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Due to the need for harmonization of passive dosimetry and the requirements of the international standards in the area of environmental monitoring in radiation protection, multiple types of various passive dosimetry systems based on different ionizing radiation detection mechanisms were subjected to extensive performance testing. In the scope of the EMPIR project 16ENV04 Preparedness, the performance of 12 passive dosimetry systems was examined in radiation fields of different photon energies, angles of incidence and ambient dose equivalent rates in order to estimate their performance in the almost omni-directionally and energetically broad radiation field of the natural environment. The use of different detectors, holders, calibrations, measurement procedures and uncertainties, leads to differences in the measured data. Prior investigations and harmonization of passive dosimetry systems are necessary to achieve reliable and comparable dose measurements in Europe.

The results obtained in a measurement campaign concerning internal contamination by the gamma-emitting radionuclides of a large number of individuals are presented in this work. The aim is to assess the effectiveness of the spectrometric method in an emergency response following a nuclear power plant accident or a spread of radionuclides in the atmosphere due to an act of terrorism. An HPGe portable spectrometer, deployed in a collective protection apparatus, was used for both whole-body and thyroid measurements. An adult bottle mannequin absorption (BOMAB) and thyroid phantoms were used to evaluate the detector performance. The BOMAB phantom was provided by the Italian Institute of Ionizing Radiation Metrology (INMRI) for the ENEA intercomparison exercise. Thyroid phantoms were provided by the Belgian Nuclear Research Centre for the 'Child and Adult Thyroid Monitoring After Reactor Accident' European intercomparison exercise. The instrument performance was further evaluated by collecting spectral data from healthy volunteers, using acquisition times of 180 s and 100 s, respectively, for the whole-body and thyroid measurements. The detector showed good accuracy in quantifying radionuclide activities in the adult BOMAB and in the thyroids of persons of all ages. The proposed method allows us to detect in vivo activity leading to a committed effective dose E(50) and committed thyroid equivalent doses H T greater than 2 mSv due to all gamma-emitting fission products, if the scan is performed within five days after intake. Assuming, for instance, an acute inhalation of 137Cs and 131I, the obtained detection limit values for adults lead to a E(50) value equal to 0.08 mSv and an H T value of 0.27 mSv. The E(50) and H T values show that the proposed method can be successfully used when the dose assessment must be rapidly performed for a large number of individuals in the eventuality of the scenarios previously mentioned.

In the aftermath of a nuclear or radiological accident, an extended mapping of reliable dose rate values is of key importance for any governmental decision and countermeasures. Presently, numerous dosimetry network stations, operated by the national governments of the member states in Europe, provide such dose rate data on an hourly basis. Nevertheless, there are large areas in Europe that are not covered at all by these early warning networks and other areas that show only a low density of governmental network stations. Hence, there may be a significant lack of information in case of a nuclear or radiological emergency. As a consequence of the Fukushima Daiichi nuclear power plant accidents in 2011, a number of non-governmental radiation monitoring networks (NRMN) appeared on the internet, providing dose rate data based on stationary as well as on mobile measurements of ionizing radiation by laypersons. Especially the mobile detectors are able to cover large areas in short time. Therefore, it is of considerable importance to investigate the feasibility of using dose rate data from non-governmental networks as a complementary input to the European Radiological Data Exchange Platform (EURDEP). Within the European Metrology Program for Innovation and Research (EMPIR), the project 16ENV04 “Preparedness” has studied the metrological relevance of such non-governmental dose rate data (also called crowd-sourced radiological monitoring) in the most comprehensive way so far. Sixteen different dose rate detector systems (in general 4 of each type, plus 2 types with 2 detectors, i.e. 68 detectors in total) used in NRMN have been investigated for the reliability of their data and the corresponding networks, and their data provision to the public were analyzed. The most relevant performance parameters of dosimetry systems (detector's inherent background, energy dependence and linearity of the response as well as the response to secondary cosmic radiation, the sensitivity to small increases of the dose rate and finally the stability of the detector's indication at various climatic conditions - temperature and humidity) have been investigated for fourteen representative types of non-governmental dose rate measuring instruments. Results of this comprehensive performance study of the simple, light-weighted and cheap dose rate meters used in NRMN, and conclusions on the feasibility of using their data for governmental monitoring in case of a nuclear or radiological emergency are presented. © 2021 The Authors

