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Recently, dual-modality systems have been developed, aimed to correlate anatomical and functional information, improving disease localization and helping oncological or surgical treatments. Moreover, due to the growing interest in handheld detectors for preclinical trials or small animal imaging, in this work a new dual modality integrated device, based on a Ultrasounds probe and a small Field of View Single Photon Emission gamma camera, is proposed. © 2018 Elsevier Ltd

The ECORAD collaboration aims at developing a dual compact camera for acquiring ultrasound and scintigraphic images, in order to get both morphological and functional information on the same device. A final volumetric image containing the fusion information will be provided to the user. Here we present the first simulated results of the scintigraphic camera, achieved by means of the GEANT4 program. The camera is based on a four-segment slant collimator. Each segment is coupled with a planar LaBr3(Ce) scintillator and to a Position Sensitive Photo-Multiplier Tube. We tested two different centroid algorithms for reconstructing the planar images. The 3D information is recovered from the planar images acquired at each position of the rotating collimator by using a simple back-projection algorithm. The proposed approach of a scintigraphic camera based on slant collimators is able to recover the location and the depth of a lesion in a very accurate way.

The development of the molecular imaging technique based on radiopharmaceuticals is requiring sophisticated devices with sub-millimeter spatial resolution and high detection efficiency. Recently, in the field of scintillation gamma camera, it has been demonstrated that continuous crystals may improve spatial resolution with respect to the use of scintillation arrays. In this work we propose a new algorithm that improves spatial resolution. It calculates the position from a single scintillation event by squaring the charge collected on a multi-anodes photomultiplier tube (MA-PMT). It is able to remove the position linearity distortion due to the light reflections and the truncations at the crystal edge. We present measurements from a compact gamma camera based on a 51 mm × 51 mm × 4.0 mm LaBr3:Ce continuous scintillation crystal, coupled to a MA-PMT Hamamatsu H8500. The results show a strong improvement in spatial resolution and confirm the high potential in using of LaBr continuous crystal for molecular imaging applications. © 2009 Elsevier B.V. All rights reserved.

The performance of the new prototype of high quantum efficiency PMT (43% at 380 nm), Hamamatsu R7600U-200, was studied coupled to a LaBr 3 :Ce crystal with the size of ∅12.5 mm×12.5 mm. The energy resolution results were compared with ones from two PMTs, Hamamatsu R7600U and R6231MOD, with 22% and 30% quantum efficiency (QE), respectively. Moreover, the photodetectors were equipped with tapered and un-tapered voltage dividers to study the non-linearity effects on pulse height distribution, due to very high peak currents induced in the PMT by the fast and intense light pulse of LaBr 3 :Ce. The results show an energy resolution improvement with UBA PMT of about 20%, in the energy range of 80–662 keV, with respect to the BA one.

The very low sensitivity of Scintimammography for tumors under 1 cm in diameter, with current nuclear medicine cameras in use, is the major limitation in recommending this test modality for screening purposes. Recently latest generation cameras with superior imaging performances have allowed to foresee a very promising future for scintimammography. Recent technological advances obtained from our research group on the new Lanthanum scintillation crystals are now demonstrating how continuous crystals coupled to Hamamatsu Flat panel tube can overcome a number of limitations in spatial and energy resolution of scintillation arrays, carrying out 6% energy resolution, and submillimeter spatial resolution values at 140 keV. In this paper three basic detection systems have been analysed: a LumaGEM 3200S gamma camera (Gamma Medica, InC., Northridge, USA), based on a cadmium–zinc–telluride (CZT) semiconductor detector with a FoV of 12.5×12.5 cm 2 and with detector elements of 1.6×1.6 mm 2 in size and a detector prototype consisting of a Flat panel PMT coupled to planar LaBr 3 :Ce scintillator. The third one is a first generation large FoV gamma camera chosen for comparison, based on PSPMTs photodetector array coupled to a NaI(Tl) scintillation crystal matrix. LaBr 3 :Ce and CZT cameras showed superior spatial and energy resolution than previous generation one based on NaI(Tl) scintillation array. Both CZT and LaBr gamma cameras showed similar efficiencies for the same energy window though LaBr 3 :Ce continuous crystal showed better imaging performance than pixellated detectors. However large area LaBr 3 :Ce continuous crystals are not available yet.

