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Abstract: The characterization of novel x-ray sources includes the measurement of the photon flux and the energy distribution of the beam produced. The aim of the BEATS2 experiment at INFN-LNF is the study of medical applications of an x-ray source based on Thomson relativistic backscattering. This source is expected to produce pulsed quasi-monochromatic x-ray beam with an instantaneous flux of 1020 ph/s in pulses 10ps long and with an average energy of 20keV. A direct measurement of energy distribution of this beam with traditional detectors, such as HPGe, CZT or CdTe, is very difficult because of the extremely high photon flux. For this reason we have planned to use a technique based on beam filtration using k-edge absorbing foils in the energy range of interest (16–22keV). By measuring the photon flux of the photon beam filtered with appropriate thicknesses of k-edge absorbers, it is possible to retrieve the energy distribution of the incident x-ray beam. The energy resolution obtainable depends on the number and energy separation of k-edges of filter used. A preliminary test of the technique was made using an x-ray tube with a tungsten anode at 22kVp, filtered with 3.1mm of Al providing an x-ray spectrum with an energy distribution similar to that expected from a Thomson source. The comparison between the results obtained directly measuring this spectrum with an HPGe detector and using the k-edge subtraction technique showed good agreement. [Copyright &y& Elsevier]

Abstract: Nonlinear effects in vacuum have been predicted but never observed yet directly. The PVLAS collaboration has long been working on an apparatus aimed at detecting such effects by measuring vacuum magnetic birefringence. Unfortunately the sensitivity has been affected by unaccounted noise and systematics since the beginning. A new small prototype ellipsometer has been designed and characterized at the Department of Physics of the University of Ferrara, Italy entirely mounted on a single seismically isolated optical bench. With a finesse F =414,000 and a cavity length L =0.5m we have reached the sensitivity of given the laser power at the output of the ellipsometer of P =24mW. This record result, very close to the predicted limit, demonstrates the feasibility of reaching such sensitivities, and opens the way to designing a dedicated apparatus for a first detection of vacuum magnetic birefringence. [ABSTRACT FROM AUTHOR]

The University of Ferrara YAP-(S)PET scanner is currently being employed in small animal SPECT studies, with [sup99m]Tc labeled radiotracers, with the goal of obtaining quantitative activity measurements from region of interest (ROI) analysis of reconstructed images of rats. The measurements will be compared directly with traditional ex vivo measurement of activity with gamma counters. To achieve this goal, the scanner was calibrated relative to a standard Isodose dose calibrator which was calibrated with various certified activity sources. The calibration factor K was defined as the ratio of the activity measured with the Isodose (MBq) and the image count rate (cps). We find K = 0.1346 ± 0.0008 MBq/cps, with good linearity over a wide range of activities (9-88 MBq). With the calibrated scanner we compared results of activity measurements from images of whole-rat heart acquisitions versus excised hearts. We found good agreement between the two measurements. [ABSTRACT FROM AUTHOR]

A prototype of a combined CT–SPECT tomograph for breast cancer study has been developed and evaluated. It allows to perform scintimammography and X-ray CT in the same geometrical conditions. The CT system is based on a quasi-monochromatic beam tuned at 28 keV and an array of ultra fast ceramic scintillators coupled to photodiodes whilst the SPECT system is based on two scintillator matrices coupled to position sensitive photomultipliers. CT and SPECT sinograms of a test phantom were recorded and reconstruted with both modalities. Image fusion of CT and SPECT images was then performed. The developed CT–SPECT prototype is able to detect a region of interest of 1 cm3, with a 10:1 tumour/background concentration ratio, within an object having a diameter of 8 cm. [Copyright &y& Elsevier]

A dedicated small animal PET scanner, YAPPET, was designed and built at Ferrara University. Each detector consists of a 20×20 matrix of 2×2×30 mm3 YAP:Ce finger-like crystals glued together and directly coupled to a Hamamatsu position sensitive photomultiplier. The scanner is made from four detectors positioned on a rotating gantry at a distance of 7.5 cm from the center and the field of view (FOV) is 4 cm both in the transaxial direction and in the axial direction. The system operates in 3D acquisition mode. The performance parameters of YAPPET scanner such as spatial, energy and time resolution, as well as its sensitivity and counting rate have been determined. The average spatial resolution over the whole FOV is 1.8 mm at FWHM and 4.2 mm at FWTM. The sensitivity at the center is 640 cps/μCi. [Copyright &y& Elsevier]

Provides information on a study which designed, built and tested a small animal Positron Emission Tomograph (YAP-PET) based on four matrices of YAP:Ce finger crystals. Experimental apparatus; Experimental results; Conclusions.