One of the objectives of the EMPIR project 16ENV04 “Preparedness” is the harmonization of methodologies for the measurement of doses with passive dosimetry systems for environmental radiation monitoring in the aftermath of a nuclear or radiological event. In such cases, measurements are often performed at low radiation dose rates, close to the detection limit of the passive systems. The parameters which may affect the dosimetric results of a passive dosimetry system are analyzed and four laboratories quantitatively evaluate the uncertainties of their passive dosimetry systems. Typical uncertainties of five dosimetric systems in four European countries are compared and the main sources of uncertainty are analyzed using the results of a questionnaire compiled for this specific purpose. To compute the characteristic limits of a passive dosimetry system according to standard ISO 11929, the study of the uncertainty of the system is the first step. In this work the uncertainty budget as well as the characteristic limits (decision thresholds and detection limits) are evaluated and the limitations and strengths of a complete analysis of all parameters are presented.

In order to properly respond to an emergency caused by an accident in a nuclear power plant with a spread of radionuclides in the atmosphere, we propose a field procedure to perform a large-scale individual thyroid monitoring of internal contamination due to inhalation of 131I, by means of non-spectrometric equipment, in particular dose rate meters. Specific attention is paid to the individual monitoring of children, because of the very high radiosensitivity of the child's thyroid to the carcinogenic effects of ionising radiation. The device performance was evaluated by measuring mock iodine sources provided in the Child and Adult Thyroid Monitoring After Reactor Accident (CAThyMARA) intercomparison and, just for a scintillator dose rate meter, by means of 60 s acquisitions of healthy volunteers' thyroids. All the devices showed a remarkable accuracy in quantification of equivalent 131I activity in the thyroids of persons of all ages. The selected scintillator dose rate meter showed detection limit values resulting in a maximum committed equivalent dose to thyroid HT, assuming an acute 131I inhalation occurred five days before the measurement, equal to 10 mSv (related to five-year-old children). Considering the level of HT values associated with the calculated detection limit activities, the proposed procedure has a significant sensitivity to be used for fast internally thyroid monitoring in nuclear or radiological emergencies, allowing daily monitoring a large amount of individuals.

In order to properly respond to an emergency of nuclear and radiological terrorism, we realized a mobile complex system (MCS) for conducting on field a large-scale individual monitoring of internal contamination by gamma emitters. The proposed MCS consists of a collective protection apparatus and a HPGe portable spectrometer for whole-body and thyroid measurements. The MCS performance was evaluated and showed, assuming, for instance, an acute inhalation of 137Cs and 131I occurred 5 days before measurement, detection limit values resulting in a committed effective dose equal to 0.07 mSv, and a maximum committed equivalent dose to thyroid equal to 1.3 mSv, respectively. Considering the annual limit of effective dose for public exposure and the lowest reference level to plan stable iodine prophylaxis, the proposed MCS has a significant sensitivity to be used for fast internal monitoring in nuclear and radiological emergencies from malicious acts. This MCS allows to operate in contaminated environment and to monitor daily a large amount of individuals.

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.