The aim of the ECORAD collaboration is to develop a dual integrated compact and portable camera able to acquire ultrasound and scintigraphic images at the same time. In this work, we present some simulated results of the scintigraphic part of the system. This camera consists of a rotating slant collimator with four segments connected to a planar LaBr3:Ce scintillator and to a PMT Hamamatsu Flat Panel H8500. Simulations are achieved by means of the GEANT4 program. The volumetric information is reconstructed from the planar images acquired at each position of the rotating collimator by means of a simple back-projection method. Results showed that the planar spatial resolution is better that the axial one. First preliminary results suggest that the detection limit of the camera is about 15:1 (in terms of Tumor/Background ratio) for a spherical tumor with 8 mm diameter located at 3 cm distance from the collimator. This confirms that with our approach it is feasible to develop a compact camera able to recover the 3D position of lesions located at small depths (up to some centimeters), without the need of rotating the camera around the body.

188 Re is a beta and gamma emitter used in metabolic radiotherapy. SCINTIRAD is a multidisciplinary collaboration that aims at determining the radio-response of 188 Re in cells “in vitro” and the biodistribution in different organs of mice “in vivo”, and studying the therapeutic effect on liver and other tumours induced in mice. Several tumour cell lines have been treated “in vitro” with a 188 Re solution. The dosimetry of 188 Re used to target the different lines of cancer cells has been evaluated using GEANT4, and preliminary results are presented. Studies to optimize the imaging of 188 Re “in vivo” have also continued, including the characterization of H8500 Flat Panel PMT and of LaBr 3 crystals, and the development of dedicated electronics.

In these years a great interest has been growing for the cerium-doped lanthanum crystals due to their high scintillation yield well-matched to present photocathodes, which makes them promising for nuclear medical imaging. In this paper we report on the LaCl3:Ce scintillation response, with the aim to evaluate its degree of non-proportionality. Light yields of LaCl3:Ce, expressed in photoelectron numbers, were measured for X-ray and γ -energies ranging between 13.4 and 1332 keV . In the same energy range, the energy resolution was also measured. The test was performed with a 25 × 25 × 3 mm 3 crystal mounted on a Hybrid Photomultiplier Tube (HPMT) PP0470 by DEP. We observed the presence of two different ranges of LaCl3:Ce light yield response, respectively, for energies higher than 22Na- 511 keV and for energies lower than 57Co- 122 keV . A sensible difference of light yield was observed in these two regions.

In this paper the response in term of pulse height linearity of two Hamamatsu photomultipliers is investigated, when coupled to a LaBr 3 :Ce scintillation crystal. The two photodetectors have high quantum efficiency and in particular 30% for R6231-01 and 42% for R7600-200 tube. The substantial difference is in the dynode structure, linear focused and metal channel for R6231 and R7600 respectively. In this work in order to verify the non-linearity effects on the pulse height distribution, due principally to the high and fast light production of LaBr 3 :Ce scintillator, we propose a ‘peak by peak’ procedure to calibrate the pulse height distribution. Utilizing a specific fragmentation of the calibration curve in subsets, the calculated energy values are very similar for both PMTs. This result confirmed the potentiality of the procedure to highlight the non-linearity effects on pulse height distribution.

Recently scintillating crystals with high light yield coupled to photodetectors with high quantum efficiency have been opening a new way to make gamma cameras with superior performances based on continuous crystals. In this work we propose the analysis of a gamma camera based on a continuous LaBr3:Ce crystal coupled to a multi-anodes photomultiplier tube (MA-PMT). In particular we take into account four detector configurations, different in crystal thicknesses and assembling. We utilize a new position algorithm to reduce the position non linearity affecting intrinsic spatial resolution of small FoV gamma cameras when standard Anger algorithm is applied. The experimental data are obtained scanning the detectors with 0.4 mm collimated 99 m Tc source, at 1.5 mm step. An improvement in position linearity and spatial resolution of about a factor two is obtained with the new algorithm. The best values in terms of spatial resolution were 0.90 mm, 0.95 mm and 1.80 mm for integral assembled, 4.0 mm thick and 10 mm thick LaBr3:Ce crystal respectively.

