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Graphical Markov models determined by acyclic digraphs (ADGs), also called directed acyclic graphs (DAOs), are widely studied in statistics, computer science (as Bayesian networks), operations research (as influence diagrams), and many related fields. Because different ADOs may determine the same Markov equivalence class, it long has been of interest to(More)
Bayesian networks, equivalently graphical Markov models determined by acyclic digraphs or ADGs (also called directed acyclic graphs or dags), have proved to be both effective and efficient for representing complex multivariate dependence structures in terms of local relations. However, model search and selection is potentially complicated by the many-to-one(More)
SimSET (a Simulation System for Emission Tomography) is being modified to more accurately simulate typical PET block detector tomographs. A new detector module that models the detector system as a collection of rectangular boxes is being added to the software. The new model is sufficiently general to allow many more imaginative or speculative detector(More)
By adding a second parameter, Conway and Maxwell created a new distribution for situations where data deviate from the standard Poisson distribution. This new distribution contains a normalization constant expressed as an infinite sum whose summation has no known closed-form expression. Shmueli et al. produced an approximation for this sum but proved only(More)
We consider the problem of a consumer wishing to evaluate bundles of options from a list of N independently selectable binary options. The consumer's goal is to find the t best bundles out of the 2 N possible bundle subsets, when ranked according to supplied utility and cost functions. Although 2 N is very large (e.g., for N = 100, 2 N ≈ 10 30), we show how(More)
We are conducting a two-phase study, which aims to select design parameters of a long-axis positron emission tomography (PET) scanner that are a compromise between detection performance and cost. In this first phase, we examine the effects of axial length, detector thickness and collimator geometry on the noise equivalent count rate per axial length (λNEC)(More)
We present a study that introduces two approaches to implementing block detectors into SimSET and compares their performance. SimSET is a photon tracking simulation package, which currently incorporates only detectors made of a solid annulus of scinitillator material. A pseudo-block approximation has been imposed on the solid annulus of conventional SimSET(More)
OBJECTIVES: We have added a block detector model to the Simulation System for Emission Tomography (SimSET) software version 2.9. METHODS: The new model simulates the detector system as a collection of right rectangular boxes and allows for very flexible positioning of these boxes. This model allows users to simulate typical block-based cylindrical(More)
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