Following the Fukushima power plants accident on the 11th March 2011, the radioactivity monitoring programme at the Italian ENEA research centres was activated in order to detect the possible new input of radionuclides through atmospheric transport and precipitation. Measurements of (131)I and (134,137)Cs were carried out on atmospheric particulate, atmospheric deposition, seawater and mussels and sheep milk. In the daily samples of air particulate, (131)I was detectable between March 28 and April 12, with extremely low concentrations (1 mBq m(-3); the detection limit for (131)I was ~0.2 mBq m(-3)) while Cs isotopes were always below the detection limit (0.2 mBq m(-3)). The two main episodes of (131)I atmospheric deposition were registered in La Spezia research centre, around March 28 and April 15, reaching values of 17.8 ± 1.1 and 8.0 ± 2.5 Bq m(-2) respectively; maximum values of (134)Cs and (137)Cs were 0.11 ± 0.03 and 0.17 ± 0.02 Bq m(-2), respectively, detected in Brasimone research centre in April (reference date April 15). Mussels and seawater were collected in the Gulf of La Spezia: only mussels after the main (131)I deposition, on March 28, contained a measurable, although very small, amount of (131)I (0.18 ± 0.05 Bq kg(-1), detection limit (131)I = 0.03 Bq kg(-1) wet weight - soft parts). The (131)I was also detected in sheep milk in Rome (Casaccia research centre) until May 5, showing a maximum concentration of 4.9 ± 0.4 Bq L(-1). As for other European Countries for which data are available, activity levels remain of no concern for public health.

Irradiation resistance of as-studied scintillating glass samples were tested under the 60Co γ-ray radiation at doses between 60 and 700 Gy. Photoluminescence properties of glasses with and without cerium ions were investigated to show the effect of cerium (III) on the luminescence of ZnO. Ultraviolet and visible optical transmittance spectra were compared before and after irradiation treatment. The so-called radiation-induced absorption coefficient (RIAC) was introduced to compare more effectively the radiation damage on glass samples. The much reduced transmittance change and decreased RIAC value in UV–Vis region indicate that the density of electron centers and hole centers caused by radiation decreased, which helps to confirm that the reduction and oxidation reaction of cerium ions took place in radiation process. From RIAC curves, it can be seen that TiO2 enhances the irradiation resistance of sample in UV region. However, high TiO2 content has negative effect on visible transmittance of glasses after the higher dose irradiation (700 Gy).

The Hamamatsu H8500 Flat Panel PMT is the latest technological advancement in gamma ray imaging. Its compact size makes it attractive for medical imaging applications. To study and compare image performance a Flat Panel PMT, representing the present production, was coupled to CsI(Tl) and Nal(Tl) scintillation arrays with 3 mm and 1.8 mm pixel size respectively and connected to a multi-anode electronic readout. Furthermore, a pulsed blue LED coupled to an optical liber was utilized to scan the tube with different light distributions. This study investigated how PMT anode gain uniformity response, scintillation light distribution and intensity influence the spatial resolution, the position linearity and the image noise. Each crystal in the scintillation array produces a different charge distribution, which depends on the match between the anode size and the scintillation array lattice. The Nal(Tl) array demonstrated to fit both PMT characteristics and dynamic range of electronic read out, due to the charge distribution adequate to the anode size. For CsI(Tl) crystal, the pulse height calibration resulted more critical, due to the narrow light distribution. In conclusion, the use of Flat Panel tube with selected anode gain uniformity could represent the cheapest and easiest solution to obtain the best image quality, in particular for scintillator array with smaller pixel size.

This paper aims to describe a sub-miniature scintillation detector suitable for functional bronchial scanning and solitary pulmonary nodules detection. The device is made by a probe having diameter adequate for insertion in a catheter and external electronics for signal's analysis. The final scanner will be composed of a train of individual detectors, each one made by a scintillation crystal and a Si-avalanche photodiode operating in single-photon modality. The setup shows high-efficiency photon detection and high quantum-efficiency readout giving adequate energy resolution for efficient rejection of scattered events. The crystal can be adequately shielded to reduce the background from healthy tissues. Assuming the use of a radiopharmaceutical labeled with 99mTc, Monte Carlo simulations concerning a simple pulmonary model have been performed at 57Co lines and compared to experimental results. Furthermore, useful simulated data have been obtained at 140 keV concerning the strategy for background reduction to improve nodule localization.

