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Gamma-ray Imaging

Session chair: Sanada , Yukihisa (Japan Atomic Energy Agency, Sector of Fukushima Research and Development, Fukushima, Japan); He , Zhong (University of Michigan, Nuclear Engineering and Radiological Science, Ann Arbor, USA)
Shortcut: N-03
Date: Tuesday, 19 October, 2021, 9:15 AM - 11:15 AM
Room: NSS - 3
Session type: NSS Session


Click on an contribution to preview the abstract content.

9:15 AM N-03-01

A High-Sensitivity and High-Resolution 4π-View Gamma Imager with Mosaic-Patterned 3D Position-Sensitive Scintillators (#907)

Y. Hu1, 2, Z. Lyu1, 2, P. Fan3, 4, Y. Xia3, 4, S. Wang1, 2, Z. Wu1, 2, Y. Liu1, 2, T. Ma1, 2

1 Tsinghua University, Department of Engineering Physics, Beijing, China
2 Ministry of Education, Key Laboratory of Particle & Radiation Imaging, Beijing, China
3 China Academy of Space Technology, Beijing Institute of Spacecraft Environment Engineering, Beijing, China
4 Beijing Institute of Spacecraft Environment Engineering, Science and Technology on Reliability and Environmental Engineering Laboratory, Beijing, China


Industrial gamma cameras are widely used in nuclear power plant monitoring, nuclear emergency response and homeland security applications. Existing mechanically collimated gamma cameras (such as coded-aperture gamma imagers) have reduced sensitivity and limited FOV (typically < 40 deg). State-of-art Compton cameras can have a full 4π-view FOV; however, they are only effective in a limited gamma energy range (typically >250 keV).

This study aims to build a gamma camera with high sensitivity, high resolution, and a 4π-view FOV. We present a collimator-less gamma imager design based on a 3D position-sensitive, mosaic-patterned scintillator block. Since the gamma events distribution in the scintillator block is sensitive to incoming gamma-ray's direction, it is possible to perform high-sensitivity, 4π-FOV gamma imaging thanks to the collimator-less design. Meanwhile, the specifically mosaic-pattern block design enables high-resolution gamma imaging.

We have fabricated a mosaic-patterned scintillator block with 128 spatially separated GAGG(Ce) scintillators. A series of imaging experiments with 99mTc source show that the developed gamma imager could achieve a positioning accuracy of less than 1° for a single point source and clearly resolve two-point sources with 10° separation. The imager is able to clearly resolve 2×6 99mTc point sources with 20° separation. Imaging tests with higher-energy sources, such as 137Cs is under way. Further work is in progress to integrate two compact gamma imager prototypes.


This research was supported by the National Natural Science Foundation of China (No. 81727807), National Key Research and Development (R&D) Plan of China (Grant ID. 2019YFF0302503), and Tsinghua University Initiative Scientific Research Program (No. 20197010010).

Keywords: gamma imager, 4π-view FOV, 3D position-sensitive scintillator, mosaic pattern
9:30 AM N-03-02

Single Detector 3D Source Imaging Using a Kullback-Leibler Divergence Based Prior (#1200)

J. Lee1, 2, R. J. Cooper2, T. H. Y. Joshi2, K. Vetter1, 2

1 University of California, Berkeley, Nuclear Engineering, Berkeley, California, United States of America
2 Lawrence Berkeley National Laboratory, Applied Nuclear Physics, Berkeley, California, United States of America


Recent advances in computer vision combined with the radiation detection technology have enabled the possibility of using a single detector on free-moving platforms for localization and mapping of radiological sources in 3-D. The reconstruction of 3-D source activity maps from a time-series of count data can be performed with the well-known Maximum Likelihood Expectation Maximization (ML-EM) algorithm; however, due to the limited number of measurements available and the vastness of the 3-D imaging space, the reconstruction problem is highly underdetermined and ill-posed, and thus, the ML-EM algorithm often leads to spurious images with severe overfitting. 

In this work, to overcome the limitations of the ML-EM algorithm, we propose the use of Bayesian Maximum a Posteriori Expectation Maximization (MAP-EM), with Kullback-Leibler (KL) divergence as a prior. Specifically, KL divergences are evaluated between the measured count distribution and the forward projection from each voxel and used to penalize those voxels that are unlikely to have contributed to the observed count distribution. To benchmark the proposed algorithm, a free-moving measurement scenario was simulated with a single detector, and both the ML-EM and the proposed algorithm were used to reconstruct the source distribution. The reconstruction results show that the proposed algorithm significantly outperforms the ML-EM algorithm, effectively addressing the overfitting issue.


This material is based upon work supported by Defense Threat Reduction Agency under DTRA 13081-31571.

