Physics-Based, Bayesian Sequential Detection Method and System for Radioactive Contraband

摘要

A distributed sequential method and system for detecting and identifying radioactive contraband from highly uncertain (noisy) low-count, radionuclide measurements, i.e. an event mode sequence (EMS), using a statistical approach based on Bayesian inference and physics-model-based signal processing based on the representation of a radionuclide as a monoenergetic decomposition of monoenergetic sources. For a given photon event of the EMS, the appropriate monoenergy processing channel is determined using a confidence interval condition-based discriminator for the energy amplitude and interarrival time. If accepted the parameter values of the photon event are used to update the parameter values using an LKF for the energy amplitude and a bootstrap PF for the interarrival times. These parameter estimates are then used to update a measured probability density function estimate for a target radionuclide. A a sequential likelihood ratio test, which is based in part on a previous sequential likelihood ratio for a previous photon event, the updated measured PDF estimates, and the an a-priori PDF estimates based on expected amplitude level and interarrival time values of the target radionuclide, is then used to determine one of two threshold conditions signifying that the EMS is either identified as the target radionuclide or as not the target radionuclide, and if not, then repeating the process with for the next sequential photon event of the EMS until one of the two threshold conditions is satisfied.