L’Istituto di Radioprotezione ENEA (IRP), che assicura la sorveglianza fisica di radioprotezione all’interno dei centri di ricerca ENEA, nell’ambito delle proprie attività ha istituito un gruppo di lavoro tra gli Esperti Qualificati dell’Agenzia che si occupasse della stesura di una serie di procedure a supporto delle attività istituzionali. All’interno di questo progetto è stato elaborato un documento che illustra la procedura operativa applicata in ambito IRP per la misura indiretta della contaminazione superficiale rimovibile ,  e , senza impiego di contatori a scintillazione liquida. Lo scopo delle misure di contaminazione superficiale con finalità di sorveglianza fisica è quello di controllare l’esposizione alle radiazioni stimando la concentrazione, il rilascio e la risospensione in aria di materiale radioattivo per valutare il conseguente impatto sui lavoratori e sulla popolazione attraverso esposizione esterna e/o interna. La contaminazione superficiale è generalmente costituita da una componente fissa e una rimovibile. La prima è intimamente integrata con i materiali della superficie mentre la seconda può essere rimossa con semplici operazioni di pulizia e strofinio e può molto facilmente essere rilasciata dal materiale. L’applicabilità e l’affidabilità delle misure dirette o delle valutazioni indirette della contaminazione superficiale dipendono dall’entità di queste due componenti, tanto che talvolta i metodi indiretti che si avvalgono del prelievo di un campione per la successiva misura sono indicati come procedura di elezione nella determinazione della contaminazione superficiale. La procedura sviluppata e qui descritta fornisce le indicazioni necessarie per valutare i livelli di contaminazione superficiale rimovibile tramite campagne di misura condotte con la tecnica conosciuta con il termine “smear test” o di strofinio, consigliando anche le metodiche più accreditate sulla base di diverse condizioni e in presenza di diverse situazioni operative. Nella medesima procedura si propone anche una strategia di controllo che comprende diversi livelli o vincoli derivati in corrispondenza dei quali attuare azioni adeguate ad affrontare le situazioni che possono essere previste in funzione dei risultati del monitoraggio effettuato. In via preliminare sono quindi definiti e discussi livelli derivati di registrazione, indagine e intervento, al di sopra dei quali si opera rispettivamente nei modi seguenti: a) si registra il livello di contaminazione rilevato nello specifico punto, b) si avvia un’indagine per stabilire le motivazioni che hanno portato al superamento dello specifico livello, c) si interviene con una decontaminazione dell’area interessata ed eventualmente con l’interdizione all’accesso in quell’area per un determinato periodo di tempo.

This work is aimed to assess the feasibility of a gamma-ray scintillation detector for radionuclide imaging characterized by good energy resolution and point-of-interaction measurement at room temperature. To obtain such performances the single-event scintillation light must be read from more than one crystal face. We have preliminarily analyzed the energy response using CsI:Tl crystals and Si-APD. Results concerning energy response are presented in terms of linearity and resolution. The single-APD configuration, chosen as a reference, has shown very good energy linearity in the range 80–662 keV and a 7.6% FWHM energy resolution at 662 keV. Similar linearity results have been obtained for the 5-APD case, while energy resolution worsens down to 13.2% FWHM. These results could be further improved using APD with reduced peripheral dead zones.

The very low sensitivity of scintimammography for tumours under 1 cm in diameter, with current nuclear medicine cameras, is the major limitation in recommending this test modality for screening purposes. To improve this diagnostic technique,a new concept of scintillation gamma camera, which fits the best requirements for functional breast imaging has been developed under “Integrated Mammographic Imaging” (IMI) project. This camera consists of a large detection head (6″×7″),very compact sized and with light weight to be easily positioned in the same X-ray geometry. The detection head consists of matrix of 42 photodetector Hamamatsu 1 in 2 square H8520-C12 PSPMTs, which are closely packed and coupled to a NaI(Tl) scintillating array, with individual crystal pixel 2×2×6 mm 3 size. Large FoV camera shows a very good pixel identification in the detection dead zones between tubes allowing an accurate LUT correction of the final image reconstruction. Electronic read-out was especially designed to optimize the intrinsic spatial resolution and camera compactness. With respect to Anger camera, the overall spatial resolution is improved up to 40% while the overall energy resolution values is ∼16% at 140 keV. Large FoV dedicated camera was characterized and tested by phantom studies; and clinical trials are currently performed. For all patients, compression views have been acquiring for both breasts in craniocaudal projections, and are compared with standard gamma camera images.