In this work we propose an analysis of a novel Low Energy (LE) parallel hole collimator for high resolution SPET applications. The tested prototype, realized jointly with Nuclear Fields, is a lead parallel hole collimator with 1.0 mm hexagonal hole, 18 mm length, 0.2 mm septa and 10x10 cm2 of useful detection area. It was planned to match the high spatial resolution performances of a compact gamma camera based on LaBr3(Ce) continuous scintillation crystal. The imaging performance of this prototype is compared with a tungsten pinhole collimator (1.0 mm diameter) and with a couple of 1.5 mm parallel hole collimators, 22 mm and 40 mm length with 0.2 mm septa respectively. All the collimators were individually coupled to a scintillation gamma camera based on LaBr3(Ce) continuous crystal and multi anode PMT Hamamatsu H8500. The high intrinsic spatial resolution of the crystal enhances the response of collimators at short source-to-collimator distance –SCD overcoming problems in alignment with the collimator pattern. Spatial resolution and sensitivity were evaluated by scanning the detector field of view at different SCD using a Co57 point source. The parallel hole prototype showed SR better than pinhole with 28 mm FoV. In term of sensitivity, it showed values greater than pinhole one at FoV larger than 2.4 cm. In comparison with LEHR parallel hole collimators, the prototype carried out better SR values at SCD lower than 20 mm with two times more sensitivity. Moreover, the overall SR improved of 20% with respect to the LEGP one at all SCD, with only 35% loss of sensitivity. The collimator prototype seemed complementary with the use of pinhole one and in addition when coupled to the compact LaBr3(Ce) gamma camera can allow a very attractive trade-off between spatial resolution, sensitivity and detection area for radionuclide molecular imaging applications.

The new PMT generation with very high quantum efficiency is very attractive for their potential to improve energy resolution, in particular for applications involving new scintillation crystals with high light yield. Furthermore recent development of new devices, like silicon photomultipliers (SiPMs), with high gain and quantum efficiency have raised the competition between silicon and standard photomultiplier device in particular for application where high energy resolution may improve the imaging response of the detector. Hamamatsu has recently developed a new prototype PMT R7600-200 with an Ultra BiAlkali (UBA) photocathode (QE=42%). To evaluate the improvement, we compared the energy resolution obtained by R7600-200 PMT with ones from a standard R7600 PMT (QE=22%); the results from both PMTs was obtained with a standard and a tapered divider circuit respectively. We compared also the data from a MA-PMT H8500 and from a PMT R6231, representing a gold standard. A LaBr3:Ce scintillator crystal (½” diam. x ½” thick) was coupled to all PMTs. Preliminary results show an energy resolution improvement with UBA photocathode of about 30% @122keV with respect to R7600, close to what expected from the higher quantum efficiency (40%). On the contrary they agree with ones from R6231 PMT, thought its lower QE. This result is probably due to the different collection efficiency of first dynode stage related to different dynode structure of tubes. Furthermore an energy resolution improvement smaller than expected resulted from H8500 MA-PMT. Thought the same dynode structure, this result is not well understood and it could probably due to the larger size of MAPMT photocathode, involving a better light collection. In any case, the improvement of 30% between UBA e No-UBA PMT is not in agreement with the expected one (20%), considering the intrinsic energy resolution of LaBr3:Ce (4.4%@ 140 keV). This behavior is not well explained at moment and is matter of next investigations.

The availability of LaBr3:Ce crystals from St. Gobain has started various investigations in the field of medical imaging, in particular in PET, SPECT and Compton camera systems. At present LaBr3:Ce crystals are available in a continuous shape covering up to 10×10 cm2 with a thickness of 1 cm, in contrast, serious concerns are arising in pixellated manufacturing. With the aim of verifying the potentials introduced by LaBr3:Ce for SPET imaging, two small γ cameras based on Anger camera principle have been assembled and imaging performances were compared. Two crystals of LaBr3:Ce and NaI(Tl) with the same detection area (5×5 cm2) and thickness of 5 and 1.5 mm, respectively were been integrally assembled with a H8500 Hamamatsu flat panel PMT. Through the thicker crystal, the LaBr3:Ce camera showed superior imaging and detection performances at 140 keV compared with the NaI(Tl) one, with 0.9 mm FWHM intrinsic spatial resolution, 8% FWHM energy resolution and 80% intrinsic detection efficiency.

