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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.

Laser scanning is a recently-introduced remote sensing technology that shows high potentiality in the context of the forestry resources management. The research group of the University of Udine, within an INTERREG IIIA Phare/CBC Italy-Slovenia project, developed specific methods regarding the use of LiDAR data for forestry applications. A specific methodology which makes possible to obtain the position of the single trees and their relative heights has been implemented. On the basis of the height distributions, using stand height curves relation already available in the stand volume tables, a method to derive the volume values of each tree is proposed. The paper shows the first results obtained with the above method in terms of diameter and volume estimation on the basis of laser scanning data surveyed in different composed forestry plots. A comparison between laser-based and traditional methods-based data is also presented. Some of the consequences of this different way to use the stand volume tables were analyzed, and an experimental procedure is proposed that seems to guarantee a sufficient reliability of the results, and their historical continuity. Furthermore, the approach described may reduce the costs of the traditional dendrometric assessment, nowadays not sustainable in forest management.

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.

In recent works we presented the γ0, a chip expressely designed for γ imaging in medical application. The chip was designed to be the anode of an Integrated Silicon Pixel Array (ISPA) tube. This chip consists of a matrix of 1024 pixels each 135u by 135u, each pixel comprises a CSA, designed to handle signals of few thousand electrons, a shaper, a discriminator and a 10 bit event buffer. The chip addresses many issues that are essential for the realization of cheap and fast detectors. Particularly it integrates a DAC controlled biasing network and an energy discrimination system. In this work, we present the test system and the first test results for the γ0.

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.

The gamma cameras built on a LaBr3 crystal and Hamamatsu H8500 that are being developed have a number of channel that can vary from 64 to 256 depending on the number of PSPMTs that are used and, due to the gain differences, channels have to be acquired and corrected individually. In this context, the readout electronics has to be able to acquire and possibly to make computations on a high number of channels at a rate of kiloevents. A possible solution is the use of an FPGA programmed to collect the data and, in parallel, make a preliminary analysis. The high number of pins available on a modern FPGA allows to acquire and to manage all the data coming from the ADCs, driving the control signals and acquiring the data from several devices at the same time. The possibility, even on average grade FPGAs, of having clock rate in the 100 MHz range, makes it feasible to make preliminary energy discrimination in order not to overload the communication channel with the control PC that, due to the high volume of data, can became the real bottleneck of the system.

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.

In a preceding work a new compact gamma camera based on the Hamamatsu H8500 PSPMT and on a custom developed electronics was presented [1]. The core element of such electronics is a microcontroller that operates the transfer of the sampled data to a PC using a USB link in full speed modality; This transfer utilizes on one side a firmware that controls the operation performed by the microcontroller and on the other side a software that trough a graphical interface make the analysis of the acquired data possible. Both were optimized considering the nature of the data coming from the gamma camera and on the other the limitation imposed by the USB protocol. Although they were conceived for a particular gamma camera the requirements and optimizations realized still have a general interest for any position sensitive based gamma camera.

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.

The PSPMT readout systems that are generally found in technical literature are usually based on two different principles: those with single channel acquisition and those in which the channels are connected together by a resistive chain. In this paper we present a single channel acquisition readout electronics based on easily available commercial ICs. The aim of this study is to acquire valuable information for the development of an application specific integrated circuit (ASIC). The setup is a matrix of 4 Hamamatsu H8500 PSPMTs, assembled with a 10cm x 10cm LaBr3:Ce crystal. Due to the high number of channels (256) and to the connector layout, 16 different PCBs with one standalone CPU each were used in order to calculate, with a parallel algorithm, the collected charge center of gravity and to download data to a PC. The system is capable of 250 KSample/sec, a rate that is well beyond the common rates found in these kind of applications and allows to avoid dead times between the acquisition of a meaningful event and the next.

In this paper we present a new readout system for the H8500 flat panel photomultiplier. The system is based on the MAX1320 analog-to-digital converter and reads all of 64 anodic signals simultaneously at a rate that approaches the 250 ksample/s typical of MAX1320 with a resolution of 14 bits. The data are read through an FPGA by a chip computer, the ETRAX 100LX, and either transmitted via Ethernet or stored on a USB mass storage device.

We introduce a new readout system for flat panel PSPMT detectors, based on discrete semiconductors. Due to the high number of simultaneous channels to be acquired, the first and most important component selected is the 8 channel ADC with 8 different track and hold. This approach enables us to acquire each of the requested 64 anodic channels in parallel, at 250 ksps/ch, with a typical resolution of 14 bits. All the necessary 8 ADCs are controlled by an FPGA, and an embedded Linux based CPU, that made the system capable to transfer data trough the Ethernet port or store it in an USB mass storage device like the popular USB pen.

A new readout system for hybrid photon detectors is being developed by the collaboration and has been operated for the first time to test the analog front-end. In order to test its performance we used the ISPA (Imaging Silicon Pixel Array)-tube, a position sensitive photon detector based on the hybrid technology which contains a pixel detector array with 2048 pixels of 50times500 mum2 pitch. In this paper, we present the first successful application of this gamma camera prototype with a compact and portable readout system based on new electronics, able to provide full control and real-time data processing and analysis.

The ISPA (Imaging Silicon Pixel Array)-tube is a position sensitive photon detector based on the hybrid technology. It detects light via a photocathode and an appropriate electric field accelerates the emitted photoelectrons towards a silicon pixel anode. This anode, finely segmented into pixel detectors provides binary images and allows for the self-triggering of the tube. Coupled to scintillating crystals, ISPA-tubes have been successfully tested in the field of gamma ray imaging, demonstrating real capabilities in both space and energy resolution. Recently, we have concentrated our efforts on the development of a compact and portable readout system based on new electronics and able to provide full control and real-time processing of ISPA-tubes. The system overview and the dedicated interface are presented in this paper.