High resolution radionuclide imaging requires phantoms with precise geometries and known activities using either Anger cameras equipped with pinhole collimators or dedicated small animal devices. Porous silicon samples, having areas of different shape and size, can be made and loaded with a radioactive material, obtaining: (a) precise radio-emitting figures corresponding to the porous areas geometry, (b) a radioactivity of each figure depending on the pore's specifications, and (c) the same emission energy to be used in true exams. To this aim a sample with porous circular areas has been made and loaded with a 99mTcO4- solution. Imaging has been obtained using both general purpose and pinhole collimators. This first sample shows some defects that are analyzed and discussed.

To foresee the response of a discrete scintillation imager, operating in single-photon modality, a computer simulation code has been developed and tested. The simulator, whose acronym is DISIS, may be used for designing and/or evaluating devices based on scintillation arrays coupled to a position sensitive light sensors by light guides. The simulator can be classified as a deterministic code because it is based on: (i) an analytical model describing the scintillation light distribution for charge integrals calculation, (ii) an algorithm using charge values for event centroiding and (iii) a Gaussian model for spreading the events on the image according to the inherent imager resolution. Particularly, DISIS allows one to study the influence of each setup parameter on the device spatial response. The imager optimization can be achieved by improving the pixel identification. To this aim the best trade-off has to be found between: (a) the light distribution at photocathode, (b) the light sampling capability over the photocathode area and (c) the centroiding algorithm

This work presents the results obtained with a new generation portable gamma camera, assembled with an innovative technique based on CsI(Tl) scintillation crystals inserted into the square holes of a tungsten collimator. Characterization measurements have been performed on three detectors with different crystal size, in order to obtain 7×7, 8×8 and 9×9 arrays over the fixed area of 25.7×25.7 mm 2 , having the same overall dimensions of a Position Sensitive Photomultiplier Tube. Detector sensitivity, energy resolution and spatial resolution have been measured , and the acquired image quality has been evaluated with particular attention to pixel identification capability.

The development of a scintigraphic imager is a time-consuming, high-cost interdisciplinary task. Aim of this work is to illustrate the role of Monte Carlo Nuclear Particle (MCNP) transport code in the development of an intra-operative Imaging Probe (IP). A MCNP transport model was used to test some improvement hypotheses regarding collimation and scintillating crystal. On the basis of the simulation outcome, an improved imager prototype was built and preliminary tested. Experimental results were compared with simulation predictions showing a good agreement. These results encourage us to continue the development of a more complex model to be used as "ideal observer" for the imaging probe performance evaluations. © 2005 Elsevier B.V. All rights reserved.

Over the last ten years the strong technological advances in position sensitive detectors have encouraged the scientific community to develop dedicated imagers for new diagnostic techniques in the field of isotope functional imaging. The main feature of the new detectors is the compactness that allows suitable detection geometry fitting the body anatomy. Position sensitive photomultiplier tubes (PSPMTs) have been showing very good features with continuous improvement. In 1997 a novel gamma camera was proposed based on a closely packed array of second generation 1 in PSPMTs. The main advantage is the potentially unlimited detection area but with the disadvantage of a relatively large non-active area (30%). The Hamamatsu H8500 Flat Panel PMT represents the last generation of PSPMT. Its extreme compactness allows array assembly with an improved effective area up to 97%. This paper, evaluates the potential improvement of imaging performances of a gamma camera based on the new PSPMT, compared with the two previous generation PSPMTs. To this aim the factors affecting the gamma camera final response, like PSPMT gain anode variation and position resolution, are analyzed and related to the uniformity counting response, energy resolution, position linearity, detection efficiency and intrinsic spatial resolution. The results show that uniformity of pulse height response seems to be the main parameter that provides the best imaging performances. Furthermore an extreme identification of pixels seems to be not effective to a full correction of image uniformity counting and gain response. However, considering the present technological limits, Flat Panel PSPMTs could be the best trade off between gamma camera imaging performances, compactness and large detection area.