Presents information on experimental data which is used for Planar Imaging with positron emitters, focusing on the EGS4 code simulation. What are positron emitters; How positron emitters are obtained; Details on the EGS4 code simulation; Concepts of the EGS4 code simulation.

Abstract: The PVLAS experiment aims at the observation and measurement of the effect of magnetic birefringence of vacuum (MBV) predicted by Quantum Electrodynamics. We describe here the new PVLAS apparatus which is currently being set up in INFN Ferrara. The apparatus features two rotating permanent dipole magnets and an ellipsometer operating under UHV with a high finesse Fabry–Perot cavity. [Copyright &y& Elsevier]

The Gamma Beam System of ELI-Nuclear Physics is a high brilliance monochromatic gamma source based on the inverse Compton interaction between an intense high power laser and a bright electron beam with tunable energy. The source, currently being assembled in Magurele (Romania), is designed to provide a beam with tunable average energy ranging from 0.2 to 19.5 MeV, rms energy bandwidth down to 0.5 % and flux of about 1 0 8 photons/s. The system includes a set of detectors for the diagnostic and complete characterization of the gamma beam. To evaluate the spatial distribution of the beam a gamma beam profile imager is required. For this purpose, a detector based on a scintillator target coupled to a CCD camera was designed and a prototype was tested at INFN-Ferrara laboratories. A set of analytical calculations and Monte Carlo simulations were carried out to optimize the imager design and evaluate the performance expected with ELI-NP gamma beam. In this work the design of the imager is described in detail, as well as the simulation tools used and the results obtained. The simulation parameters were tuned and cross-checked with the experimental measurements carried out on the assembled prototype using the beam from an x-ray tube. [ABSTRACT FROM AUTHOR]

A prototype x-ray system based on a liquid-metal-jet anode was evaluated within the framework of the LABSYNC project. The generated spectrum was measured using a CZT-based spectrometer and was compared with spectra simulated by three Monte Carlo codes: MCNPX, PENELOPE and EGS5. Notable differences in the simulated spectra were found. These are mainly attributable to differences in the models adopted for the electron-impact ionization cross section. The simulation that more closely reproduces the experimentally measured spectrum was provided by PENELOPE. [ABSTRACT FROM AUTHOR]

Purpose: A 3-year project called LABSYNC has been recently funded by the European Commission, with the aim of designing a radiation facility based on a compact light source, i.e., a laboratory-sized commercial synchrotron, capable of accelerating electrons up to 6 or 20 MeV. An accurate spectral description of hard x rays emitted from thin targets, irradiated by electron beams circulating in the storage ring, is of primary interest for the design and the characterization of a beamline. This article, Part I, aims at optimizing some of the parameters which are critical for the design of medical applications based on the above compact light source. The goal was to evaluate the dependence of photon fluence and beam monochromaticity on electron-beam energy, target material, and thickness. Methods: The transport of 6 and 20 MeV electrons in a thin molybdenum, rhodium, and tungsten target is studied by means of Monte Carlo simulations using MCNPX. Configurations of the x-ray output port, different from the default forward-directed emission of the beam, are also investigated. A comparison with reference spectra for general diagnostic radiology and mammography is carried out. Results: It is shown that the emitted x-ray beams can be far more intense than those generated by conventional x-ray tubes for radiography applications. The profiles of the calculated polychromatic spectra resemble those generated by conventional x-ray tubes, with x-ray energies up to the energy of the incident-electron beam. An appreciable improvement in the monochromaticity of the beams can be obtained by viewing the x-ray emission from an output port antiparallel to the direction of the incident-electron beam. Conclusions: The optimum target thickness for tungsten target spectra is practically constrained by a trade-off between bremsstrahlung efficiency and focal-spot size requirements. A larger margin for optimization of target thickness is probably available for mammographic spectra. The constraint of a backward-directed (or, to a lesser extent, orthogonal) output port is to be considered mandatory for minimizing the high-energy tail of the spectral distribution and keeping the radiation dose to a reasonable level. It is also fundamental to evaluate the impact of the high-energy tail of the emitted spectra in x-ray imaging applications, since the energy range involved is significantly beyond the diagnostic range. This topic will be dealt with in Part II of the article. [ABSTRACT FROM AUTHOR]

