Method and system for improved resolution of a compensated calorimeter detector

DOEpatents

Dawson, John W.

1991-01-01

An improved method and system for a depleted uranium calorimeter detector used in high energy physics experiments. In a depleted uranium calorimeter detector, the energy of a particle entering the calorimeter detector is determined and the output response of the calorimeter detector is compensated so that the ratio of the integrated response of the calorimeter detector from a lepton to the integrated response of the calorimeter detector from a hadron of the same energy as the lepton is approximately equal to 1. In the present invention, the energy of a particle entering the calorimeter detector is determined as a function of time and the hadron content of the response of the calorimeter detector is inferred based upon the time structure of the energy pulse measured by the calorimeter detector. The energy measurement can be corrected based on the inference of the hadron content whereby the resolution of the calorimeter can be improved.

Method and system for determining depth distribution of radiation-emitting material located in a source medium and radiation detector system for use therein

DOEpatents

Benke, Roland R.; Kearfott, Kimberlee J.; McGregor, Douglas S.

2004-04-27

A radiation detector system includes detectors having different properties (sensitivity, energy resolution) which are combined so that excellent spectral information may be obtained along with good determinations of the radiation field as a function of position.

A CMOS-based high-resolution fluoroscope (HRF) detector prototype with 49.5μm pixels for use in endovascular image guided interventions (EIGI)

NASA Astrophysics Data System (ADS)

Russ, M.; Shankar, A.; Setlur Nagesh, S. V.; Ionita, C. N.; Bednarek, D. R.; Rudin, S.

2017-03-01

X-ray detectors to meet the high-resolution requirements for endovascular image-guided interventions (EIGIs) are being developed and evaluated. A new 49.5-micron pixel prototype detector is being investigated and compared to the current suite of high-resolution fluoroscopic (HRF) detectors. This detector featuring a 300-micron thick CsI(Tl) scintillator, and low electronic noise CMOS readout is designated the HRF- CMOS50. To compare the abilities of this detector with other existing high resolution detectors, a standard performance metric analysis was applied, including the determination of the modulation transfer function (MTF), noise power spectra (NPS), noise equivalent quanta (NEQ), and detective quantum efficiency (DQE) for a range of energies and exposure levels. The advantage of the smaller pixel size and reduced blurring due to the thin phosphor was exemplified when the MTF of the HRF-CMOS50 was compared to the other high resolution detectors, which utilize larger pixels, other optical designs or thicker scintillators. However, the thinner scintillator has the disadvantage of a lower quantum detective efficiency (QDE) for higher diagnostic x-ray energies. The performance of the detector as part of an imaging chain was examined by employing the generalized metrics GMTF, GNEQ, and GDQE, taking standard focal spot size and clinical imaging parameters into consideration. As expected, the disparaging effects of focal spot unsharpness, exacerbated by increasing magnification, degraded the higher-frequency performance of the HRF-CMOS50, while increasing scatter fraction diminished low-frequency performance. Nevertheless, the HRF-CMOS50 brings improved resolution capabilities for EIGIs, but would require increased sensitivity and dynamic range for future clinical application.

Pulse height tests of a large diameter fast LaBr₃:Ce scintillation detector.

PubMed

Naqvi, A A; Khiari, F Z; Maslehuddin, M; Gondal, M A; Al-Amoudi, O S B; Ukashat, M S; Ilyas, A M; Liadi, F A; Isab, A A; Khateeb-ur Rehman; Raashid, M; Dastageer, M A

2015-10-01

The pulse height response of a large diameter fast 100 mm × 100 mm LaBr3:Ce detector was measured for 0.1-10 MeV gamma-rays. The detector has a claimed time resolution of 608 ps for 511 keV gamma rays, but has relatively poor energy resolution due to the characteristics of its fast photomultiplier. The detector pulse height response was measured for gamma rays from cobalt, cesium, and bismuth radioisotope sources as well as prompt gamma rays from thermal neutron capture in water samples contaminated with mercury (3.1 wt%), boron (2.5 wt%), cadmium (0.25 wt%), chromium (52 wt%), and nickel (22 wt%) compounds. The energy resolution of the detector was determined from full width at half maximum (FWHM) of element-characteristic gamma ray peaks in the pulse height spectrum associated with the element present in the contaminated water sample. The measured energy resolution of the 100 mm × 100 mm detector varies from 12.7±0.2% to 1.9±0.1% for 0.1 to 10 MeV gamma rays, respectively. The graph showing the energy resolution ΔE/E(%) versus 1/√Eγ was fitted with a linear function to study the detector light collection from the slope of the curve. The slope of the present 100 mm × 100 mm detector is almost twice as large as the slope of a similar curve of previously published data for a 89 mm × 203 mm LaBr3:Ce detector. This indicates almost two times poorer light collection in the 100 mm × 100 mm detector as compared to the other detector. Copyright © 2015 Elsevier Ltd. All rights reserved.

Enhancing the detector for advanced neutron capture experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Couture, A.; Mosby, S.; Baramsai, B.

2015-05-28

The Detector for Advanced Neutron Capture Experiments (DANCE) has been used for extensive studies of neutron capture, gamma decay, photon strength functions, and prompt and delayed fission-gamma emission. Despite these successes, the potential measurements have been limited by the data acquisition hardware. We, thus, report on a major upgrade of the DANCE data acquisition that simultaneously enables strait-forward coupling to auxiliary detectors, including high-resolution high-purity germanium detectors and neutron tagging array. Furthermore, the upgrade will enhance the time domain accessible for time-of-flight neutron measurements as well as improve the resolution in the DANCE barium fluoride crystals for photons.

Status of the EDDA experiment at COSY

NASA Astrophysics Data System (ADS)

Scobel, W.; EDDA Collaboration; Bisplinghoff, J.; Bollmann, R.; Cloth, P.; Dohrmann, F.; Dorner, G.; Drüke, V.; Ernst, J.; Eversheim, P. D.; Filges, D.; Gasthuber, M.; Gebel, R.; Groß, A.; Groß-Hardt, R.; Hinterberger, F.; Jahn, R.; Lahr, U.; Langkau, R.; Lippert, G.; Mayer-Kuckuk, T.; Maschuw, R.; Mertler, G.; Metsch, B.; Mosel, F.; Paetz gen Schieck, H.; Petry, H. R.; Prasuhn, D.; von Przewoski, B.; Rohdjeß, H.; Rosendaal, D.; von Rossen, P.; Scheid, H.; Schirm, N.; Schwandt, F.; Stein, H.; Theis, D.; Weber, J.; Wiedmann, W.; Woller, K.; Ziegler, R.

1993-07-01

The EDDA experiment is designed to study p + p excitation functions with high energy resolution and narrow step size in the kinetic energy range from 250 MeV to 2500 MeV at the Cooler Synchrotron COSY. Measurements during the accelertion phase in conjunction with internal targets will allow to achieve a fast and precise energy variation. Prototypes of the detector elements and the fiber target have been extensively tested with proton and electron beams; the detector performance and trigger efficiency have been studied in Monte Carlo simulations. In this contribution, results concerning detector design, prototype studies, Monte Carlo simulations and the anticipated detector resolutions will be reported.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melnyk, Roman; DiBianca, Frank A.

The detector presampling modulation transfer function (MTF) of a 576-channel variable resolution x-ray (VRX) computed tomography (CT) scanner was evaluated in this study. The scanner employs a VRX detector, which provides increased spatial resolution by matching the scanner's field of view (FOV) to the size of an object being imaged. Because spatial resolution is the parameter the scanner promises to improve, the evaluation of this resolution is important. The scanner's pre-reconstruction spatial resolution, represented by the detector presampling MTF, was evaluated using both modeling (Monte Carlo simulation) and measurement (the moving slit method). The theoretical results show the increase inmore » the cutoff frequency of the detector presampling MTF from 1.39 to 43.38 cycles/mm as the FOV of the VRX CT scanner decreases from 32 to 1 cm. The experimental results are in reasonable agreement with the theoretical data. Some discrepancies between the measured and the modeled detector presampling MTFs can be explained by the limitations of the model. At small FOVs (1-8 cm), the MTF measurements were limited by the size of the focal spot. The obtained results are important for further development of the VRX CT scanner.« less

Saturated virtual fluorescence emission difference microscopy based on detector array

NASA Astrophysics Data System (ADS)

Liu, Shaocong; Sun, Shiyi; Kuang, Cuifang; Ge, Baoliang; Wang, Wensheng; Liu, Xu

2017-07-01

Virtual fluorescence emission difference microscopy (vFED) has been proposed recently to enhance the lateral resolution of confocal microscopy with a detector array, implemented by scanning a doughnut-shaped pattern. Theoretically, the resolution can be enhanced by around 1.3-fold compared with that in confocal microscopy. For further improvement of the resolving ability of vFED, a novel method is presented utilizing fluorescence saturation for super-resolution imaging, which we called saturated virtual fluorescence emission difference microscopy (svFED). With a point detector array, matched solid and hollow point spread functions (PSF) can be obtained by photon reassignment, and the difference results between them can be used to boost the transverse resolution. Results show that the diffraction barrier can be surpassed by at least 34% compared with that in vFED and the resolution is around 2-fold higher than that in confocal microscopy.

Monte Carlo study of x-ray cross talk in a variable resolution x-ray detector

NASA Astrophysics Data System (ADS)

Melnyk, Roman; DiBianca, Frank A.

2003-06-01

A variable resolution x-ray (VRX) detector provides a great increase in the spatial resolution of a CT scanner. An important factor that limits the spatial resolution of the detector is x-ray cross-talk. A theoretical study of the x-ray cross-talk is presented in this paper. In the study, two types of the x-ray cross-talk were considered: inter-cell and inter-arm cross-talk. Both types of the x-ray cross-talk were simulated, using the Monte Carlo method, as functions of the detector field of view (FOV). The simulation was repeated for lead and tungsten separators between detector cells. The inter-cell x-ray cross-talk was maximum at the 34-36 cm FOV, but it was low at small and the maximum FOVs. The inter-arm x-ray cross-talk was high at small and medium FOVs, but it was greatly reduced when variable width collimators were placed on the front surfaces of the detector. The inter-cell, but not inter-arm, x-ray cross-talk was lower for tungsten than for lead separators. From the results, x-ray cross-talk in a VRX detector can be minimized by imaging all objects between 24 cm and 40 cm in diameter with the 40 cm FOV, using tungsten separators, and placing variable width collimators in front of the detector.

Modeling blur in various detector geometries for MeV radiography

NASA Astrophysics Data System (ADS)

Winch, Nicola M.; Watson, Scott A.; Hunter, James F.

2017-03-01

Monte Carlo transport codes have been used to model the detector blur and energy deposition in various detector geometries for applications in MeV radiography. Segmented scintillating detectors, where low Z scintillators combined with a high-Z metal matrix, can be designed in which the resolution increases with increasing metal fraction. The combination of various types of metal intensification screens and storage phosphor imaging plates has also been studied. A storage phosphor coated directly onto a metal intensification screen has superior performance over a commercial plate. Stacks of storage phosphor plates and tantalum intensification screens show an increase in energy deposited and detective quantum efficiency with increasing plate number, at the expense of resolution. Select detector geometries were tested by comparing simulation and experimental modulation transfer functions to validate the approach.

Development of New High Resolution Neutron Detector

NASA Astrophysics Data System (ADS)

Mostella, L. D., III; Rajabali, M.; Loureiro, D. P.; Grzywacz, R.

2017-09-01

Beta-delayed neutron emission is a prevalent form of decay for neutron-rich nuclei. This occurs when an unstable nucleus undergoes beta decay, but produces a daughter nucleus in an excited state above the neutron separation energy. The daughter nucleus then de-excites by ejecting one or more neutrons. We wish to map the states from which these nuclei decay via neutron spectroscopy using NEXT, a new high resolution neutron detector. NEXT utilizes silicon photomultipliers and 6 mm thick pulse-shape discriminating plastic scintillators, allowing for smaller and more compact modular geometries in the NEXT array. Timing measurements for the detector were performed and a resolution of 893 ps (FWHM) has been achieved so far. Aspects of the detector that were investigated and will be presented here include scintillator geometry, wrapping materials, fitting functions for the digitized signals, and electronic components coupled to the silicon photomultipliers for signal shaping.

Energy reconstruction of an n-type segmented inverted coaxial point-contact HPGe detector

DOE PAGES

Salathe, M.; Cooper, R. J.; Crawford, H. L.; ...

2017-06-27

We have characterized, for the rst time, an n-type segmented Inverted Coaxial Point-Contact detector. This novel detector technology relys on a large variation in drift time of the majority charge carriers, as well as image and net charges observed on the segments, to achieve a potential -ray interaction position resolution of better than 1 mm. However, the intrinsic energy resolution in such a detector is poor (more than 20 keV at 1332 keV) because of charge (electron) trapping e ects. We propose an algorithm that enables restoration of the resolution to a value of 3.44 0.03 keV at 1332 keVmore » for events with a single interaction. The algorithm is based on a measurement of the azimuthal angle and the electron drift time of a given event; the energy of the event is corrected as a function of these two values.« less

Performance improvements of wavelength-shifting-fiber neutron detectors using high-resolution positioning algorithms

DOE PAGES

Wang, C. L.

2016-05-17

On the basis of FluoroBancroft linear-algebraic method [S.B. Andersson, Opt. Exp. 16, 18714 (2008)] three highly-resolved positioning methods were proposed for wavelength-shifting fiber (WLSF) neutron detectors. Using a Gaussian or exponential-decay light-response function (LRF), the non-linear relation of photon-number profiles vs. x-pixels was linearized and neutron positions were determined. The proposed algorithms give an average 0.03-0.08 pixel position error, much smaller than that (0.29 pixel) from a traditional maximum photon algorithm (MPA). The new algorithms result in better detector uniformity, less position misassignment (ghosting), better spatial resolution, and an equivalent or better instrument resolution in powder diffraction than the MPA.more » Moreover, these characters will facilitate broader applications of WLSF detectors at time-of-flight neutron powder diffraction beamlines, including single-crystal diffraction and texture analysis.« less

Effects of Detector Thickness on Geometric Sensitivity and Event Positioning Errors in the Rectangular PET/X Scanner

NASA Astrophysics Data System (ADS)

MacDonald, Lawrence R.; Hunter, William C. J.; Kinahan, Paul E.; Miyaoka, Robert S.

2013-10-01

We used simulations to investigate the relationship between sensitivity and spatial resolution as a function of crystal thickness in a rectangular PET scanner intended for quantitative assessment of breast cancers. The system had two 20 × 15-cm2 and two 10 × 15-cm2 flat detectors forming a box, with the larger detectors separated by 4 or 8 cm. Depth-of-interaction (DOI) resolution was modeled as a function of crystal thickness based on prior measurements. Spatial resolution was evaluated independent of image reconstruction by deriving and validating a surrogate metric from list-mode data ( dFWHM). When increasing crystal thickness from 5 to 40 mm, and without using DOI information, the dFWHM for a centered point source increased from 0.72 to 1.6 mm. Including DOI information improved dFWHM by 12% and 27% for 5- and 40-mm-thick crystals, respectively. For a point source in the corner of the FOV, use of DOI information improved dFWHM by 20% (5-mm crystal) and 44% (40-mm crystal). Sensitivity was 7.7% for 10-mm-thick crystals (8-cm object). Increasing crystal thickness on the smaller side detectors from 10 to 20 mm (keeping 10-mm crystals on the larger detectors) boosted sensitivity by 24% (relative) and degraded dFWHM by only 3%/8% with/without DOI information. The benefits of measuring DOI must be evaluated in terms of the intended clinical task of assessing tracer uptake in small lesions. Increasing crystal thickness on the smaller side detectors provides substantial sensitivity increase with minimal accompanying loss in resolution.

Design principles and applications of a cooled CCD camera for electron microscopy.

PubMed

Faruqi, A R

1998-01-01

Cooled CCD cameras offer a number of advantages in recording electron microscope images with CCDs rather than film which include: immediate availability of the image in a digital format suitable for further computer processing, high dynamic range, excellent linearity and a high detective quantum efficiency for recording electrons. In one important respect however, film has superior properties: the spatial resolution of CCD detectors tested so far (in terms of point spread function or modulation transfer function) are inferior to film and a great deal of our effort has been spent in designing detectors with improved spatial resolution. Various instrumental contributions to spatial resolution have been analysed and in this paper we discuss the contribution of the phosphor-fibre optics system in this measurement. We have evaluated the performance of a number of detector components and parameters, e.g. different phosphors (and a scintillator), optical coupling with lens or fibre optics with various demagnification factors, to improve the detector performance. The camera described in this paper, which is based on this analysis, uses a tapered fibre optics coupling between the phosphor and the CCD and is installed on a Philips CM12 electron microscope equipped to perform cryo-microscopy. The main use of the camera so far has been in recording electron diffraction patterns from two dimensional crystals of bacteriorhodopsin--from wild type and from different trapped states during the photocycle. As one example of the type of data obtained with the CCD camera a two dimensional Fourier projection map from the trapped O-state is also included. With faster computers, it will soon be possible to undertake this type of work on an on-line basis. Also, with improvements in detector size and resolution, CCD detectors, already ideal for diffraction, will be able to compete with film in the recording of high resolution images.

An Information-Theoretical Approach to Image Resolution Applied to Neutron Imaging Detectors Based Upon Individual Discriminator Signals

NASA Astrophysics Data System (ADS)

Clergeau, Jean-François; Ferraton, Matthieu; Guérard, Bruno; Khaplanov, Anton; Piscitelli, Francesco; Platz, Martin; Rigal, Jean-Marie; Van Esch, Patrick; Daullé, Thibault

2017-01-01

1D or 2D neutron position sensitive detectors with individual wire or strip readout using discriminators have the advantage of being able to treat several neutron impacts partially overlapping in time, hence reducing global dead time. A single neutron impact usually gives rise to several discriminator signals. In this paper, we introduce an information-theoretical definition of image resolution. Two point-like spots of neutron impacts with a given distance between them act as a source of information (each neutron hit belongs to one spot or the other), and the detector plus signal treatment is regarded as an imperfect communication channel that transmits this information. The maximal mutual information obtained from this channel as a function of the distance between the spots allows to define a calibration-independent measure of position resolution. We then apply this measure to quantify the power of position resolution of different algorithms treating these individual discriminator signals which can be implemented in firmware. The method is then applied to different detectors existing at the ILL. Center-of-gravity methods usually improve the position resolution over best-wire algorithms which are the standard way of treating these signals.

Toward single electron resolution phonon mediated ionization detectors

NASA Astrophysics Data System (ADS)

Mirabolfathi, Nader; Harris, H. Rusty; Mahapatra, Rupak; Sundqvist, Kyle; Jastram, Andrew; Serfass, Bruno; Faiez, Dana; Sadoulet, Bernard

2017-05-01

Experiments seeking to detect rare event interactions such as dark matter or coherent elastic neutrino nucleus scattering are striving for large mass detectors with very low detection threshold. Using Neganov-Luke phonon amplification effect, the Cryogenic Dark Matter Search (CDMS) experiment is reaching unprecedented RMS resolutions of ∼14 eVee. CDMSlite is currently the most sensitive experiment to WIMPs of mass ∼5 GeV/c2 but is limited in achieving higher phonon gains due to an early onset of leakage current into Ge crystals. The contact interface geometry is particularly weak for blocking hole injection from the metal, and thus a new design is demonstrated that allows high voltage bias via vacuum separated electrode. With an increased bias voltage and a×2 Luke phonon gain, world best RMS resolution of sigma ∼7 eVee for 0.25 kg (d=75 mm, h=1 cm) Ge detectors was achieved. Since the leakage current is a function of the field and the phonon gain is a function of the applied voltage, appropriately robust interface blocking material combined with thicker substrate (25 mm) will reach a resolution of ∼2.8 eVee. In order to achieve better resolution of ∼ eV, we are investigating a layer of insulator between the phonon readout surface and the semiconductor crystals.

Simultaneous dual-color fluorescence microscope: a characterization study.

PubMed

Li, Zheng; Chen, Xiaodong; Ren, Liqiang; Song, Jie; Li, Yuhua; Zheng, Bin; Liu, Hong

2013-01-01

High spatial resolution and geometric accuracy is crucial for chromosomal analysis of clinical cytogenetic applications. High resolution and rapid simultaneous acquisition of multiple fluorescent wavelengths can be achieved by utilizing concurrent imaging with multiple detectors. However, such class of microscopic systems functions differently from traditional fluorescence microscopes. To develop a practical characterization framework to assess and optimize the performance of a high resolution and dual-color fluorescence microscope designed for clinical chromosomal analysis. A dual-band microscopic imaging system utilizes a dichroic mirror, two sets of specially selected optical filters, and two detectors to simultaneously acquire two fluorescent wavelengths. The system's geometric distortion, linearity, the modulation transfer function, and the dual detectors' alignment were characterized. Experiment results show that the geometric distortion at lens periphery is less than 1%. Both fluorescent channels show linear signal responses, but there exists discrepancy between the two due to the detectors' non-uniform response ratio to different wavelengths. In terms of the spatial resolution, the two contrast transfer function curves trend agreeably with the spatial frequency. The alignment measurement allows quantitatively assessing the cameras' alignment. A result image of adjusted alignment is demonstrated to show the reduced discrepancy by using the alignment measurement method. In this paper, we present a system characterization study and its methods for a specially designed imaging system for clinical cytogenetic applications. The presented characterization methods are not only unique to this dual-color imaging system but also applicable to evaluation and optimization of other similar multi-color microscopic image systems for improving their clinical utilities for future cytogenetic applications.

Experimental determination of the lateral dose response functions of detectors to be applied in the measurement of narrow photon-beam dose profiles.

PubMed

Poppinga, D; Meyners, J; Delfs, B; Muru, A; Harder, D; Poppe, B; Looe, H K

2015-12-21

This study aims at the experimental determination of the detector-specific 1D lateral dose response function K(x) and of its associated rotational symmetric counterpart K(r) for a set of high-resolution detectors presently used in narrow-beam photon dosimetry. A combination of slit-beam, radiochromic film, and deconvolution techniques served to accomplish this task for four detectors with diameters of their sensitive volumes ranging from 1 to 2.2 mm. The particular aim of the experiment was to examine the existence of significant negative portions of some of these response functions predicted by a recent Monte-Carlo-simulation (Looe et al 2015 Phys. Med. Biol. 60 6585-607). In a 6 MV photon slit beam formed by the Siemens Artiste collimation system and a 0.5 mm wide slit between 10 cm thick lead blocks serving as the tertiary collimator, the true cross-beam dose profile D(x) at 3 cm depth in a large water phantom was measured with radiochromic film EBT3, and the detector-affected cross-beam signal profiles M(x) were recorded with a silicon diode, a synthetic diamond detector, a miniaturized scintillation detector, and a small ionization chamber. For each detector, the deconvolution of the convolution integral M(x)  =  K(x)  ∗  D(x) served to obtain its specific 1D lateral dose response function K(x), and K(r) was calculated from it. Fourier transformations and back transformations were performed using function approximations by weighted sums of Gaussian functions and their analytical transformation. The 1D lateral dose response functions K(x) of the four types of detectors and their associated rotational symmetric counterparts K(r) were obtained. Significant negative curve portions of K(x) and K(r) were observed in the case of the silicon diode and the diamond detector, confirming the Monte-Carlo-based prediction (Looe et al 2015 Phys. Med. Biol. 60 6585-607). They are typical for the perturbation of the secondary electron field by a detector with enhanced electron density compared with the surrounding water. In the cases of the scintillation detector and the small ionization chamber, the negative curve portions of K(x) practically vanish. It is planned to use the measured functions K(x) and K(r) to deconvolve clinical narrow-beam signal profiles and to correct the output factor values obtained with various high-resolution detectors.

A novel phoswich imaging detector for simultaneous beta and coincidence-gamma imaging of plant leaves.

PubMed

Wu, Heyu; Tai, Yuan-Chuan

2011-09-07

To meet the growing demand for functional imaging technology for use in studying plant biology, we are developing a novel technique that permits simultaneous imaging of escaped positrons and coincidence gammas from annihilation of positrons within an intake leaf. The multi-modality imaging system will include two planar detectors: one is a typical PET detector array and the other is a phoswich imaging detector that detects both beta and gamma. The novel phoswich detector is made of a plastic scintillator, a lutetium oxyorthosilicate (LSO) array, and a position sensitive photomultiplier tube (PS-PMT). The plastic scintillator serves as a beta detector, while the LSO array serves as a gamma detector and light guide that couples scintillation light from the plastic detector to the PMT. In our prototype, the PMT signal was fed into the Siemens QuickSilver electronics to achieve shaping and waveform sampling. Pulse-shape discrimination based on the detectors' decay times (2.1 ns for plastic and 40 ns for LSO) was used to differentiate beta and gamma events using the common PMT signals. Using our prototype phoswich detector, we simultaneously measured a beta image and gamma events (in single mode). The beta image showed a resolution of 1.6 mm full-width-at-half-maximum using F-18 line sources. Because this shows promise for plant-scale imaging, our future plans include development of a fully functional simultaneous beta-and-coincidence-gamma imager with sub-millimeter resolution imaging capability for both modalities.

Improvements in Calibration and Analysis of the CTBT-relevant Radioxenon Isotopes with High Resolution SiPIN-based Electron Detectors

NASA Astrophysics Data System (ADS)

Khrustalev, K.

2016-12-01

Current process for the calibration of the beta-gamma detectors used for radioxenon isotope measurements for CTBT purposes is laborious and time consuming. It uses a combination of point sources and gaseous sources resulting in differences between energy and resolution calibrations. The emergence of high resolution SiPIN based electron detectors allows improvements in the calibration and analysis process to be made. Thanks to high electron resolution of SiPIN detectors ( 8-9 keV@129 keV) compared to plastic scintillators ( 35 keV@129keV) there are a lot more CE peaks (from radioxenon and radon progenies) can be resolved and used for energy and resolution calibration in the energy range of the CTBT-relevant radioxenon isotopes. The long term stability of the SiPIN energy calibration allows one to significantly reduce the time of the QC measurements needed for checking the stability of the E/R calibration. The currently used second order polynomials for the E/R calibration fitting are unphysical and shall be replaced by a linear energy calibration for NaI and SiPIN, owing to high linearity and dynamic range of the modern digital DAQ systems, and resolution calibration functions shall be modified to reflect the underlying physical processes. Alternatively, one can completely abandon the use of fitting functions and use only point-values of E/R (similar to the efficiency calibration currently used) at the energies relevant for the isotopes of interest (ROI - Regions Of Interest ). Current analysis considers the detector as a set of single channel analysers, with an established set of coefficients relating the positions of ROIs with the positions of the QC peaks. The analysis of the spectra can be made more robust using peak and background fitting in the ROIs with a single free parameter (peak area) of the potential peaks from the known isotopes and a fixed E/R calibration values set.

High resolution CsI(Tl)/Si-PIN detector development for breast imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patt, B.E.; Iwanczyk, J.S.; Tull, C.R.

High resolution multi-element (8x8) imaging arrays with collimators, size matched to discrete CsI(Tl) scintillator arrays and Si-PIN photodetector arrays (PDA`s) were developed as prototypes for larger arrays for breast imaging. Photodetector pixels were each 1.5 {times} 1.5 mm{sup 2} with 0.25 mm gaps. A 16-element quadrant of the detector was evaluated with a segmented CsI(Tl) scintillator array coupled to the silicon array. The scintillator thickness of 6 mm corresponds to >85% total gamma efficiency at 140 keV. Pixel energy resolution of <8% FWHM was obtained for Tc-99m. Electronic noise was 41 e{sup {minus}} RMS corresponding to a 3% FWHM contributionmore » to the 140 keV photopeak. Detection efficiency uniformity measured with a Tc-99m flood source was 4.3% for an {approximately}10% energy photopeak window. Spatial resolution was 1.53 mm FWHM and pitch was 1.75 mm as measured from the Co-57 (122 keV) line spread function. Signal to background was 34 and contrast was 0.94. The energy resolution and spatial characteristics of the new imaging detector exceed those of other scintillator based imaging detectors. A camera based on this technology will allow: (1) Improved Compton scatter rejection; (2) Detector positioning in close proximity to the breast to increase signal to noise; (3) Improved spatial resolution; and (4) Improved efficiency compared to high resolution collimated gamma cameras for the anticipated compressed breast geometries.« less

Variable Temperature Performance of a Si(Li) Detector Stack

NASA Technical Reports Server (NTRS)

Hubbard, G. Scott; McMurray, Robert E., Jr.; Keller, R. G.; Wercinski, P. F.; Walton, J. T.; Wong, Y. K.

1994-01-01

New experimental data is presented which displays 137Cs resolution of both single Si(Li) devices and a detector stack 2 cm in height as a function of temperature (85 K greater than or equal to T greater than or equal to 245 K). We also discuss variations in photopeak shape which indicate that detector charge collection may be temperature dependent over the range of interest.

Study of electrode pattern design for a CZT-based PET detector.

PubMed

Gu, Y; Levin, C S

2014-06-07

We are developing a 1 mm resolution small animal positron emission tomography (PET) system using 3D positioning cadmium zinc telluride photon detectors comprising 40 mm × 40 mm × 5 mm crystals metalized with a cross-strip electrode pattern with a 1 mm anode strip pitch. We optimized the electrode pattern design for intrinsic sensitivity and spatial, energy and time resolution performance using a test detector comprising cathode and steering electrode strips of varying dimensions. The study found 3 and 5 mm width cathode strips locate charge-shared photon interactions near cathode strip boundaries with equal precision. 3 mm width cathode strips exhibited large time resolution variability as a function of photon interaction location between the anode and cathode planes (~26 to ~127.5 ns full width at half maximum (FWHM) for 0.5 mm and 4.2 mm depths, respectively). 5 mm width cathode strips by contrast exhibited more stable time resolution for the same interaction locations (~34 to ~83 ns FWHM), provided more linear spatial positioning in the direction orthogonal to the electrode planes, and as much as 68.4% improvement in photon sensitivity over the 3 mm wide cathode strips. The results were understood by analyzing the cathode strips' weighting functions, which indicated a stronger 'small pixel' effect in the 3 mm wide cathode strips. Photon sensitivity and anode energy resolution were seen to improve with decreasing steering electrode bias from 0 to -80 V w.r.t. the anode potential. A slight improvement in energy resolution was seen for wider steering electrode strips (400 versus 100 µm) for charge-shared photon interactions. Although this study successfully focused on electrode pattern features for PET performance, the results are generally applicable to semiconductor photon detectors employing cross-trip electrode patterns.

Study of electrode pattern design for a CZT-based PET detector

PubMed Central

Gu, Y; Levin, C S

2014-01-01

We are developing a 1 mm resolution small animal positron emission tomography (PET) system using 3-D positioning Cadmium Zinc Telluride (CZT) photon detectors comprising 40 mm × 40 mm × 5 mm crystals metalized with a cross-strip electrode pattern with a 1 mm anode strip pitch. We optimized the electrode pattern design for intrinsic sensitivity and spatial, energy and time resolution performance using a test detector comprising cathode and steering electrode strips of varying dimensions. The study found 3 mm and 5 mm width cathode strips locate charge-shared photon interactions near cathode strip boundaries with equal precision. 3 mm width cathode strips exhibited large time resolution variability as a function of photon interaction location between the anode and cathode planes (~26 ns to ~127.5 ns FWHM for 0.5 mm and 4.2 mm depths, respectively). 5 mm width cathode strips by contrast exhibited more stable time resolution for the same interaction locations (~34 ns to ~83 ns FWHM), provided more linear spatial positioning in the direction orthogonal to the electrode planes, and as much as 68.4% improvement in photon sensitivity over the 3 mm wide cathode strips. The results were understood by analyzing the cathode strips’ weighting functions, which indicated a stronger “small pixel” effect in the 3 mm wide cathode strips. Photon sensitivity and anode energy resolution were seen to improve with decreasing steering electrode bias from 0 V to −80 V w.r.t the anode potential. A slight improvement in energy resolution was seen for wider steering electrode strips (400 μm vs. 100 μm) for charge-shared photon interactions. Although this study successfully focused on electrode pattern features for PET performance, the results are generally applicable to semiconductor photon detectors employing cross-trip electrode patterns. PMID:24786208

Analytical Calculation of the Lower Bound on Timing Resolution for PET Scintillation Detectors Comprising High-Aspect-Ratio Crystal Elements

PubMed Central

Cates, Joshua W.; Vinke, Ruud; Levin, Craig S.

2015-01-01

Excellent timing resolution is required to enhance the signal-to-noise ratio (SNR) gain available from the incorporation of time-of-flight (ToF) information in image reconstruction for positron emission tomography (PET). As the detector’s timing resolution improves, so does SNR, reconstructed image quality, and accuracy. This directly impacts the challenging detection and quantification tasks in the clinic. The recognition of these benefits has spurred efforts within the molecular imaging community to determine to what extent the timing resolution of scintillation detectors can be improved and develop near-term solutions for advancing ToF-PET. Presented in this work, is a method for calculating the Cramér-Rao lower bound (CRLB) on timing resolution for scintillation detectors with long crystal elements, where the influence of the variation in optical path length of scintillation light on achievable timing resolution is non-negligible. The presented formalism incorporates an accurate, analytical probability density function (PDF) of optical transit time within the crystal to obtain a purely mathematical expression of the CRLB with high-aspect-ratio (HAR) scintillation detectors. This approach enables the statistical limit on timing resolution performance to be analytically expressed for clinically-relevant PET scintillation detectors without requiring Monte Carlo simulation-generated photon transport time distributions. The analytically calculated optical transport PDF was compared with detailed light transport simulations, and excellent agreement was found between the two. The coincidence timing resolution (CTR) between two 3×3×20 mm3 LYSO:Ce crystals coupled to analogue SiPMs was experimentally measured to be 162±1 ps FWHM, approaching the analytically calculated lower bound within 6.5%. PMID:26083559

Analytical calculation of the lower bound on timing resolution for PET scintillation detectors comprising high-aspect-ratio crystal elements

NASA Astrophysics Data System (ADS)

Cates, Joshua W.; Vinke, Ruud; Levin, Craig S.

2015-07-01

Excellent timing resolution is required to enhance the signal-to-noise ratio (SNR) gain available from the incorporation of time-of-flight (ToF) information in image reconstruction for positron emission tomography (PET). As the detector’s timing resolution improves, so does SNR, reconstructed image quality, and accuracy. This directly impacts the challenging detection and quantification tasks in the clinic. The recognition of these benefits has spurred efforts within the molecular imaging community to determine to what extent the timing resolution of scintillation detectors can be improved and develop near-term solutions for advancing ToF-PET. Presented in this work, is a method for calculating the Cramér-Rao lower bound (CRLB) on timing resolution for scintillation detectors with long crystal elements, where the influence of the variation in optical path length of scintillation light on achievable timing resolution is non-negligible. The presented formalism incorporates an accurate, analytical probability density function (PDF) of optical transit time within the crystal to obtain a purely mathematical expression of the CRLB with high-aspect-ratio (HAR) scintillation detectors. This approach enables the statistical limit on timing resolution performance to be analytically expressed for clinically-relevant PET scintillation detectors without requiring Monte Carlo simulation-generated photon transport time distributions. The analytically calculated optical transport PDF was compared with detailed light transport simulations, and excellent agreement was found between the two. The coincidence timing resolution (CTR) between two 3× 3× 20 mm3 LYSO:Ce crystals coupled to analogue SiPMs was experimentally measured to be 162+/- 1 ps FWHM, approaching the analytically calculated lower bound within 6.5%.

Tutorial on X-ray photon counting detector characterization.

PubMed

Ren, Liqiang; Zheng, Bin; Liu, Hong

2018-01-01

Recent advances in photon counting detection technology have led to significant research interest in X-ray imaging. As a tutorial level review, this paper covers a wide range of aspects related to X-ray photon counting detector characterization. The tutorial begins with a detailed description of the working principle and operating modes of a pixelated X-ray photon counting detector with basic architecture and detection mechanism. Currently available methods and techniques for charactering major aspects including energy response, noise floor, energy resolution, count rate performance (detector efficiency), and charge sharing effect of photon counting detectors are comprehensively reviewed. Other characterization aspects such as point spread function (PSF), line spread function (LSF), contrast transfer function (CTF), modulation transfer function (MTF), noise power spectrum (NPS), detective quantum efficiency (DQE), bias voltage, radiation damage, and polarization effect are also remarked. A cadmium telluride (CdTe) pixelated photon counting detector is employed for part of the characterization demonstration and the results are presented. This review can serve as a tutorial for X-ray imaging researchers and investigators to understand, operate, characterize, and optimize photon counting detectors for a variety of applications.

Interferometric direction finding with a metamaterial detector

NASA Astrophysics Data System (ADS)

Venkatesh, Suresh; Shrekenhamer, David; Xu, Wangren; Sonkusale, Sameer; Padilla, Willie; Schurig, David

2013-12-01

We present measurements and analysis demonstrating useful direction finding of sources in the S band (2-4 GHz) using a metamaterial detector. An augmented metamaterial absorber that supports magnitude and phase measurement of the incident electric field, within each unit cell, is described. The metamaterial is implemented in a commercial printed circuit board process with off-board back-end electronics. We also discuss on-board back-end implementation strategies. Direction finding performance is analyzed for the fabricated metamaterial detector using simulated data and the standard algorithm, MUtiple SIgnal Classification. The performance of this complete system is characterized by its angular resolution as a function of radiation density at the detector. Sources with power outputs typical of mobile communication devices can be resolved at kilometer distances with sub-degree resolution and high frame rates.

Scintillator Detector Development at Central Michigan University

NASA Astrophysics Data System (ADS)

McClain, David; Estrade, Alfredo; Neupane, Shree

2017-09-01

Experimental nuclear physics relies both on the accuracy and precision of the instruments for radiation detection used in experimental setups. At Central Michigan University we have setup a lab to work with scintillator detectors for radioactive ion beam experiments, using a Picosecond Laser and radioactive sources for testing. We have tested the resolution for prototypes of large area scintillators that could be used for fast timing measurements in the focal plane of spectrometers, such as the future High Rigidity Spectrometer at the Facility for Rare Isotope Beams (FRIB). We measured the resolution as a function of the length of the detector, and also the position of the beam along the scintillator. We have also designed a scintillating detector to veto light ion background in beta-decay experiments with the Advanced Implantation Detector Array (AIDA) at RIKEN in Japan. We tested different configurations of Silicon Photomultipliers and scintillating fiber optics to find the best detection efficiency.

A polychromator-type near-infrared spectrometer with a high-sensitivity and high-resolution photodiode array detector for pharmaceutical process monitoring on the millisecond time scale.

PubMed

Murayama, Kodai; Genkawa, Takuma; Ishikawa, Daitaro; Komiyama, Makoto; Ozaki, Yukihiro

2013-02-01

In the fine chemicals industry, particularly in the pharmaceutical industry, advanced sensing technologies have recently begun being incorporated into the process line in order to improve safety and quality in accordance with process analytical technology. For estimating the quality of powders without preparation during drug formulation, near-infrared (NIR) spectroscopy has been considered the most promising sensing approach. In this study, we have developed a compact polychromator-type NIR spectrometer equipped with a photodiode (PD) array detector. This detector is consisting of 640 InGaAs-PD elements with 20-μm pitch. Some high-specification spectrometers, which use InGaAs-PD with 512 elements, have a wavelength resolution of about 1.56 nm when covering 900-1700 nm range. On the other hand, the newly developed detector, having the PD with one of the world's highest density, enables wavelength resolution of below 1.25 nm. Moreover, thanks to the combination with a highly integrated charge amplifier array circuit, measurement speed of the detector is higher by two orders than that of existing PD array detectors. The developed spectrometer is small (120 mm × 220 mm × 200 mm) and light (6 kg), and it contains various key devices including the high-density and high-sensitivity PD array detector, NIR technology, and spectroscopy technology for a spectroscopic analyzer that has the required detection mechanism and high sensitivity for powder measurement, as well as a high-speed measuring function for blenders. Moreover, we have evaluated the characteristics of the developed NIR spectrometer, and the measurement of powder samples confirmed that it has high functionality.

A BGO detector for Positron Emission Profiling in catalysts

NASA Astrophysics Data System (ADS)

Mangnus, A. V. G.; van Ijzendoorn, L. J.; de Goeij, J. J. M.; Cunningham, R. H.; van Santen, R. A.; de Voigt, M. J. A.

1995-05-01

As part of a project to study the reaction kinetics in catalysts, a detector system has been designed and built. The detector will measure in one dimension the activity distribution of positron emitters in catalyst reactors under operational conditions as a function of time. The detector consists of two arrays of ten BGO crystals each and has the flexibility to measure with high sensitivity the activity profile in various reactor sizes; the position resolution that can be reached is 3 mm.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barbosa, F.; Somov, A. S.; Somov, S. V.

Here, silicon photomultipliers (SiPMs) are used in detectors of the GlueX experiment devoted to studying the nature of confinement. These detectors are operable at counting rates as high as 2 MHz with a time resolution (FWHM) of approximately 0.3 ns and a number of excited pixels of up to 10 4. For SiPMs that operate under these conditions, the measured dependences of the recovery time and the time resolution are presented as functions of the number of excited pixels and the excitation frequency. Using a picosecond laser, the time resolution has been measured for an array of 4 × 4more » SiPMs, which was specially developed for the experiment.« less

One dimensional spatial resolution optimization on a hybrid low field MRI-gamma detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agulles-Pedrós, L., E-mail: lagullesp@unal.edu.co; Abril, A., E-mail: ajabrilf@unal.edu.co

Hybrid systems like Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI) and MRI/gamma camera, offer advantages combining the resolution and contrast capability of MRI with the better contrast and functional information of nuclear medicine techniques. However, the radiation detectors are expensive and need an electronic set-up, which can interfere with the MRI acquisition process or viceversa. In order to improve these drawbacks, in this work it is presented the design of a low field NMR system made up of permanent magnets compatible with a gamma radiation detector based on gel dosimetry. The design is performed using the software FEMM for estimation ofmore » the magnetic field, and GEANT4 for the physical process involved in radiation detection and effect of magnetic field. The homogeneity in magnetic field is achieved with an array of NbFeB magnets in a linear configuration with a separation between the magnets, minimizing the effect of Compton back scattering compared with a no-spacing linear configuration. The final magnetic field in the homogeneous zone is ca. 100 mT. In this hybrid proposal, although the gel detector do not have spatial resolution per se, it is possible to obtain a dose profile (1D image) as a function of the position by using a collimator array. As a result, the gamma detector system described allows a complete integrated radiation detector within the low field NMR (lfNMR) system. Finally we present the better configuration for the hybrid system considering the collimator parameters such as height, thickness and distance.« less

Status of the Micro-X Sounding Rocket X-Ray Spectrometer

NASA Technical Reports Server (NTRS)

Goldfinger, D. C.; Adams, J. S.; Baker, R.; Bandler, S. R.; Danowski, M. E.; Doriese, W. B.; Eckart, M. E.; Figueroa-Feliciano, E.; Hilton, G. C.; Hubbard, A. J. F.;

Detailed Studies of Pixelated CZT Detectors Grown with the Modified Horizontal Bridgman Method

NASA Technical Reports Server (NTRS)

Jung, I.; Krawczynski, H.; Burger, A.; Guo, M.; Groza, M.

2007-01-01

The detector material Cadmium Zinc Telluride (CZT) achieves excellent spatial resolution and good energy resolution over a broad energy range, several keV up to some MeV. Presently, there are two main methods to grow CZT crystals, the Modified High-Pressure Bridgman (MHB) and the High-Pressure Bridgman (HPB) process. The study presented in this paper is based on MHB CZT substrates from the company Orbotech Medical Solutions Ltd. [Orbotech Medical Solutions Ltd., 10 Plaut St., Park Rabin, P.O. Box 2489, Rehovot, Israel, 76124]. Former studies have shown that high-work-function materials on the cathode side reduce the leakage current and, therefore, improve the energy resolution at lower energies. None of the studies have emphasized on the anode contact material. Therefore, we present in this paper the result of a detailed study in which for the first time the cathode material was kept constant and the anode material was varied. We used four different anode materials: Indium, Titanium, Chromium and Gold, metals with work-functions between 4.1 eV and 5.1 eV. The detector size was 2.0 x 2.0 x 0.5 cu cm with 8 x 8 pixels and a pitch of 2.46 mm. The best performance was achieved with the low-work-function materials Indium and Titanium with energy resolutions of 2.0 keV (at 59 keV) and 1.9 keV (at 122 keV) for Titanium and 2.1 keV (at 59 keV) and 2.9 keV (at 122 keV) for Indium. Taking into account the large pixel pitch of 2.46 mm, these resolutions are very competitive in comparison to those achieved with detectors made of material produced with the more expensive conventional HPB method. We present a detailed comparison of our detector response with 3D simulations. The latter comparisons allow us to determine the mobility-lifetime-products (mu tau-products) for electrons and holes. Finally, we evaluated the temperature dependency of the detector performance and ls-products. For many applications temperature dependence is important, therefore, we extended the scope of our study to temperatures as low as -30 C. There are two important results. The breakdown voltage increases with decreasing temperature, and electron mobility-lifetime-product decreases by about 30% over a range from 20 C to -30 C. The latter effect causes the energy resolution to deteriorate, but the concomitantly increasing breakdown voltage makes it possible to increase the applied bias voltage and restore the full performance

Artifacts in Digital Coincidence Timing

PubMed Central

Moses, W. W.; Peng, Q.

2014-01-01

Digital methods are becoming increasingly popular for measuring time differences, and are the de facto standard in PET cameras. These methods usually include a master system clock and a (digital) arrival time estimate for each detector that is obtained by comparing the detector output signal to some reference portion of this clock (such as the rising edge). Time differences between detector signals are then obtained by subtracting the digitized estimates from a detector pair. A number of different methods can be used to generate the digitized arrival time of the detector output, such as sending a discriminator output into a time to digital converter (TDC) or digitizing the waveform and applying a more sophisticated algorithm to extract a timing estimator. All measurement methods are subject to error, and one generally wants to minimize these errors and so optimize the timing resolution. A common method for optimizing timing methods is to measure the coincidence timing resolution between two timing signals whose time difference should be constant (such as detecting gammas from positron annihilation) and selecting the method that minimizes the width of the distribution (i.e., the timing resolution). Unfortunately, a common form of error (a nonlinear transfer function) leads to artifacts that artificially narrow this resolution, which can lead to erroneous selection of the “optimal” method. The purpose of this note is to demonstrate the origin of this artifact and suggest that caution should be used when optimizing time digitization systems solely on timing resolution minimization. PMID:25321885

Artifacts in digital coincidence timing

DOE PAGES

Moses, W. W.; Peng, Q.

2014-10-16

Digital methods are becoming increasingly popular for measuring time differences, and are the de facto standard in PET cameras. These methods usually include a master system clock and a (digital) arrival time estimate for each detector that is obtained by comparing the detector output signal to some reference portion of this clock (such as the rising edge). Time differences between detector signals are then obtained by subtracting the digitized estimates from a detector pair. A number of different methods can be used to generate the digitized arrival time of the detector output, such as sending a discriminator output into amore » time to digital converter (TDC) or digitizing the waveform and applying a more sophisticated algorithm to extract a timing estimator.All measurement methods are subject to error, and one generally wants to minimize these errors and so optimize the timing resolution. A common method for optimizing timing methods is to measure the coincidence timing resolution between two timing signals whose time difference should be constant (such as detecting gammas from positron annihilation) and selecting the method that minimizes the width of the distribution (i.e. the timing resolution). Unfortunately, a common form of error (a nonlinear transfer function) leads to artifacts that artificially narrow this resolution, which can lead to erroneous selection of the 'optimal' method. In conclusion, the purpose of this note is to demonstrate the origin of this artifact and suggest that caution should be used when optimizing time digitization systems solely on timing resolution minimization.« less

Artifacts in digital coincidence timing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moses, W. W.; Peng, Q.

Digital methods are becoming increasingly popular for measuring time differences, and are the de facto standard in PET cameras. These methods usually include a master system clock and a (digital) arrival time estimate for each detector that is obtained by comparing the detector output signal to some reference portion of this clock (such as the rising edge). Time differences between detector signals are then obtained by subtracting the digitized estimates from a detector pair. A number of different methods can be used to generate the digitized arrival time of the detector output, such as sending a discriminator output into amore » time to digital converter (TDC) or digitizing the waveform and applying a more sophisticated algorithm to extract a timing estimator.All measurement methods are subject to error, and one generally wants to minimize these errors and so optimize the timing resolution. A common method for optimizing timing methods is to measure the coincidence timing resolution between two timing signals whose time difference should be constant (such as detecting gammas from positron annihilation) and selecting the method that minimizes the width of the distribution (i.e. the timing resolution). Unfortunately, a common form of error (a nonlinear transfer function) leads to artifacts that artificially narrow this resolution, which can lead to erroneous selection of the 'optimal' method. In conclusion, the purpose of this note is to demonstrate the origin of this artifact and suggest that caution should be used when optimizing time digitization systems solely on timing resolution minimization.« less

Simultaneous multi-headed imager geometry calibration method

DOEpatents

Tran, Vi-Hoa [Newport News, VA; Meikle, Steven Richard [Penshurst, AU; Smith, Mark Frederick [Yorktown, VA

2008-02-19

A method for calibrating multi-headed high sensitivity and high spatial resolution dynamic imaging systems, especially those useful in the acquisition of tomographic images of small animals. The method of the present invention comprises: simultaneously calibrating two or more detectors to the same coordinate system; and functionally correcting for unwanted detector movement due to gantry flexing.

The Cadmium Zinc Telluride Imager on AstroSat

NASA Astrophysics Data System (ADS)

Bhalerao, V.; Bhattacharya, D.; Vibhute, A.; Pawar, P.; Rao, A. R.; Hingar, M. K.; Khanna, Rakesh; Kutty, A. P. K.; Malkar, J. P.; Patil, M. H.; Arora, Y. K.; Sinha, S.; Priya, P.; Samuel, Essy; Sreekumar, S.; Vinod, P.; Mithun, N. P. S.; Vadawale, S. V.; Vagshette, N.; Navalgund, K. H.; Sarma, K. S.; Pandiyan, R.; Seetha, S.; Subbarao, K.

2017-06-01

The Cadmium Zinc Telluride Imager (CZTI) is a high energy, wide-field imaging instrument on AstroSat. CZTI's namesake Cadmium Zinc Telluride detectors cover an energy range from 20 keV to >200 keV, with 11% energy resolution at 60 keV. The coded aperture mask attains an angular resolution of 17^' over a 4.6° × 4.6° (FWHM) field-of-view. CZTI functions as an open detector above 100 keV, continuously sensitive to GRBs and other transients in about 30% of the sky. The pixellated detectors are sensitive to polarization above ˜ 100 keV, with exciting possibilities for polarization studies of transients and bright persistent sources. In this paper, we provide details of the complete CZTI instrument, detectors, coded aperture mask, mechanical and electronic configuration, as well as data and products.

A micron resolution optical scanner for characterization of silicon detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shukla, R. A.; Dugad, S. R., E-mail: dugad@cern.ch; Gopal, A. V.

2014-02-15

The emergence of high position resolution (∼10 μm) silicon detectors in recent times have highlighted the urgent need for the development of new automated optical scanners of micron level resolution suited for characterizing microscopic features of these detectors. More specifically, for the newly developed silicon photo-multipliers (SiPM) that are compact, possessing excellent photon detection efficiency with gain comparable to photo-multiplier tube. In a short time, since their invention the SiPMs are already being widely used in several high-energy physics and astrophysics experiments as the photon readout element. The SiPM is a high quantum efficiency, multi-pixel photon counting detector with fastmore » timing and high gain. The presence of a wide variety of photo sensitive silicon detectors with high spatial resolution requires their performance evaluation to be carried out by photon beams of very compact spot size. We have designed a high resolution optical scanner that provides a monochromatic focused beam on a target plane. The transverse size of the beam was measured by the knife-edge method to be 1.7 μm at 1 − σ level. Since the beam size was an order of magnitude smaller than the typical feature size of silicon detectors, this optical scanner can be used for selective excitation of these detectors. The design and operational details of the optical scanner, high precision programmed movement of target plane (0.1 μm) integrated with general purpose data acquisition system developed for recording static and transient response photo sensitive silicon detector are reported in this paper. Entire functionality of scanner is validated by using it for selective excitation of individual pixels in a SiPM and identifying response of active and dead regions within SiPM. Results from these studies are presented in this paper.« less

Localization accuracy of compact binary coalescences detected by the third-generation gravitational-wave detectors and implication for cosmology

NASA Astrophysics Data System (ADS)

Zhao, Wen; Wen, Linqing

2018-03-01

We use the Fisher information matrix to investigate the angular resolution and luminosity distance uncertainty for coalescing binary neutron stars (BNSs) and neutron star-black hole binaries (NSBHs) detected by the third-generation (3G) gravitational-wave (GW) detectors. Our study focuses on an individual 3G detector and a network of up to four 3G detectors at different locations including the United States, Europe, China, and Australia for the proposed Einstein Telescope (ET) and Cosmic Explorer (CE) detectors. In particular, we examine the effect of the Earth's rotation, as GW signals from BNS and low-mass NSBH systems could be hours long for 3G detectors. In this case, an individual detector can be effectively treated as a detector network with long baselines formed by the trajectory of the detector as it rotates with the Earth. Therefore, a single detector or two-detector networks could also be used to localize the GW sources effectively. We find that a time-dependent antenna beam-pattern function can help better localize BNS and NSBH sources, especially edge-on ones. The medium angular resolution for one ET-D detector is around 150 deg2 for BNSs at a redshift of z =0.1 , which improves rapidly with a decreasing low-frequency cutoff flow in sensitivity. The medium angular resolution for a network of two CE detectors in the United States and Europe, respectively, is around 20 deg2 at z =0.2 for the simulated BNS and NSBH samples. While for a network of two ET-D detectors, the similar angular resolution can be achieved at a much higher redshift of z =0.5 . The angular resolution of a network of three detectors is mainly determined by the baselines between detectors regardless of the CE or ET detector type. The medium angular resolution of BNS for a network of three detectors of the ET-D or CE type in the United States, Europe, and Australia is around 10 deg2 at z =2 . We discuss the implications of our results for multimessenger astronomy and, in particular, for using GW sources as independent tools to constrain the Hubble constant H0, the deceleration parameter q0, and the equation-of-state (EoS) of dark energy. We find that, in general, if 10 BNSs or NSBHs at z =0.1 with known redshifts are detected by 3G networks consisting of two ET-like detectors, H0 can be measured with an accuracy of 0.9%. If 1000 face-on BNSs at z <2 are detected with known redshifts, we are able to achieve Δ q0=0.002 for the deceleration parameter, or Δ w0=0.03 and Δ wa=0.2 for EoS of dark energy, respectively.

Assessment of a New High-Performance Small-Animal X-Ray Tomograph

NASA Astrophysics Data System (ADS)

Vaquero, J. J.; Redondo, S.; Lage, E.; Abella, M.; Sisniega, A.; Tapias, G.; Montenegro, M. L. Soto; Desco, M.

2008-06-01

We have developed a new X-ray cone-beam tomograph for in vivo small-animal imaging using a flat panel detector (CMOS technology with a microcolumnar CsI scintillator plate) and a microfocus X-ray source. The geometrical configuration was designed to achieve a spatial resolution of about 12 lpmm with a field of view appropriate for laboratory rodents. In order to achieve high performance with regard to per-animal screening time and cost, the acquisition software takes advantage of the highest frame rate of the detector and performs on-the-fly corrections on the detector raw data. These corrections include geometrical misalignments, sensor non-uniformities, and defective elements. The resulting image is then converted to attenuation values. We measured detector modulation transfer function (MTF), detector stability, system resolution, quality of the reconstructed tomographic images and radiated dose. The system resolution was measured following the standard test method ASTM E 1695 -95. For image quality evaluation, we assessed signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) as a function of the radiated dose. Dose studies for different imaging protocols were performed by introducing TLD dosimeters in representative organs of euthanized laboratory rats. Noise figure, measured as standard deviation, was 50 HU for a dose of 10 cGy. Effective dose with standard research protocols is below 200 mGy, confirming that the system is appropriate for in vivo imaging. Maximum spatial resolution achieved was better than 50 micron. Our experimental results obtained with image quality phantoms as well as with in-vivo studies show that the proposed configuration based on a CMOS flat panel detector and a small micro-focus X-ray tube leads to a compact design that provides good image quality and low radiated dose, and it could be used as an add-on for existing PET or SPECT scanners.

Calibration of high-dynamic-range, finite-resolution x-ray pulse-height spectrometers for extracting electron energy distribution data from the PFRC-2 device

NASA Astrophysics Data System (ADS)

Swanson, C.; Jandovitz, P.; Cohen, S. A.

2017-10-01

Knowledge of the full x-ray energy distribution function (XEDF) emitted from a plasma over a large dynamic range of energies can yield valuable insights about the electron energy distribution function (EEDF) of that plasma and the dynamic processes that create them. X-ray pulse height detectors such as Amptek's X-123 Fast SDD with Silicon Nitride window can detect x-rays in the range of 200eV to 100s of keV. However, extracting EEDF from this measurement requires precise knowledge of the detector's response function. This response function, including the energy scale calibration, the window transmission function, and the resolution function, can be measured directly. We describe measurements of this function from x-rays from a mono-energetic electron beam in a purpose-built gas-target x-ray tube. Large-Z effects such as line radiation, nuclear charge screening, and polarizational Bremsstrahlung are discussed.

Testing of Front End Electronics for 10ps Time of Flight Detectors

NASA Astrophysics Data System (ADS)

Kimball, Matthew; EIC PID Consortium Collaboration

2016-09-01

To fully achieve the physics goals of the future Electron Ion Collider (EIC), continued development of the detectors involved is needed. One area of research involves improving the timing resolution of Time of Flight (ToF) detectors from 100ps to 10ps. When the timing resolution of these ToF detectors is improved, better particle identification can be achieved. In addition, as ToF detectors are being constructed with ever improving timing resolution, the need to improve the high speed performance of the fast electronics used in their front-end electronics (FEE) increases. A series of careful measurements has been performed to investigate the performance and efficiency of each element in the FEE chain. The focus of these tests lies on the amplitude transmission efficiency of the high speed signals as a function of frequency, also known as the bandwidth. The components tested include balanced to unbalanced (balun) boards, signal pre-amps, and waveform digitizers. These tests were performed on individual components and with all elements connected over a frequency range of 1MHz to 1GHz. The results of these tests will be presented. This research was supported by US DOE MENP Grant DE-FG02-03ER41243.

Processing of CT sinograms acquired using a VRX detector

NASA Astrophysics Data System (ADS)

Jordan, Lawrence M.; DiBianca, Frank A.; Zou, Ping; Laughter, Joseph S.; Zeman, Herbert D.

2000-04-01

A 'variable resolution x-ray detector' (VRX) capable of resolving beyond 100 cycles/main a single dimension has been proposed by DiBianca, et al. The use of detectors of this design for computed-tomography (CT) imaging requires novel preprocessing of data to correct for the detector's non- uniform imaging characteristics over its range of view. This paper describes algorithms developed specifically to adjust VRX data for varying magnification, source-to-detector range and beam obliquity and to sharpen reconstructions by deconvolving the ray impulse function. The preprocessing also incorporates nonlinear interpolation of VRX raw data into canonical CT sinogram formats.

Energy calibration of organic scintillation detectors for. gamma. rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gu Jiahui; Xiao Genlai; Liu Jingyi

1988-10-01

An experimental method of calibrating organic detectors is described. A NaI(T1) detector has some advantages of high detection efficiency, good energy resolution, and definite position of the back-scattering peak. The precise position of the Compton edge can be determined by coincidence measurement between the pulse of an organic scintillation detector and the pulse of the back-scattering peak from NaI(T1) detector. It can be used to calibrate various sizes and shapes of organic scintillation detectors simply and reliably. The home-made plastic and organic liquid scintillation detectors are calibrated and positions of the Compton edge as a function of ..gamma..-ray energies aremore » obtained.« less

Recent Development of TlBr Gamma-Ray Detectors

NASA Astrophysics Data System (ADS)

Hitomi, Keitaro; Tada, Tsutomu; Kim, Seong-Yun; Wu, Yan; Tanaka, Tomonobu; Shoji, Tadayoshi; Yamazaki, Hiromichi; Ishii, Keizo

2011-08-01

Planar detectors, strip detectors, and double-sided strip detectors were fabricated from TlBr crystals grown by the traveling molten zone method using zone-purified material. The detector performance including the leakage current, energy resolutions, and timing performance were evaluated in order to assess the capability of the detectors for PET and SPECT applications. The TlBr detectors exhibited excellent spectroscopic performance at room temperature. An energy resolution of 3.4% FWHM at 511 keV was obtained from a TlBr planar detector 1 mm thick. A TlBr strip detector 1 mm thick with four anode strip electrodes exhibited almost uniform detector performance over the strips with the average energy resolution of 4.4% FWHM at 511 keV. A TlBr double-sided strip detector exhibited an energy resolution of 6.3% FWHM for 122 keV gamma-rays. Coincidence timing spectra between a TlBr planar detector and a BaF2 scintillation detector were recorded at room temperature. Timing resolutions of 14 ns and 24 ns were obtained from TlBr detectors 0.5 mm and 1 mm thick, respectively. By cooling the detector to 0° C, an improved timing resolution of 12 ns was obtained from a TlBr detector 1 mm thick.

High resolution gamma detector for small-animal positron emission tomography

NASA Astrophysics Data System (ADS)

Ling, Tao

In this study, the performance of continuous miniature crystal element (cMiCE) detectors with LYSO crystals of different thickness were investigated. Potential designs of a cMiCE small animal positron emission tomography scanner were also evaluated by an analytical simulation approach. The cMiCE detector was proposed as a high sensitivity, low cost alternative to the prevailing discrete crystal detectors. A statistics based positioning (SBP) algorithm was developed to solve the scintillation position estimation problem and proved to be successful on a cMiCE detector with a 4 mm thick crystal. By assuming a Gaussian distribution, the distributions of the photomultiplier signals could be characterized by mean and variance, which are functions of scintillation position. After calibrating the detector on a grid of locations, a 2D table of the mean and variance can be built. The SBP algorithm searches the tables to find the location that maximizes the likelihood between the mean and variance of known positions and the incoming scintillation event. In this work, the performance of the SBP algorithm on cMiCE detectors with thicker crystals (6 and 8 mm) was studied. The stopping power of a cMiCE detector is 40% and 49% for 6 and 8 mm thick crystals respectively. The intrinsic spatial resolution is 1.2 mm and 1.4 mm FWHM for the center and corner sections of a 6 mm thick crystal detector, and 1.3 mm and 1.6 mm for center and corner of an 8 mm thick crystal detector. These results demonstrate that the cMiCE detector is a promising candidate for high resolution, high sensitivity PET applications. A maximum-likelihood (ML) clustering method was developed to empirically separate the experimental data set into two to four subgroups according to the depth-of-interaction of the detected photons. This method enabled us to build 2-DOI lookup tables (LUT) (mean and variance lookup tables for front group and back group). Using the 2-DOI SBP LUTs, the scintillation position and DOI could be estimated at the same time. The experimental measured misclassification rate for the 8 mm thick crystal detector is approximately 25%. The ML clustering method also provided a better fit to the distributions of the experimental signals, especially for the skewed ones. It therefore led to a significant improvement in the intrinsic spatial resolution in the corner region of the detector. In order to eliminate the effort in calibrating a cMiCE detector, a parametric positioning method was studied. Gaussian, Cauchy, and parametric models for the light distribution inside the crystal were tested. From the diagnosis of the sum of squared residues and the goodness of fit to the experimental data, the parametric model was found to be the best fit to the light distribution. It was also the best performer in terms of intrinsic spatial resolution and DOI resolution. Using the parametric model, the intrinsic spatial resolution is 1.1 mm and 1.3 mm FWHM for the center and corner regions of the 8 mm thick crystal detector respectively. The DOI resolution is 3.2 mm FWHM. Another variation of the SBP algorithm was tried to reduce the number of readouts need to be digitized. Several themes of different trade-offs between the readout number and spatial resolution were tested. The results show that excluding the PMT channels with less 1% of the total signal or digitizing only the nearest 21 channels around the channel with the maximum signal are the best choices, while the intrinsic spatial resolution is not compromised. An analytical simulation approach was developed to investigate how the choice of cMiCE detectors affect image figures of merit for mouse-imaging cMICE PET scanners. For a high resolution imaging system, important physical effects that impact image quality are positron range, detector point-spread function and coincident photon count levels (i.e., statistical noise). Modeling of these effects was included in an analytical simulation that generated multiple realizations of sinograms with varying levels of each effect. To evaluate image quality with respect to quantitation and detection task performance, four different figures of merit were measured: (1) root mean square error; (2) a region of interest SNR (SNRROI); (3) non-prewhitening matched filter SNR (SNRNPW); and (4) recovery coefficient. The results indicate that positron range and non-stationary detector point-spread response effects cause significant reductions of quantitation (SNRROI) and detection (SNRNPW) accuracy for small regions, e.g., a 0.01 cc sphere. A cMiCE detector with 6 mm thick crystal is better for quantitation, while the one with 8 mm thick crystal is better for detection. DOI capability makes a major impact on the FOMs. cMiCE detector with 8 mm thick crystal + 2-DOI capability proved to be the best candidate for both quantitation and detection.

High-resolution extremity cone-beam CT with a CMOS detector: Task-based optimization of scintillator thickness.

PubMed

Cao, Q; Brehler, M; Sisniega, A; Stayman, J W; Yorkston, J; Siewerdsen, J H; Zbijewski, W

2017-03-01

CMOS x-ray detectors offer small pixel sizes and low electronic noise that may support the development of novel high-resolution imaging applications of cone-beam CT (CBCT). We investigate the effects of CsI scintillator thickness on the performance of CMOS detectors in high resolution imaging tasks, in particular in quantitative imaging of bone microstructure in extremity CBCT. A scintillator thickness-dependent cascaded systems model of CMOS x-ray detectors was developed. Detectability in low-, high- and ultra-high resolution imaging tasks (Gaussian with FWHM of ~250 μ m, ~80 μ m and ~40 μ m, respectively) was studied as a function of scintillator thickness using the theoretical model. Experimental studies were performed on a CBCT test bench equipped with DALSA Xineos3030 CMOS detectors (99 μ m pixels) with CsI scintillator thicknesses of 400 μ m and 700 μ m, and a 0.3 FS compact rotating anode x-ray source. The evaluation involved a radiographic resolution gauge (0.6-5.0 lp/mm), a 127 μm tungsten wire for assessment of 3D resolution, a contrast phantom with tissue-mimicking inserts, and an excised fragment of human tibia for visual assessment of fine trabecular detail. Experimental studies show ~35% improvement in the frequency of 50% MTF modulation when using the 400 μ m scintillator compared to the standard nominal CsI thickness of 700 μ m. Even though the high-frequency DQE of the two detectors is comparable, theoretical studies show a 14% to 28% increase in detectability index ( d' 2 ) of high- and ultrahigh resolution tasks, respectively, for the detector with 400 μ m CsI compared to 700 μ m CsI. Experiments confirm the theoretical findings, showing improvements with the adoption of 400 μ m panel in the visibility of the radiographic pattern (2× improvement in peak-to-through distance at 4.6 lp/mm) and a 12.5% decrease in the FWHM of the tungsten wire. Reconstructions of the tibial plateau reveal enhanced visibility of trabecular structures with the CMOS detector with 400 μ m scinitllator. Applications on CMOS detectors in high resolution CBCT imaging of trabecular bone will benefit from using a thinner scintillator than the current standard in general radiography. The results support the translation of the CMOS sensor with 400 μ m CsI onto the clinical prototype of CMOS-based extremity CBCT.

High-resolution extremity cone-beam CT with a CMOS detector: Task-based optimization of scintillator thickness

PubMed Central

Cao, Q.; Brehler, M.; Sisniega, A.; Stayman, J. W.; Yorkston, J.; Siewerdsen, J. H.; Zbijewski, W.

2017-01-01

Purpose CMOS x-ray detectors offer small pixel sizes and low electronic noise that may support the development of novel high-resolution imaging applications of cone-beam CT (CBCT). We investigate the effects of CsI scintillator thickness on the performance of CMOS detectors in high resolution imaging tasks, in particular in quantitative imaging of bone microstructure in extremity CBCT. Methods A scintillator thickness-dependent cascaded systems model of CMOS x-ray detectors was developed. Detectability in low-, high- and ultra-high resolution imaging tasks (Gaussian with FWHM of ~250 μm, ~80 μm and ~40 μm, respectively) was studied as a function of scintillator thickness using the theoretical model. Experimental studies were performed on a CBCT test bench equipped with DALSA Xineos3030 CMOS detectors (99 μm pixels) with CsI scintillator thicknesses of 400 μm and 700 μm, and a 0.3 FS compact rotating anode x-ray source. The evaluation involved a radiographic resolution gauge (0.6–5.0 lp/mm), a 127 μm tungsten wire for assessment of 3D resolution, a contrast phantom with tissue-mimicking inserts, and an excised fragment of human tibia for visual assessment of fine trabecular detail. Results Experimental studies show ~35% improvement in the frequency of 50% MTF modulation when using the 400 μm scintillator compared to the standard nominal CsI thickness of 700 μm. Even though the high-frequency DQE of the two detectors is comparable, theoretical studies show a 14% to 28% increase in detectability index (d′2) of high- and ultrahigh resolution tasks, respectively, for the detector with 400 μm CsI compared to 700 μm CsI. Experiments confirm the theoretical findings, showing improvements with the adoption of 400 μm panel in the visibility of the radiographic pattern (2× improvement in peak-to-through distance at 4.6 lp/mm) and a 12.5% decrease in the FWHM of the tungsten wire. Reconstructions of the tibial plateau reveal enhanced visibility of trabecular structures with the CMOS detector with 400 μm scinitllator. Conclusion Applications on CMOS detectors in high resolution CBCT imaging of trabecular bone will benefit from using a thinner scintillator than the current standard in general radiography. The results support the translation of the CMOS sensor with 400 μm CsI onto the clinical prototype of CMOS-based extremity CBCT. PMID:28989220

Application of machine learning techniques to lepton energy reconstruction in water Cherenkov detectors

NASA Astrophysics Data System (ADS)

Drakopoulou, E.; Cowan, G. A.; Needham, M. D.; Playfer, S.; Taani, M.

2018-04-01

The application of machine learning techniques to the reconstruction of lepton energies in water Cherenkov detectors is discussed and illustrated for TITUS, a proposed intermediate detector for the Hyper-Kamiokande experiment. It is found that applying these techniques leads to an improvement of more than 50% in the energy resolution for all lepton energies compared to an approach based upon lookup tables. Machine learning techniques can be easily applied to different detector configurations and the results are comparable to likelihood-function based techniques that are currently used.

Effects of detector-source distance and detector bias voltage variations on time resolution of general purpose plastic scintillation detectors.

PubMed

Ermis, E E; Celiktas, C

2012-12-01

Effects of source-detector distance and the detector bias voltage variations on time resolution of a general purpose plastic scintillation detector such as BC400 were investigated. (133)Ba and (207)Bi calibration sources with and without collimator were used in the present work. Optimum source-detector distance and bias voltage values were determined for the best time resolution by using leading edge timing method. Effect of the collimator usage on time resolution was also investigated. Copyright © 2012 Elsevier Ltd. All rights reserved.

Characteristic performance evaluation of a photon counting Si strip detector for low dose spectral breast CT imaging

PubMed Central

Cho, Hyo-Min; Barber, William C.; Ding, Huanjun; Iwanczyk, Jan S.; Molloi, Sabee

2014-01-01

Purpose: The possible clinical applications which can be performed using a newly developed detector depend on the detector's characteristic performance in a number of metrics including the dynamic range, resolution, uniformity, and stability. The authors have evaluated a prototype energy resolved fast photon counting x-ray detector based on a silicon (Si) strip sensor used in an edge-on geometry with an application specific integrated circuit to record the number of x-rays and their energies at high flux and fast frame rates. The investigated detector was integrated with a dedicated breast spectral computed tomography (CT) system to make use of the detector's high spatial and energy resolution and low noise performance under conditions suitable for clinical breast imaging. The aim of this article is to investigate the intrinsic characteristics of the detector, in terms of maximum output count rate, spatial and energy resolution, and noise performance of the imaging system. Methods: The maximum output count rate was obtained with a 50 W x-ray tube with a maximum continuous output of 50 kVp at 1.0 mA. A109Cd source, with a characteristic x-ray peak at 22 keV from Ag, was used to measure the energy resolution of the detector. The axial plane modulation transfer function (MTF) was measured using a 67 μm diameter tungsten wire. The two-dimensional (2D) noise power spectrum (NPS) was measured using flat field images and noise equivalent quanta (NEQ) were calculated using the MTF and NPS results. The image quality parameters were studied as a function of various radiation doses and reconstruction filters. The one-dimensional (1D) NPS was used to investigate the effect of electronic noise elimination by varying the minimum energy threshold. Results: A maximum output count rate of 100 million counts per second per square millimeter (cps/mm2) has been obtained (1 million cps per 100 × 100 μm pixel). The electrical noise floor was less than 4 keV. The energy resolution measured with the 22 keV photons from a 109Cd source was less than 9%. A reduction of image noise was shown in all the spatial frequencies in 1D NPS as a result of the elimination of the electronic noise. The spatial resolution was measured just above 5 line pairs per mm (lp/mm) where 10% of MTF corresponded to 5.4 mm−1. The 2D NPS and NEQ shows a low noise floor and a linear dependence on dose. The reconstruction filter choice affected both of the MTF and NPS results, but had a weak effect on the NEQ. Conclusions: The prototype energy resolved photon counting Si strip detector can offer superior imaging performance for dedicated breast CT as compared to a conventional energy-integrating detector due to its high output count rate, high spatial and energy resolution, and low noise characteristics, which are essential characteristics for spectral breast CT imaging. PMID:25186390

Imaging performance of an amorphous selenium digital mammography detector in a breast tomosynthesis system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao Bo; Zhao Wei

2008-05-15

In breast tomosynthesis a rapid sequence of N images is acquired when the x-ray tube sweeps through different angular views with respect to the breast. Since the total dose to the breast is kept the same as that in regular mammography, the exposure used for each image of tomosynthesis is 1/N. The low dose and high frame rate pose a tremendous challenge to the imaging performance of digital mammography detectors. The purpose of the present work is to investigate the detector performance in different operational modes designed for tomosynthesis acquisition, e.g., binning or full resolution readout, the range of viewmore » angles, and the number of views N. A prototype breast tomosynthesis system with a nominal angular range of {+-}25 deg. was used in our investigation. The system was equipped with an amorphous selenium (a-Se) full field digital mammography detector with pixel size of 85 {mu}m. The detector can be read out in full resolution or 2x1 binning (binning in the tube travel direction). The focal spot blur due to continuous tube travel was measured for different acquisition geometries, and it was found that pixel binning, instead of focal spot blur, dominates the detector modulation transfer function (MTF). The noise power spectrum (NPS) and detective quantum efficiency (DQE) of the detector were measured with the exposure range of 0.4-6 mR, which is relevant to the low dose used in tomosynthesis. It was found that DQE at 0.4 mR is only 20% less than that at highest exposure for both detector readout modes. The detector temporal performance was categorized as lag and ghosting, both of which were measured as a function of x-ray exposure. The first frame lags were 8% and 4%, respectively, for binning and full resolution mode. Ghosting is negligible and independent of the frame rate. The results showed that the detector performance is x-ray quantum noise limited at the low exposures used in each view of tomosynthesis, and the temporal performance at high frame rate (up to 2 frames per second) is adequate for tomosynthesis.« less

The timing resolution of scintillation-detector systems: Monte Carlo analysis

NASA Astrophysics Data System (ADS)

Choong, Woon-Seng

2009-11-01

Recent advancements in fast scintillating materials and fast photomultiplier tubes (PMTs) have stimulated renewed interest in time-of-flight (TOF) positron emission tomography (PET). It is well known that the improvement in the timing resolution in PET can significantly reduce the noise variance in the reconstructed image resulting in improved image quality. In order to evaluate the timing performance of scintillation detectors used in TOF PET, we use Monte Carlo analysis to model the physical processes (crystal geometry, crystal surface finish, scintillator rise time, scintillator decay time, photoelectron yield, PMT transit time spread, PMT single-electron response, amplifier response and time pick-off method) that can contribute to the timing resolution of scintillation-detector systems. In the Monte Carlo analysis, the photoelectron emissions are modeled by a rate function, which is used to generate the photoelectron time points. The rate function, which is simulated using Geant4, represents the combined intrinsic light emissions of the scintillator and the subsequent light transport through the crystal. The PMT output signal is determined by the superposition of the PMT single-electron response resulting from the photoelectron emissions. The transit time spread and the single-electron gain variation of the PMT are modeled in the analysis. Three practical time pick-off methods are considered in the analysis. Statistically, the best timing resolution is achieved with the first photoelectron timing. The calculated timing resolution suggests that a leading edge discriminator gives better timing performance than a constant fraction discriminator and produces comparable results when a two-threshold or three-threshold discriminator is used. For a typical PMT, the effect of detector noise on the timing resolution is negligible. The calculated timing resolution is found to improve with increasing mean photoelectron yield, decreasing scintillator decay time and decreasing transit time spread. However, only substantial improvement in the timing resolution is obtained with improved transit time spread if the first photoelectron timing is less than the transit time spread. While the calculated timing performance does not seem to be affected by the pixel size of the crystal, it improves for an etched crystal compared to a polished crystal. In addition, the calculated timing resolution degrades with increasing crystal length. These observations can be explained by studying the initial photoelectron rate. Experimental measurements provide reasonably good agreement with the calculated timing resolution. The Monte Carlo analysis developed in this work will allow us to optimize the scintillation detectors for timing and to understand the physical factors limiting their performance.

The timing resolution of scintillation-detector systems: Monte Carlo analysis.

PubMed

Choong, Woon-Seng

2009-11-07

Recent advancements in fast scintillating materials and fast photomultiplier tubes (PMTs) have stimulated renewed interest in time-of-flight (TOF) positron emission tomography (PET). It is well known that the improvement in the timing resolution in PET can significantly reduce the noise variance in the reconstructed image resulting in improved image quality. In order to evaluate the timing performance of scintillation detectors used in TOF PET, we use Monte Carlo analysis to model the physical processes (crystal geometry, crystal surface finish, scintillator rise time, scintillator decay time, photoelectron yield, PMT transit time spread, PMT single-electron response, amplifier response and time pick-off method) that can contribute to the timing resolution of scintillation-detector systems. In the Monte Carlo analysis, the photoelectron emissions are modeled by a rate function, which is used to generate the photoelectron time points. The rate function, which is simulated using Geant4, represents the combined intrinsic light emissions of the scintillator and the subsequent light transport through the crystal. The PMT output signal is determined by the superposition of the PMT single-electron response resulting from the photoelectron emissions. The transit time spread and the single-electron gain variation of the PMT are modeled in the analysis. Three practical time pick-off methods are considered in the analysis. Statistically, the best timing resolution is achieved with the first photoelectron timing. The calculated timing resolution suggests that a leading edge discriminator gives better timing performance than a constant fraction discriminator and produces comparable results when a two-threshold or three-threshold discriminator is used. For a typical PMT, the effect of detector noise on the timing resolution is negligible. The calculated timing resolution is found to improve with increasing mean photoelectron yield, decreasing scintillator decay time and decreasing transit time spread. However, only substantial improvement in the timing resolution is obtained with improved transit time spread if the first photoelectron timing is less than the transit time spread. While the calculated timing performance does not seem to be affected by the pixel size of the crystal, it improves for an etched crystal compared to a polished crystal. In addition, the calculated timing resolution degrades with increasing crystal length. These observations can be explained by studying the initial photoelectron rate. Experimental measurements provide reasonably good agreement with the calculated timing resolution. The Monte Carlo analysis developed in this work will allow us to optimize the scintillation detectors for timing and to understand the physical factors limiting their performance.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scaduto, DA; Hu, Y-H; Zhao, W

Purpose: Spatial resolution in digital breast tomosynthesis (DBT) is affected by inherent/binned detector resolution, oblique entry of x-rays, and focal spot size/motion; the limited angular range further limits spatial resolution in the depth-direction. While DBT is being widely adopted clinically, imaging performance metrics and quality control protocols have not been standardized. AAPM Task Group 245 on Tomosynthesis Quality Control has been formed to address this deficiency. Methods: Methods of measuring spatial resolution are evaluated using two prototype quality control phantoms for DBT. Spatial resolution in the detector plane is measured in projection and reconstruction domains using edge-spread function (ESF), point-spreadmore » function (PSF) and modulation transfer function (MTF). Spatial resolution in the depth-direction and effective slice thickness are measured in the reconstruction domain using slice sensitivity profile (SSP) and artifact spread function (ASF). An oversampled PSF in the depth-direction is measured using a 50 µm angulated tungsten wire, from which the MTF is computed. Object-dependent PSF is derived and compared with ASF. Sensitivity of these measurements to phantom positioning, imaging conditions and reconstruction algorithms is evaluated. Results are compared from systems of varying acquisition geometry (9–25 projections over 15–60°). Dependence of measurements on feature size is investigated. Results: Measurements of spatial resolution using PSF and LSF are shown to depend on feature size; depth-direction spatial resolution measurements are shown to similarly depend on feature size for ASF, though deconvolution with an object function removes feature size-dependence. A slanted wire may be used to measure oversampled PSFs, from which MTFs may be computed for both in-plane and depth-direction resolution. Conclusion: Spatial resolution measured using PSF is object-independent with sufficiently small object; MTF is object-independent. Depth-direction spatial resolution may be measured directly using MTF or indirectly using ASF or SSP as surrogate measurements. While MTF is object-independent, it is invalid for nonlinear reconstructions.« less

Double difference method in deep inelastic neutron scattering on the VESUVIO spectrometer

NASA Astrophysics Data System (ADS)

Andreani, C.; Colognesi, D.; Degiorgi, E.; Filabozzi, A.; Nardone, M.; Pace, E.; Pietropaolo, A.; Senesi, R.