Scintirad is an interdisciplinary research program that studies novel translational radiopharmaceuticals for cancer diagnosis and therapy. Scintirad employs methods of the Nuclear Medicine applied to small animals and develops new instrumentation for high resolution imaging. The first part of this report describes research programs, results and future plans, while the second part, entitled “who we are”, offers an overview of the role of involved teams and facilities.

The principal limiting factor in the clinical acceptance of scintimammography is certainly its low sensitivity for cancers sized

Over the last three years, there has been a growing interest in the development of a new class of fast scintillators such as LaCl3 :Ce and LaBr3:Ce, or their superior energy resolution is opening an easier way to improve spatial resolution. In this paper we present the results obtained from the first LaBr3:Ce small gamma camera. It is based on continuous 50 times 50 mm2 crystal 5 mm thick integral assembled with a Hamamatsu Flat panel PMT. This detector optical configuration permits the narrowest light distribution and highest light collection to obtain the best spatial and energy resolution values respectively. At the same time 5 mm crystal thickness carries out 80% efficiency at 140 keV photon energy. Measurements of spatial resolution are also compared with the analogous ones obtained from another 50 times 50 mm2 LaBr3:Ce crystal, assembled with a 3 mm glass optical window. Energy resolution values have been furtherly compared with ones obtained from a LaBr3:Ce one inch diameter and thickness optimized for spectrometric measurements. The first LaBr3:Ce gamma camera shows excellent intrinsic spatial resolution values such as 0.9 mm with a best energy resolution value of 6.0% at 140 keV photon energy

188Re is a beta- (Emax = 2.12 MeV) and gamma (155 keV) emitter. Since its chemistry is similar to that of the largely employed tracer, 99mTc, molecules of hyaluronic acid (HA) have been labelled with 188Re to produce a target specific radiopharmaceutical. The radiolabeled compound, i.v. injected in healthy mice, is able to accumulate into the liver after a few minutes. To study the effect of metabolic radiotherapy in mice, we have built a small gamma camera based on a matrix of YAP:Ce crystals, with 0.6x0.6x10 mm**3 pixels, read out by a R2486 Hamamatsu PSPMT. A high-sensitivity 20 mm thick lead parallel-hole collimator, with hole diameter 1.5 mm and septa of 0.18 mm, is placed in front of the YAP matrix. Preliminary results obtained with various phantoms containing a solution of 188Re and with C57 black mice injected with the 188Re-HA solution are presented. To increase the space resolution and to obtain two orthogonal projections simultaneously we are building in parallel two new cameras to be positioned at 90 degrees. They use a CsI(Tl) matrix with 1x1x5 mm**3 pixels read out by H8500 Hamamatsu Flat panel PMT., Comment: 6 pages, 8 figs. To appear in Nucl. Phys. B (PS), proc. of Innovative Particle and Radiation Detectors, Siena, 23-26 May 2004

The introduction of Lanthanum Bromide crystal, characterized by a fast and high light emission, offers the possibility to improve both imaging spatial resolution and energy resolution in SPECT in the 80-300 kev energy range, without compromising detection efficiency. The expected performances may be limited if the crystal is used with a multi-anode PMT with Position Sensitive response due to the wide differences in the segmented anode pad gains, ranging from 2:1 to 10:1, . These characteristics may strongly deteriorate the overall energy resolution and, consequently, impair the detector imaging capability. For this reason, a 256 independent channel electronic read out was developed, based on an FPGA control, to individually read the charge on each anode. The electronics features a very low electronic noise ( < 1%) and a wide dynamic range. The readout electronics was used to build a gamma camera based on a single 100 mm × 100 mm continuous LaBr3:Ce crystal coupled to a 2 × 2 array SBA photocatode (38{%} QE) Hamamatsu H8500. An offline calibration procedure is also shown in order to compensate the anode gain variation and to exploit the LaBr3:Ce capabilities, obtaining on the whole detection area an 8.0-8.5{%} energy resolution at 140 kev. The high energy resolution performances of this gamma camera permitted to discriminate emissions from two different isotope ( Tc99m and Co57) with very close photon energy (140 and 122 kev respectively). This capability can be used to provide the gamma image with references coming from Co 57 point sources (marker) fixed at known positions. These results confirm the LaBr3:Ce crystals as one of the most interesting for all single photon emission applications. © 2013 IOP Publishing Ltd and Sissa Medialab srl.