We have manufactured more than 250 nominally identical paraffin-coated Cs vapor cells (28 mm inner diameter bulbs) for multi-channel atomic magnetometer applications. We describe our dedicated cell characterization apparatus. For each cell we have determined the intrinsic longitudinal, Γ01, and transverse, Γ02, relaxation rates. Our best cell shows Γ01/2 π≈0.5 Hz, and Γ02/2 π≈2 Hz. We find a strong correlation of both relaxation rates which we explain in terms of reservoir and spin exchange relaxation. For each cell we have determined the optimal combination of rf and laser powers which yield the highest sensitivity to magnetic field changes. Out of all produced cells, 90% are found to have magnetometric sensitivities in the range of 9 to 30 fT $\sqrt{\mathrm{Hz}}$ . Noise analysis shows that the magnetometers operated with such cells have a sensitivity close to the fundamental photon shot noise limit. [ABSTRACT FROM AUTHOR]

Abstract: In the past years we were able to show that room temperature optical magnetometers based on magnetic resonance in atomic vapors can be used to measure magnetocardiographic (MCG) signals of healthy adults. The objective of our ongoing work is to demonstrate that multichannel arrangements of affordable and maintenance-free optical magnetometers can be operated in clinical settings. On the way to that goal we studied a new optical magnetometry scheme using linearly polarized light. We also investigated the possibility to operate such magnetometers in inexpensive magnetic shielding rooms based on aluminum. [Copyright &y& Elsevier]

Abstract: We investigated the capabilities of a small animal PET scanner, named SiliPET, based on four stacks of double sided silicon strips detectors. Each stack consists of 40 silicon detectors with dimension . These are arranged to form a box with minor sides opened; the box represents the maximal FOV of the scanner. The performance parameters of SiliPET scanner have been estimated, giving an intrinsic spatial resolution of 0.52mm and a sensitivity of 5.1% at the center of the system. [Copyright &y& Elsevier]

The precision of atomic state measurements should ideally be limited by irreducible fluctuations associated with the number of atoms available, e.g. shot noise or quantum projection noise. In practice, other noise sources can limit the precision achievable; a well-known effect is the intermodulation effect, or Dick effect, which degrades the stability of atomic fountain clocks using pulsed sources. One way to beat this source of instability consists of interrogating the atoms with a microwave signal derived from exceptionally stable local oscillators, such as cryogenic oscillators, which are however bulky and not ideally suited to the constraints of space. Another way of reaching atomic-noise limited instability is to use continuous sources of cold atoms. Experimental results obtained both on a fountain standard and on an experimental Cs fountain illustrate the potential of continuous cold atomic beams for improving signal-to-noise ratio and precision of measurement. Current developments towards higher atomic beam flux are also described. [ABSTRACT FROM AUTHOR]

We describe transverse collimation of a continuous cold cesium beam (longitudinal temperature 75 μK) induced by a two-dimensional, blue-detuned near-resonant optical lattice. The mechanism described for a lin-||-lin configuration is made possible by the application of a transverse magnetic field B⊥. The phenomenon described differs from gray molasses, for which any small magnetic field degrades cooling, as well as from magnetically induced laser cooling in red-detuned optical molasses, where there are no dark states. The lowest transverse temperature is experimentally found to vary as B⊥2. The collimated flux density shows a dip as a function of B⊥, the width of which is proportional to the cube root of the laser intensity, general features predicted by our semiclassical model. This technique provides a sensitive tool for canceling transverse magnetic fields in situ at the milligauss level. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

Presents information on the results of small animal PET applications using a YAP:Ce scintillator. Details on how it worked; Information on the proper crystal depth; Identification of the setting that the crystals were used at.

