Benefits of Position-Sensitive Detectors for Radioactive Source Detection

Abstract

Abstract-There are many systems for counting photons such as gamma-rays emitted from radioactive sources. Many of these systems are also position-sensitive, which means that the system provides directional information about recorded events. This paper investigates whether or not the additional information provided by position-sensitive capability improves the performance of detecting a point-source in background. We analyze the asymptotic performance of the generalized likelihood ratio test (GLRT) and a test based on the maximum-likelihood (ML) estimate of the source intensity for systems with and without position-sensitive capability. When the background intensity is known and detector sensitivity is spatially uniform, we prove that position-sensitive capability increases the area under the receiver operating characteristic curve (AUC). For cases when detector sensitivity is nonuniform or background intensity is unknown, we provide numerical results to illustrate the effect of the parameters on detection performance.

Source Detection Performance Prediction for a CdZnTe Array

“…This is in contrast to previous works that state performance prediction [3], [5], [13] in terms of ROC and the area under the ROC curve (AUC). We choose to fix a false alarm probability and examine how the probability of detection varies as a function of scan time because the probability of detection is arguably more important to the practitioner than the AUC.…”

“…We analyze the performance of the source intensity test (SIT) [13] applied to the gamma-ray source detection problem. The SIT is based on the quasi maximum-likelihood (QML) estimate for the source intensity.…”

“…The source intensity test (SIT) [13] for detecting the presence of a radiation source of unknown intensity is given by (9) where is the QMLE for , which is the first element of , and is a threshold chosen by the user to obtain the desired false alarm rate. The user decides that a source is present, or is true, when the source intensity estimate is greater than the threshold .…”

“…This method is similar to that used in [3], [5], and [13]. We used the following procedure to compute the empirical performance: 1) Repeat times with a source present and times without a source present: a) Draw the number of recorded source counts from a Poisson distribution with mean , where is the true source intensity, is the true sensitivity, and is the mean number of received counts from the source.…”

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

“…We analyzed the asymptotic detection performance of gamma-ray imaging systems in [5], proving that position-sensitivity always improves detection performance when the detector sensitivity is uniform. The formulas for asymptotic detection performance in [5] can give inaccurate results in practical applications where model mismatch exists. Our work extends previous work on asymptotic detection performance of gamma-ray detectors by accounting for model mismatch.…”