This paper reports on the tests of a low-noise, multi-channel readout integrated circuit used as a readout electronic front-end for a diamond multi-pixel dosimeter. The system is developed for dose distribution measurement in radiotherapy applications. The first 10-channel prototype chip was designed and fabricated in a 0.18 um CMOS process. Every channel includes a charge integrator with a 10 pF capacitor and a double slope A/D converter. The diamond multi-pixel detector, based on CVD synthetic single crystal diamond Schottky diodes, is made by a 3 × 3 sensor matrix. The overall device has been tested under irradiation with 6 MeV radio therapeutic photon beams at the Policlinico ''Tor Vergata'' (PTV) hospital. Measurements show a 20 fA RMS leakage current from the front-end input stage and a negligible dark current from the diamond detector, a stable temporal response and a good linear behaviour as a function of both dose and dose rate. These characteristics were common to each tested channel. © 2013 IOP Publishing Ltd and Sissa Medialab srl.

The bimodal diagnostic systems like ultrasound/scintigraphic ones have the benefit of providing both morphological and physiological information. In the case in which it intends to develop a compact bimodal probe it is important that, as the readout electronics are doubled, the acquisition system is the most compact possible. In this paper we present the characterization and preliminary measurements on a multi-channel readout ASIC for PSPMTs. The chip is equipped with 32 readout channels, as different works show that single channel readout allows to exploit the performances of a gamma detector, especially for linearity. Each single channel readout is composed by a variable capacitor CSA, a sample&hold and a variable gain amplifier (VGA). The possibility to change the gain of the amplifier allows to compensate for the differences in gain of the anodes of the PSPMT, while the possibility of changing the integrator capacitor allows to adapt the input dynamic of the chip depending on the PMT used (BA or SBA photocatode) and on the scintillation crystal coupled to the PMT itself. The preliminary measurements show that a 200 kHz maximum sampling rate is achievable, with 1 V input dynamic and an overall linearity of the whole channel with respect to the input charge impulse of than 2%. To validate the performances of the ASIC different operative measurement was made in two configurations: with a single chip and two R11265-M16 PMTs, and, parallelizing two chips with a single PMT H8500. The tubes were coupled with scintillation crystals with different response speeds, from CsI to LaBr3.

THE recent improvements in the quantum efficiency of Hamamatsu H8500 position sensitive PMT can be exploited if a multi channel low-noise readout electronics is used. In order to test to its limits the capability of the H8500 and readout electronic system, the PSPMT is coupled with an integral line NaI(Tl) crystal 1.5 mm thick, a pixellated NaI(Tl) 2.0mm pitch, 6mm thick and a pixellated CsI(Tl), 1mm pitch, 1mm thick. The gamma camera with the different crystals is tested with gamma sources in the 30 to 660 keV energy range. The acquisition system used is made by four analog PCBs, each one makes the acquisition of the analog signal and the A/D conversion from 16 anodes at 14 bit resolution, and is connected by USB to a control PC. The aim of the measurements is to show that, as expected from poisson statistic, the spatial resolution and the size of the PSF (sigma of the distribution of light) are inversely proportional to the square root of the photocathode generated photoelectron number. The values measured in the two configurations (continuous integral line and pixelated crystal) are compatible with those expected. Particularly, for the pixellated NaI(Tl) we find a Gaussian light distribution with about 11 mm FWHM and a with a source at 140 keV we can estimate a photo electron yield equal to 600–800 per scintillating event, with an estimated resolution close to 0.35–0.50 mm. The gamma camera is able to correctly identify the light distribution also with 1 mm pixellated CsI(Tl) where the light distribution is virtually contained in a single anode (the anode dimension is 6 mm by 6 mm) and the assignment of the correct position is only estimated based on the very low levels of charge present on the anodes around the one that collected the most of the charge.