ELI-NP-GBS is a high-brilliance gamma source that will produce monochromatic beams in the energy range 0.2–19.5 MeV through inverse Compton scattering. In order to obtain a monochromatic beam a collimation of the emission is necessary. Depending on the energy, the angular aperture required to provide the design bandwidth Δ E/E=0.5% is between 70 and 700 μ rad. This collimation is provided by a stack of 14 tungsten slits, arranged with a relative rotation around the beam axis, so that the overlap will be a continuously adjustable aperture. To monitor the operation and alignment of the collimation, a set of detectors will provide a complete characterization of the gamma beam, including the measurement of the transverse spatial distribution. For this task a gamma beam profile imager based on a thin scintillator screen and a high-resolution CCD-camera was developed. In this work we briefly present the status of the collimation system and beam profile imager, which were designed, assembled and are currently under test at INFN-Ferrara laboratories. [ABSTRACT FROM AUTHOR]

We demonstrate both theoretically and experimentally that edge-enhancement effects are produced when objects, in contact with the x-ray detector, are imaged by using very broad x-ray spectra. Radiographs of thin Al objects have been obtained with a table-top synchrotron source which generates x-rays in the energy range from a few kilo-electron-volts up to 6 MeV. Edge-enhancement effects arise from the combination of x-ray absorption (kilo-electron-volt part of the spectrum) and secondary particle emission (mega-electron-volt part of the spectrum) within the sample. The exact contribution of absorption and emission profiles in the edge-enhanced images has been calculated via Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

Abstract: We studied with Monte Carlo simulations, using the EGSnrc code, a new scanner for small animal positron emission tomography (PET), based on stacks of double-sided semiconductor detectors. Each stack is composed of planar detectors with dimension 70×60×1mm3 and orthogonal strips on both sides with 500μm pitch to read the two interaction coordinates, the third being the detector number in the stack. Multiple interactions in a stack are discarded. In this way, we achieve a precise determination of the first interaction point of the two 511keV photons. The reduced dimensions of the scanner also improve the solid angle coverage resulting in a high sensitivity. Preliminary results of scanners based on Si planar detectors are presented and the initial tomographic reconstructions demonstrate very good spatial resolution limited only by the positron range. This suggests that, this is a promising new approach for small animal PET imaging. We are testing some double-sided silicon detectors, equipped with 128 orthogonal p and n strips on opposite sides using VATAGP3 ASIC by IDEAS. [Copyright &y& Elsevier]

The ELI-NP facility will provide a monochromatic, high brilliance γ beam with tunable energy up to 19.5 MeV. The time structure of the beam consists of 32 pulses of 1 0 5 photons separated by 16 ns and delivered at repetition rate of 100 Hz. In order to match such unprecedented beam specifications and to measure its energy spectrum, intensity and space profile, a characterization system has been developed. This paper will focus on the working principle, the expected performances and the results of tests carried out on a low-Z sampling calorimeter, made of silicon detectors and polyethylene absorbers, which will measure the average beam energy and its intensity. The results of tests performed with an infrared pulsed laser have shown the capability of the detector to cope with the time structure of ELI-NP beam. Further tests carried out at the LABEC facility in Firenze have shown the excellent linearity of the silicon detectors in the energy range relevant to ELI-NP beam. [ABSTRACT FROM AUTHOR]

The ELI-NP facility, currently being built in Bucharest, Romania, will deliver an intense and almost monochromatic γ beam with tunable energy between 0.2 MeV and 19.5 MeV in two different beamlines. An articulated beam characterization system will be installed downstream of the collimator of each line. The system will use, as calibration candles, a few selected nuclear levels whose fluorescence condition will be monitored by a Nuclear Resonance Scattering System (NRSS). The NRSS will use a peculiar double-readout approach in order to detect resonant events overwhelming background: both scintillation and Cherenkov photons produced inside the same crystals will be separately read. • The NRS system will play a crucial role in the characterization of the Eli-NP beam. • It will be able to give a precise absolute energy calibration of the gamma beam. • The determination of the resonance will be achieved using a matrix of BaF/LYSO crystals. • A novel double readout technique shows a very good background rejection power. [ABSTRACT FROM AUTHOR]