2003-02-01

The principles of the Double Difference (DD) method, applied to the neutron spectrometer VESUVIO, are discussed. VESUVIO, an inverse geometry spectrometer operating at the ISIS pulsed neutron source in the eV energy region, has been specifically designed to measure the single particle dynamical properties in condensed matter. The width of the nuclear resonance of the absorbing filter, used for the neutron energy analysis, provides the most important contribution to the energy resolution of the inverse geometry instruments. In this paper, the DD method, which is based on a linear combination of two measurements recorded with filter foils of the same resonance material but of different thickness, is shown to improve significantly the instrumental energy resolution, as compared with the Single Difference (SD) method. The asymptotic response functions, derived through Monte-Carlo simulations for polycrystalline Pb and ZrH 2 samples, are analysed in both DD and SD methods, and compared with the experimental ones for Pb sample. The response functions have been modelled for two distinct experimental configurations of the VESUVIO spectrometer, employing 6Li-glass neutron detectors and NaI γ detectors revealing the γ-ray cascade from the ( n,γ) reaction, respectively. The DD method appears to be an effective experimental procedure for Deep Inelastic Neutron Scattering measurements on VESUVIO spectrometer, since it reduces the experimental resolution of the instrument in both 6Li-glass neutron detector and γ detector configurations.

Performance evaluation of a compact PET/SPECT/CT tri-modality system for small animal imaging applications

NASA Astrophysics Data System (ADS)

Wei, Qingyang; Wang, Shi; Ma, Tianyu; Wu, Jing; Liu, Hui; Xu, Tianpeng; Xia, Yan; Fan, Peng; Lyu, Zhenlei; Liu, Yaqiang

2015-06-01

PET, SPECT and CT imaging techniques are widely used in preclinical small animal imaging applications. In this paper, we present a compact small animal PET/SPECT/CT tri-modality system. A dual-functional, shared detector design is implemented which enables PET and SPECT imaging with a same LYSO ring detector. A multi-pinhole collimator is mounted on the system and inserted into the detector ring in SPECT imaging mode. A cone-beam CT consisting of a micro focus X-ray tube and a CMOS detector is implemented. The detailed design and the performance evaluations are reported in this paper. In PET imaging mode, the measured NEMA based spatial resolution is 2.12 mm (FWHM), and the sensitivity at the central field of view (CFOV) is 3.2%. The FOV size is 50 mm (∅)×100 mm (L). The SPECT has a spatial resolution of 1.32 mm (FWHM) and an average sensitivity of 0.031% at the center axial, and a 30 mm (∅)×90 mm (L) FOV. The CT spatial resolution is 8.32 lp/mm @10%MTF, and the contrast discrimination function value is 2.06% with 1.5 mm size cubic box object. In conclusion, a compact, tri-modality PET/SPECT/CT system was successfully built with low cost and high performance.

Measurement of the Energy-Dependent Angular Response of the ARES Detector System and Application to Aerial Imaging

NASA Astrophysics Data System (ADS)

Joshi, Tenzing H. Y.; Quiter, Brian J.; Maltz, Jonathan S.; Bandstra, Mark S.; Haefner, Andrew; Eikmeier, Nicole; Wagner, Eric; Luke, Tanushree; Malchow, Russell; McCall, Karen

2017-07-01

The Airborne Radiological Enhanced-sensor System (ARES) includes a prototype helicopter-borne CsI(Na) detector array that has been developed as part of the DHS Domestic Nuclear Detection Office Advanced Technology Demonstration. The detector system geometry comprises two pairs of 23-detector arrays designed to function as active masks, providing additional angular resolution of measured gamma rays in the roll dimension. Experimental measurements, using five radioisotopes (137Cs, 60Co, 241Am, 131I, and 99mTc), were performed to map the detector response in both roll and pitch dimensions. This paper describes the acquisition and analysis of these characterization measurements, calculation of the angular response of the ARES system, and how this response function is used to improve aerial detection and localization of radiological and nuclear threat sources.

The Detector Subsystem for the SXS Instrument on the Astro-H Observatory

NASA Technical Reports Server (NTRS)

Porter, Frederick; Adams, J. S.; Brown, G. V.; Chervenak, J. A.; Chiao, M. P.; Fujimoto, R.; Ishisaki, Y.; Kelley, R. L.; Kilbourne, C. A.; McCammon, D.;

Reducing the spatial resolution range of neutron radiographs cast by thick objects

NASA Astrophysics Data System (ADS)

Almeida, G. L.; Silvani, M. I.; Souza, E. S.; Lopes, R. T.

2017-11-01

The quality of a neutron radiograph is strongly dependent upon the features of the acquisition system. Most of them, such as detector resolution, electronic noise and statistical fluctuation can hardly be improved. Yet, a main parameter ruling the image spatial resolution, namely the L/D ratio of the system can be increased simply by lengthening the source-detector clearance. Such an option eventually may not be feasible due to neutron flux decreasing or engineering constraints. Under this circumstance, a radiograph improvement is only possible by some kind of after-acquisition procedure capable to retrieve, at least partially, the information concealed by the degradation process. Since the spoiling agent tied to the L/D has a systematic character, its impact can be reduced by an unfolding procedure such as Richardson-Lucy algorithm. However, that agent should be fully characterized and furnished to the algorithm as a Point Spread Function - PSF unfolding function. A main drawback of unfolding algorithms like Richardson-Lucy is that the PSF should be fixed, i.e., it assumes a certain constant image spatial resolution, rather than a variable one as actually occurs for thick objects. This work presents a methodology to minimize this difficulty by making all planes of the inspected object to cast a resolution within the shorter gap comprised between the object central plane and the detector. The image can then be unfolded with a lower resolution within a tighter range, yielding a better quality. The process is performed with two radiographs, where one of them is acquired with the object turned by 180° on its vertical axis with regard to the other. After a mirroring of one of them about its vertical axis, the images are added. As the resolution increases linearly with the object-detector gap, it would remain always lower than that of the central one. Therefore, the overall resolution of the composite radiograph is enhanced. A further improvement can then be achieved through an efficient unfolding since the object has been virtually shrunk along the neutron path.

150-μm Spatial Resolution Using Photon-Counting Detector Computed Tomography Technology: Technical Performance and First Patient Images.

PubMed

Leng, Shuai; Rajendran, Kishore; Gong, Hao; Zhou, Wei; Halaweish, Ahmed F; Henning, Andre; Kappler, Steffen; Baer, Matthias; Fletcher, Joel G; McCollough, Cynthia H

2018-05-28

The aims of this study were to quantitatively assess two new scan modes on a photon-counting detector computed tomography system, each designed to maximize spatial resolution, and to qualitatively demonstrate potential clinical impact using patient data. This Health Insurance Portability Act-compliant study was approved by our institutional review board. Two high-spatial-resolution scan modes (Sharp and UHR) were evaluated using phantoms to quantify spatial resolution and image noise, and results were compared with the standard mode (Macro). Patients were scanned using a conventional energy-integrating detector scanner and the photon-counting detector scanner using the same radiation dose. In first patient images, anatomic details were qualitatively evaluated to demonstrate potential clinical impact. Sharp and UHR modes had a 69% and 87% improvement in in-plane spatial resolution, respectively, compared with Macro mode (10% modulation-translation-function values of 16.05, 17.69, and 9.48 lp/cm, respectively). The cutoff spatial frequency of the UHR mode (32.4 lp/cm) corresponded to a limiting spatial resolution of 150 μm. The full-width-at-half-maximum values of the section sensitivity profiles were 0.41, 0.44, and 0.67 mm for the thinnest image thickness for each mode (0.25, 0.25, and 0.5 mm, respectively). At the same in-plane spatial resolution, Sharp and UHR images had up to 15% lower noise than Macro images. Patient images acquired in Sharp mode demonstrated better delineation of fine anatomic structures compared with Macro mode images. Phantom studies demonstrated superior resolution and noise properties for the Sharp and UHR modes relative to the standard Macro mode and patient images demonstrated the potential benefit of these scan modes for clinical practice.

High-resolution ionization detector and array of such detectors

DOEpatents

McGregor, Douglas S [Ypsilanti, MI; Rojeski, Ronald A [Pleasanton, CA

2001-01-16

A high-resolution ionization detector and an array of such detectors are described which utilize a reference pattern of conductive or semiconductive material to form interaction, pervious and measurement regions in an ionization substrate of, for example, CdZnTe material. The ionization detector is a room temperature semiconductor radiation detector. Various geometries of such a detector and an array of such detectors produce room temperature operated gamma ray spectrometers with relatively high resolution. For example, a 1 cm.sup.3 detector is capable of measuring .sup.137 Cs 662 keV gamma rays with room temperature energy resolution approaching 2% at FWHM. Two major types of such detectors include a parallel strip semiconductor Frisch grid detector and the geometrically weighted trapezoid prism semiconductor Frisch grid detector. The geometrically weighted detector records room temperature (24.degree. C.) energy resolutions of 2.68% FWHM for .sup.137 Cs 662 keV gamma rays and 2.45% FWHM for .sup.60 Co 1.332 MeV gamma rays. The detectors perform well without any electronic pulse rejection, correction or compensation techniques. The devices operate at room temperature with simple commercially available NIM bin electronics and do not require special preamplifiers or cooling stages for good spectroscopic results.

Detector motion method to increase spatial resolution in photon-counting detectors

NASA Astrophysics Data System (ADS)

Lee, Daehee; Park, Kyeongjin; Lim, Kyung Taek; Cho, Gyuseong

2017-03-01

Medical imaging requires high spatial resolution of an image to identify fine lesions. Photon-counting detectors in medical imaging have recently been rapidly replacing energy-integrating detectors due to the former`s high spatial resolution, high efficiency and low noise. Spatial resolution in a photon counting image is determined by the pixel size. Therefore, the smaller the pixel size, the higher the spatial resolution that can be obtained in an image. However, detector redesigning is required to reduce pixel size, and an expensive fine process is required to integrate a signal processing unit with reduced pixel size. Furthermore, as the pixel size decreases, charge sharing severely deteriorates spatial resolution. To increase spatial resolution, we propose a detector motion method using a large pixel detector that is less affected by charge sharing. To verify the proposed method, we utilized a UNO-XRI photon-counting detector (1-mm CdTe, Timepix chip) at the maximum X-ray tube voltage of 80 kVp. A similar spatial resolution of a 55- μm-pixel image was achieved by application of the proposed method to a 110- μm-pixel detector with a higher signal-to-noise ratio. The proposed method could be a way to increase spatial resolution without a pixel redesign when pixels severely suffer from charge sharing as pixel size is reduced.

Estimation of time resolution for DOI-PET detector using diameter 0.2 mm WLS fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobayashi, A.; Ito, H.; Han, S.

We are developing the whole-body PET detector with high position resolution (1 mm) and low cost (1 M dollars). Scintillator plates, Wave Length Sifting Fibers and SiPMs are used. In this work, time resolution of our PET detector is estimated. Our detector may also have good time resolution such as a few ps. (authors)

Fusion proton diagnostic for the C-2 field reversed configurationa)

NASA Astrophysics Data System (ADS)

Magee, R. M.; Clary, R.; Korepanov, S.; Smirnov, A.; Garate, E.; Knapp, K.; Tkachev, A.

2014-11-01

Measurements of the flux of fusion products from high temperature plasmas provide valuable insights into the ion energy distribution, as the fusion reaction rate is a very sensitive function of ion energy. In C-2, where field reversed configuration plasmas are formed by the collision of two compact toroids and partially sustained by high power neutral beam injection [M. Binderbauer et al., Phys. Rev. Lett. 105, 045003 (2010); M. Tuszewski et al., Phys. Rev. Lett. 108, 255008 (2012)], measurements of DD fusion neutron flux are used to diagnose ion temperature and study fast ion confinement and dynamics. In this paper, we will describe the development of a new 3 MeV proton detector that will complement existing neutron detectors. The detector is a large area (50 cm2), partially depleted, ion implanted silicon diode operated in a pulse counting regime. While the scintillator-based neutron detectors allow for high time resolution measurements (˜100 kHz), they have no spatial or energy resolution. The proton detector will provide 10 cm spatial resolution, allowing us to determine if the axial distribution of fast ions is consistent with classical fast ion theory or whether anomalous scattering mechanisms are active. We will describe in detail the diagnostic design and present initial data from a neutral beam test chamber.

Evaluation of position-estimation methods applied to CZT-based photon-counting detectors for dedicated breast CT

PubMed Central

Makeev, Andrey; Clajus, Martin; Snyder, Scott; Wang, Xiaolang; Glick, Stephen J.

2015-01-01

Abstract. Semiconductor photon-counting detectors based on high atomic number, high density materials [cadmium zinc telluride (CZT)/cadmium telluride (CdTe)] for x-ray computed tomography (CT) provide advantages over conventional energy-integrating detectors, including reduced electronic and Swank noise, wider dynamic range, capability of spectral CT, and improved signal-to-noise ratio. Certain CT applications require high spatial resolution. In breast CT, for example, visualization of microcalcifications and assessment of tumor microvasculature after contrast enhancement require resolution on the order of 100  μm. A straightforward approach to increasing spatial resolution of pixellated CZT-based radiation detectors by merely decreasing the pixel size leads to two problems: (1) fabricating circuitry with small pixels becomes costly and (2) inter-pixel charge spreading can obviate any improvement in spatial resolution. We have used computer simulations to investigate position estimation algorithms that utilize charge sharing to achieve subpixel position resolution. To study these algorithms, we model a simple detector geometry with a 5×5 array of 200  μm pixels, and use a conditional probability function to model charge transport in CZT. We used COMSOL finite element method software to map the distribution of charge pulses and the Monte Carlo package PENELOPE for simulating fluorescent radiation. Performance of two x-ray interaction position estimation algorithms was evaluated: the method of maximum-likelihood estimation and a fast, practical algorithm that can be implemented in a readout application-specific integrated circuit and allows for identification of a quadrant of the pixel in which the interaction occurred. Both methods demonstrate good subpixel resolution; however, their actual efficiency is limited by the presence of fluorescent K-escape photons. Current experimental breast CT systems typically use detectors with a pixel size of 194  μm, with 2×2 binning during the acquisition giving an effective pixel size of 388  μm. Thus, it would be expected that the position estimate accuracy reported in this study would improve detection and visualization of microcalcifications as compared to that with conventional detectors. PMID:26158095

Evaluation of position-estimation methods applied to CZT-based photon-counting detectors for dedicated breast CT.

PubMed

Makeev, Andrey; Clajus, Martin; Snyder, Scott; Wang, Xiaolang; Glick, Stephen J

2015-04-01

Semiconductor photon-counting detectors based on high atomic number, high density materials [cadmium zinc telluride (CZT)/cadmium telluride (CdTe)] for x-ray computed tomography (CT) provide advantages over conventional energy-integrating detectors, including reduced electronic and Swank noise, wider dynamic range, capability of spectral CT, and improved signal-to-noise ratio. Certain CT applications require high spatial resolution. In breast CT, for example, visualization of microcalcifications and assessment of tumor microvasculature after contrast enhancement require resolution on the order of [Formula: see text]. A straightforward approach to increasing spatial resolution of pixellated CZT-based radiation detectors by merely decreasing the pixel size leads to two problems: (1) fabricating circuitry with small pixels becomes costly and (2) inter-pixel charge spreading can obviate any improvement in spatial resolution. We have used computer simulations to investigate position estimation algorithms that utilize charge sharing to achieve subpixel position resolution. To study these algorithms, we model a simple detector geometry with a [Formula: see text] array of [Formula: see text] pixels, and use a conditional probability function to model charge transport in CZT. We used COMSOL finite element method software to map the distribution of charge pulses and the Monte Carlo package PENELOPE for simulating fluorescent radiation. Performance of two x-ray interaction position estimation algorithms was evaluated: the method of maximum-likelihood estimation and a fast, practical algorithm that can be implemented in a readout application-specific integrated circuit and allows for identification of a quadrant of the pixel in which the interaction occurred. Both methods demonstrate good subpixel resolution; however, their actual efficiency is limited by the presence of fluorescent [Formula: see text]-escape photons. Current experimental breast CT systems typically use detectors with a pixel size of [Formula: see text], with [Formula: see text] binning during the acquisition giving an effective pixel size of [Formula: see text]. Thus, it would be expected that the position estimate accuracy reported in this study would improve detection and visualization of microcalcifications as compared to that with conventional detectors.

Depth resolved grazing incidence neutron scattering experiments from semi-infinite interfaces: a statistical analysis of the scattering contributions

NASA Astrophysics Data System (ADS)

Adlmann, Franz A.; Herbel, Jörg; Korolkovas, Airidas; Bliersbach, Andreas; Toperverg, Boris; Van Herck, Walter; Pálsson, Gunnar K.; Kitchen, Brian; Wolff, Max

2018-04-01

Grazing incidence neutron scattering experiments offer surface sensitivity by reflecting from an interface at momentum transfers close to total external reflection. Under these conditions the penetration depth is strongly non-linear and may change by many orders of magnitude. This fact imposes severe challenges for depth resolved experiments, since the brilliance of neutron beams is relatively low in comparison to e.g. synchrotron radiation. In this article we use probability density functions to calculate the contribution of scattering at different distances from an interface to the intensities registered on the detector. Our method has the particular advantage that the depth sensitivity is directly extracted from the scattering pattern itself. Hence for perfectly known samples exact resolution functions can be calculated and visa versa. We show that any tails in the resolution function, e.g. Gaussian shaped, hinders depth resolved experiments. More importantly we provide means for a descriptive statistical analysis of detector images with respect to the scattering contributions and show that even for perfect resolution near surface scattering is hardly accessible.

An edge-readout, multilayer detector for positron emission tomography.

PubMed

Li, Xin; Ruiz-Gonzalez, Maria; Furenlid, Lars R

2018-06-01

We present a novel gamma-ray-detector design based on total internal reflection (TIR) of scintillation photons within a crystal that addresses many limitations of traditional PET detectors. Our approach has appealing features, including submillimeter lateral resolution, DOI positioning from layer thickness, and excellent energy resolution. The design places light sensors on the edges of a stack of scintillator slabs separated by small air gaps and exploits the phenomenon that more than 80% of scintillation light emitted during a gamma-ray event reaches the edges of a thin crystal with polished faces due to TIR. Gamma-ray stopping power is achieved by stacking multiple layers, and DOI is determined by which layer the gamma ray interacts in. The concept of edge readouts of a thin slab was verified by Monte Carlo simulation of scintillation light transport. An LYSO crystal of dimensions 50.8 mm × 50.8 mm × 3.0 mm was modeled with five rectangular SiPMs placed along each edge face. The mean-detector-response functions (MDRFs) were calculated by simulating signals from 511 keV gamma-ray interactions in a grid of locations. Simulations were carried out to study the influence of choice of scintillator material and dimensions, gamma-ray photon energies, introduction of laser or mechanically induced optical barriers (LIOBs, MIOBs), and refractive indices of optical-coupling media and SiPM windows. We also analyzed timing performance including influence of gamma-ray interaction position and presence of optical barriers. We also modeled and built a prototype detector, a 27.4 mm × 27.4 mm × 3.0 mm CsI(Tl) crystal with 4 SiPMs per edge to experimentally validate the results predicted by the simulations. The prototype detector used CsI(Tl) crystals from Proteus outfitted with 16 Hamamatsu model S13360-6050PE MPPCs read out by an AiT-16-channel readout. The MDRFs were measured by scanning the detector with a collimated beam of 662-keV photons from a 137 Cs source. The spatial resolution was experimentally determined by imaging a tungsten slit that created a beam of 0.44 mm (FWHM) width normal to the detector surface. The energy resolution was evaluated by analyzing list-mode data from flood illumination by the 137 Cs source. We find that in a block-detector-sized LYSO layer read out by five SiPMs per edge, illuminated by 511-keV photons, the average resolution is 1.49 mm (FWHM). With the introduction of optical barriers, average spatial resolution improves to 0.56 mm (FWHM). The DOI resolution is the layer thickness of 3.0 mm. We also find that optical-coupling media and SiPM-window materials have an impact on spatial resolution. The timing simulation with LYSO crystal yields a coincidence resolving time (CRT) of 200-400 ps, which is slightly position dependent. And the introduction of optical barriers has minimum influence. The prototype CsI(Tl) detector, with a smaller area and fewer SiPMs, was measured to have central-area spatial resolutions of 0.70 and 0.39 mm without and with optical barriers, respectively. These results match well with our simulations. An energy resolution of 6.4% was achieved at 662 keV. A detector design based on a stack of monolithic scintillator layers that uses edge readouts offers several advantages over current block detectors for PET. For example, there is no tradeoff between spatial resolution and detection sensitivity since no reflector material displaces scintillator crystal, and submillimeter resolution can be achieved. DOI information is readily available, and excellent timing and energy resolutions are possible. © 2018 The Authors. Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Positron Emission Mammography with Multiple Angle Acquisition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mark F. Smith; Stan Majewski; Raymond R. Raylman

2002-11-01

Positron emission mammography (PEM) of F-18 fluorodeoxyglucose (FbG) uptake in breast tumors with dedicated detectors typically has been accomplished with two planar detectors in a fixed position with the breast under compression. The potential use of PEM imaging at two detector positions to guide stereotactic breast biopsy has motivated us to use PEM coincidence data acquired at two or more detector positions together in a single image reconstruction. Multiple angle PEM acquisition and iterative image reconstruction were investigated using point source and compressed breast phantom acquisitions with 5, 9, 12 and 15 mm diameter spheres and a simulated tumor:background activitymore » concentration ratio of 6:1. Image reconstruction was performed with an iterative MLEM algorithm that used coincidence events between any two detector pixels on opposed detector heads at each detector position. This present study compared two acquisition protocols: 2 angle acquisition with detector angular positions of -15 and +15 degrees and 11 angle acquisition with detector positions spaced at 3 degree increments over the range -15 to +15 degrees. Three-dimensional image resolution was assessed for the point source acquisitions, and contrast and signal-to-noise metrics were evaluated for the compressed breast phantom with different simulated tumor sizes. Radial and tangential resolutions were similar for the two protocols, while normal resolution was better for the 2 angle acquisition. Analysis is complicated by the asymmetric point spread functions. Signal- to-noise vs. contrast tradeoffs were better for 11 angle acquisition for the smallest visible 9 mm sphere, while tradeoff results were mixed for the larger and more easily visible 12 mm and 15 mm diameter spheres. Additional study is needed to better understand the performance of limited angle tomography for PEM. PEM tomography experiments with complete angular sampling are planned.« less

Temporal and spectral manipulations of correlated photons using a time lens

NASA Astrophysics Data System (ADS)

Mittal, Sunil; Orre, Venkata Vikram; Restelli, Alessandro; Salem, Reza; Goldschmidt, Elizabeth A.; Hafezi, Mohammad

2017-10-01

A common challenge in quantum information processing with photons is the limited ability to manipulate and measure correlated states. An example is the inability to measure picosecond-scale temporal correlations of a multiphoton state, given state-of-the-art detectors have a temporal resolution of about 100 ps. Here, we demonstrate temporal magnification of time-bin-entangled two-photon states using a time lens and measure their temporal correlation function, which is otherwise not accessible because of the limited temporal resolution of single-photon detectors. Furthermore, we show that the time lens maps temporal correlations of photons to frequency correlations and could be used to manipulate frequency-bin-entangled photons. This demonstration opens a new avenue to manipulate and analyze spectral and temporal wave functions of many-photon states.

Characteristics of depth-sensing coplanar grid CdZnTe detectors

NASA Astrophysics Data System (ADS)

He, Zhong; Sturm, Ben W.

2005-12-01

The latest depth-sensing coplanar grid CdZnTe detectors have been tested. Two of these have dimensions 1.5×1.5×1.0 cm 3 and one is a cylindrical detector with 1.5 cm diameter and 1.0 cm length, all of them using the third-generation coplanar anode design. Energy resolutions of 2.0% and 2.4% FWHM at 662 keV γ-ray energies were obtained. Detector performance has been observed experimentally as a function of depth of the γ-ray interaction, and as a function of radial position near the anode surface. The measured results show the improvement of the third-generation anode design. Material uniformity of CdZnTe crystals manufactured by eV Products have been directly observed and compared on two 1.5×1.5×1.0 cm 3 detectors.

High Resolution PET with 250 micrometer LSO Detectors and Adaptive Zoom

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cherry, Simon R.; Qi, Jinyi

2012-01-08

There have been impressive improvements in the performance of small-animal positron emission tomography (PET) systems since their first development in the mid 1990s, both in terms of spatial resolution and sensitivity, which have directly contributed to the increasing adoption of this technology for a wide range of biomedical applications. Nonetheless, current systems still are largely dominated by the size of the scintillator elements used in the detector. Our research predicts that developing scintillator arrays with an element size of 250 {micro}m or smaller will lead to an image resolution of 500 {micro}m when using 18F- or 64Cu-labeled radiotracers, giving amore » factor of 4-8 improvement in volumetric resolution over the highest resolution research systems currently in existence. This proposal had two main objectives: (i) To develop and evaluate much higher resolution and efficiency scintillator arrays that can be used in the future as the basis for detectors in a small-animal PET scanner where the spatial resolution is dominated by decay and interaction physics rather than detector size. (ii) To optimize one such high resolution, high sensitivity detector and adaptively integrate it into the existing microPET II small animal PET scanner as a 'zoom-in' detector that provides higher spatial resolution and sensitivity in a limited region close to the detector face. The knowledge gained from this project will provide valuable information for building future PET systems with a complete ring of very high-resolution detector arrays and also lay the foundations for utilizing high-resolution detectors in combination with existing PET systems for localized high-resolution imaging.« less

A Submillimeter Resolution PET Prototype Evaluated With an 18F Inkjet Printed Phantom

NASA Astrophysics Data System (ADS)

Schneider, Florian R.; Hohberg, Melanie; Mann, Alexander B.; Paul, Stephan; Ziegler, Sibylle I.

2015-10-01

This work presents a submillimeter resolution PET (Positron Emission Tomography) scanner prototype based on SiPM/MPPC arrays (Silicon Photomultiplier/Multi Pixel Photon Counter). Onto each active area a 1 ×1 ×20 mm3 LYSO (Lutetium-Yttrium-Oxyorthosilicate) scintillator crystal is coupled one-to-one. Two detector modules facing each other in a distance of 10.0 cm have been set up with in total 64 channels that are digitized by SADCs (Sampling Analog to Digital Converters) with 80 MHz, 10 bit resolution and FPGA (Field Programmable Gate Array) based extraction of energy and time information. Since standard phantoms are not sufficient for testing submillimeter resolution at which positron range is an issue, a 18F inkjet printed phantom has been used to explore the limit in spatial resolution. The phantom could be successfully reconstructed with an iterative MLEM (Maximum Likelihood Expectation Maximization) and an analytically calculated system matrix based on the DRF (Detector Response Function) model. The system yields a coincidence time resolution of 4.8 ns FWHM, an energy resolution of 20%-30% FWHM and a spatial resolution of 0.8 mm.

Compact CdZnTe-based gamma camera for prostate cancer imaging

NASA Astrophysics Data System (ADS)

Cui, Yonggang; Lall, Terry; Tsui, Benjamin; Yu, Jianhua; Mahler, George; Bolotnikov, Aleksey; Vaska, Paul; De Geronimo, Gianluigi; O'Connor, Paul; Meinken, George; Joyal, John; Barrett, John; Camarda, Giuseppe; Hossain, Anwar; Kim, Ki Hyun; Yang, Ge; Pomper, Marty; Cho, Steve; Weisman, Ken; Seo, Youngho; Babich, John; LaFrance, Norman; James, Ralph B.

2011-06-01

In this paper, we discuss the design of a compact gamma camera for high-resolution prostate cancer imaging using Cadmium Zinc Telluride (CdZnTe or CZT) radiation detectors. Prostate cancer is a common disease in men. Nowadays, a blood test measuring the level of prostate specific antigen (PSA) is widely used for screening for the disease in males over 50, followed by (ultrasound) imaging-guided biopsy. However, PSA tests have a high falsepositive rate and ultrasound-guided biopsy has a high likelihood of missing small cancerous tissues. Commercial methods of nuclear medical imaging, e.g. PET and SPECT, can functionally image the organs, and potentially find cancer tissues at early stages, but their applications in diagnosing prostate cancer has been limited by the smallness of the prostate gland and the long working distance between the organ and the detectors comprising these imaging systems. CZT is a semiconductor material with wide band-gap and relatively high electron mobility, and thus can operate at room temperature without additional cooling. CZT detectors are photon-electron direct-conversion devices, thus offering high energy-resolution in detecting gamma rays, enabling energy-resolved imaging, and reducing the background of Compton-scattering events. In addition, CZT material has high stopping power for gamma rays; for medical imaging, a few-mm-thick CZT material provides adequate detection efficiency for many SPECT radiotracers. Because of these advantages, CZT detectors are becoming popular for several SPECT medical-imaging applications. Most recently, we designed a compact gamma camera using CZT detectors coupled to an application-specific-integratedcircuit (ASIC). This camera functions as a trans-rectal probe to image the prostate gland from a distance of only 1-5 cm, thus offering higher detection efficiency and higher spatial resolution. Hence, it potentially can detect prostate cancers at their early stages. The performance tests of this camera have been completed. The results show better than 6-mm resolution at a distance of 1 cm. Details of the test results are discussed in this paper.

Design, construction, and evaluation of new high resolution medical imaging detector/systems

NASA Astrophysics Data System (ADS)

Jain, Amit

Increasing need of minimally invasive endovascular image guided interventional procedures (EIGI) for accurate and successful treatment of vascular disease has set a quest for better image quality. Current state of the art detectors are not up to the mark for these complex procedures due to their inherent limitations. Our group has been actively working on the design and construction of a high resolution, region of interest CCD-based X-ray imager for some time. As a part of that endeavor, a Micro-angiographic fluoroscope (MAF) was developed to serve as a high resolution, ROI X-ray imaging detector in conjunction with large lower resolution full field of view (FOV) state-of-the-art x-ray detectors. The newly developed MAF is an indirect x-ray imaging detector capable of providing real-time images with high resolution, high sensitivity, no lag and low instrumentation noise. It consists of a CCD camera coupled to a light image intensifier (LII) through a fiber optic taper. The CsI(Tl) phosphor serving as the front end is coupled to the LII. For this work, the MAF was designed and constructed. The linear system cascade theory was used to evaluate the performance theoretically. Linear system metrics such as MTF and DQE were used to gauge the detector performance experimentally. The capabilities of the MAF as a complete system were tested using generalized linear system metrics. With generalized linear system metrics the effects of finite size focal spot, geometric magnification and the presence of scatter are included in the analysis and study. To minimize the effect of scatter, an anti-scatter grid specially designed for the MAF was also studied. The MAF was compared with the flat panel detector using signal-to-noise ratio and the two dimensional linear system metrics. The signal-to-noise comparison was carried out to point out the effect of pixel size and Point Spread Function of the detector. The two dimensional linear system metrics were used to investigate the comparative performance of both the detectors in similar simulated clinical neuro-vascular conditions. The last part of this work presents a unique quality of the MAF: operation in single photon mode. The successful operation of the MAF was demonstrated with considerable improvement in spatial and contrast resolution over conventional energy integrating mode. The work presented shows the evolution of a high resolution, high sensitivity, and region of interest x-ray imaging detector as an attractive and capable x-ray imager for the betterment of complex EIGI procedures. The capability of single photon counting mode imaging provides the potential for additional uses of the MAF including the possibility of use in dual modality imaging with radionuclide sources as well as x-rays.

A depth-encoding PET detector that uses light sharing and single-ended readout with silicon photomultipliers

NASA Astrophysics Data System (ADS)

Kuang, Zhonghua; Yang, Qian; Wang, Xiaohui; Fu, Xin; Ren, Ning; Sang, Ziru; Wu, San; Zheng, Yunfei; Zhang, Xianming; Hu, Zhanli; Du, Junwei; Liang, Dong; Liu, Xin; Zheng, Hairong; Yang, Yongfeng

2018-02-01

Detectors with depth-encoding capability and good timing resolution are required to develop high-performance whole-body or total-body PET scanners. In this work, depth-encoding PET detectors that use light sharing between two discrete crystals and single-ended readout with silicon photomultipliers (SiPMs) were manufactured and evaluated. The detectors consisted of two unpolished 3  ×  3  ×  20 mm3 LYSO crystals with different coupling materials between them and were read out by Hamamatsu 3  ×  3 mm2 SiPMs with one-to-one coupling. The ratio of the energy of one SiPM to the total energy of two SiPMs was used to measure the depth of interaction (DOI). Detectors with different coupling materials in-between the crystals were measured in the singles mode in an effort to obtain detectors that can provide good DOI resolution. The DOI resolution and energy resolution of three types of detector were measured and the timing resolution was measured for the detector with the best DOI and energy resolution. The optimum detector, with 5 mm optical glue, a 9 mm triangular ESR and a 6 mm rectangular ESR in-between the unpolished crystals, provides a DOI resolution of 2.65 mm, an energy resolution of 10.0% and a timing resolution of 427 ps for events of E  >  400 keV. The detectors simultaneously provide good DOI and timing resolution, and show great promise for the development of high-performance whole-body and total-body PET scanners.

Development of ultrahigh resolution alpha particle imaging detector using 1 mm channel size Si-PM array

NASA Astrophysics Data System (ADS)

Yamamoto, Seiichi; Kawaguchi, Wataru

2018-06-01

For precise distribution measurements of alpha particles, a high-resolution alpha particle imaging detector is required. Although combining a thin scintillator with a silicon photomultiplier (Si-PM) array is a promising method for achieving high resolution, the spatial resolution is limited. Reducing the size of the Si-PM array is a possible approach to improving the spatial resolution of the alpha particle imaging detector. Consequently, we employed a 1 mm channel size Si-PM array combined with a thin ZnS(Ag) sheet to form an alpha particle imaging detector and evaluated the performance. For the developed alpha particle imaging detector, an Si-PM array with 1 mm x 1 mm channel size arranged 8 x 8 was optically coupled to a ZnS(Ag) sheet with a 1-mm-thick light guide between them. The size of the alpha particle imaging detector was 9.5 mm x 9.5 mm. The spatial resolution of the developed alpha particle imaging detector was 0.14 mm FWHM, and the energy resolution was 74% FWHM for 5.5 MeV alpha particles. The uniformity of the imaging detector at the central part of the field of view (FOV) was ±4.7%. The background count rate was 0.06 counts/min. We obtained various high-resolution phantom images for alpha particles with the developed system. We conclude that the developed imaging detector is promising for high-resolution distribution measurements of alpha particles.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ding, Huanjun; Cho, Hyo-Min; Molloi, Sabee, E-mail: symolloi@uci.edu

Purpose: To investigate the feasibility of characterizing a Si strip photon-counting detector using x-ray fluorescence. Methods: X-ray fluorescence was generated by using a pencil beam from a tungsten anode x-ray tube with 2 mm Al filtration. Spectra were acquired at 90° from the primary beam direction with an energy-resolved photon-counting detector based on an edge illuminated Si strip detector. The distances from the source to target and the target to detector were approximately 19 and 11 cm, respectively. Four different materials, containing silver (Ag), iodine (I), barium (Ba), and gadolinium (Gd), were placed in small plastic containers with a diametermore » of approximately 0.7 cm for x-ray fluorescence measurements. Linear regression analysis was performed to derive the gain and offset values for the correlation between the measured fluorescence peak center and the known fluorescence energies. The energy resolutions and charge-sharing fractions were also obtained from analytical fittings of the recorded fluorescence spectra. An analytical model, which employed four parameters that can be determined from the fluorescence calibration, was used to estimate the detector response function. Results: Strong fluorescence signals of all four target materials were recorded with the investigated geometry for the Si strip detector. The average gain and offset of all pixels for detector energy calibration were determined to be 6.95 mV/keV and −66.33 mV, respectively. The detector’s energy resolution remained at approximately 2.7 keV for low energies, and increased slightly at 45 keV. The average charge-sharing fraction was estimated to be 36% within the investigated energy range of 20–45 keV. The simulated detector output based on the proposed response function agreed well with the experimental measurement. Conclusions: The performance of a spectral imaging system using energy-resolved photon-counting detectors is very dependent on the energy calibration of the detector. The proposed x-ray fluorescence technique offers an accurate and efficient way to calibrate the energy response of a photon-counting detector.« less

Soft x-ray submicron imaging detector based on point defects in LiF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baldacchini, G.; Bollanti, S.; Bonfigli, F.

2005-11-15

The use of lithium fluoride (LiF) crystals and films as imaging detectors for EUV and soft-x-ray radiation is discussed. The EUV or soft-x-ray radiation can generate stable color centers, emitting in the visible spectral range an intense fluorescence from the exposed areas. The high dynamic response of the material to the received dose and the atomic scale of the color centers make this detector extremely interesting for imaging at a spatial resolution which can be much smaller than the light wavelength. Experimental results of contact microscopy imaging of test meshes demonstrate a resolution of the order of 400 nm. Thismore » high spatial resolution has been obtained in a wide field of view, up to several mm{sup 2}. Images obtained on different biological samples, as well as an investigation of a soft x-ray laser beam are presented. The behavior of the generated color centers density as a function of the deposited x-ray dose and the advantages of this new diagnostic technique for both coherent and noncoherent EUV sources, compared with CCDs detectors, photographic films, and photoresists are discussed.« less

High-spatial resolution and high-spectral resolution detector for use in the measurement of solar flare hard X-rays

NASA Technical Reports Server (NTRS)

Desai, U. D.; Orwig, Larry E.

1988-01-01

In the areas of high spatial resolution, the evaluation of a hard X-ray detector with 65 micron spatial resolution for operation in the energy range from 30 to 400 keV is proposed. The basic detector is a thick large-area scintillator faceplate, composed of a matrix of high-density scintillating glass fibers, attached to a proximity type image intensifier tube with a resistive-anode digital readout system. Such a detector, combined with a coded-aperture mask, would be ideal for use as a modest-sized hard X-ray imaging instrument up to X-ray energies as high as several hundred keV. As an integral part of this study it was also proposed that several techniques be critically evaluated for X-ray image coding which could be used with this detector. In the area of high spectral resolution, it is proposed to evaluate two different types of detectors for use as X-ray spectrometers for solar flares: planar silicon detectors and high-purity germanium detectors (HPGe). Instruments utilizing these high-spatial-resolution detectors for hard X-ray imaging measurements from 30 to 400 keV and high-spectral-resolution detectors for measurements over a similar energy range would be ideally suited for making crucial solar flare observations during the upcoming maximum in the solar cycle.

Performance analysis of a CsI-based flat panel detector in a cone beam variable resolution x-ray system

NASA Astrophysics Data System (ADS)

Dahi, Bahram; Keyes, Gary S.; Rendon, David A.; DiBianca, Frank A.

2007-03-01

A new Cone-Beam CT (CBCT) system is introduced that uses the concept of Variable Resolution X-ray (VRX) detection, which has previously been demonstrated to significantly increase spatial resolution for small objects. An amorphous silicon Flat Panel Detector (FPD) with a CsI scintillator (PaxScan 2020, Varian, Salt Lake City, UT) is coupled with a micro-focus x-ray tube (35 - 80 kVp, 10 - 250 μA) to form a CBCT. The FPD is installed on a rotating arm that can be adjusted to any angle θ, called the VRX angle, between 90° and 0° with respect to the x-ray direction. A VRX angle of 90° for the detector corresponds to a conventional CBCT whereas a VRX angle of 30° means that the detector is tilted 90° - 30° = 60° from its perpendicular position. Tilting the FPD in this manner reduces both the line-spread function width and the sampling distance by a factor of sin(θ), thereby increasing detector spatial resolution proportionately. An in-house phantom is used to measure the MTF of the reconstructed CT images using different VRX angles. An increase by a factor of 1.67 +/- 0.007 is observed in the MTF cutoff frequency at 30° compared to 90° in images acquired at 75 kVp. Expected theoretical value for this case is 2.0. The new Cone-Beam Variable Resolution X-ray (CB-VRX) CT system is expected to significantly improve the images acquired from small objects - such as small animals - while exploiting the opportunities offered by a conventional CBCT.

Dependence of energy resolution of a plane-parallel HPGe detector on bias voltage upon registration of low-energy X-rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samedov, V. V., E-mail: v-samedov@yandex.ru

2016-12-15

In this study, we theoretically analyze the processes in a plane-parallel high-purity germanium (HPGe) detector. The generating function of factorial moments describing the process of registration of low-energy X-rays by the HPGe detector with consideration of capture of charge carriers by traps is obtained. It is demonstrated that the coefficients of expansion of the average signal amplitude and variance in power series over the quantity inversely proportional to the bias voltage of the detector allow one to determine the Fano factor, the product of the charge carrier lifetime and mobility, and other characteristics of the semiconductor material of the detector.

Efficient phase contrast imaging in STEM using a pixelated detector. Part 1: Experimental demonstration at atomic resolution

DOE PAGES

Pennycook, Timothy J.; Lupini, Andrew R.; Yang, Hao; ...

2014-10-15

In this paper, we demonstrate a method to achieve high efficiency phase contrast imaging in aberration corrected scanning transmission electron microscopy (STEM) with a pixelated detector. The pixelated detector is used to record the Ronchigram as a function of probe position which is then analyzed with ptychography. Ptychography has previously been used to provide super-resolution beyond the diffraction limit of the optics, alongside numerically correcting for spherical aberration. Here we rely on a hardware aberration corrector to eliminate aberrations, but use the pixelated detector data set to utilize the largest possible volume of Fourier space to create high efficiency phasemore » contrast images. The use of ptychography to diagnose the effects of chromatic aberration is also demonstrated. In conclusion, the four dimensional dataset is used to compare different bright field detector configurations from the same scan for a sample of bilayer graphene. Our method of high efficiency ptychography produces the clearest images, while annular bright field produces almost no contrast for an in-focus aberration-corrected probe.« less

TOPEM: A PET-TOF endorectal probe, compatible with MRI for diagnosis and follow up of prostate cancer

NASA Astrophysics Data System (ADS)

Garibaldi, F.; Capuani, S.; Colilli, S.; Cosentino, L.; Cusanno, F.; De Leo, R.; Finocchiaro, P.; Foresta, M.; Giove, F.; Giuliani, F.; Gricia, M.; Loddo, F.; Lucentini, M.; Maraviglia, B.; Meddi, F.; Monno, E.; Musico, P.; Pappalardo, A.; Perrino, R.; Ranieri, A.; Rivetti, A.; Santavenere, F.; Tamma, C.

2013-02-01

Prostate cancer is the most common disease in men and the second leading cause of cancer death. Generic large instruments for diagnosis have sensitivity, spatial resolution, and contrast inferior with respect to dedicated prostate imagers. Multimodality imaging can play a significant role merging anatomical and functional details coming from simultaneous PET and MRI. The TOPEM project has the goal of designing, building, and testing an endorectal PET-TOF MRI probe. The performance is dominated by the detector close to the source. Results from simulation show spatial resolution of ∼1.5 mm for source distances up to 80 mm. The efficiency is significantly improved with respect to the external PET. Mini-detectors have been built and tested. We obtained, for the first time, to our best knowledge, timing resolution of <400 ps and at the same time Depth Of Interaction (DOI) resolution of 1 mm or less.

Fabrication of Ultrasensitive TES Bolometric Detectors for HIRMES

NASA Astrophysics Data System (ADS)

Brown, Ari-David; Brekosky, Regis; Franz, David; Hsieh, Wen-Ting; Kutyrev, Alexander; Mikula, Vilem; Miller, Timothy; Moseley, S. Harvey; Oxborrow, Joseph; Rostem, Karwan; Wollack, Edward

2018-04-01

The high-resolution mid-infrared spectrometer (HIRMES) is a high resolving power (R 100,000) instrument operating in the 25-122 μm spectral range and will fly on board the Stratospheric Observatory for Far-Infrared Astronomy in 2019. Central to HIRMES are its two transition edge sensor (TES) bolometric cameras, an 8 × 16 detector high-resolution array and a 64 × 16 detector low-resolution array. Both types of detectors consist of Mo/Au TES fabricated on leg-isolated Si membranes. Whereas the high-resolution detectors, with a noise equivalent power (NEP) 1.5 × 10-18 W/rt (Hz), are fabricated on 0.45 μm Si substrates, the low-resolution detectors, with NEP 1.0 × 10-17 W/rt (Hz), are fabricated on 1.40 μm Si. Here, we discuss the similarities and differences in the fabrication methodologies used to realize the two types of detectors.

Fabrication of Ultrasensitive Transition Edge Sensor Bolometric Detectors for HIRMES

NASA Technical Reports Server (NTRS)

Brown, Ari-David; Brekosky, Regis; Franz, David; Hsieh, Wen-Ting; Kutyrev, Alexander; Mikula, Vilem; Miller, Timothy; Moseley, S. Harvey; Oxborrow, Joseph; Rostem, Karwan;

Quantitative comparison using Generalized Relative Object Detectability (G-ROD) metrics of an amorphous selenium detector with high resolution Microangiographic Fluoroscopes (MAF) and standard flat panel detectors (FPD).

PubMed

Russ, M; Shankar, A; Jain, A; Setlur Nagesh, S V; Ionita, C N; Scott, C; Karim, K S; Bednarek, D R; Rudin, S

2016-02-27

A novel amorphous selenium (a-Se) direct detector with CMOS readout has been designed, and relative detector performance investigated. The detector features include a 25 μ m pixel pitch, and 1000 μ m thick a-Se layer operating at 10V/ μ m bias field. A simulated detector DQE was determined, and used in comparative calculations of the Relative Object Detectability (ROD) family of prewhitening matched-filter (PWMF) observer and non-prewhitening matched filter (NPWMF) observer model metrics to gauge a-Se detector performance against existing high resolution micro-angiographic fluoroscopic (MAF) detectors and a standard flat panel detector (FPD). The PWMF-ROD or ROD metric compares two x-ray imaging detectors in their relative abilities in imaging a given object by taking the integral over spatial frequencies of the Fourier transform of the detector DQE weighted by an object function, divided by the comparable integral for a different detector. The generalized-ROD (G-ROD) metric incorporates clinically relevant parameters (focal-spot size, magnification, and scatter) to show the degradation in imaging performance for detectors that are part of an imaging chain. Preliminary ROD calculations using simulated spheres as the object predicted superior imaging performance by the a-Se detector as compared to existing detectors. New PWMF-G-ROD and NPWMF-G-ROD results still indicate better performance by the a-Se detector in an imaging chain over all sphere sizes for various focal spot sizes and magnifications, although a-Se performance advantages were degraded by focal spot blurring. Nevertheless, the a-Se technology has great potential to provide breakthrough abilities such as visualization of fine details including of neuro-vascular perforator vessels and of small vascular devices.

Quantitative comparison using generalized relative object detectability (G-ROD) metrics of an amorphous selenium detector with high resolution microangiographic fluoroscopes (MAF) and standard flat panel detectors (FPD)

NASA Astrophysics Data System (ADS)

Russ, M.; Shankar, A.; Jain, A.; Setlur Nagesh, S. V.; Ionita, C. N.; Scott, C.; Karim, K. S.; Bednarek, D. R.; Rudin, S.

2016-03-01

A novel amorphous selenium (a-Se) direct detector with CMOS readout has been designed, and relative detector performance investigated. The detector features include a 25μm pixel pitch, and 1000μm thick a-Se layer operating at 10V/μm bias field. A simulated detector DQE was determined, and used in comparative calculations of the Relative Object Detectability (ROD) family of prewhitening matched-filter (PWMF) observer and non-pre-whitening matched filter (NPWMF) observer model metrics to gauge a-Se detector performance against existing high resolution micro-angiographic fluoroscopic (MAF) detectors and a standard flat panel detector (FPD). The PWMF-ROD or ROD metric compares two x-ray imaging detectors in their relative abilities in imaging a given object by taking the integral over spatial frequencies of the Fourier transform of the detector DQE weighted by an object function, divided by the comparable integral for a different detector. The generalized-ROD (G-ROD) metric incorporates clinically relevant parameters (focal- spot size, magnification, and scatter) to show the degradation in imaging performance for detectors that are part of an imaging chain. Preliminary ROD calculations using simulated spheres as the object predicted superior imaging performance by the a-Se detector as compared to existing detectors. New PWMF-G-ROD and NPWMF-G-ROD results still indicate better performance by the a-Se detector in an imaging chain over all sphere sizes for various focal spot sizes and magnifications, although a-Se performance advantages were degraded by focal spot blurring. Nevertheless, the a-Se technology has great potential to provide break- through abilities such as visualization of fine details including of neuro-vascular perforator vessels and of small vascular devices.

Quantitative comparison using Generalized Relative Object Detectability (G-ROD) metrics of an amorphous selenium detector with high resolution Microangiographic Fluoroscopes (MAF) and standard flat panel detectors (FPD)

PubMed Central

Russ, M.; Shankar, A.; Jain, A.; Setlur Nagesh, S. V.; Ionita, C. N.; Scott, C.; Karim, K. S.; Bednarek, D. R.; Rudin, S.

2017-01-01

A novel amorphous selenium (a-Se) direct detector with CMOS readout has been designed, and relative detector performance investigated. The detector features include a 25μm pixel pitch, and 1000μm thick a-Se layer operating at 10V/μm bias field. A simulated detector DQE was determined, and used in comparative calculations of the Relative Object Detectability (ROD) family of prewhitening matched-filter (PWMF) observer and non-prewhitening matched filter (NPWMF) observer model metrics to gauge a-Se detector performance against existing high resolution micro-angiographic fluoroscopic (MAF) detectors and a standard flat panel detector (FPD). The PWMF-ROD or ROD metric compares two x-ray imaging detectors in their relative abilities in imaging a given object by taking the integral over spatial frequencies of the Fourier transform of the detector DQE weighted by an object function, divided by the comparable integral for a different detector. The generalized-ROD (G-ROD) metric incorporates clinically relevant parameters (focal-spot size, magnification, and scatter) to show the degradation in imaging performance for detectors that are part of an imaging chain. Preliminary ROD calculations using simulated spheres as the object predicted superior imaging performance by the a-Se detector as compared to existing detectors. New PWMF-G-ROD and NPWMF-G-ROD results still indicate better performance by the a-Se detector in an imaging chain over all sphere sizes for various focal spot sizes and magnifications, although a-Se performance advantages were degraded by focal spot blurring. Nevertheless, the a-Se technology has great potential to provide breakthrough abilities such as visualization of fine details including of neuro-vascular perforator vessels and of small vascular devices. PMID:28615795

Dynamic granularity of imaging systems

DOE PAGES

Geissel, Matthias; Smith, Ian C.; Shores, Jonathon E.; ...

2015-11-04

Imaging systems that include a specific source, imaging concept, geometry, and detector have unique properties such as signal-to-noise ratio, dynamic range, spatial resolution, distortions, and contrast. Some of these properties are inherently connected, particularly dynamic range and spatial resolution. It must be emphasized that spatial resolution is not a single number but must be seen in the context of dynamic range and consequently is better described by a function or distribution. We introduce the “dynamic granularity” G dyn as a standardized, objective relation between a detector’s spatial resolution (granularity) and dynamic range for complex imaging systems in a given environmentmore » rather than the widely found characterization of detectors such as cameras or films by themselves. We found that this relation can partly be explained through consideration of the signal’s photon statistics, background noise, and detector sensitivity, but a comprehensive description including some unpredictable data such as dust, damages, or an unknown spectral distribution will ultimately have to be based on measurements. Measured dynamic granularities can be objectively used to assess the limits of an imaging system’s performance including all contributing noise sources and to qualify the influence of alternative components within an imaging system. Our article explains the construction criteria to formulate a dynamic granularity and compares measured dynamic granularities for different detectors used in the X-ray backlighting scheme employed at Sandia’s Z-Backlighter facility.« less

Oblique reconstructions in tomosynthesis. II. Super-resolution

PubMed Central

Acciavatti, Raymond J.; Maidment, Andrew D. A.

2013-01-01

Purpose: In tomosynthesis, super-resolution has been demonstrated using reconstruction planes parallel to the detector. Super-resolution allows for subpixel resolution relative to the detector. The purpose of this work is to develop an analytical model that generalizes super-resolution to oblique reconstruction planes. Methods: In a digital tomosynthesis system, a sinusoidal test object is modeled along oblique angles (i.e., “pitches”) relative to the plane of the detector in a 3D divergent-beam acquisition geometry. To investigate the potential for super-resolution, the input frequency is specified to be greater than the alias frequency of the detector. Reconstructions are evaluated in an oblique plane along the extent of the object using simple backprojection (SBP) and filtered backprojection (FBP). By comparing the amplitude of the reconstruction against the attenuation coefficient of the object at various frequencies, the modulation transfer function (MTF) is calculated to determine whether modulation is within detectable limits for super-resolution. For experimental validation of super-resolution, a goniometry stand was used to orient a bar pattern phantom along various pitches relative to the breast support in a commercial digital breast tomosynthesis system. Results: Using theoretical modeling, it is shown that a single projection image cannot resolve a sine input whose frequency exceeds the detector alias frequency. The high frequency input is correctly visualized in SBP or FBP reconstruction using a slice along the pitch of the object. The Fourier transform of this reconstructed slice is maximized at the input frequency as proof that the object is resolved. Consistent with the theoretical results, experimental images of a bar pattern phantom showed super-resolution in oblique reconstructions. At various pitches, the highest frequency with detectable modulation was determined by visual inspection of the bar patterns. The dependency of the highest detectable frequency on pitch followed the same trend as the analytical model. It was demonstrated that super-resolution is not achievable if the pitch of the object approaches 90°, corresponding to the case in which the test frequency is perpendicular to the breast support. Only low frequency objects are detectable at pitches close to 90°. Conclusions: This work provides a platform for investigating super-resolution in oblique reconstructions for tomosynthesis. In breast imaging, this study should have applications in visualizing microcalcifications and other subtle signs of cancer. PMID:24320445

X-ray and gamma ray detector readout system

DOEpatents

Tumer, Tumay O; Clajus, Martin; Visser, Gerard

2010-10-19

A readout electronics scheme is under development for high resolution, compact PET (positron emission tomography) imagers based on LSO (lutetium ortho-oxysilicate, Lu.sub.2SiO.sub.5) scintillator and avalanche photodiode (APD) arrays. The key is to obtain sufficient timing and energy resolution at a low power level, less than about 30 mW per channel, including all required functions. To this end, a simple leading edge level crossing discriminator is used, in combination with a transimpedance preamplifier. The APD used has a gain of order 1,000, and an output noise current of several pA/ Hz, allowing bipolar technology to be used instead of CMOS, for increased speed and power efficiency. A prototype of the preamplifier and discriminator has been constructed, achieving timing resolution of 1.5 ns FWHM, 2.7 ns full width at one tenth maximum, relative to an LSO/PMT detector, and an energy resolution of 13.6% FWHM at 511 keV, while operating at a power level of 22 mW per channel. Work is in progress towards integration of this preamplifier and discriminator with appropriate coincidence logic and amplitude measurement circuits in an ASIC suitable for a high resolution compact PET instrument. The detector system and/or ASIC can also be used for many other applications for medical to industrial imaging.

The Road to the Common PET/CT Detector

NASA Astrophysics Data System (ADS)

Nassalski, Antoni; Moszynski, Marek; Szczesniak, Tomasz; Wolski, Dariusz; Batsch, Tadeusz

2007-10-01

Growing interest in the development of dual modality positron emission/X-rays tomography (PET/CT) systems prompts researchers to face a new challenge: to acquire both the anatomical and functional information in the same measurement, simultaneously using the same detection system and electronics. The aim of this work was to study a detector consisting of LaBr3, LSO or LYSO pixel crystals coupled to an avalanche photodiode (APD). The measurements covered tests of the detectors in PET and CT modes, respectively. The measurements included the determination of light output, energy resolution, the non-proportionality of the light yield and the time resolution for 511 keV annihilation quanta; analysis also included characterizing the PET detector, and determining the dependence of counting rate versus mean current of the APD in the X-ray detection. In the present experiment, the use of counting and current modes in the CT detection increases the dynamic range of the measured dose of X-rays by a factor of 20, compared to the counting mode alone.

Image charge multi-role and function detectors

NASA Astrophysics Data System (ADS)

Milnes, James; Lapington, Jon S.; Jagutzki, Ottmar; Howorth, Jon

2009-06-01

The image charge technique used with microchannel plate imaging tubes provides several operational and practical benefits by serving to isolate the electronic image readout from the detector. The simple dielectric interface between detector and readout provides vacuum isolation and no vacuum electrical feed-throughs are required. Since the readout is mechanically separate from the detector, an image tube of generic design can be simply optimised for various applications by attaching it to different readout devices and electronics. We present imaging performance results using a single image tube with a variety of readout devices suited to differing applications: (a) A four electrode charge division tetra wedge anode, optimised for best spatial resolution in photon counting mode. (b) A cross delay line anode, enabling higher count rate, and the possibility of discriminating near co-incident events, and an event timing resolution of better than 1 ns. (c) A multi-anode readout connected, either to a multi-channel oscilloscope for analogue measurements of fast optical pulses, or alternately, to a multi-channel time correlated single photon counting (TCSPC) card.

A compact high resolution flat panel PET detector based on the new 4-side buttable MPPC for biomedical applications.

PubMed

Wang, Qiang; Wen, Jie; Ravindranath, Bosky; O'Sullivan, Andrew W; Catherall, David; Li, Ke; Wei, Shouyi; Komarov, Sergey; Tai, Yuan-Chuan

2015-09-11

Compact high-resolution panel detectors using virtual pinhole (VP) PET geometry can be inserted into existing clinical or pre-clinical PET systems to improve regional spatial resolution and sensitivity. Here we describe a compact panel PET detector built using the new Though Silicon Via (TSV) multi-pixel photon counters (MPPC) detector. This insert provides high spatial resolution and good timing performance for multiple bio-medical applications. Because the TSV MPPC design eliminates wire bonding and has a package dimension which is very close to the MPPC's active area, it is 4-side buttable. The custom designed MPPC array (based on Hamamatsu S12641-PA-50(x)) used in the prototype is composed of 4 × 4 TSV-MPPC cells with a 4.46 mm pitch in both directions. The detector module has 16 × 16 lutetium yttrium oxyorthosilicate (LYSO) crystal array, with each crystal measuring 0.92 × 0.92 × 3 mm 3 with 1.0 mm pitch. The outer diameter of the detector block is 16.8 × 16.8 mm 2 . Thirty-two such blocks will be arranged in a 4 × 8 array with 1 mm gaps to form a panel detector with detection area around 7 cm × 14 cm in the full-size detector. The flood histogram acquired with Ge-68 source showed excellent crystal separation capability with all 256 crystals clearly resolved. The detector module's mean, standard deviation, minimum (best) and maximum (worst) energy resolution were 10.19%, +/-0.68%, 8.36% and 13.45% FWHM, respectively. The measured coincidence time resolution between the block detector and a fast reference detector (around 200 ps single photon timing resolution) was 0.95 ns. When tested with Siemens Cardinal electronics the performance of the detector blocks remain consistent. These results demonstrate that the TSV-MPPC is a promising photon sensor for use in a flat panel PET insert composed of many high resolution compact detector modules.

Image science team

NASA Technical Reports Server (NTRS)

Ando, K.

1982-01-01

A substantial technology base of solid state pushbroom sensors exists and is in the process of further evolution at both GSFC and JPL. Technologies being developed relate to short wave infrared (SWIR) detector arrays; HgCdTe hybrid detector arrays; InSb linear and area arrays; passive coolers; spectral beam splitters; the deposition of spectral filters on detector arrays; and the functional design of the shuttle/space platform imaging spectrometer (SIS) system. Spatial and spectral characteristics of field, aircraft and space multispectral sensors are summaried. The status, field of view, and resolution of foreign land observing systems are included.

Multibeam interferometric illumination as the primary source of resolution in optical microscopy

NASA Astrophysics Data System (ADS)

Ryu, J.; Hong, S. S.; Horn, B. K. P.; Freeman, D. M.; Mermelstein, M. S.

2006-04-01

High-resolution images of a fluorescent target were obtained using a low-resolution optical detector by illuminating the target with interference patterns produced with 31 coherent beams. The beams were arranged in a cone with 78° half angle to produce illumination patterns consistent with a numerical aperture of 0.98. High-resolution images were constructed from low-resolution images taken with 930 different illumination patterns. Results for optical detectors with numerical apertures of 0.1 and 0.2 were similar, demonstrating that the resolution is primarily determined by the illuminator and not by the low-resolution detector. Furthermore, the long working distance, large depth of field, and large field of view of the low-resolution detector are preserved.

Theoretical consideration of the energy resolution in planar HPGe detectors for low energy X-rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samedov, Victor V.

In this work, theoretical consideration of the processes in planar High Purity Ge (HPGe) detectors for low energy X-rays using the random stochastic processes formalism was carried out. Using the random stochastic processes formalism, the generating function of the processes of X-rays registration in a planar HPGe detector was derived. The power serial expansions of the detector amplitude and the variance in terms of the inverse bias voltage were derived. The coefficients of these expansions allow determining the Fano factor, electron mobility lifetime product, nonuniformity of the trap density, and other characteristics of the semiconductor material. (authors)

Abstract ID: 242 Simulation of a Fast Timing Micro-Pattern Gaseous Detector for TOF-PET.

PubMed

Radogna, Raffaella; Verwilligen, Piet

2018-01-01

Micro-Pattern Gas Detectors (MPGDs) are a new generation of gaseous detectors that have been developed thanks to advances in micro-structure technology. The main features of the MPGDs are: high rate capability (>50 MHz/cm 2 ); excellent spatial resolution (down to 50 μm); good time resolution (down to 3 ns); reduced radiation length, affordable costs, and possible flexible geometries. A new detector layout has been recently proposed that aims at combining both the high spatial resolution and high rate capability (100 MHz/cm 2 ) of the current state-of-the-art MPGDs with a high time resolution. This new type of MPGD is named the Fast Timing MPGD (FTM) detector [1,2]. The FTM developed for detecting charged particles can potentially reach sub-millimeter spatial resolution and 100 ps time resolution. This contribution introduces a Fast Timing MPGD technology optimized to detect photons, as an innovative PET imaging detector concept and emphases the importance of full detector simulation to guide the design of the detector geometry. The design and development of a new FTM, combining excellent time and spatial resolution, while exploiting the advantages of a reasonable energy resolution, will be a boost for the design of affordable TOF-PET scanner with improved image contrast. The use of such an affordable gas detector allows to instrument large areas in a cost-effective way, and to increase in image contrast for shorter scanning times (lowering the risk for the patient) and better diagnosis of the disease. In this report a dedicated simulation study is performed to optimize the detector design in the contest of the INFN project MPGD-Fatima. Results are obtained with ANSYS, COMSOL, GARFIELD++ and GEANT4 simulation tools. The final detector layout will be trade-off between fast time and good energy resolution. Copyright © 2017.

Performance evaluation of a high-resolution brain PET scanner using four-layer MPPC DOI detectors.

PubMed

Watanabe, Mitsuo; Saito, Akinori; Isobe, Takashi; Ote, Kibo; Yamada, Ryoko; Moriya, Takahiro; Omura, Tomohide

2017-08-18

A high-resolution positron emission tomography (PET) scanner, dedicated to brain studies, was developed and its performance was evaluated. A four-layer depth of interaction detector was designed containing five detector units axially lined up per layer board. Each of the detector units consists of a finely segmented (1.2 mm) LYSO scintillator array and an 8  ×  8 array of multi-pixel photon counters. Each detector layer has independent front-end and signal processing circuits, and the four detector layers are assembled as a detector module. The new scanner was designed to form a detector ring of 430 mm diameter with 32 detector modules and 168 detector rings with a 1.2 mm pitch. The total crystal number is 655 360. The transaxial and axial field of views (FOVs) are 330 mm in diameter and 201.6 mm, respectively, which are sufficient to measure a whole human brain. The single-event data generated at each detector module were transferred to the data acquisition servers through optical fiber cables. The single-event data from all detector modules were merged and processed to create coincidence event data in on-the-fly software in the data acquisition servers. For image reconstruction, the high-resolution mode (HR-mode) used a 1.2 mm 2 crystal segment size and the high-speed mode (HS-mode) used a 4.8 mm 2 size by collecting 16 crystal segments of 1.2 mm each to reduce the computational cost. The performance of the brain PET scanner was evaluated. For the intrinsic spatial resolution of the detector module, coincidence response functions of the detector module pair, which faced each other at various angles, were measured by scanning a 0.25 mm diameter 22 Na point source. The intrinsic resolutions were obtained with 1.08 mm full width at half-maximum (FWHM) and 1.25 mm FWHM on average at 0 and 22.5 degrees in the first layer pair, respectively. The system spatial resolutions were less than 1.0 mm FWHM throughout the whole FOV, using a list-mode dynamic RAMLA (LM-DRAMA). The system sensitivity was 21.4 cps kBq -1 as measured using an 18 F line source aligned with the center of the transaxial FOV. High count rate capability was evaluated using a cylindrical phantom (20 cm diameter  ×  70 cm length), resulting in 249 kcps in true and 27.9 kcps at 11.9 kBq ml -1 at the peak count in a noise equivalent count rate (NECR_2R). Single-event data acquisition and on-the-fly software coincidence detection performed well, exceeding 25 Mcps and 2.3 Mcps for single and coincidence count rates, respectively. Using phantom studies, we also demonstrated its imaging capabilities by means of a 3D Hoffman brain phantom and an ultra-micro hot-spot phantom. The images obtained were of acceptable quality for high-resolution determination. As clinical and pre-clinical studies, we imaged brains of a human and of small animals.

Performance evaluation of a high-resolution brain PET scanner using four-layer MPPC DOI detectors

NASA Astrophysics Data System (ADS)

Watanabe, Mitsuo; Saito, Akinori; Isobe, Takashi; Ote, Kibo; Yamada, Ryoko; Moriya, Takahiro; Omura, Tomohide

2017-09-01

A high-resolution positron emission tomography (PET) scanner, dedicated to brain studies, was developed and its performance was evaluated. A four-layer depth of interaction detector was designed containing five detector units axially lined up per layer board. Each of the detector units consists of a finely segmented (1.2 mm) LYSO scintillator array and an 8  ×  8 array of multi-pixel photon counters. Each detector layer has independent front-end and signal processing circuits, and the four detector layers are assembled as a detector module. The new scanner was designed to form a detector ring of 430 mm diameter with 32 detector modules and 168 detector rings with a 1.2 mm pitch. The total crystal number is 655 360. The transaxial and axial field of views (FOVs) are 330 mm in diameter and 201.6 mm, respectively, which are sufficient to measure a whole human brain. The single-event data generated at each detector module were transferred to the data acquisition servers through optical fiber cables. The single-event data from all detector modules were merged and processed to create coincidence event data in on-the-fly software in the data acquisition servers. For image reconstruction, the high-resolution mode (HR-mode) used a 1.2 mm2 crystal segment size and the high-speed mode (HS-mode) used a 4.8 mm2 size by collecting 16 crystal segments of 1.2 mm each to reduce the computational cost. The performance of the brain PET scanner was evaluated. For the intrinsic spatial resolution of the detector module, coincidence response functions of the detector module pair, which faced each other at various angles, were measured by scanning a 0.25 mm diameter 22Na point source. The intrinsic resolutions were obtained with 1.08 mm full width at half-maximum (FWHM) and 1.25 mm FWHM on average at 0 and 22.5 degrees in the first layer pair, respectively. The system spatial resolutions were less than 1.0 mm FWHM throughout the whole FOV, using a list-mode dynamic RAMLA (LM-DRAMA). The system sensitivity was 21.4 cps kBq-1 as measured using an 18F line source aligned with the center of the transaxial FOV. High count rate capability was evaluated using a cylindrical phantom (20 cm diameter  ×  70 cm length), resulting in 249 kcps in true and 27.9 kcps at 11.9 kBq ml-1 at the peak count in a noise equivalent count rate (NECR_2R). Single-event data acquisition and on-the-fly software coincidence detection performed well, exceeding 25 Mcps and 2.3 Mcps for single and coincidence count rates, respectively. Using phantom studies, we also demonstrated its imaging capabilities by means of a 3D Hoffman brain phantom and an ultra-micro hot-spot phantom. The images obtained were of acceptable quality for high-resolution determination. As clinical and pre-clinical studies, we imaged brains of a human and of small animals.

Alpha-ray spectrometry at high temperature by using a compound semiconductor detector.

PubMed

Ha, Jang Ho; Kim, Han Soo

2013-11-01

The use of conventional radiation detectors in harsh environments is limited by radiation damage to detector materials and by temperature constraints. We fabricated a wide-band gap semiconductor radiation detector based on silicon carbide. All the detector components were considered for an application in a high temperature environment like a nuclear reactor core. The radiation response, especially to alpha particles, was measured using an (241)Am source at variable operating voltages at room temperature in the air. The temperature on detector was controlled from 30°C to 250°C. The alpha-particle spectra were measured at zero bias operation. Even though the detector is operated at high temperature, the energy resolution as a function of temperature is almost constant within 3.5% deviation. Copyright © 2013 Elsevier Ltd. All rights reserved.

Characteristic of x-ray tomography performance using CdTe timepix detector

NASA Astrophysics Data System (ADS)

Zain, R. M.; O'Shea, V.; Maneuski, D.

2017-01-01

X-ray Computed Tomography (CT) is a non-destructive technique for visualizing interior features within solid objects, and for obtaining digital information on their 3-D geometries and properties. The selection of CdTe Timepix detector has a sufficient performance of imaging detector is based on quality of detector performance and energy resolution. The study of Modulation Transfer Function (MTF) shows a 70% contrast at 4 lp/mm was achieved for the 55 µm pixel pitch detector with the 60 kVp X-ray tube and 5 keV noise level. No significant degradation in performance was observed for X-ray tube energies of 20 - 60 keV. The paper discusses the application of the CdTe Timepix detector to produce a good quality image of X-ray tomography imaging.

Achieving high spatial resolution using a microchannel plate detector with an economic and scalable approach

NASA Astrophysics Data System (ADS)

Wiggins, B. B.; deSouza, Z. O.; Vadas, J.; Alexander, A.; Hudan, S.; deSouza, R. T.

2017-11-01

A second generation position-sensitive microchannel plate detector using the induced signal approach has been realized. This detector is presently capable of measuring the incident position of electrons, photons, or ions. To assess the spatial resolution, the masked detector was illuminated by electrons. The initial, measured spatial resolution of 276 μm FWHM was improved by requiring a minimum signal amplitude on the anode and by employing digital signal processing techniques. The resulting measured spatial resolution of 119 μm FWHM corresponds to an intrinsic resolution of 98 μm FWHM when the effect of the finite slit width is de-convoluted. This measurement is a substantial improvement from the last reported spatial resolution of 466 μm FWHM using the induced signal approach. To understand the factors that limit the measured resolution, the performance of the detector is simulated.

Resolution Properties of a Calcium Tungstate (CaWO4) Screen Coupled to a CMOS Imaging Detector

NASA Astrophysics Data System (ADS)

Koukou, Vaia; Martini, Niki; Valais, Ioannis; Bakas, Athanasios; Kalyvas, Nektarios; Lavdas, Eleftherios; Fountos, George; Kandarakis, Ioannis; Michail, Christos

2017-11-01

The aim of the current work was to assess the resolution properties of a calcium tungstate (CaWO4) screen (screen coating thickness: 50.09 mg/cm2, actual thickness: 167.2 μm) coupled to a high resolution complementary metal oxide semiconductor (CMOS) digital imaging sensor. A 2.7x3.6 cm2 CaWO4 sample was extracted from an Agfa Curix universal screen and was coupled directly with the active area of the active pixel sensor (APS) CMOS sensor. Experiments were performed following the new IEC 62220-1-1:2015 International Standard, using an RQA-5 beam quality. Resolution was assessed in terms of the Modulation Transfer Function (MTF), using the slanted-edge method. The CaWO4/CMOS detector configuration was found with linear response, in the exposure range under investigation. The final MTF was obtained through averaging the oversampled edge spread function (ESF), using a custom-made software developed by our team, according to the IEC 62220-1-1:2015. Considering the renewed interest in calcium tungstate for various applications, along with the resolution results of this work, CaWO4 could be also considered for use in X-ray imaging devices such as charged-coupled devices (CCD) and CMOS.

Performance of a Medipix3RX spectroscopic pixel detector with a high resistivity gallium arsenide sensor.

PubMed

Hamann, Elias; Koenig, Thomas; Zuber, Marcus; Cecilia, Angelica; Tyazhev, Anton; Tolbanov, Oleg; Procz, Simon; Fauler, Alex; Baumbach, Tilo; Fiederle, Michael

2015-03-01

High resistivity gallium arsenide is considered a suitable sensor material for spectroscopic X-ray imaging detectors. These sensors typically have thicknesses between a few hundred μm and 1 mm to ensure a high photon detection efficiency. However, for small pixel sizes down to several tens of μm, an effect called charge sharing reduces a detector's spectroscopic performance. The recently developed Medipix3RX readout chip overcomes this limitation by implementing a charge summing circuit, which allows the reconstruction of the full energy information of a photon interaction in a single pixel. In this work, we present the characterization of the first Medipix3RX detector assembly with a 500 μm thick high resistivity, chromium compensated gallium arsenide sensor. We analyze its properties and demonstrate the functionality of the charge summing mode by means of energy response functions recorded at a synchrotron. Furthermore, the imaging properties of the detector, in terms of its modulation transfer functions and signal-to-noise ratios, are investigated. After more than one decade of attempts to establish gallium arsenide as a sensor material for photon counting detectors, our results represent a breakthrough in obtaining detector-grade material. The sensor we introduce is therefore suitable for high resolution X-ray imaging applications.

WE-EF-303-08: Proton Radiography Using Pencil Beam Scanning and Novel Micromegas Detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dolney, D; Lustig, R; Teo, B

Purpose: While the energy of therapeutic proton beams can be adjusted to penetrate to any given depth in water, range uncertainties arise in patients due in part to imprecise knowledge of the stopping power of protons in human tissues. Proton radiography is one approach to reduce the beam range uncertainty, thereby allowing for a reduction in treatment margins and dose escalation. Methods: The authors have adapted a novel detector technology based on Micromesh Gaseous Structure (“Micromegas”) for proton therapy beams and have demonstrated fine spatial and time resolution of magnetically scanned proton pencil beams, as well as wide dynamic rangemore » for dosimetry. In this work, proton radiographs were obtained using Micromegas 2D planes positioned downstream of solid water assemblies. The position-sensitive monitor chambers in the IBA proton delivery nozzle provide the beam entrance position. Results: Radiography with Micromegas detectors and actively scanned beams provide spatial resolution of up to 300 µm and water-equivalent thickness (WET) resolution as good as 0.02% (60 µm out of 31 cm total thickness), with the dose delivered to the patient kept below 2 cGy. The spatial resolution as a function of sample rate and number of delivered protons is found to be near the theoretical Cramer-Rao lower bound. Using the CR bound, we argue that the imaging dose could be further lowered to 1 mGy, while still achieving sub-mm spatial resolution, by relatively simple instrumentation upgrades and beam delivery modifications. Conclusion: For proton radiography, high spatial and WET resolution can be achieved, with minimal additional dose to patient, by using magnetically scanned proton pencil beams and Micromegas detectors.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Loughran, B; Singh, V; Jain, A

Purpose: Although generalized linear system analytic metrics such as GMTF and GDQE can evaluate performance of the whole imaging system including detector, scatter and focal-spot, a simplified task-specific measured metric may help to better compare detector systems. Methods: Low quantum-noise images of a neuro-vascular stent with a modified ANSI head phantom were obtained from the average of many exposures taken with the high-resolution Micro-Angiographic Fluoroscope (MAF) and with a Flat Panel Detector (FPD). The square of the Fourier Transform of each averaged image, equivalent to the measured product of the system GMTF and the object function in spatial-frequency space, wasmore » then divided by the normalized noise power spectra (NNPS) for each respective system to obtain a task-specific generalized signal-to-noise ratio. A generalized measured relative object detectability (GM-ROD) was obtained by taking the ratio of the integral of the resulting expressions for each detector system to give an overall metric that enables a realistic systems comparison for the given detection task. Results: The GM-ROD provides comparison of relative performance of detector systems from actual measurements of the object function as imaged by those detector systems. This metric includes noise correlations and spatial frequencies relevant to the specific object. Additionally, the integration bounds for the GM-ROD can be selected to emphasis the higher frequency band of each detector if high-resolution image details are to be evaluated. Examples of this new metric are discussed with a comparison of the MAF to the FPD for neuro-vascular interventional imaging. Conclusion: The GM-ROD is a new direct-measured task-specific metric that can provide clinically relevant comparison of the relative performance of imaging systems. Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation.« less

Development of TlBr detectors for PET imaging.

PubMed

Ariño-Estrada, Gerard; Du, Junwei; Kim, Hadong; Cirignano, Leonard J; Shah, Kanai S; Cherry, Simon R; Mitchell, Gregory S

2018-05-04

Thallium bromide (TlBr) is a promising semiconductor detector material for positron emission tomography (PET) because it can offer very good energy resolution and 3-D segmentation capabilities, and it also provides detection efficiency surpassing that of commonly used scintillators. Energy, timing, and spatial resolution were measured for thin (<1 mm) TlBr detectors. The energy and timing resolution were measured simultaneously for the same planar 0.87 mm-thick TlBr device. An energy resolution of (6.41.3)% at 511 keV was achieved at -400 V bias voltage and at room temperature. A timing resolution of (27.84.1) ns FWHM was achieved for the same operating conditions when appropriate energy gating was applied. The intrinsic spatial resolution was measured to be 0.9 mm FWHM for a TlBr detector with metallic strip contacts of 0.5 mm pitch. As material properties improve, higher bias voltage should improve timing performance. A stack of thin detectors with finely segmented readout can create a modular detector with excellent energy and spatial resolution for PET applications. . © 2018 Institute of Physics and Engineering in Medicine.

Characterization of energy response for photon-counting detectors using x-ray fluorescence

PubMed Central

Ding, Huanjun; Cho, Hyo-Min; Barber, William C.; Iwanczyk, Jan S.; Molloi, Sabee

2014-01-01

Purpose: To investigate the feasibility of characterizing a Si strip photon-counting detector using x-ray fluorescence. Methods: X-ray fluorescence was generated by using a pencil beam from a tungsten anode x-ray tube with 2 mm Al filtration. Spectra were acquired at 90° from the primary beam direction with an energy-resolved photon-counting detector based on an edge illuminated Si strip detector. The distances from the source to target and the target to detector were approximately 19 and 11 cm, respectively. Four different materials, containing silver (Ag), iodine (I), barium (Ba), and gadolinium (Gd), were placed in small plastic containers with a diameter of approximately 0.7 cm for x-ray fluorescence measurements. Linear regression analysis was performed to derive the gain and offset values for the correlation between the measured fluorescence peak center and the known fluorescence energies. The energy resolutions and charge-sharing fractions were also obtained from analytical fittings of the recorded fluorescence spectra. An analytical model, which employed four parameters that can be determined from the fluorescence calibration, was used to estimate the detector response function. Results: Strong fluorescence signals of all four target materials were recorded with the investigated geometry for the Si strip detector. The average gain and offset of all pixels for detector energy calibration were determined to be 6.95 mV/keV and −66.33 mV, respectively. The detector’s energy resolution remained at approximately 2.7 keV for low energies, and increased slightly at 45 keV. The average charge-sharing fraction was estimated to be 36% within the investigated energy range of 20–45 keV. The simulated detector output based on the proposed response function agreed well with the experimental measurement. Conclusions: The performance of a spectral imaging system using energy-resolved photon-counting detectors is very dependent on the energy calibration of the detector. The proposed x-ray fluorescence technique offers an accurate and efficient way to calibrate the energy response of a photon-counting detector. PMID:25471962

Development of a compact E ? B microchannel plate detector for beam imaging

DOE PAGES

Wiggins, B. B.; Singh, Varinderjit; Vadas, J.; ...