In this work, we present a mean square estimation (MSE) based algorithm to calculate the position of a scintillation event within the crystal of a gamma camera dedicated to single photon imaging applications. The performances analysis takes into account pixilated and continuous shape configuration crystals, coupled to an Hamamatsu H8500C multi-anodes PMT (MA-PMT). The readout electronics used for readout has 64-independent channels each reading simultaneously the 64 anodes of the MA-PMT. An array of NaI(Tl) scintillation crystal with 2.0 mm pitch, one of CsI(Tl) with 1.6 mm pitch and one of YAP with 2.0 mm pixel size are taken into account. In addition, a continuous LaBr 3(Ce) crystal coupled to an Hamamatsu H8500C-Mod8 MA-PMT equipped with a super-bialkali photocathode (38% QE at 380 nm) was analyzed. Position linearity and spatial resolution analyzed with collimated (for continuous crystal) and uncollimated (for pixilated crystal) Co57 radioactive source and the scintillation points are calculated both with MSE and with a standard center of gravity (CoG) algorithm. The MSE algorithm improves spatial resolution and expands the useful field of view (UFOV) of the gamma camera that nearly reaches the size of the photocathode area thus showing a great advantage with respect to the CoG algorithm. © 2010 Elsevier B.V. All rights reserved.

The gamma cameras built on a LaBr3 crystal and Hamamatsu H8500 has a 49 mm by 49 mm FOV, equal to the detector active area. In order to increase the active area it is necessary to put more than one detector side to side. This can be done because the H8500 is designed do reduce as much as possible the dead area between two detectors. If we use a 2 by 2 matrix it is possible to use a single 10cm by 10 cm LaBr3 crystal. The readout system has in this case 256 independent channels, with low noise and wide dynamic. The system is managed by an FPGA that reads all the inputs in parallel, up to a maximum rate of 250 KSample/sec, and makes a pre-processing of data. The use of the last generation H8500 PSPMTs, having a SBA photocatode with better quantum efficiency but a lower gain, requires an in deep analysis on the readout electronics induced error, in order to increase the signal to noise ratio. Moreover the individual channel readout allows a better correction of the anodic gains, a particularly relevant problem when more than one PMT is used, and a better study of the light sharing among two PMTs by the use of more sophisticated algorithms with respect to standard the CoG. This approach is mandatory in order to reduce the dead zone between two PMTs.

We present a mean square estimation (MSE) based algorithm for position calculation of a scintillation gamma cam­era dedicated to single photon imaging. The photodetector consist of a 2×2 array of Hamamatsu H8500C-Mod8 segmented-anodes PMT (10×10 cm detection area)coupled to an array of NaI(Tl) scintillation crystals with 1.8 mm pixel size. Phototubes are read out by a 256-independent channels electronics each reading simultaneously all the anodes of the MA-PMT. We analyzed position linearity and spatial resolution where the scintillation points are calculated both with MSE and with a standard center of gravity (CoG) algorithm, and with particular attention to the crystal edge and between tubes. The MSE algorithm improves the pixel identification and the linearity, and expands the useful field of view (UFOV) up to the whole detection area of the gamma cameras. In conclusion, MSE showing a greater advantage with respect to the CoG algorithm.

Monocrystalline diamond, grown with CVD techniques, is a very good base material for clinical dosimetry sensors. Diamond also shows good physical and electronic properties in term of tissue equivalence and very low dark currents. The sensor current readout is made by electrometers, these are expensive and bulky and, due to the need of shielded cables, can hardly be used for matrix sensor readout. In order to overcome these problems an ASIC, directly bonded to the sensor, could be the most suitable electronic readout. The ASIC should be capable of integrating currents smaller than the pA, with a serial interface to minimize interconnection cable volume, providing a compact and portable device. This paper describes the main functional ASIC blocks we designed. The ASIC has nine channels that will be able to operate in the clinical dosimetry current range, and one channel dedicated to dark currents integration. We present simulation results for every functional block and the final chip layout.

In the development of a new gamma camera, we compare the characteristic of two distinct readout electronics, both able to perform single anode reading. The two gamma cameras are based on the H8500 Position Sensitive Photomultiplier (PSPMT) coupled with a planar 5cm × 5cm × 0.4cm BrLa 3 :Ce crystal.