The ELI-NP facility (Extreme Light Infrastructure-Nuclear Physics) will deliver an intense and almost monochromatic gamma beam for frontier research in nuclear physics. Peculiar devices and techniques have been developed to measure and monitor the beam parameters during the commissioning and the operational phase. In this work we will present the Compton Spectrometer, designed to reconstruct the γ beam energy spectrum, by measuring the energy and the position of Compton scattered electrons. The energy and the angle of the scattered electron are measured by a High Purity Germanium detector and a double sided silicon strip detector. The associated photon is detected in coincidence with the electron by barium fluoride (BaF 2) crystals for trigger purpose. In this work we report the status of the characterization carried out on the detectors composing the spectrometer. • Compton spectrometer, designed to reconstruct the ELI-NP γ beam energy spectrum. • Energy of the scattered e − measured with a High Purity Germanium detector. • Scattered angle determined by a double sided silicon strip detector. • Scattered photon detected in coincidence by BaF 2 crystals for trigger purpose. • Tests carried out on the components of the spectrometer are presented. [ABSTRACT FROM AUTHOR]

We report the direct observation of the onset of turbulence in propagating one-dimensional optical waves. The transition occurs as the disordered hosting material passes from being linear to one with extreme nonlinearity. As the response grows, increased wave interaction causes a modulational unstable quasihomogeneous flow to be superseded by a chaotic and spatially incoherent one. Statistical analysis of high-resolution wave behavior in the turbulent regime unveils the emergence of concomitant rogue waves. The transition, observed in a photorefractive ferroelectric crystal, introduces a new and rich experimental setting for the study of optical wave turbulence and information transport in conditions dominated by large fluctuations and extreme nonlinearity. [ABSTRACT FROM AUTHOR]

A Gamma Beam Characterisation System has been designed by the EuroGammaS association for the commissioning and development of the Extreme Light Infrastructure-Nuclear Physics Gamma Beam System (ELI-NP-GBS) to be installed in Magurele, Romania. The characterisation system consists of four elements: a Compton spectrometer, a sampling calorimeter, a nuclear resonant scattering spectrometer (NRSS) and a beam profile imager. In this paper, the nuclear resonant scattering spectrometer system, designed to perform an absolute energy calibration for the gamma beam, will be described. [ABSTRACT FROM AUTHOR]

At Legnaro laboratories of the Italian National Institute for Nuclear Physics (INFN), a feasibility study has started since 2011 related to accelerated-based direct production of 99mTc by the 100Mo(p,2n) 99mTc reaction. Both theoretical investigations and some recent preliminary irradiation tests on 100Mo-enriched samples have pointed out that both the 99gTc/ 99mTc ratio and the 99mTc specific activity will be basically different in the final accelerator-produced Tc with respect to generator-produced one, which might affect the radiopharmaceutical procedures. The aimof this work was to evaluate the possible impact of different 99gTc/99mTc isomeric ratios on the preparation of different Tc-labeled pharmaceutical kits. A set of measurements with 99mTc, eluted from a standard 99Mo/ 99mTc generator, was performed, and results on both radiochemical purity and stability studies (following the standard quality control procedures) are reported for a set of widely used pharmaceuticals (i.e., 99mTc-Sestamibi, 99mTc-ECD, 99mTc-MAG3, 99mTc-DTPA, 99mTc-MDP, 99mTc-HMDP, 99mTc-nanocolloids, and 99mTc-DMSA). These pharmaceuticals have been all reconstituted with either the first [ 99mTcO4]- eluate obtained from a 99Mo/ 99mTc generator (coming from two different companies) or eluates after 24, 36, 48, and 72 hours from last elution. Results show that the radiochemical purity and stability of these radiopharmaceuticals were not affected up to the value of 11.84 for the 99gTc/ 99mTc ratio. [ABSTRACT FROM AUTHOR]

Abstract: MIRRORCLE is a tabletop synchrotron light source being investigated within an EC funded project named LABSYNC. To evaluate the potential of this novel x-ray source for medical imaging applications, a set of measurements was performed at the MIRRORCLE factory in Japan. In particular, the aim of this work was to characterize the proposed compact x-ray source by determining different parameters, such as the intensity of the broad spectra produced with thin wire targets, the size of the focal spot and its distribution. The average electron-beam impact current on wire targets was calculated by several methods and it was demonstrated to be in the range . By comparing these values with data available for conventional x-ray tubes, the current needed to achieve the same fluence as in a standard diagnostic examination was estimated to be about 0.1–0.5mA. Finally, results from the measurements of the electron-beam impact cross-section on the target suggested that the diameter of the electron beam circulating in the storage ring is about 6mm. [Copyright &y& Elsevier]

