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Oil slicks from ships or oil platforms cause serious damage to the marine and coastal environment and ecosystems. To monitor such spill events, fully polarimetric (Pol-SAR) synthetic aperture radar (SAR) has been widely used in improving oil spillage detection performance of the image segmentation methods and machine learning methods. A key factor that greatly affects the performance of the existing methods is the use of prior knowledge, such as the manual labels of oil slicks and clean seawater. In some scenarios, a large number of trustworthy manual labels of oil slicks have been accumulated. In other scenarios, however, there are few manual labels. To efficiently utilize the manual labels in various scenarios, we propose an oil spillage identification method, named RampOC. We design cost-sensitive risk minimization model to tackle the problem of imbalance of oil slicks and seawater, employ the ramp loss function to deal with various cases of the manual labels, and design a kernel-based CCCP algorithm to train a classifier by solving a series of convex dual programming. The trained classifier is applicable to various cases, including the normal case that a certain number of the labels of oil slicks are labeled, the case that a large proportion of labels have gone missing or incorrect, and the case that no labels of oil slicks are known. In all of these cases, RampOC has proven to be effective to detect the ocean oil spillage regions. All the MATLAB source codes could be freely downloaded from https://github.com/Isaac-QiXing/rampOC.

In this paper, four non-road mobile machinery as the research object, using a portable emissions analyzer (of PEMS) were NOx emission test in the actual operation process non-road mobile machine and subjected to the processing of data in accordance with the power group window method to analyze the non-road The difference between the working conditions of the test cycle of the mobile machinery regulations and the actual working conditions. The results show that non-road mobile machinery emission regulations test cycle is difficult to represent the actual working condition of machinery, mechanical calibration and matching can be achieved through legal excessive emissions, it is necessary to introduce non-road PEMS testing methods to control the actual emissions of machinery.

The high pressure common rail fuel systems (HPCRFS) are widely utilized to meet EURO VI emissions and efficiency targets. The common rail pressure of the HPCRFS has to be extremely precisely and flexibly controlled because the common rail pressure determines the fuel injection pressure and the fuel injected quality. Therefore, an active disturbance rejection controller (ADRC) based control algorithm of the common rail pressure is proposed in order to catch up the rapid changes of the common rail pressure and balance the fluctuation of the common rail pressure. The simulation results show that ADRC based control algorithm of the common rail pressure has fast dynamic response and high control accuracy. Therefore, ADRC can be well applied to research and development on the control algorithm of the common rail pressure for the HPCRFS.

In engineering applications, related application of personnel location has become more and more popular. The global positioning system (GPS) is a classic system to locate people, vehicles and other objects. However the GPS signal cannot be received in closed space, so the localization can only be conducted through indoor positioning technologies. In this paper, we focus on the continuous positioning of people and vehicles in the tunnels. The ultra-wide-band (UWB) positioning technology is adopted, and we proposed a methods to remove the outliers to reduce the impact of NLOS transmissions. Moreover, we designed a continuous positioning algorithm based on prediction to increase the accuracy of positioning during the movement. Finally, an experimental platform was built, and the proposed scheme was evaluated. The experimental results show that the optimized algorithm can provide higher positioning accuracy and frequency than the traditional method.

Peptide sequence assignment is the central task in protein identification with MS/MS-based strategies. Sequence database searching routinely generate a large number of peptide spectrum matches (PSMs). Due to either the poor quality of the experimental MS/MS data or unexpected amino acid modifications, there are a large number of incorrect target PSMs. CRanker has shown its efficiency and accuracy in discrimination between correct and incorrect PSMs. However, it costs CRanker too much time on large PSM datasets as a built-in matlab optimization solver needs to be called for training the model. In this work, we exploit the bi-convex structure of the CRanker model and develop an alternate convex search (ACS) algorithm to reduce its total running time. At each iteration, ACS alternately solves one part of the problem when the other part of variables fixed. Compared with Matlab optimization tools, ACS is one order of magnitude faster on most datasets.

The group at University of Illinois has developed the first generation MRI compatible SPECT (MRC-SPECT-I) using 40 highly pixelated CdTe detectors. In the paper, we examined strong magnetic distortion over detector charge collection, system response, and the corresponding correction model. The system capability of working in simultaneous SPECT/MRI imaging was also demonstrated using point source and resolution phantom studies. Our results showed MRC-SPECT-I could obtain sub-500μm resolution.