The increasing demand of sophisticated devices for Medical Imaging, with submillimeter spatial resolution and high detection efficiency, motivates an in-depth study of detectors able to fulfill these requirements. In particular for Single Photon Emission Tomography applications, the on-going development of large LaBr3:Ce crystals makes very attractive their use as a system of gamma imaging. Single crystals can overcome the limitation in term of spatial resolution related to pixel size in scintillation arrays, once the problems of limited position linearity and image size are solved. In this work we use GEANT4 simulations in order to model different configurations based on LaBr3:Ce crystals coupled to a Hamamatsu H8500 Multi Anode Photomultiplier. The position linearity, the spatial and energy resolutions obtainable from optimum photodetection conditions are investigated. The values obtained by the Monte Carlo simulations are compared to the experimental results and found to be in good agreement with them upon tuning of some parameters.

Knowledge of the Depth-Of-Interaction (DOI) in detector is crucial for small ring diameter PET scanner but it is also very important for single photon emission imaging, in particular for applications where very high spatial resolution is required and position distortions caused by slant collimators can strongly affect the final response of the 3D reconstructed image. In addition the DOI determination at 140 keV is the most critical due to thinner crystal thickness and the lower number of scintillation light photons. Continuous scintillation crystals are in principle the most suitable for continuous DOI determination based on the measurements of light width of cones generated at each gamma ray interaction. In this work we propose an analysis based on a Monte Carlo GEANT4 studies and on experimental measurements at 140 keV performed on a small LaBr3:Ce continuous crystal coupled to latest multi-anode PMT Hamamatsu H8500-MOD8 series equipped with super Bialkali photocathode (SBA). The basic idea of this work is that the high light output of LaBr 3 :Ce joint with SBA photodetector can reduces statistical uncertainties related to the light distribution spread determination. Furthermore it can be crucial with a more precise measurement of scintillation light distribution from the 8×8 anode array of MAPMT. Measurements and simulation confirm that light distribution spread (SD) is related to DOI, with a DOI resolution of about 2.0-2.2 mm (Monte Carlo) and 2.8-3.0 mm experimental at 140 keV. In addition, we shown how the selection in SD window provide a 10% of spatial resolution improvement, down to (0.85±0.03) mm, for a LaBr 3 (Ce) continuous crystal coupled to the new photodetector H8500-MOD8. This method can open the possibility to build a high-sensitivity detector with DOI capability useful for gamma-ray imaging application.

The use of position sensitive multianode PMTs requests the reading of a large number of channels at the same time, in order to correct the anode gain variations that are found in these devices.

The dosimeters for radiotherapy must comply to strict requirements in terms of sensitivity, toxicity, tissue equivalence and radiation hardness. At present time both silicon and diamond dosimeters are used as solid state devices and in recent years, monocrystalline diamond sensors have been grown with CVD techniques. Due to the low current signals, the sensor readout is made by electrometers connected to the device with multi wire shielded cables. This measurement setup may be a serious limitation for practical application of these sensors, and makes impossible the use of matrix sensors. We present some functional block design for an ASIC that could replace the electrometer and the cabling for the measurements. The system will be realized by an hybrid assembly with the detector, or the detector matrix, very closely placed and wire bonded to the readout ASIC. The device is designed in 180 nm UMC technology with dual power supply, 3.3 V for the analog front end, in order to extend the signal dynamic, and 1.8 V for the control logic.

Recently scintillators with very high light yield and photodetectors with high quantum efficiency have been opening a new way to realize gamma cameras with superior performances based on continuous crystals. Pixilated imagers have a spatial resolution limited by pixel size, in contrast with continuous scintillation crystals, where spatial resolution is a statistical function depending on light distribution spread and on generated photoelectrons from scintillation light flash. Continuous LaBr 3 :Ce crystal, with a light yield almost two times higher than NaI:Tl ones and a lower intrinsic energy resolution, could be the best candidate to carry out a gamma imaging with sub-millimeter spatial resolution and very good energy resolution. Unfortunately standard Anger algorithm produces an intrinsic position non-linearity affecting spatial resolution for small size continuous crystal. In this work we propose a new method to calculate the position mean value by squaring the 2D collected charge distribution on a multi-anodes photomultiplier tube (MA-PMT). In this study we take into account four different detector configurations: three sample of LaBr 3 :Ce scintillation crystals, 49mm×49mm area, a couple of 4.0 with different surface treatment and a single 10 mm thick, with 3 mm glass window. Moreover a forth one with 5.0mm thickness which was integral assembled with an Hamamatsu H8500. We applied the new position algorithm to simulated data, obtained by Geant4 code and afterwards to the experimental data obtained scanning the different detectors with 0.4 mm O collimated Tc99m point source, at 1.5 mm step. The results obtained with the new algorithm show an improvement in position linearity and in spatial resolution of about a factor two. The best values in terms of spatial resolution were 0.9 mm, 1.1 mm and 1.8 mm for integral assembled, 4.0 mm thick and 10 mm thick LaBr 3 :Ce crystal respectively. These results demonstrate the potential of LaBr crystal for molecular imaging application and more in general for gamma ray imaging