Abstract: We report a new precise measurement of the Cotton–Mouton effect in helium at T ≃290K for the two wavelengths λ =532nm and λ =1064nm. The hypermagnetizability anisotropy Δη for helium is 0.92±0.07au at the wavelength of 532nm and 0.98±0.07au at the wavelength of 1064nm: these values agree well with the theoretical calculations. [Copyright &y& Elsevier]

Abstract: Lobster-ISS is an X-ray all-sky monitor experiment selected by ESA two years ago for a Phase A study (now almost completed) for a future flight (2009) aboard the Columbus Exposed Payload Facility of the International Space Station. The main instrument, based on MCP optics with Lobster-eye geometry, has an energy passband from 0.1 to 3.5keV, an unprecedented daily sensitivity of 2×10−12 ergcm−2 s−1, and it is capable to scan, during each orbit, the entire sky with an angular resolution of 4–6′. This X-ray telescope is flanked by a Gamma Ray Burst Monitor, with the minimum requirement of recognizing true GRBs from other transient events. In this paper we describe the GRBM. In addition to the minimum requirement, the instrument proposed is capable to roughly localize GRBs which occur in the Lobster FOV (162×22.5°) and to significantly extend the scientific capabilities of the main instrument for the study of GRBs and X-ray transients. The combination of the two instruments will allow an unprecedented spectral coverage (from 0.1 up to 300/700keV) for a sensitive study of the GRB prompt emission in the passband where GRBs and X-Ray Flashes emit most of their energy. The low-energy spectral band (0.1–10keV) is of key importance for the study of the GRB environment and the search of transient absorption and emission features from GRBs, both goals being crucial for unveiling the GRB phenomenon. The entire energy band of Lobster-ISS is not covered by either the Swift satellite or other GRB missions foreseen in the next decade. [Copyright &y& Elsevier]

When measuring very small ellipticities or rotations induced on a polarized beam of light, Fabry–Pérot cavities are often used to increase the number of passes within the region of interest. In this paper we show that due to the intrinsic birefringence of the reflective surface of the cavity mirrors, a cross talk between dichroism and ellipticity is induced. We also show how such a cross talk may be measured and kept under control by means of an adequate phase locking scheme of the laser to the cavity. [ABSTRACT FROM AUTHOR]

Abstract: In this Letter, we report a novel measurement of the magnetically induced birefringence (Cotton–Mouton effect) in neon. Using a highly sensitive apparatus we were able to precisely measure the specific birefringence value of Δn u =(5.9±0.2)×10−16 at the wavelength of 1064nm (for B =1T and atmospheric pressure) and T ≈290K. The results reported here are in agreement with theory, while the only previous precise measurement differs significantly. [Copyright &y& Elsevier]

In this Letter we report a novel measurement of the magnetically induced birefringence (Cotton–Mouton effect) in krypton and xenon. The measurement is performed, with the apparatus of the PVLAS experiment, at the previously uninvestigated wavelength of 1064 nm. [Copyright &y& Elsevier]

Compact gamma cameras based on arrays of compact Position Sensitive Photomultipliers (PSPMTs) (Hamamatsu R7600–C8/12) were recently developed by several research groups. The previous generation of dedicated gamma cameras (5 in. PSPMT) demonstrated the clinical benefit and general diagnostic value for functional breast imaging in comparison with conventional nuclear medicine technique (Anger Camera prone scintimammography and 99mTc Sestamibi administration). The aim of this paper is to investigate how scintillation material and pixel size of crystal arrays can improve image contrast and tumor SNR values. In this paper we compare tumor Signal-to-Noise Ratio (SNR) results obtained by imagers based on CsI(Tl) and NaI(Tl) array, respectively, by means of a liquid and solid breast phantom. The data collected by NaI(Tl) array show a improvement of SNR values for small tumor size (less than 8 mm). The improvement is also evident in small camera, even though for tumor size less than 6 mm the results are near visibility limit. [Copyright &y& Elsevier]