Keywords: Radiation imaging, image reconstruction, radiation source search, Maximum a Posteriori (MAP).
9:45 AM N-03-03

Multi-system Scene Data Fusion --Collaborative 3DGamma-ray Mapping with sUAS Swarms (#1250)

D. Hellfeld1, N. Abgrall1, T. H. Y. Joshi1, V. Negut1, R. Pavlovsky1, M. Salathe1, J. R. Vavrek1, B. J. Quiter1

1 Lawrence Berkeley National Laboratory, Nuclear Science Division, Berkeley, California, United States of America


The ability to map gamma-ray source distributions in 3D over large areas and in near real-time has applications in contamination avoidance and remediation, consequence man- agement and geologic survey. The concept of Scene Data Fusion (SDF), developed by Lawrence Berkeley National Laboratory, has been demonstrated to provide this capability in both a detector-agnostic (semiconductor, scintillator, etc.) and platform-agnostic (hand-carried, vehicle, aerial system, etc.) deployment. In order to enhance the mapping efficiency and sensitivity across wide-area environments, we investigate how multiple independent systems can be operated collectively to construct a single actionable contextually-aware 3D gamma-ray map. In this work, we focus on large outdoor environments and investigate the use of a group, or “swarm”, of several small Unmanned Aerial Systems (sUAS) that operate either autonomously or remotely controlled by humans. Here we present a proof-of-principle of multi-system SDF where two independent measurements were combined to localize and quantify a gamma-ray point-source in a single 3D map.


This material is based upon work supported by the Defense Threat Reduction Agency under HDTRA 13081-34686. Distribution A: approved for public release, distribution is unlimited. This support does not constitute an express or implied endorsement on the part of the United States Government.

Keywords: gamma-ray imaging, data fusion, sUAS
10:00 AM N-03-04

3D Compton Imaging of Distributed Sources around the Chernobyl NPP (#1280)

K. Knecht1, D. Gunter4, A. Haefner3, 2, J. Hecla1, D. Hellfeld2, T. Joshi2, R. Pavolvsky2, B. Quiter2, K. Vetter1, 2

1 University of California, Berkeley, Nuclear Engineering, Berkeley, California, United States of America
2 Lawrence Berkeley National Laboratory, Nuclear Science Division, Berkeley, California, United States of America
3 GammaReality Inc., Richmond, California, United States of America
4 Gunter Physics, Lisle, Illinois, United States of America


Portable radiation detection systems can be equipped with contextual sensors to allow free-moving 3D gamma-ray imaging in a method called scene data fusion (SDF). The scene information provided by the contextual sensors can be used to enable 3D imaging and constrain image reconstruction to improve imaging accuracy and computational efficiency. SDF could be a useful tool in many applications, including radiation mapping for accident remediation. To demonstrate this concept, Polaris-LAMP, a commercially available detector that has been integrated with contextual sensors, was operated in and around the Chernobyl Nuclear Power Plant. Compton imaging techniques are applied to the data collected over a series of 20-50 minute dynamic measurements around Pripyat, a nearby town which has been abandoned since the accident. These reconstruction techniques created 3D maps of gamma-ray sources and successfully identified hot spot candidates on key features of the scenes investigated, demonstrating the usefulness of SDF in radiation mapping of unknown distributed source environments. The contextual data captured by Polaris-LAMP also generated interesting visual products of scenes around Pripyat.

AcknowledgmentThis material is based upon work supported by the Department of Energy National Nuclear Security Administration through the Nuclear Science and Security Consortium under Award Number(s) DE-NA0003180. This support does not constitute an expressed or implied endorsement on the part of the United States Government
Keywords: gamma-ray imaging, multi-modality sensing, Compton imaging, scene data fusion, Chernobyl NPP accident
10:15 AM N-03-05

Double-photon simultaneous imaging using a hybrid X-ray and gamma-ray camera (#646)

M. Masubuchi1, A. Omata1, J. Kataoka1, H. Kato2, A. Toyoshima3, T. Teramoto3, K. Ooe2, Y. Liu2, K. Matsunaga2, T. Kamiya2, T. Watabe2, E. Shimosegawa2, J. Hatazawa2

1 Waseda University, Graduate School of Advanced Science and Engineering, Tokyo, Japan
2 Osaka University, Graduate School of Medicine, Osaka, Japan
3 Osaka University, Institute for Radiation Science, Osaka, Japan


In the field of nuclear medicine, X-ray and gamma-ray imaging techniques are crucial in both diagnosis and treatment. Therefore, the purpose of this study is to improve the accuracy of radiopharmaceutical distribution in a patient’s body. We developed a hybrid Compton camera that can perform broadband imaging. The hybrid Compton camera acts as a dual-modality by combining Compton and pinhole camera systems. The camera consists of two layers of scintillators, with a square hole of 3 mm in the front detector. The front detector acts as a scatter for high-energy photons as well as an active pinhole for low-energy photons. It is possible to analytically select the pinhole and Compton modes after data acquisition. In this study, using multiple hybrid Compton cameras, we performed three-dimensional (3D) reconstruction of 111In and 67Ga, which are used in nuclear medicine. We also performed double-photon simultaneous imaging of 133Ba using the information on the detection time for each camera. Consequently, we succeeded in reconstructing 3D images in pinhole and Compton modes, and the signal-to-noise ratio was improved by double-photon simultaneous imaging. These achievements will enable a more accurate diagnosis and treatment.