Synchrotron-based X—ray fluorescence computed tomography (XFCT) is a relatively new medical imaging platform that can be used for effectively mapping indicative pathologies of metals such as copper or magnesium in Parkinson's disease and other neurodegenerative disorders [1]. At the present, the sensitivity from these potential in vivo systems is limited due to (a) the intrinsically low interaction probability of the incident X-rays, (b) the limited fluorescence signal from the sample as limited by radiation dose considerations, (c) the relatively inefficient data collection methods currently in use for most of XFCT studies, and (d) the need for high flux such as those from synchrotron X-ray sources. The authors of this work demonstrate a novel method of X-ray fluorescence-based elemental mapping, called volume selective counting, that relies on apertures designed to target a single specifically dimensioned linear segment at a time and X-ray detectors constructed in certain imaging geometries capable of deriving the elemental concentration of these trace metals inside a selected volume without the need for full 3-D image reconstruction. Cross-sectional images and spectra of both a zebra fish and triple glass phantom consisting of copper, bromide, and iron exemplify the viability and practicality of the volume-selective counting method.

In this work, we proposed a next generation MRI compatible SPECT system, MRC-SPECT-II, based on an artificial compound eye (ACE) gamma camera design inspired by compound eyes often found in small invertebrate. The MRC-SPECT II had a very compact—6cm detector ring size, but it consisted of 1536 independent micro-pinhole-gamma-camera-elements looking at the object. Each of the micro-camera-elements covered a narrow view angular in the object space. This system design could cover a FOV of 1cm diameter with a very rich angular sampling. Furthermore, the Monte Carlo study showed MRC-SPECT-II could achieve peak geometry efficiency of around 1.5% (as compared to the typical levels of 0.1%–0.01% found in modern pre-clinical SPECT instrumentations), while maintaining a spatial resolution of around 0.5 mm. Compared to the MRC-SPECT-I system that we have developed, the compact MRC-SPECT-II system could sit inside pre-clinical MRI scanner and potentially allowed us to take MRI and SPECT imaging at the same time. Also the dramatic increase in sensitivity could potentially lead to a radical change in how we might employ SPECT imagining in both pre-clinical and (potentially) clinical practice, by offering much lower detection limit and allowing for new imaging procedures that would be difficult to implement with the current generation of SPECT instrumentations.

These Handheld gamma cameras are now an important, well-established technology in the management of cancer, particularly in the detection of sentinel lymph nodes Over the past 5 years, the UI group has devoted a substantial effort in developing a series of compact and high-resolution gamma ray detectors based on small-pixel CdTe/CZT detectors. The previous generation of this detector has been used as the basic building block for a high resolution MR-compatible SPECT system that has produced some preliminary phantom images. The proposed camera modules will be based on the latest iteration of this series of development a gamma ray photon counting CdTe detector with dimension of 1.1cm× 2.2cm × 2cm, which is compact for handheld camera and probe applications. The ERPC CdTe and CDT detectors offer an excellent energy resolution (3–4keV), and a very high spatial resolution (350 um), a DOI resolution of a few hundred microns and all contained in a compact form factor. In this paper, our work will be focused on the evaluation of the ERPC detectors, especially the impact of their excellent energy resolution, spatial resolution and depth of interaction (DOI) resolution for detection and localization of small lesions superimposed on noisy background. These results will be discussed in this paper.

Synchrotron-based X-ray fluorescence computed tomography (XFCT) is a common technique for mapping metal ions in biological specimens. In recent years, it has been demonstrated that various metal ions could play critical roles in disease and general biological functions. In this work, we are developing a benchtop x-ray fluorescence emission tomography system that utilizes combines charge-coupled device (CCD) detectors and special emission tomography apertures to obtain 3-D mapping of elemental distribution in intact biological samples. We have carried out a series of studies that utilize multiple slit apertures and a monochromatic pencil beam x-ray source to image a triple-tube sample and an osmium stained zebrafish.

