Online program Overview Session: RTSD-02

Abstract

Advanced X-ray imaging is a principal pillar supporting aviation security and provides materially segmented images of bags, luggage, and cargo. The images are processed to provide a high probability of detection for contraband and/or threats, at an acceptably low false alarm rate to allow sufficient throughput. As the list of contraband and threats increases, the challenge to maintain a high detection probability at a low false alarm rate is advancing the state of art in detectors, sources, scanning methods, reconstruction, recognition, and decision, with the goal of clearing items for air transport. Room temperature semiconductor detectors are currently being used in commercially available diffraction scanners. These are based on pixellated Cadmium Zinc Telluride spectroscopic detectors, which are being developed further for better performance and lower cost. Cadmium Telluride and Cadmium Zinc Telluride photon counting detectors are currently being developed for potential use in multi-energy transmission scanners to improve detection and lower false alarms compared to the dual-energy dual-layer scintillator based scanners that are in wide use. Sensor performance requirements and cost constrains for widespread use of room temperature semiconductor detectors in both transmission and diffraction scanners are presented, with a focus on next generation computed tomography methods in multi-modal system of systems approaches to achieve the imaging workflows required for aviation security. Detector array and source geometries to achieve combined transmission and diffraction imaging in the different concepts of operation for the various scanning applications in aviation security are discussed.

Abstract

During nuclear dismantling, remote measurements, as radiation gamma imaging, are particularly advantageous since they reduce the risk for users, providing a visual map of radioactivity even in inaccessible environments. However, 2D gamma imaging does not directly provide the distance between source and detector, neither the 3D localization of the source. The goal of this work is to overcome these limits by developing a new compact and light 3D coded-aperture spectro-imager for applications in nuclear dismantling. This study presents the developments of the prototype, consisting of a coded-aperture gamma spectro-imager and an RGB-D (color and depth) camera, in carrying out 3D gamma imaging in experimental laboratory conditions. The device weight 325 g, with dimensions of 18 × 10 × 2.8 cm, and can distinguish among the most common radionuclides in the nuclear industry with energies ranging from the 59.5 keV gamma ray line of 241Am, up to the 60Co 1332 keV emission. The 3D hotspot localization and reconstruction are achieved with a triangulation from different viewpoints, which is made possible using a SLAM (Simultaneous Localization And Mapping) algorithm. We tested the prototype using point-like radioactive sources both in single and multiple sources configurations. In both cases, using a minimum of three static poses of few minutes’ duration, the sources localizations are correctly achieved with errors in the order of 2 cm for measurements taken at almost one meter. New tests on volumetric and extended sources are currently on-going.

Abstract

Spectral photon counting technology (SPCCT) represents a critical leap for security screening, offering high-resolution imaging and accurate material identification to reduce false alarms and detect threats invisible to legacy systems. SureScan Corporation utilizes SPCCT and dual-energy CT (DECT) in airport explosive detection systems (EDS), focusing R&D on characterizing prototype components like the AMS-OSRAM AS5920M. This state-of-the-art, 4-side buttable system-in-package (BSIP) module features direct-conversion CdZnTe crystals with 341µm x 365µm pixels integrated with ultra-low noise ASICs. Each ASIC supports five configurable energy thresholds and operates with short dead times to sustain high photon flux without significant pile-up. Our performance evaluation includes per-bin count rates, spatial uniformity, and spectral fidelity under various beam conditions, alongside imaging metrics such as modulation transfer function (MTF) and detective quantum efficiency (DQE). Furthermore, we demonstrate the importance of spectrum unfolding to correct non-ideal detector responses. By utilizing energy response function models derived from synchrotron measurements at Brookhaven National Laboratory, we reconstructed true incident energy spectra, significantly improving the accuracy of material identification through proprietary empirical decomposition methodologies.

Abstract

For low-flux radiation imaging applications such as gamma-ray imaging, nuclear medicine, and X-ray diffraction, spectral and spatial resolution are performance drivers.However, detector efficiency is essential as it determines the quantity of information collected. The primary challenge is to achieve high-resolution performance at a reasonable cost. Then, it becomes possible to increase detection volume and the amount of information that the system can gather within a limited time.

Our HiSPECT CZT detector module addresses this challenge through several key principles: the anode is segmented into large pixels, which limits charge sharing, while high spatial resolution is achieved through sub-pixel positioning. The low electronics density reduces cost, power dissipation, and improves yield. Additionally, the absence of cathode readout simplifies integration, while the depth of interaction is retrieved through multiple anode readouts.

In this work, we present how modules are combined to build larger systems, detailing the readout electronics and showcasing various imaging application cases, including coded aperture, collimator, positron, and Compton imaging modes.

Abstract

Radioactive source activity quantification is critical in many applications.  A limiting factor in estimating activity is often knowledge of the source distribution within a medium since the position of the activity can greatly impact the observed counts at the detector.  Algorithms have been developed to use a Compton and coded aperture gamma-ray imaging detector to image the source distribution within the volume of interest using a set of stationary measurements or a free-moving measurement with a simultaneously localization and mapping (SLAM) system.  The iterative 3D volumetric imaging algorithm will be described.  The imaged source distribution can then be used to improve activity quantification over a uniform source assumption.  This is demonstrated with measurements of various geometries.