2017-06-17

A beam imaging detector was developed by coupling a multi-strip anode with delay line readout to an E×B microchannel plate (MCP) detector. This detector is capable of measuring the incident position of the beam particles in one-dimension. To assess the spatial resolution, the detector was illuminated by an α-source with an intervening mask that consists of a series of precisely-machined slits. The measured spatial resolution was 520 um source FWHM, which was improved to 413 um FWHM by performing an FFT of the signals, rejecting spurious signals on the delay line, and requiring a minimum signal amplitude. This measured spatialmore » resolution of 413 um FWHM corresponds to an intrinsic resolution of 334 um FWHM when the effect of the finite slit width is de-convoluted. To understand the measured resolution, the performance of the detector is simulated with the ion-trajectory code SIMION.« less

Development of a compact E ? B microchannel plate detector for beam imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiggins, B. B.; Singh, Varinderjit; Vadas, J.

A beam imaging detector was developed by coupling a multi-strip anode with delay line readout to an E×B microchannel plate (MCP) detector. This detector is capable of measuring the incident position of the beam particles in one-dimension. To assess the spatial resolution, the detector was illuminated by an α-source with an intervening mask that consists of a series of precisely-machined slits. The measured spatial resolution was 520 um source FWHM, which was improved to 413 um FWHM by performing an FFT of the signals, rejecting spurious signals on the delay line, and requiring a minimum signal amplitude. This measured spatialmore » resolution of 413 um FWHM corresponds to an intrinsic resolution of 334 um FWHM when the effect of the finite slit width is de-convoluted. To understand the measured resolution, the performance of the detector is simulated with the ion-trajectory code SIMION.« less

Further developments of series-connected superconducting tunnel junction to radiation detection

NASA Astrophysics Data System (ADS)

Kurakado, Masahiko; Ohsawa, Daisuke; Katano, Rintaro; Ito, Shin; Isozumi, Yasuhito

1997-10-01

One of the promising radiation detection devices for various practical applications is the series-connected superconducting tunnel junction (STJ) detector. In this article, interesting topics of the detectors are described since our previous work: e.g., more than two order higher detection efficiency compared with single STJ detectors, high count rate detection, and position resolution. Detectors were cooled to 0.35-0.4 K by means of a convenient 3He cryostat. The 5.9 and 6.5 keV x rays from 55Fe are separated by a detector specially designed for x-ray detection. The possible count rate of the series-junction detector estimated from the shaping-time constant applied in the measurements is high, e.g., over 104 counts per second. A series-junction detector equipped with a position sensing mechanism has shown a position resolution of about 35 μm in a sensing area with a radius of 1.1 mm. The position resolution of series junctions improves the energy resolution. A new type series-connected STJ detector is also proposed, i.e., the dispersed multitrap series-junction detector, for further improvement of detection efficiency and energy resolution.

Prototyping of Silicon Strip Detectors for the Inner Tracker of the ALICE Experiment

NASA Astrophysics Data System (ADS)

Sokolov, Oleksiy

2006-04-01

The ALICE experiment at CERN will study heavy ion collisions at a center-of-mass energy 5.5˜TeV per nucleon. Particle tracking around the interaction region at radii r<45 cm is done by the Inner Tracking System (ITS), consisting of six cylindrical layers of silicon detectors. The outer two layers of the ITS use double-sided silicon strip detectors. This thesis focuses on testing of these detectors and performance studies of the detector module prototypes at the beam test. Silicon strip detector layers will require about 20 thousand HAL25 front-end readout chips and about 3.5 thousand hybrids each containing 6 HAL25 chips. During the assembly procedure, chips are bonded on a patterned TAB aluminium microcables which connect to all the chip input and output pads, and then the chips are assembled on the hybrids. Bonding failures at the chip or hybrid level may either render the component non-functional or deteriorate its the performance such that it can not be used for the module production. After each bonding operation, the component testing is done to reject the non-functional or poorly performing chips and hybrids. The LabView-controlled test station for this operation has been built at Utrecht University and was successfully used for mass production acceptance tests of chips and hybrids at three production labs. The functionality of the chip registers, bonding quality and analogue functionality of the chips and hybrids are addressed in the test. The test routines were optimized to minimize the testing time to make sure that testing is not a bottleneck of the mass production. For testing of complete modules the laser scanning station with 1060 nm diode laser has been assembled at Utrecht University. The testing method relies of the fact that a response of the detector module to a short collimated laser beam pulse resembles a response to a minimum ionizing particle. A small beam spot size (˜7 μm ) allows to deposit the charge in a narrow region and measure the response of individual detector channels. First several module prototypes have been studied with this setup, the strip gain and charge sharing function have been measured, the later is compared with the model predictions. It was also shown that for a laser beam of a high monochromaticity, interference in the sensor bulk significantly modulates the deposited charge and introduces a systematic error of the gain measurement. Signatures of disconnected strips and pinholes defects have been observed, the response of the disconnected strips to the laser beam has been correlated with the noise measurements. Beam test of four prototype modules have been carried out at PS accelerator at CERN using 7 GeV/c pions. It was demonstrated that the modules provide an excellent signal-to-noise ratio in the range 40-75. The estimated spatial resolution for the normally incident tracks is about 18 μm using the center-of-gravity cluster reconstruction method. A non-iterative method for spatial resolution determination was developed, it was shown that in order to determine the resolution of each individual detector in the telescope, the telescope should consist of at least 5 detectors. The detectors showed high detection efficiency, in the order 99%. It was shown that the particle loss occurs mostly in the defected regions near the noisy strips or strips with a very low gain. The efficiency of the sensor area with nominal characteristics is consistent with 100%.

Can neutrino mass be deduced from beta particle spectrum?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Semkow, T.M.

1993-12-31

With 17-keV neutrino faith being uncertain, it is important to examine the effects of detector resolution and response on the detection limits of massive neutrino. The authors use Fermi theory and generate by Monte Carlo up to 5-10{sup 9} {beta}{sup {minus}} decay events from {sup 35}S. The {beta}{sup {minus}} spectra are then resolved by {chi}{sup 2} minimization. We show that given high statistics and accurate knowledge of the response function it should be possible to detect neutrino mass with a proportional detector, particularly with the gas-scintillation proportional detector, in addition to semiconductor, in addition to semiconductor detectors. This paper presentsmore » a design of double-chamber Xe gas-scintillation proportional detector in which the backscattering effects are suppressed. However, even the slight uncertainties in the response functions as well as {approximately} 10{sup {minus}3} relative energy nonlinearities in the {beta}{sup {minus}} spectrum may create an artificial effect of neutrino mass.« less

Carrier transport and collection in fully depleted semiconductors by a combined action of the space charge field and the field due to electrode voltages

DOEpatents

Rehak, P.; Gatti, E.

1984-02-24

A semiconductor charge transport device and method for making same, characterized by providing a thin semiconductor wafer having rectifying functions on its opposing major surfaces and including a small capacitance ohmic contact, in combination with bias voltage means and associated circuit means for applying a predetermined voltage to effectively deplete the wafer in regions thereof between the rectifying junctions and the ohmic contact. A charge transport device of the invention is usable as a drift chamber, a low capacitance detector, or a charge coupled device each constructed according to the methods of the invention for making such devices. Detectors constructed according to the principles of the invention are characterized by having significantly higher particle position indicating resolution than is attainable with prior art detectors, while at the same time requiring substantially fewer readout channels to realize such high resolution.

A new PET detector concept for compact preclinical high-resolution hybrid MR-PET

NASA Astrophysics Data System (ADS)

Berneking, Arne; Gola, Alberto; Ferri, Alessandro; Finster, Felix; Rucatti, Daniele; Paternoster, Giovanni; Jon Shah, N.; Piemonte, Claudio; Lerche, Christoph

2018-04-01

This work presents a new PET detector concept for compact preclinical hybrid MR-PET. The detector concept is based on Linearly-Graded SiPM produced with current FBK RGB-HD technology. One 7.75 mm x 7.75 mm large sensor chip is coupled with optical grease to a black coated 8 mm x 8 mm large and 3 mm thick monolithic LYSO crystal. The readout is obtained from four readout channels with the linear encoding based on integrated resistors and the Center of Gravity approach. To characterize the new detector concept, the spatial and energy resolutions were measured. Therefore, the measurement setup was prepared to radiate a collimated beam to 25 different points perpendicular to the monolithic scintillator crystal. Starting in the center point of the crystal at 0 mm / 0 mm and sampling a grid with a pitch of 1.75 mm, all significant points of the detector were covered by the collimator beam. The measured intrinsic spatial resolution (FWHM) was 0.74 +/- 0.01 mm in x- and 0.69 +/- 0.01 mm in the y-direction at the center of the detector. At the same point, the measured energy resolution (FWHM) was 13.01 +/- 0.05 %. The mean intrinsic spatial resolution (FWHM) over the whole detector was 0.80 +/- 0.28 mm in x- and 0.72 +/- 0.19 mm in y-direction. The energy resolution (FWHM) of the detector was between 13 and 17.3 % with an average energy resolution of 15.7 +/- 1.0 %. Due to the reduced thickness, the sensitivity of this gamma detector is low but still higher than pixelated designs with the same thickness due to the monolithic crystals. Combining compact design, high spatial resolution, and high sensitivity, the detector concept is particularly suitable for applications where the scanner bore size is limited and high resolution is required - as is the case in small animal hybrid MR-PET.

TU-E-217BCD-06: Cone Beam Breast CT with a High Resolution Flat Panel Detector-Improvement of Calcification Visibility.

PubMed

Shen, Y; Zhong, Y; Lai, C; Wang, T; Shaw, C

2012-06-01

To investigate the advantage of a high resolution flat panel detector for improving the visibility of microcalcifications (MCs) in cone beam breast CT Methods: A paraffin cylinder was used to simulate a 100% adipose breast. Calcium carbonate grains, ranging from 125-140 μm to 224 - 250 μm in size, were used to simulate the MCs. Groups of 25 same size MCs were embedded at the phantom center. The phantom was scanned with a bench-top CBCT system at various exposure levels. A 75μm pitch flat panel detector (Dexela 2923, Perkin Elmer) with 500μm thick CsI scintillator plate was used as the high resolution detector. A 194 μm pitch detector (Paxscan 4030CB, Varian Medical Systems) was used for reference. 300 projection images were acquired over 360° and reconstructed. The images were reviewed by 6 readers. The MC visibility was quantified as the fraction of visible MCs and averaged for comparison. The visibility was plotted as a function of the estimated dose level for various MC sizes and detectors. The MTFs and DQEs were measured and compared. For imaging small (200 μm and smaller) MCs, the visibility achieved with the 75μm pitch detector was found to be significantly higher than those achieved with the 194μm pitch detector. For imaging larger MCs, there was little advantage in using the 75μm pitch detector. Using the 75μm pitch detector, MCs as small as 180 μm could be imaged to achieve a visibility of 78% with an isocenter tissue dose of ∼20 mGys versus 62% achieved with the 194 μm pitch detector at the same dose level. It was found that a high pitch flat panel detector had the advantages of extending its imaging capability to higher frequencies thus helping improve the visibility when used to image small MCs. This work was supported in part by grants CA104759, CA13852 and CA124585 from NIH-NCI, a grant EB00117 from NIH-NIBIB, and a subcontract from NIST-ATP. © 2012 American Association of Physicists in Medicine.

High resolution collimator system for X-ray detector

DOEpatents

Eberhard, Jeffrey W.; Cain, Dallas E.

1987-01-01

High resolution in an X-ray computerized tomography (CT) inspection system is achieved by using a collimator/detector combination to limit the beam width of the X-ray beam incident on a detector element to the desired resolution width. In a detector such as a high pressure Xenon detector array, a narrow tapered collimator is provided above a wide detector element. The collimator slits have any desired width, as small as a few mils at the top, the slit width is easily controlled, and they are fabricated on standard machines. The slit length determines the slice thickness of the CT image.

A compact high resolution flat panel PET detector based on the new 4-side buttable MPPC for biomedical applications

PubMed Central

Wang, Qiang; Wen, Jie; Ravindranath, Bosky; O’Sullivan, Andrew W.; Catherall, David; Li, Ke; Wei, Shouyi; Komarov, Sergey; Tai, Yuan-Chuan

2015-01-01

Compact high-resolution panel detectors using virtual pinhole (VP) PET geometry can be inserted into existing clinical or pre-clinical PET systems to improve regional spatial resolution and sensitivity. Here we describe a compact panel PET detector built using the new Though Silicon Via (TSV) multi-pixel photon counters (MPPC) detector. This insert provides high spatial resolution and good timing performance for multiple bio-medical applications. Because the TSV MPPC design eliminates wire bonding and has a package dimension which is very close to the MPPC’s active area, it is 4-side buttable. The custom designed MPPC array (based on Hamamatsu S12641-PA-50(x)) used in the prototype is composed of 4 × 4 TSV-MPPC cells with a 4.46 mm pitch in both directions. The detector module has 16 × 16 lutetium yttrium oxyorthosilicate (LYSO) crystal array, with each crystal measuring 0.92 × 0.92 × 3 mm3 with 1.0 mm pitch. The outer diameter of the detector block is 16.8 × 16.8 mm2. Thirty-two such blocks will be arranged in a 4 × 8 array with 1 mm gaps to form a panel detector with detection area around 7 cm × 14 cm in the full-size detector. The flood histogram acquired with Ge-68 source showed excellent crystal separation capability with all 256 crystals clearly resolved. The detector module’s mean, standard deviation, minimum (best) and maximum (worst) energy resolution were 10.19%, +/−0.68%, 8.36% and 13.45% FWHM, respectively. The measured coincidence time resolution between the block detector and a fast reference detector (around 200 ps single photon timing resolution) was 0.95 ns. When tested with Siemens Cardinal electronics the performance of the detector blocks remain consistent. These results demonstrate that the TSV-MPPC is a promising photon sensor for use in a flat panel PET insert composed of many high resolution compact detector modules. PMID:26085702

The spatial resolution of a rotating gamma camera tomographic facility.

PubMed

Webb, S; Flower, M A; Ott, R J; Leach, M O; Inamdar, R

1983-12-01

An important feature determining the spatial resolution in transverse sections reconstructed by convolution and back-projection is the frequency filter corresponding to the convolution kernel. Equations have been derived giving the theoretical spatial resolution, for a perfect detector and noise-free data, using four filter functions. Experiments have shown that physical constraints will always limit the resolution that can be achieved with a given system. The experiments indicate that the region of the frequency spectrum between KN/2 and KN where KN is the Nyquist frequency does not contribute significantly to resolution. In order to investigate the physical effect of these filter functions, the spatial resolution of reconstructed images obtained with a GE 400T rotating gamma camera has been measured. The results obtained serve as an aid to choosing appropriate reconstruction filters for use with a rotating gamma camera system.

Simulation study of light transport in laser-processed LYSO:Ce detectors with single-side readout

NASA Astrophysics Data System (ADS)

Bläckberg, L.; El Fakhri, G.; Sabet, H.

2017-11-01

A tightly focused pulsed laser beam can locally modify the crystal structure inside the bulk of a scintillator. The result is incorporation of so-called optical barriers with a refractive index different from that of the crystal bulk, that can be used to redirect the scintillation light and control the light spread in the detector. We here systematically study the scintillation light transport in detectors fabricated using the laser induced optical barrier technique, and objectively compare their potential performance characteristics with those of the two mainstream detector types: monolithic and mechanically pixelated arrays. Among countless optical barrier patterns, we explore barriers arranged in a pixel-like pattern extending all-the-way or half-way through a 20 mm thick LYSO:Ce crystal. We analyze the performance of the detectors coupled to MPPC arrays, in terms of light response functions, flood maps, line profiles, and light collection efficiency. Our results show that laser-processed detectors with both barrier patterns constitute a new detector category with a behavior between that of the two standard detector types. Results show that when the barrier-crystal interface is smooth, no DOI information can be obtained regardless of barrier refractive index (RI). However, with a rough barrier-crystal interface we can extract multiple levels of DOI. Lower barrier RI results in larger light confinement, leading to better transverse resolution. Furthermore we see that the laser-processed crystals have the potential to increase the light collection efficiency, which could lead to improved energy resolution and potentially better timing resolution due to higher signals. For a laser-processed detector with smooth barrier-crystal interfaces the light collection efficiency is simulated to  >42%, and for rough interfaces  >73%. The corresponding numbers for a monolithic crystal is 39% with polished surfaces, and 71% with rough surfaces, and for a mechanically pixelated array 35% with polished pixel surfaces and 59% with rough surfaces.

Simulation study of light transport in laser-processed LYSO:Ce detectors with single-side readout.

PubMed

Bläckberg, L; El Fakhri, G; Sabet, H

2017-10-19

A tightly focused pulsed laser beam can locally modify the crystal structure inside the bulk of a scintillator. The result is incorporation of so-called optical barriers with a refractive index different from that of the crystal bulk, that can be used to redirect the scintillation light and control the light spread in the detector. We here systematically study the scintillation light transport in detectors fabricated using the laser induced optical barrier technique, and objectively compare their potential performance characteristics with those of the two mainstream detector types: monolithic and mechanically pixelated arrays. Among countless optical barrier patterns, we explore barriers arranged in a pixel-like pattern extending all-the-way or half-way through a 20 mm thick LYSO:Ce crystal. We analyze the performance of the detectors coupled to MPPC arrays, in terms of light response functions, flood maps, line profiles, and light collection efficiency. Our results show that laser-processed detectors with both barrier patterns constitute a new detector category with a behavior between that of the two standard detector types. Results show that when the barrier-crystal interface is smooth, no DOI information can be obtained regardless of barrier refractive index (RI). However, with a rough barrier-crystal interface we can extract multiple levels of DOI. Lower barrier RI results in larger light confinement, leading to better transverse resolution. Furthermore we see that the laser-processed crystals have the potential to increase the light collection efficiency, which could lead to improved energy resolution and potentially better timing resolution due to higher signals. For a laser-processed detector with smooth barrier-crystal interfaces the light collection efficiency is simulated to  >42%, and for rough interfaces  >73%. The corresponding numbers for a monolithic crystal is 39% with polished surfaces, and 71% with rough surfaces, and for a mechanically pixelated array 35% with polished pixel surfaces and 59% with rough surfaces.

Characteristic Performance Evaluation of a new SAGe Well Detector for Small and Large Sample Geometries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adekola, A.S.; Colaresi, J.; Douwen, J.

2015-07-01

Environmental scientific research requires a detector that has sensitivity low enough to reveal the presence of any contaminant in the sample at a reasonable counting time. Canberra developed the germanium detector geometry called Small Anode Germanium (SAGe) Well detector, which is now available commercially. The SAGe Well detector is a new type of low capacitance germanium well detector manufactured using small anode technology capable of advancing many environmental scientific research applications. The performance of this detector has been evaluated for a range of sample sizes and geometries counted inside the well, and on the end cap of the detector. Themore » detector has energy resolution performance similar to semi-planar detectors, and offers significant improvement over the existing coaxial and Well detectors. Energy resolution performance of 750 eV Full Width at Half Maximum (FWHM) at 122 keV γ-ray energy and resolution of 2.0 - 2.3 keV FWHM at 1332 keV γ-ray energy are guaranteed for detector volumes up to 425 cm{sup 3}. The SAGe Well detector offers an optional 28 mm well diameter with the same energy resolution as the standard 16 mm well. Such outstanding resolution performance will benefit environmental applications in revealing the detailed radionuclide content of samples, particularly at low energy, and will enhance the detection sensitivity resulting in reduced counting time. The detector is compatible with electric coolers without any sacrifice in performance and supports the Canberra Mathematical efficiency calibration method (In situ Object Calibration Software or ISOCS, and Laboratory Source-less Calibration Software or LABSOCS). In addition, the SAGe Well detector supports true coincidence summing available in the ISOCS/LABSOCS framework. The improved resolution performance greatly enhances detection sensitivity of this new detector for a range of sample sizes and geometries counted inside the well. This results in lower minimum detectable concentrations compared to Traditional Well detectors. The SAGe Well detectors are compatible with Marinelli beakers and compete very well with semi-planar and coaxial detectors for large samples in many applications. (authors)« less

Characterizations of BC501A and BC537 liquid scintillator detectors.

PubMed

Qin, Jianguo; Lai, Caifeng; Ye, Bangjiao; Liu, Rong; Zhang, Xinwei; Jiang, Li

2015-10-01

Two 2″×2″ liquid scintillator detectors BC537 and BC501A have been characterized for their responses and efficiencies to γ-ray detection. Light output resolution and response functions were derived by least-squares minimization of a simulated response function, fitted to experimental data. The γ-ray response matrix and detection efficiency were simulated with Monte Carlo (MC) methods and validated. For photon energies below 2.4 MeVee, the resolution, as well as the efficiency, of BC501A is better than BC537 scintillator. The situation is reversed when the energy is higher than 2.4 MeVee. BC537 has higher γ-ray detection efficiency than BC501A if the impinging photon energy is more than 2 MeV due to different ratios of C to H/D atoms. Copyright © 2015 Elsevier Ltd. All rights reserved.

Single crystal diamond detector measurements of deuterium-deuterium and deuterium-tritium neutrons in Joint European Torus fusion plasmas.

PubMed

Cazzaniga, C; Sundén, E Andersson; Binda, F; Croci, G; Ericsson, G; Giacomelli, L; Gorini, G; Griesmayer, E; Grosso, G; Kaveney, G; Nocente, M; Perelli Cippo, E; Rebai, M; Syme, B; Tardocchi, M

2014-04-01

First simultaneous measurements of deuterium-deuterium (DD) and deuterium-tritium neutrons from deuterium plasmas using a Single crystal Diamond Detector are presented in this paper. The measurements were performed at JET with a dedicated electronic chain that combined high count rate capabilities and high energy resolution. The deposited energy spectrum from DD neutrons was successfully reproduced by means of Monte Carlo calculations of the detector response function and simulations of neutron emission from the plasma, including background contributions. The reported results are of relevance for the development of compact neutron detectors with spectroscopy capabilities for installation in camera systems of present and future high power fusion experiments.

A Multi-Contact, Low Capacitance HPGe Detector for High Rate Gamma Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cox, Christopher

2014-12-04

The detection, identification and non-destructive assay of special nuclear materials and nuclear fission by-products are critically important activities in support of nuclear non-proliferation programs. Both national and international nuclear safeguard agencies recognize that current accounting methods for spent nuclear fuel are inadequate from a safeguards perspective. Radiation detection and analysis by gamma-ray spectroscopy is a key tool in this field, but no instrument exists that can deliver the required performance (energy resolution and detection sensitivity) in the presence of very high background count rates encountered in the nuclear safeguards arena. The work of this project addresses this critical need bymore » developing a unique gamma-ray detector based on high purity germanium that has the previously unachievable property of operating in the 1 million counts-per-second range while achieving state-of-the-art energy resolution necessary to identify and analyze the isotopes of interest. The technical approach was to design and fabricate a germanium detector with multiple segmented electrodes coupled to multi-channel high rate spectroscopy electronics. Dividing the germanium detector’s signal electrode into smaller sections offers two advantages; firstly, the energy resolution of the detector is potentially improved, and secondly, the detector is able to operate at higher count rates. The design challenges included the following; determining the optimum electrode configuration to meet the stringent energy resolution and count rate requirements; determining the electronic noise (and therefore energy resolution) of the completed system after multiple signals are recombined; designing the germanium crystal housing and vacuum cryostat; and customizing electronics to perform the signal recombination function in real time. In this phase I work, commercial off-the-shelf electrostatic modeling software was used to develop the segmented germanium crystal geometry, which underwent several iterations before an optimal electrode configuration was found. The model was tested and validated against real-world measurements with existing germanium detectors. Extensive modeling of electronic noise was conducted using established formulae, and real-world measurements were performed on candidate front-end electronic components. This initial work proved the feasibility of the design with respect to expected high count rate and energy resolution performance. Phase I also delivered the mechanical design of the detector housing and vacuum cryostat to be built in Phase II. Finally, a Monte Carlo simulation was created to show the response of the complete design to a Cs-137 source. This development presents a significant advance for nuclear safeguards instrumentation with increased speed and accuracy of detection and identification of special nuclear materials. Other significant applications are foreseen for a gamma-ray detector that delivers high energy resolution (1keV FWHM noise) at high count rate (1 Mcps), especially in the areas of physics research and materials analysis.« less

Design consideration of a multipinhole collimator with septa for ultra high-resolution silicon drift detector modules

NASA Astrophysics Data System (ADS)

Min, Byung Jun; Choi, Yong; Lee, Nam-Yong; Lee, Kisung; Ahn, Young Bok; Joung, Jinhun

2009-07-01

The aim of this study was to design a multipinhole (MP) collimator with lead vertical septa coupled to a high-resolution detector module containing silicon drift detectors (SDDs) with an intrinsic resolution approaching the sub-millimeter level. Monte Carlo simulations were performed to determine pinhole parameters such as pinhole diameter, focal length, and number of pinholes. Effects of parallax error and collimator penetration were investigated for the new MP collimator design. The MP detector module was evaluated using reconstructed images of resolution and mathematical cardiac torso (MCAT) phantoms. In addition, the reduced angular sampling effect was investigated over 180°. The images were reconstructed using dedicated maximum likelihood expectation maximization (MLEM) algorithm. An MP collimator with 81-pinhole was designed with a 2-mm-diameter pinhole and a focal length of 40 mm . Planar sensitivity and resolution obtained using the devised MP collimator were 3.9 cps/μCi and 6 mm full-width at half-maximum (FWHM) at a 10 cm distance. The parallax error and penetration ratio were significantly improved using the proposed MP collimation design. The simulation results demonstrated that the proposed MP detector provided enlarged imaging field of view (FOV) and improved the angular sampling effect in resolution and MCAT phantom studies. Moreover, the novel design enables tomography images by simultaneously obtaining eight projections with eight-detector modules located along the 180° orbit surrounding a patient, which allows designing of a stationary cardiac SPECT. In conclusion, the MP collimator with lead vertical septa was designed to have comparable system resolution and sensitivity to those of the low-energy high-resolution (LEHR) collimator per detector. The system sensitivity with an eight-detector configuration would be four times higher than that with a standard dual-detector cardiac SPECT.

Design and initial performance of PlanTIS: a high-resolution positron emission tomograph for plants

NASA Astrophysics Data System (ADS)

Beer, S.; Streun, M.; Hombach, T.; Buehler, J.; Jahnke, S.; Khodaverdi, M.; Larue, H.; Minwuyelet, S.; Parl, C.; Roeb, G.; Schurr, U.; Ziemons, K.

2010-02-01

Positron emitters such as 11C, 13N and 18F and their labelled compounds are widely used in clinical diagnosis and animal studies, but can also be used to study metabolic and physiological functions in plants dynamically and in vivo. A very particular tracer molecule is 11CO2 since it can be applied to a leaf as a gas. We have developed a Plant Tomographic Imaging System (PlanTIS), a high-resolution PET scanner for plant studies. Detectors, front-end electronics and data acquisition architecture of the scanner are based on the ClearPET™ system. The detectors consist of LSO and LuYAP crystals in phoswich configuration which are coupled to position-sensitive photomultiplier tubes. Signals are continuously sampled by free running ADCs, and data are stored in a list mode format. The detectors are arranged in a horizontal plane to allow the plants to be measured in the natural upright position. Two groups of four detector modules stand face-to-face and rotate around the field-of-view. This special system geometry requires dedicated image reconstruction and normalization procedures. We present the initial performance of the detector system and first phantom and plant measurements.

Design and initial performance of PlanTIS: a high-resolution positron emission tomograph for plants.

PubMed

Beer, S; Streun, M; Hombach, T; Buehler, J; Jahnke, S; Khodaverdi, M; Larue, H; Minwuyelet, S; Parl, C; Roeb, G; Schurr, U; Ziemons, K

2010-02-07

Positron emitters such as (11)C, (13)N and (18)F and their labelled compounds are widely used in clinical diagnosis and animal studies, but can also be used to study metabolic and physiological functions in plants dynamically and in vivo. A very particular tracer molecule is (11)CO(2) since it can be applied to a leaf as a gas. We have developed a Plant Tomographic Imaging System (PlanTIS), a high-resolution PET scanner for plant studies. Detectors, front-end electronics and data acquisition architecture of the scanner are based on the ClearPET system. The detectors consist of LSO and LuYAP crystals in phoswich configuration which are coupled to position-sensitive photomultiplier tubes. Signals are continuously sampled by free running ADCs, and data are stored in a list mode format. The detectors are arranged in a horizontal plane to allow the plants to be measured in the natural upright position. Two groups of four detector modules stand face-to-face and rotate around the field-of-view. This special system geometry requires dedicated image reconstruction and normalization procedures. We present the initial performance of the detector system and first phantom and plant measurements.

Th/U/Pu/Cm dating of galactic cosmic rays with the extremely heavy cosmic ray composition observer

NASA Astrophysics Data System (ADS)

Westphal, Andrew J.; Weaver, Benjamin A.; Tarlé, Gregory

The principal goal of ECCO, the Extremely-heavy Cosmic-ray Composition Observer, is the measurement of the age of heavy galactic cosmic-ray nuclei using the extremely rare actinides (Th, U, Pu, Cm) as clocks. ECCO is one of two cosmic-ray instruments comprising the Heavy Nuclei Explorer (HNX), which was recently selected as one of several missions for Phase A study under NASA's Small class Explorer (SMEX) program. ECCO is based on the flight heritage of Trek, an array of barium-phosphate glass tracketch detectors deployed on the Russian space station Mir from 1991-1995. Using Trek, we measured the abundances of elements with Z > 70 in the galactic cosmic rays (GCRs). Trek consisted of a 1 m 2 array of stacks of individually polished thin BP-1 glass detectors. ECCO will be a much larger instrument, but will achieve both excellent resolution and low cost through use of a novel detector configuration. Here we report the results of recent accelerator tests of the ECCO detectors that verify detector performance. We also show the expected charge and energy resolution of ECCO as a function of energy.

On charged particle tracks in cellulose nitrate and Lexan

NASA Technical Reports Server (NTRS)

Benton, E. V.; Henke, R. P.

1972-01-01

Investigations were performed aimed at developing plastic nuclear track detectors into quantitative tools for recording and measuring multicharged, heavy particles. Accurate track etch rate measurements as a function of LET were performed for cellulose nitrate and Lexan plastic detectors. This was done using a variety of incident charged particle types and energies. The effect of aging of latent tracks in Lexan in different gaseous atmospheres was investigated. Range distributions of high energy N-14 particle bevatron beams in nuclear emulsion were measured. Investigation of charge resolution and Bragg peak measurements were carried out using plastic nuclear track detectors.

High resolution multidetector CT aided tissue analysis and quantification of lung fibrosis

NASA Astrophysics Data System (ADS)

Zavaletta, Vanessa A.; Karwoski, Ronald A.; Bartholmai, Brian; Robb, Richard A.

2006-03-01

Idiopathic pulmonary fibrosis (IPF, also known as Idiopathic Usual Interstitial Pneumontis, pathologically) is a progressive diffuse lung disease which has a median survival rate of less than four years with a prevalence of 15-20/100,000 in the United States. Global function changes are measured by pulmonary function tests and the diagnosis and extent of pulmonary structural changes are typically assessed by acquiring two-dimensional high resolution CT (HRCT) images. The acquisition and analysis of volumetric high resolution Multi-Detector CT (MDCT) images with nearly isotropic pixels offers the potential to measure both lung function and structure. This paper presents a new approach to three dimensional lung image analysis and classification of normal and abnormal structures in lungs with IPF.

Cascaded systems analysis of charge sharing in cadmium telluride photon-counting x-ray detectors.

PubMed

Tanguay, Jesse; Cunningham, Ian A

2018-05-01

Single-photon-counting (SPC) and spectroscopic x-ray detectors are under development in academic and industry laboratories for medical imaging applications. The spatial resolution of SPC and spectroscopic x-ray detectors is an important design criterion. The purpose of this article was to extend the cascaded systems approach to include a description of the spatial resolution of SPC and spectroscopic x-ray imaging detectors. A cascaded systems approach was used to model reabsorption of characteristic x rays, Coulomb repulsion, and diffusion in SPC and spectroscopic x-ray detectors. In addition to reabsorption, diffusion, and Coulomb repulsion, the model accounted for x-ray conversion to electron-hole (e-h) pairs, integration of e-h pairs in detector elements, electronic noise, and energy thresholding. The probability density function (PDF) describing the number of e-h pairs was propagated through each stage of the model and was used to derive new theoretical expressions for the large-area gain and modulation transfer function (MTF) of CdTe SPC x-ray detectors, and the energy bin sensitivity functions and MTFs of CdTe spectroscopic detectors. Theoretical predictions were compared with the results of MATLAB-based Monte Carlo (MC) simulations and published data. Comparisons were also made with the MTF of energy-integrating systems. Under general radiographic conditions, reabsorption, diffusion, and Coulomb repulsion together artificially inflate count rates by 20% to 50%. For thicker converters (e.g. 1000 μm) and larger detector elements (e.g. 500 μm pixel pitch) these processes result in modest inflation (i.e. ∼10%) in apparent count rates. Our theoretical and MC analyses predict that SPC MTFs will be degraded relative to those of energy-integrating systems for fluoroscopic, general radiographic, and CT imaging conditions. In most cases, this degradation is modest (i.e., ∼10% at the Nyquist frequency). However, for thicker converters, the SPC MTF can be degraded by up to 25% at the Nyquist frequency relative to EI systems. Additionally, unlike EI systems, the MTF of spectroscopic systems is strongly dependent on photon energy, which results in energy-bin-dependent spatial resolution in spectroscopic systems. The PDF-transfer approach to modeling signal transfer through SPC and spectroscopic x-ray imaging systems provides a framework for understanding system performance. Application of this approach demonstrated that charge sharing artificially inflates the SPC image signal and degrades the MTF of SPC and spectroscopic systems relative to energy-integrating systems. These results further motivate the need for anticharge-sharing circuits to mitigate the effects of charge sharing on SPC and spectroscopic x-ray image quality. © 2018 American Association of Physicists in Medicine.

Geo-PET: A novel generic organ-pet for small animal organs and tissues

NASA Astrophysics Data System (ADS)

Sensoy, Levent

Reconstructed tomographic image resolution of small animal PET imaging systems is improving with advances in radiation detector development. However the trend towards higher resolution systems has come with an increase in price and system complexity. Recent developments in the area of solid-state photomultiplication devices like silicon photomultiplier arrays (SPMA) are creating opportunities for new high performance tools for PET scanner design. Imaging of excised small animal organs and tissues has been used as part of post-mortem studies in order to gain detailed, high-resolution anatomical information on sacrificed animals. However, this kind of ex-vivo specimen imaging has largely been limited to ultra-high resolution muCT. The inherent limitations to PET resolution have, to date, excluded PET imaging from these ex-vivo imaging studies. In this work, we leverage the diminishing physical size of current generation SPMA designs to create a very small, simple, and high-resolution prototype detector system targeting ex-vivo tomographic imaging of small animal organs and tissues. We investigate sensitivity, spatial resolution, and the reconstructed image quality of a prototype small animal PET scanner designed specifically for imaging of excised murine tissue and organs. We aim to demonstrate that a cost-effective silicon photomultiplier (SiPM) array based design with thin crystals (2 mm) to minimize depth of interaction errors might be able to achieve sub-millimeter resolution. We hypothesize that the substantial decrease in sensitivity associated with the thin crystals can be compensated for with increased solid angle detection, longer acquisitions, higher activity and wider acceptance energy windows (due to minimal scatter from excised organs). The constructed system has a functional field of view (FoV) of 40 mm diameter, which is adequate for most small animal specimen studies. We perform both analytical (3D-FBP) and iterative (ML-EM) methods in order to reconstruct tomographic images. Results demonstrate good agreement between the simulation and the prototype. Our detector system with pixelated crystals is able to separate small objects as close as 1.25 mm apart, whereas spatial resolution converges to the theoretical limit of 1.6 mm (half the size of the smallest detecting element), which is to comparable to the spatial resolution of the existing commercial small animal PET systems. Better system spatial resolution is achievable with new generation SiPM detector boards with 1 mm x 1 mm cell dimensions. We demonstrate through Monte Carlo simulations that it is possible to achieve sub-millimeter spatial image resolution (0.7 mm for our scanner) in complex objects using monolithic crystals and exploiting the light-sharing mechanism among the neighboring detector cells. Results also suggest that scanner (or object) rotation minimizes artifacts arising from poor angular sampling, which is even more significant in smaller PET designs as the gaps between the sensitive regions of the detector have a more exaggerated effect on the overall reconstructed image quality when the design is more compact. Sensitivity of the system, on the other hand, can be doubled by adding two additional detector heads resulting in a, fully closed, 4? geometry.

Estimation of Orbital Neutron Detector Spatial Resolution by Systematic Shifting of Differential Topographic Masks

NASA Technical Reports Server (NTRS)

McClanahan, T. P.; Mitrofanov, I. G.; Boynton, W. V.; Chin, G.; Livengood, T.; Starr, R. D.; Evans, L. G.; Mazarico, E.; Smith, D. E.

2012-01-01

We present a method and preliminary results related to determining the spatial resolution of orbital neutron detectors using epithermal maps and differential topographic masks. Our technique is similar to coded aperture imaging methods for optimizing photonic signals in telescopes [I]. In that approach photon masks with known spatial patterns in a telescope aperature are used to systematically restrict incoming photons which minimizes interference and enhances photon signal to noise. Three orbital neutron detector systems with different stated spatial resolutions are evaluated. The differing spatial resolutions arise due different orbital altitudes and the use of neutron collimation techniques. 1) The uncollimated Lunar Prospector Neutron Spectrometer (LPNS) system has spatial resolution of 45km FWHM from approx. 30km altitude mission phase [2]. The Lunar Rennaissance Orbiter (LRO) Lunar Exploration Neutron Detector (LEND) with two detectors at 50km altitude evaluated here: 2) the collimated 10km FWHM spatial resolution detector CSETN and 3) LEND's collimated Sensor for Epithermal Neutrons (SETN). Thus providing two orbital altitudes to study factors of: uncollimated vs collimated and two average altitudes for their effect on fields-of-view.

Chandra's Ultimate Angular Resolution: Studies of the HRC-I Point Spread Function

NASA Astrophysics Data System (ADS)

Juda, Michael; Karovska, M.

2010-03-01

The Chandra High Resolution Camera (HRC) should provide an ideal imaging match to the High-Resolution Mirror Assembly (HRMA). The laboratory-measured intrinsic resolution of the HRC is 20 microns FWHM. HRC event positions are determined via a centroiding method rather than by using discrete pixels. This event position reconstruction method and any non-ideal performance of the detector electronics can introduce distortions in event locations that, when combined with spacecraft dither, produce artifacts in source images. We compare ray-traces of the HRMA response to "on-axis" observations of AR Lac and Capella as they move through their dither patterns to images produced from filtered event lists to characterize the effective intrinsic PSF of the HRC-I. A two-dimensional Gaussian, which is often used to represent the detector response, is NOT a good representation of the intrinsic PSF of the HRC-I; the actual PSF has a sharper peak and additional structure which will be discussed. This work was supported under NASA contract NAS8-03060.

Evaluation of Large Volume SrI2(Eu) Scintillator Detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sturm, B W; Cherepy, N J; Drury, O B

2010-11-18

There is an ever increasing demand for gamma-ray detectors which can achieve good energy resolution, high detection efficiency, and room-temperature operation. We are working to address each of these requirements through the development of large volume SrI{sub 2}(Eu) scintillator detectors. In this work, we have evaluated a variety of SrI{sub 2} crystals with volumes >10 cm{sup 3}. The goal of this research was to examine the causes of energy resolution degradation for larger detectors and to determine what can be done to mitigate these effects. Testing both packaged and unpackaged detectors, we have consistently achieved better resolution with the packagedmore » detectors. Using a collimated gamma-ray source, it was determined that better energy resolution for the packaged detectors is correlated with better light collection uniformity. A number of packaged detectors were fabricated and tested and the best spectroscopic performance was achieved for a 3% Eu doped crystal with an energy resolution of 2.93% FWHM at 662keV. Simulations of SrI{sub 2}(Eu) crystals were also performed to better understand the light transport physics in scintillators and are reported. This study has important implications for the development of SrI{sub 2}(Eu) detectors for national security purposes.« less

High-resolution 3D laser imaging based on tunable fiber array link

NASA Astrophysics Data System (ADS)

Zhao, Sisi; Ruan, Ningjuan; Yang, Song

2017-10-01

Airborne photoelectric reconnaissance system with the bore sight down to the ground is an important battlefield situational awareness system, which can be used for reconnaissance and surveillance of complex ground scene. Airborne 3D imaging Lidar system is recognized as the most potential candidates for target detection under the complex background, and is progressing in the directions of high resolution, long distance detection, high sensitivity, low power consumption, high reliability, eye safe and multi-functional. However, the traditional 3D laser imaging system has the disadvantages of lower imaging resolutions because of the small size of the existing detector, and large volume. This paper proposes a high resolution laser 3D imaging technology based on the tunable optical fiber array link. The echo signal is modulated by a tunable optical fiber array link and then transmitted to the focal plane detector. The detector converts the optical signal into electrical signals which is given to the computer. Then, the computer accomplishes the signal calculation and image restoration based on modulation information, and then reconstructs the target image. This paper establishes the mathematical model of tunable optical fiber array signal receiving link, and proposes the simulation and analysis of the affect factors on high density multidimensional point cloud reconstruction.

Challenges, constraints, and results of lens design for 17 micron-bolometer focal plane arrays in 8-12 micron waveband

NASA Astrophysics Data System (ADS)

Schuster, Norbert; Franks, John

2011-06-01

In the 8-12 micron waveband Focal Plane Arrays (FPA) are available with a 17 micron pixel pitch in different arrays sizes (e.g. 512 x 480 pixels and 320 x 240 pixels) and with excellent electrical properties. Many applications become possible using this new type of IR-detector which will become the future standard in uncooled technology. Lenses with an f-number faster than f/1.5 minimize the diffraction impact on the spatial resolution and guarantee a high thermal resolution for uncooled cameras. Both effects will be quantified. The distinction between Traditional f-number (TF) and Radiometric f-number (RF) is discussed. Lenses with different focal lengths are required for applications in a variety of markets. They are classified by their Horizontal field of view (HFOV). Respecting the requirements for high volume markets, several two lens solutions will be discussed. A commonly accepted parameter of spatial resolution is the Modulation Transfer Function (MTF)-value at the Nyquist frequency of the detector (here 30cy/mm). This parameter of resolution will be presented versus field of view. Wide Angle and Super Wide Angle lenses are susceptible to low relative illumination in the corner of the detector. Measures to reduce this drop to an acceptable value are presented.

Measurement of basic characteristics and gain uniformity of a triple GEM detector

NASA Astrophysics Data System (ADS)

Patra, Rajendra Nath; Singaraju, Rama N.; Biswas, Saikat; Ahammed, Zubayer; Nayak, Tapan K.; Viyogi, Yogendra P.

2017-08-01

Large area Gas Electron Multiplier (GEM) detectors have been the preferred choice for tracking devices in major nuclear and particle physics experiments. Uniformity over surface of the detector in terms of gain, energy resolution and efficiency is crucial for the optimum performance of these detectors. In the present work, detailed performance study of a 10×10 cm2 triple GEM detector operated using Ar and CO2 gas mixtures in proportions of 70:30 and 90:10, has been made by making a voltage scan of the efficiency with 106Ru-Rh β-source and cosmic rays. The gain and energy resolution of the detector were studied using the X-ray spectrum of 55Fe source. The uniformity of the detector has been investigated by dividing the detector in 7×7 zones and measuring the gain and energy resolution at the centre of each zone. The variations of the gain and energy resolution have been found to be 8.8% and 6.7%, respectively. These studies are essential to characterise GEM detectors before their final use in the experiments.

Solid state VRX CT detector

NASA Astrophysics Data System (ADS)

DiBianca, Frank A.; Melnyk, Roman; Sambari, Aniket; Jordan, Lawrence M.; Laughter, Joseph S.; Zou, Ping

2000-04-01

A technique called Variable-Resolution X-ray (VRX) detection that greatly increases the spatial resolution in computed tomography (CT) and digital radiography (DR) is presented. The technique is based on a principle called 'projective compression' that allows the resolution element of a CT detector to scale with the subject or field size. For very large (40 - 50 cm) field sizes, resolution exceeding 2 cy/mm is possible and for very small fields, microscopy is attainable with resolution exceeding 100 cy/mm. Preliminary results from a 576-channel solid-state detector are presented. The detector has a dual-arm geometry and is comprised of CdWO4 scintillator crystals arranged in 24 modules of 24 channels/module. The scintillators are 0.85 mm wide and placed on 1 mm centers. Measurements of signal level, MTF and SNR, all versus detector angle, are presented.

Investigation of spatial resolution improvement by use of a mouth-insert detector in the helmet PET scanner.

PubMed

Ahmed, Abdella M; Tashima, Hideaki; Yamaya, Taiga

2018-03-01

The dominant factor limiting the intrinsic spatial resolution of a positron emission tomography (PET) system is the size of the crystal elements in the detector. To increase sensitivity and achieve high spatial resolution, it is essential to use advanced depth-of-interaction (DOI) detectors and arrange them close to the subject. The DOI detectors help maintain high spatial resolution by mitigating the parallax error caused by the thickness of the scintillator near the peripheral regions of the field-of-view. As an optimal geometry for a brain PET scanner, with high sensitivity and spatial resolution, we proposed and developed the helmet-chin PET scanner using 54 four-layered DOI detectors consisting of a 16 × 16 × 4 array of GSOZ scintillator crystals with dimensions of 2.8 × 2.8 × 7.5 mm 3 . All the detectors used in the helmet-chin PET scanner had the same spatial resolution. In this study, we conducted a feasibility study of a new add-on detector arrangement for the helmet PET scanner by replacing the chin detector with a segmented crystal cube, having high spatial resolution in all directions, which can be placed inside the mouth. The crystal cube (which we have named the mouth-insert detector) has an array of 20 × 20 × 20 LYSO crystal segments with dimensions of 1 × 1 × 1 mm 3 . Thus, the scanner is formed by the combination of the helmet and mouth-insert detectors, and is referred to as the helmet-mouth-insert PET scanner. The results show that the helmet-mouth-insert PET scanner has comparable sensitivity and improved spatial resolution near the center of the hemisphere, compared to the helmet-chin PET scanner.

Widefield TSCSPC-systems with large-area-detectors: application in simultaneous multi-channel-FLIM

NASA Astrophysics Data System (ADS)

Stepanov, Sergei; Bakhlanov, Sergei; Drobchenko, Evgeny; Eckert, Hann-Jörg; Kemnitz, Klaus

2010-11-01

Novel proximity-type Time- and Space-Correlated Single Photon Counting (TSCSPC) crossed-delay-line (DL)- and multi-anode (MA)-systems of outstanding performance and homogeneity were developed, using large-area detector heads of 25 and 40 mm diameter. Instrument response functions IRF(space) = (60 +/- 5) μm FWHM and IRF(time) = (28 +/- 3) ps FWHM were achieved over the full 12 cm2 area of the detector. Deadtime at throughput of 105 cps is 10% for "high-resolution" system and 5% in the "video"-system at 106 cps, at slightly reduced time- and space resolution. A fluorescence lifetime of (3.5 +/- 1) ps can be recovered from multi-exponential dynamics of a single living cyanobacterium (Acaryochloris marina). The present large-area detectors are particularly useful in simultaneous multichannel applications, such as 2-colour anisotropy or 4-colour lifetime imaging, utilizing dual- or quad-view image splitters. The long-term stability, low- excitation-intensity (< 100 mW/cm2) widefield systems enable minimal-invasive observation, without significant bleaching or photodynamic reactions, thus allowing long-period observation of up to several hours in living cells.

Simulations of a Thin Sampling Calorimeter with GEANT/FLUKA

NASA Technical Reports Server (NTRS)

Lee, Jeongin; Watts, John; Howell, Leonard; Rose, M. Franklin (Technical Monitor)

2000-01-01

The Advanced Cosmic-ray Composition Experiment for the Space Station (ACCESS) will investigate the origin, composition and acceleration mechanism of cosmic rays by measuring the elemental composition of the cosmic rays up to 10(exp 15) eV. These measurements will be made with a thin ionization calorimeter and a transition radiation detector. This paper reports studies of a thin sampling calorimeter concept for the ACCESS thin ionization calorimeter. For the past year, a Monte Carlo simulation study of a Thin Sampling Calorimeter (TSC) design has been conducted to predict the detector performance and to design the system for achieving the ACCESS scientific objectives. Simulation results show that the detector energy resolution function resembles a Gaussian distribution and the energy resolution of TSC is about 40%. In addition, simulations of the detector's response to an assumed broken power law cosmic ray spectra in the region where the 'knee' of the cosmic ray spectrum occurs have been conducted and clearly show that a thin sampling calorimeter can provide sufficiently accurate estimates of the spectral parameters to meet the science requirements of ACCESS. n

Developing fine-pixel CdTe detectors for the next generation of high-resolution hard x-ray telescopes

NASA Astrophysics Data System (ADS)

Christe, Steven

Over the past decade, the NASA Marshall Space Flight Center (MSFC) has been improving the angular resolution of hard X-ray (HXR; 20 "70 keV) optics to the point that we now routinely manufacture optics modules with an angular resolution of 20 arcsec Half Power Diameter (HDP), almost three times the performance of NuSTAR optics (Ramsey et al. 2013; Gubarev et al. 2013a; Atkins et al. 2013). New techniques are currently being developed to provide even higher angular resolution. High angular resolution HXR optics require detectors with a large number of fine pixels in order to adequately sample the telescope point spread function (PSF) over the entire field of view. Excessively over-sampling the PSF will increase readout noise and require more processing with no appreciable increase in image quality. An appropriate level of over-sampling is to have 3 pixels within the HPD. For the HERO mirrors, where the HPD is 26 arcsec over a 6-m focal length converts to 750 μm, the optimum pixel size is around 250 μm. At a 10-m focal length these detectors can support a 16 arcsec HPD. Of course, the detectors must also have high efficiency in the HXR region, good energy resolution, low background, low power requirements, and low sensitivity to radiation damage (Ramsey 2001). The ability to handle high counting rates is also desirable for efficient calibration. A collaboration between Goddard Space Flight Center (GSFC), MSFC, and Rutherford Appleton Laboratory (RAL) in the UK is developing precisely such detectors under an ongoing, funded APRA program (FY2015 to FY2017). The detectors use the RALdeveloped Application Specific Integrated Circuit (ASIC) dubbed HEXITEC, for High Energy X-Ray Imaging Technology. These HEXITEC ASICs can be bonded to 1- or 2- mm-thick Cadmium Telluride (CdTe) or Cadmium-Zinc-Telluride (CZT) to create a fine (250 μm pitch) HXR detector (Jones et al. 2009; Seller et al. 2011). The objectives of this funded effort are to develop and test a HEXITEC-based detector system through the (1) design, manufacture, and test of front-end electronics instrument boards and (2) calibration of the detectors to assess their performance and (3) vibration and environmental testing. By the end of this program, multiple detector assemblies will be built and characterized, and can be used as part of future instruments. We propose to augment the existing effort with the development of an anti-coincidence shield for these HEXITEC-based detector assemblies to maximize sensitivity. Designing the anti-coincidence shield is enabled by the addition of a new team member, Wayne Baumgartner, who has recently and fortuitously joined the existing effort. Dr. Baumgartner has valuable and relevant past experience with a similar shield systems developed for NuSTAR and the InFOCμS x-ray telescope. We are asking for a modest amount of additional funding in this proposal year, as it coincides with a key time in the characterization and environmental testing of the detector assemblies. Characterization and environmental testing of the bare assemblies is already funded under the current effort. The addition of this active shield will allow for a more complete detector module vibration and environment test at the end of the existing development program so that this project results in a detector system with a demonstrated TRL of 6: "System/subsystem model or prototype demonstration in a relevant environment."

Impact of detector design on imaging performance of a long axial field-of-view, whole-body PET scanner

NASA Astrophysics Data System (ADS)

Surti, S.; Karp, J. S.

2015-07-01

Current generation of commercial time-of-flight (TOF) PET scanners utilize 20-25 mm thick LSO or LYSO crystals and have an axial FOV (AFOV) in the range of 16-22 mm. Longer AFOV scanners would provide increased intrinsic sensitivity and require fewer bed positions for whole-body imaging. Recent simulation work has investigated the sensitivity gains that can be achieved with these long AFOV scanners, and has motivated new areas of investigation such as imaging with a very low dose of injected activity as well as providing whole-body dynamic imaging capability in one bed position. In this simulation work we model a 72 cm long scanner and prioritize the detector design choices in terms of timing resolution, crystal size (spatial resolution), crystal thickness (detector sensitivity), and depth-of-interaction (DOI) measurement capability. The generated list data are reconstructed with a list-mode OSEM algorithm using a Gaussian TOF kernel that depends on the timing resolution and blob basis functions for regularization. We use lesion phantoms and clinically relevant metrics for lesion detectability and contrast measurement. The scan time was fixed at 10 min for imaging a 100 cm long object assuming a 50% overlap between adjacent bed positions. Results show that a 72 cm long scanner can provide a factor of ten reduction in injected activity compared to an identical 18 cm long scanner to get equivalent lesion detectability. While improved timing resolution leads to further gains, using 3 mm (as opposed to 4 mm) wide crystals does not show any significant benefits for lesion detectability. A detector providing 2-level DOI information with equal crystal thickness also does not show significant gains. Finally, a 15 mm thick crystal leads to lower lesion detectability than a 20 mm thick crystal when keeping all other detector parameters (crystal width, timing resolution, and DOI capability) the same. However, improved timing performance with 15 mm thick crystals can provide similar or better performance than that achieved by a detector using 20 mm thick crystals.

TandemPET-A High Resolution, Small Animal, Virtual Pinhole-Based PET Scanner: Initial Design Study

NASA Astrophysics Data System (ADS)

Raylman, Raymond R.; Stolin, Alexander V.; Martone, Peter F.; Smith, Mark F.

2016-02-01

Mice are the perhaps the most common species of rodents used in biomedical research, but many of the current generation of small animal PET scanners are non-optimal for imaging these small rodents due to their relatively low resolution. Consequently, a number of researchers have investigated the development of high-resolution scanners to address this need. In this investigation, the design of a novel, high-resolution system based on the dual-detector, virtual-pinhole PET concept was explored via Monte Carlo simulations. Specifically, this system, called TandemPET, consists of a 5 cm × 5 cm high-resolution detector made-up of a 90 × 90 array of 0.5 mm × 0.5 × 10 mm (pitch = 0.55 mm) LYSO detector elements in coincidence with a lower resolution detector consisting of a 68 × 68 array of 1.5 mm × 1.5 mm × 10 mm LYSO detector elements (total size = 10.5 cm × 10.5 cm). Analyses indicated that TandemPET's optimal geometry is to position the high-resolution detector 3 cm from the center-of-rotation, with the lower resolution detector positioned 9 cm from center. Measurements using modified NEMA NU4-2008-based protocols revealed that the spatial resolution of the system is 0.5 mm FWHM, after correction of positron range effects. Peak sensitivity is 2.1%, which is comparable to current small animal PET scanners. Images from a digital mouse brain phantom demonstrated the potential of the system for identifying important neurological structures.

Characterization of Pixelated Cadmium-Zinc-Telluride Detectors for Astrophysical Applications

NASA Technical Reports Server (NTRS)

Gaskin, Jessica; Sharma, Dharma; Ramsey, Brian; Seller, Paul

2003-01-01

Comparisons of charge sharing and charge loss measurements between two pixelated Cadmium-Zinc-Telluride (CdZnTe) detectors are discussed. These properties along with the detector geometry help to define the limiting energy resolution and spatial resolution of the detector in question. The first detector consists of a 1-mm-thick piece of CdZnTe sputtered with a 4x4 array of pixels with pixel pitch of 750 microns (inter-pixel gap is 100 microns). Signal readout is via discrete ultra-low-noise preamplifiers, one for each of the 16 pixels. The second detector consists of a 2-mm-thick piece of CdZnTe sputtered with a 16x16 array of pixels with a pixel pitch of 300 microns (inter-pixel gap is 50 microns). This crystal is bonded to a custom-built readout chip (ASIC) providing all front-end electronics to each of the 256 independent pixels. These detectors act as precursors to that which will be used at the focal plane of the High Energy Replicated Optics (HERO) telescope currently being developed at Marshall Space Flight Center. With a telescope focal length of 6 meters, the detector needs to have a spatial resolution of around 200 microns in order to take full advantage of the HERO angular resolution. We discuss to what degree charge sharing will degrade energy resolution but will improve our spatial resolution through position interpolation.

Improved image quality in pinhole SPECT by accurate modeling of the point spread function in low magnification systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pino, Francisco; Roé, Nuria; Aguiar, Pablo, E-mail: pablo.aguiar.fernandez@sergas.es

2015-02-15

Purpose: Single photon emission computed tomography (SPECT) has become an important noninvasive imaging technique in small-animal research. Due to the high resolution required in small-animal SPECT systems, the spatially variant system response needs to be included in the reconstruction algorithm. Accurate modeling of the system response should result in a major improvement in the quality of reconstructed images. The aim of this study was to quantitatively assess the impact that an accurate modeling of spatially variant collimator/detector response has on image-quality parameters, using a low magnification SPECT system equipped with a pinhole collimator and a small gamma camera. Methods: Threemore » methods were used to model the point spread function (PSF). For the first, only the geometrical pinhole aperture was included in the PSF. For the second, the septal penetration through the pinhole collimator was added. In the third method, the measured intrinsic detector response was incorporated. Tomographic spatial resolution was evaluated and contrast, recovery coefficients, contrast-to-noise ratio, and noise were quantified using a custom-built NEMA NU 4–2008 image-quality phantom. Results: A high correlation was found between the experimental data corresponding to intrinsic detector response and the fitted values obtained by means of an asymmetric Gaussian distribution. For all PSF models, resolution improved as the distance from the point source to the center of the field of view increased and when the acquisition radius diminished. An improvement of resolution was observed after a minimum of five iterations when the PSF modeling included more corrections. Contrast, recovery coefficients, and contrast-to-noise ratio were better for the same level of noise in the image when more accurate models were included. Ring-type artifacts were observed when the number of iterations exceeded 12. Conclusions: Accurate modeling of the PSF improves resolution, contrast, and recovery coefficients in the reconstructed images. To avoid the appearance of ring-type artifacts, the number of iterations should be limited. In low magnification systems, the intrinsic detector PSF plays a major role in improvement of the image-quality parameters.« less

Development of a Scintillation Detector and the Influence on Clinical Imaging

NASA Astrophysics Data System (ADS)

Panetta, Joseph Vincent

The detector is the functional unit within a Positron Emission Tomography (PET) scanner, serving to convert the energy of radiation emitted from a patient into positional information, and as such contributes significantly to the performance of the scanner. Excellent spatial resolution in continuous detectors that are thick has proven difficult to achieve using simple positioning algorithms, leading to research in the field to improve performance. This thesis aims to investigate the effect of modifications to the scintillation light spread within the bulk of the scintillator to improve performance, focusing on the use of laser induced optical barriers (LIOBs) etched within thick continuous crystals, and furthermore aims to translate the effect on detector performance to scanner quantitation in patient studies. The conventional continuous detector is first investigated by analyzing the various components of the detector as well as its limitations. It is seen that the performance of the detector is affected by a number of variables that either cannot be improved or may be improved only at the expense of greater complexity or computing time; these include the photodetector, the positioning algorithm, and Compton scatter in the detector. The performance of the detectors, however, is fundamentally determined by the light spread within the detector, and limited by the depth-dependence of the light spread and poor performance in the entrance region, motivating efforts to modify this aspect of the detector. The feasibility and potential of LIOBs to fine-tune this light spread and improve these limitations is then studied using both experiments and simulations. The behavior of the LIOBs in response to optical light is investigated, and the opacity of the etchings is shown to be dependent on the parameters of the etching procedure. Thick crystals were also etched with LIOBs in their entrance region in a grid pattern in order to improve the resolution in the entrance region. Measurements show an overall improvement in spatial resolution: the resolution in the etched region of the crystals is slightly improved (e.g., 0.8mm for a 25mm thick crystal), though in the unetched region, it is slightly degraded (e.g., 0.4mm for a 25mm thick crystal). While the depth-dependence of the response of the crystal is decreased, the depth-of-interaction (DOI) performance is degraded as well. Simulation studies informed by these measurements show that the properties of the LIOBs strongly affect the performance of the crystal, and ultimately further illustrate that trade-offs in spatial resolution, position sampling, and DOI resolution are inherent in varying the light spread using LIOBs in this manner; these may be used as a guide for future experiments. System Monte Carlo simulations were used to investigate the added benefit of improved detector spatial resolution and position sampling to the imaging performance of a whole-body scanner. These simulations compared the performance of scanners composed of conventional pixelated detectors to that of scanners using continuous crystals. Results showed that the improved performance (relative to that of 4-mm pixelated detectors) of continuous crystals with a 2-mm resolution, pertinent to both the etched 14mm thick crystal studied as well as potential designs with the etched 25mm thick crystal, increased the mean contrast recovery coefficient (CRC) of images by 22% for 5.5mm spheres. Last, a set of experiments aimed to test the correspondence between quantification in phantom and patient images using a lesion embedding methodology, so that any improvements determined using phantom studies may be understood clinically. The results show that the average CRC values for lesions embedded in the lung and liver agree well with those for lesions embedded in the phantom for all lesion sizes. In addition, the relative changes in CRC resulting from application of post-filters on the subject and phantom images are consistent within measurement uncertainty. This study shows that the improvements in CRC resulting from improved spatial resolution, measured using phantom studies in the simulations, are representative of improvements in quantitative accuracy in patient studies. While unmodified thick continuous detectors hold promise for both improved image quality and quantitation in whole-body imaging, excellent performance requires intensive hardware and computational solutions. Laser induced optical barriers offer the ability to modify the light spread within the scintillator to improve the intrinsic performance of the detector: while measurements with crystals etched with relatively transmissive etchings show a slight improvement in resolution, simulations show that the LIOBs may be fine-tuned to result in improved performance using relatively simple positioning algorithms. For systems in which DOI information is less important, and transverse resolution and sensitivity are paramount, etching thick detectors with this design, fine-tuned to the particular thickness of the crystal and application, is an interesting alternative to the standard detector design. (Abstract shortened by ProQuest.).

Energy resolution improvement of CdTe detectors by using the principal component analysis technique

NASA Astrophysics Data System (ADS)

Alharbi, T.

2018-02-01

In this paper, we report on the application of the Principal Component Analysis (PCA) technique for the improvement of the γ-ray energy resolution of CdTe detectors. The PCA technique is used to estimate the amount of charge-trapping effect which is reflected in the shape of each detector pulse, thereby correcting for the charge-trapping effect. The details of the method are described and the results obtained with a CdTe detector are shown. We have achieved an energy resolution of 1.8 % (FWHM) at 662 keV with full detection efficiency from a 1 mm thick CdTe detector which gives an energy resolution of 4.5 % (FWHM) by using the standard pulse processing method.

High-resolution x-ray imaging using a structured scintillator.

PubMed

Hormozan, Yashar; Sychugov, Ilya; Linnros, Jan

2016-02-01

In this study, the authors introduce a new generation of finely structured scintillators with a very high spatial resolution (a few micrometers) compared to conventional scintillators, yet maintaining a thick absorbing layer for improved detectivity. Their concept is based on a 2D array of high aspect ratio pores which are fabricated by ICP etching, with spacings (pitches) of a few micrometers, on silicon and oxidation of the pore walls. The pores were subsequently filled by melting of powdered CsI(Tl), as the scintillating agent. In order to couple the secondary emitted photons of the back of the scintillator array to a CCD device, having a larger pixel size than the pore pitch, an open optical microscope with adjustable magnification was designed and implemented. By imaging a sharp edge, the authors were able to calculate the modulation transfer function (MTF) of this finely structured scintillator. The x-ray images of individually resolved pores suggest that they have been almost uniformly filled, and the MTF measurements show the feasibility of a few microns spatial resolution imaging, as set by the scintillator pore size. Compared to existing techniques utilizing CsI needles as a structured scintillator, their results imply an almost sevenfold improvement in resolution. Finally, high resolution images, taken by their detector, are presented. The presented work successfully shows the functionality of their detector concept for high resolution imaging and further fabrication developments are most likely to result in higher quantum efficiencies.

High-resolution x-ray imaging using a structured scintillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hormozan, Yashar, E-mail: hormozan@kth.se; Sychugov, Ilya; Linnros, Jan

2016-02-15

Purpose: In this study, the authors introduce a new generation of finely structured scintillators with a very high spatial resolution (a few micrometers) compared to conventional scintillators, yet maintaining a thick absorbing layer for improved detectivity. Methods: Their concept is based on a 2D array of high aspect ratio pores which are fabricated by ICP etching, with spacings (pitches) of a few micrometers, on silicon and oxidation of the pore walls. The pores were subsequently filled by melting of powdered CsI(Tl), as the scintillating agent. In order to couple the secondary emitted photons of the back of the scintillator arraymore » to a CCD device, having a larger pixel size than the pore pitch, an open optical microscope with adjustable magnification was designed and implemented. By imaging a sharp edge, the authors were able to calculate the modulation transfer function (MTF) of this finely structured scintillator. Results: The x-ray images of individually resolved pores suggest that they have been almost uniformly filled, and the MTF measurements show the feasibility of a few microns spatial resolution imaging, as set by the scintillator pore size. Compared to existing techniques utilizing CsI needles as a structured scintillator, their results imply an almost sevenfold improvement in resolution. Finally, high resolution images, taken by their detector, are presented. Conclusions: The presented work successfully shows the functionality of their detector concept for high resolution imaging and further fabrication developments are most likely to result in higher quantum efficiencies.« less

Improving Technology for Vascular Imaging

NASA Astrophysics Data System (ADS)

Rana, Raman

Neuro-endovascular image guided interventions (Neuro-EIGIs) is a minimally invasive procedure that require micro catheters and endovascular devices be inserted into the vasculature via an incision near the femoral artery and guided under low dose fluoroscopy to the vasculature of the head and neck. However, the endovascular devices used for the purpose are of very small size (stents are of the order of 50mum to 100mum) and the success of these EIGIs depends a lot on the accurate placement of these devices. In order to accurately place these devices inside the patient, the interventionalist should be able to see them clearly. Hence, high resolution capabilities are of immense importance in neuro-EIGIs. The high-resolution detectors, MAF-CCD and MAF-CMOS, at the Toshiba Stroke and Vascular Research Center at the University at Buffalo are capable of presenting improved images for better patient care. Focal spot of an x-ray tube plays an important role in performance of these high resolution detectors. The finite size of the focal spot results into the blurriness around the edges of the image of the object resulting in reduced spatial resolution. Hence, knowledge of accurate size of the focal spot of the x-ray tube is very essential for the evaluation of the total system performance. Importance of magnification and image detector blur deconvolution was demonstrated to carry out the more accurate measurement of x-ray focal spot using a pinhole camera. A 30 micron pinhole was used to obtain the focal spot images using flat panel detector (FPD) and different source to image distances (SIDs) were used to achieve different magnifications (3.16, 2.66 and 2.16). These focal spot images were deconvolved with a 2-D modulation transfer function (MTF), obtained using noise response (NR) method, to remove the detector blur present in the images. Using these corrected images, the accurate size of all the three focal spots were obtained and it was also established that effect of detector blur can be reduced significantly by using a higher magnification. As discussed earlier, interventionalist need higher resolution capabilities during EIGIs for more confident and successful treatment of the patient. An experimental MAF-CCD enabled with a Control, Acquisition, Processing, Image Display and Storage (CAPIDS) system was installed and aligned on a detector changer attached to the C-arm of a clinical angiographic unit. The CAPIDS system was developed and implemented using LabVIEW software and provides a user-friendly interface that enables control of several clinical radiographic imaging modes of the MAF including: fluoroscopy, roadmap, radiography, and digital-subtraction-angiography (DSA). Whenever the higher resolution is needed, the MAD-CCD detector can be moved in front of the FPD. A particular set of steps were needed to deploy the MAF in front of the FPD and to transfer the controls to CAPIDS from the Toshiba Systems. In order to minimize any possible negative impact of using two different detectors during a procedure, a well-designed workflow was developed that enables smooth deployment of the MAF at critical stages of clinical procedures. The images obtained using MAF-CCD detector demonstrated the advantages the high resolution imagers have over FPDs. Scatter is inevitable in x-ray imaging as it reduces the image quality. The benefit of removing the scatter is that it improves contrast and also increases the signal-to-Noise (SNR). There are various scatter reduction methods like air-gap techniques, collimation, moving anti-scatter grids, stationary anti-scatter grids. Stationary anti-scatter grids is a preferred choice in dynamic imaging because of its compact design and ease to use. However, when these anti-scatter grids are used with high resolution detector, there will be anti-scatter grid-line pattern present in the image, as structure noise. Because of presence of this anti-scatter grid artifact, the contrast-to-Noise (CNR) of the image decreases when grid is used with high resolution detector. In order to address this issue, grid-line artifact minimization method for high resolution detectors is developed. (Abstract shortened by ProQuest.).

Scientific Benefit of Enlarging Gravitational Wave Detector Networks

NASA Astrophysics Data System (ADS)

Chu, Qi; Wen, Linqing; Blair, David

2012-06-01

Localising the sources of gravitational waves (GWs) in the sky is crucial to observing the electromagnetic counterparts of GW sources. The localisation capability is poor by a single GW detector yet can be improved by adding more detectors to the detector network. In this paper we review recent studies on scientific benefits of global detector networks and focus on their localisation capability. We employ Wen-Chen's formula to compare this merit of current and future detector networks for localising gravitational wave bursts. We find that the addition of a new detector located in Japan, or India, or Australia will increase angular resolution 3~5 fold with respect to current LIGO-Virgo network, and that the angular resolution improvement by adding a single detector in Australia is comparable to that achieved by adding detectors in both India and Japan. A six-site network achieves a 11-fold improvement in angular resolution compared with the existing three-site network.

Cryogenic, high-resolution x-ray detector with high count rate capability

DOEpatents

Frank, Matthias; Mears, Carl A.; Labov, Simon E.; Hiller, Larry J.; Barfknecht, Andrew T.

2003-03-04

A cryogenic, high-resolution X-ray detector with high count rate capability has been invented. The new X-ray detector is based on superconducting tunnel junctions (STJs), and operates without thermal stabilization at or below 500 mK. The X-ray detector exhibits good resolution (.about.5-20 eV FWHM) for soft X-rays in the keV region, and is capable of counting at count rates of more than 20,000 counts per second (cps). Simple, FET-based charge amplifiers, current amplifiers, or conventional spectroscopy shaping amplifiers can provide the electronic readout of this X-ray detector.

Non-contact time-domain imaging of functional brain activation and heterogeneity of superficial signals

NASA Astrophysics Data System (ADS)

Wabnitz, H.; Mazurenka, M.; Di Sieno, L.; Contini, D.; Dalla Mora, A.; Farina, A.; Hoshi, Y.; Kirilina, E.; Macdonald, R.; Pifferi, A.

2017-07-01

Non-contact scanning at small source-detector separation enables imaging of cerebral and extracranial signals at high spatial resolution and their separation based on early and late photons accounting for the related spatio-temporal characteristics.

Physics of cardiac imaging with multiple-row detector CT.

PubMed

Mahesh, Mahadevappa; Cody, Dianna D

2007-01-01

Cardiac imaging with multiple-row detector computed tomography (CT) has become possible due to rapid advances in CT technologies. Images with high temporal and spatial resolution can be obtained with multiple-row detector CT scanners; however, the radiation dose associated with cardiac imaging is high. Understanding the physics of cardiac imaging with multiple-row detector CT scanners allows optimization of cardiac CT protocols in terms of image quality and radiation dose. Knowledge of the trade-offs between various scan parameters that affect image quality--such as temporal resolution, spatial resolution, and pitch--is the key to optimized cardiac CT protocols, which can minimize the radiation risks associated with these studies. Factors affecting temporal resolution include gantry rotation time, acquisition mode, and reconstruction method; factors affecting spatial resolution include detector size and reconstruction interval. Cardiac CT has the potential to become a reliable tool for noninvasive diagnosis and prevention of cardiac and coronary artery disease. (c) RSNA, 2007.

Cadmium Telluride Semiconductor Detector for Improved Spatial and Energy Resolution Radioisotopic Imaging

PubMed Central

Abbaspour, Samira; Mahmoudian, Babak; Islamian, Jalil Pirayesh

2017-01-01

The detector in single-photon emission computed tomography has played a key role in the quality of the images. Over the past few decades, developments in semiconductor detector technology provided an appropriate substitution for scintillation detectors in terms of high sensitivity, better energy resolution, and also high spatial resolution. One of the considered detectors is cadmium telluride (CdTe). The purpose of this paper is to review the CdTe semiconductor detector used in preclinical studies, small organ and small animal imaging, also research in nuclear medicine and other medical imaging modalities by a complete inspect on the material characteristics, irradiation principles, applications, and epitaxial growth method. PMID:28553175

Requirements on high resolution detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koch, A.

For a number of microtomography applications X-ray detectors with a spatial resolution of 1 {mu}m are required. This high spatial resolution will influence and degrade other parameters of secondary importance like detective quantum efficiency (DQE), dynamic range, linearity and frame rate. This note summarizes the most important arguments, for and against those detector systems which could be considered. This article discusses the mutual dependencies between the various figures which characterize a detector, and tries to give some ideas on how to proceed in order to improve present technology.

Development of depth encoding small animal PET detectors using dual-ended readout of pixelated scintillator arrays with SiPMs.

PubMed

Kuang, Zhonghua; Sang, Ziru; Wang, Xiaohui; Fu, Xin; Ren, Ning; Zhang, Xianming; Zheng, Yunfei; Yang, Qian; Hu, Zhanli; Du, Junwei; Liang, Dong; Liu, Xin; Zheng, Hairong; Yang, Yongfeng

2018-02-01

The performance of current small animal PET scanners is mainly limited by the detector performance and depth encoding detectors are required to develop PET scanner to simultaneously achieve high spatial resolution and high sensitivity. Among all depth encoding PET detector approaches, dual-ended readout detector has the advantage to achieve the highest depth of interaction (DOI) resolution and spatial resolution. Silicon photomultiplier (SiPM) is believed to be the photodetector of the future for PET detector due to its excellent properties as compared to the traditional photodetectors such as photomultiplier tube (PMT) and avalanche photodiode (APD). The purpose of this work is to develop high resolution depth encoding small animal PET detector using dual-ended readout of finely pixelated scintillator arrays with SiPMs. Four lutetium-yttrium oxyorthosilicate (LYSO) arrays with 11 × 11 crystals and 11.6 × 11.6 × 20 mm 3 outside dimension were made using ESR, Toray and BaSO 4 reflectors. The LYSO arrays were read out with Hamamatsu 4 × 4 SiPM arrays from both ends. The SiPM array has a pixel size of 3 × 3 mm 2 , 0.2 mm gap in between the pixels and a total active area of 12.6 × 12.6 mm 2 . The flood histograms, DOI resolution, energy resolution and timing resolution of the four detector modules were measured and compared. All crystals can be clearly resolved from the measured flood histograms of all four arrays. The BaSO 4 arrays provide the best and the ESR array provides the worst flood histograms. The DOI resolution obtained from the DOI profiles of the individual crystals of the four array is from 2.1 to 2.35 mm for events with E > 350 keV. The DOI ratio variation among crystals is bigger for the BaSO 4 arrays as compared to both the ESR and Toray arrays. The BaSO 4 arrays provide worse detector based DOI resolution. The photopeak amplitude of the Toray array had the maximum change with depth, it provides the worst energy resolution of 21.3%. The photopeak amplitude of the BaSO 4 array with 80 μm reflector almost doesn't change with depth, it provides the best energy resolution of 12.9%. A maximum timing shift of 1.37 ns to 1.61 ns among the corner and the center crystals in the four arrays was obtained due to the use of resistor network readout. A crystal based timing resolution of 0.68 ns to 0.83 ns and a detector based timing resolution of 1.26 ns to 1.45 ns were obtained for the four detector modules. Four high resolution depth encoding small animal PET detectors were developed using dual-ended readout of pixelated scintillator arrays with SiPMs. The performance results show that those detectors can be used to build a small animal PET scanner to simultaneously achieve uniform high spatial resolution and high sensitivity. © 2017 American Association of Physicists in Medicine.

High-resolution imaging gamma-ray spectroscopy with externally segmented germanium detectors

NASA Technical Reports Server (NTRS)

Callas, J. L.; Mahoney, W. A.; Varnell, L. S.; Wheaton, W. A.

1993-01-01

Externally segmented germanium detectors promise a breakthrough in gamma-ray imaging capabilities while retaining the superb energy resolution of germanium spectrometers. An angular resolution of 0.2 deg becomes practical by combining position-sensitive germanium detectors having a segment thickness of a few millimeters with a one-dimensional coded aperture located about a meter from the detectors. Correspondingly higher angular resolutions are possible with larger separations between the detectors and the coded aperture. Two-dimensional images can be obtained by rotating the instrument. Although the basic concept is similar to optical or X-ray coded-aperture imaging techniques, several complicating effects arise because of the penetrating nature of gamma rays. The complications include partial transmission through the coded aperture elements, Compton scattering in the germanium detectors, and high background count rates. Extensive electron-photon Monte Carlo modeling of a realistic detector/coded-aperture/collimator system has been performed. Results show that these complicating effects can be characterized and accounted for with no significant loss in instrument sensitivity.

Surface Passivation of CdZnTe Detector by Hydrogen Peroxide Solution Etching

NASA Technical Reports Server (NTRS)

Hayes, M.; Chen, H.; Chattopadhyay, K.; Burger, A.; James, R. B.

1998-01-01

The spectral resolution of room temperature nuclear radiation detectors such as CdZnTe is usually limited by the presence of conducting surface species that increase the surface leakage current. Studies have shown that the leakage current can be reduced by proper surface preparation. In this study, we try to optimize the performance of CdZnTe detector by etching the detector with hydrogen peroxide solution as function of concentration and etching time. The passivation effect that hydrogen peroxide introduces have been investigated by current-voltage (I-V) measurement on both parallel strips and metal-semiconductor-metal configurations. The improvements on the spectral response of Fe-55 and 241Am due to hydrogen peroxide treatment are presented and discussed.

A depth-of-interaction PET detector using mutual gain-equalized silicon photomultiplier

DOE Office of Scientific and Technical Information (OSTI.GOV)

W. Xi, A.G, Weisenberger, H. Dong, Brian Kross, S. Lee, J. McKisson, Carl Zorn

We developed a prototype high resolution, high efficiency depth-encoding detector for PET applications based on dual-ended readout of LYSO array with two silicon photomultipliers (SiPMs). Flood images, energy resolution, and depth-of-interaction (DOI) resolution were measured for a LYSO array - 0.7 mm in crystal pitch and 10 mm in thickness - with four unpolished parallel sides. Flood images were obtained such that individual crystal element in the array is resolved. The energy resolution of the entire array was measured to be 33%, while individual crystal pixel elements utilizing the signal from both sides ranged from 23.3% to 27%. By applyingmore » a mutual-gain equalization method, a DOI resolution of 2 mm for the crystal array was obtained in the experiments while simulations indicate {approx}1 mm DOI resolution could possibly be achieved. The experimental DOI resolution can be further improved by obtaining revised detector supporting electronics with better energy resolutions. This study provides a detailed detector calibration and DOI response characterization of the dual-ended readout SiPM-based PET detectors, which will be important in the design and calibration of a PET scanner in the future.« less

Monte Carlo simulation of the resolution volume for the SEQUOIA spectrometer

NASA Astrophysics Data System (ADS)

Granroth, G. E.; Hahn, S. E.

2015-01-01

Monte Carlo ray tracing simulations, of direct geometry spectrometers, have been particularly useful in instrument design and characterization. However, these tools can also be useful for experiment planning and analysis. To this end, the McStas Monte Carlo ray tracing model of SEQUOIA, the fine resolution fermi chopper spectrometer at the Spallation Neutron Source (SNS) of Oak Ridge National Laboratory (ORNL), has been modified to include the time of flight resolution sample and detector components. With these components, the resolution ellipsoid can be calculated for any detector pixel and energy bin of the instrument. The simulation is split in two pieces. First, the incident beamline up to the sample is simulated for 1 × 1011 neutron packets (4 days on 30 cores). This provides a virtual source for the backend that includes the resolution sample and monitor components. Next, a series of detector and energy pixels are computed in parallel. It takes on the order of 30 s to calculate a single resolution ellipsoid on a single core. Python scripts have been written to transform the ellipsoid into the space of an oriented single crystal, and to characterize the ellipsoid in various ways. Though this tool is under development as a planning tool, we have successfully used it to provide the resolution function for convolution with theoretical models. Specifically, theoretical calculations of the spin waves in YFeO3 were compared to measurements taken on SEQUOIA. Though the overall features of the spectra can be explained while neglecting resolution effects, the variation in intensity of the modes is well described once the resolution is included. As this was a single sharp mode, the simulated half intensity value of the resolution ellipsoid was used to provide the resolution width. A description of the simulation, its use, and paths forward for this technique will be discussed.