This paper presents the basic design of a dual-mode readout system for MR-Compatible ultrahigh resolution SPECT/PET system, especially the design of a cathode waveform sampling and processing unit. This effort was motivated by the development of a stationary CdTe detector based MR Compatible SPECT system. In our previous study, this CdTe detector shows around 3kev energy resolution around 140kev for SPECT imaging and 500μm spatial resolution with a prototype system inside a 3T Siemens MR scanner. With MR compatible rapid-prototyping made polyamide housing and proper compress air system cooling design, we expect this multi-head ring detectors can work well inside/outside MR scanner to serve as an ultrahigh resolution SPECT system. In addition, the ultrahigh resolution CdTe detectors used in the MRC-SPECT system also has the potential of serving as an ultrahigh resolution PET system. The original readout system designed for this detector only reads out anode pixels using four 2-D energy-resolved photon-counting (ERPC) ASICs. If we want to push this system into PET use, we would need to add another readout system that reads out and processes the cathode waveform. The added waveform sampling circuitry could provide a precise timing and depth-of-interaction (DOI), which are cortically needed for high resolution PET imaging. The cathode readout system consists of four low-noise pre-amplifiers connecting to individual cathodes of the detector and a fast sampling AD converter is used to digitize the signal waveforms (WFs) induced on the cathodes. Digitized data will be stored in a group of ring-buffers on a FPGA which also implements a lookup table for storing a series of predetermined WF models. Precise interaction time, DOI and energy-deposition are achieved by comparing the sampled WF with the pre-stored WF models and finding the best fit. By integrating these two readout systems, we can choose this ring detection system to work either in MR/SPECT or MR/PET mode.

This paper presents the design and experimental results obtained with a prototype adaptive SPECT that implements a recently developed adaptive angular sampling approach. With this system, the hardware system configuration can be adjusted in real time based on the imaging information being collected to offer an optimum sampling of an unknown object. This system consists of two major components. First, the detection system consists of two independent pinhole cameras based on recently developed energy-resolved photon-counting (ERPC) CdTe detectors. During an imaging study, both the detectors and pinhole apertures can move back and forth independently against the rotation object. This system also include a CT system that provides the physical profile of the object, and helps to determine the feasible sampling strategy for the given source geometry. Second, the adaptive angular sampling is controlled by a software package that consists of three key components: (a) a set of close-form equations for evaluating image variance and resolution attainable with given sampling strategy, (b) a gradient-based algorithm to search the optimum sampling strategy, (c) an efficient computation approach for speeding up the searching process. During an imaging study, the corresponding computation is performed on a PC to determine the optimum sampling and to guide the hardware configuration to be adjusted accordingly. We carried a series of experimental studies to demonstrate the benefit using this self-optimized adaptive angular sampling strategy. The SPECT imaging performance obtained is compared to those from conventional uniform sampling strategies.

This paper presents an adaptive angular sampling approach developed for SPECT systems that require the rotation of the detection system to obtain an adequate angular sampling. The basic idea of the approach is to assign different imaging times across possible sampling angles, based on the efficiency of the camera(s) at each possible angle for collecting imaging information. In this study, we used the resolution-variance tradeoffs and bias-variance tradeoffs as performance indices for guiding the adaptive angular sampling strategy, and applied a highly efficient computation scheme, based on the non-uniform object-space pixilation methods, for deriving the optimum time distribution in near real-time. This approach allows an optimum efficiency for collecting imaging information and therefore offers an improved image quality.

A coincidence detection system between 350μm pitch pixelated CZT detector and a LSO-based Inveon PET detector was built up for PET imaging application. Using different trigger mode, we studied how the triggering strategy affects the PET imaging resolution. We obtained 670μm at FWHM image resolution for coincidence events detected by CZT central pixel only. If we include coincidence events from CZT double-pixel charge sharing events (while the CZT central pixel still got the biggest signal amplitude), the PET image resolution degrades to 730μm FWHM, but the count rate increases 2.5 to 3 times. We estimated the CZT timing property in different coincidence approaches, i.e. triggered by CZT anode signal or LSO signal, based on the electron drift time measurement from one flash ADC system and the measurement of trigger time difference of LSO and CZT signals.

This paper presents preliminary experimental results obtained with a prototype SPECT system for small animal studies. This system is based on novel energy-resolved photon counting (ERPC) detectors we have recently developed for gamma ray imaging applications. The ERPC detector has basic modular configuration that offers an overall detection area of 4.5 cm × 4.5 cm, comprising of eight CdTe/CMOS detector hybrids. Each hybrid has a CdTe detector of 11 mm × 22 mm bump-bonded onto a dedicated readout ASIC that has 32 × 64 readout pixels with 350 μm pitch size. The 1mm and 2mm thickness CdTe detector have both been developed. This configuration offers a very-high spatial resolution of around 350 μm and an excellent energy resolution of around 3∼4 keV at 140 keV. The prototype SPECT system that consists of two or four ERPC detectors is mounted on a system gantry rotating around a horizontal axis. The detectors are coupled to apertures with differently sized pinholes. In order to utilize the imaging information provided by the ERPC detector, we have developed a comprehensive system modelling and calibration method that accounts for the irregular shapes and physical details in the collimation apertures. Detailed system design and experimental procedures will be described in this paper.