AcknowledgmentThis research was supported by JSPS KAKENHI Grant Number 20H00669. The Ga-67 and In-111 were supplied through Supply Platform of Short-lived Radioisotopes, supported by JSPS Grant-in-Aid for Scientific Research on Innovative Areas, Grant Number 16H06278.
Keywords: Compton camera, broadband imaging, three-dimensional (3D) imaging, double-photon simultaneous imaging
10:30 AM N-03-06

Real-time Imaging with Thick LaBr3: FPGA-Embedded Machine and Deep Learning for Nuclear Physics (#1094)

L. Buonanno1, 2, D. Di Vita1, 2, F. Canclini1, 2, G. Ticchi1, 2, F. Camera3, 2, M. Carminati1, 2, C. Fiorini1, 2

1 Politecnico di Milano, Dipartimento di Elettronica Informazione e Bioingegneria, Milano, Italy
2 Istituto Nazionale di Fisica Nucleare, Sezione di Milano, Milano, Italy
3 Università degli Studi Milano Statale, Dipartimento di Fisica, Milano, Italy


We present in this work a gamma spectrometer with real-time imaging capabilities, coupling a 3"x3" LaBr3 crystal to a 144-SiPM array. The position-sensitive spectrometer aims at state-of-the-art energy resolution and sub-centimeter spatial resolution of the gamma-photon interaction point in the scintillator, for post-processing correction of the relativistic Doppler broadening effect. The 16-channel GAMMA ASIC front-end accordingly favors a large number of 84 dB dynamic range channels integration and, in turn, the individual readout of SiPMs with accurate measurement of the scintillation light distribution. Two machine-learning or deep-learning classifiers are trained using a collimated 137Cs source, and cascaded in the FPGA-based DAQ, achieving 1.08 cm spatial resolution with a sub-μs data latency.

Keywords: gamma, imaging, sipm, asic, machine learning
10:45 AM N-03-07

Enabling PSD-capability for a High-density Channel Imager (#709)

M. Fang1, S. Pani1, A. Di Fulvio1

1 University of Illinois at Urbana Champaign, Nuclear, Plasma, and Radiological Engineering, Urbana, Illinois, United States of America


We demonstrated in simulation that the Citiroc1A ASIC can be configured to perform pulse shape discrimination. A PSD parameter is obtained as the ratio between the output of two shaping amplifiers. Each light readout signal is amplified by two independent front-end shaping amplifiers with shaping times optimized to maximize the difference between gamma-ray and neutron pulses. The differential responses of the two amplifiers hence mainly depend on the shape of the pulse and can be used to perform PSD. This capability, once implemented, will enable high-density channel PSD-capable imaging. We then designed and built a 56-channel SiPM readout board for the double-side readout of a CsI(Tl) array and EJ276, PSD capable, plastic scintillators. The board provided the input signal to four Citiroc1A modules and will be used to demonstrate the simulated PSD feature. Charge-integration-based PSD is both resource-intensive and slow for real-time applications such as imaging. Therefore, the possibility of performing PSD by using off-the-shelf readout electronics that we demonstrated in simulation could greatly facilitate multi-particle real-time imaging.

Keywords: Imaging, Scintillators
11:00 AM N-03-08

Radiographic Rolling Ball Viscometer for Molten Salts (#994)

P. B. Rose Jr1, N. D. B. Ezell2, R. C. Gallagher2, A. J. Martin3

1 Oak Ridge National Laboratory, Physics Division, Oak Ridge, Tennessee, United States of America
2 Oak Ridge National Laboratory, Nuclear Energy and Fuel Cycle Division, Oak Ridge, Tennessee, United States of America
3 Oak Ridge National Laboratory, Enrichment Science and Engineering Division, Oak Ridge, Tennessee, United States of America


Understanding and characterizing thermophysical properties of molten salts is critical for the development and deployment of Molten Salt Reactors.  These materials are being considered as heat transfer fluids, either coolants and/or fuels for the Department of Energy’s Advanced Reactor Technology program.  These materials can be difficult to measure due to high temperatures, corrosivity, and the volatile nature of molten salts.  This work addresses those issues with the development of a radiographic equivalent of a standard falling or rolling ball viscometer.  The mobile radiography system uses a mobile 150 kVp x-rays and a digital radiography panel for in-situ measurements of the potentially volatile materials.   In particular, the work presented here is focused on NIST traceable viscosity standards to validate the method and measurement in preparation for moving on to high temperature molten salts.  Three viscosity standard fluids were evaluated using the radiographic rolling ball viscometer and the calculated viscosities were found to be in agreement with literature values to within 2.25% at the worst case.


Submitted on May 6, 2021 for review.  Notice:  This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (

Keywords: molten salt, viscosity, digital radiography, imaging, falling ball

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