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

AIM To evaluate the soft tissue response to immediately placed implants using the platform switching concept. MATERIAL AND METHODS In 22 patients, 22 implants of 5.5 mm platform diameter were placed immediately into fresh extraction sockets in maxillae without compromised bone tissue. Eventual post-extraction bone defects were filled using bovine bone matrix mixed with collagen. Immediately after insertion, implants were randomly divided: 11 implants were connected with a 3.8 mm diameter abutment (test group) and 11 with a 5.5 mm diameter abutment (control group). A provisional crown was adapted and adjusted for non-functional immediate positioning. Two months later, definitive prosthetic rehabilitation was performed. Periodontal parameter, buccal peri-implant mucosal changes (REC), mesial and distal papilla height (PH) and vertical height of jumping distance (VHG) were measured at the time of implant placement, of definitive prosthesis insertion and every 6 months thereafter. RESULTS The mean follow-up was 25 months. All implants were clinically osseointegrated. The test group showed a +0.18 mm REC gain. PH gain was +0.045 mm on average. The mean values were statistically significant (P< or =0.005) compared with the control group (PH=-0.88 mm; REC=-0.45 mm). No difference between the two groups in periodontal parameters was found. The mean value of bone filling was 7.51 mm in the test group (97.4% of VHG) and 8.57 mm in the control group (95.2% of VHG). No statistically significant difference was found between the two groups. CONCLUSIONS This study suggests that, in a limited time period of 2 years, immediately placed implants with subsequent platform switching can provide peri-implant tissue stability.

The feasibility of radioisotopic planar sources made by absorption of an active solution in Porous Silicon (PS) matrices has been studied. To this aim two PS samples, characterized by different pore dimension and shape, have been made and tested. The Tc radiotracer, commonly used in nuclear medicine departments, has been loaded into the pores by immersion, and the radioactivity distribution over the porous areas has been measured by an Imaging Probe (IP). Using a solution with the low specific activity of 5.8 MBq/cc, counting rates of 96*3 and 36*2 counts/s per pixel (area 3.5x3.5 mm') have been measured, showing good emission homogeneity for both PS samples. A mean activity ratio of 2.6*0.4 has been found between the two samples. Further studies are in progress to optimize matrices treatment and loading techniques and to design porous phantoms having appropriate surface areas, shapes and absorbance. 99m

This work is aimed to study the feasibility of a low energy gamma-ray detector for nuclear medicine to be inserted into a body cavity, duct, or vessel. The small dimension detector concept is based on a CsI:Tl scintillation crystal coupled to a Si Avalanche Photodiode (APD) mounted in a catheter. Due to the availability of Tc in nuclear medicine departments, 140 keV photons have been considered for detector design. At this energy the response concerns a more extended volume nearby the cathector than in the case of beta emitting radiotracers. Monte Carlo simulations have been performed and results have then been compared to experimental ones. The latter have been obtained using a Co radioisotopic source and a laboratory setup including a detector having dimensions not optimized coupled to a low-noise conventional electronics. Count rates and sensitivities have been measured approaching a point source to the detector along some paths and considering different background irradiation levels.

In this work, we report and compare the results of γ-ray spectroscopy measurements performed using a LaBr3:Ce crystal coupled to a photomultiplier tube with modified base and to a Si-avalanche photodiode readout by standard electronics. Energy resolution values have been obtained in the range from 59.5 keV (241Am) to 1332 keV (60Co). Good linearity in energy response has been found. Energy resolution values obtained with avalanche photodiode readout are underestimated due to the small active area of the presently available photosensor with respect to crystal dimension.