We have been working to develop and implement faster synchrotron-based X-ray fluorescence computed tomography (XFCT) methods for the mapping of trace metals in biological samples. As practiced now, the XFCT image acquisition process is slow (on the order of 1 or more hours per slice), which severely limits the ability to perform 3D imaging and to image multiple samples for sake of comparison and improved experimental statistics. This is because the data needed for tomographic reconstruction are acquired line-by-line in a first-generation tomo-graphic geometry. Recently, we have been demonstrated the feasibility of using emission tomography systems for synchrotron X-ray fluorescence computer tomography. The proposed detection system combines high-resolution semiconductor detectors with multiple-pinhole apertures. The most promising acquisition mode involves using a sheet-collimated beam to illuminate a single plane through the object, which can then be directly imaged through the pinholes without need for tomographic reconstruction. Monte Carlo and experimental studies demonstrated the potential for order-of-magnitude improvements in SNR or imaging speed using this strategy. Some have found this surprising since the use of a pinhole collimator greatly reduces the detection efficiency of the system. In the present paper, we derive analytic figures of merit based on the ideal observer signal to noise ratio for the two geometries. These FOMs provide simple analytic insight into the reason for the improvement obtained with the pinhole-based system: the low detection efficiency is more than compensated for by avoiding the ill-posedness of tomographic reconstruction. The derived FOMs also provide a basis for performing system optimization.

In this paper, we will present a preliminary study based on a prototype of the MRI-compatible, ultra-high resolution SPECT system for use in a pre-existing Siemens 3.0 T MR scanner. The system uses an ultra-high special resolution energy-resolved photon-counting (ERPC) CdTe detector that we have recently developed. This detector consists of eight detector hybrids, each having a pixilated CdTe detector of 1mm thickness, bump-bonded to a custom-designed CMOS readout ASIC. Each detector hybrid offers an imaging area of 1.1cm × 2.2cm that is divided into an array of 32 × 64 pixels with a pitch size of 350μm × 350μm. A prototype SPECT system has been designed and tailored for use inside the 3.0 T Siemens scanner for tomographic imaging. It consists of a single ERPC detector head, coupled to a collimation aperture. The system is supported by a non-magnetic gantry that allows the system to be moved in and out the Siemens scanner and to be rotated around the object to obtain a sufficient angular sampling. All shielding, supporting and cooling structures are proved to be MRI-compatible. The imaging performance of the prototype system with presence of magnetic field will be evaluated by using image of the Co57 point source and the results will be presented.

Use of fuzzy mathematics in evaluation of thermal and moisture comfort of ramie fabrics and bamboo-cotton fabrics is introduced. The thermal transmittance, air permeability, moisture vapor transmission, and hygroscopicity of fabrics with different specifications are tested, and their thermal and moisture transmitting properties are compared with that of silk fabrics through fuzzy similar priority ratio analysis, and the moisture transmitting properties of the fabrics are listed in the order from good to bad, in order to study the relationship among raw material, structure and thermal and moisture comfort of fabrics, which shows that this method is effective to evaluate thermal and moisture comfort of fabrics, thus providing a theoretical basis for investigation and research of fabric design and thermal and moisture comfort of fabric.

In this paper, we report the design and feasibility study of a high resolution and high sensitivity SPECT (Gamma-Cube) system for mouse brain imaging. The system consists of six high resolution gamma ray detectors, arranged in cubic geometry, and a truncated spherical aperture with multiple pinholes, which offers a relatively uniform 4π angular coverage around the object. The proposed Gamma-Cube system is based on the so-called energy-resolved photon-counting (ERPC) detector that consists of multiple pixilated CdTe detectors bump-bonded to ERPC readout ASICs that are 1.1×2.2cm in size with a pixel pitch of 350μm×350μm. In this study, we used Monte Carlo simulation to optimize system geometry and multiple-pinhole patterns for detection of a tiny amount of radioactivity in mouse brain.