Artificial neural networks can be successfully used for short-term load forecasting and it is well known that better forecasting performances can be obtained taking into account the weather influence on electric load. An extensive analysis has been conducted for selecting the monitoring sites most representative of the Italian general weather conditions. The selection activity has been based on the computation of correlation functions. The analysis of the results thus obtained has permitted the identification of correlated and noncorrelated sites for each meteorological variable. The variables identified have been used for integrating the training set of an available ANN in order to test its forecasting performance. The paper reports on research activity aimed at carrying out an adequate model permitting correct representation of weather influence on Italian electric hourly load.

In this paper are presented the preliminary measurements of electrical losses in oxide compounds that are usually present on the surface of bronze artifacts. These measurement are currently not found in literature and could allow a non-destructive analysis of the bronze surface oxide layer composition. An automatic measurement method, based on a capacitive sensor and a multi-frequency excitation waveshape, is studied.

The paper illustrates two different Artificial Neural Networks (ANN) architectures for electric Short-Term Load Forecasting (STLF). Two multi-layer perceptron ANN using the back-propagation learning algorithm have been implemented which provide different, although complementary, forecasting approaches (static and dynamic). In order to test the potentialities of the architectures implemented, the ANN have been applied to the Short-Term Forecasting of Italian hourly electric load. The importance of this load (peak demands up to about 38 000 MW) requires tools for STLF which must be as more accurate and precise as possible. This fact has imposed the adoprequires tools for STLF which must be as more accurate and precise as possible. This fact has imposed the adoption of some algorithmic enhancements to the basic back-propagation algorithm formulation. Since an adequate formulation of the influence exerted on hourly electric load by the main meteorological and climatic factors is not known at present, the data set used for ANN training phase has concerned only historical series of electric hourly demand. The paper illustrates the two ANN architectures as well as the computational platforms used for implementation. Finally, some results obtained from the application of the two ANN to the short-term forecasting of Italian electric load relevant to three different weeks of the year 1993 are comparatively reported.

In this paper, the design and characterization of a 7-bit CMOS stochastic-flash analog-to-digital converter is illustrated by means of simulations including level-3 CMOS models and estimated dither-based spectra. The conversion scheme and its main properties are briefly recalled, and a possible design of the voltage reference generator proposed. It is shown that mismatches among the resistors in the ladder employed to generate these voltages are largely compensated by the presented architecture when small-scale dithering is employed.

LaBr3:Ce has been showing very promising characteristics as gamma ray imager and spectrometer. In particular its excellent energy resolution values (6% at 140 keV and not, vert, similar3% FWHM at 662 keV), obtained when coupled to a PMT, make it the major competitor of semiconductor detectors working at room temperature. In order to improve its imaging performances, the LaBr3:Ce can easily work as continuous detector allowing sub-millimeter spatial resolution values at 140 keV photon energy when coupled to a Position Sensitive PMT. Further interesting characteristics like a short scintillation decay time (16 ns), a very high light yield (63 000 photons/MeV) and a low afterglow are attracting the scientific community for the potential improvement of a wide range of applications in medicine like PET, SPECT and CT instrumentation. In this paper, we present some preliminary imaging results obtained by coupling H8500 Hamamatsu Flat Panel PMT to two LaBr3:Ce crystals with 50×50 mm2 area, 5 and 10 mm thickness respectively. With the aim to propose a single detector able to combine functional information, for example from Single Photon Emission technique, with the morphological ones from X-ray imaging the spatial resolution results obtained in the energy range between 30 and 302 keV are analyzed and discussed. We obtained very interesting spatial resolution results for gamma ray energy value greater than 60 keV (better than 1 mm, intrinsic value), while in the energy range proper to X-ray applications, like RX-Mammography (about 30 keV), the spatial resolution values resulted about 2 mm.