In principle, a scintillation imager made by a crystal array and a position-sensitive photomultiplier shows spatial non linearities at borders due to the undersampling of scintillation light distributions. To improve the response of such detectors a method has been carried out based on the comparison between experimental and simulated images. A computer simulation code has been developed and used to foresee the imager response. The code computes the tapered charge-weighting factors giving the optimized event centroiding in terms of crystal-pixel identification. The comparison between measured centroids and crystal axes produces the effective correction table for image linearization. Experimental results concerning a 8x8 crystal array coupled to a position sensitive photomultiplier tube (1 inch square) are presented and discussed.

The feasibility of a subminiature scintillation detector to be inserted in a catheter for lesion localization in nuclear medicine SPECT has been studied. Measurements on a simple laboratory setup have been performed and compared with Monte Carlo results. Further simulations, at 30keV and 140keV, concerning a configuration reproducing severe clinical conditions have shown poor lesion detectability. Several factors affecting the response have to be investigated to improve the capability of lesion localization characterizing such detector.

Hamamatsu H8500 Flat Panel PMT represents the last technological advancement in gamma ray imaging. Compact size makes it attractive for medical imaging application. To study and compare image performance two Flat Panel PMTs were coupled to CsI(Tl) and NaI(Tl) scintillation arrays with 3 mm and 1.8 mm pixel size respectively and they were connected to multi-anode electronic readout (64 channel). Furthermore a pulsed blue LED coupled to an optical fiber was utilized to scan the tube with different light distribution spreading. The study took into account how PMT anode gain uniformity response, light distribution and intensity, influence spatial resolution, position linearity and image noise. Gain calibration was firstly studied because of PMT gain anode non uniformity response, which range between 27:100 and between 45:100 respectively. Furthermore each crystal pixel produces different charge distribution and this depends on the matching between anode and scintillation array lattice. The amount of anode charge can change more than a factor five for narrow light distributions. Tube gain setting results critical, in fact because of energy resolution of each anode spectra, only a factor five pulse height variation can be adequately converted by ADC. In addition there is a further gain anode variation due to PMT non uniformity response of a factor 3. This mentioned two elements, do not allow to convert all pulses in the useful pulse height ADC range. As a consequence image position distortion and background are produced. Flat Panel shows good image performance. However, because of the big anode size and PMT gain non uniformity response, the gain setting can be critical to obtain the best image performance for scintillation light distribution comparable with anode size.

Several INFN Sections and Departments of Physics of Italian Universities have spent many man-years in the attempt to adapt detector and read-out technologies, originally developed in the field of High Energy Physics, to the domain of biomedical apparatuses. The research covered such areas as the exploitation of crystals for the production of monochromatic X-ray beams, the development of devices for efficient X-ray detection, the design of advanced VLSI electronics, the improvement of Position Sensitive Photomultiplier Tubes and crystals for Nuclear Medicine gamma-cameras. These studies have been integrated in the Integrated Mammographic Imaging (IMI) project, funded by the Italian Government through the law 46/82 (art.10) and is carried on by five high-technology industries in Italy, namely LABEN, CAEN, AMS, GILARDONI and POL.HI.TECH. We report on the status of this technological transfer project.

The specific aim of the IMI project is the development of a new concept gamma camera specifically designed for the functional breast imaging. Such diagnostic technique is performed administering to the patient radiopharmaceuticals. It is able to distinguish malignant from benign tumors. The gamma camera prototype developed in the IMI project is very compact and with light weight to be easily positioned in the same X-ray geometry. The final detection head consists of a photodetector based on 42 Hamamatsu 1 in. square PSPMTs closely packed and coupled to a NaI(Tl) scintillating array with individual crystal pixel size of 1.8 mm. Photodetector and the electronic read-out were especially designed to optimize the spatial resolution and the minimum lesion contrast sensitivity for tumors as small as 5 mm size.

