit allows to completely describe the phenomenon of light emission and propagation through the media, providing control to all second-order factors existing in real systems. Results show clearly that SR is dependent on the number of photoelectrons produced and on the light spread. Furthermore, the role of refractive index has been unambiguously identified as an important factor affecting light collection and consequently SR.

The MindView European Project pursues the development of a high efficiency and high resolution brain dedicated PET detector, simultaneously working with a Magnetic Resonance Imaging (MRI) system. Since the PET scanner is based on a small diameter ring and on thick monolithic scintillation crystals to assess high efficiency, the parallax error related to off-center positron annihilation is a critical issue. The Depth of Interaction (DoI) discrimination can reduce the blurring due to this phenomenon. In this work, we propose a novel DoI estimator, based on the ratio of the integral of scintillation light distribution to its maximum (named N/I). In a preliminary way, by means of Monte Carlo simulation, we have validated the correlation between this parameter and the DoI. Furthermore, we have experimentally tested the capability of such DoI estimator on a monolithic 20 mm-thick LYSO crystal optically coupled to a 12x12 silicon photomultipliers (SiPMs) array. Thanks to the proposed method, it is possible to select interaction events coming from different depths of the crystal. The DoI discrimination capability has been confirmed by using a collimated slanted pencil-beam: the proposed estimator allows to produce different images coming from events belonging to different depths of the crystal. From the experimental results a DoI discrimination resolution ranging from 4 mm to 6 mm has been obtained. The proposed method is expected to reduce the parallax error and, consequently, the width of lines of response coming from off- center positron annihilation of about 70% respect to the method without DoI discrimination.

The Depth of Interaction (DoI) discrimination of gamma-photons within scintillation crystals allows to improve imaging performance in PET scanners as well as in SPECT devices equipped with non-parallel collimators (e. g. pinhole ones). In previous works, the authors experimentally proved the efficiency of a DoI-encoding technique in case of a 20 mm-thick monolithic crystal PET module. For the thinner crystals commonly used in SPECT, DoI determination still remains a challenging goal. To this aim, in this work the authors have experimentally evaluated the DoI-encoding method on a 6 mm-thick monolithic LaBr3:Ce crystal. The results prove the efficiency and reliability of the proposed method. It indeed allows to discriminate the gamma photons interacting at the the top and the bottom of the crystal.

Dynamic contrast-enhanced cardiovascular magnetic resonance imaging can be used to quantitatively assess the myocardial blood flow (MBF), recovering the tissue impulse response function for the transit of a gadolinium bolus through the myocardium. Several deconvolution techniques are available, using various models for the impulse response. The method of choice may influence the results, producing differences that have not been deeply investigated yet. Three methods for quantifying myocardial perfusion have been compared: Fermi function modelling (FFM), the Tofts model (TM) and the gamma function model (GF), with the latter traditionally used in brain perfusion MRI. Thirty human subjects were studied at rest as well as under cold pressor test stress (submerging hands in ice-cold water), and a single bolus of gadolinium weighing 0.1 ± 0.05 mmol kg-1 was injected. Perfusion estimate differences between the methods were analysed by paired comparisons with Student's t-test, linear regression analysis, and Bland-Altman plots, as well as also using the two-way ANOVA, considering the MBF values of all patients grouped according to two categories: calculation method and rest/stress conditions. Perfusion estimates obtained by various methods in both rest and stress conditions were not significantly different, and were in good agreement with the literature. The results obtained during the first-pass transit time (20 s) yielded p-values in the range 0.20-0.28 for Student's t-test, linear regression analysis slopes between 0.98-1.03, and R values between 0.92-1.01. From the Bland-Altman plots, the paired comparisons yielded a bias (and a 95% CI)-expressed as ml/min/g-for FFM versus TM, -0.01 (-0.20, 0.17) or 0.02 (-0.49, 0.52) at rest or under stress respectively, for FFM versus GF, -0.05 (-0.29, 0.20) or -0.07 (-0.55, 0.41) at rest or under stress, and for TM versus GF, -0.03 (-0.30, 0.24) or -0.09 (-0.43, 0.26) at rest or under stress. With the two-way ANOVA, the results were p = 0.20 for the method effect (not significant), p

The proposal of Mindview European Project concerns with the development of a very high resolution and high efficiency brain dedicated PET scanner simultaneously working with a Magnetic Resonance scanner, that expects to visualize neurotransmitter pathways and their disruptions in the quest to better diagnose schizophrenia. On behalf of this project, we propose a low cost PET module for the first prototype, based on monolithic crystals, suitable to be integrated with a head Radio Frequency (RF) coil. The aim of the suggested module is to achieve high performances in terms of efficiency, planar spatial resolution (expected about 1 mm) and discrimination of gamma Depth Of Interaction (DOI) in order to reduce the parallax error. Our preliminary results are very promising: a DOI resolution of about 3 mm, a spatial resolution ranging from about 1 to 1.5 mm and a good position linearity.

One of the technical objectives of the MindView project is developing a brain-dedicated PET insert based on monolithic scintillation crystals. It will be inserted in MRI systems with the purpose to obtain simultaneous PET and MRI brain images. High sensitivity, high image quality performance and accurate detection of the Depth-of-Interaction (DoI) of the 511keV photons are required. We have developed a DoI estimation method, dedicated to monolithic scintillators, allowing continuous DoI estimation and a DoI-dependent algorithm for the estimation of the photon planar impact position, able to improve the single module imaging capabilities. In this work, through experimental measurements, the proposed methods have been used for the estimation of the impact positions within the monolithic crystal block. We have evaluated the PET system performance following the NEMA NU 4-2008 protocol by reconstructing the images using the STIR 3D platform. The results obtained with two different methods, providing discrete and continuous DoI information, are compared with those obtained from an algorithm without DoI capabilities and with the ideal response of the detector. The proposed DoI-dependent imaging methods show clear improvements in the spatial resolution (FWHM) of reconstructed images, allowing to obtain values from 2mm (at the center FoV) to 3mm (at the FoV edges).

Nuclear medicine imaging devices commonly use multi-element photo detection systems, composed of an array of N × N elements, each one providing an individual signal. Many strategies have been developed to reduce the number of readout channels, one of the main approaches is the Rows and Columns (R/C) projection logic. In this paper we proposed a modified version of Raised To the Power (RTP) algorithm adapted to R/C logic. In order to validate its efficiency a linear scanning irradiation on two 49× 49 mm2 LaBr3:Ce (0.5%) crystals with different thickness (4 mm and 10 mm) was carried out. Imaging performance analysis was made in terms of position linearity, Field-of-View (FoV) enlargement and spatial resolution. Imaging results from Anger Logic, RTP algorithm based on single element readout and RTP algorithm based on R/C readout were compared. A notable advantage of using RTP algorithms instead of Anger Logic was found: the FoV widens from about 30% to more than 70% of the detector area whereas the spatial resolution is highly improved, especially for off-center interactions, both for 4 mm-thick and 10 mm-thick crystals. Furthermore, imaging performance with the R/C readout is just slightly different from the single element one (FoV reduction less than 7% and SR worsening less than 10%). The R/C adapted RTP algorithm opens doors to high imaging performance with a substantial reduction of complexity and cost in the readout electronics.