Modeling and measurement of the detector presampling MTF of a variable resolution x-ray CT scanner

PubMed Central

Melnyk, Roman; DiBianca, Frank A.

2007-01-01

The detector presampling MTF of a 576-channel variable resolution x-ray (VRX) CT scanner was evaluated in this study. The scanner employs a VRX detector, which provides increased spatial resolution by matching the scanner’s field of view (FOV) to the size of an object being imaged. Because spatial resolution is the parameter the scanner promises to improve, the evaluation of this resolution is important. The scanner’s pre-reconstruction spatial resolution, represented by the detector presampling MTF, was evaluated using both modeling (Monte Carlo simulation) and measurement (the moving slit method). The theoretical results show the increase in the cutoff frequency of the detector presampling MTF from 1.39 cy/mm to 43.38 cy/mm as the FOV of the VRX CT scanner decreases from 32 cm to 1 cm. The experimental results are in reasonable agreement with the theoretical data. Some discrepancies between the measured and the modeled detector presampling MTFs can be explained by the limitations of the model. At small FOVs (1–8 cm), the MTF measurements were limited by the size of the focal spot. The obtained results are important for further development of the VRX CT scanner. PMID:17369872

Evaluation of PET Imaging Resolution Using 350 mu{m} Pixelated CZT as a VP-PET Insert Detector

NASA Astrophysics Data System (ADS)

Yin, Yongzhi; Chen, Ximeng; Li, Chongzheng; Wu, Heyu; Komarov, Sergey; Guo, Qingzhen; Krawczynski, Henric; Meng, Ling-Jian; Tai, Yuan-Chuan

2014-02-01

A cadmium-zinc-telluride (CZT) detector with 350 μm pitch pixels was studied in high-resolution positron emission tomography (PET) imaging applications. The PET imaging system was based on coincidence detection between a CZT detector and a lutetium oxyorthosilicate (LSO)-based Inveon PET detector in virtual-pinhole PET geometry. The LSO detector is a 20 ×20 array, with 1.6 mm pitches, and 10 mm thickness. The CZT detector uses ac 20 ×20 ×5 mm substrate, with 350 μm pitch pixelated anodes and a coplanar cathode. A NEMA NU4 Na-22 point source of 250 μm in diameter was imaged by this system. Experiments show that the image resolution of single-pixel photopeak events was 590 μm FWHM while the image resolution of double-pixel photopeak events was 640 μm FWHM. The inclusion of double-pixel full-energy events increased the sensitivity of the imaging system. To validate the imaging experiment, we conducted a Monte Carlo (MC) simulation for the same PET system in Geant4 Application for Emission Tomography. We defined LSO detectors as a scanner ring and 350 μm pixelated CZT detectors as an insert ring. GATE simulated coincidence data were sorted into an insert-scanner sinogram and reconstructed. The image resolution of MC-simulated data (which did not factor in positron range and acolinearity effect) was 460 μm at FWHM for single-pixel events. The image resolutions of experimental data, MC simulated data, and theoretical calculation are all close to 500 μm FWHM when the proposed 350 μm pixelated CZT detector is used as a PET insert. The interpolation algorithm for the charge sharing events was also investigated. The PET image that was reconstructed using the interpolation algorithm shows improved image resolution compared with the image resolution without interpolation algorithm.

Towards a microchannel-based X-ray detector with two-dimensional spatial and time resolution and high dynamic range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adams, Bernhard W.; Mane, Anil U.; Elam, Jeffrey W.

X-ray detectors that combine two-dimensional spatial resolution with a high time resolution are needed in numerous applications of synchrotron radiation. Most detectors with this combination of capabilities are based on semiconductor technology and are therefore limited in size. Furthermore, the time resolution is often realised through rapid time-gating of the acquisition, followed by a slower readout. Here, a detector technology is realised based on relatively inexpensive microchannel plates that uses GHz waveform sampling for a millimeter-scale spatial resolution and better than 100 ps time resolution. The technology is capable of continuous streaming of time- and location-tagged events at rates greatermore » than 10 7events per cm 2. Time-gating can be used for improved dynamic range.« less

A high time resolution x-ray diagnostic on the Madison Symmetric Torus

NASA Astrophysics Data System (ADS)

DuBois, Ami M.; Lee, John David; Almagri, Abdulgadar F.

2015-07-01

A new high time resolution x-ray detector has been installed on the Madison Symmetric Torus (MST) to make measurements around sawtooth events. The detector system is comprised of a silicon avalanche photodiode, a 20 ns Gaussian shaping amplifier, and a 500 MHz digitizer with 14-bit sampling resolution. The fast shaping time diminishes the need to restrict the amount of x-ray flux reaching the detector, limiting the system dead-time. With a much higher time resolution than systems currently in use in high temperature plasma physics experiments, this new detector has the versatility to be used in a variety of discharges with varying flux and the ability to study dynamics on both slow and fast time scales. This paper discusses the new fast x-ray detector recently installed on MST and the improved time resolution capabilities compared to the existing soft and hard x-ray diagnostics. In addition to the detector hardware, improvements to the detector calibration and x-ray pulse identification software, such as additional fitting parameters and a more sophisticated fitting routine are discussed. Finally, initial data taken in both high confinement and standard reversed-field pinch plasma discharges are compared.

Characterization of scintillator-based detectors for few-ten-keV high-spatial-resolution x-ray imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Larsson, Jakob C., E-mail: jakob.larsson@biox.kth.se; Lundström, Ulf; Hertz, Hans M.

2016-06-15

Purpose: High-spatial-resolution x-ray imaging in the few-ten-keV range is becoming increasingly important in several applications, such as small-animal imaging and phase-contrast imaging. The detector properties critically influence the quality of such imaging. Here the authors present a quantitative comparison of scintillator-based detectors for this energy range and at high spatial frequencies. Methods: The authors determine the modulation transfer function, noise power spectrum (NPS), and detective quantum efficiency for Gadox, needle CsI, and structured CsI scintillators of different thicknesses and at different photon energies. An extended analysis of the NPS allows for direct measurements of the scintillator effective absorption efficiency andmore » effective light yield as well as providing an alternative method to assess the underlying factors behind the detector properties. Results: There is a substantial difference in performance between the scintillators depending on the imaging task but in general, the CsI based scintillators perform better than the Gadox scintillators. At low energies (16 keV), a thin needle CsI scintillator has the best performance at all frequencies. At higher energies (28–38 keV), the thicker needle CsI scintillators and the structured CsI scintillator all have very good performance. The needle CsI scintillators have higher absorption efficiencies but the structured CsI scintillator has higher resolution. Conclusions: The choice of scintillator is greatly dependent on the imaging task. The presented comparison and methodology will assist the imaging scientist in optimizing their high-resolution few-ten-keV imaging system for best performance.« less

Characterization of scintillator-based detectors for few-ten-keV high-spatial-resolution x-ray imaging.

PubMed

Larsson, Jakob C; Lundström, Ulf; Hertz, Hans M

2016-06-01

High-spatial-resolution x-ray imaging in the few-ten-keV range is becoming increasingly important in several applications, such as small-animal imaging and phase-contrast imaging. The detector properties critically influence the quality of such imaging. Here the authors present a quantitative comparison of scintillator-based detectors for this energy range and at high spatial frequencies. The authors determine the modulation transfer function, noise power spectrum (NPS), and detective quantum efficiency for Gadox, needle CsI, and structured CsI scintillators of different thicknesses and at different photon energies. An extended analysis of the NPS allows for direct measurements of the scintillator effective absorption efficiency and effective light yield as well as providing an alternative method to assess the underlying factors behind the detector properties. There is a substantial difference in performance between the scintillators depending on the imaging task but in general, the CsI based scintillators perform better than the Gadox scintillators. At low energies (16 keV), a thin needle CsI scintillator has the best performance at all frequencies. At higher energies (28-38 keV), the thicker needle CsI scintillators and the structured CsI scintillator all have very good performance. The needle CsI scintillators have higher absorption efficiencies but the structured CsI scintillator has higher resolution. The choice of scintillator is greatly dependent on the imaging task. The presented comparison and methodology will assist the imaging scientist in optimizing their high-resolution few-ten-keV imaging system for best performance.

Light-Sharing Interface for dMiCE Detectors Using Sub-Surface Laser Engraving

PubMed Central

Hunter, William C. J.; Miyaoka, Robert S.; MacDonald, Lawrence; McDougald, Wendy; Lewellen, Thomas K.

2015-01-01

We have previously reported on dMiCE, a method of resolving depth or interaction (DOI) in a pair of discrete crystals by encoding light sharing properties as a function of depth in the interface of a crystal-element pair. A challenge for this method is the cost and repeatability of interface treatment for each crystal pair. In this work, we report our preliminary results on using sub-surface laser engraving (SSLE) as a means of forming this depth-dependent interface in a dMiCE detector. A surplus first-generation SSLE system was used to create a partially reflective layer 100-microns thick at the boundary between two halves of a 1.4-by-2.9-by-20 mm3 LYSO crystal. The boundary of these paired crystal elements was positioned between two 3-mm wide Silicon photomultiplier arrays. The responses of these two photodetectors were acquired for an ensemble of 511-keV photons collimated to interact at a fixed depth in just one crystal element. Interaction position was then varied to measure detector response as a function of depth, which was then used to maximum-likelihood positions. Despite use of sub-optimal SSLE processing we found an average DOI resolution of 3.4 mm for front-sided readout and 3.9 mm for back-sided readout while obtaining energy resolutions on the order of 10%. We expect DOI resolution can be improved significantly by optimizing the SSLE process and pattern. PMID:25914421

Light-Sharing Interface for dMiCE Detectors Using Sub-Surface Laser Engraving.

PubMed

Hunter, William C J; Miyaoka, Robert S; MacDonald, Lawrence; McDougald, Wendy; Lewellen, Thomas K

2015-02-06

We have previously reported on dMiCE, a method of resolving depth or interaction (DOI) in a pair of discrete crystals by encoding light sharing properties as a function of depth in the interface of a crystal-element pair. A challenge for this method is the cost and repeatability of interface treatment for each crystal pair. In this work, we report our preliminary results on using sub-surface laser engraving (SSLE) as a means of forming this depth-dependent interface in a dMiCE detector. A surplus first-generation SSLE system was used to create a partially reflective layer 100-microns thick at the boundary between two halves of a 1.4-by-2.9-by-20 mm 3 LYSO crystal. The boundary of these paired crystal elements was positioned between two 3-mm wide Silicon photomultiplier arrays. The responses of these two photodetectors were acquired for an ensemble of 511-keV photons collimated to interact at a fixed depth in just one crystal element. Interaction position was then varied to measure detector response as a function of depth, which was then used to maximum-likelihood positions. Despite use of sub-optimal SSLE processing we found an average DOI resolution of 3.4 mm for front-sided readout and 3.9 mm for back-sided readout while obtaining energy resolutions on the order of 10%. We expect DOI resolution can be improved significantly by optimizing the SSLE process and pattern.

Optimization of an on-board imaging system for extremely rapid radiation therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cherry Kemmerling, Erica M.; Wu, Meng, E-mail: mengwu@stanford.edu; Yang, He

2015-11-15

Purpose: Next-generation extremely rapid radiation therapy systems could mitigate the need for motion management, improve patient comfort during the treatment, and increase patient throughput for cost effectiveness. Such systems require an on-board imaging system that is competitively priced, fast, and of sufficiently high quality to allow good registration between the image taken on the day of treatment and the image taken the day of treatment planning. In this study, three different detectors for a custom on-board CT system were investigated to select the best design for integration with an extremely rapid radiation therapy system. Methods: Three different CT detectors aremore » proposed: low-resolution (all 4 × 4 mm pixels), medium-resolution (a combination of 4 × 4 mm pixels and 2 × 2 mm pixels), and high-resolution (all 1 × 1 mm pixels). An in-house program was used to generate projection images of a numerical anthropomorphic phantom and to reconstruct the projections into CT datasets, henceforth called “realistic” images. Scatter was calculated using a separate Monte Carlo simulation, and the model included an antiscatter grid and bowtie filter. Diagnostic-quality images of the phantom were generated to represent the patient scan at the time of treatment planning. Commercial deformable registration software was used to register the diagnostic-quality scan to images produced by the various on-board detector configurations. The deformation fields were compared against a “gold standard” deformation field generated by registering initial and deformed images of the numerical phantoms that were used to make the diagnostic and treatment-day images. Registrations of on-board imaging system data were judged by the amount their deformation fields differed from the corresponding gold standard deformation fields—the smaller the difference, the better the system. To evaluate the registrations, the pointwise distance between gold standard and realistic registration deformation fields was computed. Results: By most global metrics (e.g., mean, median, and maximum pointwise distance), the high-resolution detector had the best performance but the medium-resolution detector was comparable. For all medium- and high-resolution detector registrations, mean error between the realistic and gold standard deformation fields was less than 4 mm. By pointwise metrics (e.g., tracking a small lesion), the high- and medium-resolution detectors performed similarly. For these detectors, the smallest error between the realistic and gold standard registrations was 0.6 mm and the largest error was 3.6 mm. Conclusions: The medium-resolution CT detector was selected as the best for an extremely rapid radiation therapy system. In essentially all test cases, data from this detector produced a significantly better registration than data from the low-resolution detector and a comparable registration to data from the high-resolution detector. The medium-resolution detector provides an appropriate compromise between registration accuracy and system cost.« less

Application of Timepix3 based CdTe spectral sensitive photon counting detector for PET imaging

NASA Astrophysics Data System (ADS)

Turecek, Daniel; Jakubek, Jan; Trojanova, Eliska; Sefc, Ludek; Kolarova, Vera

2018-07-01

Positron emission tomography (PET) is a nuclear medicine functional imaging technique. It is used in clinical oncology (medical imaging of tumors and the search for metastases), and pre-clinical studies using animals. PET uses small amounts of radioactive materials (radiotracers) and a special photon sensitive camera. Most of these cameras use scintillators with photomultipliers as detectors. However, these detectors have limited energy sensitivity and large pixels. Therefore, the false signal caused by a scattering poses a significant problem. In this work we study properties of position, energy and time sensitive semiconductor detector of Timepix3 type and its applicability for PET measurements. This work presents an initial study and evaluation of two Timepix3 detectors with 2 mm thick CdTe sensors used in simplified geometry for PET imaging. The study is performed on 2 samples - a capillary tube and a cylindrical plexiglass phantom with cavities. Both samples are filled with fluodeoxyglucose (FDG) solution that is used as a radiotracer. The Timepix3 offers better properties compared to conventional detectors - high granularity (55 μm pixel pitch), good energy resolution (1 keV at 60 keV) and sufficient time resolution (1.6 ns). The spectral sensitivity of Timepix3 together with coincidence/anticoincidence technique allows for significant reduction of background signal caused by Compton scattering and internal X-ray fluorescence of Cd and Te.

Sub-millimetre DOI detector based on monolithic LYSO and digital SiPM for a dedicated small-animal PET system.

PubMed

Marcinkowski, Radosław; Mollet, Pieter; Van Holen, Roel; Vandenberghe, Stefaan

2016-03-07

The mouse model is widely used in a vast range of biomedical and preclinical studies. Thanks to the ability to detect and quantify biological processes at the molecular level in vivo, PET has become a well-established tool in these investigations. However, the need to visualize and quantify radiopharmaceuticals in anatomic structures of millimetre or less requires good spatial resolution and sensitivity from small-animal PET imaging systems.In previous work we have presented a proof-of-concept of a dedicated high-resolution small-animal PET scanner based on thin monolithic scintillator crystals and Digital Photon Counter photosensor. The combination of thin monolithic crystals and MLE positioning algorithm resulted in an excellent spatial resolution of 0.7 mm uniform in the entire field of view (FOV). However, the limitation of the scanner was its low sensitivity due to small thickness of the lutetium-yttrium oxyorthosilicate (LYSO) crystals (2 mm).Here we present an improved detector design for a small-animal PET system that simultaneously achieves higher sensitivity and sustains a sub-millimetre spatial resolution. The proposed detector consists of a 5 mm thick monolithic LYSO crystal optically coupled to a Digital Photon Counter. Mean nearest neighbour (MNN) positioning combined with depth of interaction (DOI) decoding was employed to achieve sub-millimetre spatial resolution. To evaluate detector performance the intrinsic spatial resolution, energy resolution and coincidence resolving time (CRT) were measured. The average intrinsic spatial resolution of the detector was 0.60 mm full-width-at-half-maximum (FWHM). A DOI resolution of 1.66 mm was achieved. The energy resolution was 23% FWHM at 511 keV and CRT of 529 ps were measured. The improved detector design overcomes the sensitivity limitation of the previous design by increasing the nominal sensitivity of the detector block and retains an excellent intrinsic spatial resolution.

Characterization of Sensitivity Encoded Silicon Photomultiplier (SeSP) with 1-Dimensional and 2-Dimensional Encoding for High Resolution PET/MR

NASA Astrophysics Data System (ADS)

Omidvari, Negar; Schulz, Volkmar

2015-06-01

This paper evaluates the performance of a new type of PET detectors called sensitivity encoded silicon photomultiplier (SeSP), which allows a direct coupling of small-pitch crystal arrays to the detector with a reduction in the number of readout channels. Four SeSP devices with two separate encoding schemes of 1D and 2D were investigated in this study. Furthermore, both encoding schemes were manufactured in two different sizes of 4 ×4 mm2 and 7. 73 ×7. 9 mm2, in order to investigate the effect of size on detector parameters. All devices were coupled to LYSO crystal arrays with 1 mm pitch size and 10 mm height, with optical isolation between crystals. The characterization was done for the key parameters of crystal-identification, energy resolution, and time resolution as a function of triggering threshold and over-voltage (OV). Position information was archived using the center of gravity (CoG) algorithm and a least squares approach (LSQA) in combination with a mean light matrix around the photo-peak. The positioning results proved the capability of all four SeSP devices in precisely identifying all crystals coupled to the sensors. Energy resolution was measured at different bias voltages, varying from 12% to 18% (FWHM) and paired coincidence time resolution (pCTR) of 384 ps to 1.1 ns was obtained for different SeSP devices at about 18 °C room temperature. However, the best time resolution was achieved at the highest over-voltage, resulting in a noise ratio of 99.08%.

Development of a high-resolution liquid xenon detector for gamma-ray astrophysics

NASA Astrophysics Data System (ADS)

Mukherjee, Reshmi

It has been shown here that liquid xenon is one of the most promising detector media for future gamma-ray detectors, owing to an excellent combination of physical properties. The feasibility of the construction of a high resolution liquid xenon detector as a gamma-ray detector for astrophysics has been demonstrated. Up to 3.5 liters of liquid xenon has been successfully purified and using both small and large volume prototypes, the charge and the energy resolution response of such detectors to gamma-rays, internal conversion electrons and alpha particles have been measured. The best energy resolution measured was 4.5 percent FWHM at 1 MeV. Cosmic ray tracks have been imaged using a 2-dimensional liquid xenon multiwire imaging chamber. The spatial resolution along the direction of the drifting electrons was 180 microns rms. Experiments have been performed to study the scintillation light in liquid xenon, as the prompt scintillation signal in the liquid is an electron-ion pair in liquid krypton was measured for the first time with a pulsed ionization chamber to be 18.4 plus or minus 0.3 eV.

Reconstructed Image Spatial Resolution of Multiple Coincidences Compton Imager

NASA Astrophysics Data System (ADS)

Andreyev, Andriy; Sitek, Arkadiusz; Celler, Anna

2010-02-01

We study the multiple coincidences Compton imager (MCCI) which is based on a simultaneous acquisition of several photons emitted in cascade from a single nuclear decay. Theoretically, this technique should provide a major improvement in localization of a single radioactive source as compared to a standard Compton camera. In this work, we investigated the performance and limitations of MCCI using Monte Carlo computer simulations. Spatial resolutions of the reconstructed point source have been studied as a function of the MCCI parameters, including geometrical dimensions and detector characteristics such as materials, energy and spatial resolutions.

Organic Scintillator Detector Response Simulations with DRiFT

DOE PAGES

Andrews, Madison Theresa; Bates, Cameron Russell; Mckigney, Edward Allen; ...

2016-06-11

Here, this work presents the organic scintillation simulation capabilities of DRiFT, a post-processing Detector Response Function Toolkit for MCNPR output. DRiFT is used to create realistic scintillation detector response functions to incident neutron and gamma mixed- field radiation. As a post-processing tool, DRiFT leverages the extensively validated radiation transport capabilities of MCNPR ®6, which also provides the ability to simulate complex sources and geometries. DRiFT is designed to be flexible, it allows the user to specify scintillator material, PMT type, applied PMT voltage, and quenching data used in simulations. The toolkit's capabilities, which include the generation of pulse shape discriminationmore » plots and full-energy detector spectra, are demonstrated in a comparison of measured and simulated neutron contributions from 252Cf and PuBe, and photon spectra from 22Na and 228Th sources. DRiFT reproduced energy resolution effects observed in EJ-301 measurements through the inclusion of scintillation yield variances, photon transport noise, and PMT photocathode and multiplication noise.« less

Organic scintillator detector response simulations with DRiFT

NASA Astrophysics Data System (ADS)

Andrews, M. T.; Bates, C. R.; McKigney, E. A.; Solomon, C. J.; Sood, A.

2016-09-01

This work presents the organic scintillation simulation capabilities of DRiFT, a post-processing Detector Response Function Toolkit for MCNP® output. DRiFT is used to create realistic scintillation detector response functions to incident neutron and gamma mixed-field radiation. As a post-processing tool, DRiFT leverages the extensively validated radiation transport capabilities of MCNP® 6 , which also provides the ability to simulate complex sources and geometries. DRiFT is designed to be flexible, it allows the user to specify scintillator material, PMT type, applied PMT voltage, and quenching data used in simulations. The toolkit's capabilities, which include the generation of pulse shape discrimination plots and full-energy detector spectra, are demonstrated in a comparison of measured and simulated neutron contributions from 252Cf and PuBe, and photon spectra from 22Na and 228Th sources. DRiFT reproduced energy resolution effects observed in EJ-301 measurements through the inclusion of scintillation yield variances, photon transport noise, and PMT photocathode and multiplication noise.

Characterization of on-site digital mammography systems: Direct versus indirect conversion detectors

NASA Astrophysics Data System (ADS)

Youn, Hanbean; Han, Jong Chul; Yun, Seungman; Kam, Soohwa; Cho, Seungryong; Kim, Ho Kyung

2015-06-01

We investigated the performances of two digital mammography systems. The systems use a cesium-iodide (CsI) scintillator and an amorphous selenium ( a-Se) photoconductor for X-ray detection and are installed in the same hospital. As physical metrics, we measured the modulationtransfer function (MTF), the noise-power spectrum (NPS), and the detective quantum efficiency (DQE). In addition, we analyzed the contrast-detail performances of the two systems by using a commercial contrast-detail phantom. The CsI-based indirect conversion detector provided better MTF and DQE performances than the a-Se-based direct conversion detector whereas the former provided a poorer NPS performance than the latter. These results are explained by the fact that the CsI-based detector used an MTF restoration preprocessing algorithm. The a-Se-based detector showed better contrast-detail performance than the CsI-based detector. We believe that the highfrequency noise characteristic of a detector is more responsible for the visibility of small details than its spatial-resolution performance.

Angular resolution of the gaseous micro-pixel detector Gossip

NASA Astrophysics Data System (ADS)

Bilevych, Y.; Blanco Carballo, V.; van Dijk, M.; Fransen, M.; van der Graaf, H.; Hartjes, F.; Hessey, N.; Koppert, W.; Nauta, S.; Rogers, M.; Romaniouk, A.; Veenhof, R.

2011-06-01

Gossip is a gaseous micro-pixel detector with a very thin drift gap intended for a high rate environment like at the pixel layers of ATLAS at the sLHC. The detector outputs not only the crossing point of a traversing MIP, but also the angle of the track, thus greatly simplifying track reconstruction. In this paper we describe a testbeam experiment to examine the angular resolution of the reconstructed track segments in Gossip. We used here the low diffusion gas mixture DME/CO 2 50/50. An angular resolution of 20 mrad for perpendicular tracks could be obtained from a 1.5 mm thin drift volume. However, for the prototype detector used at the testbeam experiment, the resolution of slanting tracks was worsened by poor time resolution of the pixel chip used.

A new imaging method for understanding chemical dynamics: efficient slice imaging using an in-vacuum pixel detector.

PubMed

Jungmann, J H; Gijsbertsen, A; Visser, J; Visschers, J; Heeren, R M A; Vrakking, M J J

2010-10-01

The implementation of the Timepix complementary metal oxide semiconductor pixel detector in velocity map slice imaging is presented. This new detector approach eliminates the need for gating the imaging detector. In time-of-flight mode, the detector returns the impact position and the time-of-flight of charged particles with 12.5 ns resolution and a dynamic range of about 100 μs. The implementation of the Timepix detector in combination with a microchannel plate additionally allows for high spatial resolution information via center-of-mass centroiding. Here, the detector was applied to study the photodissociation of NO(2) at 452 nm. The energy resolution observed in the experiment was ΔE/E=0.05 and is limited by the experimental setup rather than by the detector assembly. All together, this new compact detector assembly is well-suited for slice imaging and is a promising tool for imaging studies in atomic and molecular physics research.

Design and performance of a high spatial resolution, time-of-flight PET detector

PubMed Central

Krishnamoorthy, Srilalan; LeGeyt, Benjamin; Werner, Matthew E.; Kaul, Madhuri; Newcomer, F. M.; Karp, Joel S.; Surti, Suleman

2014-01-01

This paper describes the design and performance of a high spatial resolution PET detector with time-of-flight capabilities. With an emphasis on high spatial resolution and sensitivity, we initially evaluated the performance of several 1.5 × 1.5 and 2.0 × 2.0 mm2 and 12–15 mm long LYSO crystals read out by several appropriately sized PMTs. Experiments to evaluate the impact of reflector on detector performance were performed and the final detector consisted of a 32 × 32 array of 1.5 × 1.5 × 15 mm3 LYSO crystals packed with a diffuse reflector and read out by a single Hamamatsu 64 channel multi-anode PMT. Such a design made it compact, modular and offered a cost-effective solution to obtaining excellent energy and timing resolution. To minimize the number of readout signals, a compact front-end readout electronics that summed anode signals along each of the orthogonal directions was also developed. Experimental evaluation of detector performance demonstrates clear discrimination of the crystals within the detector. An average energy resolution (FWHM) of 12.7 ± 2.6% and average coincidence timing resolution (FWHM) of 348 ps was measured, demonstrating suitability for use in the development of a high spatial resolution time-of-flight scanner for dedicated breast PET imaging. PMID:25246711

Study of a high-resolution PET system using a Silicon detector probe

NASA Astrophysics Data System (ADS)

Brzeziński, K.; Oliver, J. F.; Gillam, J.; Rafecas, M.

2014-10-01

A high-resolution silicon detector probe, in coincidence with a conventional PET scanner, is expected to provide images of higher quality than those achievable using the scanner alone. Spatial resolution should improve due to the finer pixelization of the probe detector, while increased sensitivity in the probe vicinity is expected to decrease noise. A PET-probe prototype is being developed utilizing this principle. The system includes a probe consisting of ten layers of silicon detectors, each a 80 × 52 array of 1 × 1 × 1 mm3 pixels, to be operated in coincidence with a modern clinical PET scanner. Detailed simulation studies of this system have been performed to assess the effect of the additional probe information on the quality of the reconstructed images. A grid of point sources was simulated to study the contribution of the probe to the system resolution at different locations over the field of view (FOV). A resolution phantom was used to demonstrate the effect on image resolution for two probe positions. A homogeneous source distribution with hot and cold regions was used to demonstrate that the localized improvement in resolution does not come at the expense of the overall quality of the image. Since the improvement is constrained to an area close to the probe, breast imaging is proposed as a potential application for the novel geometry. In this sense, a simplified breast phantom, adjacent to heart and torso compartments, was simulated and the effect of the probe on lesion detectability, through measurements of the local contrast recovery coefficient-to-noise ratio (CNR), was observed. The list-mode ML-EM algorithm was used for image reconstruction in all cases. As expected, the point spread function of the PET-probe system was found to be non-isotropic and vary with position, offering improvement in specific regions. Increase in resolution, of factors of up to 2, was observed in the region close to the probe. Images of the resolution phantom showed visible improvement in resolution when including the probe in the simulations. The image quality study demonstrated that contrast and spill-over ratio in other areas of the FOV were not sacrificed for this enhancement. The CNR study performed on the breast phantom indicates increased lesion detectability provided by the probe.

CZT drift strip detectors for high energy astrophysics

NASA Astrophysics Data System (ADS)

Kuvvetli, I.; Budtz-Jørgensen, C.; Caroli, E.; Auricchio, N.

2010-12-01

Requirements for X- and gamma ray detectors for future High Energy Astrophysics missions include high detection efficiency and good energy resolution as well as fine position sensitivity even in three dimensions. We report on experimental investigations on the CZT drift detector developed DTU Space. It is operated in the planar transverse field (PTF) mode, with the purpose of demonstrating that the good energy resolution of the CZT drift detector can be combined with the high efficiency of the PTF configuration. Furthermore, we demonstrated and characterized the 3D sensing capabilities of this detector configuration. The CZT drift strip detector (10 mm×10 mm×2.5 mm) was characterized in both standard illumination geometry, Photon Parallel Field (PPF) configuration and in PTF configuration. The detection efficiency and energy resolution are compared for both configurations . The PTF configuration provided a higher efficiency in agreement with calculations. The detector energy resolution was found to be the same (3 keV FWHM at 122 keV) in both in PPF and PTF . The depth sensing capabilities offered by drift strip detectors was investigated by illuminating the detector using a collimated photon beam of 57Co radiation in PTF configuration. The width (300μm FWHM at 122 keV) of the measured depth distributions was almost equal to the finite beam size. However, the data indicate that the best achievable depth resolution for the CZT drift detector is 90μm FWHM at 122 keV and that it is determined by the electronic noise from the setup.

Three-dimensional cascaded system analysis of a 50 µm pixel pitch wafer-scale CMOS active pixel sensor x-ray detector for digital breast tomosynthesis.

PubMed

Zhao, C; Vassiljev, N; Konstantinidis, A C; Speller, R D; Kanicki, J

2017-03-07

High-resolution, low-noise x-ray detectors based on the complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) technology have been developed and proposed for digital breast tomosynthesis (DBT). In this study, we evaluated the three-dimensional (3D) imaging performance of a 50 µm pixel pitch CMOS APS x-ray detector named DynAMITe (Dynamic Range Adjustable for Medical Imaging Technology). The two-dimensional (2D) angle-dependent modulation transfer function (MTF), normalized noise power spectrum (NNPS), and detective quantum efficiency (DQE) were experimentally characterized and modeled using the cascaded system analysis at oblique incident angles up to 30°. The cascaded system model was extended to the 3D spatial frequency space in combination with the filtered back-projection (FBP) reconstruction method to calculate the 3D and in-plane MTF, NNPS and DQE parameters. The results demonstrate that the beam obliquity blurs the 2D MTF and DQE in the high spatial frequency range. However, this effect can be eliminated after FBP image reconstruction. In addition, impacts of the image acquisition geometry and detector parameters were evaluated using the 3D cascaded system analysis for DBT. The result shows that a wider projection angle range (e.g.  ±30°) improves the low spatial frequency (below 5 mm -1 ) performance of the CMOS APS detector. In addition, to maintain a high spatial resolution for DBT, a focal spot size of smaller than 0.3 mm should be used. Theoretical analysis suggests that a pixelated scintillator in combination with the 50 µm pixel pitch CMOS APS detector could further improve the 3D image resolution. Finally, the 3D imaging performance of the CMOS APS and an indirect amorphous silicon (a-Si:H) thin-film transistor (TFT) passive pixel sensor (PPS) detector was simulated and compared.

Three-dimensional cascaded system analysis of a 50 µm pixel pitch wafer-scale CMOS active pixel sensor x-ray detector for digital breast tomosynthesis

NASA Astrophysics Data System (ADS)

Zhao, C.; Vassiljev, N.; Konstantinidis, A. C.; Speller, R. D.; Kanicki, J.

2017-03-01

High-resolution, low-noise x-ray detectors based on the complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) technology have been developed and proposed for digital breast tomosynthesis (DBT). In this study, we evaluated the three-dimensional (3D) imaging performance of a 50 µm pixel pitch CMOS APS x-ray detector named DynAMITe (Dynamic Range Adjustable for Medical Imaging Technology). The two-dimensional (2D) angle-dependent modulation transfer function (MTF), normalized noise power spectrum (NNPS), and detective quantum efficiency (DQE) were experimentally characterized and modeled using the cascaded system analysis at oblique incident angles up to 30°. The cascaded system model was extended to the 3D spatial frequency space in combination with the filtered back-projection (FBP) reconstruction method to calculate the 3D and in-plane MTF, NNPS and DQE parameters. The results demonstrate that the beam obliquity blurs the 2D MTF and DQE in the high spatial frequency range. However, this effect can be eliminated after FBP image reconstruction. In addition, impacts of the image acquisition geometry and detector parameters were evaluated using the 3D cascaded system analysis for DBT. The result shows that a wider projection angle range (e.g.  ±30°) improves the low spatial frequency (below 5 mm-1) performance of the CMOS APS detector. In addition, to maintain a high spatial resolution for DBT, a focal spot size of smaller than 0.3 mm should be used. Theoretical analysis suggests that a pixelated scintillator in combination with the 50 µm pixel pitch CMOS APS detector could further improve the 3D image resolution. Finally, the 3D imaging performance of the CMOS APS and an indirect amorphous silicon (a-Si:H) thin-film transistor (TFT) passive pixel sensor (PPS) detector was simulated and compared.

Fine-Pitch CdTe Detector for Hard X-Ray Imaging and Spectroscopy of the Sun with the FOXSI Rocket Experiment

NASA Technical Reports Server (NTRS)

Ishikawa, Shin-nosuke; Katsuragawa, Miho; Watanabe, Shin; Uchida, Yuusuke; Takeda, Shin'lchiro; Takahashi, Tadayuki; Saito, Shinya; Glesener, Lindsay; Bultrago-Casas, Juan Camilo; Krucker, Sam;

Fine-pitch CdTe detector for hard X-ray imaging and spectroscopy of the Sun with the FOXSI rocket experiment

NASA Astrophysics Data System (ADS)

Ishikawa, Shin-nosuke; Katsuragawa, Miho; Watanabe, Shin; Uchida, Yuusuke; Takeda, Shin'ichiro; Takahashi, Tadayuki; Saito, Shinya; Glesener, Lindsay; Buitrago-Casas, Juan Camilo; Krucker, Säm.; Christe, Steven

2016-07-01

We have developed a fine-pitch hard X-ray (HXR) detector using a cadmium telluride (CdTe) semiconductor for imaging and spectroscopy for the second launch of the Focusing Optics Solar X-ray Imager (FOXSI). FOXSI is a rocket experiment to perform high sensitivity HXR observations from 4 to 15 keV using the new technique of HXR focusing optics. The focal plane detector requires <100μm position resolution (to take advantage of the angular resolution of the optics) and ≈1 keV energy resolution (full width at half maximum (FWHM)) for spectroscopy down to 4 keV, with moderate cooling (>-30°C). Double-sided silicon strip detectors were used for the first FOXSI flight in 2012 to meet these criteria. To improve the detectors' efficiency (66% at 15 keV for the silicon detectors) and position resolution of 75 μm for the second launch, we fabricated double-sided CdTe strip detectors with a position resolution of 60 μm and almost 100% efficiency for the FOXSI energy range. The sensitive area is 7.67 mm × 7.67 mm, corresponding to the field of view of 791'' × 791''. An energy resolution of 1 keV (FWHM) and low-energy threshold of ≈4 keV were achieved in laboratory calibrations. The second launch of FOXSI was performed on 11 December 2014, and images from the Sun were successfully obtained with the CdTe detector. Therefore, we successfully demonstrated the detector concept and the usefulness of this technique for future HXR observations of the Sun.

WE-G-204-05: Relative Object Detectability Evaluation of a New High Resolution A-Se Direct Detection System Compared to Indirect Micro-Angiographic Fluoroscopic (MAF) Detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russ, M; Nagesh, S Setlur; Ionita, C

2015-06-15

Purpose: To evaluate the task specific imaging performance of a new 25µm pixel pitch, 1000µm thick amorphous selenium direct detection system with CMOS readout for typical angiographic exposure parameters using the relative object detectability (ROD) metric. Methods: The ROD metric uses a simulated object function weighted at each spatial frequency by the detectors’ detective quantum efficiency (DQE), which is an intrinsic performance metric. For this study, the simulated objects were aluminum spheres of varying diameter (0.05–0.6mm). The weighted object function is then integrated over the full range of detectable frequencies inherent to each detector, and a ratio is taken ofmore » the resulting value for two detectors. The DQE for the 25µm detector was obtained from a simulation of a proposed a-Se detector using an exposure of 200µR for a 50keV x-ray beam. This a-Se detector was compared to two microangiographic fluoroscope (MAF) detectors [the MAF-CCD with pixel size of 35µm and Nyquist frequency of 14.2 cycles/mm and the MAF-CMOS with pixel size of 75µm and Nyquist frequency of 6.6 cycles/mm] and a standard flat-panel detector (FPD with pixel size of 194µm and Nyquist frequency of 2.5cycles/mm). Results: ROD calculations indicated vastly superior performance by the a-Se detector in imaging small aluminum spheres. For the 50µm diameter sphere, the ROD values for the a-Se detector compared to the MAF-CCD, the MAF-CMOS, and the FPD were 7.3, 9.3 and 58, respectively. Detector performance in the low frequency regime was dictated by each detector’s DQE(0) value. Conclusion: The a-Se with CMOS readout is unique and appears to have distinctive advantages of incomparable high resolution, low noise, no readout lag, and expandable design. The a-Se direct detection system will be a powerful imaging tool in angiography, with potential break-through applications in diagnosis and treatment of neuro-vascular disease. Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation.« less

Study of the Dependency on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter

NASA Technical Reports Server (NTRS)

Gottardi, L.; Bruijn, M.; denHartog, R.; Hoevers, H.; deKorte, P.; vanderKuur, J.; Linderman, M.; Adams, J.; Bailey, C.; Bandler, S.;

A system definition study for the Advanced Meteorological Temperature Sounder (AMTS)

NASA Technical Reports Server (NTRS)

1977-01-01

The functional requirements of Exhibit A (11) were used as the baseline for the conceptual design of a fixed grating out of plane multidetector spectrometer for the Space Shuttle application. Because the grating instrument would be large and the 28 element detector array would be difficult to cool radiatively from a free flying spacecraft and because increasing the spectral resolution of the grating instrument would be difficult in an instrument of reasonable size, a parallel study of a Nichelson interferometer spectrometer was undertaken. This type of instrument offers compact size, fewer detectors to cool, and the possibility of increased spectral resolution. The design and performance parameters of both the grating and interferometer approaches are described. The tradeoffs involved in comparing the two systems for sounding applications are discussed.

Study of the Dependence on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter

NASA Technical Reports Server (NTRS)

Bandler, Simon

2011-01-01

At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in the AC bias configuration. For x-ray photons at 6keV the AC biased pixel shows a best energy resolution of 3.7eV, which is about a factor of 2 worse than the energy resolution observed in identical DC-biased pixels. To better understand the reasons of this discrepancy, we investigated the detector performance as a function of temperature, bias working point and applied magnetic field. A strong periodic dependence of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recent weak-link behaviour observed inTES microcalorimeters.

Particle tracking with a Timepix based triple GEM detector

NASA Astrophysics Data System (ADS)

George, S. P.; Murtas, F.; Alozy, J.; Curioni, A.; Rosenfeld, A. B.; Silari, M.

2015-11-01

This paper details the response of a triple GEM detector with a 55 μmetre pitch pixelated ASIC for readout. The detector is operated as a micro TPC with 9.5 cm3 sensitive volume and characterized with a mixed beam of 120 GeV protons and positive pions. A process for reconstruction of incident particle tracks from individual ionization clusters is described and scans of the gain and drift fields are performed. The angular resolution of the measured tracks is characterized. Also, the readout was operated in a mixed mode where some pixels measure drift time and others charge. This was used to measure the energy deposition in the detector and the charge cloud size as a function of interaction depth. The future uses of the device, including in microdosimetry are discussed.

Event Centroiding Applied to Energy-Resolved Neutron Imaging at LANSCE

DOE PAGES

Borges, Nicholas; Losko, Adrian; Vogel, Sven

2018-02-13

The energy-dependence of the neutron cross section provides vastly different contrast mechanisms than polychromatic neutron radiography if neutron energies can be selected for imaging applications. In recent years, energy-resolved neutron imaging (ERNI) with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as for quantitative density measurements, was pioneered at the Flight Path 5 beam line at LANSCE and continues to be refined. In this work, we present event centroiding, i.e., the determination of the center-of-gravity of a detection event on an imaging detector to allow sub-pixel spatial resolution and apply it to the many frames collected for energy-resolvedmore » neutron imaging at a pulsed neutron source. While event centroiding was demonstrated at thermal neutron sources, it has not been applied to energy-resolved neutron imaging, where the energy resolution requires to be preserved, and we present a quantification of the possible resolution as a function of neutron energy. For the 55 μm pixel size of the detector used for this study, we found a resolution improvement from ~80 μm to ~22 μm using pixel centroiding while fully preserving the energy resolution.« less

Event Centroiding Applied to Energy-Resolved Neutron Imaging at LANSCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borges, Nicholas; Losko, Adrian; Vogel, Sven

The energy-dependence of the neutron cross section provides vastly different contrast mechanisms than polychromatic neutron radiography if neutron energies can be selected for imaging applications. In recent years, energy-resolved neutron imaging (ERNI) with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as for quantitative density measurements, was pioneered at the Flight Path 5 beam line at LANSCE and continues to be refined. In this work, we present event centroiding, i.e., the determination of the center-of-gravity of a detection event on an imaging detector to allow sub-pixel spatial resolution and apply it to the many frames collected for energy-resolvedmore » neutron imaging at a pulsed neutron source. While event centroiding was demonstrated at thermal neutron sources, it has not been applied to energy-resolved neutron imaging, where the energy resolution requires to be preserved, and we present a quantification of the possible resolution as a function of neutron energy. For the 55 μm pixel size of the detector used for this study, we found a resolution improvement from ~80 μm to ~22 μm using pixel centroiding while fully preserving the energy resolution.« less

Energy straggling eliminated as a limitation to charge resolution of transmission detectors. [used for particle identification

NASA Technical Reports Server (NTRS)

Tarle, G.; Ahlen, S. P.; Price, P. B.

1981-01-01

It is pointed out that detectors of the energy loss of penetrating charged particles are widely used for particle identification. These measurements are hampered, however, by fluctuations in the amount of energy deposited within the detector. It is shown that this limitation can be overcome with a new nuclear track detector, CR-39(DOP), and that the charge resolution of this detector exceeds that of any other, including semiconductor diodes.

Fabrication and characterization of a 0.5-mm lutetium oxyorthosilicate detector array for high-resolution PET applications.

PubMed

Stickel, Jennifer R; Qi, Jinyi; Cherry, Simon R

2007-01-01

With the increasing use of in vivo imaging in mouse models of disease, there are many interesting applications that demand imaging of organs and tissues with submillimeter resolution. Though there are other contributing factors, the spatial resolution in small-animal PET is still largely determined by the detector pixel dimensions. In this work, a pair of lutetium oxyorthosilicate (LSO) arrays with 0.5-mm pixels was coupled to multichannel photomultiplier tubes and evaluated for use as high-resolution PET detectors. Flood histograms demonstrated that most crystals were clearly identifiable. Energy resolution varied from 22% to 38%. The coincidence timing resolution was 1.42-ns full width at half maximum (FWHM). The intrinsic spatial resolution was 0.68-mm FWHM as measured with a 30-gauge needle filled with (18)F. The improvement in spatial resolution in a tomographic setting is demonstrated using images of a line source phantom reconstructed with filtered backprojection and compared with images obtained from 2 dedicated small-animal PET scanners. Finally, a projection image of the mouse foot is shown to demonstrate the application of these 0.5-mm LSO detectors to a biologic task. A pair of highly pixelated LSO detections has been constructed and characterized for use as high-spatial-resolution PET detectors. It appears that small-animal PET systems capable of a FWHM spatial resolution of 600 microm or less are feasible and should be pursued.

Characterization of a 2-mm thick, 16x16 Cadmium-Zinc-Telluride Pixel Array

NASA Technical Reports Server (NTRS)

Gaskin, Jessica; Richardson, Georgia; Mitchell, Shannon; Ramsey, Brian; Seller, Paul; Sharma, Dharma

2003-01-01

The detector under study is a 2-mm-thick, 16x16 Cadmium-Zinc-Telluride pixel array with a pixel pitch of 300 microns and inter-pixel gap of 50 microns. This detector is a precursor to that which will be used at the focal plane of the High Energy Replicated Optics (HERO) telescope currently being developed at Marshall Space Flight Center. With a telescope focal length of 6 meters, the detector needs to have a spatial resolution of around 200 microns in order to take full advantage of the HERO angular resolution. We discuss to what degree charge sharing will degrade energy resolution but will improve our spatial resolution through position interpolation. In addition, we discuss electric field modeling for this specific detector geometry and the role this mapping will play in terms of charge sharing and charge loss in the detector.

Development of MMC Gamma Detectors for Nuclear Analysis

NASA Astrophysics Data System (ADS)

Bates, C. R.; Pies, C.; Kempf, S.; Gastaldo, L.; Fleischmann, A.; Enss, C.; Friedrich, S.

2014-09-01

Non-destructive assay (NDA) of nuclear materials would benefit from gamma detectors with improved energy resolution in cases where line overlap in current Ge detectors limits NDA accuracy. We are developing metallic magnetic calorimeter gamma-detectors for this purpose by electroplating 150 m thick Au absorbers into microfabricated molds on top of Au:Er sensors. Initial tests under non-optimized conditions show an energy resolution of 200 eV FWHM at 60 keV. Monte Carlo simulations illustrate that this resolution is starting to be sufficient for direct detection of Pu in plutonium separated from spent nuclear fuel.

High Resolution PET Imaging Probe for the Detection, Molecular Characterization and Treatment Monitoring of Prostate Cancer

DTIC Science & Technology

2012-07-01

Jitter results from electronic noise and from the fact that the shape of the detector signal used for timing can vary considerably depending on the...photomultiplier technology, several “probe” detectors were developed. It was predicted, and subsequently shown, that probes having good position...high spatial resolution for prostate imaging. Practical proof-of-concept detectors with good depth-of-interactions resolution have been developed and

High resolution micro-CT of low attenuating organic materials using large area photon-counting detector

NASA Astrophysics Data System (ADS)

Kumpová, I.; Vavřík, D.; Fíla, T.; Koudelka, P.; Jandejsek, I.; Jakůbek, J.; Kytýř, D.; Zlámal, P.; Vopálenský, M.; Gantar, A.

2016-02-01

To overcome certain limitations of contemporary materials used for bone tissue engineering, such as inflammatory response after implantation, a whole new class of materials based on polysaccharide compounds is being developed. Here, nanoparticulate bioactive glass reinforced gelan-gum (GG-BAG) has recently been proposed for the production of bone scaffolds. This material offers promising biocompatibility properties, including bioactivity and biodegradability, with the possibility of producing scaffolds with directly controlled microgeometry. However, to utilize such a scaffold with application-optimized properties, large sets of complex numerical simulations using the real microgeometry of the material have to be carried out during the development process. Because the GG-BAG is a material with intrinsically very low attenuation to X-rays, its radiographical imaging, including tomographical scanning and reconstructions, with resolution required by numerical simulations might be a very challenging task. In this paper, we present a study on X-ray imaging of GG-BAG samples. High-resolution volumetric images of investigated specimens were generated on the basis of micro-CT measurements using a large area flat-panel detector and a large area photon-counting detector. The photon-counting detector was composed of a 010× 1 matrix of Timepix edgeless silicon pixelated detectors with tiling based on overlaying rows (i.e. assembled so that no gap is present between individual rows of detectors). We compare the results from both detectors with the scanning electron microscopy on selected slices in transversal plane. It has been shown that the photon counting detector can provide approx. 3× better resolution of the details in low-attenuating materials than the integrating flat panel detectors. We demonstrate that employment of a large area photon counting detector is a good choice for imaging of low attenuating materials with the resolution sufficient for numerical simulations.

Four-arm variable-resolution x-ray detector for CT target imaging

NASA Astrophysics Data System (ADS)

DiBianca, Frank A.; Gulabani, Daya; Jordan, Lawrence M.; Vangala, Sravanthi; Rendon, David; Laughter, Joseph S.; Melnyk, Roman; Gaber, M. W.; Keyes, Gary S.

2005-04-01

The basic VRX technique boosts spatial resolution of a CT scanner in the scan plane by two or more orders of magnitude by reducing the angle of incidence of the x-ray beam with respect to the detector surface. A four-arm Variable-Resolution X-ray (VRX) detector has been developed for CT scanning. The detector allows for "target imaging" in which an area of interest is scanned at higher resolution than the remainder of the subject, yielding even higher resolution for the focal area than that obtained from the basic VRX technique. The new VRX-CT detector comprises four quasi-identical arms each containing six 24-cell modules (576 cells total). The modules are made of individual custom CdWO4 scintillators optically-coupled to custom photodiode arrays. The maximum scan field is 40 cm for a magnification of 1.4. A significant advantage of the four-arm geometry is that it can transform quickly to the two-arm, or even the single-arm geometry, for comparison studies. These simpler geometries have already been shown experimentally to yield in-plane CT detector resolution exceeding 60 cy/mm (<8μ) for small fields of view. Geometrical size and resolution limits of the target VRX field are calculated. Two-arm VRX-CT data are used to simulate and establish the feasibility of VRX CT target imaging. A prototype target VRX-CT scanner has been built and is undergoing initial testing.

Large-area field-ionization detector for the study of Rydberg atoms.

PubMed

Jones, A C L; Piñeiro, A M; Roeder, E E; Rutbeck-Goldman, H J; Tom, H W K; Mills, A P

2016-11-01

We describe here the development and characterization of a micro-channel plate (MCP) based detector designed for the efficient collection and detection of Rydberg positronium (Ps) atoms for use in a time-of-flight apparatus. The designed detector collects Rydberg atoms over a large area (∼4 times greater than the active area of the MCP), ionizing incident atoms and then collecting and focusing the freed positrons onto the MCP. Here we discuss the function, design, and optimization of the device. The detector has an efficiency for Rydberg Ps that is two times larger than that of the γ-ray scintillation detector based scheme it has been designed to replace, with half the background signal. In principle, detectors of the type described here could be readily employed for the detection of any Rydberg atom species, provided a sufficient field can be applied to achieve an ionization rate of ≥10 8 /s. In such cases, the best time resolution would be achieved by collecting ionized electrons rather than the positive ions.

Fast neutron sensitivity of neutron detectors based on Boron-10 converter layers

NASA Astrophysics Data System (ADS)

Mauri, G.; Messi, F.; Kanaki, K.; Hall-Wilton, R.; Karnickis, E.; Khaplanov, A.; Piscitelli, F.

2018-03-01

In the last few years many detector technologies for thermal neutron detection have been developed in order to face the shortage of 3He, which is now much less available and more expensive. Moreover the 3He-based detectors can not fulfil the requirements in performance, e.g. the spatial resolution and the counting rate capability needed for the new instruments. The Boron-10-based gaseous detectors have been proposed as a suitable choice. This and other alternative technologies are being developed at ESS. Higher intensities mean higher signals but higher background as well. The signal-to-background ratio is an important feature to study, in particular the γ-ray and the fast neutron contributions. This paper investigates, for the first time, the fast neutrons sensitivity of 10B-based thermal neutron detector. It presents the study of the detector response as a function of energy threshold and the underlying physical mechanisms. The latter are explained with the help of theoretical considerations and simulations.

X-ray characterization of a multichannel smart-pixel array detector.

PubMed

Ross, Steve; Haji-Sheikh, Michael; Huntington, Andrew; Kline, David; Lee, Adam; Li, Yuelin; Rhee, Jehyuk; Tarpley, Mary; Walko, Donald A; Westberg, Gregg; Williams, George; Zou, Haifeng; Landahl, Eric

2016-01-01

The Voxtel VX-798 is a prototype X-ray pixel array detector (PAD) featuring a silicon sensor photodiode array of 48 × 48 pixels, each 130 µm × 130 µm × 520 µm thick, coupled to a CMOS readout application specific integrated circuit (ASIC). The first synchrotron X-ray characterization of this detector is presented, and its ability to selectively count individual X-rays within two independent arrival time windows, a programmable energy range, and localized to a single pixel is demonstrated. During our first trial run at Argonne National Laboratory's Advance Photon Source, the detector achieved a 60 ns gating time and 700 eV full width at half-maximum energy resolution in agreement with design parameters. Each pixel of the PAD holds two independent digital counters, and the discriminator for X-ray energy features both an upper and lower threshold to window the energy of interest discarding unwanted background. This smart-pixel technology allows energy and time resolution to be set and optimized in software. It is found that the detector linearity follows an isolated dead-time model, implying that megahertz count rates should be possible in each pixel. Measurement of the line and point spread functions showed negligible spatial blurring. When combined with the timing structure of the synchrotron storage ring, it is demonstrated that the area detector can perform both picosecond time-resolved X-ray diffraction and fluorescence spectroscopy measurements.

Detector Development for the abBA Experiment.

PubMed

Seo, P-N; Bowman, J D; Mitchell, G S; Penttila, S I; Wilburn, W S

2005-01-01

We have developed a new type of field-expansion spectrometer to measure the neutron beta decay correlations (a, b, B, and A). A precision measurement of these correlations places stringent requirements on charged particle detectors. The design employs large area segmented silicon detectors to detect both protons and electrons in coincidence. Other requirements include good energy resolution (< 5 keV), a thin dead layer to allow observation of 30-keV protons, fast timing resolution (~1 ns) to reconstruct electron-backscattering events, and nearly unity efficiency. We report results of testing commercially available surface-barrier silicon detectors for energy resolution and timing performance, and measurement of the dead-layer thickness of ion-implanted silicon detectors with a 3.2 MeV alpha source.

Initial tests of a prototype MRI-compatible PET imager

NASA Astrophysics Data System (ADS)

Raylman, Raymond R.; Majewski, Stan; Lemieux, Susan; Velan, S. Sendhil; Kross, Brain; Popov, Vladimir; Smith, Mark F.; Weisenberger, Andrew G.; Wojcik, Randy

2006-12-01

Multi-modality imaging is rapidly becoming a valuable tool in the diagnosis of disease and in the development of new drugs. Functional images produced with PET fused with anatomical structure images created by MRI, will allow the correlation of form with function. Our group (a collaboration of West Virginia University and Jefferson Lab) is developing a system to acquire MRI and PET images contemporaneously. The prototype device consists of two opposed detector heads, operating in coincidence mode with an active FOV of 5×5×4 cm 3. Each MRI-PET detector module consists of an array of LSO detector elements (2.5×2.5×15 mm 3) coupled through a long fiber optic light guide to a single Hamamatsu flat panel PSPMT. The fiber optic light guide is made of a glued assembly of 2 mm diameter acrylic fibers with a total length of 2.5 m. The use of a light guides allows the PSPMTs to be positioned outside the bore of the 3 T General Electric MRI scanner used in the tests. Photon attenuation in the light guides resulted in an energy resolution of ˜60% FWHM, interaction of the magnetic field with PSPMT further reduced energy resolution to ˜85% FWHM. Despite this effect, excellent multi-plane PET and MRI images of a simple disk phantom were acquired simultaneously. Future work includes improved light guides, optimized magnetic shielding for the PSPMTs, construction of specialized coils to permit high-resolution MRI imaging, and use of the system to perform simultaneous PET and MRI or MR-spectroscopy .

High-resolution CdTe detectors with application to various fields (Conference Presentation)

NASA Astrophysics Data System (ADS)

Takeda, Shin'ichiro; Orita, Tadashi; Arai, Yasuo; Sugawara, Hirotaka; Tomaru, Ryota; Katsuragawa, Miho; Sato, Goro; Watanabe, Shin; Ikeda, Hirokazu; Takahashi, Tadayuki; Furenlid, Lars R.; Barber, H. Bradford

2016-10-01

High-quality CdTe semiconductor detectors with both fine position resolution and high energy resolution hold great promise to improve measurement in various hard X-ray and gamma-ray imaging fields. ISAS/JAXA has been developing CdTe imaging detectors to meet scientific demands in latest celestial observation and severe environmental limitation (power consumption, vibration, radiation) in space for over 15 years. The energy resolution of imaging detectors with a CdTe Schottky diode of In/CdTe/Pt or Al/CdTe/Pt contact is a highlight of our development. We can extremely reduce a leakage current of devises, meaning it allows us to supply higher bias voltage to collect charges. The 3.2cm-wide and 0.75mm-thick CdTe double-sided strip detector with a strip pitch of 250 µm has been successfully established and was mounted in the latest Japanese X-ray satellite. The energy resolution measured in the test on ground was 2.1 keV (FWHM) at 59.5 keV. The detector with much finer resolution of 60 µm is ready, and it was actually used in the FOXSI rocket mission to observe hard X-ray from the sun. In this talk, we will focus on our research activities to apply space sensor technologies to such various imaging fields as medical imaging. Recent development of CdTe detectors, imaging module with pinhole and coded-mask collimators, and experimental study of response to hard X-rays and gamma-rays are presented. The talk also includes research of the Compton camera which has a configuration of accumulated Si and CdTe imaging detectors.

A High-Resolution Time-of-Flight Clinical PET Detection System Using a Gapless PMT-Quadrant-Sharing Method

NASA Astrophysics Data System (ADS)

Wong, Wai-Hoi; Li, Hongdi; Zhang, Yuxuan; Ramirez, Rocio; An, Shaohui; Wang, Chao; Liu, Shitao; Dong, Yun; Baghaei, Hossain

2015-10-01

We developed a high-resolution Photomultiplier-Quadrant-Sharing (PQS) PET system for human imaging. This system is made up of 24 detector panels. Each panel (bank) consists of 3 ×7 detector blocks, and each block has 16 ×16 LYSO crystals of 2.35 ×2.35 ×15.2 mm3. We used a novel detector-grinding scheme that is compatible with the PQS detector-pixel-decoding requirements to make a gapless cylindrical detector ring for maximizing detection efficiency while delivering an ultrahigh spatial-resolution for a whole-body PET camera with a ring diameter of 87 cm and axial field of view of 27.6 cm. This grinding scheme enables two adjacent gapless panels to share one row of the PMTs to extend the PQS configuration beyond one panel and thus maximize the economic benefit (in PMT usage) of the PQS design. The entire detector ring has 129,024 crystals, all of which are clearly decoded using only 576 PMTs (38-mm diameter). Thus, each PMT on average decodes 224 crystals to achieve a high crystal-pitch resolution of 2.44 mm ×2.44 mm. The detector blocks were mass-produced with our slab-sandwich-slice technique using a set of optimized mirror-film patterns (between crystals) to maximize light output and achieve high spatial and timing resolution. This detection system with time-of-flight capability was placed in a human PET/CT gantry. The reconstructed image resolution of the system was about 2.87 mm using 2D-filtered back-projection. The time-of-flight resolution was 473 ps. The preliminary images of phantoms and clinical studies presented in this work demonstrate the capability of this new PET/CT system to produce high-quality images.

High-Resolution Detector For X-Ray Diffraction

NASA Technical Reports Server (NTRS)

Carter, Daniel C.; Withrow, William K.; Pusey, Marc L.; Yost, Vaughn H.

1988-01-01

Proposed x-ray-sensitive imaging detector offers superior spatial resolution, counting-rate capacity, and dynamic range. Instrument based on laser-stimulated luminescence and reusable x-ray-sensitive film. Detector scans x-ray film line by line. Extracts latent image in film and simultaneously erases film for reuse. Used primarily for protein crystallography. Principle adapted to imaging detectors for electron microscopy and fluorescence spectroscopy and general use in astronomy, engineering, and medicine.

High resolution multiple excitation spot optical microscopy

NASA Astrophysics Data System (ADS)

Dilipkumar, Shilpa; Mondal, Partha Pratim

2011-06-01

We propose fundamental improvements in three-dimensional (3D) resolution of multiple excitation spot optical microscopy. The excitation point spread function (PSF) is generated by two interfering counter-propagating depth-of-focus beams along the optical axis. Detection PSF is obtained by coherently interfering the emitted fluorescent light (collected by both the objectives) at the detector. System PSF shows upto 14-fold reduction in focal volume as compared to confocal, and almost 2-fold improvement in lateral resolution. Proposed PSF has the ability to simultaneously excite multiple 3D-spots of sub-femtoliter volume. Potential applications are in fluorescence microscopy and nanobioimaging.

Characterization of Makrofol ® DE 1-1 for alpha particle radiography

NASA Astrophysics Data System (ADS)

El Ghazaly, M.; Aydarous, Abdulkadir; Al-Thomali, Talal A.

2017-09-01

Makrofol ® DE 1-1 (bisphenol-A polycarbonate) was investigated for alpha particle radiography. The edge spread function (ESF) was measured by razor-blade's edge. Makrofol ® DE 1-1 detectors were irradiated with perpendicular incident alpha particles of energy 2.5, 4 and 5.4 MeV, thereafter they were etched in 75% 6N KOH+25% C2H5OH at a temperature of 50 °C for different durations. The etched Makrofol®DE 1-1 detectors were imaged with an optical microscope equipped with a CCD camera. The results revealed that the green channel of the original RGB image provides the highest contrast comparing with red and blue channel by a factor of 27.6% of the original RGB image. The image contrast of alpha particle-irradiated Makrofol®DE 1-1 detector was found to be inversely related to the etching time since the alpha particle tracks proceed from a conical phase to spherical phase. The spatial resolution of alpha particle-irradiated Makrofol®DE 1-1 detector, in terms of line spread function, was found to deteriorate as the etching time increases for all examined alpha particle energies. The results revealed the potential capability of Makrofol®DE 1-1 detector as an efficient detector for alpha particle radiography such as autoradiography.

A comparative study via Monte Carlo simulation of new inorganic scintillator Cs2HfCl6 for applications in nuclear medicine, security and defense, and astrophysics

NASA Astrophysics Data System (ADS)

Chen, Henry; Raby, Paul

2016-09-01

Cs2HfCl6 (CHC) is one of the most promising recently discovered new inorganic single crystal scintillator that has high light output, non-hygroscopic, no self-activity, having energy resolution significantly better than NaI(Tl), even approaching that of LaBr3 yet can also potentially be at a much lower cost than LaBr3. This study attempts to use Monte Carlo simulation to examine the great potential offered by this new scintillator. CHC's detector performance is compared via simulation with that of 4 typical existing scintillators of the same size and same PMT readout. Two halide-scintillators: NaI(Tl) and LaBr3 and two oxide-scintillators: GSO and LSO were used in this simulation to compare their 122 keV and 511 keV gamma responses with that of CHC with both spectroscopy application and imaging applications in mind. Initial simulation results are very promising and consistent with reported experimental measurements. Beside detector energy resolution, image-quality measurement parameters commonly used to characterize imaging detectors as in nuclear medicine such as Light Response Function (LRF) which goes in parallel with spatial resolution and simulated position spectra will also be presented and discussed.

Online readout and control unit for high-speed/high resolution readout of silicon tracking detectors

NASA Astrophysics Data System (ADS)

Bürger, J.; Hansen, K.; Lange, W.; Nowak, T.; Prell, S.; Zimmermann, W.

1997-02-01

We are describing a high speed VME readout and control module developed and presently working at the H1 experiment at DESY in Hamburg. It has the capability to read out 4 × 2048 analogue data channels at sampling rates up to 10 MHz with a dynamic input range of 1 V. The nominal resolution of the A/D converters can be adjusted between 8 and 12 bit. At the latter resolution we obtain signal-to-noise ratio better than 61.4 dB at a conversion rate of 5 MSps. At this data rate all 8192 detector channels can be read out to the internal raw data memory and VME interface within about 410 μs and 510 μs, respectively. The pedestal subtracted signals can be analyzed on-line. At a raw data hit occupation of 10%, the VME readout time is 50 μs per module. Each module provides four complementary CMOS signals to control the front-end electronics and four independent sets of power supplies for analogue and digital voltages (10 V, 100 mA) to drive the front-end electronics and for the bias voltage (100 V, 1.2 mA) to assure the full functionality of the detectors and the readout.

Design and image-quality performance of high resolution CMOS-based X-ray imaging detectors for digital mammography

NASA Astrophysics Data System (ADS)

Cha, B. K.; Kim, J. Y.; Kim, Y. J.; Yun, S.; Cho, G.; Kim, H. K.; Seo, C.-W.; Jeon, S.; Huh, Y.

2012-04-01

In digital X-ray imaging systems, X-ray imaging detectors based on scintillating screens with electronic devices such as charge-coupled devices (CCDs), thin-film transistors (TFT), complementary metal oxide semiconductor (CMOS) flat panel imagers have been introduced for general radiography, dental, mammography and non-destructive testing (NDT) applications. Recently, a large-area CMOS active-pixel sensor (APS) in combination with scintillation films has been widely used in a variety of digital X-ray imaging applications. We employed a scintillator-based CMOS APS image sensor for high-resolution mammography. In this work, both powder-type Gd2O2S:Tb and a columnar structured CsI:Tl scintillation screens with various thicknesses were fabricated and used as materials to convert X-ray into visible light. These scintillating screens were directly coupled to a CMOS flat panel imager with a 25 × 50 mm2 active area and a 48 μm pixel pitch for high spatial resolution acquisition. We used a W/Al mammographic X-ray source with a 30 kVp energy condition. The imaging characterization of the X-ray detector was measured and analyzed in terms of linearity in incident X-ray dose, modulation transfer function (MTF), noise-power spectrum (NPS) and detective quantum efficiency (DQE).

Development and characterization of high-resolution neutron pixel detectors based on Timepix read-out chips

NASA Astrophysics Data System (ADS)

Krejci, F.; Zemlicka, J.; Jakubek, J.; Dudak, J.; Vavrik, D.; Köster, U.; Atkins, D.; Kaestner, A.; Soltes, J.; Viererbl, L.; Vacik, J.; Tomandl, I.

2016-12-01

Using a suitable isotope such as 6Li and 10B semiconductor hybrid pixel detectors can be successfully adapted for position sensitive detection of thermal and cold neutrons via conversion into energetic light ions. The adapted devices then typically provides spatial resolution at the level comparable to the pixel pitch (55 μm) and sensitive area of about few cm2. In this contribution, we describe further progress in neutron imaging performance based on the development of a large-area hybrid pixel detector providing practically continuous neutron sensitive area of 71 × 57 mm2. The measurements characterising the detector performance at the cold neutron imaging instrument ICON at PSI and high-flux imaging beam-line Neutrograph at ILL are presented. At both facilities, high-resolution high-contrast neutron radiography with the newly developed detector has been successfully applied for objects which imaging were previously difficult with hybrid pixel technology (such as various composite materials, objects of cultural heritage etc.). Further, a significant improvement in the spatial resolution of neutron radiography with hybrid semiconductor pixel detector based on the fast read-out Timepix-based detector is presented. The system is equipped with a thin planar 6LiF convertor operated effectively in the event-by-event mode enabling position sensitive detection with spatial resolution better than 10 μm.

Functional near-infrared spectroscopy at small source-detector distance by means of high dynamic-range fast-gated SPAD acquisitions: first in-vivo measurements

NASA Astrophysics Data System (ADS)

Di Sieno, L.; Contini, D.; Dalla Mora, A.; Torricelli, A.; Spinelli, L.; Cubeddu, R.; Tosi, A.; Boso, G.; Pifferi, A.

2013-06-01

In this article, we show experimental results of time-resolved optical spectroscopy performed with small distance between launching and detecting fibers. It was already demonstrated that depth discrimination is independent of source-detector separation and that measurements at small source detector distance provide better contrast and spatial resolution. The main disadvantage is represent by the huge increase in early photons (scarcely diffused by tissue) peak that can saturate the dynamic range of most detectors, hiding information carried by late photons. Thanks to a fast-gated Single- Photon Avalanche Diode (SPAD) module, we are able to reject the peak of early photons and to obtain high-dynamic range acquisitions. We exploit fast-gated SPAD module to perform for the first time functional near-infrared spectroscopy (fNIRS) at small source-detector distance for in vivo measurements and we demonstrate the possibility to detect non-invasively the dynamics of oxygenated and deoxygenated haemoglobin occurring in the motor cortex during a motor task. We also show the improvement in terms of signal amplitude and Signal-to-Noise Ratio (SNR) obtained exploiting fast-gated SPAD performances with respect to "non-gated" measurements.

The Influence of Gantry Geometry on Aliasing and Other Geometry Dependent Errors

NASA Astrophysics Data System (ADS)

Joseph, Peter M.

1980-06-01

At least three gantry geometries are widely used in medical CT scanners: (1) rotate-translate, (2) rotating detectors, (3) stationary detectors. There are significant geometrical differences between these designs, especially regarding (a) the region of space scanned by any given detector and (b) the sample density of rays which scan the patient. It is imperative to distinguish between "views" and "rays" in analyzing this situation. In particular, views are defined by the x-ray source in type 2 and by the detector in type 3 gantries. It is known that ray dependent errors are generally much more important than view dependent errors. It is shown that spatial resolution is primarily limited by the spacing between rays in any view, while the number of ray samples per beam width determines the extent of aliasing artifacts. Rotating detector gantries are especially susceptible to aliasing effects. It is shown that aliasing effects can distort the point spread function in a way that is highly dependent on the position of the point in the scanned field. Such effects can cause anomalies in the MTF functions as derived from points in machines with significant aliasing problems.

Image quality of a pixellated GaAs X-ray detector

NASA Astrophysics Data System (ADS)

Sun, G. C.; Makham, S.; Bourgoin, J. C.; Mauger, A.

2007-02-01

X-ray detection requires materials with large atomic numbers Z in order to absorb the radiation efficiently. In case of X-ray imaging, fluorescence is a limiting factor for the spatial resolution and contrast at energies above the kα threshold. Since both the energy and yield of the fluorescence of a given material increase with the atomic number, there is an optimum value of Z. GaAs, which can now be epitaxially grown as self-supported thick layers to fulfil the requirements for imaging (good homogeneity of the electronic properties) corresponds to this optimum. Image performances obtained with this material are evaluated in terms of line spread function and modulation transfer function, and a comparison with CsI is made. We evaluate the image contrast obtained for a given object contrast with GaAs and CsI detectors, in the photon energy range of medical applications. Finally, we discuss the minimum object size, which can be detected by these detectors in of mammography conditions. This demonstrates that an object of a given size can be detected using a GaAs detector with a dose at least 100 times lower than using a CsI detector.

Seeing tobacco mosaic virus through direct electron detectors

PubMed Central

Fromm, Simon A.; Bharat, Tanmay A.M.; Jakobi, Arjen J.; Hagen, Wim J.H.; Sachse, Carsten

2015-01-01

With the introduction of direct electron detectors (DED) to the field of electron cryo-microscopy, a wave of atomic-resolution structures has become available. As the new detectors still require comparative characterization, we have used tobacco mosaic virus (TMV) as a test specimen to study the quality of 3D image reconstructions from data recorded on the two direct electron detector cameras, K2 Summit and Falcon II. Using DED movie frames, we explored related image-processing aspects and compared the performance of micrograph-based and segment-based motion correction approaches. In addition, we investigated the effect of dose deposition on the atomic-resolution structure of TMV and show that radiation damage affects negative carboxyl chains first in a side-chain specific manner. Finally, using 450,000 asymmetric units and limiting the effects of radiation damage, we determined a high-resolution cryo-EM map at 3.35 Å resolution. Here, we provide a comparative case study of highly ordered TMV recorded on different direct electron detectors to establish recording and processing conditions that enable structure determination up to 3.2 Å in resolution using cryo-EM. PMID:25528571

Enhancement of the resolution of full-field optical coherence tomography by using a colour image sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalyanov, A L; Lychagov, V V; Smirnov, I V

2013-08-31

The influence of white balance in a colour image detector on the resolution of a full-field optical coherence tomograph (FFOCT) is studied. The change in the interference pulse width depending on the white balance tuning is estimated in the cases of a thermal radiation source (incandescent lamp) and a white light emitting diode. It is shown that by tuning white balance of the detector in a certain range, the FFOCT resolution can be increased by 20 % as compared to the resolution, attained with the use of a monochrome detector. (optical coherence tomography)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ross, Steve; Haji-Sheikh, Michael; Huntington, Andrew

The Voxtel VX-798 is a prototype X-ray pixel array detector (PAD) featuring a silicon sensor photodiode array of 48 x 48 pixels, each 130 mu m x 130 mu m x 520 mu m thick, coupled to a CMOS readout application specific integrated circuit (ASIC). The first synchrotron X-ray characterization of this detector is presented, and its ability to selectively count individual X-rays within two independent arrival time windows, a programmable energy range, and localized to a single pixel is demonstrated. During our first trial run at Argonne National Laboratory's Advance Photon Source, the detector achieved a 60 ns gatingmore » time and 700 eV full width at half-maximum energy resolution in agreement with design parameters. Each pixel of the PAD holds two independent digital counters, and the discriminator for X-ray energy features both an upper and lower threshold to window the energy of interest discarding unwanted background. This smart-pixel technology allows energy and time resolution to be set and optimized in software. It is found that the detector linearity follows an isolated dead-time model, implying that megahertz count rates should be possible in each pixel. Measurement of the line and point spread functions showed negligible spatial blurring. When combined with the timing structure of the synchrotron storage ring, it is demonstrated that the area detector can perform both picosecond time-resolved X-ray diffraction and fluorescence spectroscopy measurements.« less

Ultrahigh-resolution CT and DR scanner

NASA Astrophysics Data System (ADS)

DiBianca, Frank A.; Gupta, Vivek; Zou, Ping; Jordan, Lawrence M.; Laughter, Joseph S.; Zeman, Herbert D.; Sebes, Jeno I.

1999-05-01

A new technique called Variable-Resolution X-ray (VRX) detection that dramatically increases the spatial resolution in computed tomography (CT) and digital radiography (DR) is presented. The technique is based on a principle called 'projective compression' that allows the resolution element of a CT detector to scale with the subject or field size. For very large (40 - 50 cm) field sizes, resolution exceeding 2 cy/mm is possible and for very small fields, microscopy is attainable with resolution exceeding 100 cy/mm. Several effects that could limit the performance of VRX detectors are considered. Experimental measurements on a 16-channel, CdWO4 scintillator + photodiode test array yield a limiting MTF of 64 cy/mm (8(mu) ) in the highest-resolution configuration reported. Preliminary CT images have been made of small anatomical specimens and small animals using a storage phosphor screen in the VRX mode. Measured detector resolution of the CT projection data exceeds 20 cy/mm (less than 25 (mu) ); however, the final, reconstructed CT images produced thus far exhibit 10 cy/mm (50 (mu) ) resolution because of non-flatness of the storage phosphor plates, focal spot effects and the use of a rudimentary CT reconstruction algorithm. A 576-channel solid-state detector is being fabricated that is expected to achieve CT image resolution in excess of that of the 26-channel test array.

A Segmented Neutron Detector with a High Position Resolution for the (p,pn) Reactions

NASA Astrophysics Data System (ADS)

Kubota, Yuki; Sasano, Masaki; Uesaka, Tomohiro; Dozono, Masanori; Itoh, Masatoshi; Kawase, Shoichiro; Kobayashi, Motoki; Lee, CheongSoo; Matsubara, Hiroaki; Miki, Kenjiro; Miya, Hiroyuki; Ota, Shinsuke; Sekiguchi, Kimiko; Shima, Tatsushi; Taguchi, Takahiro; Tamii, Atsushi; Tang, Tsz Leung; Tokieda, Hiroshi; Wakasa, Tomotsugu; Wakui, Takashi; Yasuda, Jumpei; Zenihiro, Juzo

We are developing a neutron detector with a high position resolution to study the single particle properties of nuclei by the knockout (p,pn) reaction at intermediate energies. We constructed a prototype detector consisting of plastic scintillating fibers and multi-anode photomultiplier tubes (PMTs). Test experiments using 200- and 70-MeV proton and 199-, 188-, 68-, and 50-MeV neutron were performed for characterizing its performance. Preliminary results show that a position resolution of about 3 mm at full-width at half-maximum (FWHM) is realized as designed. The resulting separation-energy resolution to be obtained for (p,pn) measurement would be 1 MeV in FWHM, when the detector is used at a distance of 2 m from the target for measuring the neutron momentum.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plautz, Tia E.; Johnson, R. P.; Sadrozinski, H. F.-W.

Purpose: To characterize the modulation transfer function (MTF) of the pre-clinical (phase II) head scanner developed for proton computed tomography (pCT) by the pCT collaboration. To evaluate the spatial resolution achievable by this system. Methods: Our phase II proton CT scanner prototype consists of two silicon telescopes that track individual protons upstream and downstream from a phantom, and a 5-stage scintillation detector that measures a combination of the residual energy and range of the proton. Residual energy is converted to water equivalent path length (WEPL) of the protons in the scanned object. The set of WEPL values and associated pathsmore » of protons passing through the object over a 360° angular scan is processed by an iterative parallelizable reconstruction algorithm that runs on GP-GPU hardware. A custom edge phantom composed of water-equivalent polymer and tissue-equivalent material inserts was constructed. The phantom was first simulated in Geant4 and then built to perform experimental beam tests with 200 MeV protons at the Northwestern Medicine Chicago Proton Center. The oversampling method was used to construct radial and azimuthal edge spread functions and modulation transfer functions. The spatial resolution was defined by the 10% point of the modulation transfer function in units of lp/cm. Results: The spatial resolution of the image was found to be strongly correlated with the radial position of the insert but independent of the relative stopping power of the insert. The spatial resolution varies between roughly 4 and 6 lp/cm in both the the radial and azimuthal directions depending on the radial displacement of the edge. Conclusion: The amount of image degradation due to our detector system is small compared with the effects of multiple Coulomb scattering, pixelation of the image and the reconstruction algorithm. Improvements in reconstruction will be made in order to achieve the theoretical limits of spatial resolution.« less

Measurements with Si and GaAs pixel detectors bonded to photon counting readout chips

NASA Astrophysics Data System (ADS)

Schwarz, C.; Campbell, M.; Goeppert, R.; Ludwig, J.; Mikulec, B.; Runge, K.; Smith, K. M.; Snoeys, W.

2001-06-01

Detectors fabricated with SI-GaAs and Si bulk material were bonded to Photon Counting Chips (PCC), developed in the framework of the MEDIPIX Collaboration. The PCC consists of a matrix of 64×64 identical square pixels (170 μm×170 μm) with a 15-bit counter in each cell. We investigated the imaging properties of these detector systems under exposure of a dental X-ray tube at room temperature. The image homogeneity and the mean count rate were determined via flood exposure images and compared. Exposures for GaAs detectors exhibit a 3 times larger spread in count rate per image in comparison to Si detectors. This also results in a 3 times worse signal to noise ratio. IV-characteristics and X-ray images at different values of the detectors bias voltage were also taken and show a 30 times higher leakage current for GaAs. The Si detector is fully active beginning from 70 V, whereas the GaAs detector does not reach full charge collection. The presampling modulation transfer function of both assembly types was measured via slit images and gives a spatial resolution of 4.3 lp/mm for both detector systems.

Towards simultaneous single emission microscopy and magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Cai, Liang

In recent years, the combined nuclear imaging and magnetic resonance imaging (MRI) has drawn extensive research effort. They can provide simultaneously acquired anatomical and functional information inside the human/small animal body in vivo. In this dissertation, the development of an ultrahigh resolution MR-compatible SPECT (Single Photon Emission Computed Tomography) system that can be operated inside a pre-existing clinical MR scanner for simultaneous dual-modality imaging of small animals will be discussed. This system is constructed with 40 small pixel CdTe detector modules assembled in a fully stationary ring SPECT geometry. Series of experiments have demonstrated that this system is capable of providing an imaging resolution of <500?m, when operated inside MR scanners. The ultrahigh resolution MR-compatible SPECT system is built around a small pixel CdTe detector module that we recently developed. Each module consists of CdTe detectors having an overall size of 2.2 cm x 1.1 cm, divided into 64 x 32 pixels of 350 mum in size. A novel hybrid pixel-waveform (HPWF) readout system is also designed to alleviate several challenges for using small-pixel CdTe detectors in ultrahigh-resolution SPECT imaging applications. The HPWF system utilizes a modified version of a 2048-channel 2-D CMOS ASIC to readout the anode pixel, and a digitizing circuitry to sample the signal waveform induced on the cathode. The cathode waveform acquired with the HPWF circuitry offers excellent spatial resolution, energy resolution and depth of interaction (DOI) information, even with the presence of excessive charge-sharing/charge-loss between the small anode pixels. The HPWF CdTe detector is designed and constructed with a minimum amount of ferromagnetic materials, to ensure the MR-compatibility. To achieve sub-500?m imaging resolution, two special designed SPECT apertures have been constructed with different pinhole sizes of 300?m and 500?m respectively. It has 40 pinhole inserts that are made of cast platinum (90%)-iridium (10%) alloy, which provides the maximum stopping power and are compatible with MR scanners. The SPECT system is installed on a non-metal gantry constructed with 3-D printing using nylon powder material. This compact system can work as a "low-cost" desktop ultrahigh resolution SPECT system. It can also be directly operated inside an MR scanner. Accurate system geometrical calibration and corresponding image reconstruction methods for the MRC-SPECT system is developed. In order to account for the magnetic field induced distortion in the SPECT image, a comprehensive charge collection model inside strong magnetic field is adopted to produce high resolution SPECT image inside MR scanner.