Recent improvements in detector technology allow pinhole SPECT to approach spatial resolutions as low as 50 mum. Such high resolutions require a high accuracy of the imaging gantry for preclinical SPECT systems, and is not easily achieved in a laboratory setting. Analytical calibration methods are deemed to fail due to practical implications such as size and activity concentrations of the required point sources. Thus, we have developed a numerical calibration method based on least-square optimization that incorporates the modeling attributes of a forward projector frequently used in iterative reconstruction. The forward projector is currently capable of modeling detector misalignment such as detector rotation and pinhole translation, and will incorporate the pinhole point spread function as well as the size and shape of the point source. Currently, our calibration phantom consists of a single point source, positioned off-center in the object space. The optimization method involves a sequentially fitting of each individual parameter to the data, followed by fitting multiple parameters simultaneous in consecutive steps including all five parameters for the final fitting. The results of the optimization show an error of expected magnitude considering the relatively coarse sampling grid of our simulations. The relatively slow convergence of the y- and z-tilt require simulation of additional point sources. Further improvements of computational and memory efficiency need to be made, which enable the method to fit high resolution data as well as incorporation of the pinhole point spread function and the shape and size of the point sources.

This paper presents the design study of an MRI compatible, ultra-high resolution SPECT system. This system consists of multiple ultra-high resolution energy-resolved photon counting (ERPC) CdTe detectors that are currently development. This detector is based on a novel readout ASIC that is roughly 1.1times2.2 cm2 in size and has a 32times64 array of 350times350 um2 pixels. A prototype detector was tested inside a 4.7 Tesla MRI scanner for simple pinhole imaging. The results obtained have demonstrated the feasibility of simultaneous acquisition of SPECT and MRI data. Extensive Monte Carlo simulation was performed to evaluate a number of system configurations.

In this paper, we present the results from a design study for an ultra-high resolution SPECT system with various aperture designs. The system uses a recently developed ultrahigh resolution gamma camera based on an intensified Electron- multiplying Charge Coupled Device (EMCCD) sensor. It provides an intrinsic spatial resolution of < 60 mum and a high signal-to-noise ratio for imaging the 27-35 keV photons emitted by 1-125. The goal of present work is to optimize the multiple- pinhole aperture design for a stationary 4 headed SPECT system. The system is equipped with a variable aperture system that allows a large number of different aperture configurations to be used. In this study, we used the resolution-variance tradeoff as a performance index for selecting appropriate apertures for several imaging scenarios. A large number of apertures were compared with Monte Carlo simulations and experimental measurements.

This paper presents the design of dispersion movement and concentration movement for a multi-robot team to search for targets in an unknown environment. The goal of the dispersion movement is for the multi-robot team to spread out as widely as possible and explore any unknown targets without breaking the communication links among these robots. The movement direction is made based on only minimal available communication data. After one of the team members finding a target, other robots are commanded by the concentration algorithm to move to the same target location to, for example, retrieve the explored target or transport the target cooperatively. The only information used for designing the movement algorithms is the number of robots within the communication range of the robot. The proposed algorithms have been extensively tested by the simulation study. The simulation results demonstrate the feasibility and fast convergence of the proposed algorithms in several typical scenarios presented in this paper. Potential applications of the proposed algorithms include rescue in a damaged area, planetary exploration, military reconnaissance, and geophysical mapping.

An experimental small animal PET using two 3-D position sensitive CdZnTe detectors was developed and tested. Each 1.5/spl times/1.5/spl times/1 cm/sup 3/ CdZnTe detector employs 11 by 11 pixellated anodes wire-bonded to the VAS3.1/TAT3/MCR3 readout electronics. Each detector can obtain the deposited energy and 3-D coordinates for single-pixel and multiple-pixel events. Both systems achieved energy resolutions of better than 1.0% FWHM at 662 ReV for single-pixel events and better than 1.5% FWHM at 662 ReV for two-pixel events. The position resolution of each detector was estimated to be /spl sim/1.3/spl times/1.3/spl times/0.5 mm/sup 3/. Modifications to the firmware of the readout board and additions of custom-built circuitry enabled coincidence measurement between two 3-D CdZnTe detector systems using VAS3.1/TAT3/MCR3 readout systems. Spatial resolution improvements by using depth of interaction (DOI) and by identifying the first interaction using Compton scattering angle reconstruction are reported and discussed.