In recent years there has been a growing interest in developing compact gamma cameras to improve gamma ray imaging for application in nuclear medicine as well as in astrophysics, radiation physics and high energy physics. The gamma cameras based on position sensitive photomultipliers could be the best chance to obtain a realistic and low cost compact gamma camera. Since 1985 the development of position sensitive photo multiplier tubes (PSPMT) has shown the highest rate in technological advancement achieving very compact size (25 × 25 × 20 mm3) by a novel charge multiplication system. The PSPMT shows the same advantages of a standard gamma camera with the additional possibility to utilize scintillation arrays with pixel dimension less than 1 mm, thus achieving sub-millimeter spatial resolution values. The last technological advance is a PSPMT with Flat Panel structure, named H8500. Its dimension is 50 × 50 mm2 with a narrow peripheral dead zone to place closely different modules achieving large detection areas. In this paper the technological development of different PSPMT generations is reviewed and some measurements of the first Flat Panel PMT prototype are presented and compared with ones from previous generation. Flat Panel PMT could be the best trade-off between compactness, large detection areas, effective area (packing density) and imaging performance.

Over the last ten years there was being a strong advancement in photodetection. Different application fields are involved in their use in particular high energy physics, astrophysics and nuclear medicine. They usually work by coupling a scintillation crystal and more recent scintillation arrays with pixel size as small as 0.5 mm. PSPMT represents today the most ready technology for photodetection with large detection areas and very high spatial resolution. Flat panel PMT represents the last technological advancement. Its dimension is 50x50 mm 2 with a narrow peripheral dead zone (0.5 mm final goal). Its compactness allow to assemble different modules closely packed, achieving large detection areas with an effective active area of 97%. In this paper we analyze the imaging performances of PSPMT by coupling two scintillation arrays and by light spot scanning of photocathode to evaluate the linearity position response, spatial resolution and uniformity gain response as a function of light distribution spread and the number of photoelectrons generated on photocathode. The results point out a very narrow PMT intrinsic charge spread and low cross-talk between anodes. Energy resolution and spatial resolution show a good linearity with DRF variation. An unexpected intra-anode gain variation is carried out. In this paper we present the results obtained with this PSPMT regarding imaging performances principally addressed to nuclear medicine application.

A computer simulation code has been developed in order to foresee the response of discrete scintillation imaging devices. Discrete Scintillation Imager Simulator (DISIS) has been designed for imagers based on a scintillation array coupled to a position sensitive light sensor (like position sensitive photomultiplier tube or avalanche photodiode array) by a planar light guide. The simulator is a deterministic code that uses: (i) a model describing the single photon light distribution emerging from a crystal pixel for charge integrals evaluation; (ii) the assigned algorithm for centroid calculation and; (iii) the Gaussian spread for localizing, crystal by crystal, the events on the image. In particular DISIS allows us to study the spatial response over the imager field of view changing parameters individually. The imager optimization can be obtained searching an acceptable pixel identification. To this aim a good trade-off between the spread of light distribution, the light sampling capability over the light-sensor area and the centroiding algorithm has to be found. © 2004 IEEE.

Brain metastases are the most common tumor of the brain with a dismal prognosis. A fraction of patients with brain metastasis benefit from treatment with immune checkpoint inhibitors (ICI) and the degree and phenotype of the immune cell infiltration has been used to predict response to ICI. However, the anatomical location of brain lesions limits access to tumor material to characterize the immune phenotype. Here, we characterize immune cells present in brain lesions and matched cerebrospinal fluid (CSF) using single-cell RNA sequencing combined with T cell receptor genotyping. Tumor immune infiltration and specifically CD8+ T cell infiltration can be discerned through the analysis of the CSF. Consistently, identical T cell receptor clonotypes are detected in brain lesions and CSF, confirming cell exchange between these compartments. The analysis of immune cells of the CSF can provide a non-invasive alternative to predict the response to ICI, as well as identify the T cell receptor clonotypes present in brain metastasis., The use of CSF for diagnosis of metastatic brain tumors could be of clinical and patient benefit. Here the authors undertake a single-cell RNA analysis of CSF and brain to determine whether the phenotype in the CSF is reflective of the phenotype in the tumor.