Raster-scan optoacoustic angiography reveals 3D microcirculatory changes during cuffed occlusion

NASA Astrophysics Data System (ADS)

Subochev, Pavel; Orlova, Anna; Smolina, Ekaterina; Kirillov, Aleksey; Shakhova, Natalia; Turchin, Ilya

2018-04-01

Acoustic resolution photoacoustic microscopy at the optical wavelength of 532 nm was used to investigate the functional reaction of blood vessels of healthy human skin during cuffed venous occlusion. The high bandwidth of the polyvinilidene difluoride detector provided the opportunity for raster-scan optoacoustic angiography of both the superficial and deep plexuses at the high resolution of 35/50 microns (axial/lateral). A reversible increase of blood supply in the microcirculatory bed during occlusion was revealed.

Study of the Dependency on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter.

PubMed

Gottardi, L; Adams, J; Bailey, C; Bandler, S; Bruijn, M; Chervenak, J; Eckart, M; Finkbeiner, F; den Hartog, R; Hoevers, H; Kelley, R; Kilbourne, C; de Korte, P; van der Kuur, J; Lindeman, M; Porter, F; Sadlier, J; Smith, S

At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in an AC bias configuration. For x-ray photons at 6 keV the pixel shows an x-ray energy resolution Δ E FWHM =3.7 eV, which is about a factor 2 worse than the energy resolution observed in an identical DC-biased pixel. In order to better understand the reasons for this discrepancy we characterised the detector as a function of temperature, bias working point and applied perpendicular magnetic field. A strong periodic dependency of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recently observed weak-link behaviour of a TES microcalorimeter.

Characterization of X3 Silicon Detectors for the ELISSA Array at ELI-NP

NASA Astrophysics Data System (ADS)

Chesnevskaya, S.; Balabanski, D. L.; Choudhury, D.; Cognata, M. La; Constantin, P.; Filipescu, D. M.; Ghita, D. G.; Guardo, G. L.; Lattuada, D.; Matei, C.; Rotaru, A.; Spitaleri, C.; State, A.; Xu, Y.

2018-01-01

Position-sensitive silicon strip detectors represent one of the best solutions for the detection of charged particles as they provide good energy and position resolution over a large range of energies. A silicon array coupled with the gamma beams at the ELI-NP facility would allow measuring photodissociation reactions of interest for Big Bang Nucleosynthesis and on heavy nuclei intervening in the p-process. Forty X3 detectors for our ELISSA (ELI-NP Silicon Strip Detectors Array) project have been recently purchased and tested. We investigated several specifications, such as leakage currents, depletion voltage, and detector stability under vacuum. The energy and position resolution, and ballistic deficit were measured and analyzed. This paper presents the main results of our extensive testing. The measured energy resolution for the X3 detectors is better than results published for similar arrays (ANASEN or ORRUBA).

High Resolution Energetic X-ray Imager (HREXI)

NASA Astrophysics Data System (ADS)

Grindlay, Jonathan

We propose to design and build the first imaging hard X-ray detector system that incorporates 3D stacking of closely packed detector readouts in finely-spaced imaging arrays with their required data processing and control electronics. In virtually all imaging astronomical detectors, detector readout is done with flex connectors or connections that are not vertical but rather horizontal , requiring loss of focal plane area. For high resolution pixel detectors needed for high speed event-based X-ray imaging, from low energy applications (CMOS) with focusing X-ray telescopes, to hard X-ray applications with pixelated CZT for large area coded aperture telescopes, this new detector development offers great promise. We propose to extend our previous and current APRA supported ProtoEXIST program that has developed the first large area imaging CZT detectors and demonstrated their astrophysical capabilities on two successful balloon flight to a next generation High Resolution Energetic X-ray Imager (HREXI), which would incorporate microvia technology for the first time to connect the readout ASIC on each CZT crystal directly to its control and data processing system. This 3-dimensional stacking of detector and readout/control system means that large area (>2m2) imaging detector planes for a High Resolution Wide-field hard X-ray telescope can be built with initially greatly reduced detector gaps and ultimately with no gaps. This increases detector area, efficiency, and simplicity of detector integration. Thus higher sensitivity wide-field imagers will be possible at lower cost. HREXI will enable a post-Swift NASA mission such as the EREXS concept proposed to PCOS to be conducted as a future MIDEX mission. This mission would conduct a high resolution (<2 arcmin) , broad band (5 200 keV) hard X-ray survey of black holes on all scales with ~10X higher sensitivity than Swift. In the current era of Time Domain Astrophysics, such a survey capability, in conjunction with a nIR telescope in spece, will enable GRBs to be used as probes of the formation of the first stars and structure in the Universe. HREXI on its own, with broad bandwidth and high spectral and spatial resolution, will extend both Galactic surveys for obscured young supernova remnants (44Ti sources) and for transients, black holes and flaring AGN and TDEs well at greatly increased sensitivity and spatial/spectral resolution than has been done with Swift or INTEGRAL. If the HREXI-1 technology is developed in the first year of this proposed effort, it could be used on the upcoming Brazil-US MIRAX telescope on the Lattes satellite, scheduled for a 2018 launch with imaging detector planes to be provided (under contract) by our group. Finally, the 3D stacking technology development proposed here for imaging detector arrays has broad application to Wide Field soft X-ray imaging, to CMB polarization mode (B mode) imaging detectors with very high detector-pixel count, and to Homeland Security.

Energy resolution and efficiency of phonon-mediated kinetic inductance detectors for light detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cardani, L., E-mail: laura.cardani@roma1.infn.it; Physics Department, Princeton University, Washington Road, 08544, Princeton, New Jersey; Colantoni, I.

The development of sensitive cryogenic light detectors is of primary interest for bolometric experiments searching for rare events like dark matter interactions or neutrino-less double beta decay. Thanks to their good energy resolution and the natural multiplexed read-out, Kinetic Inductance Detectors (KIDs) are particularly suitable for this purpose. To efficiently couple KIDs-based light detectors to the large crystals used by the most advanced bolometric detectors, active surfaces of several cm{sup 2} are needed. For this reason, we are developing phonon-mediated detectors. In this paper, we present the results obtained with a prototype consisting of four 40 nm thick aluminum resonators patternedmore » on a 2 × 2 cm{sup 2} silicon chip, and calibrated with optical pulses and X-rays. The detector features a noise resolution σ{sub E} = 154 ± 7 eV and an (18 ± 2)% efficiency.« less

Large gamma-ray detector arrays and electromagnetic separators

NASA Astrophysics Data System (ADS)

Lee, I.-Yang

2013-12-01

The use of large gamma-ray detector arrays with electromagnetic separators is a powerful combination. Various types of gamma-ray detectors have been used; some provide high detector efficiency such as scintillation detector array, others use Ge detectors for good energy resolution, and recently developed Ge energy tracking arrays gives both high peak-to-background ratio and position resolution. Similarly, different types of separators were used to optimize the performance under different experimental requirements and conditions. For example, gas-filled separators were used in heavy element studies for their large efficiency and beam rejection factor. Vacuum separators with good isotope resolution were used in transfer and fragmentation reactions for the study of nuclei far from stability. This paper presents results from recent experiments using gamma-ray detector arrays in combination with electromagnetic separators, and discusses the physics opportunities provided by these instruments. In particular, we review the performance of the instruments currently in use, and discuss the requirements of instruments for future radioactive beam accelerator facilities.

Calibration of the Large Area X-Ray Proportional Counter (LAXPC) Instrument on board AstroSat

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antia, H. M.; Yadav, J. S.; Chauhan, Jai Verdhan

We present the calibration and background model for the Large Area X-ray Proportional Counter (LAXPC) detectors on board AstroSat . The LAXPC instrument has three nominally identical detectors to achieve a large collecting area. These detectors are independent of each other, and in the event analysis mode they record the arrival time and energy of each photon that is detected. The detectors have a time resolution of 10 μ s and a dead-time of about 42 μ s. This makes LAXPC ideal for timing studies. The energy resolution and peak channel-to-energy mapping were obtained from calibration on the ground usingmore » radioactive sources coupled with GEANT4 simulations of the detectors. The response matrix was further refined from observations of the Crab after launch. At around 20 keV the energy resolution of the detectors is 10%–15%, while the combined effective area of the three detectors is about 6000 cm{sup 2}.« less

The TOFp/pVPD time-of-flight system for STAR

NASA Astrophysics Data System (ADS)

Llope, W. J.; Geurts, F.; Mitchell, J. W.; Liu, Z.; Adams, N.; Eppley, G.; Keane, D.; Li, J.; Liu, F.; Liu, L.; Mutchler, G. S.; Nussbaum, T.; Bonner, B.; Sappenfield, P.; Zhang, B.; Zhang, W.-M.

2004-04-01

A time-of-flight system was constructed for the STAR Experiment for the direct identification of hadrons produced in 197Au+ 197Au collisions at RHIC. The system consists of two separate detector subsystems, one called the Pseudo Vertex Position Detector (pVPD, the "start" detector) and the other called the Time of Flight Patch (TOFp, the "stop" detector). Each detector is based on conventional scintillator/phototube technology and includes custom high-performance front-end electronics and a common CAMAC-based digitization and read-out. The design of the system and its performance during the 2001 RHIC run will be described. The start resolution attained by the pVPD was 24 ps, implying a pVPD single-detector resolution of 58 ps. The total time resolution of the system averaged over all detector channels was 87 ps, allowing direct π/ K/ p discrimination for momenta up to ˜1.8 GeV/ c, and direct ( π+ K)/ p discrimination up to ˜3 GeV/ c.

A 3D CZT high resolution detector for x- and gamma-ray astronomy

NASA Astrophysics Data System (ADS)

Kuvvetli, I.; Budtz-Jørgensen, C.; Zappettini, A.; Zambelli, N.; Benassi, G.; Kalemci, E.; Caroli, E.; Stephen, J. B.; Auricchio, N.

2014-07-01

At DTU Space we have developed a high resolution three dimensional (3D) position sensitive CZT detector for high energy astronomy. The design of the 3D CZT detector is based on the CZT Drift Strip detector principle. The position determination perpendicular to the anode strips is performed using a novel interpolating technique based on the drift strip signals. The position determination in the detector depth direction, is made using the DOI technique based the detector cathode and anode signals. The position determination along the anode strips is made with the help of 10 cathode strips orthogonal to the anode strips. The position resolutions are at low energies dominated by the electronic noise and improve therefore with increased signal to noise ratio as the energy increases. The achievable position resolution at higher energies will however be dominated by the extended spatial distribution of the photon produced ionization charge. The main sources of noise contribution of the drift signals are the leakage current between the strips and the strip capacitance. For the leakage current, we used a metallization process that reduces the leakage current by means of a high resistive thin layer between the drift strip electrodes and CZT detector material. This method was applied to all the proto type detectors and was a very effective method to reduce the surface leakage current between the strips. The proto type detector was recently investigated at the European Synchrotron Radiation Facility, Grenoble which provided a fine 50 × 50 μm2 collimated X-ray beam covering an energy band up to 600 keV. The Beam positions are resolved very well with a ~ 0.2 mm position resolution (FWHM ) at 400 keV in all directions.

Gamma-Ray Simulated Spectrum Deconvolution of a LaBr₃ 1-in. x 1-in. Scintillator for Nondestructive ATR Fuel Burnup On-Site Predictions

DOE PAGES

Navarro, Jorge; Ring, Terry A.; Nigg, David W.

2015-03-01

A deconvolution method for a LaBr₃ 1"x1" detector for nondestructive Advanced Test Reactor (ATR) fuel burnup applications was developed. The method consisted of obtaining the detector response function, applying a deconvolution algorithm to 1”x1” LaBr₃ simulated, data along with evaluating the effects that deconvolution have on nondestructively determining ATR fuel burnup. The simulated response function of the detector was obtained using MCNPX as well with experimental data. The Maximum-Likelihood Expectation Maximization (MLEM) deconvolution algorithm was selected to enhance one-isotope source-simulated and fuel- simulated spectra. The final evaluation of the study consisted of measuring the performance of the fuel burnup calibrationmore » curve for the convoluted and deconvoluted cases. The methodology was developed in order to help design a reliable, high resolution, rugged and robust detection system for the ATR fuel canal capable of collecting high performance data for model validation, along with a system that can calculate burnup and using experimental scintillator detector data.« less

Resolution of Transverse Electron Beam Measurements using Optical Transition Radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ischebeck, Rasmus; Decker, Franz-Josef; Hogan, Mark

2005-06-22

In the plasma wakefield acceleration experiment E-167, optical transition radiation is used to measure the transverse profile of the electron bunches before and after the plasma acceleration. The distribution of the electric field from a single electron does not give a point-like distribution on the detector, but has a certain extension. Additionally, the resolution of the imaging system is affected by aberrations. The transverse profile of the bunch is thus convolved with a point spread function (PSF). Algorithms that deconvolve the image can help to improve the resolution. Imaged test patterns are used to determine the modulation transfer function ofmore » the lens. From this, the PSF can be reconstructed. The Lucy-Richardson algorithm is used to deconvolute this PSF from test images.« less

Using a flat-panel detector in high resolution cone beam CT for dental imaging.

PubMed

Baba, R; Ueda, K; Okabe, M

2004-09-01

Cone beam CT (CBCT) requires a two-dimensional X-ray detector. In the several CBCT systems developed for dental imaging, detection has been by the combination of an X-ray image intensifier and charge-coupled device (CCD) camera. In this paper, we propose a new CBCT system in which the detector is of the flat-panel type and evaluate its performance in dental imaging. We developed a prototype CBCT that has a flat-panel-type detector. The detector consists of a CsI scintillator screen and a photosensor array. First, the flat panel detector and image intensifier detector were compared in terms of the signal-to-noise ratio (SNR) of projected images. We then used these data and a theoretical formula to evaluate noise in reconstructed images. Second, reconstructed images of a bar pattern phantom were obtained as a way of evaluating the spatial resolution. Then, reconstructed images of a skull phantom were obtained. The SNR of the developed system was 1.6 times as high as that of a system with an image intensifier detector of equal detector pitch. The system was capable of resolving a 0.35 mm pattern and its field of view almost completely encompassed that of an image intensifier detector which is used in dentomaxillofacial imaging. The fine spatial resolution of the detector led to images in which the structural details of a skull phantom were clearly visible. The system's isotropically fine resolution will lead to improved precision in dental diagnosis and surgery. The next stage of our research will be the development of a flat panel detector system with a high frame acquisition rate.

Position Sensitive Proximity Charge Sensing Readout of HPGe Detectors

NASA Astrophysics Data System (ADS)

Priest, Anders Peterson

Electrode segmentation is a necessity to achieve position sensitivity in semicon- ductor radiation detectors. Traditional segmentation requires decreasing electrode sizes while increasing channel numbers to achieve very fine position resolution. These electrodes can be complicated to fabricate, and many electrodes with individual electronic channels are required to instrument large detector areas. To simplify the fabrication process, we have moved the readout electrodes onto a printed circuit board that is positioned above the ionization type detection material. In this scheme, charge from radiation interactions will be shared amongst several electrodes, allowing for position interpolation. Because events can be reconstructed in between electrodes, fewer electrodes are needed to instrument large detector areas. The proximity charge sensing method of readout promises to simplify detector fabrication while maintaining the position resolution that is required by fields such as homeland security, astrophysics, environmental remediation, nuclear physics, and medical imaging. We performed scanning measurements on a proof of principle detector that we fabricated at Lawrence Berkeley National Laboratory (LBNL). These measurements showed that position resolution much finer than the strip pitch was achievable using the proximity charge readout method. We performed analytic calculations and Monte Carlo modeling to optimize the readout electrode geometry for a larger detector to test the limits of this technology. We achieved an average position resolution of 288 microm with eight proximity electrodes at a 5 mm pitch and 1 mm strip width, set 100 microm away from the detector surface by a Kapton spacer. To achieve this resolution using standard technologies, 300 microm pitch strips are necessary, and would require 100 channels to instrument the same area. Through our optimization calculations, we found that there is a trade-off between position resolution and energy resolution, and this system provided comparatively poor energy resolution by HPGe standards, with 4.7 keV FWHM at 59.5 keV. With another electrode geometry, we were able to achieve 2.9 keV FWHM at 59.5 keV. This dissertation describes the work we completed to achieve these results.

DETECTORS AND EXPERIMENTAL METHODS: Studies of a scintillator-bar detector for a neutron wall at an external target facility

NASA Astrophysics Data System (ADS)

Yu, Yu-Hong; Xu, Hua-Gen; Xu, Hu-Shan; Zhan, Wen-Long; Sun, Zhi-Yu; Guo, Zhong-Yan; Hu, Zheng-Guo; Wang, Jian-Song; Chen, Jun-Ling; Zheng, Chuan

2009-07-01

To achieve a better time resolution of a scintillator-bar detector for a neutron wall at the external target facility of HIRFL-CSR, we have carried out a detailed study of the photomultiplier, the wrapping material and the coupling media. The timing properties of a scintillator-bar detector have been studied in detail with cosmic rays using a high and low level signal coincidence. A time resolution of 80 ps has been achieved in the center of the scintillator-bar detector.

Toroidal magnetic detector for high resolution measurement of muon momenta

DOEpatents

Bonanos, P.

1992-01-07

A muon detector system including central and end air-core superconducting toroids and muon detectors enclosing a central calorimeter/detector. Muon detectors are positioned outside of toroids and all muon trajectory measurements are made in a nonmagnetic environment. Internal support for each magnet structure is provided by sheets, located at frequent and regularly spaced azimuthal planes, which interconnect the structural walls of the toroidal magnets. In a preferred embodiment, the shape of the toroidal magnet volume is adjusted to provide constant resolution over a wide range of rapidity. 4 figs.

Toroidal magnetic detector for high resolution measurement of muon momenta

DOEpatents

Bonanos, Peter

1992-01-01

A muon detector system including central and end air-core superconducting toroids and muon detectors enclosing a central calorimeter/detector. Muon detectors are positioned outside of toroids and all muon trajectory measurements are made in a nonmagnetic environment. Internal support for each magnet structure is provided by sheets, located at frequent and regularly spaced azimuthal planes, which interconnect the structural walls of the toroidal magnets. In a preferred embodiment, the shape of the toroidal magnet volume is adjusted to provide constant resolution over a wide range of rapidity.

Limits of a spatial resolution of the cascaded GEM based detectors

NASA Astrophysics Data System (ADS)

Kudryavtsev, V. N.; Maltsev, T. V.; Shekhtman, L. I.

2017-06-01

Spatial resolution of tracking detectors based on GEM cascades is determined in the simulation and measured. The simulation includes GEANT4 implemented transport of high energy electrons with careful accounting for atomic relaxation processes including emission of fluorescent photons and Auger electrons and custom post-processing taking into account diffusion, gas amplification fluctuations, the distribution of signals over readout electrodes, electronics noise and particular algorithm of final coordinate calculation (centre-of-gravity algorithm). The simulation demonstrates that the minimum of the spatial resolution of about 10-20 μm can be achieved with a gas mixture of Ar-CO2 (75%-25%) at a strip pitch in the range from 250 μm to 300 μm. At a larger pitch the resolution quickly degrades reaching 70-100 μm at a pitch of 450-500 μm. The reasons of such behavior are discussed and corresponding hypothesis is tested. Particularly, the effect of electron cloud modification due to a GEM operation is considered using the ANSYS and Garfield++ simulation programs. The detection efficiency and spatial resolution of low-material triple-GEM detectors for the DEUTERON facility at BINP are measured at the extracted beam facility of the VEPP-4M collider. One-coordinate resolution of two detectors for the DEUTERON facility is measured with a 2 GeV electron beam. The determined values of the detectors' spatial resolution is equal to 46.6 ± 0.1 μm and 38.5 ± 0.2 μm for orthogonal tracks in two detectors, respectively.

High resolution 1280×1024, 15 μm pitch compact InSb IR detector with on-chip ADC

NASA Astrophysics Data System (ADS)

Nesher, O.; Pivnik, I.; Ilan, E.; Calalhorra, Z.; Koifman, A.; Vaserman, I.; Oiknine Schlesinger, J.; Gazit, R.; Hirsh, I.

2009-05-01

Over the last decade, SCD has developed and manufactured high quality InSb Focal Plane Arrays (FPAs), which are currently used in many applications worldwide. SCD's production line includes many different types of InSb FPA with formats of 320x256, 480x384 and 640x512 elements and with pitch sizes in the range of 15 to 30 μm. All these FPAs are available in various packaging configurations, including fully integrated Detector-Dewar-Cooler Assemblies (DDCA) with either closed-cycle Sterling or open-loop Joule-Thomson coolers. With an increasing need for higher resolution, SCD has recently developed a new large format 2-D InSb detector with 1280x1024 elements and a pixel size of 15μm. The InSb 15μm pixel technology has already been proven at SCD with the "Pelican" detector (640x512 elements), which was introduced at the Orlando conference in 2006. A new signal processor was developed at SCD for use in this mega-pixel detector. This Readout Integrated Circuit (ROIC) is designed for, and manufactured with, 0.18 μm CMOS technology. The migration from 0.5 to 0.18 μm CMOS technology supports SCD's roadmap for the reduction of pixel size and power consumption and is in line with the increasing demand for improved performance and on-chip functionality. Consequently, the new ROIC maintains the same level of performance and functionality with a 15 μm pitch, as exists in our 20 μm-pitch ROICs based on 0.5μm CMOS technology. Similar to Sebastian (SCD ROIC with A/D on chip), this signal processor also includes A/D converters on the chip and demonstrates the same level of performance, but with reduced power consumption. The pixel readout rate has been increased up to 160 MHz in order to support a high frame rate, resulting in 120 Hz operation with a window of 1024×1024 elements at ~130 mW. These A/D converters on chip save the need for using 16 A/D channels on board (in the case of an analog ROIC) which would operate at 10 MHz and consume about 8Watts A Dewar has been designed with a stiffened detector support to withstand harsh environmental conditions with a minimal contribution to the heat load of the detector. The combination of the 0.18μm-based low power CMOS technology for the ROIC and the stiffening of the detector support within the Dewar has enabled the use of the Ricor K508 cryo-cooler (0.5 W). This has created a high-resolution detector in a very compact package. In this paper we present the basic concept of the new detector. We will describe its construction and will present electrical and radiometric characterization results.

Methods for increasing the sensitivity of gamma-ray imagers

DOEpatents

Mihailescu, Lucian [Pleasanton, CA; Vetter, Kai M [Alameda, CA; Chivers, Daniel H [Fremont, CA

2012-02-07

Methods are presented that increase the position resolution and granularity of double sided segmented semiconductor detectors. These methods increase the imaging resolution capability of such detectors, either used as Compton cameras, or as position sensitive radiation detectors in imagers such as SPECT, PET, coded apertures, multi-pinhole imagers, or other spatial or temporal modulated imagers.

Systems for increasing the sensitivity of gamma-ray imagers

DOEpatents

Mihailescu, Lucian; Vetter, Kai M.; Chivers, Daniel H.

2012-12-11

Systems that increase the position resolution and granularity of double sided segmented semiconductor detectors are provided. These systems increase the imaging resolution capability of such detectors, either used as Compton cameras, or as position sensitive radiation detectors in imagers such as SPECT, PET, coded apertures, multi-pinhole imagers, or other spatial or temporal modulated imagers.

EndoTOFPET-US - A Miniaturised Calorimeter for Endoscopic Time-of-Flight Positron Emission Tomography

NASA Astrophysics Data System (ADS)

Zvolský, Milan; EndoTOFPET-US Collaboration

2015-02-01

In the scope of the EndoTOFPET-US project, a novel multimodal device for Ultrasound (US) Endoscopy and Positron Emission Tomography (PET) is being developed. The project aims at detecting and quantifying morphologic and functional markers and developing new biomarkers for pancreas and prostate oncology. Exploiting the Time-of-Flight (TOF) information of the gamma rays allows for a more sensitive, more precise and lower radiation- dose imaging and intervention on small internal structures. The detection of the gamma rays is realised with the help of scintillator crystals with Silicon Photomultiplier (SiPM) read-out, aiming at a coincidence time resolution of 200 ps and a spatial resolution of ≈ 1 mm. For the endoscopic detector, digital SiPMs are utilised for the first time in an instrument planned for clinical applications. The functionality of the instrument as well as the challenges that accompany the high miniaturisation of the endoscopic detector and the asymmetric and variable geometry of the system, are presented. The demands on the system involve the fields of scintillating crystallography, ultra-fast photon detection, highly integrated electronics, system integration as well as image reconstruction. The single detector components have been fully characterised and are performing up to specifications. Two dedicated ASIC chips have been developed for the project. The first PET images have been acquired with a test setup that consists solely of hardware and software developed within the collaboration and demonstrate that the data acquisition and reconstruction chain is operational. In this talk, the characterisation of the single components and the status of the detector integration and comissioning is presented.

Beam test results of the BTeV silicon pixel detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gabriele Chiodini et al.

2000-09-28

The authors have described the results of the BTeV silicon pixel detector beam test. The pixel detectors under test used samples of the first two generations of Fermilab pixel readout chips, FPIX0 and FPIX1, (indium bump-bonded to ATLAS sensor prototypes). The spatial resolution achieved using analog charge information is excellent for a large range of track inclination. The resolution is still very good using only 2-bit charge information. A relatively small dependence of the resolution on bias voltage is observed. The resolution is observed to depend dramatically on the discriminator threshold, and it deteriorates rapidly for threshold above 4000e{sup {minus}}.

First characterization of a digital SiPM based time-of-flight PET detector with 1 mm spatial resolution

NASA Astrophysics Data System (ADS)

Seifert, Stefan; van der Lei, Gerben; van Dam, Herman T.; Schaart, Dennis R.

2013-05-01

Monolithic scintillator detectors can offer a combination of spatial resolution, energy resolution, timing performance, depth-of-interaction information, and detection efficiency that make this type of detector a promising candidate for application in clinical, time-of-flight (TOF) positron emission tomography (PET). In such detectors the scintillation light is distributed over a relatively large number of photosensor pixels and the light intensity per pixel can be relatively low. Therefore, monolithic scintillator detectors are expected to benefit from the low readout noise offered by a novel photosensor called the digital silicon photomultiplier (dSiPM). Here, we present a first experimental characterization of a TOF PET detector comprising a 24 × 24 × 10 mm3 LSO:Ce,0.2%Ca scintillator read out by a dSiPM array (DPC-6400-44-22) developed by Philips Digital Photon Counting. A spatial resolution of ˜1 mm full-width-at-half-maximum (FWHM) averaged over the entire crystal was obtained (varying from just below 1 mm FWHM in the detector center to ˜1.2 mm FWHM close to the edges). Furthermore, the bias in the position estimation at the crystal edges that is typically found in monolithic scintillators is well below 1 mm even in the corners of the crystal.

Detector evaluation of a prototype amorphous selenium-based full field digital mammography system

NASA Astrophysics Data System (ADS)

Jesneck, Jonathan L.; Saunders, Robert S.; Samei, Ehsan; Xia, Jessie Q.; Lo, Joseph Y.

2005-04-01

This study evaluated the physical performance of a selenium-based direct full-field digital mammography prototype detector (Siemens Mammomat NovationDR), including the pixel value vs. exposure linearity, the modulation transfer function (MTF), the normalized noise power spectrum (NNPS), and the detective quantum efficiency (DQE). The current detector is the same model which received an approvable letter from FDA for release to the US market. The results of the current prototype are compared to those of an earlier prototype. Two IEC standard beam qualities (RQA-M2: Mo/Mo, 28 kVp, 2 mm Al; RQA-M4: Mo/Mo, 35 kVp, 2 mm Al) and two additional beam qualities (MW2: W/Rh, 28 kVp, 2 mm Al; MW4: W/Rh, 35 kVp, 2 mm Al) were investigated. To calculate the modulation transfer function (MTF), a 0.1 mm Pt-Ir edge was imaged at each beam quality. Detector pixel values responded linearly against exposure values (R2 0.999). As before, above 6 cycles/mm Mo/Mo MTF was slightly higher along the chest-nipple axis compared to the left-right axis. MTF was comparable to the previously reported prototype, with slightly reduced resolution. The DQE peaks ranged from 0.71 for 3.31 μC/kg (12.83 mR) to 0.4 for 0.48 μC/kg (1.86 mR) at 1.75 cycles/mm for Mo/Mo at 28 kVp. The DQE range for W/Rh at 28 kVP was 0.81 at 2.03 μC/kg (7.87 mR) to 0.50 at 0.50 μC/kg (1.94 mR) at 1 cycle/mm. NNPS tended to increase with greater exposures, while all exposures had a significant low-frequency component. Bloom and detector edge artifacts observed previously were no longer present in this prototype. The new detector shows marked noise improvement, with slightly reduced resolution. There remain artifacts due to imperfect gain calibration, but at a reduced magnitude compared to a prototype detector.

Charge Collection Efficiency in a segmented semiconductor detector interstrip region

NASA Astrophysics Data System (ADS)

Alarcon-Diez, V.; Vickridge, I.; Jakšić, M.; Grilj, V.; Schmidt, B.; Lange, H.

2017-09-01

Charged particle semiconductor detectors have been used in Ion Beam Analysis (IBA) for over four decades without great changes in either design or fabrication. However one area where improvement is desirable would be to increase the detector solid angle so as to improve spectrum statistics for a given incident beam fluence. This would allow the use of very low fluences opening the way, for example, to increase the time resolution in real-time RBS or for analysis of materials that are highly sensitive to beam damage. In order to achieve this goal without incurring the costs of degraded resolution due to kinematic broadening or large detector capacitance, a single-chip segmented detector (SEGDET) was designed and built within the SPIRIT EU infrastructure project. In this work we present the Charge Collection Efficiency (CCE) in the vicinity between two adjacent segments focusing on the interstrip zone. Microbeam Ion Beam Induced Charge (IBIC) measurements with different ion masses and energies were used to perform X-Y mapping of (CCE), as a function of detector operating conditions (bias voltage changes, detector housing possibilities and guard ring configuration). We show the (CCE) in the edge region of the active area and have also mapped the charge from the interstrip region, shared between adjacent segments. The results indicate that the electrical extent of the interstrip region is very close to the physical extent of the interstrip and guard ring structure with interstrip impacts contributing very little to the complete spectrum. The interstrip contributions to the spectra that do occur, can be substantially reduced by an offline anti-coincidence criterion applied to list mode data, which should also be easy to implement directly in the data acquisition software.

Magnetic Microcalorimeter (MMC) Gamma Detectors with Ultra-High Energy Resolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Friedrich, Stephen

The goal of this LCP is to develop ultra-high resolution gamma detectors based on magnetic microcalorimeters (MMCs) for accurate non-destructive analysis (NDA) of nuclear materials. For highest energy resolution, we will introduce erbium-doped silver (Ag:Er) as a novel sensor material, and implement several geometry and design changes to improve the signal-to-noise ratio. The detector sensitivity will be increased by developing arrays of 32 Ag:Er pixels read out by 16 SQUID preamplifiers, and by developing a cryogenic Compton veto to reduce the spectral background. Since best MMC performance requires detector operation at ~10 mK, we will purchase a dilution refrigerator withmore » a base temperature <10 mK and adapt it for MMC operation. The detector performance will be tested with radioactive sources of interest to the safeguards community.« less

Xenon detector with high energy resolution for gamma-ray line emission registration

NASA Astrophysics Data System (ADS)

Novikov, Alexander S.; Ulin, Sergey E.; Chernysheva, Irina V.; Dmitrenko, Valery V.; Grachev, Victor M.; Petrenko, Denis V.; Shustov, Alexander E.; Uteshev, Ziyaetdin M.; Vlasik, Konstantin F.

2014-09-01

A description of the xenon detector (XD) for gamma-ray line emission registration is presented. The detector provides high energy resolution and is able to operate under extreme environmental conditions (wide temperature range and unfavorable acoustic action). Resistance to acoustic noise as well as improvement in energy resolution has been achieved by means of real-time digital pulse processing. Another important XD feature is the ionization chamber's thin wall with composite housing, which significantly decreases the mass of the device and expands its energy range, especially at low energies.

The Effect of Twin Boundaries on the Spectroscopic Performance of CdZnTe Detectors

NASA Technical Reports Server (NTRS)

Parker, Bradford H.; Stahle, C. M.; Roth, D.; Babu, S.; Tueller, Jack; Powers, Edward I. (Technical Monitor)

2001-01-01

Most single grains in cadmium zinc telluride (CdZnTe) grown by the high-pressure Bridgman (HPB) technique contain multiple twin boundaries. As a consequence, twin boundaries are one of the most common macroscopic material defects found in large area (400 to 700 sq mm) CdZnTe specimens obtained from HPB ingots. Due to the prevalence of twin boundaries, understanding their effect on detector performance is key to the material selection process. Twin boundaries in several 2 mm thick large area specimens were first, documented using infrared transmission imaging. These specimens were then fabricated into either 2 mm pixel or planar detectors in order to examine the effect of the twin boundaries on detector performance. Preliminary results show that twin boundaries, which are decorated with tellurium inclusions, produce a reduction in detector efficiency and a degradation in resolution. The extent of the degradation appears to be a function of the density of tellurium inclusions.

Induced Charge Fluctuations in Semiconductor Detectors with a Cylindrical Geometry

NASA Astrophysics Data System (ADS)

Samedov, Victor V.

2018-01-01

Now, compound semiconductors are very appealing for hard X-ray room-temperature detectors for medical and astrophysical applications. Despite the attractive properties of compound semiconductors, such as high atomic number, high density, wide band gap, low chemical reactivity and long-term stability, poor hole and electron mobility-lifetime products degrade the energy resolution of these detectors. The main objective of the present study is in development of a mathematical model of the process of the charge induction in a cylindrical geometry with accounting for the charge carrier trapping. The formulae for the moments of the distribution function of the induced charge and the formulae for the mean amplitude and the variance of the signal at the output of the semiconductor detector with a cylindrical geometry were derived. It was shown that the power series expansions of the detector amplitude and the variance in terms of the inverse bias voltage allow determining the Fano factor, electron mobility lifetime product, and the nonuniformity level of the trap density of the semiconductor material.

2D dose distribution images of a hybrid low field MRI-γ detector

NASA Astrophysics Data System (ADS)

Abril, A.; Agulles-Pedrós, L.

2016-07-01

The proposed hybrid system is a combination of a low field MRI and dosimetric gel as a γ detector. The readout system is based on the polymerization process induced by the gel radiation. A gel dose map is obtained which represents the functional part of hybrid image alongside with the anatomical MRI one. Both images should be taken while the patient with a radiopharmaceutical is located inside the MRI system with a gel detector matrix. A relevant aspect of this proposal is that the dosimetric gel has never been used to acquire medical images. The results presented show the interaction of the 99mTc source with the dosimetric gel simulated in Geant4. The purpose was to obtain the planar γ 2D-image. The different source configurations are studied to explore the ability of the gel as radiation detector through the following parameters; resolution, shape definition and radio-pharmaceutical concentration.

Estimation of position resolution for DOI-PET detector using diameter 0.2 mm WLS fibers [ANIMMA--2015-IO-x5

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaneko, Naomi; Ito, H.; Han, S.

We have been developing a submillimeter resolution and low-cost DOI-PET detector using wavelength shifting fibers (WLSF), scintillating crystal plates and MPPCs (Hamamatsu Photonics). Conventional design of DOI-PET detectors had approximately mm{sup 3} of resolution by using some scintillating blocks with a volume of 1 mm{sup 3}, which detects gamma-ray. They are expensive due to difficulties in processing scintillating crystals and a large number of photo-detectors, and these technologies are likely to reach the limit of the resolution. Development of a lower cost DOI-PET detector with higher resolution is challenging to popularize the PET diagnosis. We propose two type of PETmore » detector. One is a whole body PET system, and the other is a PET system for brain or small animals. Each PET system consists 6 blocks. The former consists of 6 layers of crystal plates with 300 mm x 300 mm x 4 mm. The latter consists of 16 crystal layers, forming 4 x 4 crystal arrays. The size of the crystal plate is 40 mm x 40 mm x 1 mm. Wavelength shifting fiber (WLSF) sheets are attached to above and up and down side of crystal planes. The whole PET system has 8 MPPCs attached on each side. For the brain PET detector, 9 WLSF fibers are attached on the each side. The expected position resolution would be less than 1 mm at the former system. We have performed an experimental performance estimation for the system component using {sup 22}Na radioactive source. We achieved a collection efficiency of 10% using the WLSF sheet and Ce:Gd{sub 3}(Al,Ga){sub 5}O{sub 12} (GAGG) crystals at 511 keV. The linear relationship between reconstruction position and incident position was obtained, and a resolution of 0.7 mm (FWHM) for x-axis of DOI by the WLSF readout was achieved. (authors)« less

Basic performance evaluation of a Si-PM array-based LGSO phoswich DOI block detector for a high-resolution small animal PET system.

PubMed

Yamamoto, Seiichi

2013-07-01

The silicon photomultiplier (Si-PM) is a promising photodetector for PET. However, it remains unclear whether Si-PM can be used for a depth-of-interaction (DOI) detector based on the decay time differences of the scintillator where pulse shape analysis is used. For clarification, we tested the Hamamatsu 4 × 4 Si-PM array (S11065-025P) combined with scintillators that used different decay times to develop DOI block detectors using the pulse shape analysis. First, Ce-doped Gd(2)SiO(5) (GSO) scintillators of 0.5 mol% Ce were arranged in a 4 × 4 matrix and were optically coupled to the center of each pixel of the Si-PM array for measurement of the energy resolution as well as its gain variations according to the temperature. Then two types of Ce-doped Lu(1.9)Gd(0.1)Si0(5) (LGSO) scintillators, 0.025 mol% Ce (decay time: ~31 ns) and 0.75 mol% Ce (decay time: ~46 ns), were optically coupled in the DOI direction, arranged in a 11 × 7 matrix, and optically coupled to a Si-PM array for testing of the possibility of a high-resolution DOI detector. The energy resolution of the Si-PM array-based GSO block detector was 18 ± 4.4 % FWHM for a Cs-137 gamma source (662 keV). Less than 1 mm crystals were clearly resolved in the position map of the LGSO DOI block detector. The peak-to-valley ratio (P/V) derived from the pulse shape spectra of the LGSO DOI block detector was 2.2. These results confirmed that Si-PM array-based DOI block detectors are promising for high-resolution small animal PET systems.

Al/Ti/Al phonon-mediated KIDs for UV–vis light detection over large areas

NASA Astrophysics Data System (ADS)

Cardani, L.; Casali, N.; Cruciani, A.; le Sueur, H.; Martinez, M.; Bellini, F.; Calvo, M.; Castellano, M. G.; Colantoni, I.; Cosmelli, C.; D’Addabbo, A.; Di Domizio, S.; Goupy, J.; Minutolo, L.; Monfardini, A.; Vignati, M.

2018-07-01

The development of wide-area cryogenic light detectors with baseline energy resolution lower than 20 eV RMS is essential for next generation bolometric experiments searching for rare interactions. Indeed the simultaneous readout of the light and heat signals will enable background suppression through particle identification. Because of their excellent intrinsic energy resolution, as well as their well-established reproducibility, kinetic inductance detectors (KIDs) are good candidates for the development of next generation light detectors. The CALDER project is investigating the potential of phonon-mediated KIDs. The first phase of the project allowed to reach a baseline resolution of 80 eV using a single KID made of aluminum on a 2 × 2 cm2 silicon substrate acting as photon absorber. In this paper we present a new prototype detector implementing a trilayer aluminum–titanium–aluminum KID. Taking advantage of superconducting proximity effect the baseline resolution improves down to 26 eV.

Electron imaging with Medipix2 hybrid pixel detector.

PubMed

McMullan, G; Cattermole, D M; Chen, S; Henderson, R; Llopart, X; Summerfield, C; Tlustos, L; Faruqi, A R

2007-01-01

The electron imaging performance of Medipix2 is described. Medipix2 is a hybrid pixel detector composed of two layers. It has a sensor layer and a layer of readout electronics, in which each 55 microm x 55 microm pixel has upper and lower energy discrimination and MHz rate counting. The sensor layer consists of a 300 microm slab of pixellated monolithic silicon and this is bonded to the readout chip. Experimental measurement of the detective quantum efficiency, DQE(0) at 120 keV shows that it can reach approximately 85% independent of electron exposure, since the detector has zero noise, and the DQE(Nyquist) can reach approximately 35% of that expected for a perfect detector (4/pi(2)). Experimental measurement of the modulation transfer function (MTF) at Nyquist resolution for 120 keV electrons using a 60 keV lower energy threshold, yields a value that is 50% of that expected for a perfect detector (2/pi). Finally, Monte Carlo simulations of electron tracks and energy deposited in adjacent pixels have been performed and used to calculate expected values for the MTF and DQE as a function of the threshold energy. The good agreement between theory and experiment allows suggestions for further improvements to be made with confidence. The present detector is already very useful for experiments that require a high DQE at very low doses.

Image reconstruction of IRAS survey scans

NASA Technical Reports Server (NTRS)

Bontekoe, Tj. Romke

1990-01-01

The IRAS survey data can be used successfully to produce images of extended objects. The major difficulties, viz. non-uniform sampling, different response functions for each detector, and varying signal-to-noise levels for each detector for each scan, were resolved. The results of three different image construction techniques are compared: co-addition, constrained least squares, and maximum entropy. The maximum entropy result is superior. An image of the galaxy M51 with an average spatial resolution of 45 arc seconds is presented, using 60 micron survey data. This exceeds the telescope diffraction limit of 1 minute of arc, at this wavelength. Data fusion is a proposed method for combining data from different instruments, with different spacial resolutions, at different wavelengths. Data estimates of the physical parameters, temperature, density and composition, can be made from the data without prior image (re-)construction. An increase in the accuracy of these parameters is expected as the result of this more systematic approach.

Development of a Cost-Effective Modular Pixelated NaI(Tl) Detector for Clinical SPECT Applications

PubMed Central

Rozler, Mike; Liang, Haoning; Chang, Wei

2013-01-01

A new pixelated detector for high-resolution clinical SPECT applications was designed and tested. The modular detector is based on a scintillator block comprised of 2.75×2.75×10 mm3 NaI(Tl) pixels and decoded by an array of 51 mm diameter single-anode PMTs. Several configurations, utilizing two types of PMTs, were evaluated using a collimated beam source to measure positioning accuracy directly. Good pixel separation was observed, with correct pixel identification ranging from 60 to 72% averaged over the entire area of the modules, depending on the PMT type and configuration. This translates to a significant improvement in positioning accuracy compared to continuous slab detectors of the same thickness, along with effective reduction of “dead” space at the edges. The observed 10% average energy resolution compares well to continuous slab detectors. The combined performance demonstrates the suitability of pixelated detectors decoded with a relatively small number of medium-sized PMTs as a cost-effective approach for high resolution clinical SPECT applications, in particular those involving curved detector geometries. PMID:24146436

A Curved Image-Plate Detector System for High-Resolution Synchrotron X-ray Diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarin, P.; Haggerty, R; Yoon, W

2009-01-01

The developed curved image plate (CIP) is a one-dimensional detector which simultaneously records high-resolution X-ray diffraction (XRD) patterns over a 38.7 2{theta} range. In addition, an on-site reader enables rapid extraction, transfer and storage of X-ray intensity information in {le}30 s, and further qualifies this detector to study kinetic processes in materials science. The CIP detector can detect and store X-ray intensity information linearly proportional to the incident photon flux over a dynamical range of about five orders of magnitude. The linearity and uniformity of the CIP detector response is not compromised in the unsaturated regions of the image plate,more » regardless of saturation in another region. The speed of XRD data acquisition together with excellent resolution afforded by the CIP detector is unique and opens up wide possibilities in materials research accessible through X-ray diffraction. This article presents details of the basic features, operation and performance of the CIP detector along with some examples of applications, including high-temperature XRD.« less

Intrinsic limits on resolutions in muon- and electron-neutrino charged-current events in the KM3NeT/ORCA detector

NASA Astrophysics Data System (ADS)

Adrián-Martínez, S.; Ageron, M.; Aiello, S.; Albert, A.; Ameli, F.; Anassontzis, E. G.; Andre, M.; Androulakis, G.; Anghinolfi, M.; Anton, G.; Ardid, M.; Avgitas, T.; Barbarino, G.; Barbarito, E.; Baret, B.; Barrios-Mart, J.; Belias, A.; Berbee, E.; van den Berg, A.; Bertin, V.; Beurthey, S.; van Beveren, V.; Beverini, N.; Biagi, S.; Biagioni, A.; Billault, M.; Bondì, M.; Bormuth, R.; Bouhadef, B.; Bourlis, G.; Bourret, S.; Boutonnet, C.; Bouwhuis, M.; Bozza, C.; Bruijn, R.; Brunner, J.; Buis, E.; Buompane, R.; Busto, J.; Cacopardo, G.; Caillat, L.; Calamai, M.; Calvo, D.; Capone, A.; Caramete, L.; Cecchini, S.; Celli, S.; Champion, C.; Cherubini, S.; Chiarella, V.; Chiarelli, L.; Chiarusi, T.; Circella, M.; Classen, L.; Cobas, D.; Cocimano, R.; Coelho, J. A. B.; Coleiro, A.; Colonges, S.; Coniglione, R.; Cordelli, M.; Cosquer, A.; Coyle, P.; Creusot, A.; Cuttone, G.; D'Amato, C.; D'Amico, A.; D'Onofrio, A.; De Bonis, G.; De Sio, C.; Di Palma, I.; Díaz, A. F.; Distefano, C.; Donzaud, C.; Dornic, D.; Dorosti-Hasankiadeh, Q.; Drakopoulou, E.; Drouhin, D.; Durocher, M.; Eberl, T.; Eichie, S.; van Eijk, D.; El Bojaddaini, I.; Elsaesser, D.; Enzenhöfer, A.; Favaro, M.; Fermani, P.; Ferrara, G.; Frascadore, G.; Furini, M.; Fusco, L. A.; Gal, T.; Galatà, S.; Garufi, F.; Gay, P.; Gebyehu, M.; Giacomini, F.; Gialanella, L.; Giordano, V.; Gizani, N.; Gracia, R.; Graf, K.; Grégoire, T.; Grella, G.; Grmek, A.; Guerzoni, M.; Habel, R.; Hallmann, S.; van Haren, H.; Harissopulos, S.; Heid, T.; Heijboer, A.; Heine, E.; Henry, S.; Hernández-Rey, J. J.; Hevinga, M.; Hofestädt, J.; Hugon, C. M. F.; Illuminati, G.; James, C. W.; Jansweijerf, P.; Jongen, M.; de Jong, M.; Kadler, M.; Kalekin, O.; Kappes, A.; Katz, U. F.; Keller, P.; Kieft, G.; Kießling, D.; Koffeman, E. N.; Kooijman, P.; Kouchner, A.; Kreter, M.; Kulikovskiy, V.; Lahmann, R.; Lamare, P.; Larosa, G.; Leisos, A.; Leone, F.; Leonora, E.; Lindsey Clark, M.; Liolios, A.; Llorens Alvarez, C. D.; Lo Presti, D.; Löhner, H.; Lonardo, A.; Lotze, M.; Loucatos, S.; Maccioni, E.; Mannheim, K.; Manzali, M.; Margiotta, A.; Margotti, A.; Marinelli, A.; Maris, O.; Markou, C.; Martínez-Mora, J. A.; Martini, A.; Marzaioli, F.; Mele, R.; Melis, K. W.; Michael, T.; Migliozzi, P.; Migneco, E.; Mijakowski, P.; Miraglia, A.; Mollo, C. M.; Mongelli, M.; Morganti, M.; Moussa, A.; Musico, P.; Musumeci, M.; Navas, S.; Nicolau, C. A.; Olcina, I.; Olivetto, C.; Orlando, A.; Orzelli, A.; Pancaldi, G.; Papaikonomou, A.; Papaleo, R.; Păvălas, G. E.; Peek, H.; Pellegrini, G.; Pellegrino, C.; Perrina, C.; Pfutzner, M.; Piattelli, P.; Pikounis, K.; Pleinert, M.-O.; Poma, G. E.; Popa, V.; Pradier, T.; Pratolongo, F.; Pühlhofer, G.; Pulvirenti, S.; Quinn, L.; Racca, C.; Raffaelli, F.; Randazzo, N.; Rauch, T.; Real, D.; Resvanis, L.; Reubelt, J.; Riccobene, G.; Rossi, C.; Rovelli, A.; Saldaña, M.; Salvadori, I.; Samtleben, D. F. E.; Sánchez García, A.; Sánchez Losa, A.; Sanguineti, M.; Santangelo, A.; Santonocito, D.; Sapienza, P.; Schimmel, F.; Schmelling, J.; Schnabel, J.; Sciacca, V.; Sedita, M.; Seitz, T.; Sgura, I.; Simeone, F.; Sipala, V.; Spisso, B.; Spurio, M.; Stavropoulos, G.; Steijger, J.; Stellacci, S. M.; Stransky, D.; Taiuti, M.; Tayalati, Y.; Terrasi, F.; Tézier, D.; Theraube, S.; Timmer, P.; Tönnis, C.; Trasatti, L.; Travaglini, R.; Trovato, A.; Tsirigotis, A.; Tzamarias, S.; Tzamariudaki, E.; Vallage, B.; Van Elewyck, V.; Vermeulen, J.; Versari, F.; Vicini, P.; Viola, S.; Vivolo, D.; Volkert, M.; Wiggers, L.; Wilms, J.; de Wolf, E.; Zachariadou, K.; Zani, S.; Zornoza, J. D.; Zúñiga, J.

2017-05-01

Studying atmospheric neutrino oscillations in the few-GeV range with a multi-megaton detector promises to determine the neutrino mass hierarchy. This is the main science goal pursued by the future KM3NeT/ORCA water Cherenkov detector in the Mediterranean Sea. In this paper, the processes that limit the obtainable resolution in both energy and direction in charged-current neutrino events in the ORCA detector are investigated. These processes include the composition of the hadronic fragmentation products, the subsequent particle propagation and the photon-sampling fraction of the detector. GEANT simulations of neutrino interactions in seawater produced by GENIE are used to study the effects in the 1-20 GeV range. It is found that fluctuations in the hadronic cascade in conjunction with the variation of the inelasticity y are most detrimental to the resolutions. The effect of limited photon sampling in the detector is of significantly less importance. These results will therefore also be applicable to similar detectors/media, such as those in ice. [Figure not available: see fulltext.

Gas scintillation glass GEM detector for high-resolution X-ray imaging and CT

NASA Astrophysics Data System (ADS)

Fujiwara, T.; Mitsuya, Y.; Fushie, T.; Murata, K.; Kawamura, A.; Koishikawa, A.; Toyokawa, H.; Takahashi, H.

2017-04-01

A high-spatial-resolution X-ray-imaging gaseous detector has been developed with a single high-gas-gain glass gas electron multiplier (G-GEM), scintillation gas, and optical camera. High-resolution X-ray imaging of soft elements is performed with a spatial resolution of 281 μm rms and an effective area of 100×100 mm. In addition, high-resolution X-ray 3D computed tomography (CT) is successfully demonstrated with the gaseous detector. It shows high sensitivity to low-energy X-rays, which results in high-contrast radiographs of objects containing elements with low atomic numbers. In addition, the high yield of scintillation light enables fast X-ray imaging, which is an advantage for constructing CT images with low-energy X-rays.

Optimization of a LSO-Based Detector Module for Time-of-Flight PET

NASA Astrophysics Data System (ADS)

Moses, W. W.; Janecek, M.; Spurrier, M. A.; Szupryczynski, P.; Choong, W.-S.; Melcher, C. L.; Andreaco, M.

2010-06-01

We have explored methods for optimizing the timing resolution of an LSO-based detector module for a single-ring, “demonstration” time-of-flight PET camera. By maximizing the area that couples the scintillator to the PMT and minimizing the average path length that the scintillation photons travel, a single detector timing resolution of 218 ps fwhm is measured, which is considerably better than the 385 ps fwhm obtained by commercial LSO or LYSO TOF detector modules. We explored different surface treatments (saw-cut, mechanically polished, and chemically etched) and reflector materials (Teflon tape, ESR, Lumirror, Melinex, white epoxy, and white paint), and found that for our geometry, a chemically etched surface had 5% better timing resolution than the saw-cut or mechanically polished surfaces, and while there was little dependence on the timing resolution between the various reflectors, white paint and white epoxy were a few percent better. Adding co-dopants to LSO shortened the decay time from 40 ns to 30 ns but maintained the same or higher total light output. This increased the initial photoelectron rate and so improved the timing resolution by 15%. Using photomultiplier tubes with higher quantum efficiency (blue sensitivity index of 13.5 rather than 12) improved the timing resolution by an additional 5%. By choosing the optimum surface treatment (chemically etched), reflector (white paint), LSO composition (co-doped), and PMT (13.5 blue sensitivity index), the coincidence timing resolution of our detector module was reduced from 309 ps to 220 ps fwhm.

High-Resolution Hard X-Ray and Gamma-Ray Spectrometers Based on Superconducting Absorbers Coupled to Superconducting Transition Edge Sensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

van den Berg, M.; Chow, D.; Loshak, A.

2000-09-21

We are developing detectors based on bulk superconducting absorbers coupled to superconducting transition edge sensors (TES) for high-resolution spectroscopy of hard X-rays and soft gamma-rays. We have achieved an energy resolution of 70 eV FWHM at 60 keV using a 1 x 1 x 0.25 mm{sup 3} Sn absorber coupled to a Mo/Cu multilayer TES with a transition temperature of 100 mK. The response of the detector is compared with a simple model using only material properties data and characteristics derived from IV-measurements. We have also manufactured detectors using superconducting absorbers with a higher stopping power, such as Pb andmore » Ta. We present our first measurements of these detectors, including the thermalization characteristics of the bulk superconducting absorbers. The differences in performance between the detectors are discussed and an outline of the future direction of our detector development efforts is given.« less

Limitations on energy resolution of segmented silicon detectors

NASA Astrophysics Data System (ADS)

Wiącek, P.; Chudyba, M.; Fiutowski, T.; Dąbrowski, W.

2018-04-01

In the paper experimental study of charge division effects and energy resolution of X-ray silicon pad detectors are presented. The measurements of electrical parameters, capacitances and leakage currents, for six different layouts of pad arrays are reported. The X-ray spectra have been measured using a custom developed dedicated low noise front-end electronics. The spectra measured for six different detector layouts have been analysed in detail with particular emphasis on quantitative evaluation of charge division effects. Main components of the energy resolution due to Fano fluctuations, electronic noise, and charge division, have been estimated for six different sensor layouts. General recommendations regarding optimisation of pad sensor layout for achieving best possible energy resolution have been formulated.

Analysis of axial spatial resolution in a variable resolution x-ray cone beam CT (VRX-CBCT) system

NASA Astrophysics Data System (ADS)

Dahi, Bahram; Keyes, Gary S.; Rendon, David A.; DiBianca, Frank A.

2008-03-01

The Variable Resolution X-ray (VRX) technique has been successfully used in a Cone-Beam CT (CBCT) system to increase the spatial resolution of CT images in the transverse plane. This was achieved by tilting the Flat Panel Detector (FPD) to smaller vrx y angles in a VRX Cone Beam CT (VRX-CBCT) system. In this paper, the effect on the axial spatial resolution of CT images created by the VRX-CBCT system is examined at different vrx x angles, where vrx x is the tilting angle of the FPD about its x-axis. An amorphous silicon FPD with a CsI scintillator is coupled with a micro-focus x-ray tube to form a CBCT. The FPD is installed on a rotating frame that allows rotation of up to 90° about x and y axes of the FPD. There is no rotation about the z-axis (i.e. normal to the imaging surface). Tilting the FPD about its x-axis (i.e. decreasing the vrx x angle) reduces both the width of the line-spread function and the sampling distance by a factor of sin vrx x, thereby increasing the theoretical detector pre-sampling spatial resolution proportionately. This results in thinner CT slices that in turn help increase the axial spatial resolution of the CT images. An in-house phantom is used to measure the MTF of the reconstructed CT images at different vrx x angles.

Conceptual design and optimization of a plastic scintillator array for 2D tomography using a compact D-D fast neutron generator.

PubMed

Adams, Robert; Zboray, Robert; Cortesi, Marco; Prasser, Horst-Michael

2014-04-01

A conceptual design optimization of a fast neutron tomography system was performed. The system is based on a compact deuterium-deuterium fast neutron generator and an arc-shaped array of individual neutron detectors. The array functions as a position sensitive one-dimensional detector allowing tomographic reconstruction of a two-dimensional cross section of an object up to 10 cm across. Each individual detector is to be optically isolated and consists of a plastic scintillator and a Silicon Photomultiplier for measuring light produced by recoil protons. A deterministic geometry-based model and a series of Monte Carlo simulations were used to optimize the design geometry parameters affecting the reconstructed image resolution. From this, it is expected that with an array of 100 detectors a reconstructed image resolution of ~1.5mm can be obtained. Other simulations were performed in order to optimize the scintillator depth (length along the neutron path) such that the best ratio of direct to scattered neutron counts is achieved. This resulted in a depth of 6-8 cm and an expected detection efficiency of 33-37%. Based on current operational capabilities of a prototype neutron generator being developed at the Paul Scherrer Institute, planned implementation of this detector array design should allow reconstructed tomograms to be obtained with exposure times on the order of a few hours. Copyright © 2014 Elsevier Ltd. All rights reserved.

Quantitative 1D diffraction signatures during dual detector scatter VOI breast CBCT

NASA Astrophysics Data System (ADS)

LeClair, Robert J.

2017-03-01

Dual detector VOI scatter CBCT is similar to dual detector VOI CBCT except that during the high resolution scan, the low resolution flat panel detector is also used to capture the scattered photons. Simulations show a potential use of scatter to diagnose suspicious VOIs. Energy integrated signals due to scatter (EISs) were computed for a specific imaging task involving a malignant lesion and was labelled as a hypothetical experiment (expt) result. The signal was compared to predictions (pred) using benign and malignant lesions. The ΔEISs=EISs|expt - EISs|pred displayed eye catching diffraction structure when the prediction calculation used a benign lesion. The structure occurred even when the phantom compositions were different for prediction and experiment calculations. Since the diffraction structure has a circularly symmetric behaviour because the tissues are amorphous in nature, the 2D ΔEISs patterns were transformed to 1D signals. The 1D signals were obtained by calculating the mean ΔEISs signals in rings. The mean pixel values were a function of the momentum transfer argument q = 4π sin(θ/2)/λ which ranged from 12 to 46 nm-1. The 1D signals correlated well with the 2D profiles. Of particular interest were scatter signatures between q = 20 and 30 nm-1 where malignant tissue is predicted to scatter more than benign fibroglandular tissue. The 1D diffraction signatures could allow a better method to diagnose a suspicious lesion during dual detector scatter VOI CBCT.

Position sensitive and energy dispersive x-ray detector based on silicon strip detector technology

NASA Astrophysics Data System (ADS)

Wiącek, P.; Dąbrowski, W.; Fink, J.; Fiutowski, T.; Krane, H.-G.; Loyer, F.; Schwamberger, A.; Świentek, K.; Venanzi, C.

2015-04-01

A new position sensitive detector with a global energy resolution for the entire detector of about 380 eV FWHM for 8.04 keV line at ambient temperature is presented. The measured global energy resolution is defined by the energy spectra summed over all strips of the detector, and thus it includes electronic noise of the front-end electronics, charge sharing effects, matching of parameters across the channels and other system noise sources. The target energy resolution has been achieved by segmentation of the strips to reduce their capacitance and by careful optimization of the front-end electronics. The key design aspects and parameters of the detector are discussed briefly in the paper. Excellent noise and matching performance of the readout ASIC and negligible system noise allow us to operate the detector with a discrimination threshold as low as 1 keV and to measure fluorescence radiation lines of light elements, down to Al Kα of 1.49 keV, simultaneously with measurements of the diffraction patterns. The measurement results that demonstrate the spectrometric and count rate performance of the developed detector are presented and discussed in the paper.

Progress in the Development of CdZnTe Unipolar Detectors for Different Anode Geometries and Data Corrections

PubMed Central

Zhang, Qiushi; Zhang, Congzhe; Lu, Yanye; Yang, Kun; Ren, Qiushi

2013-01-01

CdZnTe detectors have been under development for the past two decades, providing good stopping power for gamma rays, lightweight camera heads and improved energy resolution. However, the performance of this type of detector is limited primarily by incomplete charge collection problems resulting from charge carriers trapping. This paper is a review of the progress in the development of CdZnTe unipolar detectors with some data correction techniques for improving performance of the detectors. We will first briefly review the relevant theories. Thereafter, two aspects of the techniques for overcoming the hole trapping issue are summarized, including irradiation direction configuration and pulse shape correction methods. CdZnTe detectors of different geometries are discussed in detail, covering the principal of the electrode geometry design, the design and performance characteristics, some detector prototypes development and special correction techniques to improve the energy resolution. Finally, the state of art development of 3-D position sensing and Compton imaging technique are also discussed. Spectroscopic performance of CdZnTe semiconductor detector will be greatly improved even to approach the statistical limit on energy resolution with the combination of some of these techniques. PMID:23429509

The effects of Doppler broadening and detector resolution on the performance of three-stage Compton cameras

PubMed Central

Mackin, Dennis; Polf, Jerimy; Peterson, Steve; Beddar, Sam

2013-01-01

Purpose: The authors investigated how the characteristics of the detectors used in a three-stage Compton camera (CC) affect the CC's ability to accurately measure the emission distribution and energy spectrum of prompt gammas (PG) emitted by nuclear de-excitations during proton therapy. The detector characteristics they studied included the material (high-purity germanium [HPGe] and cadmium zinc telluride [CZT]), Doppler broadening (DB), and resolution (lateral, depth, and energy). Methods: The authors simulated three-stage HPGe and CZT CCs of various configurations, detecting gammas from point sources with energies ranging from 0.511 to 7.12 MeV. They also simulated a proton pencil beam irradiating a tissue target to study how the detector characteristics affect the PG data measured by CCs in a clinical proton therapy setting. They used three figures of merit: the distance of closest approach (DCA) and the point of closest approach (PCA) between the measured and actual position of the PG emission origin, and the calculated energy resolution. Results: For CCs with HPGe detectors, DB caused the DCA to be greater than 3 mm for 14% of the 6.13 MeV gammas and 20% of the 0.511 MeV gammas. For CCs with CZT detectors, DB caused the DCA to be greater than 3 mm for 18% of the 6.13 MeV gammas and 25% of the 0.511 MeV gammas. The full width at half maximum (FWHM) of the PCA in the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}\\hat z\\end{equation*} \\end{document}z^ direction for HPGe and CZT detectors ranged from 1.3 to 0.4 mm for gammas with incident energy ranging from 0.511 to 7.12 MeV. For CCs composed of HPGe detectors, the resolution of incident gamma energy calculated by the CC ranged from 6% to 1% for gammas with true incident energies from 0.511 to 7.12 MeV. For CCs composed of CZT detectors, the resolution of gamma energy calculated by the CC ranged from 10% to 1% for gammas with true incident energies from 0.511 to 7.12 MeV. For HPGe and CZT CCs in which all detector effect were included, the DCA was less than 3 mm for 75% and 68% of the detected gammas, respectively, and restricting gammas to those having energy greater than 2.0 MeV increased these percentages to 83% and 77% for HPGe and CZT, respectively. Distributions of the true gamma origins and the PCA after detector characteristics had been included showed good agreement on beam range and some loss of resolution for the lateral profile of the PG emission. Characteristic energy lines were evident in the calculated gamma energy spectrum. Conclusions: The authors found the following: (1) DB is the dominant source of spatial and energy resolution loss in the CCs at all energy levels; (2) the largest difference in the spatial resolution of HPGe and CZT CCs is that the spatial resolution distributions of CZT have broader tails. The differences in the FWHM of these distributions are small; (3) the energy resolution of both HPGe and CZT three-stage CCs is adequate for PG spectroscopy; and (4) restricting the gammas to those having energy greater than 2.0 MeV can improve the achievable image resolution. PMID:23298111

Optimizing modelling in iterative image reconstruction for preclinical pinhole PET

NASA Astrophysics Data System (ADS)

Goorden, Marlies C.; van Roosmalen, Jarno; van der Have, Frans; Beekman, Freek J.

2016-05-01

The recently developed versatile emission computed tomography (VECTor) technology enables high-energy SPECT and simultaneous SPECT and PET of small animals at sub-mm resolutions. VECTor uses dedicated clustered pinhole collimators mounted in a scanner with three stationary large-area NaI(Tl) gamma detectors. Here, we develop and validate dedicated image reconstruction methods that compensate for image degradation by incorporating accurate models for the transport of high-energy annihilation gamma photons. Ray tracing software was used to calculate photon transport through the collimator structures and into the gamma detector. Input to this code are several geometric parameters estimated from system calibration with a scanning 99mTc point source. Effects on reconstructed images of (i) modelling variable depth-of-interaction (DOI) in the detector, (ii) incorporating photon paths that go through multiple pinholes (‘multiple-pinhole paths’ (MPP)), and (iii) including various amounts of point spread function (PSF) tail were evaluated. Imaging 18F in resolution and uniformity phantoms showed that including large parts of PSFs is essential to obtain good contrast-noise characteristics and that DOI modelling is highly effective in removing deformations of small structures, together leading to 0.75 mm resolution PET images of a hot-rod Derenzo phantom. Moreover, MPP modelling reduced the level of background noise. These improvements were also clearly visible in mouse images. Performance of VECTor can thus be significantly improved by accurately modelling annihilation gamma photon transport.

A Recommended Procedure for Estimating the Cosmic-Ray Spectral Parameter of a Simple Power Law With Applications to Detector Design

NASA Technical Reports Server (NTRS)

Howell, L. W.

2001-01-01

A simple power law model consisting of a single spectral index alpha-1 is believed to be an adequate description of the galactic cosmic-ray (GCR) proton flux at energies below 10(exp 13) eV. Two procedures for estimating alpha-1 the method of moments and maximum likelihood (ML), are developed and their statistical performance compared. It is concluded that the ML procedure attains the most desirable statistical properties and is hence the recommended statistical estimation procedure for estimating alpha-1. The ML procedure is then generalized for application to a set of real cosmic-ray data and thereby makes this approach applicable to existing cosmic-ray data sets. Several other important results, such as the relationship between collecting power and detector energy resolution, as well as inclusion of a non-Gaussian detector response function, are presented. These results have many practical benefits in the design phase of a cosmic-ray detector as they permit instrument developers to make important trade studies in design parameters as a function of one of the science objectives. This is particularly important for space-based detectors where physical parameters, such as dimension and weight, impose rigorous practical limits to the design envelope.

Study of the spatial resolution of low-material GEM tracking detectors

NASA Astrophysics Data System (ADS)

Kudryavtsev, V. N.; Maltsev, T. V.; Shekhtman, L. I.

2018-02-01

The spatial resolution of GEM based tracking detectors has been simulated and measured. The simulation includes the GEANT4 based transport of high energy electrons with careful accounting for atomic relaxation processes including emission of fluorescent photons and Auger electrons and custom post-processing, including accounting for diffusion, gas amplification fluctuations, the distribution of signals on readout electrodes, electronics noise and a particular algorithm of the final coordinate calculation (center of gravity). The simulation demonstrates that a minimum of the spatial resolution of about 10 μm can be achieved with strip pitches from 250 μm to 300 μm. For larger pitches the resolution is quickly degrading reaching 80-100 μm at a pitch of 500 μm. The spatial resolution of low-material triple-GEM detectors for the DEUTRON facility at the VEPP-3 storage ring is measured at the extracted beam facility of the VEPP-4M collider. The amount of material in these detectors is reduced by etching the copper of the GEMs electrodes and using a readout structure on a thin kapton foil rather than on a glass fibre plate. The exact amount of material in one DEUTRON detector is measured by studying multiple scattering of 100 MeV electrons in it. The result of these measurements is X/X0 = 2.4×10-3 corresponding to a thickness of the copper layers of the GEM foils of 3 μm. The spatial resolution of one DEUTRON detector is measured with 500 MeV electrons and the measured value is equal to 35 ± 1 μm for orthogonal tracks.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andrews, Madison Theresa; Bates, Cameron Russell; Mckigney, Edward Allen

Here, this work presents the organic scintillation simulation capabilities of DRiFT, a post-processing Detector Response Function Toolkit for MCNPR output. DRiFT is used to create realistic scintillation detector response functions to incident neutron and gamma mixed- field radiation. As a post-processing tool, DRiFT leverages the extensively validated radiation transport capabilities of MCNPR ®6, which also provides the ability to simulate complex sources and geometries. DRiFT is designed to be flexible, it allows the user to specify scintillator material, PMT type, applied PMT voltage, and quenching data used in simulations. The toolkit's capabilities, which include the generation of pulse shape discriminationmore » plots and full-energy detector spectra, are demonstrated in a comparison of measured and simulated neutron contributions from 252Cf and PuBe, and photon spectra from 22Na and 228Th sources. DRiFT reproduced energy resolution effects observed in EJ-301 measurements through the inclusion of scintillation yield variances, photon transport noise, and PMT photocathode and multiplication noise.« less

Region-of-interest cone beam computed tomography (ROI CBCT) with a high resolution CMOS detector.

PubMed

Jain, A; Takemoto, H; Silver, M D; Nagesh, S V S; Ionita, C N; Bednarek, D R; Rudin, S

Cone beam computed tomography (CBCT) systems with rotational gantries that have standard flat panel detectors (FPD) are widely used for the 3D rendering of vascular structures using Feldkamp cone beam reconstruction algorithms. One of the inherent limitations of these systems is limited resolution (<3 lp/mm). There are systems available with higher resolution but their small FOV limits them to small animal imaging only. In this work, we report on region-of-interest (ROI) CBCT with a high resolution CMOS detector (75 μm pixels, 600 μm HR-CsI) mounted with motorized detector changer on a commercial FPD-based C-arm angiography gantry (194 μm pixels, 600 μm HL-CsI). A cylindrical CT phantom and neuro stents were imaged with both detectors. For each detector a total of 209 images were acquired in a rotational protocol. The technique parameters chosen for the FPD by the imaging system were used for the CMOS detector. The anti-scatter grid was removed and the incident scatter was kept the same for both detectors with identical collimator settings. The FPD images were reconstructed for the 10 cm x10 cm FOV and the CMOS images were reconstructed for a 3.84 cm × 3.84 cm FOV. Although the reconstructed images from the CMOS detector demonstrated comparable contrast to the FPD images, the reconstructed 3D images of the neuro stent clearly showed that the CMOS detector improved delineation of smaller objects such as the stent struts (~70 μm) compared to the FPD. Further development and the potential for substantial clinical impact are suggested.

Solid xenon radiation detectors

NASA Astrophysics Data System (ADS)

Dolinski, Michelle J.

2014-03-01

Cryogenic liquid xenon detectors have become a popular technology in the search for rare events, such as dark matter interactions and neutrinoless double beta decay. The power of the liquid xenon detector technology is in the combination of the ionization and scintillation signals, resulting in particle discrimination and improved energy resolution over the ionization-only signal. The improved energy resolution results from a unique anti-correlation phenomenon that has not been described from first principles. Solid xenon bolometers, under development at Drexel University, are expected to have excellent counting statistics in the phonon channel, with energy resolution of 0.1% or better. This additional energy channel may offer the final piece of the puzzle in understanding liquid xenon detector energy response. Supported by a grant from the Charles E. Kaufman Foundation.

Singular value decomposition metrics show limitations of detector design in diffuse fluorescence tomography

PubMed Central

Leblond, Frederic; Tichauer, Kenneth M.; Pogue, Brian W.

2010-01-01

The spatial resolution and recovered contrast of images reconstructed from diffuse fluorescence tomography data are limited by the high scattering properties of light propagation in biological tissue. As a result, the image reconstruction process can be exceedingly vulnerable to inaccurate prior knowledge of tissue optical properties and stochastic noise. In light of these limitations, the optimal source-detector geometry for a fluorescence tomography system is non-trivial, requiring analytical methods to guide design. Analysis of the singular value decomposition of the matrix to be inverted for image reconstruction is one potential approach, providing key quantitative metrics, such as singular image mode spatial resolution and singular data mode frequency as a function of singular mode. In the present study, these metrics are used to analyze the effects of different sources of noise and model errors as related to image quality in the form of spatial resolution and contrast recovery. The image quality is demonstrated to be inherently noise-limited even when detection geometries were increased in complexity to allow maximal tissue sampling, suggesting that detection noise characteristics outweigh detection geometry for achieving optimal reconstructions. PMID:21258566

On the resolution of a MIEZE spectrometer

NASA Astrophysics Data System (ADS)

Martin, N.

2018-02-01

We study the effect of a finite sample size, beam divergence and detector thickness on the resolution function of a MIEZE spectrometer. We provide a transparent analytical framework which can be used to determine the optimal trade-off between incoming flux and time-resolution for a given experimental configuration. The key result of our approach is that the usual limiting factor of MIEZE spectroscopy, namely neutron path length differences throughout the instrument, can be suppressed up to relatively large momentum transfers by using a proper small-angle (SANS) geometry. Under such configuration, the hitherto accepted limits of MIEZE spectroscopy in terms of time-resolution are pushed upwards by typically an order of magnitude, giving access to most of the topical fields in soft- and hard-condensed matter physics.

Radiation imaging with optically read out GEM-based detectors

NASA Astrophysics Data System (ADS)

Brunbauer, F. M.; Lupberger, M.; Oliveri, E.; Resnati, F.; Ropelewski, L.; Streli, C.; Thuiner, P.; van Stenis, M.

2018-02-01

Modern imaging sensors allow for high granularity optical readout of radiation detectors such as MicroPattern Gaseous Detectors (MPGDs). Taking advantage of the high signal amplification factors achievable by MPGD technologies such as Gaseous Electron Multipliers (GEMs), highly sensitive detectors can be realised and employing gas mixtures with strong scintillation yield in the visible wavelength regime, optical readout of such detectors can provide high-resolution event representations. Applications from X-ray imaging to fluoroscopy and tomography profit from the good spatial resolution of optical readout and the possibility to obtain images without the need for extensive reconstruction. Sensitivity to low-energy X-rays and energy resolution permit energy resolved imaging and material distinction in X-ray fluorescence measurements. Additionally, the low material budget of gaseous detectors and the possibility to couple scintillation light to imaging sensors via fibres or mirrors makes optically read out GEMs an ideal candidate for beam monitoring detectors in high energy physics as well as radiotherapy. We present applications and achievements of optically read out GEM-based detectors including high spatial resolution imaging and X-ray fluorescence measurements as an alternative readout approach for MPGDs. A detector concept for low intensity applications such as X-ray crystallography, which maximises detection efficiency with a thick conversion region but mitigates parallax-induced broadening is presented and beam monitoring capabilities of optical readout are explored. Augmenting high resolution 2D projections of particle tracks obtained with optical readout with timing information from fast photon detectors or transparent anodes for charge readout, 3D reconstruction of particle trajectories can be performed and permits the realisation of optically read out time projection chambers. Combining readily available high performance imaging sensors with compatible scintillating gases and the strong signal amplification factors achieved by MPGDs makes optical readout an attractive alternative to the common concept of electronic readout of radiation detectors. Outstanding signal-to-noise ratios and robustness against electronic noise allow unprecedented imaging capabilities for various applications in fields ranging from high energy physics to medical instrumentation.

Fast and high resolution thermal detector based on an aluminum nitride piezoelectric microelectromechanical resonator with an integrated suspended heat absorbing element

NASA Astrophysics Data System (ADS)

Hui, Yu; Rinaldi, Matteo

2013-03-01

This letter presents a miniaturized, fast, and high resolution thermal detector, in which a heat absorbing element and a temperature sensitive microelectromechanical system (MEMS) resonator are perfectly overlapped but separated by a microscale air gap. This unique design guarantees efficient and fast (˜10s μs) heat transfer from the absorbing element to the temperature sensitive device and enables high resolution thermal power detection (˜nW), thanks to the low noise performance of the high quality factor (Q = 2305) MEMS resonant thermal detector. A device prototype was fabricated, and its detection capabilities were experimentally characterized. A thermal power as low as 150 nW was experimentally measured, and a noise equivalent power of 6.5 nW/Hz1/2 was extracted. A device thermal time constant of only 350 μs was measured (smallest ever reported for MEMS resonant thermal detectors), indicating the great potential of the proposed technology for the implementation of ultra-fast and high resolution un-cooled resonant thermal detectors.

Recent Developments in Transition-Edge Strip Detectors for Solar X-Rays

NASA Technical Reports Server (NTRS)

Rausch, Adam J.; Deiker, Steven W.; Hilton, Gene; Irwin, Kent D.; Martinez-Galarce, Dennis S.; Shing, Lawrence; Stern, Robert A.; Ullom, Joel N.; Vale, Leila R.

2008-01-01

LMSAL and NIST are developing position-sensitive x-ray strip detectors based on Transition Edge Sensor (TES) microcalorimeters optimized for solar physics. By combining high spectral (E/ delta E approximately equals 1600) and temporal (single photon delta t approximately equals 10 micro s) resolutions with imaging capabilities, these devices will be able to study high-temperature (>l0 MK) x-ray lines as never before. Diagnostics from these lines should provide significant new insight into the physics of both microflares and the early stages of flares. Previously, the large size of traditional TESs, along with the heat loads associated with wiring large arrays, presented obstacles to using these cryogenic detectors for solar missions. Implementing strip detector technology at small scales, however, addresses both issues: here, a line of substantially smaller effective pixels requires only two TESs, decreasing both the total array size and the wiring requirements for the same spatial resolution. Early results show energy resolutions of delta E(sub fwhm) approximately equals 30 eV and spatial resolutions of approximately 10-15 micron, suggesting the strip-detector concept is viable.

A large area high resolution imaging detector for fast atom diffraction

NASA Astrophysics Data System (ADS)

Lupone, Sylvain; Soulisse, Pierre; Roncin, Philippe

2018-07-01

We describe a high resolution imaging detector based on a single 80 mm micro-channel-plate (MCP) and a phosphor screen mounted on a UHV flange of only 100 mm inner diameter. It relies on standard components and we describe its performance with one or two MCPs. A resolution of 80 μm rms is observed on the beam profile. At low count rate, individual impact can be pinpointed with few μm accuracy but the resolution is probably limited by the MCP channel diameter. The detector has been used to record the diffraction of fast atoms at grazing incidence on crystal surfaces (GIFAD), a technique probing the electronic density of the topmost layer only. The detector was also used to record the scattering profile during azimuthal scan of the crystal to produce triangulation curves revealing the surface crystallographic directions of molecular layers. It should also be compatible with reflection high energy electron (RHEED) experiment when fragile surfaces require a low exposure to the electron beam. The discussions on the mode of operation specific to diffraction experiments apply also to commercial detectors.

Spatially-resolved HPGe Gamma-ray Spectroscopy of Swipe Samples

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDonald, Benjamin S.; VanDevender, Brent A.; Wood, Lynn S.

Measurement of swipe samples is a critical element of the National Technical Nuclear Forensics (NTNF) mission. A unique, portable, germanium gamma imager (GeGI-s) from PHDS Co may provide complementary information to current techniques for swipe sample screening. The GeGI-s is a modified version of the commercial GeGI-4, a planar HPGe detector, capable of several million counts per second across the whole detector. The GeGI-s detector is a prototype of a commercial off-the-shelf high rate GeGI. The high rate capability allows high-activity samples be placed directly on the face of the detector. Utilizing the high energy resolution and pixelization of themore » detector, the GeGI-s can generate isotope specific spatial maps of the materials on the swipe sample. To prove this technology is viable for such mapping, the GeGI-s detector response to spatially distributed events must be well characterized. The detection efficiency as a function of location has been characterized to understand the non-uniformities presented as a collimated photon beam was rastered vertically and horizontally across the face of the detector. The detection efficiency as a function of location has been characterized to understand the non-uniformities presented as a collimated photon beam was rastered vertically and horizontally across the face of the detector. The response was found to be primarily uniform and symmetric, however two causes of non-uniformity were found. Both of these causes can ultimately be corrected for in off-line data analysis.« less

The Morava E-theories of finite general linear groups

NASA Astrophysics Data System (ADS)

Mattafirri, Sara

The feasibility of producing an image of radioactivity distribution within a patient or confined region of space using information carried by the gamma-rays emitted from the source is investigated. The imaging approach makes use of parameters related to the gamma-rays which undergo Compton scattering within a detection system, it does not involve the use of pin-holes, and it employs gamma-rays of energy ranging from a few hundreds of keVs to MeVs. Energy range of the photons and absence of pin-holes aim to provide larger pool of radioisotopes and larger efficiency than other emission imaging modalities, such as single photon emission computed tomography and positron emission tomography, making it possible to investigate larger pool of functions and smaller radioactivity doses. The observables available to produce the image are the gamma-ray position of interaction and energy deposition during Compton scattering within the detection systems. Image reconstruction methodologies such as backprojection and list-mode maximum likelihood expectation maximization algorithm are characterized and applied to produce images of simulated and experimental sources on the basis of the observed parameters. Given the observables and image reconstruction methodologies, imaging systems based on minimizing the variation of the impulse response with position within the field of view are developed. The approach allows imaging of three-dimensional sources when an imaging system which provides full 4 pi view of the object is used and imaging of two-dimensional sources when a single block-type detector which provides one view of the object is used. Geometrical resolution of few millimeters is obtained at few centimeters from the detection system if employing gamma-rays of energy in the order of few hundreds of keVs and current state of the art semi-conductor detectors; At this level of resolution, detection efficiency is in the order of 10-3 at few centimeters from the detector when a single block detector few centimeters in size is used. The resolution significantly improves with increasing energy of the photons and it degrades roughly linearly with increasing distance from the detector; Larger detection efficiency can be obtained at the expenses of resolution or via targeted configurations of the detector. Results pave the way for image reconstruction of practical gamma-ray emitting sources.