We have been investigating the possibility to readout a large number of crystals (more than 400) by means of WaveLength Shifting (WLS) square section fibers and multi-pixel Hybrid PhotoDiodes (HPDs) for PET applications. However, due to the small light yield, the detection efficiency for 511 keV photons could be too low. To overcome this limitation, we have recently proposed to shape the surface of each finger crystal like an “half-pipe” to achieve a better scintillator—WLS fiber coupling. In this paper, we present the results of the light yield experimental measurements on a test 5×5 “half-pipe” YAP:Ce crystal matrix and a comparison with square fibers—standard matrix configuration.In view of future availability of large-area HPD, we have also assembled a small detector head using a test 4×4 YAP:Ce crystal matrix directly coupled to a 61-pixel HPD. Experimental measurements on the imaging capabilities are also presented. [Copyright &y& Elsevier]

Describes an animal PET-SPECT scanner prototype. Problem with the use of the first YAP-(S)PET prototype; Features of the scanner prototype; Performance of the electronic prototype.

Objective. We would like to improve the image reconstructions for both signal-to-noise ratio (SNR) and spatial resolution characteristics for the small animal positron emission tomograph YAP–PET, built at the Department of Physics of Ferrara University. The three-dimensional (3D) filtered backprojection (FBP) algorithm, usually used for image reconstruction, has a limited angle restriction due to the tomograph geometry, which causes a serious loss in sensitivity.Methods. We implemented a 3D iterative reconstruction program using the symmetry and sparse properties of the ‘probability matrix’, which correlates the emission from each voxel to the detector within a coincidence tube. A fraction only of matrix elements are calculated before the reconstruction and stored on disk: this allows us to avoid on-line computation. A depth dependent function differentiates the voxels in a coincidence tube. Three experimental phantoms with no background were reconstructed by using the program, in comparison with traditionally used FBP.Results. The adopted method allowed us to reduce the computation time significantly. Furthermore, the simple depth dependent function improved the spatial resolution. With 64×64×20 voxels of 0.625×0.625×2.0 mm3 in the field of view, the computation time was less than 4 min per iteration on a Sparc Ultra450 Workstation, and less than 6 min per iteration on a Mac-PPC G3 300 MHz: the spatial resolution measured with a 0.8 mm diameter 18F-FDG filled capillary reconstructed in this way was 2.0 mm FWHM. By decreasing the voxel size to 0.3125×0.3125×2.0 mm3 per voxel the transaxial FWHM was 1.7 mm with a computation time of 15 min per iteration on a Sparc Ultra450. By using all the acquired data, the SNR improves from 1.3 to 6.0 in the worst measured case, a pair of 0.8 mm diameter 18F-FDG filled capillaries, which are 2.5 mm apart each other.Conclusion. The adoption of iterative reconstruction allowed us to overcome the loss in sensitivity of previously used FBP: this improved the SNR. The studies of symmetry and sparse properties avoided a severe increase of the reconstruction time and of storing space on disk. This fast EM Algorithm is now routinely used for the image reconstruction with the YAP–PET tomograph. [Copyright &y& Elsevier]

Presents a set of preliminary results of a detector phototype for positron emission tomography application. Experimental measurements with a single-pixel photodiodes; Description of the parts of a detector and the light transport through the system; Schematic diagram of the experimental setup used in the position measurement.

Presents information on a study which developed a combined single photon emission computed tomography-CT tomographic imager for breast cancer study. Experimental setup; System evaluation and results; Conclusions.

We propose and provide experimental evidence of a mechanism able to support negative intrinsic effective mass. The idea is to use a shape-sensitive nonlinearity to change the sign of the mass in the leading linear propagation equation. Intrinsic negative-mass dynamics is reported for light beams in a ferroelectric crystal substrate, where the diffusive photorefractive nonlinearity leads to a negative-mass Schrödinger equation. The signature of inverted dynamics is the observation of beams repelled from strongly guiding integrated waveguides irrespective of wavelength and intensity and suggests shape-sensitive nonlinearity as a basic mechanism leading to intrinsic negative mass. [ABSTRACT FROM AUTHOR]

Presents a correction to the article 'Preliminary Test Results on the New Electronic Read Out of the YAP-(S)PET Small Animal Scanner.'