This paper presents preliminary results achieved using an ultra-high resolution pinhole SPECT system for small animal imaging using I-125 radiotracers. This system is based on a very-high resolution gamma camera that consists of an intensified EMCCD (I-EMCCD) camera coupled to columnar CsI(Tl) scintillators. The I-EMCCD camera provides an active area of ~80mm diameter, an intrinsic resolution of ~60mum and a near perfect photon counting efficiency for detecting 27-35keV photons emitted by I-125. A single pinhole aperture with a 100mum diameter pinhole was used in these imaging studies based on both phantoms and mice injected with 1-125 NaCl solution. A reconstructed spatial resolution of

In this paper, we present the design and the results of a feasibility study of a novel, ultra-fast and high-resolution PET detector. It is based on the use of an LSO crystal array read-out by a Multi pixel Hybrid PhotoDiode (M-HPD) using an encoded fiber light-guide. The fiber encoding method enables one to readout more than 400 discrete crystal elements using a single M-HPD tube having 61 pixels. One of the key features of the detector is that the encoded fiber light-guide, used in conjunction with a digital readout system, eliminates the need for the use of ADCs in finding the address of the crystal in which interaction occurred. The readout time of a detector comprising around four hundred 2/spl times/2/spl times/10 mm discrete crystals, defined as the time between identifying a coincidence and providing the address of the crystal hit, can be reduced to less than 0.1 /spl mu/s. As a consequence, one could significantly improve the noise-effective-count-rate (NECR) performance of a PET system based on this detector design. Another advantage of this detector design is that the parallel readout scheme used, greatly simplifies the readout electronics by eliminating the use of ADC in the readout system. The feasibility of this detector design has been confirmed by measurements using a prototype detector module based on a 5/spl times/5 array of 2/spl times/2/spl times/10 mm LSO crystals. A signal level of around 200 photoelectrons has been measured for 511 keV energy deposited in the detector. An energy-resolution of /spl sim/30% and a timing resolution of less than 4 ns were achieved in this study.

The new scintillation detectors, CsI(Tl) + Si PIN photodiode, were developed in the Kurchatov Institute. The current state of the developed spectrometric probes are large volume (10-300cm3) scintillation detectors intended for gamma-ray spectroscopy. These detectors consist of a spherical CsI(Tl) crystal packed in MgO powder within a cylindrical aluminum housing and a Hamamatsu photodiode. Environmental devices based on the above probes uses methods of field spectrometry. They include spectrometric electronics and algorithms for spectra processing to obtain particular characteristics of environmental radioactivity or radioactive contamination. The description of measurement techniques used with devices, their performance parameters and results of their practical applications are presented.

Arrays of small scintillation crystals are being used increasingly for high-resolution imaging applications in nuclear medicine. Although the degree of pixellation now available is high for some scintillation materials, this spatial resolution is often achieved at the expense of degraded energy resolution due to the lower, and more variable, light-collection efficiency. The energy resolution of a detector is, however, especially important in nuclear medicine, where events that have been scattered in the body need to be rejected efficiently. The light output from a range of CsI(Tl) arrays was measured in terms of the number of photoelectrons; detected, using a hybrid photodiode (HPD). This data, used in conjunction with the measured energy resolution and an estimate of the intrinsic energy resolution of CsI(Tl), were used to assess the magnitudes of the various contributions to the overall energy resolution of these detectors. This information suggested that there is an opportunity to improve their energy resolution by carefully choosing the geometry and reflector material to minimize the variance in the light collection. If the nature of this variance is understood sufficiently well, there may be an opportunity to apply a postprocessing technique similar to that that has dramatically improved the performance of other standard scintillation detectors. This possibility depends on the use of either the uniform quantum efficiency of the multipixel HPD photocathodes or a monolithic array of PIN diodes. This would ensure that no additional or indeterminate variance in the light collection is introduced. Measurements made using fine BGO arrays for higher energy applications and columnar grown CsI(Tl) for X-ray imaging will also be presented.