Photon Detector System Timing Performance in the DUNE 35-ton Prototype Liquid Argon Time Projection Chamber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adams, D.L.; et al.

The 35-ton prototype for the Deep Underground Neutrino Experiment far detector was a single-phase liquid argon time projection chamber with an integrated photon detector system, all situated inside a membrane cryostat. The detector took cosmic-ray data for six weeks during the period of February 1, 2016 to March 12, 2016. The performance of the photon detection system was checked with these data. An installed photon detector was demonstrated to measure the arrival times of cosmic-ray muons with a resolution better than 32 ns, limited by the timing of the trigger system. A measurement of the timing resolution using closely-spaced calibration pulses yielded a resolution of 15 ns for pulses at a level of 6 photo-electrons. Scintillation light from cosmic-ray muons was observed to be attenuated with increasing distance with a characteristic length ofmore » $$155 \\pm 28$$ cm.« less

Thallium bromide radiation detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shah, K.S.; Lund, J.C.; Olschner, F.

1989-02-01

Radiation detectors have been fabricated from crystals of the semiconductor material thallium bromide (TlBr) and the performance of these detectors as room temperature photon spectrometers has been measured. These detectors exhibit improved energy resolution over previously reported TlBr detectors. These results indicate that TlBr is a very promising radiation detector material.

Phase contrast tomography of the mouse cochlea at microfocus x-ray sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartels, Matthias; Krenkel, Martin; Hernandez, Victor H.

2013-08-19

We present phase contrast x-ray tomography of functional soft tissue within the bony cochlear capsule of mice, carried out at laboratory microfocus sources with well-matched source, detector, geometry, and reconstruction algorithms at spatial resolutions down to 2 μm. Contrast, data quality and resolution enable the visualization of thin membranes and nerve fibers as well as automated segmentation of surrounding bone. By complementing synchrotron radiation imaging techniques, a broad range of biomedical applications becomes possible as demonstrated for optogenetic cochlear implant research.

Accelerator test of the coded aperture mask technique for gamma-ray astronomy

NASA Technical Reports Server (NTRS)

Jenkins, T. L.; Frye, G. M., Jr.; Owens, A.; Carter, J. N.; Ramsden, D.

1982-01-01

A prototype gamma-ray telescope employing the coded aperture mask technique has been constructed and its response to a point source of 20 MeV gamma-rays has been measured. The point spread function is approximately a Gaussian with a standard deviation of 12 arc minutes. This resolution is consistent with the cell size of the mask used and the spatial resolution of the detector. In the context of the present experiment, the error radius of the source position (90 percent confidence level) is 6.1 arc minutes.

Capillary electrophoresis-high resolution sector field inductively coupled plasma mass spectrometry.

PubMed

Sonke, Jeroen E; Salters, Vincent J M

2007-08-03

The background and applications of high resolution sector field inductively coupled plasma mass spectrometry (HR-ICP-MS) as a detector for capillary (CE) and gel electrophoretic separations are reviewed. Notable progress has been made in the fields of bioinorganic and environmental (geo-) chemistry. Metallomics, the study of metal species interactions and functions in biological systems, puts substantial technical demands on speciation analysis. The combination of high species resolving power (CE) and high sensitivity-high mass resolving power (HR-ICP-MS) provides a solid base to meet such demands.

Sensitivity of a low threshold directional detector to CNO-cycle solar neutrinos

NASA Astrophysics Data System (ADS)

Bonventre, R.; Orebi Gann, G. D.

2018-06-01

A first measurement of neutrinos from the CNO fusion cycle in the Sun would allow a resolution to the current solar metallicity problem. Detection of these low-energy neutrinos requires a low-threshold detector, while discrimination from radioactive backgrounds in the region of interest is significantly enhanced via directional sensitivity. This combination can be achieved in a water-based liquid scintillator target, which offers enhanced energy resolution beyond a standard water Cherenkov detector. We study the sensitivity of such a detector to CNO neutrinos under various detector and background scenarios, and draw conclusions about the requirements for such a detector to successfully measure the CNO neutrino flux. A detector designed to measure CNO neutrinos could also achieve a few-percent measurement of pep neutrinos.

Microtomography with photon counting detectors: improving the quality of tomographic reconstruction by voxel-space oversampling

NASA Astrophysics Data System (ADS)

Dudak, J.; Zemlicka, J.; Karch, J.; Hermanova, Z.; Kvacek, J.; Krejci, F.

2017-01-01

Photon counting detectors Timepix are known for their unique properties enabling X-ray imaging with extremely high contrast-to-noise ratio. Their applicability has been recently further improved since a dedicated technique for assembling large area Timepix detector arrays was introduced. Despite the fact that the sensitive area of Timepix detectors has been significantly increased, the pixel pitch is kept unchanged (55 microns). This value is much larger compared to widely used and popular X-ray imaging cameras utilizing scintillation crystals and CCD-based read-out. On the other hand, photon counting detectors provide steeper point-spread function. Therefore, with given effective pixel size of an acquired radiography, Timepix detectors provide higher spatial resolution than X-ray cameras with scintillation-based devices unless the image is affected by penumbral blur. In this paper we take an advance of steep PSF of photon counting detectors and test the possibility to improve the quality of computed tomography reconstruction using finer sampling of reconstructed voxel space. The achieved results are presented in comparison with data acquired under the same conditions using a commercially available state-of-the-art CCD X-ray camera.

High resolution scintillation detector with semiconductor readout

DOEpatents

Levin, Craig S.; Hoffman, Edward J.

2000-01-01

A novel high resolution scintillation detector array for use in radiation imaging such as high resolution Positron Emission Tomography (PET) which comprises one or more parallelepiped crystals with at least one long surface of each crystal being in intimate contact with a semiconductor photodetector such that photons generated within each crystal by gamma radiation passing therethrough is detected by the photodetector paired therewith.

Development of MMC Gamma Detectors for Precise Characterization of Uranium Isotopes

NASA Astrophysics Data System (ADS)

Kim, G. B.; Flynn, C. C.; Kempf, S.; Gastaldo, L.; Fleischmann, A.; Enss, C.; Friedrich, S.

2018-06-01

Precise nuclear data from radioactive decays are important for the accurate non-destructive assay of fissile materials in nuclear safeguards. We are developing high energy resolution gamma detectors based on metallic magnetic calorimeters (MMCs) to accurately measure gamma-ray energies and branching ratios of uranium isotopes. Our MMC gamma detectors exhibit good linearity, reproducibility and a consistent response function for low energy gamma-rays. We illustrate the capabilities of MMCs to improve literature values of nuclear data with an analysis of gamma spectra of U-233. In this context, we also improve the value of the energy for the single gamma-ray of the U-233 daughter Ra-225 by over an order of magnitude from 40.09 ± 0.05 to 40.0932 ± 0.0007 keV.

Circuit for high resolution decoding of multi-anode microchannel array detectors

NASA Technical Reports Server (NTRS)

Kasle, David B. (Inventor)

1995-01-01

A circuit for high resolution decoding of multi-anode microchannel array detectors consisting of input registers accepting transient inputs from the anode array; anode encoding logic circuits connected to the input registers; midpoint pipeline registers connected to the anode encoding logic circuits; and pixel decoding logic circuits connected to the midpoint pipeline registers is described. A high resolution algorithm circuit operates in parallel with the pixel decoding logic circuit and computes a high resolution least significant bit to enhance the multianode microchannel array detector's spatial resolution by halving the pixel size and doubling the number of pixels in each axis of the anode array. A multiplexer is connected to the pixel decoding logic circuit and allows a user selectable pixel address output according to the actual multi-anode microchannel array detector anode array size. An output register concatenates the high resolution least significant bit onto the standard ten bit pixel address location to provide an eleven bit pixel address, and also stores the full eleven bit pixel address. A timing and control state machine is connected to the input registers, the anode encoding logic circuits, and the output register for managing the overall operation of the circuit.

Study of spatial resolution of coordinate detectors based on Gas Electron Multipliers

NASA Astrophysics Data System (ADS)

Kudryavtsev, V. N.; Maltsev, T. V.; Shekhtman, L. I.

2017-02-01

Spatial resolution of GEM-based tracking detectors is determined in the simulation and measured in the experiments. The simulation includes GEANT4 implemented transport of high energy electrons with careful accounting of atomic relaxation processes including emission of fluorescent photons and Auger electrons and custom post-processing with accounting of diffusion, gas amplification fluctuations, distribution of signals on readout electrodes, electronics noise and particular algorithm of final coordinate calculation (center of gravity). The simulation demonstrates that the minimum of spatial resolution of about 10 μm can be achieved with a gas mixture of Ar -CO2 (75-25 %) at a strips pitch from 250 μm to 300 μm. At a larger pitch the resolution quickly degrades reaching 80-100 μm at a pitch of 460-500 μm. Spatial resolution of low-material triple-GEM detectors for the DEUTERON facility at the VEPP-3 storage ring is measured at the extracted beam facility of the VEPP-4 M collider. One-coordinate resolution of the DEUTERON detector is measured with electron beam of 500 MeV, 1 GeV and 3.5 GeV energies. The determined value of spatial resolution varies in the range from approximately 35 μm to 50 μm for orthogonal tracks in the experiments.

Improvement of the energy resolution of pixelated CdTe detectors for applications in 0νββ searches

NASA Astrophysics Data System (ADS)

Gleixner, T.; Anton, G.; Filipenko, M.; Seller, P.; Veale, M. C.; Wilson, M. D.; Zang, A.; Michel, T.

2015-07-01

Experiments trying to detect 0νββ are very challenging. Their requirements include a good energy resolution and a good detection efficiency. With current fine pixelated CdTe detectors there is a trade off between the energy resolution and the detection efficiency, which limits their performance. It will be shown with simulations that this problem can be mostly negated by analysing the cathode signal which increases the optimal sensor thickness. We will compare different types of fine pixelated CdTe detectors (Timepix, Dosepix, HEXITEC) from this point of view.

Characterisation methods for the hyperspectral sensor HySpex at DLR's calibration home base

NASA Astrophysics Data System (ADS)

Baumgartner, Andreas; Gege, Peter; Köhler, Claas; Lenhard, Karim; Schwarzmaier, Thomas

2012-09-01

The German Aerospace Center's (DLR) Remote Sensing Technology Institute (IMF) operates a laboratory for the characterisation of imaging spectrometers. Originally designed as Calibration Home Base (CHB) for the imaging spectrometer APEX, the laboratory can be used to characterise nearly every airborne hyperspectral system. Characterisation methods will be demonstrated exemplarily with HySpex, an airborne imaging spectrometer system from Norsk Elektro Optikks A/S (NEO). Consisting of two separate devices (VNIR-1600 and SWIR-320me) the setup covers the spectral range from 400 nm to 2500 nm. Both airborne sensors have been characterised at NEO. This includes measurement of spectral and spatial resolution and misregistration, polarisation sensitivity, signal to noise ratios and the radiometric response. The same parameters have been examined at the CHB and were used to validate the NEO measurements. Additionally, the line spread functions (LSF) in across and along track direction and the spectral response functions (SRF) for certain detector pixels were measured. The high degree of lab automation allows the determination of the SRFs and LSFs for a large amount of sampling points. Despite this, the measurement of these functions for every detector element would be too time-consuming as typical detectors have 105 elements. But with enough sampling points it is possible to interpolate the attributes of the remaining pixels. The knowledge of these properties for every detector element allows the quantification of spectral and spatial misregistration (smile and keystone) and a better calibration of airborne data. Further laboratory measurements are used to validate the models for the spectral and spatial properties of the imaging spectrometers. Compared to the future German spaceborne hyperspectral Imager EnMAP, the HySpex sensors have the same or higher spectral and spatial resolution. Therefore, airborne data will be used to prepare for and validate the spaceborne system's data.

Method and system for determining depth distribution of radiation-emitting material located in a source medium and radiation detector system for use therein

DOEpatents

Benke, Roland R.; Kearfott, Kimberlee J.; McGregor, Douglas S.

2003-03-04

A method, system and a radiation detector system for use therein are provided for determining the depth distribution of radiation-emitting material distributed in a source medium, such as a contaminated field, without the need to take samples, such as extensive soil samples, to determine the depth distribution. The system includes a portable detector assembly with an x-ray or gamma-ray detector having a detector axis for detecting the emitted radiation. The radiation may be naturally-emitted by the material, such as gamma-ray-emitting radionuclides, or emitted when the material is struck by other radiation. The assembly also includes a hollow collimator in which the detector is positioned. The collimator causes the emitted radiation to bend toward the detector as rays parallel to the detector axis of the detector. The collimator may be a hollow cylinder positioned so that its central axis is perpendicular to the upper surface of the large area source when positioned thereon. The collimator allows the detector to angularly sample the emitted radiation over many ranges of polar angles. This is done by forming the collimator as a single adjustable collimator or a set of collimator pieces having various possible configurations when connected together. In any one configuration, the collimator allows the detector to detect only the radiation emitted from a selected range of polar angles measured from the detector axis. Adjustment of the collimator or the detector therein enables the detector to detect radiation emitted from a different range of polar angles. The system further includes a signal processor for processing the signals from the detector wherein signals obtained from different ranges of polar angles are processed together to obtain a reconstruction of the radiation-emitting material as a function of depth, assuming, but not limited to, a spatially-uniform depth distribution of the material within each layer. The detector system includes detectors having different properties (sensitivity, energy resolution) which are combined so that excellent spectral information may be obtained along with good determinations of the radiation field as a function of position.

A sub-millimeter resolution PET detector module using a multi-pixel photon counter array

NASA Astrophysics Data System (ADS)

Song, Tae Yong; Wu, Heyu; Komarov, Sergey; Siegel, Stefan B.; Tai, Yuan-Chuan

2010-05-01

A PET block detector module using an array of sub-millimeter lutetium oxyorthosilicate (LSO) crystals read out by an array of surface-mount, semiconductor photosensors has been developed. The detector consists of a LSO array, a custom acrylic light guide, a 3 × 3 multi-pixel photon counter (MPPC) array (S10362-11-050P, Hamamatsu Photonics, Japan) and a readout board with a charge division resistor network. The LSO array consists of 100 crystals, each measuring 0.8 × 0.8 × 3 mm3 and arranged in 0.86 mm pitches. A Monte Carlo simulation was used to aid the design and fabrication of a custom light guide to control distribution of scintillation light over the surface of the MPPC array. The output signals of the nine MPPC are multiplexed by a charge division resistor network to generate four position-encoded analog outputs. Flood image, energy resolution and timing resolution measurements were performed using standard NIM electronics. The linearity of the detector response was investigated using gamma-ray sources of different energies. The 10 × 10 array of 0.8 mm LSO crystals was clearly resolved in the flood image. The average energy resolution and standard deviation were 20.0% full-width at half-maximum (FWHM) and ±5.0%, respectively, at 511 keV. The timing resolution of a single MPPC coupled to a LSO crystal was found to be 857 ps FWHM, and the value for the central region of detector module was 1182 ps FWHM when ±10% energy window was applied. The nonlinear response of a single MPPC when used to read out a single LSO was observed among the corner crystals of the proposed detector module. However, the central region of the detector module exhibits significantly less nonlinearity (6.5% for 511 keV). These results demonstrate that (1) a charge-sharing resistor network can effectively multiplex MPPC signals and reduce the number of output signals without significantly degrading the performance of a PET detector and (2) a custom light guide to permit light sharing among multiple MPPC and to diffuse and direct scintillation light can reduce the nonlinearity of the detector response within the limited dynamic range of a typical MPPC. As a result, the proposed PET detector module has the potential to be refined for use in high-resolution PET insert applications.

A sub-millimeter resolution PET detector module using a multi-pixel photon counter array.

PubMed

Song, Tae Yong; Wu, Heyu; Komarov, Sergey; Siegel, Stefan B; Tai, Yuan-Chuan

2010-05-07

A PET block detector module using an array of sub-millimeter lutetium oxyorthosilicate (LSO) crystals read out by an array of surface-mount, semiconductor photosensors has been developed. The detector consists of a LSO array, a custom acrylic light guide, a 3 x 3 multi-pixel photon counter (MPPC) array (S10362-11-050P, Hamamatsu Photonics, Japan) and a readout board with a charge division resistor network. The LSO array consists of 100 crystals, each measuring 0.8 x 0.8 x 3 mm(3) and arranged in 0.86 mm pitches. A Monte Carlo simulation was used to aid the design and fabrication of a custom light guide to control distribution of scintillation light over the surface of the MPPC array. The output signals of the nine MPPC are multiplexed by a charge division resistor network to generate four position-encoded analog outputs. Flood image, energy resolution and timing resolution measurements were performed using standard NIM electronics. The linearity of the detector response was investigated using gamma-ray sources of different energies. The 10 x 10 array of 0.8 mm LSO crystals was clearly resolved in the flood image. The average energy resolution and standard deviation were 20.0% full-width at half-maximum (FWHM) and +/-5.0%, respectively, at 511 keV. The timing resolution of a single MPPC coupled to a LSO crystal was found to be 857 ps FWHM, and the value for the central region of detector module was 1182 ps FWHM when +/-10% energy window was applied. The nonlinear response of a single MPPC when used to read out a single LSO was observed among the corner crystals of the proposed detector module. However, the central region of the detector module exhibits significantly less nonlinearity (6.5% for 511 keV). These results demonstrate that (1) a charge-sharing resistor network can effectively multiplex MPPC signals and reduce the number of output signals without significantly degrading the performance of a PET detector and (2) a custom light guide to permit light sharing among multiple MPPC and to diffuse and direct scintillation light can reduce the nonlinearity of the detector response within the limited dynamic range of a typical MPPC. As a result, the proposed PET detector module has the potential to be refined for use in high-resolution PET insert applications.

A sub-millimeter resolution PET detector module using a multi-pixel photon counter array

PubMed Central

Song, Tae Yong; Wu, Heyu; Komarov, Sergey; Siegel, Stefan B; Tai, Yuan-Chuan

2010-01-01

A PET block detector module using an array of sub-millimeter lutetium oxyorthosilicate (LSO) crystals read out by an array of surface-mount, semiconductor photosensors has been developed. The detector consists of a LSO array, a custom acrylic light guide, a 3 × 3 multi-pixel photon counter (MPPC) array (S10362-11-050P, Hamamatsu Photonics, Japan) and a readout board with a charge division resistor network. The LSO array consists of 100 crystals, each measuring 0.8 × 0.8 × 3 mm3 and arranged in 0.86 mm pitches. A Monte Carlo simulation was used to aid the design and fabrication of a custom light guide to control distribution of scintillation light over the surface of the MPPC array. The output signals of the nine MPPC are multiplexed by a charge division resistor network to generate four position-encoded analog outputs. Flood image, energy resolution and timing resolution measurements were performed using standard NIM electronics. The linearity of the detector response was investigated using gamma-ray sources of different energies. The 10 × 10 array of 0.8 mm LSO crystals was clearly resolved in the flood image. The average energy resolution and standard deviation were 20.0% full-width at half-maximum (FWHM) and ±5.0%, respectively, at 511 keV. The timing resolution of a single MPPC coupled to a LSO crystal was found to be 857 ps FWHM, and the value for the central region of detector module was 1182 ps FWHM when ±10% energy window was applied. The nonlinear response of a single MPPC when used to read out a single LSO was observed among the corner crystals of the proposed detector module. However, the central region of the detector module exhibits significantly less nonlinearity (6.5% for 511 keV). These results demonstrate that (1) a charge-sharing resistor network can effectively multiplex MPPC signals and reduce the number of output signals without significantly degrading the performance of a PET detector and (2) a custom light guide to permit light sharing among multiple MPPC and to diffuse and direct scintillation light can reduce the nonlinearity of the detector response within the limited dynamic range of a typical MPPC. As a result, the proposed PET detector module has the potential to be refined for use in high-resolution PET insert applications. PMID:20393236

Directional Sensitivity in Light-Mass Dark Matter Searches with Single-Electron-Resolution Ionization Detectors

NASA Astrophysics Data System (ADS)

Kadribasic, Fedja; Mirabolfathi, Nader; Nordlund, Kai; Sand, Andrea E.; Holmström, Eero; Djurabekova, Flyura

2018-03-01

We propose a method using solid state detectors with directional sensitivity to dark matter interactions to detect low-mass weakly interacting massive particles (WIMPs) originating from galactic sources. In spite of a large body of literature for high-mass WIMP detectors with directional sensitivity, no available technique exists to cover WIMPs in the mass range <1 GeV /c2 . We argue that single-electron-resolution semiconductor detectors allow for directional sensitivity once properly calibrated. We examine the commonly used semiconductor material response to these low-mass WIMP interactions.

Continuous on-line monitoring of left ventricular function with a new nonimaging detector:validation and clinical use in the evaluation of patients post angioplasty.

PubMed

Breisblatt, W M; Schulman, D S; Follansbee, W P

1991-06-01

A new miniaturized nonimaging radionuclide detector (Cardioscint, Oxford, England) was evaluated for the continuous on-line assessment of left ventricular function. This cesium iodide probe can be placed on the patient's chest and can be interfaced to an IBM compatible personal computer conveniently placed at the patient's bedside. This system can provide a beat-to-beat or gated determination of left ventricular ejection fraction and ST segment analysis. In 28 patients this miniaturized probe was correlated against a high resolution gamma camera study. Over a wide range of ejection fraction (31% to 76%) in patients with and without regional wall motion abnormalities, the correlation between the Cardioscint detector and the gamma camera was excellent (r = 0.94, SEE +/- 2.1). This detector system has high temporal (10 msec) resolution, and comparison of peak filling rate (PFR) and time to peak filling (TPFR) also showed close agreement with the gamma camera (PFR, r = 0.94, SEE +/- 0.17; TPFR, r = 0.92, SEE +/- 6.8). In 18 patients on bed rest the long-term stability of this system for measuring ejection fraction and ST segments was verified. During the monitoring period (108 +/- 28 minutes) only minor changes in ejection fraction occurred (coefficient of variation 0.035 +/- 0.016) and ST segment analysis showed no significant change from baseline. To determine whether continuous on-line measurement of ejection fraction would be useful after coronary angioplasty, 12 patients who had undergone a successful procedure were evaluated for 280 +/- 35 minutes with the Cardioscint system.(ABSTRACT TRUNCATED AT 250 WORDS)

A PET detector prototype based on digital SiPMs and GAGG scintillators.

PubMed

Schneider, Florian R; Shimazoe, Kenji; Somlai-Schweiger, Ian; Ziegler, Sibylle I

2015-02-21

Silicon Photomultipliers (SiPM) are interesting light sensors for Positron Emission Tomography (PET). The detector signal of analog SiPMs is the total charge of all fired cells. Energy and time information have to be determined with dedicated readout electronics. Philips Digital Photon Counting has developed a SiPM with added electronics on cell level delivering a digital value of the time stamp and number of fired cells. These so called Digital Photon Counters (DPC) are fully digital devices. In this study, the feasibility of using DPCs in combination with LYSO (Lutetium Yttrium Oxyorthosilicate) and GAGG (Gadolinium Aluminum Gallium Garnet) scintillators for PET is tested. Each DPC module has 64 channels with 3.2 × 3.8775 mm(2), comprising 3200 cells each. GAGG is a recently developed scintillator (Zeff = 54, 6.63 g cm(-3), 520 nm peak emission, 46 000 photons MeV(-1), 88 ns (92%) and 230 ns (8%) decay times, non-hygroscopic, chemically and mechanically stable). Individual crystals of 2 × 2 × 6 mm(3) were coupled onto each DPC pixel. LYSO coupled to the DPC results in a coincidence time resolution (CTR) of 171 ps FWHM and an energy resolution of 12.6% FWHM at 511 keV. Using GAGG, coincidence timing is 310 ps FWHM and energy resolution is 8.5% FWHM. A PET detector prototype with 2 DPCs equipped with a GAGG array matching the pixel size (3.2 × 3.8775 × 8 mm(3)) was assembled. To emulate a ring of 10 modules, objects are rotated in the field of view. CTR of the PET is 619 ps and energy resolution is 9.2% FWHM. The iterative MLEM reconstruction is based on system matrices calculated with an analytical detector response function model. A phantom with rods of different diameters filled with (18)F was used for tomographic tests.

A PET detector prototype based on digital SiPMs and GAGG scintillators

NASA Astrophysics Data System (ADS)

Schneider, Florian R.; Shimazoe, Kenji; Somlai-Schweiger, Ian; Ziegler, Sibylle I.

2015-02-01

Silicon Photomultipliers (SiPM) are interesting light sensors for Positron Emission Tomography (PET). The detector signal of analog SiPMs is the total charge of all fired cells. Energy and time information have to be determined with dedicated readout electronics. Philips Digital Photon Counting has developed a SiPM with added electronics on cell level delivering a digital value of the time stamp and number of fired cells. These so called Digital Photon Counters (DPC) are fully digital devices. In this study, the feasibility of using DPCs in combination with LYSO (Lutetium Yttrium Oxyorthosilicate) and GAGG (Gadolinium Aluminum Gallium Garnet) scintillators for PET is tested. Each DPC module has 64 channels with 3.2 × 3.8775 mm2, comprising 3200 cells each. GAGG is a recently developed scintillator (Zeff = 54, 6.63 g cm-3, 520 nm peak emission, 46 000 photons MeV-1, 88 ns (92%) and 230 ns (8%) decay times, non-hygroscopic, chemically and mechanically stable). Individual crystals of 2 × 2 × 6 mm3 were coupled onto each DPC pixel. LYSO coupled to the DPC results in a coincidence time resolution (CTR) of 171 ps FWHM and an energy resolution of 12.6% FWHM at 511 keV. Using GAGG, coincidence timing is 310 ps FWHM and energy resolution is 8.5% FWHM. A PET detector prototype with 2 DPCs equipped with a GAGG array matching the pixel size (3.2 × 3.8775 × 8 mm3) was assembled. To emulate a ring of 10 modules, objects are rotated in the field of view. CTR of the PET is 619 ps and energy resolution is 9.2% FWHM. The iterative MLEM reconstruction is based on system matrices calculated with an analytical detector response function model. A phantom with rods of different diameters filled with 18F was used for tomographic tests.

A micropixelated ion-imaging detector for mass resolution enhancement of a QMS instrument.

PubMed

Syed, Sarfaraz U A H; Eijkel, Gert B; Maher, Simon; Kistemaker, Piet; Taylor, Stephen; Heeren, Ron M A

2015-03-01

An in-vacuum position-sensitive micropixelated detector (Timepix) is used to investigate the time-dependent spatial distribution of different charge state (and hence different mass-to-charge (m/z)) ions exiting an electrospray ionization (ESI)-based quadrupole mass spectrometer (QMS) instrument. Ion images obtained from the Timepix detector provide a detailed insight into the positions of stable and unstable ions of the mass peak as they exit the QMS. With the help of image processing algorithms and by selecting areas on the ion images where more stable ions impact the detector, an improvement in mass resolution by a factor of 5 was obtained for certain operating conditions. Moreover, our experimental approach of mass resolution enhancement was confirmed by in-house-developed novel QMS instrument simulation software. Utilizing the imaging-based mass resolution enhancement approach, the software predicts instrument mass resolution of ∼1,0000 for a single-filter QMS instrument with a 210-mm long mass filter and a low operating frequency (880 kHz) of the radio frequency (RF) voltage.

A variable resolution x-ray detector for computed tomography: II. Imaging theory and performance.

PubMed

DiBianca, F A; Zou, P; Jordan, L M; Laughter, J S; Zeman, H D; Sebes, J

2000-08-01

A computed tomography (CT) imaging technique called variable resolution x-ray (VRX) detection provides variable image resolution ranging from that of clinical body scanning (1 cy/mm) to that of microscopy (100 cy/mm). In this paper, an experimental VRX CT scanner based on a rotating subject table and an angulated storage phosphor screen detector is described and tested. The measured projection resolution of the scanner is > or = 20 lp/mm. Using this scanner, 4.8-s CT scans are made of specimens of human extremities and of in vivo hamsters. In addition, the system's projected spatial resolution is calculated to exceed 100 cy/mm for a future on-line CT scanner incorporating smaller focal spots (0.1 mm) than those currently used and a 1008-channel VRX detector with 0.6-mm cell spacing.

Measurement of the Flux of Ultrahigh Energy Cosmic Rays from Monocular Observations by the High Resolution Fly's Eye Experiment

NASA Astrophysics Data System (ADS)

Abbasi, R. U.; Abu-Zayyad, T.; Amann, J. F.; Archbold, G.; Bellido, J. A.; Belov, K.; Belz, J. W.; Bergman, D. R.; Cao, Z.; Clay, R. W.; Cooper, M. D.; Dai, H.; Dawson, B. R.; Everett, A. A.; Fedorova, Yu. A.; Girard, J. H.; Gray, R. C.; Hanlon, W. F.; Hoffman, C. M.; Holzscheiter, M. H.; Hüntemeyer, P.; Jones, B. F.; Jui, C. C.; Kieda, D. B.; Kim, K.; Kirn, M. A.; Loh, E. C.; Manago, N.; Marek, L. J.; Martens, K.; Martin, G.; Matthews, J. A.; Matthews, J. N.; Meyer, J. R.; Moore, S. A.; Morrison, P.; Moosman, A. N.; Mumford, J. R.; Munro, M. W.; Painter, C. A.; Perera, L.; Reil, K.; Riehle, R.; Roberts, M.; Sarracino, J. S.; Sasaki, M.; Schnetzer, S. R.; Shen, P.; Simpson, K. M.; Sinnis, G.; Smith, J. D.; Sokolsky, P.; Song, C.; Springer, R. W.; Stokes, B. T.; Taylor, S. F.; Thomas, S. B.; Thompson, T. N.; Thomson, G. B.; Tupa, D.; Westerhoff, S.; Wiencke, L. R.; Vanderveen, T. D.; Zech, A.; Zhang, X.

2004-04-01

We have measured the cosmic ray spectrum above 1017.2 eV using the two air-fluorescence detectors of the High Resolution Fly's Eye observatory operating in monocular mode. We describe the detector, phototube, and atmospheric calibrations, as well as the analysis techniques for the two detectors. We fit the spectrum to a model consisting of galactic and extragalactic sources.

System geometry optimization for molecular breast tomosynthesis with focusing multi-pinhole collimators

NASA Astrophysics Data System (ADS)

van Roosmalen, Jarno; Beekman, Freek J.; Goorden, Marlies C.

2018-01-01

Imaging of 99mTc-labelled tracers is gaining popularity for detecting breast tumours. Recently, we proposed a novel design for molecular breast tomosynthesis (MBT) based on two sliding focusing multi-pinhole collimators that scan a modestly compressed breast. Simulation studies indicate that MBT has the potential to improve the tumour-to-background contrast-to-noise ratio significantly over state-of-the-art planar molecular breast imaging. The aim of the present paper is to optimize the collimator-detector geometry of MBT. Using analytical models, we first optimized sensitivity at different fixed system resolutions (ranging from 5 to 12 mm) by tuning the pinhole diameters and the distance between breast and detector for a whole series of automatically generated multi-pinhole designs. We evaluated both MBT with a conventional continuous crystal detector with 3.2 mm intrinsic resolution and with a pixelated detector with 1.6 mm pixels. Subsequently, full system simulations of a breast phantom containing several lesions were performed for the optimized geometry at each system resolution for both types of detector. From these simulations, we found that tumour-to-background contrast-to-noise ratio was highest for systems in the 7 mm-10 mm system resolution range over which it hardly varied. No significant differences between the two detector types were found.

Using synchrotron radiation angiography with a highly sensitive detector to identify impaired peripheral perfusion in rat pulmonary emphysema

PubMed Central

Ito, Hiromichi; Matsushita, Shonosuke; Hyodo, Kazuyuki; Sato, Yukio; Sakakibara, Yuzuru

2013-01-01

Owing to limitations in spatial resolution and sensitivity, it is difficult for conventional angiography to detect minute changes of perfusion in diffuse lung diseases, including pulmonary emphysema (PE). However, a high-gain avalanche rushing amorphous photoconductor (HARP) detector can give high sensitivity to synchrotron radiation (SR) angiography. SR angiography with a HARP detector provides high spatial resolution and sensitivity in addition to time resolution owing to its angiographic nature. The purpose of this study was to investigate whether this SR angiography with a HARP detector could evaluate altered microcirculation in PE. Two groups of rats were used: group PE and group C (control). Transvenous SR angiography with a HARP detector was performed and histopathological findings were compared. Peak density of contrast material in peripheral lung was lower in group PE than group C (p < 0.01). The slope of the linear regression line in scattering diagrams was also lower in group PE than C (p < 0.05). The correlation between the slope and extent of PE in histopathology showed significant negative correlation (p < 0.05, r = 0.61). SR angiography with a HARP detector made it possible to identify impaired microcirculation in PE by means of its high spatial resolution and sensitivity. PMID:23412496

3D track reconstruction capability of a silicon hybrid active pixel detector

NASA Astrophysics Data System (ADS)

Bergmann, Benedikt; Pichotka, Martin; Pospisil, Stanislav; Vycpalek, Jiri; Burian, Petr; Broulim, Pavel; Jakubek, Jan

2017-06-01

Timepix3 detectors are the latest generation of hybrid active pixel detectors of the Medipix/Timepix family. Such detectors consist of an active sensor layer which is connected to the readout ASIC (application specific integrated circuit), segmenting the detector into a square matrix of 256 × 256 pixels (pixel pitch 55 μm). Particles interacting in the active sensor material create charge carriers, which drift towards the pixelated electrode, where they are collected. In each pixel, the time of the interaction (time resolution 1.56 ns) and the amount of created charge carriers are measured. Such a device was employed in an experiment in a 120 GeV/c pion beam. It is demonstrated, how the drift time information can be used for "4D" particle tracking, with the three spatial dimensions and the energy losses along the particle trajectory (dE/dx). Since the coordinates in the detector plane are given by the pixelation ( x, y), the x- and y-resolution is determined by the pixel pitch (55 μm). A z-resolution of 50.4 μm could be achieved (for a 500 μm thick silicon sensor at 130 V bias), whereby the drift time model independent z-resolution was found to be 28.5 μm.

Characterization of a sub-assembly of 3D position sensitive cadmium zinc telluride detectors and electronics from a sub-millimeter resolution PET system.

PubMed

Abbaszadeh, Shiva; Gu, Yi; Reynolds, Paul D; Levin, Craig S

2016-09-21

Cadmium zinc telluride (CZT) offers key advantages for small animal positron emission tomography (PET), including high spatial and energy resolution and simple metal deposition for fabrication of very small pixel arrays. Previous studies have investigated the intrinsic spatial, energy, and timing resolution of an individual sub-millimeter resolution CZT detector. In this work we present the first characterization results of a system of these detectors. The 3D position sensitive dual-CZT detector module and readout electronics developed in our lab was scaled up to complete a significant portion of the final PET system. This sub-system was configured as two opposing detection panels containing a total of twelve [Formula: see text] mm monolithic CZT crystals for proof of concept. System-level characterization studies, including optimizing the trigger threshold of each channel's comparators, were performed. 68 Ge and 137 Cs radioactive isotopes were used to characterize the energy resolution of all 468 anode channels in the sub-system. The mean measured global 511 keV photopeak energy resolution over all anodes was found to be [Formula: see text]% FWHM after correction for photon interaction depth-dependent signal variation. The measured global time resolution was 37 ns FWHM, a parameter to be further optimized, and the intrinsic spatial resolution was 0.76 mm FWHM.

Expanding the detection efficiency of silicon drift detectors

NASA Astrophysics Data System (ADS)

Schlosser, D. M.; Lechner, P.; Lutz, G.; Niculae, A.; Soltau, H.; Strüder, L.; Eckhardt, R.; Hermenau, K.; Schaller, G.; Schopper, F.; Jaritschin, O.; Liebel, A.; Simsek, A.; Fiorini, C.; Longoni, A.

2010-12-01

To expand the detection efficiency Silicon Drift Detectors (SDDs) with various customized radiation entrance windows, optimized detector areas and geometries have been developed. Optimum values for energy resolution, peak to background ratio (P/B) and high count rate capability support the development. Detailed results on sensors optimized for light element detection down to Boron or even lower will be reported. New developments for detecting medium and high X-ray energies by increasing the effective detector thickness will be presented. Gamma-ray detectors consisting of a SDD coupled to scintillators like CsI(Tl) and LaBr 3(Ce) have been examined. Results of the energy resolution for the 137Cs 662 keV line and the light yield (LY) of such detector systems will be reported.

SU-C-201-02: Quantitative Small-Animal SPECT Without Scatter Correction Using High-Purity Germanium Detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gearhart, A; Peterson, T; Johnson, L

2015-06-15

Purpose: To evaluate the impact of the exceptional energy resolution of germanium detectors for preclinical SPECT in comparison to conventional detectors. Methods: A cylindrical water phantom was created in GATE with a spherical Tc-99m source in the center. Sixty-four projections over 360 degrees using a pinhole collimator were simulated. The same phantom was simulated using air instead of water to establish the true reconstructed voxel intensity without attenuation. Attenuation correction based on the Chang method was performed on MLEM reconstructed images from the water phantom to determine a quantitative measure of the effectiveness of the attenuation correction. Similarly, a NEMAmore » phantom was simulated, and the effectiveness of the attenuation correction was evaluated. Both simulations were carried out using both NaI detectors with an energy resolution of 10% FWHM and Ge detectors with an energy resolution of 1%. Results: Analysis shows that attenuation correction without scatter correction using germanium detectors can reconstruct a small spherical source to within 3.5%. Scatter analysis showed that for standard sized objects in a preclinical scanner, a NaI detector has a scatter-to-primary ratio between 7% and 12.5% compared to between 0.8% and 1.5% for a Ge detector. Preliminary results from line profiles through the NEMA phantom suggest that applying attenuation correction without scatter correction provides acceptable results for the Ge detectors but overestimates the phantom activity using NaI detectors. Due to the decreased scatter, we believe that the spillover ratio for the air and water cylinders in the NEMA phantom will be lower using germanium detectors compared to NaI detectors. Conclusion: This work indicates that the superior energy resolution of germanium detectors allows for less scattered photons to be included within the energy window compared to traditional SPECT detectors. This may allow for quantitative SPECT without implementing scatter correction, reducing uncertainties introduced by scatter correction algorithms. Funding provided by NIH/NIBIB grant R01EB013677; Todd Peterson, Ph.D., has had a research contract with PHDs Co., Knoxville, TN.« less

Throughput of diffraction-limited field optics systems for infrared and millimetric telescopes

NASA Technical Reports Server (NTRS)

Hildebrand, R. H.; Winston, R.

1982-01-01

Telescopes for submillimeter wavelengths have point spread functions some millimeters or centimeters in diameter, but the detectors may be only fractions of a millimeter in size. Thus a field aperture and collecting optics are needed. Optimizing the aperture by a calculation of the effects of diffraction on signal and resolution as a function of size of the collecting aperture is shown. Calculations are compared to experimental results from observations of Mars at submillimeter wavelengths.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blaut, Arkadiusz

We present the results of the estimation of parameters with LISA for nearly monochromatic gravitational waves in the low and high frequency regimes for the time-delay interferometry response. Angular resolution of the detector and the estimation errors of the signal's parameters in the high frequency regimes are calculated as functions of the position in the sky and as functions of the frequency. For the long-wavelength domain we give compact formulas for the estimation errors valid on a wide range of the parameter space.

Pulsed-neutron imaging by a high-speed camera and center-of-gravity processing

NASA Astrophysics Data System (ADS)

Mochiki, K.; Uragaki, T.; Koide, J.; Kushima, Y.; Kawarabayashi, J.; Taketani, A.; Otake, Y.; Matsumoto, Y.; Su, Y.; Hiroi, K.; Shinohara, T.; Kai, T.

2018-01-01

Pulsed-neutron imaging is attractive technique in the research fields of energy-resolved neutron radiography and RANS (RIKEN) and RADEN (J-PARC/JAEA) are small and large accelerator-driven pulsed-neutron facilities for its imaging, respectively. To overcome the insuficient spatial resolution of the conunting type imaging detectors like μ NID, nGEM and pixelated detectors, camera detectors combined with a neutron color image intensifier were investigated. At RANS center-of-gravity technique was applied to spots image obtained by a CCD camera and the technique was confirmed to be effective for improving spatial resolution. At RADEN a high-frame-rate CMOS camera was used and super resolution technique was applied and it was recognized that the spatial resolution was futhermore improved.

Results from a 64-pixel PIN-diode detector system for low-energy beta-electrons

NASA Astrophysics Data System (ADS)

Wuestling, Sascha; Fraenkle, F.; Habermehl, F.; Renschler, P.; Steidl, M.

2010-12-01

The KATRIN neutrino mass experiment is based on a precise energy measurement (Δ E/ E=5×10 -5) of electrons emerging from tritium beta decay ( Emax=18.6 keV). This is done by a large electrostatic retarding spectrometer (MAC-E Filter), which is followed by an electron detector. Key requirements for this detector are a large sensitive area (˜80 cm 2), a certain energy resolution (Δ E=600 eV @ 18.6 keV) but also a certain spatial resolution (˜3 mm), which leads to a multi-pixel design. As a tentative design on the way to the final detector, but also for operational service on the so-called pre-spectrometer experiment, a detector system with a reduced size (16 cm 2) and a reduced pixel number (64), making use of a monolithic segmented silicon PIN diode, was designed and built. While the design and very first measurements have been presented in Wuestling et al. [6], this publication shows the operational performance of the detector system. The robust concept of the electronics allowed adaptation to mechanically different experimental setups. The spacial resolution of the detector system proved to be essential in examining Penning trap induced background and other effects in the pre-spectrometer experiment. The detector performance test runs include energy resolution and calibration, background rates, correlation between pixels (crosstalk), spatially resolved rate analysis, and a dead-layer measurement [7]. The detector allows for background searches with a sensitivity as low as 1.3×10 -3 cps/cm 2 in the energy range of 20 keV. This allows the pre-spectrometer to be characterized with e-gun illumination with a signal to background ratio of better than 10 5 and the search for ultra low Penning discharge emissions.

Theoretical performance analysis for CMOS based high resolution detectors.

PubMed

Jain, Amit; Bednarek, Daniel R; Rudin, Stephen

2013-03-06

High resolution imaging capabilities are essential for accurately guiding successful endovascular interventional procedures. Present x-ray imaging detectors are not always adequate due to their inherent limitations. The newly-developed high-resolution micro-angiographic fluoroscope (MAF-CCD) detector has demonstrated excellent clinical image quality; however, further improvement in performance and physical design may be possible using CMOS sensors. We have thus calculated the theoretical performance of two proposed CMOS detectors which may be used as a successor to the MAF. The proposed detectors have a 300 μm thick HL-type CsI phosphor, a 50 μm-pixel CMOS sensor with and without a variable gain light image intensifier (LII), and are designated MAF-CMOS-LII and MAF-CMOS, respectively. For the performance evaluation, linear cascade modeling was used. The detector imaging chains were divided into individual stages characterized by one of the basic processes (quantum gain, binomial selection, stochastic and deterministic blurring, additive noise). Ranges of readout noise and exposure were used to calculate the detectors' MTF and DQE. The MAF-CMOS showed slightly better MTF than the MAF-CMOS-LII, but the MAF-CMOS-LII showed far better DQE, especially for lower exposures. The proposed detectors can have improved MTF and DQE compared with the present high resolution MAF detector. The performance of the MAF-CMOS is excellent for the angiography exposure range; however it is limited at fluoroscopic levels due to additive instrumentation noise. The MAF-CMOS-LII, having the advantage of the variable LII gain, can overcome the noise limitation and hence may perform exceptionally for the full range of required exposures; however, it is more complex and hence more expensive.

A high-throughput, multi-channel photon-counting detector with picosecond timing

NASA Astrophysics Data System (ADS)

Lapington, J. S.; Fraser, G. W.; Miller, G. M.; Ashton, T. J. R.; Jarron, P.; Despeisse, M.; Powolny, F.; Howorth, J.; Milnes, J.

2009-06-01

High-throughput photon counting with high time resolution is a niche application area where vacuum tubes can still outperform solid-state devices. Applications in the life sciences utilizing time-resolved spectroscopies, particularly in the growing field of proteomics, will benefit greatly from performance enhancements in event timing and detector throughput. The HiContent project is a collaboration between the University of Leicester Space Research Centre, the Microelectronics Group at CERN, Photek Ltd., and end-users at the Gray Cancer Institute and the University of Manchester. The goal is to develop a detector system specifically designed for optical proteomics, capable of high content (multi-parametric) analysis at high throughput. The HiContent detector system is being developed to exploit this niche market. It combines multi-channel, high time resolution photon counting in a single miniaturized detector system with integrated electronics. The combination of enabling technologies; small pore microchannel plate devices with very high time resolution, and high-speed multi-channel ASIC electronics developed for the LHC at CERN, provides the necessary building blocks for a high-throughput detector system with up to 1024 parallel counting channels and 20 ps time resolution. We describe the detector and electronic design, discuss the current status of the HiContent project and present the results from a 64-channel prototype system. In the absence of an operational detector, we present measurements of the electronics performance using a pulse generator to simulate detector events. Event timing results from the NINO high-speed front-end ASIC captured using a fast digital oscilloscope are compared with data taken with the proposed electronic configuration which uses the multi-channel HPTDC timing ASIC.

Use of high-granularity CdZnTe pixelated detectors to correct response non-uniformities caused by defects in crystals

DOE PAGES

Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.; ...

2015-09-06

Following our successful demonstration of the position-sensitive virtual Frisch-grid detectors, we investigated the feasibility of using high-granularity position sensing to correct response non-uniformities caused by the crystal defects in CdZnTe (CZT) pixelated detectors. The development of high-granularity detectors able to correct response non-uniformities on a scale comparable to the size of electron clouds opens the opportunity of using unselected off-the-shelf CZT material, whilst still assuring high spectral resolution for the majority of the detectors fabricated from an ingot. Here, we present the results from testing 3D position-sensitive 15×15×10 mm 3 pixelated detectors, fabricated with conventional pixel patterns with progressively smallermore » pixel sizes: 1.4, 0.8, and 0.5 mm. We employed the readout system based on the H3D front-end multi-channel ASIC developed by BNL's Instrumentation Division in collaboration with the University of Michigan. We use the sharing of electron clouds among several adjacent pixels to measure locations of interaction points with sub-pixel resolution. By using the detectors with small-pixel sizes and a high probability of the charge-sharing events, we were able to improve their spectral resolutions in comparison to the baseline levels, measured for the 1.4-mm pixel size detectors with small fractions of charge-sharing events. These results demonstrate that further enhancement of the performance of CZT pixelated detectors and reduction of costs are possible by using high spatial-resolution position information of interaction points to correct the small-scale response non-uniformities caused by crystal defects present in most devices.« less

Amorphous selenium direct detection CMOS digital x-ray imager with 25 micron pixel pitch

NASA Astrophysics Data System (ADS)

Scott, Christopher C.; Abbaszadeh, Shiva; Ghanbarzadeh, Sina; Allan, Gary; Farrier, Michael; Cunningham, Ian A.; Karim, Karim S.

2014-03-01

We have developed a high resolution amorphous selenium (a-Se) direct detection imager using a large-area compatible back-end fabrication process on top of a CMOS active pixel sensor having 25 micron pixel pitch. Integration of a-Se with CMOS technology requires overcoming CMOS/a-Se interfacial strain, which initiates nucleation of crystalline selenium and results in high detector dark currents. A CMOS-compatible polyimide buffer layer was used to planarize the backplane and provide a low stress and thermally stable surface for a-Se. The buffer layer inhibits crystallization and provides detector stability that is not only a performance factor but also critical for favorable long term cost-benefit considerations in the application of CMOS digital x-ray imagers in medical practice. The detector structure is comprised of a polyimide (PI) buffer layer, the a-Se layer, and a gold (Au) top electrode. The PI layer is applied by spin-coating and is patterned using dry etching to open the backplane bond pads for wire bonding. Thermal evaporation is used to deposit the a-Se and Au layers, and the detector is operated in hole collection mode (i.e. a positive bias on the Au top electrode). High resolution a-Se diagnostic systems typically use 70 to 100 μm pixel pitch and have a pre-sampling modulation transfer function (MTF) that is significantly limited by the pixel aperture. Our results confirm that, for a densely integrated 25 μm pixel pitch CMOS array, the MTF approaches the fundamental material limit, i.e. where the MTF begins to be limited by the a-Se material properties and not the pixel aperture. Preliminary images demonstrating high spatial resolution have been obtained from a frst prototype imager.

A Lower-Cost High-Resolution LYSO Detector Development for Positron Emission Mammography (PEM)

PubMed Central

Ramirez, Rocio A.; Zhang, Yuxuan; Liu, Shitao; Li, Hongdi; Baghaei, Hossain; An, Shaohui; Wang, Chao; Jan, Meei-Ling; Wong, Wai-Hoi

2010-01-01

In photomultiplier-quadrant-sharing (PQS) geometry for positron emission tomography applications, each PMT is shared by four blocks and each detector block is optically coupled to four round PMTs. Although this design reduces the cost of high-resolution PET systems, when the camera consists of detector panels that are made up of square blocks, half of the PMT’s sensitive window remains unused at the detector panel edge. Our goal was to develop a LYSO detector panel which minimizes the unused portion of the PMTs for a low-cost, high-resolution, and high-sensitivity positron emission mammography (PEM) camera. We modified the PQS design by using elongated blocks at panel edges and square blocks in the inner area. For elongated blocks, symmetric and asymmetrical reflector patterns were developed and PQS and PMT-half-sharing (PHS) arrangements were implemented in order to obtain a suitable decoding. The packing fraction was 96.3% for asymmetric block and 95.5% for symmetric block. Both of the blocks have excellent decoding capability with all crystals clearly identified, 156 for asymmetric and 144 for symmetric and peak-to-valley ratio of 3.0 and 2.3 respectively. The average energy resolution was 14.2% for the asymmetric block and 13.1% for the symmetric block. Using a modified PQS geometry and asymmetric block design, we reduced the unused PMT region at detector panel edges, thereby increased the field-of-view and the overall detection sensitivity and minimized the undetected breast region near the chest wall. This detector design and using regular round PMT allowed building a lower-cost, high-resolution and high-sensitivity PEM camera. PMID:20485510

Thallium Bromide as an Alternative Material for Room-Temperature Gamma-Ray Spectroscopy and Imaging

NASA Astrophysics Data System (ADS)

Koehler, William

Thallium bromide is an attractive material for room-temperature gamma-ray spectroscopy and imaging because of its high atomic number (Tl: 81, Br: 35), high density (7.56 g/cm3), and a wide bandgap (2.68 eV). In this work, 5 mm thick TlBr detectors achieved 0.94% FWHM at 662 keV for all single-pixel events and 0.72% FWHM at 662 keV from the best pixel and depth using three-dimensional position sensing technology. However, these results were limited to stable operation at -20°C. After days to months of room-temperature operation, ionic conduction caused these devices to fail. Depth-dependent signal analysis was used to isolate room-temperature degradation effects to within 0.5 mm of the anode surface. This was verified by refabricating the detectors after complete failure at room temperature; after refabrication, similar performance and functionality was recovered. As part of this work, the improvement in electron drift velocity and energy resolution during conditioning at -20°C was quantified. A new method was developed to measure the impurity concentration without changing the gamma ray measurement setup. The new method was used to show that detector conditioning was likely the result of charged impurities drifting out of the active volume. This space charge reduction then caused a more stable and uniform electric field. Additionally, new algorithms were developed to remove hole contributions in high-hole-mobility detectors to improve depth reconstruction. These algorithms improved the depth reconstruction (accuracy) without degrading the depth uncertainty (precision). Finally, spectroscopic and imaging performance of new 11 x 11 pixelated-anode TlBr detectors was characterized. The larger detectors were used to show that energy resolution can be improved by identifying photopeak events from their Tl characteristic x-rays.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.

Following our successful demonstration of the position-sensitive virtual Frisch-grid detectors, we investigated the feasibility of using high-granularity position sensing to correct response non-uniformities caused by the crystal defects in CdZnTe (CZT) pixelated detectors. The development of high-granularity detectors able to correct response non-uniformities on a scale comparable to the size of electron clouds opens the opportunity of using unselected off-the-shelf CZT material, whilst still assuring high spectral resolution for the majority of the detectors fabricated from an ingot. Here, we present the results from testing 3D position-sensitive 15×15×10 mm 3 pixelated detectors, fabricated with conventional pixel patterns with progressively smallermore » pixel sizes: 1.4, 0.8, and 0.5 mm. We employed the readout system based on the H3D front-end multi-channel ASIC developed by BNL's Instrumentation Division in collaboration with the University of Michigan. We use the sharing of electron clouds among several adjacent pixels to measure locations of interaction points with sub-pixel resolution. By using the detectors with small-pixel sizes and a high probability of the charge-sharing events, we were able to improve their spectral resolutions in comparison to the baseline levels, measured for the 1.4-mm pixel size detectors with small fractions of charge-sharing events. These results demonstrate that further enhancement of the performance of CZT pixelated detectors and reduction of costs are possible by using high spatial-resolution position information of interaction points to correct the small-scale response non-uniformities caused by crystal defects present in most devices.« less

Investigation of the limitations of the highly pixilated CdZnTe detector for PET applications

PubMed Central

Komarov, Sergey; Yin, Yongzhi; Wu, Heyu; Wen, Jie; Krawczynski, Henric; Meng, Ling-Jian; Tai, Yuan-Chuan

2016-01-01

We are investigating the feasibility of a high resolution positron emission tomography (PET) insert device based on the CdZnTe detector with 350 μm anode pixel pitch to be integrated into a conventional animal PET scanner to improve its image resolution. In this paper, we have used a simplified version of the multi pixel CdZnTe planar detector, 5 mm thick with 9 anode pixels only. This simplified 9 anode pixel structure makes it possible to carry out experiments without a complete application-specific integrated circuits readout system that is still under development. Special attention was paid to the double pixel (or charge sharing) detections. The following characteristics were obtained in experiment: energy resolution full-width-at-half-maximum (FWHM) is 7% for single pixel and 9% for double pixel photoelectric detections of 511 keV gammas; timing resolution (FWHM) from the anode signals is 30 ns for single pixel and 35 ns for double pixel detections (for photoelectric interactions only the corresponding values are 20 and 25 ns); position resolution is 350 μm in x,y-plane and ~0.4 mm in depth-of-interaction. The experimental measurements were accompanied by Monte Carlo (MC) simulations to find a limitation imposed by spatial charge distribution. Results from MC simulations suggest the limitation of the intrinsic spatial resolution of the CdZnTe detector for 511 keV photoelectric interactions is 170 μm. The interpixel interpolation cannot recover the resolution beyond the limit mentioned above for photoelectric interactions. However, it is possible to achieve higher spatial resolution using interpolation for Compton scattered events. Energy and timing resolution of the proposed 350 μm anode pixel pitch detector is no better than 0.6% FWHM at 511 keV, and 2 ns FWHM, respectively. These MC results should be used as a guide to understand the performance limits of the pixelated CdZnTe detector due to the underlying detection processes, with the understanding of the inherent limitations of MC methods. PMID:23079763

Investigation of the limitations of the highly pixilated CdZnTe detector for PET applications.

PubMed

Komarov, Sergey; Yin, Yongzhi; Wu, Heyu; Wen, Jie; Krawczynski, Henric; Meng, Ling-Jian; Tai, Yuan-Chuan

2012-11-21

We are investigating the feasibility of a high resolution positron emission tomography (PET) insert device based on the CdZnTe detector with 350 µm anode pixel pitch to be integrated into a conventional animal PET scanner to improve its image resolution. In this paper, we have used a simplified version of the multi pixel CdZnTe planar detector, 5 mm thick with 9 anode pixels only. This simplified 9 anode pixel structure makes it possible to carry out experiments without a complete application-specific integrated circuits readout system that is still under development. Special attention was paid to the double pixel (or charge sharing) detections. The following characteristics were obtained in experiment: energy resolution full-width-at-half-maximum (FWHM) is 7% for single pixel and 9% for double pixel photoelectric detections of 511 keV gammas; timing resolution (FWHM) from the anode signals is 30 ns for single pixel and 35 ns for double pixel detections (for photoelectric interactions only the corresponding values are 20 and 25 ns); position resolution is 350 µm in x,y-plane and ∼0.4 mm in depth-of-interaction. The experimental measurements were accompanied by Monte Carlo (MC) simulations to find a limitation imposed by spatial charge distribution. Results from MC simulations suggest the limitation of the intrinsic spatial resolution of the CdZnTe detector for 511 keV photoelectric interactions is 170 µm. The interpixel interpolation cannot recover the resolution beyond the limit mentioned above for photoelectric interactions. However, it is possible to achieve higher spatial resolution using interpolation for Compton scattered events. Energy and timing resolution of the proposed 350 µm anode pixel pitch detector is no better than 0.6% FWHM at 511 keV, and 2 ns FWHM, respectively. These MC results should be used as a guide to understand the performance limits of the pixelated CdZnTe detector due to the underlying detection processes, with the understanding of the inherent limitations of MC methods.

A review of the developments of radioxenon detectors for nuclear explosion monitoring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sivels, Ciara B.; McIntyre, Justin I.; Bowyer, Theodore W.

Developments in radioxenon monitoring since the implementation of the International Monitoring System are reviewed with emphasis on the most current technologies to improve detector sensitivity and resolution. The nuclear detectors reviewed include combinations of plastic and NaI(Tl) detectors, high purity germanium detectors, silicon detectors, and phoswich detectors. The minimum detectable activity and calibration methods for the various detectors are also discussed.

Relationship between noise, dose, and pitch in cardiac multi-detector row CT.

PubMed

Primak, Andrew N; McCollough, Cynthia H; Bruesewitz, Michael R; Zhang, Jie; Fletcher, Joel G

2006-01-01

In spiral computed tomography (CT), dose is always inversely proportional to pitch. However, the relationship between noise and pitch (and hence noise and dose) depends on the scanner type (single vs multi-detector row) and reconstruction mode (cardiac vs noncardiac). In single detector row spiral CT, noise is independent of pitch. Conversely, in noncardiac multi-detector row CT, noise depends on pitch because the spiral interpolation algorithm makes use of redundant data from different detector rows to decrease noise for pitch values less than 1 (and increase noise for pitch values > 1). However, in cardiac spiral CT, redundant data cannot be used because such data averaging would degrade the temporal resolution. Therefore, the behavior of noise versus pitch returns to the single detector row paradigm, with noise being independent of pitch. Consequently, since faster rotation times require lower pitch values in cardiac multi-detector row CT, dose is increased without a commensurate decrease in noise. Thus, the use of faster rotation times will improve temporal resolution, not alter noise, and increase dose. For a particular application, the higher dose resulting from faster rotation speeds should be justified by the clinical benefits of the improved temporal resolution. RSNA, 2006

Study of sub-pixel position resolution with time-correlated transient signals in 3D pixelated CdZnTe detectors with varying pixel sizes

NASA Astrophysics Data System (ADS)

Ocampo Giraldo, L.; Bolotnikov, A. E.; Camarda, G. S.; De Geronimo, G.; Fried, J.; Gul, R.; Hodges, D.; Hossain, A.; Ünlü, K.; Vernon, E.; Yang, G.; James, R. B.

2018-03-01

We evaluated the sub-pixel position resolution achievable in large-volume CdZnTe pixelated detectors with conventional pixel patterns and for several different pixel sizes: 2.8 mm, 1.72 mm, 1.4 mm and 0.8 mm. Achieving position resolution below the physical dimensions of pixels (sub-pixel resolution) is a practical path for making high-granularity position-sensitive detectors, <100 μm, using a limited number of pixels dictated by the mechanical constraints and multi-channel readout electronics. High position sensitivity is important for improving the imaging capability of CZT gamma cameras. It also allows for making more accurate corrections of response non-uniformities caused by crystal defects, thus enabling use of standard-grade (unselected) and less expensive CZT crystals for producing large-volume position-sensitive CZT detectors feasible for many practical applications. We analyzed the digitized charge signals from a representative 9 pixels and the cathode, generated using a pulsed-laser light beam focused down to 10 μm (650 nm) to scan over a selected 3 × 3 pixel area. We applied our digital pulse processing technique to the time-correlated signals captured from adjacent pixels to achieve and evaluate the capability for sub-pixel position resolution. As an example, we also demonstrated an application of 3D corrections to improve the energy resolution and positional information of the events for the tested detectors.

Study of sub-pixel position resolution with time-correlated transient signals in 3D pixelated CdZnTe detectors with varying pixel sizes

DOE PAGES

Giraldo, L. Ocampo; Bolotnikov, A. E.; Camarda, G. S.; ...

2017-12-18

Here, we evaluated the sub-pixel position resolution achievable in large-volume CdZnTe pixelated detectors with conventional pixel patterns and for several different pixel sizes: 2.8 mm, 1.72 mm, 1.4 mm and 0.8 mm. Achieving position resolution below the physical dimensions of pixels (sub-pixel resolution) is a practical path for making high-granularity position-sensitive detectors, <100 μμm, using a limited number of pixels dictated by the mechanical constraints and multi-channel readout electronics. High position sensitivity is important for improving the imaging capability of CZT gamma cameras. It also allows for making more accurate corrections of response non-uniformities caused by crystal defects, thus enablingmore » use of standard-grade (unselected) and less expensive CZT crystals for producing large-volume position-sensitive CZT detectors feasible for many practical applications. We analyzed the digitized charge signals from a representative 9 pixels and the cathode, generated using a pulsed-laser light beam focused down to 10 m (650 nm) to scan over a selected 3×3 pixel area. We applied our digital pulse processing technique to the time-correlated signals captured from adjacent pixels to achieve and evaluate the capability for sub-pixel position resolution. As an example, we also demonstrated an application of 3D corrections to improve the energy resolution and positional information of the events for the tested detectors.« less

Study of sub-pixel position resolution with time-correlated transient signals in 3D pixelated CdZnTe detectors with varying pixel sizes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giraldo, L. Ocampo; Bolotnikov, A. E.; Camarda, G. S.

Here, we evaluated the sub-pixel position resolution achievable in large-volume CdZnTe pixelated detectors with conventional pixel patterns and for several different pixel sizes: 2.8 mm, 1.72 mm, 1.4 mm and 0.8 mm. Achieving position resolution below the physical dimensions of pixels (sub-pixel resolution) is a practical path for making high-granularity position-sensitive detectors, <100 μμm, using a limited number of pixels dictated by the mechanical constraints and multi-channel readout electronics. High position sensitivity is important for improving the imaging capability of CZT gamma cameras. It also allows for making more accurate corrections of response non-uniformities caused by crystal defects, thus enablingmore » use of standard-grade (unselected) and less expensive CZT crystals for producing large-volume position-sensitive CZT detectors feasible for many practical applications. We analyzed the digitized charge signals from a representative 9 pixels and the cathode, generated using a pulsed-laser light beam focused down to 10 m (650 nm) to scan over a selected 3×3 pixel area. We applied our digital pulse processing technique to the time-correlated signals captured from adjacent pixels to achieve and evaluate the capability for sub-pixel position resolution. As an example, we also demonstrated an application of 3D corrections to improve the energy resolution and positional information of the events for the tested detectors.« less

WE-G-204-03: Photon-Counting Hexagonal Pixel Array CdTe Detector: Optimal Resampling to Square Pixels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shrestha, S; Vedantham, S; Karellas, A

Purpose: Detectors with hexagonal pixels require resampling to square pixels for distortion-free display of acquired images. In this work, the presampling modulation transfer function (MTF) of a hexagonal pixel array photon-counting CdTe detector for region-of-interest fluoroscopy was measured and the optimal square pixel size for resampling was determined. Methods: A 0.65mm thick CdTe Schottky sensor capable of concurrently acquiring up to 3 energy-windowed images was operated in a single energy-window mode to include ≥10 KeV photons. The detector had hexagonal pixels with apothem of 30 microns resulting in pixel spacing of 60 and 51.96 microns along the two orthogonal directions.more » Images of a tungsten edge test device acquired under IEC RQA5 conditions were double Hough transformed to identify the edge and numerically differentiated. The presampling MTF was determined from the finely sampled line spread function that accounted for the hexagonal sampling. The optimal square pixel size was determined in two ways; the square pixel size for which the aperture function evaluated at the Nyquist frequencies along the two orthogonal directions matched that from the hexagonal pixel aperture functions, and the square pixel size for which the mean absolute difference between the square and hexagonal aperture functions was minimized over all frequencies up to the Nyquist limit. Results: Evaluation of the aperture functions over the entire frequency range resulted in square pixel size of 53 microns with less than 2% difference from the hexagonal pixel. Evaluation of the aperture functions at Nyquist frequencies alone resulted in 54 microns square pixels. For the photon-counting CdTe detector and after resampling to 53 microns square pixels using quadratic interpolation, the presampling MTF at Nyquist frequency of 9.434 cycles/mm along the two directions were 0.501 and 0.507. Conclusion: Hexagonal pixel array photon-counting CdTe detector after resampling to square pixels provides high-resolution imaging suitable for fluoroscopy.« less

Detection of grapes in natural environment using HOG features in low resolution images

NASA Astrophysics Data System (ADS)

Škrabánek, Pavel; Majerík, Filip

2017-07-01

Detection of grapes in real-life images has importance in various viticulture applications. A grape detector based on an SVM classifier, in combination with a HOG descriptor, has proven to be very efficient in detection of white varieties in high-resolution images. Nevertheless, the high time complexity of such utilization was not suitable for its real-time applications, even when a detector of a simplified structure was used. Thus, we examined possibilities of the simplified version application on images of lower resolutions. For this purpose, we designed a method aimed at search for a detector’s setting which gives the best time complexity vs. performance ratio. In order to provide precise evaluation results, we formed new extended datasets. We discovered that even applied on low-resolution images, the simplified detector, with an appropriate setting of all tuneable parameters, was competitive with other state of the art solutions. We concluded that the detector is qualified for real-time detection of grapes in real-life images.

Modeling and simulation of Positron Emission Mammography (PEM) based on double-sided CdTe strip detectors

NASA Astrophysics Data System (ADS)

Ozsahin, I.; Unlu, M. Z.

2014-03-01

Breast cancer is the most common leading cause of cancer death among women. Positron Emission Tomography (PET) Mammography, also known as Positron Emission Mammography (PEM), is a method for imaging primary breast cancer. Over the past few years, PEMs based on scintillation crystals dramatically increased their importance in diagnosis and treatment of early stage breast cancer. However, these detectors have significant limitations like poor energy resolution resulting with false-negative result (missed cancer), and false-positive result which leads to suspecting cancer and suggests an unnecessary biopsy. In this work, a PEM scanner based on CdTe strip detectors is simulated via the Monte Carlo method and evaluated in terms of its spatial resolution, sensitivity, and image quality. The spatial resolution is found to be ~ 1 mm in all three directions. The results also show that CdTe strip detectors based PEM scanner can produce high resolution images for early diagnosis of breast cancer.

Development of a Germanium Small-Animal SPECT System

NASA Astrophysics Data System (ADS)

Johnson, Lindsay C.; Ovchinnikov, Oleg; Shokouhi, Sepideh; Peterson, Todd E.

2015-10-01

Advances in fabrication techniques, electronics, and mechanical cooling systems have given rise to germanium detectors suitable for biomedical imaging. We are developing a small-animal SPECT system that uses a double-sided Ge strip detector. The detector's excellent energy resolution may help to reduce scatter and simplify processing of multi-isotope imaging, while its ability to measure depth of interaction has the potential to mitigate parallax error in pinhole imaging. The detector's energy resolution is <; 1% FWHM at 140 keV and its spatial resolution is approximately 1.5 mm FWHM. The prototype system described has a single-pinhole collimator with a 1-mm diameter and a 70-degree opening angle with a focal length variable between 4.5 and 9 cm. Phantom images from the gantry-mounted system are presented, including the NEMA NU-2008 phantom and a hot-rod phantom. Additionally, the benefit of energy resolution is demonstrated by imaging a dual-isotope phantom with 99mTc and 123I without cross-talk correction.

Calorimetric low-temperature detectors for high resolution x-ray spectroscopy on stored highly stripped heavy ions

NASA Astrophysics Data System (ADS)

Bleile, A.; Egelhof, P.; Kraft, S.; McCammon, D.; Meier, H. J.; Shrivastava, A.; Stahle, C. K.; Weber, M.

2002-02-01

The accurate determination of the Lamb shift in heavy hydrogen-like ions provides a sensitive test of quantum electrodynamics in very strong Coulomb fields, not accessible otherwise. For the investigation of the Lyman-α transitions in 208Pb81+ or 238U91+ with sufficient accuracy, a high resolution calorimetric detector for hard x-rays (E<=100 keV) is presently being developed. The detector modules consist of arrays of silicon thermistors and of x-ray absorbers made of high-Z material to optimize the absorption efficiency. The detectors are housed in a specially designed 3He/4He dilution refrigerator with a side arm which fits to the internal target geometry of the storage ring ESR at GSI Darmstadt. The detector performance presently achieved is already close to fulfill the demands of the Lamb shift experiment. For a prototype detector pixel with a 0.2 mm2×47 μm Pb absorber an energy resolution of ΔEFWHM=65 eV is obtained for 60 keV x-rays. .

Basic Performance Test of a Prototype PET Scanner Using CdTe Semiconductor Detectors

NASA Astrophysics Data System (ADS)

Ueno, Y.; Morimoto, Y.; Tsuchiya, K.; Yanagita, N.; Kojima, S.; Ishitsu, T.; Kitaguchi, H.; Kubo, N.; Zhao, S.; Tamaki, N.; Amemiya, K.

2009-02-01

A prototype positron emission tomography (PET) scanner using CdTe semiconductor detectors was developed, and its initial evaluation was conducted. The scanner was configured to form a single detector ring with six separated detector units, each having 96 detectors arranged in three detector layers. The field of view (FOV) size was 82 mm in diameter. Basic physical performance indicators of the scanner were measured through phantom studies and confirmed by rat imaging. The system-averaged energy resolution and timing resolution were 5.4% and 6.0 ns (each in FWHM) respectively. Spatial resolution measured at FOV center was 2.6 mm FWHM. Scatter fraction was measured and calculated in a National Electrical Manufacturers Association (NEMA)-fashioned manner using a 3-mm diameter hot capillary in a water-filled 80-mm diameter acrylic cylinder. The calculated result was 3.6%. Effect of depth of interaction (DOI) measurement was demonstrated by comparing hot-rod phantom images reconstructed with and without DOI information. Finally, images of a rat myocardium and an implanted tumor were visually assessed, and the imaging performance was confirmed.

Tracking performance of a single-crystal and a polycrystalline diamond pixel-detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menasce, D.; et al.

2013-06-01

We present a comparative characterization of the performance of a single-crystal and a polycrystalline diamond pixel-detector employing the standard CMS pixel readout chips. Measurements were carried out at the Fermilab Test Beam Facility, FTBF, using protons of momentum 120 GeV/c tracked by a high-resolution pixel telescope. Particular attention was directed to the study of the charge-collection, the charge-sharing among adjacent pixels and the achievable position resolution. The performance of the single-crystal detector was excellent and comparable to the best available silicon pixel-detectors. The measured average detection-efficiency was near unity, ε = 0.99860±0.00006, and the position-resolution for shared hits was aboutmore » 6 μm. On the other hand, the performance of the polycrystalline detector was hampered by its lower charge collection distance and the readout chip threshold. A new readout chip, capable of operating at much lower threshold (around 1 ke $-$), would be required to fully exploit the potential performance of the polycrystalline diamond pixel-detector.« less

Measurement of the flux of ultrahigh energy cosmic rays from monocular observations by the High Resolution Fly's Eye experiment.

PubMed

Abbasi, R U; Abu-Zayyad, T; Amann, J F; Archbold, G; Bellido, J A; Belov, K; Belz, J W; Bergman, D R; Cao, Z; Clay, R W; Cooper, M D; Dai, H; Dawson, B R; Everett, A A; Fedorova, Yu A; Girard, J H V; Gray, R C; Hanlon, W F; Hoffman, C M; Holzscheiter, M H; Hüntemeyer, P; Jones, B F; Jui, C C H; Kieda, D B; Kim, K; Kirn, M A; Loh, E C; Manago, N; Marek, L J; Martens, K; Martin, G; Matthews, J A J; Matthews, J N; Meyer, J R; Moore, S A; Morrison, P; Moosman, A N; Mumford, J R; Munro, M W; Painter, C A; Perera, L; Reil, K; Riehle, R; Roberts, M; Sarracino, J S; Sasaki, M; Schnetzer, S R; Shen, P; Simpson, K M; Sinnis, G; Smith, J D; Sokolsky, P; Song, C; Springer, R W; Stokes, B T; Taylor, S F; Thomas, S B; Thompson, T N; Thomson, G B; Tupa, D; Westerhoff, S; Wiencke, L R; VanderVeen, T D; Zech, A; Zhang, X

2004-04-16

We have measured the cosmic ray spectrum above 10(17.2) eV using the two air-fluorescence detectors of the High Resolution Fly's Eye observatory operating in monocular mode. We describe the detector, phototube, and atmospheric calibrations, as well as the analysis techniques for the two detectors. We fit the spectrum to a model consisting of galactic and extragalactic sources.

Reconstruction of 2D PET data with Monte Carlo generated system matrix for generalized natural pixels

NASA Astrophysics Data System (ADS)

Vandenberghe, Stefaan; Staelens, Steven; Byrne, Charles L.; Soares, Edward J.; Lemahieu, Ignace; Glick, Stephen J.

2006-06-01

In discrete detector PET, natural pixels are image basis functions calculated from the response of detector pairs. By using reconstruction with natural pixel basis functions, the discretization of the object into a predefined grid can be avoided. Here, we propose to use generalized natural pixel reconstruction. Using this approach, the basis functions are not the detector sensitivity functions as in the natural pixel case but uniform parallel strips. The backprojection of the strip coefficients results in the reconstructed image. This paper proposes an easy and efficient way to generate the matrix M directly by Monte Carlo simulation. Elements of the generalized natural pixel system matrix are formed by calculating the intersection of a parallel strip with the detector sensitivity function. These generalized natural pixels are easier to use than conventional natural pixels because the final step from solution to a square pixel representation is done by simple backprojection. Due to rotational symmetry in the PET scanner, the matrix M is block circulant and only the first blockrow needs to be stored. Data were generated using a fast Monte Carlo simulator using ray tracing. The proposed method was compared to a listmode MLEM algorithm, which used ray tracing for doing forward and backprojection. Comparison of the algorithms with different phantoms showed that an improved resolution can be obtained using generalized natural pixel reconstruction with accurate system modelling. In addition, it was noted that for the same resolution a lower noise level is present in this reconstruction. A numerical observer study showed the proposed method exhibited increased performance as compared to a standard listmode EM algorithm. In another study, more realistic data were generated using the GATE Monte Carlo simulator. For these data, a more uniform contrast recovery and a better contrast-to-noise performance were observed. It was observed that major improvements in contrast recovery were obtained with MLEM when the correct system matrix was used instead of simple ray tracing. The correct modelling was the major cause of improved contrast for the same background noise. Less important factors were the choice of the algorithm (MLEM performed better than ART) and the basis functions (generalized natural pixels gave better results than pixels).

Light-Sharing Interface for dMiCE Detectors using Sub-Surface Laser Engraving.

PubMed

Hunter, William C J; Miyaoka, Robert S; MacDonald, Lawrence; McDougald, Wendy; Lewellen, Thomas K

2013-10-01

We have previously reported on dMiCE, a method of resolving depth or interaction (DOI) in a pair of discrete crystals by encoding light sharing properties as a function of depth in the interface of this crystal-element pair. A challenge for this method is the cost and repeatability of interface treatment for a crystal pair. In this work, we report our preliminary results on using sub-surface laser engraving (SSLE) as a means of forming this depth-dependent interface in a dMiCE detector. A surplus first-generation SSLE system was used to create a partially reflective layer 100-microns thick at the boundary between two halves of a 1.4-by-2.9-by-20 mmˆ3 LYSO crystal. The boundary of these paired crystal elements was positioned between two 3-mm wide Geiger-Müller avalanche photodiodes from Hamamatsu. The responses of these two photodetectors were acquired for an ensemble of 511-keV photons collimated to interact at a fixed depth in just one crystal element. Interaction position was then varied to measure detector response as a function of depth, which was then used to maximum-likelihood positions events. Despite use of sub-optimal SSLE processing we found an average DOI resolution of 3.4 mm for front-sided readout and 3.9 mm for back-sided readout. We expect DOI resolution can be improved significantly by optimizing the SSLE process and pattern.

Light-Sharing Interface for dMiCE Detectors using Sub-Surface Laser Engraving

PubMed Central

Hunter, William C.J.; Miyaoka, Robert S.; MacDonald, Lawrence; McDougald, Wendy; Lewellen, Thomas K.

2014-01-01

We have previously reported on dMiCE, a method of resolving depth or interaction (DOI) in a pair of discrete crystals by encoding light sharing properties as a function of depth in the interface of this crystal-element pair. A challenge for this method is the cost and repeatability of interface treatment for a crystal pair. In this work, we report our preliminary results on using sub-surface laser engraving (SSLE) as a means of forming this depth-dependent interface in a dMiCE detector. A surplus first-generation SSLE system was used to create a partially reflective layer 100-microns thick at the boundary between two halves of a 1.4-by-2.9-by-20 mmˆ3 LYSO crystal. The boundary of these paired crystal elements was positioned between two 3-mm wide Geiger-Müller avalanche photodiodes from Hamamatsu. The responses of these two photodetectors were acquired for an ensemble of 511-keV photons collimated to interact at a fixed depth in just one crystal element. Interaction position was then varied to measure detector response as a function of depth, which was then used to maximum-likelihood positions events. Despite use of sub-optimal SSLE processing we found an average DOI resolution of 3.4 mm for front-sided readout and 3.9 mm for back-sided readout. We expect DOI resolution can be improved significantly by optimizing the SSLE process and pattern. PMID:25506194

SU-E-CAMPUS-I-04: Automatic Skin-Dose Mapping for An Angiographic System with a Region-Of-Interest, High-Resolution Detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vijayan, S; Rana, V; Setlur Nagesh, S

2014-06-15

Purpose: Our real-time skin dose tracking system (DTS) has been upgraded to monitor dose for the micro-angiographic fluoroscope (MAF), a high-resolution, small field-of-view x-ray detector. Methods: The MAF has been mounted on a changer on a clinical C-Arm gantry so it can be used interchangeably with the standard flat-panel detector (FPD) during neuro-interventional procedures when high resolution is needed in a region-of-interest. To monitor patient skin dose when using the MAF, our DTS has been modified to automatically account for the change in scatter for the very small MAF FOV and to provide separated dose distributions for each detector. Themore » DTS is able to provide a color-coded mapping of the cumulative skin dose on a 3D graphic model of the patient. To determine the correct entrance skin exposure to be applied by the DTS, a correction factor was determined by measuring the exposure at the entrance surface of a skull phantom with an ionization chamber as a function of entrance beam size for various beam filters and kVps. Entrance exposure measurements included primary radiation, patient backscatter and table forward scatter. To allow separation of the dose from each detector, a parameter log is kept that allows a replay of the procedure exposure events and recalculation of the dose components.The graphic display can then be constructed showing the dose distribution from the MAF and FPD separately or together. Results: The DTS is able to provide separate displays of dose for the MAF and FPD with field-size specific scatter corrections. These measured corrections change from about 49% down to 10% when changing from the FPD to the MAF. Conclusion: The upgraded DTS allows identification of the patient skin dose delivered when using each detector in order to achieve improved dose management as well as to facilitate peak skin-dose reduction through dose spreading. Research supported in part by Toshiba Medical Systems Corporation and NIH Grants R43FD0158401, R44FD0158402 and R01EB002873.« less

Development of an integrated four-channel fast avalanche-photodiode detector system with nanosecond time resolution

NASA Astrophysics Data System (ADS)

Li, Zhenjie; Li, Qiuju; Chang, Jinfan; Ma, Yichao; Liu, Peng; Wang, Zheng; Hu, Michael Y.; Zhao, Jiyong; Alp, E. E.; Xu, Wei; Tao, Ye; Wu, Chaoqun; Zhou, Yangfan

2017-10-01

A four-channel nanosecond time-resolved avalanche-photodiode (APD) detector system is developed at Beijing Synchrotron Radiation. It uses a single module for signal processing and readout. This integrated system provides better reliability and flexibility for custom improvement. The detector system consists of three parts: (i) four APD sensors, (ii) four fast preamplifiers and (iii) a time-digital-converter (TDC) readout electronics. The C30703FH silicon APD chips fabricated by Excelitas are used as the sensors of the detectors. It has an effective light-sensitive area of 10 × 10 mm2 and an absorption layer thickness of 110 μm. A fast preamplifier with a gain of 59 dB and bandwidth of 2 GHz is designed to readout of the weak signal from the C30703FH APD. The TDC is realized by a Spartan-6 field-programmable-gate-array (FPGA) with multiphase method in a resolution of 1ns. The arrival time of all scattering events between two start triggers can be recorded by the TDC. The detector has been used for nuclear resonant scattering study at both Advanced Photon Source and also at Beijing Synchrotron Radiation Facility. For the X-ray energy of 14.4 keV, the time resolution, the full width of half maximum (FWHM) of the detector (APD sensor + fast amplifier) is 0.86 ns, and the whole detector system (APD sensors + fast amplifiers + TDC readout electronics) achieves a time resolution of 1.4 ns.

