3-D position sensitive CdZnTe gamma-ray spectrometers

He, Zhong; Li, W.; Knoll, G.F.; Wehe, D.K.; Berry, J.E.; Stahle, C. M.

doi:10.1016/s0168-9002(98)00950-4

Cited by 231 publications

(114 citation statements)

References 6 publications

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“…The quasi maximum likelihood (QML) estimate of the parameter vector is given by (3) assuming a solution exists and is unique. The subscript is included to emphasize that the estimate is a function of a list of event attributes acquired during a scan of duration .…”

Section: Estimator Definitionmentioning

confidence: 99%

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Asymptotic Source Detection Performance of Gamma-Ray Imaging Systems Under Model Mismatch

Lingenfelter

Fessler

Scott

et al. 2011

IEEE Trans. Signal Process.

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Abstract-Likelihood-based test statistics for the task of detecting a radioactive source in background using a gamma-ray imaging system often have intractable distributions. This complicates the tasks of predicting detection performance and setting thresholds that ensure desired false-alarm rates. Asymptotic distributions of test statistics can aid in predicting performance and in setting detection thresholds. However, in applications with complex sensors, like gamma-ray imaging, often only approximate statistical models for the measurements are available. Standard asymptotic approximations can yield inaccurate performance predictions when based on misspecified models. This paper considers asymptotic properties of detection tests based on maximum likelihood (ML) estimates under model mismatch, i.e., when the statistical model used for detection differs from the true distribution. We provide general expressions for the asymptotic distribution of likelihood-based test statistics when the number of measurements is Poisson, and expressions specific to gamma-ray source detection that one can evaluate using a modest amount of data from a real system or Monte Carlo simulation. Considering a simulated Compton imaging system, we show that the proposed expressions yield more accurate detection performance predictions than previous expressions that ignore model mismatch. These expressions require less data and computation than conventional empirical methods.

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Section: Estimator Definitionmentioning

confidence: 99%

“…By the definition in (3), assuming that the log-likelihood is differentiable and the maximizer is in the interior of the parameter space, the QMLE satisfies…”

Section: Properties Of the Qmlementioning

confidence: 99%

Asymptotic Source Detection Performance of Gamma-Ray Imaging Systems Under Model Mismatch

Lingenfelter

Fessler

Scott

et al. 2011

IEEE Trans. Signal Process.

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“…The interaction depth provide a correction for the electron path length and the trapping which are important for thick detectors (∼ 1 cm). He et al have performed extensive studies on this possibility [38], [39]. The fist 3-D position-sensitive semiconductor detector with CdZnTe yielded an energy resolution of 10 keV at 662 keV and a depth resolution of 0.5 mm.…”

Section: -D Position Sensitive Semiconductor Detectormentioning

confidence: 99%

Recent progress in CdTe and CdZnTe detectors

Takahashi

Watanabe

2001

IEEE Trans. Nucl. Sci.

528

275

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Cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) have been regarded as promising semiconductor materials for hard X-ray and γ-ray detection. The high atomic number of the materials (Z Cd =48, Z T e =52) gives a high quantum efficiency in comparison with Si. The large band-gap energy (Eg ∼ 1.5 eV) allows us to operate the detector at room temperature. However, a considerable amount of charge loss in these detectors produces a reduced energy resolution. This problem arises due to the low mobility and short lifetime of holes. Recently, significant improvements have been achieved to improve the spectral properties based on the advances in the production of crystals and in the design of electrodes. In this overview talk, we summarize (1) advantages and disadvantages of CdTe and CdZnTe semiconductor detectors and (2) technique for improving energy resolution and photopeak efficiencies. Applications of these imaging detectors in future hard X-ray and gamma-ray astronomy missions are briefly discussed.

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“…For example, when there is no source present, the true source intensity is zero, but model mismatch may cause the source intensity estimate to converge to some nonzero value. To precisely define the value to which the parameter estimates converge, we first define the expected log-likelihood by (7) where the expectation is with respect to the true distribution and is the set of all lists of recorded attributes. This definition uses the expected value of the log-likelihood because it is the likelihood function one would obtain with an infinitely large number of observations, and thus it defines the asymptotic behavior of the estimates.…”

Section: B Detection Methodsmentioning

confidence: 99%

“…For example, Doppler broadening ( [6], p. 311) is not simulated in [5]. Room-temperature pixellated semiconductor detectors, including the detectors used in this work [7], have an area near the anode where interacting photons are not detected. To simplify computation, the model used in this work, based on [1], does not account for this non-ideal detector behavior.…”

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confidence: 99%

Source Detection Performance Prediction for a CdZnTe Array

Lingenfelter

Fessler

Scott

et al. 2013

IEEE Trans. Nucl. Sci.

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Abstract-The complex system response of 3D position-sensitive gamma-ray detectors complicates modeling the recorded measurements and makes exact expressions for detection performance intractable. This makes source detection performance difficult and expensive to compute. Asymptotic analysis has the potential to simplify detection performance prediction with complex systems and has previously been applied to detection performance prediction with simulated gamma-ray detectors. In this work, we use asymptotic performance prediction methods to predict points on the receiver operating characteristic (ROC) curve for the illustrative task of detecting a 137 Cs source in background with an 18-detector CdZnTe array. We assume that the source position, source energy, background spectrum, and background spatial distribution are known. Although these assumptions are not always valid in practice, the efficiency of the prediction method makes it attractive for detection system design problems. Our results show that the asymptotic performance prediction method accurately predicts the empirically observed performance with real data recorded with a real system. Our results also characterize the performance of the detector array for the task of source detection. The accuracy and computational efficiency of the asymptotic detection performance prediction method make it a viable alternative to empirical performance evaluation.

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3-D position sensitive CdZnTe gamma-ray spectrometers

Cited by 231 publications

References 6 publications

Asymptotic Source Detection Performance of Gamma-Ray Imaging Systems Under Model Mismatch

Asymptotic Source Detection Performance of Gamma-Ray Imaging Systems Under Model Mismatch

Recent progress in CdTe and CdZnTe detectors

Source Detection Performance Prediction for a CdZnTe Array

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