Pixellated mercuric iodide (HgI2) detectors with thickness of 5 and 10 mm have been investigated using depth sensing single polarity charge sensing technique at room temperatures. By acquiring energy spectra of 137Cs as a function of the interaction depth, an insensitive region exhibiting poor spectroscopic performance was observed in the vicinity of the cathode surface of a 10 mm thick HgI2 detector operated at 2500 V, while the other regions of the detector present clear photo peaks with good energy resolutions. The thickness of the insensitive region is estimated to be around 2 mm. The electron mobility-lifetime (mutau) product was estimated based on the change of photopeak amplitude at different bias voltages. The value of electron mutau product was estimated to be around 1.9times10-3 cm2/V which is smaller than the value of 7.4times10-3 cm2/V reported earlier

Describes the design of a fast imaging system aimed at providing the accurate location of the centroid of a sentinel lymph node. Through the proposed use of a new 80 mm diameter multi-pixel hybrid photo-diode, equipped with a fibre-optic window, a CsI(Tl) scintillation crystal and a specially optimised collimator, the authors expect to achieve a precision of /spl plusmn/3 mm within 20 s for the location of a lymph node. It has been assumed that the affected gland has a 10 mm diameter and had accumulated 3 /spl mu/Ci of /sup 99/Tc through drainage of the region of the breast. The paper discusses the likely imaging quality of the larger tube based on measurements made with a smaller prototype detector. The design of two collimators is presented; one to provide a rapid location of the centroid of the SLN and the other to provide the surgeon with a measure of the depth of the potentially infected organ. A method for relating the image information to the patient's anatomy to guide the surgeon is also presented.

The basis for a design of a high-resolution PET imaging system, utilising a wavelength-shifting (WLS) fibre readout technique is presented here. Scintillation light is transported from the individual LSO pixels in the detector array through the WLS fibres to a multi-pixel hybrid photodiode (M-HPD). Each detector array consists of a number of 2/spl times/2/spl times/10 mm LSO crystals viewed by two orthogonal ribbons of WLS fibres. An array of as many as 30/spl times/31 crystals can thus be read-out by a single, small 61-pixel M-HPD tube. The design is both compact, inexpensive and suitable for application not only in the field of small-animal PET or in a dedicated PEM system, but could also operate in a combined PET/MRI system. Initial tests have shown that the signal level generated at the detector by a single 511 keV energy-deposit, is 20-25 photoelectrons. Separate tests have indicated that, at this signal-level, a resolving time of /spl sim/25 ns could be achievable.

This paper presents the design and initial experimental results of a gamma camera using a coded aperture with clustered non-redundant array pattern. This system is based on the use of 5" position sensitive photomultiplier tube coupled to pixelated BGO array with 2/spl times/2/spl times/10mm/sup 3/ pixels. The PSPMT is readout by the IDEAS VA-MCR system with a costume made front electronic. This gamma camera was designed for imaging gamma rays with a broad energy range. The collimator plate was made of Tungsten of 8 mm thick for reducing the effect of gamma ray penetration. For imaging source objects with a relatively large angular extent and high background, the use of clustered NRA offers great flexibility in aperture design that provides a wide view angle and a controlled data multiplexing. In order to replace the time consuming Monte Carlo simulations, we also presented an analytical method for calculating performance indices, such as pixel-wise signal-to-noise ratio and resolution/variance tradeoffs achievable with different detector designs. This helps to select an approximate aperture for given imaging tasks.

Recent measurements of the performance of the newly available multi-pixel hybrid photo-detector (M-HPD) have demonstrated their particular value in the detection of very low light-level signals. The single and multiple photo-electron response characteristics of these devices is unmatched by any other room-temperature device. This characteristic, coupled with their speed of response and the availability of an internally-generated trigger signal when any one of the pixels detects an event, makes them well suited for the detection of minimum ionizing particles (MIPs). These detectors may therefore be expected to find application in particle-tracking applications both in High-Energy Physics and Gamma-ray Astronomy. The result of tests made using single and double-clad plastic fibres have confirmed the usefulness of these devices. The technique used to read-out 61 channels of data is described along with a way of viewing as many as 2000 fibres with just two 61-pixel M-HPDs.

Recent developments in the application of maximum likelihood expectation maximisation (MLEM) techniques to the deconvolution of low-resolution gamma-ray spectra have demonstrated a substantial improvement in both the energy-resolution and sensitivity achievable with the industry-standard 3" NaI scintillation counter. This technique can be used to determine the specific activities of the radioisotopes present in low-activity materials. In this paper, a practical application of this method for measuring the cement content of concrete in real-time is presented. However, the technique can be applied in many other fields.