SU-F-T-559: High-Resolution Scintillating Fiber Array for In-Vivo Real-Time SRS and SBRT Patient QA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knewtson, T; Pokhrel, S; University of Tennessee Health Science Center, Memphis, TN

2016-06-15

Purpose: A high-resolution scintillating fiber detector was built for in-vivo real-time patient specific quality assurance (QA). The detector is designed for stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS) to monitor treatment delivery and detect real-time deviations from planned dose to increase patient safety and treatment accuracy. Methods: The detector consists of two high-density scintillating fiber arrays layered to form an X-Y grid which can be attached to the accessory tray of a medical linac for SBRT and cone SRS treatment QA. Fiber arrays consist of 128 scintillating fibers embedded within a precision-machined, high-transmission polymer substrate with 0.8mm pitch. Themore » fibers are coupled on both ends to high-sensitivity photodetectors and the output is recorded through a high-speed analog-to-digital converter to capture the linac pulse sequence as treatment delivery progresses. The detector has a software controlled 360 degree rotational system to capture angular beam projections for high-resolution beam profile reconstruction. Results: The detector was validated using SRS cone sizes from 6mm to 34mm and MLC defined field sizes from 5×5mm2 to 100×100mm2. The detector output response is linear with dose and is dose rate independent. Each field can be reconstructed accurately with a spatial resolution of 0.8mm and the current beam output is displayed every 50msec. Dosimetric errors of 1% with respect to the treatment plan can be identified and clinically significant deviations from the expected treatment can be displayed in real-time to alert the therapists. Conclusion: The high resolution detector is capable of reconstructing beam profiles in real-time with submillimeter resolution and 1% dose resolution. This system has the ability to project in-vivo both spatial and dosimetric errors during SBRT and SRS treatments when only a non-clinically significant fraction of the intended dose was delivered. The device has the potential to establish new standards for in-vivo patient specific QA.« less

Spatial resolution limits for the isotropic-3D PET detector X’tal cube

NASA Astrophysics Data System (ADS)

Yoshida, Eiji; Tashima, Hideaki; Hirano, Yoshiyuki; Inadama, Naoko; Nishikido, Fumihiko; Murayama, Hideo; Yamaya, Taiga

2013-11-01

Positron emission tomography (PET) has become a popular imaging method in metabolism, neuroscience, and molecular imaging. For dedicated human brain and small animal PET scanners, high spatial resolution is needed to visualize small objects. To improve the spatial resolution, we are developing the X’tal cube, which is our new PET detector to achieve isotropic 3D positioning detectability. We have shown that the X’tal cube can achieve 1 mm3 uniform crystal identification performance with the Anger-type calculation even at the block edges. We plan to develop the X’tal cube with even smaller 3D grids for sub-millimeter crystal identification. In this work, we investigate spatial resolution of a PET scanner based on the X’tal cube using Monte Carlo simulations for predicting resolution performance in smaller 3D grids. For spatial resolution evaluation, a point source emitting 511 keV photons was simulated by GATE for all physical processes involved in emission and interaction of positrons. We simulated two types of animal PET scanners. The first PET scanner had a detector ring 14.6 cm in diameter composed of 18 detectors. The second PET scanner had a detector ring 7.8 cm in diameter composed of 12 detectors. After the GATE simulations, we converted the interacting 3D position information to digitalized positions for realistic segmented crystals. We simulated several X’tal cubes with cubic crystals from (0.5 mm)3 to (2 mm)3 in size. Also, for evaluating the effect of DOI resolution, we simulated several X’tal cubes with crystal thickness from (0.5 mm)3 to (9 mm)3. We showed that sub-millimeter spatial resolution was possible using cubic crystals smaller than (1.0 mm)3 even with the assumed physical processes. Also, the weighted average spatial resolutions of both PET scanners with (0.5 mm)3 cubic crystals were 0.53 mm (14.6 cm ring diameter) and 0.48 mm (7.8 cm ring diameter). For the 7.8 cm ring diameter, spatial resolution with 0.5×0.5×1.0 mm3 crystals was improved 39% relative to the (1 mm)3 cubic crystals. On the other hand, spatial resolution with (0.5 mm)3 cubic crystals was improved 47% relative to the (1 mm)3 cubic crystals. The X’tal cube promises better spatial resolution for the 3D crystal block with isotropic resolution.

Performance studies of X3 silicon detectors for the future ELISSA array at ELI-NP

NASA Astrophysics Data System (ADS)

Chesnevskaya, S.; Balabanski, D. L.; Choudhury, D.; Constantin, P.; Filipescu, D. M.; Ghita, D. G.; Guardo, G. L.; Lattuada, D.; Matei, C.; Rotaru, A.; State, A.

2018-05-01

ELISSA is an array of silicon strip detectors under construction at the ELI-NP facility for measurements of photodissociation reactions using high-brilliance, quasi monoenergetic gamma beams. The detection system consists of 35 single-sided position-sensitive X3 detectors arranged in a cylindrical configuration and eight QQQ3 detectors as end-caps. A batch of forty X3 detectors have been tested at ELI-NP. The energy and position resolution, ballistic deficit, leakage currents, and depletion voltage were measured and analyzed. Measurements of the energy resolution were carried out using two read-out electronic chains, one based on multichannel preamplifiers and another based on multiplexers.

BTDI detector technology for reconnaissance application

NASA Astrophysics Data System (ADS)

Hilbert, Stefan; Eckardt, Andreas; Krutz, David

2017-11-01

The Institute of Optical Sensor Systems (OS) at the Robotics and Mechatronics Center of the German Aerospace Center (DLR) has more than 30 years of experience with high-resolution imaging technology. This paper shows the institute's scientific results of the leading-edge detector design in a BTDI (Bidirectional Time Delay and Integration) architecture. This project demonstrates an approved technological design for high or multi-spectral resolution spaceborne instruments. DLR OS and BAE Systems were driving the technology of new detectors and the FPA design for future projects, new manufacturing accuracy in order to keep pace with ambitious scientific and user requirements. Resulting from customer requirements and available technologies the current generation of space borne sensor systems is focusing on VIS/NIR high spectral resolution to meet the requirements on earth and planetary observation systems. The combination of large swath and high-spectral resolution with intelligent control applications and new focal plane concepts opens the door to new remote sensing and smart deep space instruments. The paper gives an overview of the detector development and verification program at DLR on detector module level and key parameters like SNR, linearity, spectral response, quantum efficiency, PRNU, DSNU and MTF.

Enhanced R200 with Frisch-Grid CZT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bolotnikov, A.

2017-12-01

The goal of this project is to demonstrate an engineering prototype of a gamma ray spectrometer that uses Cadmium Zinc Telluride (CZT) in a configuration comprised of an array of position-sensitive virtual Frisch grid (PSVFG) detectors and show its capability to perform functions that would be useful to the IAEA. The detectors should achieve energy resolution of ~2% at 200 keV and <1% at > 662 keV, thereby outperforming all hand-held instruments currently in use other than cryogenically cooled germanium. BNL will make every effort to transfer the technology to an industrial partner so that robust, fieldable instruments can bemore » manufactured.« less

Enhanced R200 with Frisch-Grid CZT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bolotnikov, Aleksey

The goal of this project is to demonstrate an engineering prototype of a gamma ray spectrometer that uses Cadmium Zinc Telluride (CZT) in a configuration comprised of an array of position-sensitive virtual Frisch grid (PSVFG) detectors and show its capability to perform functions that would be useful to the IAEA. The detectors should achieve energy resolution of ~2% at 200 keV and <1% at > 662 keV, thereby outperforming all hand-held instruments currently in use other than cryogenically cooled germanium. BNL will make every effort to transfer the technology to an industrial partner so that robust, fieldable instruments can bemore » manufactured.« less

Characterization of a 6Li enriched Cs2LiYCl6:Ce scintillator and its application as a γ-ray detector

NASA Astrophysics Data System (ADS)

Qin, Jianguo; Lai, Caifeng; Lu, Xinxin; Zheng, Pu; Zhu, Tonghua; Liu, Rong; Ye, Bangjiao; Zhang, Xinwei

2018-04-01

In this work, we characterize the γ-ray response and efficiency for a cylindrical inorganic Cs2LiYCl6:Ce detector 1‧‧ in diameter and 1‧‧ in height. The energy resolution and linearity are obtained from 21 γ-rays with energies ranging from 0.026 to 2.447 MeV. In addition, the neutron γ-ray discrimination is validated by measuring a 252Cf radioisotope. Gamma-ray response functions and matrix below 7 MeV are simulated using a Monte Carlo approach and validated through the unfolded γ-ray spectra.

Characterization of EJ-200 plastic scintillators as active background shield for cosmogenic radiation

NASA Astrophysics Data System (ADS)

Tkaczyk, A. H.; Saare, H.; Ipbüker, C.; Schulte, F.; Mastinu, P.; Paepen, J.; Pedersen, B.; Schillebeeckx, P.; Varasano, G.

2018-02-01

This paper describes the characterization of commercially available plastic scintillation detectors to be used as an active shield or veto system to reduce the neutron background resulting from atmospheric muon interactions in low-level nuclear waste assay systems. The shield consists of an array of scintillation detectors surrounding a neutron detection system. Scintillation detectors with different thicknesses are characterized for their response to gamma rays, neutrons, and muons. Response functions to gamma rays were determined and measured in the energy range from 0.6 MeV to 6.0 MeV using radionuclide sources. Neutron response functions were derived from results of time-of-flight measurements at the Van de Graaff accelerator of the INFN Legnaro and from measurements with quasi mono-energetic neutron beams produced at the Van de Graaff accelerator of the JRC Geel. From these data, the light output and resolution functions for protons and electrons were derived. The response to muons was verified by background measurements, i.e. without the presence of any neutron or gamma source. It was found that the muon peak is more pronounced when the detectors are placed horizontally. The results indicate that a scintillator with a minimum thickness of 20 mm is needed to separate events due to atmospheric muons from natural gamma ray background, and contributions due to neutron production in nuclear waste based on only the total energy deposition in the detector. In addition, it was shown that muons can be identified with a coincidence pattern when the detectors are stacked. The effectiveness of the proposed system was demonstrated based on muon induced spallation reactions in a lead sample.

The STIS MAMA status: Current detector performance

NASA Technical Reports Server (NTRS)

Danks, A. C.; Joseph, C.; Bybee, R.; Argebright, V.; Abraham, J.; Kimble, R.; Woodgate, B.

1992-01-01

The STIS (Space Telescope Imaging Spectrograph) is a second generation Hubble instrument scheduled to fly in 1997. Through a variety of modes, the instrument will provide spectral resolutions from R approximately 50 in the objective spectroscopy mode to 100,000 in the high resolution echelle mode in the wavelength region from 115 to 1000 nm. In the UV the instrument employs two MAMA (Multimode Anode Microchannel plate Arrays) 1024 by 1024 pixel detectors, which provide high DQE (Detective Quantum Efficiency), and good dynamic range and resolution. The current progress and performance of these detectors are reported, illustrating that the technology is mature and that the performance is very close to flight requirements.

High resolution x-ray and gamma ray imaging using diffraction lenses with mechanically bent crystals

DOEpatents

Smither, Robert K [Hinsdale, IL

2008-12-23

A method for high spatial resolution imaging of a plurality of sources of x-ray and gamma-ray radiation is provided. High quality mechanically bent diffracting crystals of 0.1 mm radial width are used for focusing the radiation and directing the radiation to an array of detectors which is used for analyzing their addition to collect data as to the location of the source of radiation. A computer is used for converting the data to an image. The invention also provides for the use of a multi-component high resolution detector array and for narrow source and detector apertures.

Multi-pinhole SPECT Imaging with Silicon Strip Detectors

PubMed Central

Peterson, Todd E.; Shokouhi, Sepideh; Furenlid, Lars R.; Wilson, Donald W.

2010-01-01

Silicon double-sided strip detectors offer outstanding instrinsic spatial resolution with reasonable detection efficiency for iodine-125 emissions. This spatial resolution allows for multiple-pinhole imaging at low magnification, minimizing the problem of multiplexing. We have conducted imaging studies using a prototype system that utilizes a detector of 300-micrometer thickness and 50-micrometer strip pitch together with a 23-pinhole collimator. These studies include an investigation of the synthetic-collimator imaging approach, which combines multiple-pinhole projections acquired at multiple magnifications to obtain tomographic reconstructions from limited-angle data using the ML-EM algorithm. Sub-millimeter spatial resolution was obtained, demonstrating the basic validity of this approach. PMID:20953300

X-ray spectrometer with a low-cost SiC photodiode

NASA Astrophysics Data System (ADS)

Zhao, S.; Lioliou, G.; Barnett, A. M.

2018-04-01

A low-cost Commercial-Off-The-Shelf (COTS) 4H-SiC 0.06 mm2 UV p-n photodiode was coupled to a low-noise charge-sensitive preamplifier and used as photon counting X-ray spectrometer. The photodiode/spectrometer was investigated at X-ray energies from 4.95 keV to 21.17 keV: a Mo cathode X-ray tube was used to fluoresce eight high-purity metal foils to produce characteristic X-ray emission lines which were used to characterise the instrument. The energy resolution (full width at half maximum, FWHM) of the spectrometer was found to be 1.6 keV to 1.8 keV, across the energy range. The energy linearity of the detector/spectrometer (i.e. the detector's charge output per photon as a function of incident photon energy across the 4.95 keV to 21.17 keV energy range), as well as the count rate linearity of the detector/spectrometer (i.e. number of detected photons as a function of photon fluence at a specific energy) were investigated. The energy linearity of the detector/spectrometer was linear with an error < ± 0.7 %; the count rate linearity of the detector/spectrometer was linear with an error < ± 2 %. The use of COTS SiC photodiodes as detectors for X-ray spectrometers is attractive for nanosatellite/CubeSat applications (including solar flare monitoring), and for cost sensitive industrial uses.

Energy dependent features of X-ray signals in a GridPix detector

NASA Astrophysics Data System (ADS)

Krieger, C.; Kaminski, J.; Vafeiadis, T.; Desch, K.

2018-06-01

We report on the calibration of an argon/isobutane (97.7%/2.3%)-filled GridPix detector with soft X-rays (277 eV to 8 keV) using the variable energy X-ray source of the CAST Detector Lab at CERN. We study the linearity and energy resolution of the detector using both the number of pixels hit and the total measured charge as energy measures. For the latter, the energy resolution σE / E is better than 10% (20%) for energies above 2 keV (0.5 keV). Several characteristics of the recorded events are studied.

Radiology utilizing a gas multiwire detector with resolution enhancement

DOEpatents

Majewski, Stanislaw; Majewski, Lucasz A.

1999-09-28

This invention relates to a process and apparatus for obtaining filmless, radiological, digital images utilizing a gas multiwire detector. Resolution is enhanced through projection geometry. This invention further relates to imaging systems for X-ray examination of patients or objects, and is particularly suited for mammography.

Lead and uranium group abundances in cosmic rays

NASA Technical Reports Server (NTRS)

Yadav, J. S.; Perelygin, V. P.

1985-01-01

The importance of Lead and Uranium group abundances in cosmic rays is discussed in understanding their evolution and propagation. The electronic detectors can provide good charge resolution but poor data statistics. The plastic detectors can provide somewhat better statistics but charge resolution deteriorates. The extraterrestrial crystals can provide good statistics but with poor charge resolution. Recent studies of extraterrestrial crystals regarding their calibration to accelerated uranium ion beam and track etch kinetics are discussed. It is hoped that a charge resolution of two charge units can be achieved provided an additional parameter is taken into account. The prospects to study abundances of Lead group, Uranium group and superheavy element in extraterrestrial crystals are discussed, and usefulness of these studies in the light of studies with electronic and plastic detectors is assessed.

Performance of a high-resolution depth-encoding PET detector module using linearly-graded SiPM arrays

NASA Astrophysics Data System (ADS)

Du, Junwei; Bai, Xiaowei; Gola, Alberto; Acerbi, Fabio; Ferri, Alessandro; Piemonte, Claudio; Yang, Yongfeng; Cherry, Simon R.

2018-02-01

The goal of this study was to exploit the excellent spatial resolution characteristics of a position-sensitive silicon photomultiplier (SiPM) and develop a high-resolution depth-of-interaction (DOI) encoding positron emission tomography (PET) detector module. The detector consists of a 30  ×  30 array of 0.445  ×  0.445  ×  20 mm3 polished LYSO crystals coupled to two 15.5  ×  15.5 mm2 linearly-graded SiPM (LG-SiPM) arrays at both ends. The flood histograms show that all the crystals in the LYSO array can be resolved. The energy resolution, the coincidence timing resolution and the DOI resolution were 21.8  ±  5.8%, 1.23  ±  0.10 ns and 3.8  ±  1.2 mm, respectively, at a temperature of -10 °C and a bias voltage of 35.0 V. The performance did not degrade significantly for event rates of up to 130 000 counts s-1. This detector represents an attractive option for small-bore PET scanner designs that simultaneously emphasize high spatial resolution and high detection efficiency, important, for example, in preclinical imaging of the rodent brain with neuroreceptor ligands.

Athermal Energy Loss from X-rays Deposited in Thin Superconducting Films on Solid Substrates

NASA Technical Reports Server (NTRS)

Kozorezov, Alexander G.; Lambert, Colin J.; Bandler, Simon R.; Balvin, Manuel A.; Busch, Sarah E.; Sagler, Peter N.; Porst, Jan-Patrick; Smith, Stephen J.; Stevenson, Thomas R.; Sadleir, John E.

2013-01-01

When energy is deposited in a thin-film cryogenic detector, such as from the absorption of an X-ray, an important feature that determines the energy resolution is the amount of athermal energy that can be lost to the heat bath prior to the elementary excitation systems coming into thermal equilibrium. This form of energy loss will be position-dependent and therefore can limit the detector energy resolution. An understanding of the physical processes that occur when elementary excitations are generated in metal films on dielectric substrates is important for the design and optimization of a number of different types of low temperature detector. We have measured the total energy loss in one relatively simple geometry that allows us to study these processes and compare measurements with calculation based upon a model for the various di.erent processes. We have modeled the athermal phonon energy loss in this device by finding an evolving phonon distribution function that solves the system of kinetic equations for the interacting system of electrons and phonons. Using measurements of device parameters such as the Debye energy and the thermal di.usivity we have calculated the expected energy loss from this detector geometry, and also the position-dependent variation of this loss. We have also calculated the predicted impact on measured spectral line-shapes, and shown that they agree well with measurements. In addition, we have tested this model by using it to predict the performance of a number of other types of detector with di.erent geometries, where good agreement is also found.

Simulation of energy spectrum of GEM detector from an x-ray quantum

NASA Astrophysics Data System (ADS)

Malinowski, K.; Chernyshova, M.; Czarski, T.; Kowalska-Strzęciwilk, E.; Linczuk, P.; Wojeński, A.; Krawczyk, R.; Gąska, M.

2018-01-01

This paper presents the results of the energy resolution simulation for the triple GEM-based detector for x-ray quantum of 5.9 keV . Photons of this energy are emitted by 55Fe source, which is a standard calibration marker for this type of detectors. The calculations were made in Garfield++ in two stages. In the first stage, the distribution of the amount of primary electrons generated in the drift volume by the x-ray quantum was simulated using the Heed program. Secondly, the primary electrons of the resulting quantitative distribution were treated as a source of electron avalanches propagated through the whole volume of the triple GEM-based detector. The distribution of the obtained signals created a spectrum corresponding to the peak at 5.9 keV, which allowed us to determine the theoretical energy resolution of the detector. Its knowledge allows observing and improving the eventual experimental deterioration of the energy resolution, inevitably accompanying processes of registration and processing of the signals.

Picosecond timing resolution detection of ggr-photons utilizing microchannel-plate detectors: experimental tests of quantum nonlocality and photon localization

NASA Astrophysics Data System (ADS)

Irby, Victor D.

2004-09-01

The concept and subsequent experimental verification of the proportionality between pulse amplitude and detector transit time for microchannel-plate detectors is presented. This discovery has led to considerable improvement in the overall timing resolution for detection of high-energy ggr-photons. Utilizing a 22Na positron source, a full width half maximum (FWHM) timing resolution of 138 ps has been achieved. This FWHM includes detector transit-time spread for both chevron-stack-type detectors, timing spread due to uncertainties in annihilation location, all electronic uncertainty and any remaining quantum mechanical uncertainty. The first measurement of the minimum quantum uncertainty in the time interval between detection of the two annihilation photons is reported. The experimental results give strong evidence against instantaneous spatial localization of ggr-photons due to measurement-induced nonlocal quantum wavefunction collapse. The experimental results are also the first that imply momentum is conserved only after the quantum uncertainty in time has elapsed (Yukawa H 1935 Proc. Phys. Math. Soc. Japan 17 48).

Timing Characterization of Helium-4 Fast Neutron Detector with EJ-309 Organic Liquid Scintillator

NASA Astrophysics Data System (ADS)

Liang, Yinong; Zhu, Ting; Enqvist, Andreas

2018-01-01

Recently, the Helium-4 gas fast neutron scintillation detectors is being used in time-sensitive measurements, such time-of-flight and multiplicity counting. In this paper, a set of time aligned signals was acquired in a coincidence measurement using the Helium-4 gas detectors and EJ-309 liquid scintillators. The high-speed digitizer system is implanted with a trigger moving average window (MAW) unit combing with its constant fraction discriminator (CFD) feature. It can calculate a "time offset" to the timestamp value to get a higher resolution timestamp (up to 50 ps), which is better than the digitizer's time resolution (4 ns) [1]. The digitized waveforms were saved to the computer hard drive and post processed with digital analysis code to determine the difference of their arrival times. The full-width at half-maximum (FWHM) of the Gaussian fit was used as to examine the resolution. For the cascade decay of Cobalt-60 (1.17 and 1.33 MeV), the first version of the Helium-4 detector with two Hamamatsu R580 photomultipliers (PMT) installed at either end of the cylindrical gas chamber (20 cm in length and 4.4 cm in diameter) has a time resolution which is about 3.139 ns FWHM. With improved knowledge of the timing performance, the Helium-4 scintillation detectors are excellent for neutron energy spectrometry applications requiring high temporal and energy resolutions.

Toward high-resolution NMR spectroscopy of microscopic liquid samples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butler, Mark C.; Mehta, Hardeep S.; Chen, Ying

A longstanding limitation of high-resolution NMR spectroscopy is the requirement for samples to have macroscopic dimensions. Commercial probes, for example, are designed for volumes of at least 5 mL, in spite of decades of work directed toward the goal of miniaturization. Progress in miniaturizing inductive detectors has been limited by a perceived need to meet two technical requirements: (1) minimal separation between the sample and the detector, which is essential for sensitivity, and (2) near-perfect magnetic-field homogeneity at the sample, which is typically needed for spectral resolution. The first of these requirements is real, but the second can be relaxed,more » as we demonstrate here. By using pulse sequences that yield high-resolution spectra in an inhomogeneous field, we eliminate the need for near-perfect field homogeneity and the accompanying requirement for susceptibility matching of microfabricated detector components. With this requirement removed, typical imperfections in microfabricated components can be tolerated, and detector dimensions can be matched to those of the sample, even for samples of volume << 5 uL. Pulse sequences that are robust to field inhomogeneity thus enable small-volume detection with optimal sensitivity. We illustrate the potential of this approach to miniaturization by presenting spectra acquired with a flat-wire detector that can easily be scaled to subnanoliter volumes. In particular, we report high-resolution NMR spectroscopy of an alanine sample of volume 500 pL.« less

A high-resolution x-ray spectrometer for a kaon mass measurement

NASA Astrophysics Data System (ADS)

Phelan, Kevin; Suzuki, Ken; Zmeskal, Johann; Tortorella, Daniele; Bühler, Matthias; Hertrich, Theo

2017-02-01

The ASPECT consortium (Adaptable Spectrometer Enabled by Cryogenic Technology) is currently constructing a generalised cryogenic platform for cryogenic detector work which will be able to accommodate a wide range of sensors. The cryogenics system is based on a small mechanical cooler with a further adiabatic demagnetisation stage and will work with cryogenic detectors at sub-Kelvin temperatures. The commercial aim of the consortium is to produce a compact, user-friendly device with an emphasis on reliability and portability which can easily be transported for specialised on-site work, such as beam-lines or telescope facilities. The cryogenic detector platform will accommodate a specially developed cryogenic sensor, either a metallic magnetic calorimeter or a magnetic penetration-depth thermometer. The detectors will be designed to work in various temperatures regions with an emphasis on optimising the various detector resolutions for specific temperatures. One resolution target is of about 10 eV at the energies range typically created in kaonic atoms experiments (soft x-ray energies). A following step will see the introduction of continuous, high-power, sub-Kelvin cooling which will bring the cryogenic basis for a high resolution spectrometer system to the market. The scientific goal of the project will produce an experimental set-up optimised for kaon-mass measurements performing high-resolution x-ray spectroscopy on a beam-line provided foreseeably by the J-PARC (Tokai, Japan) or DAΦNE (Frascati, Italy) facilities.

High resolution, two-dimensional imaging, microchannel plate detector for use on a sounding rocket experiment

NASA Technical Reports Server (NTRS)

Bush, Brett C.; Cotton, Daniel M.; Siegmund, Oswald H.; Chakrabarti, Supriya; Harris, Walter; Clarke, John

1991-01-01

We discuss a high resolution microchannel plate (MCP) imaging detector to be used in measurements of Doppler-shifted hydrogen Lyman-alpha line emission from Jupiter and the interplanetary medium. The detector is housed in a vacuum-tight stainless steel cylinder (to provide shielding from magnetic fields) with a MgF2 window. Operating at nominal voltage, the four plate configuration provides a gain of 1.2 x 10 exp 7 electrons per incident photon. The wedge-and-strip anode has two-dimensional imaging capabilities, with a resolution of 40 microns FWHM over a one centimeter diameter area. The detector has a high quantum efficiency while retaining a low background rate. A KBr photocathode is used to enhance the quantum efficiency of the bare MCPs to a value of 35 percent at Lyman-alpha.

Design Studies of a CZT-based Detector Combined with a Pixel-Geometry-Matching Collimator for SPECT Imaging.

PubMed

Weng, Fenghua; Bagchi, Srijeeta; Huang, Qiu; Seo, Youngho

2013-10-01

Single Photon Emission Computed Tomography (SPECT) suffers limited efficiency due to the need for collimators. Collimator properties largely decide the data statistics and image quality. Various materials and configurations of collimators have been investigated in many years. The main thrust of our study is to evaluate the design of pixel-geometry-matching collimators to investigate their potential performances using Geant4 Monte Carlo simulations. Here, a pixel-geometry-matching collimator is defined as a collimator which is divided into the same number of pixels as the detector's and the center of each pixel in the collimator is a one-to-one correspondence to that in the detector. The detector is made of Cadmium Zinc Telluride (CZT), which is one of the most promising materials for applications to detect hard X-rays and γ -rays due to its ability to obtain good energy resolution and high light output at room temperature. For our current project, we have designed a large-area, CZT-based gamma camera (20.192 cm×20.192 cm) with a small pixel pitch (1.60 mm). The detector is pixelated and hence the intrinsic resolution can be as small as the size of the pixel. Materials of collimator, collimator hole geometry, detection efficiency, and spatial resolution of the CZT detector combined with the pixel-matching collimator were calculated and analyzed under different conditions. From the simulation studies, we found that such a camera using rectangular holes has promising imaging characteristics in terms of spatial resolution, detection efficiency, and energy resolution.

A Prototype Combination TPC Cherenkov Detector with GEM Readout for Tracking and Particle Identification and its Potential Use at an Electron Ion Collider

NASA Astrophysics Data System (ADS)

Woody, Craig; Azmoun, Babak; Majka, Richard; Phipps, Michael; Purschke, Martin; Smirnov, Nikolai

2018-02-01

A prototype detector is being developed which combines the functions of a Time Projection Chamber for charged particle tracking and a Cherenkov detector for particle identification. The TPC consists of a 10×10×10 cm3 drift volume where the charge is drifted to a 10×10 cm2 triple GEM detector. The charge is measured on a readout plane consisting of 2×10 mm2 chevron pads which provide a spatial resolution ˜ 100 μm per point in the chevron direction along with dE/dx information. The Cherenkov portion of the detector consists of a second 10×10 cm2 triple GEM with a photosensitive CsI photocathode on the top layer. This detector measures Cherenkov light produced in the drift gas of the TPC by high velocity particles which are above threshold. CF4 or CF4 mixtures will be used as the drift gas which are highly transparent to UV light and can provide excellent efficiency for detecting Cherenkov photons. The drift gas is also used as the operating gas for both GEM detectors. The prototype detector has been constructed and is currently being tested in the lab with sources and cosmic rays, and additional tests are planned in the future to study the detector in a test beam.

Investigation of spatial resolution and temporal performance of SAPHIRE (scintillator avalanche photoconductor with high resolution emitter readout) with integrated electrostatic focusing

NASA Astrophysics Data System (ADS)

Scaduto, David A.; Lubinsky, Anthony R.; Rowlands, John A.; Kenmotsu, Hidenori; Nishimoto, Norihito; Nishino, Takeshi; Tanioka, Kenkichi; Zhao, Wei

2014-03-01

We have previously proposed SAPHIRE (scintillator avalanche photoconductor with high resolution emitter readout), a novel detector concept with potentially superior spatial resolution and low-dose performance compared with existing flat-panel imagers. The detector comprises a scintillator that is optically coupled to an amorphous selenium photoconductor operated with avalanche gain, known as high-gain avalanche rushing photoconductor (HARP). High resolution electron beam readout is achieved using a field emitter array (FEA). This combination of avalanche gain, allowing for very low-dose imaging, and electron emitter readout, providing high spatial resolution, offers potentially superior image quality compared with existing flat-panel imagers, with specific applications to fluoroscopy and breast imaging. Through the present collaboration, a prototype HARP sensor with integrated electrostatic focusing and nano- Spindt FEA readout technology has been fabricated. The integrated electron-optic focusing approach is more suitable for fabricating large-area detectors. We investigate the dependence of spatial resolution on sensor structure and operating conditions, and compare the performance of electrostatic focusing with previous technologies. Our results show a clear dependence of spatial resolution on electrostatic focusing potential, with performance approaching that of the previous design with external mesh-electrode. Further, temporal performance (lag) of the detector is evaluated and the results show that the integrated electrostatic focusing design exhibits comparable or better performance compared with the mesh-electrode design. This study represents the first technical evaluation and characterization of the SAPHIRE concept with integrated electrostatic focusing.

Waveform digitization for high resolution timing detectors with silicon photomultipliers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ronzhin, A.; Albrow, M. G.; Los, S.

2012-03-01

The results of time resolution studies with silicon photomultipliers (SiPMs) read out with high bandwidth constant fraction discrimination electronics were presented earlier [1-3]. Here we describe the application of fast waveform digitization readout based on the DRS4 chip [4], a switched capacitor array (SCA) produced by the Paul Scherrer Institute, to further our goal of developing high time resolution detectors based on SiPMs. The influence of the SiPM signal shape on the time resolution was investigated. Different algorithms to obtain the best time resolution are described, and test beam results are presented.

Optimizing the position resolution of a Z-stack microchannel plate resistive anode detector for low intensity signals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiggins, B. B.; Richardson, E.; Siwal, D.

A method for achieving good position resolution of low-intensity electron signals using a microchannel plate resistive anode detector is demonstrated. Electron events at a rate of 7 counts s{sup −1} are detected using a Z-stack microchannel plate. The dependence of position resolution on both the distance and the potential difference between the microchannel plate and resistive anode is investigated. Using standard commercial electronics, a measured position resolution of 170 μm (FWHM) is obtained, which corresponds to an intrinsic resolution of 157 μm (FWHM)

Digital pulse processing for planar TlBr detectors

NASA Astrophysics Data System (ADS)

Nakhostin, M.; Hitomi, K.; Ishii, K.; Kikuchi, Y.

2010-04-01

We report on a digital pulse processing algorithm for correction of charge trapping in the planar TlBr detectors. The algorithm is performed on the signals digitized at the preamplifier stage. The algorithm is very simple and is implemented with little computational effort. By using a digitizer with a sampling rate of 250 MSample/s and 8 bit resolution, an energy resolution of 6.5% is achieved at 511 keV with a 0.7 mm thick detector.

Design and prototype results of the FAST detector

NASA Astrophysics Data System (ADS)

Mozzanica, A.; Basset, M.; Caccia, M.; Corradini, M.; Leali, M.; Lodi Rizzini, E.; Prest, M.; Venturelli, L.; Vallazza, E.; Zurlo, N.

2006-11-01

A new fiber tracker is being developed for the ASACUSA experiment at the Antiproton Decelerator at CERN. The detector is based on 1 mm diameter scintillating fibers readout by HAMAMATSU 64 channel multianode photomultipliers (MA-PMTs) connected to a dedicated electronic chain. The paper gives a description of the testing procedures for time resolution, spatial resolution and efficiency measurements performed with standard NIM electronics and a commercial TDC and reports the results for different prototype detectors.

Molecular imaging with radionuclides, a powerful technique for studying biological processes in vivo

NASA Astrophysics Data System (ADS)

Cisbani, E.; Cusanno, F.; Garibaldi, F.; Magliozzi, M. L.; Majewski, S.; Torrioli, S.; Tsui, B. M. W.

2007-02-01

Our team is carrying on a systematic study devoted to the design of a SPECT detector with submillimeter resolution and adequate sensitivity (1 cps/kBq). Such system will be used for functional imaging of biological processes at molecular level in small animal. The system requirements have been defined by two relevant applications: study of atherosclerotic plaques characterization and stem cells diffusion and homing. In order to minimize costs and implementation time, the gamma detector will be based—as much as possible—on conventional components: scintillator crystal and position sensitive PhotoMultipliers read by individual channel electronics. A coded aperture collimator should be adapted to maximize the efficiency. The optimal selection of the detector components is investigated by systematic use of Monte-Carlo simulations (and laboratory validation tests); and finally preliminary results are presented and discussed here.

Arrays of Segmented, Tapered Light Guides for Use With Large, Planar Scintillation Detectors

NASA Astrophysics Data System (ADS)

Raylman, Raymond R.; Vaigneur, Keith; Stolin, Alexander V.; Jaliparthi, Gangadhar

2015-06-01

Metabolic imaging techniques can potentially improve detection and diagnosis of cancer in women with radiodense and/or fibrocystic breasts. Our group has previously developed a high-resolution positron emission tomography imaging and biopsy device (PEM-PET) to detect and guide the biopsy of suspicious breast lesions. Initial testing revealed that the imaging field-of-view (FOV) of the scanner was smaller than the physical size of the detector's active area, which could hinder sampling of breast areas close to the chest wall. The purpose of this work was to utilize segmented, tapered light guides for optically coupling the scintillator arrays to arrays of position-sensitive photomultipliers to increase both the active FOV and identification of individual scintillator elements. Testing of the new system revealed that the optics of these structures made it possible to discern detector elements from the complete active area of the detector face. In the previous system the top and bottom rows and left and right columns were not identifiable. Additionally, use of the new light guides increased the contrast of individual detector elements by up to 129%. Improved element identification led to a spatial resolution increase by approximately 12%. Due to attenuation of light in the light guides the detector energy resolution decreased from 18.5% to 19.1%. Overall, these improvements should increase the field-of-view and spatial resolution of the dedicated breast-PET system.

A combined time-of-flight and depth-of-interaction detector for total-body positron emission tomography.

PubMed

Berg, Eric; Roncali, Emilie; Kapusta, Maciej; Du, Junwei; Cherry, Simon R

2016-02-01

In support of a project to build a total-body PET scanner with an axial field-of-view of 2 m, the authors are developing simple, cost-effective block detectors with combined time-of-flight (TOF) and depth-of-interaction (DOI) capabilities. This work focuses on investigating the potential of phosphor-coated crystals with conventional PMT-based block detector readout to provide DOI information while preserving timing resolution. The authors explored a variety of phosphor-coating configurations with single crystals and crystal arrays. Several pulse shape discrimination techniques were investigated, including decay time, delayed charge integration (DCI), and average signal shapes. Pulse shape discrimination based on DCI provided the lowest DOI positioning error: 2 mm DOI positioning error was obtained with single phosphor-coated crystals while 3-3.5 mm DOI error was measured with the block detector module. Minimal timing resolution degradation was observed with single phosphor-coated crystals compared to uncoated crystals, and a timing resolution of 442 ps was obtained with phosphor-coated crystals in the block detector compared to 404 ps without phosphor coating. Flood maps showed a slight degradation in crystal resolvability with phosphor-coated crystals; however, all crystals could be resolved. Energy resolution was degraded by 3%-7% with phosphor-coated crystals compared to uncoated crystals. These results demonstrate the feasibility of obtaining TOF-DOI capabilities with simple block detector readout using phosphor-coated crystals.

Note: Large active area solid state photon counter with 20 ps timing resolution and 60 fs detection delay stability

NASA Astrophysics Data System (ADS)

Prochazka, Ivan; Kodet, Jan; Eckl, Johann; Blazej, Josef

2017-10-01

We are reporting on the design, construction, and performance of a photon counting detector system, which is based on single photon avalanche diode detector technology. This photon counting device has been optimized for very high timing resolution and stability of its detection delay. The foreseen application of this detector is laser ranging of space objects, laser time transfer ground to space and fundamental metrology. The single photon avalanche diode structure, manufactured on silicon using K14 technology, is used as a sensor. The active area of the sensor is circular with 200 μm diameter. Its photon detection probability exceeds 40% in the wavelength range spanning from 500 to 800 nm. The sensor is operated in active quenching and gating mode. A new control circuit was optimized to maintain high timing resolution and detection delay stability. In connection to this circuit, timing resolution of the detector is reaching 20 ps FWHM. In addition, the temperature change of the detection delay is as low as 70 fs/K. As a result, the detection delay stability of the device is exceptional: expressed in the form of time deviation, detection delay stability of better than 60 fs has been achieved. Considering the large active area aperture of the detector, this is, to our knowledge, the best timing performance reported for a solid state photon counting detector so far.

TES-Based Light Detectors for the CRESST Direct Dark Matter Search

NASA Astrophysics Data System (ADS)

Rothe, J.; Angloher, G.; Bauer, P.; Bento, A.; Bucci, C.; Canonica, L.; D'Addabbo, A.; Defay, X.; Erb, A.; Feilitzsch, F. v.; Ferreiro Iachellini, N.; Gorla, P.; Gütlein, A.; Hauff, D.; Jochum, J.; Kiefer, M.; Kluck, H.; Kraus, H.; Lanfranchi, J.-C.; Langenkämper, A.; Loebell, J.; Mancuso, M.; Mondragon, E.; Münster, A.; Pagliarone, C.; Petricca, F.; Potzel, W.; Pröbst, F.; Puig, R.; Reindl, F.; Schäffner, K.; Schieck, J.; Schipperges, V.; Schönert, S.; Seidel, W.; Stahlberg, M.; Stodolsky, L.; Strandhagen, C.; Strauss, R.; Tanzke, A.; Trinh Thi, H. H.; Türkoğlu, C.; Ulrich, A.; Usherov, I.; Wawoczny, S.; Willers, M.; Wüstrich, M.

2018-05-01

The CRESST experiment uses cryogenic detectors based on transition-edge sensors to search for dark matter interactions. Each detector module consists of a scintillating CaWO_4 crystal and a silicon-on-sapphire (SOS) light detector which operate in coincidence (phonon-light technique). The 40-mm-diameter SOS disks (2 g mass) used in the data taking campaign of CRESST-II Phase 2 (2014-2016) reached absolute baseline resolutions of σ = 4-7 eV. This is the best performance reported for cryogenic light detectors of this size. Newly developed silicon beaker light detectors (4 cm height, 4 cm diameter, 6 g mass), which cover a large fraction of the target crystal surface, have achieved a baseline resolution of σ = 5.8 eV. First results of further improved light detectors developed for the ongoing low-threshold CRESST-III experiment are presented.

Characterization of pixelated TlBr detectors with Tl electrodes

NASA Astrophysics Data System (ADS)

Hitomi, Keitaro; Onodera, Toshiyuki; Kim, Seong-Yun; Shoji, Tadayoshi; Ishii, Keizo

2014-05-01

A 4.36-mm-thick pixelated thallium bromide (TlBr) detector with Tl electrodes was fabricated from a crystal grown by the traveling molten zone method using zone-purified material. The detector had four 1×1 mm2 pixelated anodes. The detector performance was characterized at room temperature. The mobility-lifetime products of electrons for each pixel of the TlBr detector were measured to be >2.8×10-3 cm2/V. The four pixelated anodes of the detector exhibited energy resolutions of 1.5-1.8% full width at half maximum (FWHM) for 662-keV gamma rays for single-pixel events with the depth correction method. An energy resolution of 4.5% FWHM for 662-keV gamma rays was obtained from a reconstructed energy spectrum using two-pixel events from the two pixelated anodes on the detector.

Characteristics of Un doped and Europium-dopedSrI2 Scintillator Detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sturm, Benjamin; Cherepy, Nerine; Drury, Owen

2012-01-01

High energy resolution gamma-ray detectors that can be formed into relatively large sizes while operating at room temperature offer many advantages for national security applications. We are working toward that goal through the development of SrI{sub 2}(Eu) scintillator detectors, which routinely provide <;3.0% energy resolution at 662 keV with volumes >;10 cm{sup 3}. In this study, we have tested pure, undoped SrI{sub 2} to gain a better understanding of the scintillation properties and spectroscopic performance achievable without activation. An undoped crystal grown from 99.999% pure SrI{sub 2} pellets was tested for its spectroscopic performance, its light yield, and uniformity ofmore » scintillation light collection as a function of gamma-ray interaction position relative to the crystal growth direction. Undoped SrI{sub 2} was found to provide energy resolution of 5.3% at 662 keV, and the light collection nonuniformity varied by only 0.72% over the length of the crystal. Measurements of both a 3% Eu-doped and the undoped SrI{sub 2} crystal were carried out in the SLYNCI facility and indicate differences in their light yield non-proportionality. The surprisingly good scintillation properties of the pure SrI{sub 2} crystal suggests that with high-purity feedstock, further reduction of the Eu concentration can be made to grow larger crystals while not adversely impacting the spectroscopic performance.« less

Estimation of position resolution for DOI-PET detector using diameter 0.2 mm WLS fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaneko, Naomi; Ito, Hiroshi; Kawai, Hideyuki

We have been developing sub mm resolution andmore » $$ 1 million DOI-PET detector using wavelength shifting fibers (WLSF), scintillation crystals of plate shape and SiPM (MPPC: HAMAMATSU K. K.). Conventional design of DOI-PET detector is obtained about mm{sup 3} of resolution by using some blocks detecting gamma-ray in mm 3 voxel. It requires the production cost of $$ a few ten million or more for high technique of processing crystal and a lot of number of photo-devices, and this technology is reaching the limit of the resolution. Both higher resolution and lower cost of DOI-PET detector production is challenging for PET diagnosis population. We propose two type of detector. One is a whole body PET system, and the other for brain or small animal. Both PET system consist 6 blocks. the former consist of 6 layers 300 mm x 300 mm x 4 mm crystal plate. The latter consist 16 crystal layers, 4 x 4 crystal array. The size of crystal plate is 40 mm x 40 mm x 1 mm.The WLSF sheets connect to upper and lower plane. The whole PET systems connect 8 SiPMs are bonded on each side. For the brain PET, 9 WLSF fibers are bond on the each side. The expected position resolution maybe less than 1 mm at the former. We have estimation experimental performance the system using {sup 22}Na radioactive source. The collection efficiency of WLSF (R-3) sheet was achieved 10% with GAGG at 511 keV. The relation between reconstruction position and incident position is obtained linearity and achieved the resolution of 0.7 mm FWHM for x-axis of DOI by readout WLSF. (authors)« less

CdZnTe γ detector for deep inelastic neutron scattering on the VESUVIO spectrometer

NASA Astrophysics Data System (ADS)

Andreani, C.; D'Angelo, A.; Gorini, G.; Imberti, S.; Pietropaolo, A.; Rhodes, N. J.; Schooneveld, E. M.; Senesi, R.; Tardocchi, M.

In this paper it is shown that solid-state cadmium-zinc-telluride (CZT) is a promising photon detector for neutron spectroscopy in a wide energy interval, ranging from thermal ( 25 meV) to epithermal ( 70 eV) neutron energies. In the present study two CZT detectors were tested as part of the inverse-geometry neutron spectrometer VESUVIO operating at the ISIS pulsed neutron source. The response of the CZT detector to photon emission from radiative neutron capture in 238U was determined by biparametric measurements of neutron time of flight and photon energy. The scattering response function F(y) from a Pb sample has been derived using both CZT and conventional 6Li-glass scintillator detectors. The former showed both an improved signal to background ratio and higher efficiency as compared to 6Li glass, allowing us to measure F(y) up to the fourth 238U absorption energy (Er=66.02 eV). Due to the small size of CZT detectors, their use is envisaged in arrays, with high spatial resolution, for neutron-scattering studies at high energy (ω>1 eV) and low wavevector (q <10 Å-1) transfers.

Challenges of small-pixel infrared detectors: a review.

PubMed

Rogalski, A; Martyniuk, P; Kopytko, M

2016-04-01

In the last two decades, several new concepts for improving the performance of infrared detectors have been proposed. These new concepts particularly address the drive towards the so-called high operating temperature focal plane arrays (FPAs), aiming to increase detector operating temperatures, and as a consequence reduce the cost of infrared systems. In imaging systems with the above megapixel formats, pixel dimension plays a crucial role in determining critical system attributes such as system size, weight and power consumption (SWaP). The advent of smaller pixels has also resulted in the superior spatial and temperature resolution of these systems. Optimum pixel dimensions are limited by diffraction effects from the aperture, and are in turn wavelength-dependent. In this paper, the key challenges in realizing optimum pixel dimensions in FPA design including dark current, pixel hybridization, pixel delineation, and unit cell readout capacity are outlined to achieve a sufficiently adequate modulation transfer function for the ultra-small pitches involved. Both photon and thermal detectors have been considered. Concerning infrared photon detectors, the trade-offs between two types of competing technology-HgCdTe material systems and III-V materials (mainly barrier detectors)-have been investigated.

Improvement of spatial resolution in a Timepix based CdTe photon counting detector using ToT method

NASA Astrophysics Data System (ADS)

Park, Kyeongjin; Lee, Daehee; Lim, Kyung Taek; Kim, Giyoon; Chang, Hojong; Yi, Yun; Cho, Gyuseong

2018-05-01

Photon counting detectors (PCDs) have been recognized as potential candidates in X-ray radiography and computed tomography due to their many advantages over conventional energy-integrating detectors. In particular, a PCD-based X-ray system shows an improved contrast-to-noise ratio, reduced radiation exposure dose, and more importantly, exhibits a capability for material decomposition with energy binning. For some applications, a very high resolution is required, which translates into smaller pixel size. Unfortunately, small pixels may suffer from energy spectral distortions (distortion in energy resolution) due to charge sharing effects (CSEs). In this work, we propose a method for correcting CSEs by measuring the point of interaction of an incident X-ray photon by the time-of-threshold (ToT) method. Moreover, we also show that it is possible to obtain an X-ray image with a reduced pixel size by using the concept of virtual pixels at a given pixel size. To verify the proposed method, modulation transfer function (MTF) and signal-to-noise ratio (SNR) measurements were carried out with the Timepix chip combined with the CdTe pixel sensor. The X-ray test condition was set at 80 kVp with 5 μA, and a tungsten edge phantom and a lead line phantom were used for the measurements. Enhanced spatial resolution was achieved by applying the proposed method when compared to that of the conventional photon counting method. From experiment results, MTF increased from 6.3 (conventional counting method) to 8.3 lp/mm (proposed method) at 0.3 MTF. On the other hand, the SNR decreased from 33.08 to 26.85 dB due to four virtual pixels.

Micrometer-resolution imaging using MÖNCH: towards G2-less grating interferometry

PubMed Central

Cartier, Sebastian; Kagias, Matias; Bergamaschi, Anna; Wang, Zhentian; Dinapoli, Roberto; Mozzanica, Aldo; Ramilli, Marco; Schmitt, Bernd; Brückner, Martin; Fröjdh, Erik; Greiffenberg, Dominic; Mayilyan, Davit; Mezza, Davide; Redford, Sophie; Ruder, Christian; Schädler, Lukas; Shi, Xintian; Thattil, Dhanya; Tinti, Gemma; Zhang, Jiaguo; Stampanoni, Marco

2016-01-01

MÖNCH is a 25 µm-pitch charge-integrating detector aimed at exploring the limits of current hybrid silicon detector technology. The small pixel size makes it ideal for high-resolution imaging. With an electronic noise of about 110 eV r.m.s., it opens new perspectives for many synchrotron applications where currently the detector is the limiting factor, e.g. inelastic X-ray scattering, Laue diffraction and soft X-ray or high-resolution color imaging. Due to the small pixel pitch, the charge cloud generated by absorbed X-rays is shared between neighboring pixels for most of the photons. Therefore, at low photon fluxes, interpolation algorithms can be applied to determine the absorption position of each photon with a resolution of the order of 1 µm. In this work, the characterization results of one of the MÖNCH prototypes are presented under low-flux conditions. A custom interpolation algorithm is described and applied to the data to obtain high-resolution images. Images obtained in grating interferometry experiments without the use of the absorption grating G2 are shown and discussed. Perspectives for the future developments of the MÖNCH detector are also presented. PMID:27787252

Improving the spectral resolution of flat-field concave grating miniature spectrometers by dividing a wide spectral band into two narrow ones.

PubMed

Zhou, Qian; Pang, Jinchao; Li, Xinghui; Ni, Kai; Tian, Rui

2015-11-10

In this study, a new flat-field concave grating miniature spectrometer is proposed with improved resolution across a wide spectral band. A mirror is added to a conventional concave grating spectrometer and placed near the existing detector array, allowing a wide spectral band to be divided into two adjacent subspectral bands. One of these bands is directly detected by the detector, and the other is indirectly analyzed by the same detector after being reflected by the mirror. These two subspectral bands share the same entrance slit, concave grating, and detector, which allows for a compact size, while maintaining an improved spectral resolution across the entire spectral band. The positions of the mirror and other parameters of the spectrometer are designed by a computer procedure and the optical design software ZEMAX. Simulation results show that the resolution of this kind of flat-field concave grating miniature spectrometer is better than 1.6 nm across a spectral band of 700 nm. Experiments based on three laser sources reveal that the measured resolutions are comparable to the simulated ones, with a maximum relative error between them of less than 19%.

Choice of crystal surface finishing for a dual-ended readout depth-of-interaction (DOI) detector.

PubMed

Fan, Peng; Ma, Tianyu; Wei, Qingyang; Yao, Rutao; Liu, Yaqiang; Wang, Shi

2016-02-07

The objective of this study was to choose the crystal surface finishing for a dual-ended readout (DER) DOI detector. Through Monte Carlo simulations and experimental studies, we evaluated 4 crystal surface finishing options as combinations of crystal surface polishing (diffuse or specular) and reflector (diffuse or specular) options on a DER detector. We also tested one linear and one logarithm DOI calculation algorithm. The figures of merit used were DOI resolution, DOI positioning error, and energy resolution. Both the simulation and experimental results show that (1) choosing a diffuse type in either surface polishing or reflector would improve DOI resolution but degrade energy resolution; (2) crystal surface finishing with a diffuse polishing combined with a specular reflector appears a favorable candidate with a good balance of DOI and energy resolution; and (3) the linear and logarithm DOI calculation algorithms show overall comparable DOI error, and the linear algorithm was better for photon interactions near the ends of the crystal while the logarithm algorithm was better near the center. These results provide useful guidance in DER DOI detector design in choosing the crystal surface finishing and DOI calculation methods.

Study of near-stability nuclei populated as fission fragments in heavy-ion fusion reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fotiadis, Nikolaos; Nelson, Ronald O; Devlin, Matthew

2010-01-01

Examples are presented to illustrate the power of prompt {gamma}-ray spectroscopy of fission fragments from compound nuclei with A {approx} 200 formed in fusion-evaporation reactions in experiments using the Gammasphere Ge-detector array. Complementary methods, such as Coulomb excitation and deep-inelastic processes, are also discussed. In other cases (n, xn{gamma}) reactions on stable isotopes have been used to establish neutron excitation functions for {gamma}-rays using a pulsed 'white'-neutron source, coupled to a high-energy-resolution germanium-detector array. The excitation functions can unambiguously assign {gamma}-rays to a specific reaction product. Results from all these methods bridge the gaps in the systematics of high-spin statesmore » between the neutron-deficient and neutron-rich nuclei. Results near shell closures should motivate new shell model calculations.« less

Response function of single crystal synthetic diamond detectors to 1-4 MeV neutrons for spectroscopy of D plasmas

NASA Astrophysics Data System (ADS)

Rebai, M.; Giacomelli, L.; Milocco, A.; Nocente, M.; Rigamonti, D.; Tardocchi, M.; Camera, F.; Cazzaniga, C.; Chen, Z. J.; Du, T. F.; Fan, T. S.; Giaz, A.; Hu, Z. M.; Marchi, T.; Peng, X. Y.; Gorini, G.

2016-11-01

A Single-crystal Diamond (SD) detector prototype was installed at Joint European Torus (JET) in 2013 and the achieved results have shown its spectroscopic capability of measuring 2.5 MeV neutrons from deuterium plasmas. This paper presents measurements of the SD response function to monoenergetic neutrons, which is a key point for the development of a neutron spectrometer based on SDs and compares them with Monte Carlo simulations. The analysis procedure allows for a good reconstruction of the experimental results. The good pulse height energy resolution (equivalent FWHM of 80 keV at 2.5 MeV), gain stability, insensitivity to magnetic field, and compact size make SDs attractive as compact neutron spectrometers of high flux deuterium plasmas, such as for instance those needed for the ITER neutron camera.

Timing Performance of TlBr Detectors

NASA Astrophysics Data System (ADS)

Hitomi, Keitaro; Tada, Tsutomu; Onodera, Toshiyuki; Shoji, Tadayoshi; Kim, Seong-Yun; Xu, Yuanlai; Ishii, Keizo

2013-08-01

The timing performance of TlBr detectors was evaluated at room temperature (22 °C). 0.5-mm-thick planar TlBr detectors with Tl circular electrodes with a diameter of 3 mm were fabricated from TlBr crystals grown by the traveling molten zone method using a zone-purified material. The pulse rise time of the TlBr detector was measured using a digital oscilloscope as the cathode surface of the device was irradiated with a 22Na gamma-ray source. Coincidence timing spectra were obtained between the TlBr detector and a BaF2 scintillation detector when both detectors were irradiated with 511 keV positron annihilation gamma-rays. The timing resolution of the TlBr detector was found to be inversely proportional to the applied bias voltage. The TlBr detector, in coincidence with the BaF2 detector, exhibited timing resolutions characterized by a 6.5 ns full width at half maximum (FWHM) and an 8.5 ns FWHM with and without an energy window of 350 keV-560 keV, respectively.

Estimating Cosmic-Ray Spectral Parameters from Simulated Detector Responses with Detector Design Implications

NASA Technical Reports Server (NTRS)

Howell, L. W.

2001-01-01

A simple power law model consisting of a single spectral index (alpha-1) is believed to be an adequate description of the galactic cosmic-ray (GCR) proton flux at energies below 10(exp 13) eV, with a transition at knee energy (E(sub k)) to a steeper spectral index alpha-2 > alpha-1 above E(sub k). The maximum likelihood procedure is developed for estimating these three spectral parameters of the broken power law energy spectrum from simulated detector responses. These estimates and their surrounding statistical uncertainty are being used to derive the requirements in energy resolution, calorimeter size, and energy response of a proposed sampling calorimeter for the Advanced Cosmic-ray Composition Experiment for the Space Station (ACCESS). This study thereby permits instrument developers to make important trade studies in design parameters as a function of the science objectives, which is particularly important for space-based detectors where physical parameters, such as dimension and weight, impose rigorous practical limits to the design envelope.

Characterization of NaI crystal scintillators for the COHERENT collaboration

NASA Astrophysics Data System (ADS)

Erkela, Eric; Coherent Collaboration

2017-09-01

The COHERENT project aims to make a first observation of Coherent Elastic Neutrino-Nucleus Scattering (CEvNS) using a set of complimentary detector arrays located at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. Using NaI scintillators acquired from the DHS-ASP program, we plan to construct a multi-tonne array with the capacity to detect CEvNS even in the presence of moderate background. Such an array would also have sensitivity to charged-current scattering of the SNS' pion Decay-At-Rest neutrinos with potential application to neutrinoless double-beta decay nuclear matrix element calculations. Optimization of the array design requires detailed characterization of the NaI scintillators themselves. We will show results on measurements of the light response and its linearity, as well as the energy resolution as a function of detector voltage. We also measured detector thresholds, dynamic range, and spatial and temporal variation of the detector response. This work is supported by the University of Washington Royalty Research Fund.

Toward the Era of a One-Stop Imaging Service Using an Angiography Suite for Neurovascular Disorders

PubMed Central

Hung, Sheng-Che; Lin, Chung-Jung; Chang, Feng-Chi; Luo, Chao-Bao; Teng, Michael Mu-Huo; Chang, Cheng-Yen

2013-01-01

Transportation of patients requiring multiple diagnostic and imaging-guided therapeutic modalities is unavoidable in current radiological practice. This clinical scenario causes time delays and increased risk in the management of stroke and other neurovascular emergencies. Since the emergence of flat-detector technology in imaging practice in recent decades, studies have proven that flat-detector X-ray angiography in conjunction with contrast medium injection and specialized reconstruction algorithms can provide not only high-quality and high-resolution CT-like images but also functional information. This improvement in imaging technology allows quantitative assessment of intracranial hemodynamics and, subsequently in the same imaging session, provides treatment guidance for patients with neurovascular disorders by using only a flat-detector angiographic suite—a so-called one-stop quantitative imaging service (OSIS). In this paper, we review the recent developments in the field of flat-detector imaging and share our experience of applying this technology in neurovascular disorders such as acute ischemic stroke, cerebral aneurysm, and stenoocclusive carotid diseases. PMID:23762863

Performance of a SiPM based semi-monolithic scintillator PET detector

NASA Astrophysics Data System (ADS)

Zhang, Xianming; Wang, Xiaohui; Ren, Ning; Kuang, Zhonghua; Deng, Xinhan; Fu, Xin; Wu, San; Sang, Ziru; Hu, Zhanli; Liang, Dong; Liu, Xin; Zheng, Hairong; Yang, Yongfeng

2017-10-01

A depth encoding PET detector module using semi-monolithic scintillation crystal single-ended readout by a SiPM array was built and its performance was measured. The semi-monolithic scintillator detector consists of 11 polished LYSO slices measuring 1  ×  11.6  ×  10 mm3. The slices are glued together with enhanced specular reflector (ESR) in between and outside of the slices. The bottom surface of the slices is coupled to a 4  ×  4 SiPM array with a 1 mm light guide and silicon grease between them. No reflector is used on the top surface and two sides of the slices to reduce the scintillation photon reflection. The signals of the 4  ×  4 SiPM array are grouped along rows and columns separately into eight signals. Four SiPM column signals are used to identify the slices according to the center of the gravity of the scintillation photon distribution in the pixelated direction. Four SiPM row signals are used to estimate the y (monolithic direction) and z (depth of interaction) positions according to the center of the gravity and the width of the scintillation photon distribution in the monolithic direction, respectively. The detector was measured with 1 mm sampling interval in both the y and z directions with electronic collimation by using a 0.25 mm diameter 22Na point source and a 1  ×  1  ×  20 mm3 LYSO crystal detector. An average slice based energy resolution of 14.9% was obtained. All slices of 1 mm thick were clearly resolved and a detector with even thinner slices could be used. The y positions calculated with the center of gravity method are different for interactions happening at the same y, but different z positions due to depth dependent edge effects. The least-square minimization and the maximum likelihood positioning algorithms were developed and both methods improved the spatial resolution at the edges of the detector as compared with the center of gravity method. A mean absolute error (MAE) which is defined as the probability-weighted mean of the absolute value of the positioning error is used to evaluate the spatial resolution. An average MAE spatial resolution of ~1.15 mm was obtained in both y and z directions without rejection of the multiple scattering events. The average MAE spatial resolution was ~0.7 mm in both y and z directions after the multiple scattering events were rejected. The timing resolution of the detector is 575 ps. In the next step, long rectangle detector will be built to reduce edge effects and improve the spatial resolution of the semi-monolithic detector. Thick detector up to 20 mm will be explored and the positioning algorithms will be further optimized.

Performance of a SiPM based semi-monolithic scintillator PET detector.

PubMed

Zhang, Xianming; Wang, Xiaohui; Ren, Ning; Kuang, Zhonghua; Deng, Xinhan; Fu, Xin; Wu, San; Sang, Ziru; Hu, Zhanli; Liang, Dong; Liu, Xin; Zheng, Hairong; Yang, Yongfeng

2017-09-21

A depth encoding PET detector module using semi-monolithic scintillation crystal single-ended readout by a SiPM array was built and its performance was measured. The semi-monolithic scintillator detector consists of 11 polished LYSO slices measuring 1  ×  11.6  ×  10 mm 3 . The slices are glued together with enhanced specular reflector (ESR) in between and outside of the slices. The bottom surface of the slices is coupled to a 4  ×  4 SiPM array with a 1 mm light guide and silicon grease between them. No reflector is used on the top surface and two sides of the slices to reduce the scintillation photon reflection. The signals of the 4  ×  4 SiPM array are grouped along rows and columns separately into eight signals. Four SiPM column signals are used to identify the slices according to the center of the gravity of the scintillation photon distribution in the pixelated direction. Four SiPM row signals are used to estimate the y (monolithic direction) and z (depth of interaction) positions according to the center of the gravity and the width of the scintillation photon distribution in the monolithic direction, respectively. The detector was measured with 1 mm sampling interval in both the y and z directions with electronic collimation by using a 0.25 mm diameter 22 Na point source and a 1  ×  1  ×  20 mm 3 LYSO crystal detector. An average slice based energy resolution of 14.9% was obtained. All slices of 1 mm thick were clearly resolved and a detector with even thinner slices could be used. The y positions calculated with the center of gravity method are different for interactions happening at the same y, but different z positions due to depth dependent edge effects. The least-square minimization and the maximum likelihood positioning algorithms were developed and both methods improved the spatial resolution at the edges of the detector as compared with the center of gravity method. A mean absolute error (MAE) which is defined as the probability-weighted mean of the absolute value of the positioning error is used to evaluate the spatial resolution. An average MAE spatial resolution of ~1.15 mm was obtained in both y and z directions without rejection of the multiple scattering events. The average MAE spatial resolution was ~0.7 mm in both y and z directions after the multiple scattering events were rejected. The timing resolution of the detector is 575 ps. In the next step, long rectangle detector will be built to reduce edge effects and improve the spatial resolution of the semi-monolithic detector. Thick detector up to 20 mm will be explored and the positioning algorithms will be further optimized.

A novel method to calibrate DOI function of a PET detector with a dual-ended-scintillator readout.

PubMed

Shao, Yiping; Yao, Rutao; Ma, Tianyu

2008-12-01

The detection of depth-of-interaction (DOI) is a critical detector capability to improve the PET spatial resolution uniformity across the field-of-view and will significantly enhance, in particular, small bore system performance for brain, breast, and small animal imaging. One promising technique of DOI detection is to use dual-ended-scintillator readout that uses two photon sensors to detect scintillation light from both ends of a scintillator array and estimate DOI based on the ratio of signals (similar to Anger logic). This approach needs a careful DOI function calibration to establish accurate relationship between DOI and signal ratios, and to recalibrate if the detection condition is shifted due to the drift of sensor gain, bias variations, or degraded optical coupling, etc. However, the current calibration method that uses coincident events to locate interaction positions inside a single scintillator crystal has severe drawbacks, such as complicated setup, long and repetitive measurements, and being prone to errors from various possible misalignments among the source and detector components. This method is also not practically suitable to calibrate multiple DOI functions of a crystal array. To solve these problems, a new method has been developed that requires only a uniform flood source to irradiate a crystal array without the need to locate the interaction positions, and calculates DOI functions based solely on the uniform probability distribution of interactions over DOI positions without knowledge or assumption of detector responses. Simulation and experiment have been studied to validate the new method, and the results show that the new method, with a simple setup and one single measurement, can provide consistent and accurate DOI functions for the entire array of multiple scintillator crystals. This will enable an accurate, simple, and practical DOI function calibration for the PET detectors based on the design of dual-ended-scintillator readout. In addition, the new method can be generally applied to calibrating other types of detectors that use the similar dual-ended readout to acquire the radiation interaction position.

A novel method to calibrate DOI function of a PET detector with a dual-ended-scintillator readout

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shao Yiping; Yao Rutao; Ma Tianyu

The detection of depth-of-interaction (DOI) is a critical detector capability to improve the PET spatial resolution uniformity across the field-of-view and will significantly enhance, in particular, small bore system performance for brain, breast, and small animal imaging. One promising technique of DOI detection is to use dual-ended-scintillator readout that uses two photon sensors to detect scintillation light from both ends of a scintillator array and estimate DOI based on the ratio of signals (similar to Anger logic). This approach needs a careful DOI function calibration to establish accurate relationship between DOI and signal ratios, and to recalibrate if the detectionmore » condition is shifted due to the drift of sensor gain, bias variations, or degraded optical coupling, etc. However, the current calibration method that uses coincident events to locate interaction positions inside a single scintillator crystal has severe drawbacks, such as complicated setup, long and repetitive measurements, and being prone to errors from various possible misalignments among the source and detector components. This method is also not practically suitable to calibrate multiple DOI functions of a crystal array. To solve these problems, a new method has been developed that requires only a uniform flood source to irradiate a crystal array without the need to locate the interaction positions, and calculates DOI functions based solely on the uniform probability distribution of interactions over DOI positions without knowledge or assumption of detector responses. Simulation and experiment have been studied to validate the new method, and the results show that the new method, with a simple setup and one single measurement, can provide consistent and accurate DOI functions for the entire array of multiple scintillator crystals. This will enable an accurate, simple, and practical DOI function calibration for the PET detectors based on the design of dual-ended-scintillator readout. In addition, the new method can be generally applied to calibrating other types of detectors that use the similar dual-ended readout to acquire the radiation interaction position.« less

Development of High Resolution Mirrors and Cd-Zn-Te Detectors for Hard X-ray Astronomy

NASA Technical Reports Server (NTRS)

Ramsey, Brian D.; Speegle, Chet O.; Gaskin, Jessica; Sharma, Dharma; Engelhaupt, Darell; Six, N. Frank (Technical Monitor)

2002-01-01

We describe the fabrication and implementation of a high-resolution conical, grazing- incidence, hard X-ray (20-70 keV) telescope. When flown aboard stratospheric balloons, these mirrors are used to image cosmic sources such as supernovae, neutron stars, and quasars. The fabrication process involves generating super-polished mandrels, mirror shell electroforming, and mirror testing. The cylindrical mandrels consist of two conical segments; each segment is approximately 305 mm long. These mandrels are first, precision ground to within approx. 1.0 micron straightness along each conical segment and then lapped and polished to less than 0.5 micron straightness. Each mandrel segment is the super-polished to an average surface roughness of approx. 3.25 angstrom rms. By mirror shell replication, this combination of good figure and low surface roughness has enabled us to achieve 15 arcsec, confirmed by X-ray measurements in the Marshall Space Flight Center 102 meter test facility. To image the focused X-rays requires a focal plane detector with appropriate spatial resolution. For 15 arcsec optics of 6 meter focal length, this resolution must be around 200 microns. In addition, the detector must have a high efficiency, relatively high energy resolution, and low background. We are currently developing Cadmium-Zinc-Telluride fine-pixel detectors for this purpose. The detectors under study consist of a 16x16 pixel array with a pixel pitch of 300 microns and are 1 mm and 2 mm thick. At 60 keV, the measured energy resolution is around 2%.

MR-compatibility of a high-resolution small animal PET insert operating inside a 7 T MRI.

PubMed

Thiessen, J D; Shams, E; Stortz, G; Schellenberg, G; Bishop, D; Khan, M S; Kozlowski, P; Retière, F; Sossi, V; Thompson, C J; Goertzen, A L

2016-11-21

A full-ring PET insert consisting of 16 PET detector modules was designed and constructed to fit within the 114 mm diameter gradient bore of a Bruker 7 T MRI. The individual detector modules contain two silicon photomultiplier (SiPM) arrays, dual-layer offset LYSO crystal arrays, and high-definition multimedia interface (HDMI) cables for both signal and power transmission. Several different RF shielding configurations were assessed prior to construction of a fully assembled PET insert using a combination of carbon fibre and copper foil for RF shielding. MR-compatibility measurements included field mapping of the static magnetic field (B 0 ) and the time-varying excitation field (B 1 ) as well as acquisitions with multiple pulse sequences: spin echo (SE), rapid imaging with refocused echoes (RARE), fast low angle shot (FLASH) gradient echo, and echo planar imaging (EPI). B 0 field maps revealed a small degradation in the mean homogeneity (+0.1 ppm) when the PET insert was installed and operating. No significant change was observed in the B 1 field maps or the image homogeneity of various MR images, with a 9% decrease in the signal-to-noise ratio (SNR) observed only in EPI images acquired with the PET insert installed and operating. PET detector flood histograms, photopeak amplitudes, and energy resolutions were unchanged in individual PET detector modules when acquired during MRI operation. There was a small baseline shift on the PET detector signals due to the switching amplifiers used to power MRI gradient pulses. This baseline shift was observable when measured with an oscilloscope and varied as a function of the gradient duty cycle, but had no noticeable effect on the performance of the PET detector modules. Compact front-end electronics and effective RF shielding led to minimal cross-interference between the PET and MRI systems. Both PET detector and MRI performance was excellent, whether operating as a standalone system or a hybrid PET/MRI.

MR-compatibility of a high-resolution small animal PET insert operating inside a 7 T MRI

NASA Astrophysics Data System (ADS)

Thiessen, J. D.; Shams, E.; Stortz, G.; Schellenberg, G.; Bishop, D.; Khan, M. S.; Kozlowski, P.; Retière, F.; Sossi, V.; Thompson, C. J.; Goertzen, A. L.

2016-11-01

A full-ring PET insert consisting of 16 PET detector modules was designed and constructed to fit within the 114 mm diameter gradient bore of a Bruker 7 T MRI. The individual detector modules contain two silicon photomultiplier (SiPM) arrays, dual-layer offset LYSO crystal arrays, and high-definition multimedia interface (HDMI) cables for both signal and power transmission. Several different RF shielding configurations were assessed prior to construction of a fully assembled PET insert using a combination of carbon fibre and copper foil for RF shielding. MR-compatibility measurements included field mapping of the static magnetic field (B 0) and the time-varying excitation field (B 1) as well as acquisitions with multiple pulse sequences: spin echo (SE), rapid imaging with refocused echoes (RARE), fast low angle shot (FLASH) gradient echo, and echo planar imaging (EPI). B 0 field maps revealed a small degradation in the mean homogeneity (+0.1 ppm) when the PET insert was installed and operating. No significant change was observed in the B 1 field maps or the image homogeneity of various MR images, with a 9% decrease in the signal-to-noise ratio (SNR) observed only in EPI images acquired with the PET insert installed and operating. PET detector flood histograms, photopeak amplitudes, and energy resolutions were unchanged in individual PET detector modules when acquired during MRI operation. There was a small baseline shift on the PET detector signals due to the switching amplifiers used to power MRI gradient pulses. This baseline shift was observable when measured with an oscilloscope and varied as a function of the gradient duty cycle, but had no noticeable effect on the performance of the PET detector modules. Compact front-end electronics and effective RF shielding led to minimal cross-interference between the PET and MRI systems. Both PET detector and MRI performance was excellent, whether operating as a standalone system or a hybrid PET/MRI.

Detailed characterization of low background β-delayed proton detector

NASA Astrophysics Data System (ADS)

Janasik, Molly; Friedman, Moshe; Budner, Tamas; Wrede, Chris

2017-09-01

In order to determine the rates of two important reactions for the astrophysical rapid proton (rp) capture process, a segmented, low background β-delayed proton detector has been built at NSCL. The detector is currently in the process of being optimized. A detailed characterization of the detector's Micromegas pad plane is being performed using measurements with a radioactive 55Fe x-ray calibration source. A fitting routine has been developed to extract the energy resolution from the spectra. First results of detector resolution with P10 gas will be presented. This work is supported by the U.S. National Science Foundation under Award Nos. PHY-1102511 and PHY- 1565546 and the U.S. Department of Energy, Office of Science, under Award No. DE-SC0016052.

X-ray photon correlation spectroscopy using a fast pixel array detector with a grid mask resolution enhancer.

PubMed

Hoshino, Taiki; Kikuchi, Moriya; Murakami, Daiki; Harada, Yoshiko; Mitamura, Koji; Ito, Kiminori; Tanaka, Yoshihito; Sasaki, Sono; Takata, Masaki; Jinnai, Hiroshi; Takahara, Atsushi

2012-11-01

The performance of a fast pixel array detector with a grid mask resolution enhancer has been demonstrated for X-ray photon correlation spectroscopy (XPCS) measurements to investigate fast dynamics on a microscopic scale. A detecting system, in which each pixel of a single-photon-counting pixel array detector, PILATUS, is covered by grid mask apertures, was constructed for XPCS measurements of silica nanoparticles in polymer melts. The experimental results are confirmed to be consistent by comparison with other independent experiments. By applying this method, XPCS measurements can be carried out by customizing the hole size of the grid mask to suit the experimental conditions, such as beam size, detector size and sample-to-detector distance.

DQE simulation of a-Se x-ray detectors using ARTEMIS

NASA Astrophysics Data System (ADS)

Fang, Yuan; Badano, Aldo

2016-03-01

Detective Quantum Efficiency (DQE) is one of the most important image quality metrics for evaluating the spatial resolution performance of flat-panel x-ray detectors. In this work, we simulate the DQE of amorphous selenium (a-Se) xray detectors with a detailed Monte Carlo transport code (ARTEMIS) for modeling semiconductor-based direct x-ray detectors. The transport of electron-hole pairs is achieved with a spatiotemporal model that accounts for recombination and trapping of carriers and Coulombic effects of space charge and external applied electric field. A range of x-ray energies has been simulated from 10 to 100 keV. The DQE results can be used to study the spatial resolution characteristics of detectors at different energies.

Gamma-ray tracking method for pet systems

DOEpatents

Mihailescu, Lucian; Vetter, Kai M.

2010-06-08

Gamma-ray tracking methods for use with granular, position sensitive detectors identify the sequence of the interactions taking place in the detector and, hence, the position of the first interaction. The improved position resolution in finding the first interaction in the detection system determines a better definition of the direction of the gamma-ray photon, and hence, a superior source image resolution. A PET system using such a method will have increased efficiency and position resolution.

PET Timing Performance Measurement Method Using NEMA NEC Phantom

NASA Astrophysics Data System (ADS)

Wang, Gin-Chung; Li, Xiaoli; Niu, Xiaofeng; Du, Huini; Balakrishnan, Karthik; Ye, Hongwei; Burr, Kent

2016-06-01

When comparing the performance of time-of-flight whole-body PET scanners, timing resolution is one important benchmark. Timing performance is heavily influenced by detector and electronics design. Even for the same scanner design, measured timing resolution is a function of many factors including the activity concentration, geometry and positioning of the radioactive source. Due to lack of measurement standards, the timing resolutions reported in the literature may not be directly comparable and may not describe the timing performance under clinically relevant conditions. In this work we introduce a method which makes use of the data acquired during the standard NEMA Noise-Equivalent-Count-Rate (NECR) measurements, and compare it to several other timing resolution measurement methods. The use of the NEMA NEC phantom, with well-defined dimensions and radioactivity distribution, is attractive because it has been widely accepted in the industry and allows for the characterization of timing resolution across a more relevant range of conditions.

Advanced Scintillator Detectors for Neutron Imaging in Inertial Confinement Fusion

NASA Astrophysics Data System (ADS)

Geppert-Kleinrath, Verena; Danly, Christopher; Merrill, Frank; Simpson, Raspberry; Volegov, Petr; Wilde, Carl

2016-10-01

The neutron imaging team at Los Alamos National Laboratory (LANL) has been providing two-dimensional neutron imaging of the inertial confinement fusion process at the National Ignition Facility (NIF) for over five years. Neutron imaging is a powerful tool in which position-sensitive detectors register neutrons emitted in the fusion reactions, producing a picture of the burning fuel. Recent images have revealed possible multi-dimensional asymmetries, calling for additional views to facilitate three-dimensional imaging. These will be along shorter lines of sight to stay within the existing facility at NIF. In order to field imaging capabilities equivalent to the existing system several technological challenges have to be met: high spatial resolution, high light output, and fast scintillator response to capture lower-energy neutrons, which have scattered from non-burning regions of fuel. Deuterated scintillators are a promising candidate to achieve the timing and resolution required; a systematic study of deuterated and non-deuterated polystyrene and liquid samples is currently ongoing. A test stand has been implemented to measure the response function, and preliminary data on resolution and light output have been obtained at the LANL Weapons Neutrons Research facility.

A Study of a Mini-Drift GEM Tracking Detector

NASA Astrophysics Data System (ADS)

Azmoun, B.; DiRuzza, B.; Franz, A.; Kiselev, A.; Pak, R.; Phipps, M.; Purschke, M. L.; Woody, C.

2016-06-01

A GEM tracking detector with an extended drift region has been studied as part of an effort to develop new tracking detectors for future experiments at RHIC and for the Electron Ion Collider that is being planned for BNL or JLAB. The detector consists of a triple GEM stack with a 1.6 cm drift region that was operated in a mini TPC type configuration. Both the position and arrival time of the charge deposited in the drift region were measured on the readout plane which allowed the reconstruction of a short vector for the track traversing the chamber. The resulting position and angle information from the vector could then be used to improve the position resolution of the detector for larger angle tracks, which deteriorates rapidly with increasing angle for conventional GEM tracking detectors using only charge centroid information. Two types of readout planes were studied. One was a COMPASS style readout plane with 400 μm pitch XY strips and the other consisted of 2 × 10 mm2 chevron pads. The detector was studied in test beams at Fermilab and CERN, along with additional measurements in the lab, in order to determine its position and angular resolution for incident track angles up to 45 degrees. Several algorithms were studied for reconstructing the vector using the position and timing information in order to optimize the position and angular resolution of the detector for the different readout planes. Applications for large angle tracking detectors at RHIC and EIC are also discussed.

Investigation of runaway electron dissipation in DIII-D using a gamma ray imager

NASA Astrophysics Data System (ADS)

Lvovskiy, A.; Paz-Soldan, C.; Eidietis, N.; Pace, D.; Taussig, D.

2017-10-01

We report the findings of a novel gamma ray imager (GRI) to study runaway electron (RE) dissipation in the quiescent regime on the DIII-D tokamak. The GRI measures the bremsstrahlung emission by RE providing information on RE energy spectrum and distribution across a poloidal cross-section. It consists of a lead pinhole camera illuminating a matrix of BGO detectors placed in the DIII-D mid-plane. The number of detectors was recently doubled to provide better spatial resolution and additional detector shielding was implemented to reduce un-collimated gamma flux and increase single-to-noise ratio. Under varying loop voltage, toroidal magnetic field and plasma density, a non-monotonic RE distribution function has been revealed as a result of the interplay between electric field, synchrotron radiation and collisional damping. A fraction of the high-energy RE population grows forming a bump at the RE distribution function while synchrotron radiation decreases. A possible destabilizing effect of Parail-Pogutse instability on the RE population will be also discussed. Work supported by the US DOE under DE-FC02-04ER54698.

Xenon gamma-ray detector for ecological applications

NASA Astrophysics Data System (ADS)

Novikov, Alexander S.; Ulin, Sergey E.; Chernysheva, Irina V.; Dmitrenko, Valery V.; Grachev, Victor M.; Petrenko, Denis V.; Shustov, Alexander E.; Uteshev, Ziyaetdin M.; Vlasik, Konstantin F.

2015-01-01

A description of the xenon detector (XD) for ecological applications is presented. The detector provides high energy resolution and is able to operate under extreme environmental conditions (wide temperature range and unfavorable acoustic action). Resistance to acoustic noise as well as improvement in energy resolution has been achieved by means of real-time digital pulse processing. Another important XD feature is the ionization chamber's thin wall with composite housing, which significantly decreases the mass of the device and expands its energy range, especially at low energies.

High Resolution PET Imaging Probe for the Detection, Molecular Characterization and Treatment Monitoring of Prostate Cancer

DTIC Science & Technology

2012-07-01

number of high resolution PET experiments including the dual-ring small field- of-view configuration shown at left in Figure 5 . The benchtop system...detectors having 26 x 40 arrays of 1mm x 1mm x 1mm detector elements is shown at right in Figure 5 . Detectors used for probe experiments shown in...Figure 13). In the series of experiments geared towards PET application, but with the results applicable to the present single gamma case, we have

Image-based Modeling of PSF Deformation with Application to Limited Angle PET Data

PubMed Central

Matej, Samuel; Li, Yusheng; Panetta, Joseph; Karp, Joel S.; Surti, Suleman

2016-01-01

The point-spread-functions (PSFs) of reconstructed images can be deformed due to detector effects such as resolution blurring and parallax error, data acquisition geometry such as insufficient sampling or limited angular coverage in dual-panel PET systems, or reconstruction imperfections/simplifications. PSF deformation decreases quantitative accuracy and its spatial variation lowers consistency of lesion uptake measurement across the imaging field-of-view (FOV). This can be a significant problem with dual panel PET systems even when using TOF data and image reconstruction models of the detector and data acquisition process. To correct for the spatially variant reconstructed PSF distortions we propose to use an image-based resolution model (IRM) that includes such image PSF deformation effects. Originally the IRM was mostly used for approximating data resolution effects of standard PET systems with full angular coverage in a computationally efficient way, but recently it was also used to mitigate effects of simplified geometric projectors. Our work goes beyond this by including into the IRM reconstruction imperfections caused by combination of the limited angle, parallax errors, and any other (residual) deformation effects and testing it for challenging dual panel data with strongly asymmetric and variable PSF deformations. We applied and tested these concepts using simulated data based on our design for a dedicated breast imaging geometry (B-PET) consisting of dual-panel, time-of-flight (TOF) detectors. We compared two image-based resolution models; i) a simple spatially invariant approximation to PSF deformation, which captures only the general PSF shape through an elongated 3D Gaussian function, and ii) a spatially variant model using a Gaussian mixture model (GMM) to more accurately capture the asymmetric PSF shape in images reconstructed from data acquired with the B-PET scanner geometry. Results demonstrate that while both IRMs decrease the overall uptake bias in the reconstructed image, the second one with the spatially variant and accurate PSF shape model is also able to ameliorate the spatially variant deformation effects to provide consistent uptake results independent of the lesion location within the FOV. PMID:27812222

Report of the x ray and gamma ray sensors panel

NASA Technical Reports Server (NTRS)

Szymkowiak, Andrew; Collins, S.; Kurfess, J.; Mahoney, W.; Mccammon, D.; Pehl, R.; Ricker, G.

1991-01-01

Overall five major areas of technology are recommended for development in order to meet the science requirements of the Astrotech 21 mission set. These are: detectors for high resolution gamma ray spectroscopy, cryogenic detectors for improved x ray spectral and spatial resolution, advanced x ray charge coupled devices (CCDs) for higher energy resolution and larger format, extension to higher energies, liquid and solid position sensitive detectors for improving stopping power in the energy range 5 to 500 keV and 0.2 to 2 MeV. Development plans designed to achieve the desired capabilities on the time scales required by the technology freeze dates have been recommended in each of these areas.

Evaluation of Timepix3 based CdTe photon counting detector for fully spectroscopic small animal SPECT imaging

NASA Astrophysics Data System (ADS)

Trojanova, E.; Jakubek, J.; Turecek, D.; Sykora, V.; Francova, P.; Kolarova, V.; Sefc, L.

2018-01-01

The imaging method of SPECT (Single Photon Emission Computed Tomography) is used in nuclear medicine for diagnostics of various diseases or organs malfunctions. The distribution of medically injected, inhaled, or ingested radionuclides (radiotracers) in the patient body is imaged using gamma-ray sensitive camera with suitable imaging collimator. The 3D image is then calculated by combining many images taken from different observation angles. Most of SPECT systems use scintillator based cameras. These cameras do not provide good energy resolution and do not allow efficient suppression of unwanted signals such as those caused by Compton scattering. The main goal of this work is evaluation of Timepix3 detector properties for SPECT method for functional imaging of small animals during preclinical studies. Advantageous Timepix3 properties such as energy and spatial resolution are exploited for significant image quality improvement. Preliminary measurements were performed on specially prepared plastic phantom with cavities filled by radioisotopes and then repeated with in vivo mouse sample.

First results from the NEMO Test Site

NASA Astrophysics Data System (ADS)

Riccobene, Giorgio; NEMO Collaboration

2007-03-01

The NEMO (NEutrino Mediterranean Observatory) Collaboration is constructing, 25 km E from Catania (Sicily) at 2000 m depth, an underwater test site to perform long-term tests of prototypes and new technologies for an underwater high energy neutrino detector in the Mediterranean Sea. In this framework the collaboration deployed and operated an experimental apparatus for on-line monitoring of deep-sea noise. The station is equipped with 4 hydrophones operational in the range 30 Hz - 40 kHz. This interval of frequencies matches the range suitable for acoustic detection of high energy neutrino-induced showers in water. Hydrophone signals are digitized underwater at 96 kHz sampling frequency and 24 bits resolution. A custom software was developed to record data on high resolution 4-channels PCM .le. Data are used to model underwater acoustic noise as a function of frequency and time, a mandatory parametre for future acoustic neutrino detectors. Results indicate that the average noise in the site is compatible with noise produced in condition of sea surface agitation (sea state.)

Image construction from the IRAS survey and data fusion

NASA Technical Reports Server (NTRS)

Bontekoe, Tj. R.

1990-01-01

The IRAS survey data can be used successfully to produce images of extended objects. The major difficulty, viz. non-uniform sampling, different response functions for each detector, and varying signal-to-noise levels for each detector for each scan, were resolved. The results of three different image construction techniques are compared: co-addition, constrained least squares, and maximum entropy. The maximum entropy result is superior. An image of the galaxy M51 with an average spatial resolution of 45 arc seconds, is presented using 60 micron survey data. This exceeds the telescope diffraction limit of 1 minute of arc, at this wavelength. Data fusion is a proposed method for combining data from different instruments, with different spatial resolutions, at different wavelengths. Direct estimates of the physical parameters, temperature, density and composition, can be made from the data without prior images (re-)construction. An increase in the accuracy of these parameters is expected as the result of this more systematic approach.

Speckle interferometry. Data acquisition and control for the SPID instrument.

NASA Astrophysics Data System (ADS)

Altarac, S.; Tallon, M.; Thiebaut, E.; Foy, R.

1998-08-01

SPID (SPeckle Imaging by Deconvolution) is a new speckle camera currently under construction at CRAL-Observatoire de Lyon. Its high spectral resolution and high image restoration capabilities open new astrophysical programs. The instrument SPID is composed of four main optical modules which are fully automated and computer controlled by a software written in Tcl/Tk/Tix and C. This software provides an intelligent assistance to the user by choosing observational parameters as a function of atmospheric parameters, computed in real time, and the desired restored image quality. Data acquisition is made by a photon-counting detector (CP40). A VME-based computer under OS9 controls the detector and stocks the data. The intelligent system runs under Linux on a PC. A slave PC under DOS commands the motors. These 3 computers communicate through an Ethernet network. SPID can be considered as a precursor for VLT's (Very Large Telescope, four 8-meter telescopes currently built in Chile by European Southern Observatory) very high spatial resolution camera.

Performance evaluation of a two detector camera for real-time video.

PubMed

Lochocki, Benjamin; Gambín-Regadera, Adrián; Artal, Pablo

2016-12-20

Single pixel imaging can be the preferred method over traditional 2D-array imaging in spectral ranges where conventional cameras are not available. However, when it comes to real-time video imaging, single pixel imaging cannot compete with the framerates of conventional cameras, especially when high-resolution images are desired. Here we evaluate the performance of an imaging approach using two detectors simultaneously. First, we present theoretical results on how low SNR affects final image quality followed by experimentally determined results. Obtained video framerates were doubled compared to state of the art systems, resulting in a framerate from 22 Hz for a 32×32 resolution to 0.75 Hz for a 128×128 resolution image. Additionally, the two detector imaging technique enables the acquisition of images with a resolution of 256×256 in less than 3 s.

An efficient and cost-effective microchannel plate detector for slow neutron radiography

NASA Astrophysics Data System (ADS)

Wiggins, B. B.; Vadas, J.; Bancroft, D.; deSouza, Z. O.; Huston, J.; Hudan, S.; Baxter, D. V.; deSouza, R. T.

2018-05-01

A novel approach for efficiently imaging objects with slow neutrons in two dimensions is realized. Neutron sensitivity is achieved by use of a boron doped microchannel plate (MCP). The resulting electron avalanche is further amplified with a Z-stack MCP before being sensed by two orthogonally oriented wire planes. Coupling of the wire planes to delay lines efficiently encodes the position information as a time difference. To determine the position resolution, slow neutrons were used to illuminate a Cd-mask placed directly in front of the detector. Peaks in the resulting spectrum exhibited an average peak width of 329 μm FWHM, corresponding to an average intrinsic resolution of 216 μm. The center region of the detector exhibits a significantly better spatial resolution with an intrinsic resolution of <100 μm observed.

Direct Visualization of Local Electromagnetic Field Structures by Scanning Transmission Electron Microscopy.

PubMed

Shibata, Naoya; Findlay, Scott D; Matsumoto, Takao; Kohno, Yuji; Seki, Takehito; Sánchez-Santolino, Gabriel; Ikuhara, Yuichi

2017-07-18

The functional properties of materials and devices are critically determined by the electromagnetic field structures formed inside them, especially at nanointerface and surface regions, because such structures are strongly associated with the dynamics of electrons, holes and ions. To understand the fundamental origin of many exotic properties in modern materials and devices, it is essential to directly characterize local electromagnetic field structures at such defect regions, even down to atomic dimensions. In recent years, rapid progress in the development of high-speed area detectors for aberration-corrected scanning transmission electron microscopy (STEM) with sub-angstrom spatial resolution has opened new possibilities to directly image such electromagnetic field structures at very high-resolution. In this Account, we give an overview of our recent development of differential phase contrast (DPC) microscopy for aberration-corrected STEM and its application to many materials problems. In recent years, we have developed segmented-type STEM detectors which divide the detector plane into 16 segments and enable simultaneous imaging of 16 STEM images which are sensitive to the positions and angles of transmitted/scattered electrons on the detector plane. These detectors also have atomic-resolution imaging capability. Using these segmented-type STEM detectors, we show DPC STEM imaging to be a very powerful tool for directly imaging local electromagnetic field structures in materials and devices in real space. For example, DPC STEM can clearly visualize the local electric field variation due to the abrupt potential change across a p-n junction in a GaAs semiconductor, which cannot be observed by normal in-focus bright-field or annular type dark-field STEM imaging modes. DPC STEM is also very effective for imaging magnetic field structures in magnetic materials, such as magnetic domains and skyrmions. Moreover, real-time imaging of electromagnetic field structures can now be realized through very fast data acquisition, processing, and reconstruction algorithms. If we use DPC STEM for atomic-resolution imaging using a sub-angstrom size electron probe, it has been shown that we can directly observe the atomic electric field inside atoms within crystals and even inside single atoms, the field between the atomic nucleus and the surrounding electron cloud, which possesses information about the atomic species, local chemical bonding and charge redistribution between bonded atoms. This possibility may open an alternative way for directly visualizing atoms and nanostructures, that is, seeing atoms as an entity of electromagnetic fields that reflect the intra- and interatomic electronic structures. In this Account, the current status of aberration-corrected DPC STEM is highlighted, along with some applications in real material and device studies.

Fundamental Performance Improvement of Microwave Kinetic Inductance Detectors for UVOIR Astrophysics

NASA Astrophysics Data System (ADS)

Mazin, Benjamin

Ultraviolet, Optical, and near-Infrared Microwave Kinetic Inductance Detectors (UVOIR MKIDs) are one of the most powerful new technologies to emerge out of the NASA APRA detectors program in the last decade. This proposal seeks to build on previous APRA grants to drastically improve the performance of UVOIR MKIDs. Like an X-ray microcalorimeter ultraviolet, optical, and near-IR (UVOIR) MKIDs are cryogenic detectors capable of detecting single photons and measuring their energy without filters or gratings. Our team has created this technology from the ground up, and fielded a 2024-pixel UVOIR MKID array on five separate observing runs at 5-m class telescopes. With 34 observing nights successfully completed and two astronomy papers published using MKID data (the first astronomy papers published using MKID data at any wavelength), UVOIR MKIDs are at TRL 5-6 for ground-based astronomy, and TRL 3 for space-based astronomy. The outstanding potential of these detectors was recognized in the recent NASA long term vision, "Enduring Quests, Daring Visions'', which recognized on page 88 that MKIDs have tremendous potential for future NASA UVOIR space missions, especially for finding Earth twins around nearby stars: "..microwave kinetic inductance detectors (MKIDs) would be a game-changing capability..''. Current UVOIR MKIDs feature array sizes in the 10-30 kpix range, energy resolution R=16 at 254 nm, ~70% pixel yield, and quantum efficiency that goes from 70% in the UV to 25% in the near-IR. These arrays, fabricated out of Titanium Nitride (TiN) on a high resistivity silicon substrate, are fully functional for ground-based science. However, our current MKIDs are far away from their theoretical limits, especially in yield (70% vs. 100%) and energy resolution (R=10 vs. R=100 at 400 nm). The yield is of especially urgent concern as missing pixels make accurate photometry difficult, especially for rapidly time variable sources like compact binaries that we have been studying. The yield is low because the reactively sputtered TiN that we make our MKIDs from is extremely sensitive to deposition conditions, and the resistivity and hence resonant frequency of the MKIDs varies dramatically across a wafer, as shown in. Our energy resolution is low because of a combination of factors related to the MKID material and the two level system (TLS) noise from our capacitors. In order to improve our current energy resolution, yield, and quantum efficiency we need to move in new directions. This proposal will focus on two main improvements: making better MKID resonator materials, and making lower noise capacitors.

Hard X-ray and low-energy gamma-ray spectrometers

NASA Technical Reports Server (NTRS)

Gehrels, N.; Crannell, C. J.; Orwig, L. E.; Forrest, D. J.; Lin, R. P.; Starr, R.

1988-01-01

Basic principles of operation and characteristics of scintillation and semi-conductor detectors used for solar hard X-ray and gamma-ray spectrometers are presented. Scintillation materials such as NaI offer high stopping power for incident gamma rays, modest energy resolution, and relatively simple operation. They are, to date, the most often used detector in solar gamma-ray spectroscopy. The scintillator BGO has higher stopping power than NaI, but poorer energy resolution. The primary advantage of semi-conductor materials such as Ge is their high-energy resolution. Monte-Carlo simulations of the response of NaI and Ge detectors to model solar flare inputs show the benefit of high resoluton for studying spectral lines. No semi-conductor material besides Ge is currently available with adequate combined size and purity to make general-use hard X-ray and gamma-ray detectors for solar studies.

A two-dimensional intensified photodiode array for imaging spectroscopy

NASA Technical Reports Server (NTRS)

Tennyson, P. D.; Dymond, K.; Moos, H. W.; Feldman, P. D.; Mackey, E. F.

1986-01-01

The Johns Hopkins University is currently developing an instrument to fly aboard NASA's Space Shuttle as a Spartan payload in the late 1980s. This Spartan free flyer will obtain spatially resolved spectra of faint extended emission line objects in the wavelength range 750-1150 A at about 2-A resolution. The use of two-dimensional photon counting detectors will give simultaneous coverage of the 400 A spectral range and the 9 arc-minute spatial resolution along the spectrometer slit. The progress towards the flight detector is reported here with preliminary results from a laboratory breadboard detector, and a comparison with the one-dimensional detector developed for the Hopkins Ultraviolet Telescope. A hardware digital centroiding algorithm has been successfully implemented. The system is ultimately capable of 15-micron resolution in two dimensions at the image plane and can handle continuous counting rates of up to 8000 counts/s.

Recent technologic advances in multi-detector row cardiac CT.

PubMed

Halliburton, Sandra Simon

2009-11-01

Recent technical advances in multi-detector row CT have resulted in lower radiation dose, improved temporal and spatial resolution, decreased scan time, and improved tissue differentiation. Lower radiation doses have resulted from the use of pre-patient z collimators, the availability of thin-slice axial data acquisition, the increased efficiency of ECG-based tube current modulation, and the implementation of iterative reconstruction algorithms. Faster gantry rotation and the simultaneous use of two x-ray sources have led to improvements in temporal resolution, and gains in spatial resolution have been achieved through application of the flying x-ray focal-spot technique in the z-direction. Shorter scan times have resulted from the design of detector arrays with increasing numbers of detector rows and through the simultaneous use of two x-ray sources to allow higher helical pitch. Some improvement in tissue differentiation has been achieved with dual energy CT. This article discusses these recent technical advances in detail.

Relativistic astrophysics. [design analysis and performance tests of Cerenkov counters for detection of iron isotopes

NASA Technical Reports Server (NTRS)

Price, P. B.

1976-01-01

The design, experimental testing, and calibration (error analysis) of a high resolution Cerenkov-scintillation detector is presented. The detector is capable of detecting iron isotopes and heavy ions of cosmic rays, and of performing direct measurements of individual neighboring isotopes at charge resolution 26. It utilizes Lexan (trademark) sheets, and has been used in flight packages of balloons and on the Skylab. The detector will be able to provide more information on violet astrophysical processes, such as thermonuclear reactions on neutron stars. Ground support and display equipment which are to be used in conjunction with the detector are also discussed.

Design and performance of a large area neutron sensitive anger camera

DOE PAGES

Visscher, Theodore; Montcalm, Christopher A.; Donahue, Jr., Cornelius; ...

2015-05-21

We describe the design and performance of a 157mm x 157mm two dimensional neutron detector. The detector uses the Anger principle to determine the position of neutrons. We have verified FWHM resolution of < 1.2mm with distortion < 0.5mm on over 50 installed Anger Cameras. The performance of the detector is limited by the light yield of the scintillator, and it is estimated that the resolution of the current detector could be doubled with a brighter scintillator. Data collected from small (<1mm 3) single crystal reference samples at the single crystal instrument TOPAZ provide results with low R w(F) values

A line-source method for aligning on-board and other pinhole SPECT systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Susu; Bowsher, James; Yin, Fang-Fang

2013-12-15

Purpose: In order to achieve functional and molecular imaging as patients are in position for radiation therapy, a robotic multipinhole SPECT system is being developed. Alignment of the SPECT system—to the linear accelerator (LINAC) coordinate frame and to the coordinate frames of other on-board imaging systems such as cone-beam CT (CBCT)—is essential for target localization and image reconstruction. An alignment method that utilizes line sources and one pinhole projection is proposed and investigated to achieve this goal. Potentially, this method could also be applied to the calibration of the other pinhole SPECT systems.Methods: An alignment model consisting of multiple alignmentmore » parameters was developed which maps line sources in three-dimensional (3D) space to their two-dimensional (2D) projections on the SPECT detector. In a computer-simulation study, 3D coordinates of line-sources were defined in a reference room coordinate frame, such as the LINAC coordinate frame. Corresponding 2D line-source projections were generated by computer simulation that included SPECT blurring and noise effects. The Radon transform was utilized to detect angles (α) and offsets (ρ) of the line-source projections. Alignment parameters were then estimated by a nonlinear least squares method, based on the α and ρ values and the alignment model. Alignment performance was evaluated as a function of number of line sources, Radon transform accuracy, finite line-source width, intrinsic camera resolution, Poisson noise, and acquisition geometry. Experimental evaluations were performed using a physical line-source phantom and a pinhole-collimated gamma camera attached to a robot.Results: In computer-simulation studies, when there was no error in determining angles (α) and offsets (ρ) of the measured projections, six alignment parameters (three translational and three rotational) were estimated perfectly using three line sources. When angles (α) and offsets (ρ) were provided by the Radon transform, estimation accuracy was reduced. The estimation error was associated with rounding errors of Radon transform, finite line-source width, Poisson noise, number of line sources, intrinsic camera resolution, and detector acquisition geometry. Statistically, the estimation accuracy was significantly improved by using four line sources rather than three and by thinner line-source projections (obtained by better intrinsic detector resolution). With five line sources, median errors were 0.2 mm for the detector translations, 0.7 mm for the detector radius of rotation, and less than 0.5° for detector rotation, tilt, and twist. In experimental evaluations, average errors relative to a different, independent registration technique were about 1.8 mm for detector translations, 1.1 mm for the detector radius of rotation (ROR), 0.5° and 0.4° for detector rotation and tilt, respectively, and 1.2° for detector twist.Conclusions: Alignment parameters can be estimated using one pinhole projection of line sources. Alignment errors are largely associated with limited accuracy of the Radon transform in determining angles (α) and offsets (ρ) of the line-source projections. This alignment method may be important for multipinhole SPECT, where relative pinhole alignment may vary during rotation. For pinhole and multipinhole SPECT imaging on-board radiation therapy machines, the method could provide alignment of SPECT coordinates with those of CBCT and the LINAC.« less

A line-source method for aligning on-board and other pinhole SPECT systems

PubMed Central

Yan, Susu; Bowsher, James; Yin, Fang-Fang

2013-01-01

Purpose: In order to achieve functional and molecular imaging as patients are in position for radiation therapy, a robotic multipinhole SPECT system is being developed. Alignment of the SPECT system—to the linear accelerator (LINAC) coordinate frame and to the coordinate frames of other on-board imaging systems such as cone-beam CT (CBCT)—is essential for target localization and image reconstruction. An alignment method that utilizes line sources and one pinhole projection is proposed and investigated to achieve this goal. Potentially, this method could also be applied to the calibration of the other pinhole SPECT systems. Methods: An alignment model consisting of multiple alignment parameters was developed which maps line sources in three-dimensional (3D) space to their two-dimensional (2D) projections on the SPECT detector. In a computer-simulation study, 3D coordinates of line-sources were defined in a reference room coordinate frame, such as the LINAC coordinate frame. Corresponding 2D line-source projections were generated by computer simulation that included SPECT blurring and noise effects. The Radon transform was utilized to detect angles (α) and offsets (ρ) of the line-source projections. Alignment parameters were then estimated by a nonlinear least squares method, based on the α and ρ values and the alignment model. Alignment performance was evaluated as a function of number of line sources, Radon transform accuracy, finite line-source width, intrinsic camera resolution, Poisson noise, and acquisition geometry. Experimental evaluations were performed using a physical line-source phantom and a pinhole-collimated gamma camera attached to a robot. Results: In computer-simulation studies, when there was no error in determining angles (α) and offsets (ρ) of the measured projections, six alignment parameters (three translational and three rotational) were estimated perfectly using three line sources. When angles (α) and offsets (ρ) were provided by the Radon transform, estimation accuracy was reduced. The estimation error was associated with rounding errors of Radon transform, finite line-source width, Poisson noise, number of line sources, intrinsic camera resolution, and detector acquisition geometry. Statistically, the estimation accuracy was significantly improved by using four line sources rather than three and by thinner line-source projections (obtained by better intrinsic detector resolution). With five line sources, median errors were 0.2 mm for the detector translations, 0.7 mm for the detector radius of rotation, and less than 0.5° for detector rotation, tilt, and twist. In experimental evaluations, average errors relative to a different, independent registration technique were about 1.8 mm for detector translations, 1.1 mm for the detector radius of rotation (ROR), 0.5° and 0.4° for detector rotation and tilt, respectively, and 1.2° for detector twist. Conclusions: Alignment parameters can be estimated using one pinhole projection of line sources. Alignment errors are largely associated with limited accuracy of the Radon transform in determining angles (α) and offsets (ρ) of the line-source projections. This alignment method may be important for multipinhole SPECT, where relative pinhole alignment may vary during rotation. For pinhole and multipinhole SPECT imaging on-board radiation therapy machines, the method could provide alignment of SPECT coordinates with those of CBCT and the LINAC. PMID:24320537

A line-source method for aligning on-board and other pinhole SPECT systems.

PubMed

Yan, Susu; Bowsher, James; Yin, Fang-Fang

2013-12-01

In order to achieve functional and molecular imaging as patients are in position for radiation therapy, a robotic multipinhole SPECT system is being developed. Alignment of the SPECT system-to the linear accelerator (LINAC) coordinate frame and to the coordinate frames of other on-board imaging systems such as cone-beam CT (CBCT)-is essential for target localization and image reconstruction. An alignment method that utilizes line sources and one pinhole projection is proposed and investigated to achieve this goal. Potentially, this method could also be applied to the calibration of the other pinhole SPECT systems. An alignment model consisting of multiple alignment parameters was developed which maps line sources in three-dimensional (3D) space to their two-dimensional (2D) projections on the SPECT detector. In a computer-simulation study, 3D coordinates of line-sources were defined in a reference room coordinate frame, such as the LINAC coordinate frame. Corresponding 2D line-source projections were generated by computer simulation that included SPECT blurring and noise effects. The Radon transform was utilized to detect angles (α) and offsets (ρ) of the line-source projections. Alignment parameters were then estimated by a nonlinear least squares method, based on the α and ρ values and the alignment model. Alignment performance was evaluated as a function of number of line sources, Radon transform accuracy, finite line-source width, intrinsic camera resolution, Poisson noise, and acquisition geometry. Experimental evaluations were performed using a physical line-source phantom and a pinhole-collimated gamma camera attached to a robot. In computer-simulation studies, when there was no error in determining angles (α) and offsets (ρ) of the measured projections, six alignment parameters (three translational and three rotational) were estimated perfectly using three line sources. When angles (α) and offsets (ρ) were provided by the Radon transform, estimation accuracy was reduced. The estimation error was associated with rounding errors of Radon transform, finite line-source width, Poisson noise, number of line sources, intrinsic camera resolution, and detector acquisition geometry. Statistically, the estimation accuracy was significantly improved by using four line sources rather than three and by thinner line-source projections (obtained by better intrinsic detector resolution). With five line sources, median errors were 0.2 mm for the detector translations, 0.7 mm for the detector radius of rotation, and less than 0.5° for detector rotation, tilt, and twist. In experimental evaluations, average errors relative to a different, independent registration technique were about 1.8 mm for detector translations, 1.1 mm for the detector radius of rotation (ROR), 0.5° and 0.4° for detector rotation and tilt, respectively, and 1.2° for detector twist. Alignment parameters can be estimated using one pinhole projection of line sources. Alignment errors are largely associated with limited accuracy of the Radon transform in determining angles (α) and offsets (ρ) of the line-source projections. This alignment method may be important for multipinhole SPECT, where relative pinhole alignment may vary during rotation. For pinhole and multipinhole SPECT imaging on-board radiation therapy machines, the method could provide alignment of SPECT coordinates with those of CBCT and the LINAC.

Plastic scintillation detectors for precision Time-of-Flight measurements of relativistic heavy ions

NASA Astrophysics Data System (ADS)

Lin, Wen-Jian; Zhao, Jian-Wei; Sun, Bao-Hua; He, Liu-Chun; Lin, Wei-Ping; Liu, Chuan-Ye; Tanihata, Isao; Terashima, Satoru; Tian, Yi; Wang, Feng; Wang, Meng; Zhang, Guang-Xin; Zhang, Xue-Heng; Zhu, Li-Hua; Duan, Li-Min; Hu, Rong-Jiang; Liu, Zhong; Lu, Chen-Gui; Ren, Pei-Pei; Sheng, Li-Na; Sun, Zhi-Yu; Wang, Shi-Tao; Wang, Tao-Feng; Xu, Zhi-Guo; Zheng, Yong

2017-06-01

Plastic scintillation detectors for Time-of-Flight (TOF) measurements are almost essential for event-by-event identification of relativistic rare isotopes. In this work, a pair of plastic scintillation detectors of dimensions 50 × 50 × 3t mm3 and 80 × 100 × 3t mm3 have been set up at the External Target Facility (ETF), Institute of Modern Physics (IMP). Their time, energy and position responses are measured with the 18O primary beam at 400 MeV/nucleon. After off-line corrections for walk effect and position, the time resolutions of the two detectors are determined to be 27 ps (σ) and 36 ps (σ), respectively. Both detectors have nearly the same energy resolution of 3.1% (σ) and position resolution of about 3.4 mm (σ). The detectors have been used successfully in nuclear reaction cross section measurements, and will be be employed for upgrading the RIBLL2 beam line at IMP as well as for the high energy branch at HIAF. Supported by National Natural Science Foundation of China (11475014,11235002) and National Key Research and Development Program (2016YFA0400500)

Cryogenic phonon-scintillation detectors with PMT readout for rare event search experiments

NASA Astrophysics Data System (ADS)

Zhang, X.; Lin, J.; Mikhailik, V. B.; Kraus, H.

2016-06-01

Cryogenic phonon-scintillation detectors (CPSD) for rare event search experiments require reliable, efficient and robust photon detectors that can resolve individual photons in a scintillation event. We report on a cryogenic detector containing a scintillating crystal, equipped with an NTD-Ge phonon sensor and a photon detector based on a low-temperature photomultiplier tube (PMT) that is powered by a Cockcroft-Walton generator. Here we present results from the characterisation of two detector modules, one with CaWO4, the other with CaMoO4 as scintillator. The energy resolutions (FWHM) at 122.1 keV for the scintillation/PMT channel are 19.9% and 29.7% respectively for CaWO4 and CaMoO4 while the energy resolutions (FWHM) for the phonon channels are 2.17 keV (1.8%) and 0.97 keV (0.79%). These characteristics compare favourably with other CPSDs currently used in cryogenic rare-event search experiments. The detection module with PMT readout benefits from the implementation of a well-understood, reliable, and commercially available component and improved time resolution, while retaining the major advantages of conventional CPSD, such as high sensitivity, resolving power and discrimination ability.

The Tunable XUV Imager (TXI) Sounding Rocket Payload

NASA Technical Reports Server (NTRS)

Brinton, John (Technical Monitor); Golub, Leon

2004-01-01

The TXI was flown successfully on 21 June 2001 (36.199 US). All systems functioned as planned and image data were acquired and sent to the ground. Unfortunately, due to a parachute failure the payload was destroyed. In this report we summarize results from the flight and provide detailed information on the high resolution X-ray imaging detector which was developed as part of the program.

A versatile indirect detector design for hard X-ray microimaging

NASA Astrophysics Data System (ADS)

Douissard, P.-A.; Cecilia, A.; Rochet, X.; Chapel, X.; Martin, T.; van de Kamp, T.; Helfen, L.; Baumbach, T.; Luquot, L.; Xiao, X.; Meinhardt, J.; Rack, A.

2012-09-01

Indirect X-ray detectors are of outstanding importance for high resolution imaging, especially at synchrotron light sources: while consisting mostly of components which are widely commercially available, they allow for a broad range of applications in terms of the X-ray energy employed, radiation dose to the detector, data acquisition rate and spatial resolving power. Frequently, an indirect detector consists of a thin-film single crystal scintillator and a high-resolution visible light microscope as well as a camera. In this article, a novel modular-based indirect design is introduced, which offers several advantages: it can be adapted for different cameras, i.e. different sensor sizes, and can be trimmed to work either with (quasi-)monochromatic illumination and the correspondingly lower absorbed dose or with intense white beam irradiation. In addition, it allows for a motorized quick exchange between different magnifications / spatial resolutions. Developed within the European project SCINTAX, it is now commercially available. The characteristics of the detector in its different configurations (i.e. for low dose or for high dose irradiation) as measured within the SCINTAX project will be outlined. Together with selected applications from materials research, non-destructive evaluation and life sciences they underline the potential of this design to make high resolution X-ray imaging widely available.

Active Radiation Detectors for Use in Space Beyond Low Earth Orbit: Spatial and Energy Resolution Requirements and Methods for Heavy Ion Charge Classification

NASA Astrophysics Data System (ADS)

McBeth, Rafe A.

Space radiation exposure to astronauts will need to be carefully monitored on future missions beyond low earth orbit. NASA has proposed an updated radiation risk framework that takes into account a significant amount of radiobiological and heavy ion track structure information. These models require active radiation detection systems to measure the energy and ion charge Z. However, current radiation detection systems cannot meet these demands. The aim of this study was to investigate several topics that will help next generation detection systems meet the NASA objectives. Specifically, this work investigates the required spatial resolution to avoid coincident events in a detector, the effects of energy straggling and conversion of dose from silicon to water, and methods for ion identification (Z) using machine learning. The main results of this dissertation are as follows: 1. Spatial resolution on the order of 0.1 cm is required for active space radiation detectors to have high confidence in identifying individual particles, i.e., to eliminate coincident events. 2. Energy resolution of a detector system will be limited by energy straggling effects and the conversion of dose in silicon to dose in biological tissue (water). 3. Machine learning methods show strong promise for identification of ion charge (Z) with simple detector designs.

CMOS-TDI detector technology for reconnaissance application

NASA Astrophysics Data System (ADS)

Eckardt, Andreas; Reulke, Ralf; Jung, Melanie; Sengebusch, Karsten

2014-10-01

The Institute of Optical Sensor Systems (OS) at the Robotics and Mechatronics Center of the German Aerospace Center (DLR) has more than 30 years of experience with high-resolution imaging technology. This paper shows the institute's scientific results of the leading-edge detector design CMOS in a TDI (Time Delay and Integration) architecture. This project includes the technological design of future high or multi-spectral resolution spaceborne instruments and the possibility of higher integration. DLR OS and the Fraunhofer Institute for Microelectronic Circuits and Systems (IMS) in Duisburg were driving the technology of new detectors and the FPA design for future projects, new manufacturing accuracy and on-chip processing capability in order to keep pace with the ambitious scientific and user requirements. In combination with the engineering research, the current generation of space borne sensor systems is focusing on VIS/NIR high spectral resolution to meet the requirements on earth and planetary observation systems. The combination of large-swath and high-spectral resolution with intelligent synchronization control, fast-readout ADC (analog digital converter) chains and new focal-plane concepts opens the door to new remote-sensing and smart deep-space instruments. The paper gives an overview of the detector development status and verification program at DLR, as well as of new control possibilities for CMOS-TDI detectors in synchronization control mode.

Method for improving the angular resolution of a neutron scatter camera

DOEpatents

Mascarenhas, Nicholas; Marleau, Peter; Gerling, Mark; Cooper, Robert Lee; Mrowka, Stanley; Brennan, James S.

2012-12-25

An instrument that will directly image the fast fission neutrons from a special nuclear material source wherein the neutron detection efficiency is increased has been described. Instead of the previous technique that uses a time-of-flight (TOF) between 2 widely spaced fixed planes of neutron detectors to measure scatter neutron kinetic energy, we now use the recoil proton energy deposited in the second of the 2 scatter planes which can now be repositioned either much closer together or further apart. However, by doubling the separation distance between the 2 planes from 20 cm to a distance of 40 cm we improved the angular resolution of the detector from about 12.degree. to about 10.degree.. A further doubling of the separation distance to 80 cm provided an addition improvement in angular resolution of the detector to about 6.degree. without adding additional detectors or ancillary electronics. The distance between planes also may be dynamically changed using a suitable common technique such as a gear- or motor-drive to toggle between the various positions. The angular resolution of this new configuration, therefore, is increased at the expanse of detection sensitivity. However, the diminished sensitivity may be acceptable for those applications where the detector is able to interrogate a particular site for an extended period.

Spatial resolution of a hard x-ray CCD detector.

PubMed

Seely, John F; Pereira, Nino R; Weber, Bruce V; Schumer, Joseph W; Apruzese, John P; Hudson, Lawrence T; Szabo, Csilla I; Boyer, Craig N; Skirlo, Scott

2010-08-10

The spatial resolution of an x-ray CCD detector was determined from the widths of the tungsten x-ray lines in the spectrum formed by a crystal spectrometer in the 58 to 70 keV energy range. The detector had 20 microm pixel, 1700 by 1200 pixel format, and a CsI x-ray conversion scintillator. The spectral lines from a megavolt x-ray generator were focused on the spectrometer's Rowland circle by a curved transmission crystal. The line shapes were Lorentzian with an average width after removal of the natural and instrumental line widths of 95 microm (4.75 pixels). A high spatial frequency background, primarily resulting from scattered gamma rays, was removed from the spectral image by Fourier analysis. The spectral lines, having low spatial frequency in the direction perpendicular to the dispersion, were enhanced by partially removing the Lorentzian line shape and by fitting Lorentzian curves to broad unresolved spectral features. This demonstrates the ability to improve the spectral resolution of hard x-ray spectra that are recorded by a CCD detector with well-characterized intrinsic spatial resolution.

A full range detector for the HIRRBS high resolution RBS magnetic spectrometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skala, Wayne G.; Haberl, Arthur W.; Bakhru, Hassaram

2013-04-19

The UAlbany HIRRBS (High Resolution RBS) system has been updated for better use in rapid analysis. The focal plane detector now covers the full range from U down to O using a linear stepper motor to translate the 1-cm detector across the 30-cm range. Input is implemented with zero-back-angle operation in all cases. The chamber has been modified to allow for quick swapping of sample holders, including a channeling goniometer. A fixed standard surface-barrier detector allows for normal RBS simultaneously with use of the magnetic spectrometer. The user can select a region on the standard spectrum or can select anmore » element edge or an energy point for collection of the expanded spectrum portion. The best resolution currently obtained is about 2-to-3 keV, probably representing the energy width of the incoming beam. Calibration is maintained automatically for any spectrum portion and any beam energy from 1.0 to 3.5 MeV. Element resolving power, sensitivity and depth resolution are shown using several examples. Examples also show the value of simultaneous conventional RBS.« less

New concepts for scintillator/HgI[sub 2] gamma ray spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Y.J.; Iwanczyk, J.S.; Patt, B.E.

The construction of a high energy resolution gamma ray detector consisting of a scintillator/mercuric iodide photodetector combination has been investigated. Several HgI[sub 2] photodetectors have been fabricated and tested with standard NIM electronics. The energy resolution of a scintillator/HgI[sub 2] pair was found to be 4.75%, full width at half maximum, for 662 keV [sup 137]Cs gamma ray photons. Of five detectors fabricated with the new technique, all produced resolutions better than 5.6% FWHM. This technology makes it possible to reliably produce high quality HgI[sub 2] photodetectors. New design concepts for the HgI[sub 2] photocell, including the transparent entrance electrode,more » detector geometry, and detector packaging, are described in the paper. Advantages of gamma ray spectrometers based upon crystal scintillators optically coupled to HgI[sub 2] photodetectors (in contrast to coupling the scintillators to the more conventional light sensors, i.e., photomultiplier tubes (PMTs)) include greater ruggedness, improved energy resolution, markedly smaller size and weight, reduced power, and insensitivity to magnetic field perturbations.« less

Position sensitivity by light splitting in scintillator arrays

NASA Astrophysics Data System (ADS)

Bisplinghoff, J.; Bollmann, R.; Cloth, P.; Dohrmann, F.; Dorner, G.; Drüke, V.; Ernst, J.; Eversheim, P. D.; Filges, D.; Gasthuber, M.; Gebel, R.; Groβ, A.; Groβ-Hardt, R.; Hinterberger, F.; Jahn, R.; Kühl, L.; Lahr, U.; Langkau, R.; Lippert, G.; Mayer-Kuckuk, T.; Maschuw, R.; Mertler, G.; Metsch, B.; Mosel, F.; Paetz gen. Schieck, H.; Petry, H. R.; Prasuhn, D.; Przewoski, B. v.; Rohdjeβ, H.; Rosendaal, D.; Rossen, P. v.; Scheid, H.; Schirm, N.; Schwandt, F.; Scobel, W.; Sprute, L.; Stein, H.; Theis, D.; Weber, J.; Wiedmann, W.; Woller, K.; Ziegler, R.; EDDA Collaboration

1993-05-01

A novel detector design of overlapping plastic scintillator elements in cylindrical geometry has been developed for detection of low multiplicity events of fast protons and other light charged particles: each particle traversing the detector from the axis outwards will produce light in several elements. The relative amounts of energy deposited in those elements allow one to interpolate on the particle trajectory beyond the resolution given by the granularity. The detector covers the angular range 10° ≤ Θlab ≤ 72° and 0° ≤ ϕ ≤ 360° with an inner layer of scintillator bars of triangular cross section and an outer layer of rings. The material is BC408. Tests with minimum ionizing electron beams show that spatial resolutions of ΔΘlab ≈ 1.5° and Δϕ12 ≈ 1.5° (FWHM) can be obtained for electrons or proton pairs with energies in the GeV range. In the EDDA experiment the ultimate spatial resolution is then determined by the size of the interaction area rather than by the intrinsic pulse height resolution of the detector.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pablant, N. A.; Delgado-Aparicio, L.; Bitter, M.

A new energy resolving x-ray pinhole camera has been recently installed on Alcator C-Mod. This diagnostic is capable of 1D or 2D imaging with a spatial resolution of Almost-Equal-To 1 cm, an energy resolution of Almost-Equal-To 1 keV in the range of 3.5-15 keV and a maximum time resolution of 5 ms. A novel use of a Pilatus 2 hybrid-pixel x-ray detector [P. Kraft et al., J. Synchrotron Rad. 16, 368 (2009)] is employed in which the lower energy threshold of individual pixels is adjusted, allowing regions of a single detector to be sensitive to different x-ray energy ranges. Developmentmore » of this new detector calibration technique was done as a collaboration between PPPL and Dectris Ltd. The calibration procedure is described, and the energy resolution of the detector is characterized. Initial data from this installation on Alcator C-Mod is presented. This diagnostic provides line-integrated measurements of impurity emission which can be used to determine impurity concentrations as well as the electron energy distribution.« less

Novel energy resolving x-ray pinhole camera on Alcator C-Mod.

PubMed

Pablant, N A; Delgado-Aparicio, L; Bitter, M; Brandstetter, S; Eikenberry, E; Ellis, R; Hill, K W; Hofer, P; Schneebeli, M

2012-10-01

A new energy resolving x-ray pinhole camera has been recently installed on Alcator C-Mod. This diagnostic is capable of 1D or 2D imaging with a spatial resolution of ≈1 cm, an energy resolution of ≈1 keV in the range of 3.5-15 keV and a maximum time resolution of 5 ms. A novel use of a Pilatus 2 hybrid-pixel x-ray detector [P. Kraft et al., J. Synchrotron Rad. 16, 368 (2009)] is employed in which the lower energy threshold of individual pixels is adjusted, allowing regions of a single detector to be sensitive to different x-ray energy ranges. Development of this new detector calibration technique was done as a collaboration between PPPL and Dectris Ltd. The calibration procedure is described, and the energy resolution of the detector is characterized. Initial data from this installation on Alcator C-Mod is presented. This diagnostic provides line-integrated measurements of impurity emission which can be used to determine impurity concentrations as well as the electron energy distribution.

Achieving subpixel resolution with time-correlated transient signals in pixelated CdZnTe gamma-ray sensors using a focused laser beam (Conference Presentation)

NASA Astrophysics Data System (ADS)

Ocampo Giraldo, Luis A.; Bolotnikov, Aleksey E.; Camarda, Giuseppe S.; Cui, Yonggang; De Geronimo, Gianluigi; Gul, Rubi; Fried, Jack; Hossain, Anwar; Unlu, Kenan; Vernon, Emerson; Yang, Ge; James, Ralph B.

2017-05-01

High-resolution position-sensitive detectors have been proposed to correct response non-uniformities in Cadmium Zinc Telluride (CZT) crystals by virtually subdividing the detectors area into small voxels and equalizing responses from each voxel. 3D pixelated detectors coupled with multichannel readout electronics are the most advanced type of CZT devices offering many options in signal processing and enhancing detector performance. One recent innovation proposed for pixelated detectors is to use the induced (transient) signals from neighboring pixels to achieve high sub-pixel position resolution while keeping large pixel sizes. The main hurdle in achieving this goal is the relatively low signal induced on the neighboring pixels because of the electrostatic shielding effect caused by the collecting pixel. In addition, to achieve high position sensitivity one should rely on time-correlated transient signals, which means that digitized output signals must be used. We present the results of our studies to measure the amplitude of the pixel signals so that these can be used to measure positions of the interaction points. This is done with the processing of digitized correlated time signals measured from several adjacent pixels taking into account rise-time and charge-sharing effects. In these measurements we used a focused pulsed laser to generate a 10-micron beam at one milliwatt (650-nm wavelength) over the detector surface while the collecting pixel was moved in cardinal directions. The results include measurements that present the benefits of combining conventional pixel geometry with digital pulse processing for the best approach in achieving sub-pixel position resolution with the pixel dimensions of approximately 2 mm. We also present the sub-pixel resolution measurements at comparable energies from various gamma emitting isotopes.

Comparison of high resolution x-ray detectors with conventional FPDs using experimental MTFs and apodized aperture pixel design for reduced aliasing

NASA Astrophysics Data System (ADS)

Shankar, A.; Russ, M.; Vijayan, S.; Bednarek, D. R.; Rudin, S.

2017-03-01

Apodized Aperture Pixel (AAP) design, proposed by Ismailova et.al, is an alternative to the conventional pixel design. The advantages of AAP processing with a sinc filter in comparison with using other filters include non-degradation of MTF values and elimination of signal and noise aliasing, resulting in an increased performance at higher frequencies, approaching the Nyquist frequency. If high resolution small field-of-view (FOV) detectors with small pixels used during critical stages of Endovascular Image Guided Interventions (EIGIs) could also be extended to cover a full field-of-view typical of flat panel detectors (FPDs) and made to have larger effective pixels, then methods must be used to preserve the MTF over the frequency range up to the Nyquist frequency of the FPD while minimizing aliasing. In this work, we convolve the experimentally measured MTFs of an Microangiographic Fluoroscope (MAF) detector, (the MAF-CCD with 35μm pixels) and a High Resolution Fluoroscope (HRF) detector (HRF-CMOS50 with 49.5μm pixels) with the AAP filter and show the superiority of the results compared to MTFs resulting from moving average pixel binning and to the MTF of a standard FPD. The effect of using AAP is also shown in the spatial domain, when used to image an infinitely small point object. For detectors in neurovascular interventions, where high resolution is the priority during critical parts of the intervention, but full FOV with larger pixels are needed during less critical parts, AAP design provides an alternative to simple pixel binning while effectively eliminating signal and noise aliasing yet allowing the small FOV high resolution imaging to be maintained during critical parts of the EIGI.

A multiplexed TOF and DOI capable PET detector using a binary position sensitive network.

PubMed

Bieniosek, M F; Cates, J W; Levin, C S

2016-11-07

Time of flight (TOF) and depth of interaction (DOI) capabilities can significantly enhance the quality and uniformity of positron emission tomography (PET) images. Many proposed TOF/DOI PET detectors require complex readout systems using additional photosensors, active cooling, or waveform sampling. This work describes a high performance, low complexity, room temperature TOF/DOI PET module. The module uses multiplexed timing channels to significantly reduce the electronic readout complexity of the PET detector while maintaining excellent timing, energy, and position resolution. DOI was determined using a two layer light sharing scintillation crystal array with a novel binary position sensitive network. A 20 mm effective thickness LYSO crystal array with four 3 mm  ×  3 mm silicon photomultipliers (SiPM) read out by a single timing channel, one energy channel and two position channels achieved a full width half maximum (FWHM) coincidence time resolution of 180  ±  2 ps with 10 mm of DOI resolution and 11% energy resolution. With sixteen 3 mm  ×  3 mm SiPMs read out by a single timing channel, one energy channel and four position channels a coincidence time resolution 204  ±  1 ps was achieved with 10 mm of DOI resolution and 15% energy resolution. The methods presented here could significantly simplify the construction of high performance TOF/DOI PET detectors.

Sci-Sat AM(1): Imaging-08: Small animal APD PET detector with submillimetric resolution for molecular imaging.

PubMed

Bérard, P; Bergeron, M; Pepin, C M; Cadorette, J; Tétrault, M-A; Viscogliosi, N; Fontaine, R; Dautet, H; Davies, M; Lecomte, R

2008-07-01

Visualization and quantification of biological processes in mice, the preferred animal model in most preclinical studies, require the best possible spatial resolution in positron emission tomography (PET). A new 64-channel avalanche photodiode (APD) detector module was developed to achieve submillimeter spatial resolution for this purpose. The module consists of dual 4 × 8 APD arrays mounted in a custom ceramic holder. Individual APD pixels having an active area of 1.1 × 1.1 mm2 at a 1.2 mm pitch can be fitted to an 8 × 8 LYSO scintillator block designed to accommodate one-to-one coupling. An analog test board with four 16-channel preamplifier ASICs was designed to be interfaced with the existing LabPET digital processing electronics. At a standard APD operating bias, a mean energy resolution of 27.5 ± 0.6% was typically obtained at 511 keV with a relative standard deviation of 13.8% in signal amplitude for the 64 individual pixels. Crosstalk between pixels was found to be well below the typical lower energy threshold used for PET imaging applications. With two modules in coincidence, a global timing resolution of 5.0 ns FWHM was measured. Finally, an intrinsic spatial resolution of 0.8 mm FWHM was measured by sweeping a 22Na point source between two detector arrays. The proposed detector module demonstrates promising characteristics for dedicated mouse PET imaging at submillimiter resolution. © 2008 American Association of Physicists in Medicine.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carini, Gabriella; Denes, Peter; Gruener, Sol

The Basic Energy Sciences (BES) X-ray and neutron user facilities attract more than 12,000 researchers each year to perform cutting-edge science at these state-of-the-art sources. While impressive breakthroughs in X-ray and neutron sources give us the powerful illumination needed to peer into the nano- to mesoscale world, a stumbling block continues to be the distinct lag in detector development, which is slowing progress toward data collection and analysis. Urgently needed detector improvements would reveal chemical composition and bonding in 3-D and in real time, allow researchers to watch “movies” of essential life processes as they happen, and make much moremore » efficient use of every X-ray and neutron produced by the source The immense scientific potential that will come from better detectors has triggered worldwide activity in this area. Europe in particular has made impressive strides, outpacing the United States on several fronts. Maintaining a vital U.S. leadership in this key research endeavor will require targeted investments in detector R&D and infrastructure. To clarify the gap between detector development and source advances, and to identify opportunities to maximize the scientific impact of BES user facilities, a workshop on Neutron and X-ray Detectors was held August 1-3, 2012, in Gaithersburg, Maryland. Participants from universities, national laboratories, and commercial organizations from the United States and around the globe participated in plenary sessions, breakout groups, and joint open-discussion summary sessions. Sources have become immensely more powerful and are now brighter (more particles focused onto the sample per second) and more precise (higher spatial, spectral, and temporal resolution). To fully utilize these source advances, detectors must become faster, more efficient, and more discriminating. In supporting the mission of today’s cutting-edge neutron and X-ray sources, the workshop identified six detector research challenges (and two computing hurdles that result from the corresponding increase in data volume) for the detector community to overcome in order to realize the full potential of BES neutron and X-ray facilities. Resolving these detector impediments will improve scientific productivity both by enabling new types of experiments, which will expand the scientific breadth at the X-ray and neutron facilities, and by potentially reducing the beam time required for a given experiment. These research priorities are summarized in the table below. Note that multiple, simultaneous detector improvements are often required to take full advantage of brighter sources. High-efficiency hard X-ray sensors: The fraction of incident particles that are actually detected defines detector efficiency. Silicon, the most common direct-detection X-ray sensor material, is (for typical sensor thicknesses) 100% efficient at 8 keV, 25%efficient at 20 keV, and only 3% efficient at 50 keV. Other materials are needed for hard X-rays. Replacement for 3He for neutron detectors: 3He has long been the neutron detection medium of choice because of its high cross section over a wide neutron energy range for the reaction 3He + n —> 3H + 1H + 0.764 MeV. 3He stockpiles are rapidly dwindling, and what is available can be had only at prohibitively high prices. Doped scintillators hold promise as ways to capture neutrons and convert them into light, although work is needed on brighter, more efficient scintillator solutions. Neutron detectors also require advances in speed and resolution. Fast-framing X-ray detectors: Today’s brighter X-ray sources make time-resolved studies possible. For example, hybrid X-ray pixel detectors, initially developed for particle physics, are becoming fairly mature X-ray detectors, with considerable development in Europe. To truly enable time-resolved studies, higher frame rates and dynamic range are required, and smaller pixel sizes are desirable. High-speed spectroscopic X-ray detectors: Improvements in the readout speed and energy resolution of X-ray detectors are essential to enable chemically sensitive microscopies. Advances would make it possible to take images with simultaneous spatial and chemical information. Very high-energy-resolution X-ray detectors: The energy resolution of semiconductor detectors, while suitable for a wide range of applications, is far less than what can be achieved with X-ray optics. A direct detector that could rival the energy resolution of optics could dramatically improve the efficiency of a multitude of experiments, as experiments are often repeated at a number of different energies. Very high-energy-resolution detectors could make these experiments parallel, rather than serial. Low-background, high-spatial-resolution neutron detectors: Low-background detectors would significantly improve experiments that probe excitations (phonons, spin excitations, rotation, and diffusion in polymers and molecular substances, etc.) in condensed matter. Improved spatial resolution would greatly benefit radiography, tomography, phase-contrast imaging, and holography. Improved acquisition and visualization tools: In the past, with the limited variety of slow detectors, it was straightforward to visualize data as it was being acquired (and adjust experimental conditions accordingly) to create a compact data set that the user could easily transport. As detector complexity and data rates explode, this becomes much more challenging. Three goals were identified as important for coping with the growing data volume from high-speed detectors: Facilitate better algorithm development. In particular, algorithms that can minimize the quantity of data stored. Improve community-driven mechanisms to reduce data protocols and enhance quantitative, interactive visualization tools. Develop and distribute community-developed, detector-specific simulation tools. Aim for parallelization to take advantage of high-performance analysis platforms. Improved analysis work flows: Standardize the format of metadata that accompanies detector data and describes the experimental setup and conditions. Develop a standardized user interface and software framework for analysis and data management. The diversity of detector improvements required is necessarily as broad as the range of scientific experimentation at BES facilities. This workshop identified a variety of avenues by which detector R&D can enable enhanced science at BES facilities. The Research Directions listed above will be addressed by focused R&D and detector engineering, both of which require specialized infrastructure and skills. While U.S. leadership in neutron and X-ray detectors lags behind other countries in several areas, significant talent exists across the complex. A forum of technical experts, facilities management, and BES could be a venue to provide further definition.« less

Instrumentation effects on U and Pu CBNM standards spectra quality measured on a 500 mm3 CdZnTe and a 2×2 inch LaBr3 detectors

NASA Astrophysics Data System (ADS)

Meleshenkovskii, I.; Borella, A.; Van der Meer, K.; Bruggeman, M.; Pauly, N.; Labeau, P. E.; Schillebeeckx, P.

2018-01-01

Nowadays, there is interest in developing gamma-ray measuring devices based on the room temperature operated medium resolution detectors such as semiconductor detectors of the CdZnTe type and scintillators of the LaBr3 type. This is true also for safeguards applications and the International Atomic Energy Agency (IAEA) has launched a project devoted to the assessment of medium resolution gamma-ray spectroscopy for the verification of the isotopic composition of U and Pu bearing samples. This project is carried out within the Non-Destructive Assay Working Group of the European Safeguards Research and Development Association (ESARDA). In this study we analyze medium resolution spectra of U and Pu standards with the aim to develop an isotopic composition determination algorithm, particularly suited for these types of detectors. We show how the peak shape of a CdZnTe detector is influenced by the instrumentation parameters. The experimental setup consisted of a 500 mm3 CdZnTe detector, a 2×2 inch LaBr3 detector, two types of measurement instrumentation - an analogue one and a digital one, and a set of certified samples - a 207Bi point source and U and Pu CBNM standards. The results of our measurements indicate that the lowest contribution to the peak asymmetry and thus the smallest impact on the resolution of the 500 mm3 CdZnTe detector was achieved with the digital MCA. Analysis of acquired spectra allowed to reject poor quality measurement runs and produce summed spectra files with the least impact of instrumentation instabilities. This work is preliminary to further studies concerning the development of an isotopic composition determination algorithm particularly suited for CZT and LaBr3 detectors for safeguards applications.

Application of GEM-based detectors in full-field XRF imaging

NASA Astrophysics Data System (ADS)

Dąbrowski, W.; Fiutowski, T.; Frączek, P.; Koperny, S.; Lankosz, M.; Mendys, A.; Mindur, B.; Świentek, K.; Wiącek, P.; Wróbel, P. M.

2016-12-01

X-ray fluorescence spectroscopy (XRF) is a commonly used technique for non-destructive elemental analysis of cultural heritage objects. It can be applied to investigations of provenance of historical objects as well as to studies of art techniques. While the XRF analysis can be easily performed locally using standard available equipment there is a growing interest in imaging of spatial distribution of specific elements. Spatial imaging of elemental distrbutions is usually realised by scanning an object with a narrow focused X-ray excitation beam and measuring characteristic fluorescence radiation using a high energy resolution detector, usually a silicon drift detector. Such a technique, called macro-XRF imaging, is suitable for investigation of flat surfaces but it is time consuming because the spatial resolution is basically determined by the spot size of the beam. Another approach is the full-field XRF, which is based on simultaneous irradiation and imaging of large area of an object. The image of the investigated area is projected by a pinhole camera on a position-sensitive and energy dispersive detector. The infinite depth of field of the pinhole camera allows one, in principle, investigation of non-flat surfaces. One of possible detectors to be employed in full-field XRF imaging is a GEM based detector with 2-dimensional readout. In the paper we report on development of an imaging system equipped with a standard 3-stage GEM detector of 10 × 10 cm2 equipped with readout electronics based on dedicated full-custom ASICs and DAQ system. With a demonstrator system we have obtained 2-D spatial resolution of the order of 100 μm and energy resolution at a level of 20% FWHM for 5.9 keV . Limitations of such a detector due to copper fluorescence radiation excited in the copper-clad drift electrode and GEM foils is discussed and performance of the detector using chromium-clad electrodes is reported.

Calibration of large area Micromegas detectors using cosmic rays

NASA Astrophysics Data System (ADS)

Biebel, O.; Flierl, B.; Herrmann, M.; Hertenberger, R.; Klitzner, F.; Lösel, P.; Müller, R.; Valderanis, C.; Zibell, A.

2017-06-01

Currently m2-sized micropattern detectors with spatial resolution better than 100 μm and online trigger capability are of big interest for many experiments. Large size in combination with superb spatial resolution and trigger capability implicates that the construction of these detectors is highly sophisticated and imposes strict mechanical tolerances. We developed a method to survey assembled and working detectors on potential deviations of the micro pattern readout structures from design value as well as deformations of the whole detector, using cosmic muons in a tracking facility. The LMU Cosmic Ray Facility consists of two 8 m2 ATLAS Monitored Drift Tube chambers (MDT) for precision muon reference tracking and two segmented trigger hodoscopes with sub-ns time-resolution and additional 10 cm position information along the wires of the MDTs. It provides information on homogeneity in efficiency and pulse height of one or several micropattern detectors installed in between the MDTs. With an angular acceptance of -30° to +30° the comparison of the reference muon tracking with centroidal position determination or time projection chamber like track reconstruction in the micropattern detector allows for calibration in three dimensions. We present results of a m2-sized one-dimensional resistive strip Micromegas detector consisting of two readout boards with in total 2048 strips, read out by 16 APV25 front-end boards. This 16-fold segmentation along the precision direction in combination with a 10-fold segmentation in orthogonal direction by the resolution of the trigger hodoscope, allows for very detailed analysis of the 1 m2 detector under study by subdivision into 160 partitions, each being analyzed separately. We are able to disentangle deviations from the readout strip straightness and global deformation due to the small overpressure caused by the Ar:CO2 (93:7) gas mixture flux. We introduce the alignment and calibration procedure, report on homogeneity in efficiency and pulse height and present results on deformation and performance of the m2-sized Micromegas.

GATE simulation of a new design of pinhole SPECT system for small animal brain imaging

NASA Astrophysics Data System (ADS)

Uzun Ozsahin, D.; Bläckberg, L.; El Fakhri, G.; Sabet, H.

2017-01-01

Small animal SPECT imaging has gained an increased interest over the past decade since it is an excellent tool for developing new drugs and tracers. Therefore, there is a huge effort on the development of cost-effective SPECT detectors with high capabilities. The aim of this study is to simulate the performance characteristics of new designs for a cost effective, stationary SPECT system dedicated to small animal imaging with a focus on mice brain. The conceptual design of this SPECT system platform, Stationary Small Animal SSA-SPECT, is to use many pixelated CsI:TI detector modules with 0.4 mm × 0.4 mm pixels in order to achieve excellent intrinsic detector resolution where each module is backed by a single pinhole collimator with 0.3 mm hole diameter. In this work, we present the simulation results of four variations of the SSA-SPECT platform where the number of detector modules and FOV size is varied while keeping the detector size and collimator hole size constant. Using the NEMA NU-4 protocol, we performed spatial resolution, sensitivity, image quality simulations followed by a Derenzo-like phantom evaluation. The results suggest that all four SSA-SPECT systems can provide better than 0.063% system sensitivity and < 1.5 mm FWHM spatial resolution without resolution recovery or other correction techniques. Specifically, SSA-SPECT-1 showed a system sensitivity of 0.09% in combination with 1.1 mm FWHM spatial resolution.

TU-H-CAMPUS-TeP2-03: High Sensitivity and High Resolution Fiber Based Micro-Detector for Sub-Millimeter Preclinical Dosimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Izaguirre, E; Pokhrel, S; Knewtson, T

2016-06-15

Purpose: Current precision of small animal and cell micro-irradiators has continuously increased during the past years. Currently, preclinical irradiators can deliver sub-millimeter fields with micrometric precision but there are no water equivalent dosimeters to determine small field profiles and dose in the orthovoltage range of energies with micrometric resolution and precision. We have developed a fiber based micro-dosimeter with the resolution and dosimetric accuracy required for radiobiological research. Methods: We constructed two prototypes of micro-dosimeters based on different compositions of fiber scintillators to study the spatial resolution and dosimetric precision of small animal and cell micro-irradiators. The first has greenmore » output and the second has blue output. The blue output dosimeter has the highest sensitivity because it matches the spectral sensitivity of silicon photomultipliers. A blue detector with 500um cross section was built and tested respect to a CC01 ion chamber, film, and the 1500um green output detector. Orthovoltage fields from 1×1mm2 to 5×5mm2 were used for detector characteristics comparison. Results: The blue fiber dosimeter shows great agreement with films and matches dose measurements with the gold-standard ion chamber for 5×5mm2 fields. The detector has the appropriate sensitivity to measure fields from 1×1mm2 to larger sizes with a 1% dosimetric accuracy. The spatial resolution is in the sub-millimeter range and the spectral matching with the photomultiplier allows reducing the sensor cross section even further than the presented prototype. These results suggest that scintillating fibers combined with silicon photomultipliers is the appropriate technology to pursue micro-dosimetry for small animals and disperse cell samples. Conclusion: The constructed detectors establish a new landmark for the resolution and sensitivity of fiber based microdetectors. The validation of the detector in our small animal and cell irradiator shows that they are appropriate for preclinical and micro single cell irradiation quality assurance and dosimetry.« less

High density processing electronics for superconducting tunnel junction x-ray detector arrays

NASA Astrophysics Data System (ADS)

Warburton, W. K.; Harris, J. T.; Friedrich, S.

2015-06-01

Superconducting tunnel junctions (STJs) are excellent soft x-ray (100-2000 eV) detectors, particularly for synchrotron applications, because of their ability to obtain energy resolutions below 10 eV at count rates approaching 10 kcps. In order to achieve useful solid detection angles with these very small detectors, they are typically deployed in large arrays - currently with 100+ elements, but with 1000 elements being contemplated. In this paper we review a 5-year effort to develop compact, computer controlled low-noise processing electronics for STJ detector arrays, focusing on the major issues encountered and our solutions to them. Of particular interest are our preamplifier design, which can set the STJ operating points under computer control and achieve 2.7 eV energy resolution; our low noise power supply, which produces only 2 nV/√Hz noise at the preamplifier's critical cascode node; our digital processing card that digitizes and digitally processes 32 channels; and an STJ I-V curve scanning algorithm that computes noise as a function of offset voltage, allowing an optimum operating point to be easily selected. With 32 preamplifiers laid out on a custom 3U EuroCard, and the 32 channel digital card in a 3U PXI card format, electronics for a 128 channel array occupy only two small chassis, each the size of a National Instruments 5-slot PXI crate, and allow full array control with simple extensions of existing beam line data collection packages.

Relevancies of multiple-interaction events and signal-to-noise ratio for Anger-logic based PET detector designs

NASA Astrophysics Data System (ADS)

Peng, Hao

2015-10-01

A fundamental challenge for PET block detector designs is to deploy finer crystal elements while limiting the number of readout channels. The standard Anger-logic scheme including light sharing (an 8 by 8 crystal array coupled to a 2×2 photodetector array with an optical diffuser, multiplexing ratio: 16:1) has been widely used to address such a challenge. Our work proposes a generalized model to study the impacts of two critical parameters on spatial resolution performance of a PET block detector: multiple interaction events and signal-to-noise ratio (SNR). The study consists of the following three parts: (1) studying light output profile and multiple interactions of 511 keV photons within crystal arrays of different crystal widths (from 4 mm down to 1 mm, constant height: 20 mm); (2) applying the Anger-logic positioning algorithm to investigate positioning/decoding uncertainties (i.e., "block effect") in terms of peak-to-valley ratio (PVR), with light sharing, multiple interactions and photodetector SNR taken into account; and (3) studying the dependency of spatial resolution on SNR in the context of modulation transfer function (MTF). The proposed model can be used to guide the development and evaluation of a standard Anger-logic based PET block detector including: (1) selecting/optimizing the configuration of crystal elements for a given photodetector SNR; and (2) predicting to what extent additional electronic multiplexing may be implemented to further reduce the number of readout channels.

Development of a novel depth of interaction PET detector using highly multiplexed G-APD cross-strip encoding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kolb, A., E-mail: armin.kolb@med.uni-tuebingen.de; Parl, C.; Liu, C. C.

Purpose: The aim of this study was to develop a prototype PET detector module for a combined small animal positron emission tomography and magnetic resonance imaging (PET/MRI) system. The most important factor for small animal imaging applications is the detection sensitivity of the PET camera, which can be optimized by utilizing longer scintillation crystals. At the same time, small animal PET systems must yield a high spatial resolution. The measured object is very close to the PET detector because the bore diameter of a high field animal MR scanner is limited. When used in combination with long scintillation crystals, thesemore » small-bore PET systems generate parallax errors that ultimately lead to a decreased spatial resolution. Thus, we developed a depth of interaction (DoI) encoding PET detector module that has a uniform spatial resolution across the whole field of view (FOV), high detection sensitivity, compactness, and insensitivity to magnetic fields. Methods: The approach was based on Geiger mode avalanche photodiode (G-APD) detectors with cross-strip encoding. The number of readout channels was reduced by a factor of 36 for the chosen block elements. Two 12 × 2 G-APD strip arrays (25μm cells) were placed perpendicular on each face of a 12 × 12 lutetium oxyorthosilicate crystal block with a crystal size of 1.55 × 1.55 × 20 mm. The strip arrays were multiplexed into two channels and used to calculate the x, y coordinates for each array and the deposited energy. The DoI was measured in step sizes of 1.8 mm by a collimated {sup 18}F source. The coincident resolved time (CRT) was analyzed at all DoI positions by acquiring the waveform for each event and applying a digital leading edge discriminator. Results: All 144 crystals were well resolved in the crystal flood map. The average full width half maximum (FWHM) energy resolution of the detector was 12.8% ± 1.5% with a FWHM CRT of 1.14 ± 0.02 ns. The average FWHM DoI resolution over 12 crystals was 2.90 ± 0.15 mm. Conclusions: The novel DoI PET detector, which is based on strip G-APD arrays, yielded a DoI resolution of 2.9 mm and excellent timing and energy resolution. Its high multiplexing factor reduces the number of electronic channels. Thus, this cross-strip approach enables low-cost, high-performance PET detectors for dedicated small animal PET and PET/MRI and potentially clinical PET/MRI systems.« less

A novel TOF-PET MRI detector for diagnosis and follow up of the prostate cancer

NASA Astrophysics Data System (ADS)

Garibaldi, F.; Beging, S.; Canese, R.; Carpinelli, G.; Clinthorne, N.; Colilli, S.; Cosentino, L.; Finocchiaro, P.; Giuliani, F.; Gricia, M.; Lucentini, M.; Majewski, S.; Monno, E.; Musico, P.; Santavenere, F.; Tödter, J.; Wegener, H.; Ziemons, K.

2017-09-01

Prostate cancer is the most common disease in men and the second leading cause of death from cancer. Generic large imaging instruments used in cancer diagnosis have sensitivity, spatial resolution, and contrast which are inadequate for the task of imaging details of a small organ such as the prostate. In addition, multimodality imaging can play a significant role in merging anatomical and functional details coming from simultaneous PET and MRI. Indeed, multiparametric PET/MRI was demonstrated to improve diagnosis, but it suffers from too many false positives. In order to address the above limits of the current techniques, we have proposed, built and tested, thanks to the TOPEM project funded by Italian National Institute of Nuclear Phisics, a prototype of an endorectal PET-TOF/MRI probe. In the applied magnification PET geometry, performance is dominated by a high-resolution detector placed closer to the source. The expected spatial resolution in the selected geometry is about 1.5mm FWHM and efficiency of a factor 2 with respect to what was obtained with the conventional PET scanner. In our experimental studies, we have obtained a timing resolution of ˜ 320 ps FWHM and at the same time a Depth of Interaction (DOI) resolution of under 1mm. Tests also showed that mutual adverse PET-MR effects are minimal. In addition, the matching endorectal RF coil was designed, built and tested. In the next planned studies, we expect that benefiting from the further progress in scintillator crystal surface treatment, in SiPM technology and associated electronics would allow us to significantly improve TOF resolution.

A combined time-of-flight and depth-of-interaction detector for total-body positron emission tomography

PubMed Central

Berg, Eric; Roncali, Emilie; Kapusta, Maciej; Du, Junwei; Cherry, Simon R.

2016-01-01

Purpose: In support of a project to build a total-body PET scanner with an axial field-of-view of 2 m, the authors are developing simple, cost-effective block detectors with combined time-of-flight (TOF) and depth-of-interaction (DOI) capabilities. Methods: This work focuses on investigating the potential of phosphor-coated crystals with conventional PMT-based block detector readout to provide DOI information while preserving timing resolution. The authors explored a variety of phosphor-coating configurations with single crystals and crystal arrays. Several pulse shape discrimination techniques were investigated, including decay time, delayed charge integration (DCI), and average signal shapes. Results: Pulse shape discrimination based on DCI provided the lowest DOI positioning error: 2 mm DOI positioning error was obtained with single phosphor-coated crystals while 3–3.5 mm DOI error was measured with the block detector module. Minimal timing resolution degradation was observed with single phosphor-coated crystals compared to uncoated crystals, and a timing resolution of 442 ps was obtained with phosphor-coated crystals in the block detector compared to 404 ps without phosphor coating. Flood maps showed a slight degradation in crystal resolvability with phosphor-coated crystals; however, all crystals could be resolved. Energy resolution was degraded by 3%–7% with phosphor-coated crystals compared to uncoated crystals. Conclusions: These results demonstrate the feasibility of obtaining TOF–DOI capabilities with simple block detector readout using phosphor-coated crystals. PMID:26843254

A combined time-of-flight and depth-of-interaction detector for total-body positron emission tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berg, Eric, E-mail: eberg@ucdavis.edu; Roncali, Emilie; Du, Junwei

Purpose: In support of a project to build a total-body PET scanner with an axial field-of-view of 2 m, the authors are developing simple, cost-effective block detectors with combined time-of-flight (TOF) and depth-of-interaction (DOI) capabilities. Methods: This work focuses on investigating the potential of phosphor-coated crystals with conventional PMT-based block detector readout to provide DOI information while preserving timing resolution. The authors explored a variety of phosphor-coating configurations with single crystals and crystal arrays. Several pulse shape discrimination techniques were investigated, including decay time, delayed charge integration (DCI), and average signal shapes. Results: Pulse shape discrimination based on DCI providedmore » the lowest DOI positioning error: 2 mm DOI positioning error was obtained with single phosphor-coated crystals while 3–3.5 mm DOI error was measured with the block detector module. Minimal timing resolution degradation was observed with single phosphor-coated crystals compared to uncoated crystals, and a timing resolution of 442 ps was obtained with phosphor-coated crystals in the block detector compared to 404 ps without phosphor coating. Flood maps showed a slight degradation in crystal resolvability with phosphor-coated crystals; however, all crystals could be resolved. Energy resolution was degraded by 3%–7% with phosphor-coated crystals compared to uncoated crystals. Conclusions: These results demonstrate the feasibility of obtaining TOF–DOI capabilities with simple block detector readout using phosphor-coated crystals.« less

Poster — Thur Eve — 01: The effect of the number of projections on MTF and CNR in Compton scatter tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chighvinadze, T; Pistorius, S; CancerCare Manitoba, Winnipeg, MB

2014-08-15

Purpose: To investigate the dependence of the reconstructed image quality on the number of projections in multi-projection Compton scatter tomography (MPCST). The conventional relationship between the projection number used for reconstruction and reconstructed image quality pertained to CT does not necessarily apply to MPCST, which can produce images from a single projection if the detectors have sufficiently high energy and spatial resolution. Methods: The electron density image was obtained using filtered-backprojection of the scatter signal over circular arcs formed using Compton equation. The behavior of the reconstructed image quality as a function of the projection number was evaluated through analyticalmore » simulations and characterized by CNR and MTF. Results: The increase of the projection number improves the contrast with this dependence being a function of fluence. The number of projections required to approach the asymptotic maximum contrast decreases as the fluence increases. Increasing projection number increases the CNR but not spatial resolution. Conclusions: For MPCST using a 500eV energy resolution and a 2×2mm{sup 2} size detector, an adequate image quality can be obtained with a small number of projections provided the incident fluence is high enough. This is conceptually different from conventional CT where a minimum number of projections is required to obtain an adequate image quality. While increasing projection number, even for the lowest dose value, the CNR increases even though the number of photons per projection decreases. The spatial resolution of the image is improved by increasing the sampling within a projection rather than by increasing the number of projections.« less

Radiation effects on ALICE V0 detector components

NASA Astrophysics Data System (ADS)

Cheynis, B.; Ducroux, L.; Grossiord, J.-Y.; Guichard, A.; Pillot, P.; Rapp, B.; Tieulent, R.; Tromeur, W.; Zoccarato, Y.

2006-12-01

The 60 MeV proton beam delivered by the RADEF facility of the University of Jyväskylä (Finland) was used to measure the radiation effects on the counter components of the V0 detector of ALICE. There are the scintillator BC404, the wavelength shifting fibres BCF9929A and the optical fibres BCF98 from Bicron (Saint-Gobain). The light yield and the time resolution given by a counter of the inner ring of the V0C array, mounted within a dedicated device, were measured as a function of the radiation dose up to about 300 krad. A global light attenuation of the order of 30% can be anticipated during 10 years of ALICE running.

Timing resolution and time walk in SLiK SPAD: measurement and optimization

NASA Astrophysics Data System (ADS)

Fong, Bernicy S.; Davies, Murray; Deschamps, Pierre

2017-08-01

Timing resolution (or timing jitter) and time walk are separate parameters associated with a detector's response time. Studies have been done mostly on the time resolution of various single photon detectors [1]. As the designer and manufacturer of the ultra-low noise (ƙ-factor) silicon avalanche photodiode the SLiK SPAD, which is used in many single photon counting applications, we often get inquiries from customers to better understand how this detector behaves under different operating conditions. Hence, here we will be focusing on the study of these time related parameters specifically for the SLiK SPAD, as a way to provide the most direct information for users of this detector to help with its use more efficiently and effectively. We will be providing the study data on how these parameters can be affected by temperature (both intrinsic to the detector chip and environmental input based on operating conditions), operating voltage, photon wavelength, as well as light spot size. How these parameters can be optimized and the trade-offs from optimization from the desired performance will be presented.

Design, implementation, and performance of the Astro-H SXS calorimeter array and anticoincidence detector

NASA Astrophysics Data System (ADS)

Kilbourne, Caroline A.; Adams, Joseph S.; Brekosky, Regis P.; Chervenak, James A.; Chiao, Meng P.; Eckart, Megan E.; Figueroa-Feliciano, Enectali; Galeazzi, Masimilliano; Grein, Christoph; Jhabvala, Christine A.; Kelly, Daniel; Leutenegger, Maurice A.; McCammon, Dan; Scott Porter, F.; Szymkowiak, Andrew E.; Watanabe, Tomomi; Zhao, Jun

2018-01-01

The calorimeter array of the JAXA Astro-H (renamed Hitomi) soft x-ray spectrometer (SXS) was designed to provide unprecedented spectral resolution of spatially extended cosmic x-ray sources and of all cosmic x-ray sources in the Fe-K band around 6 keV, enabling essential plasma diagnostics. The SXS had a square array of 36 x-ray calorimeters at the focal plane. These calorimeters consisted of ion-implanted silicon thermistors and HgTe thermalizing x-ray absorbers. These devices demonstrated a resolution of better than 4.5 eV at 6 keV when operated at a heat-sink temperature of 50 mK. We will discuss the basic physical parameters of this array, including the array layout, thermal conductance of the link to the heat sink, resistance function, absorber details, and means of attaching the absorber to the thermistor-bearing element. We will also present the thermal characterization of the whole array, including thermal conductance and crosstalk measurements and the results of pulsing the frame temperature via alpha particles, heat pulses, and the environmental background. A silicon ionization detector was located behind the calorimeter array and served to reject events due to cosmic rays. We will briefly describe this anticoincidence detector and its performance.

The Design, Implementation, and Performance of the Astro-H SXS Calorimeter Array and Anti-Coincidence Detector

NASA Technical Reports Server (NTRS)

Kilbourne, Caroline A.; Adams, Joseph S.; Brekosky, Regis P.; Chiao, Meng P.; Chervenak, James A.; Eckart, Megan E.; Figueroa-Feliciano, Enectali; Galeazzi, Masimilliano; Grein, Christoph; Jhabvala, Christine A.;

Evaluation of a ''CMOS'' Imager for Shadow Mask Hard X-ray Telescope

NASA Technical Reports Server (NTRS)

Desai, Upendra D.; Orwig, Larry E.; Oergerle, William R. (Technical Monitor)

2002-01-01

We have developed a hard x-ray coder that provides high angular resolution imaging capability using a coarse position sensitive image plane detector. The coder consists of two Fresnel zone plates. (FZP) Two such 'FZP's generate Moire fringe patterns whose frequency and orientation define the arrival direction of a beam with respect to telescope axis. The image plane detector needs to resolve the Moire fringe pattern. Pixilated detectors can be used as an image plane detector. The recently available 'CMOS' imager could provide a very low power large area image plane detector for hard x-rays. We have looked into a unit made by Rad-Icon Imaging Corp. The Shadow-Box 1024 x-ray camera is a high resolution 1024xl024 pixel detector of 50x50 mm area. It is a very low power, stand alone camera. We present some preliminary results of our investigation of evaluation of such camera.

Experiment definition and integration study for the accommodation of giant, passive detector of Exotic Particles In the Cosmic Rays (EPIC) payload on shuttle/spacelab missions

NASA Technical Reports Server (NTRS)

Price, P. B.

1978-01-01

The feasibility of the design, construction, launch and retrieval of a hinged 15 ft by 110 ft the platform containing an array of interleaved CR-39 and Lexan track-recording detectors to be placed into circular orbit by space shuttle is assessed. The total weight of the detector assembly plus supporting structure and accessories is 32,000 pounds. The modular construction permits as little as one fourth of the payload to be exposed at one time. The CR-39 detector has sensitivity adequate to detect and study cosmic rays ranging from minimum ionizing iron-group nuclei to the heaviest elements. The detectors will survive a one year exposure to trapped protons without losing their high resolution. Advantages include low cost, huge collecting power (approximately 150 sq m) as well as the high resolution previously attainable only with electronic detectors.