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Publishing Language: Chinese

Large field-of-view radioactive source location system based on a coded aperture and pinholes

Yujie LIU1,2Tiantian DAI3Nianming JIANG4Yansong HOU4Qingyang WEI1,2,4( )
School of Automation and Electrical Engineering, University of Science and Technology Beijing, Beijing 100083, China
Beijing Engineering Research Center of Industrial Spectrum Imaging, University of Science and Technology Beijing, Beijing 100083, China
Department of Radiation Oncology, China-Japan Friendship Hospital, Beijing 100029, China
Beijing Novel Medical Equipment Ltd., Beijing 102206, China
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Abstract

Objective

Gamma-ray detection using a nuclear radiation locator is critical for monitoring, locating, and processing radioactive sources. In recent years, gamma cameras based on coded aperture imaging techniques have been extensively utilized to identify and monitor radioactive sources. However, these detectors have limitations in terms of the imaging field. To accurately determine the specific location of radioactive sources, constant adjustment of the detection angle is required, which is often time-consuming. To expand the detection field, multiple coded aperture cameras can be used simultaneously, but this approach increases cost and equipment complexity. Some researchers have attempted to combine Compton and coded aperture imaging techniques. While the Compton camera can extend the field-of-view (FOV) to 4p, this method is complicated, costly, and limited to detecting high-energy rays. As a result, the combination of these two techniques proves inadequate when searching for low-energy sources. In this work, we proposed a system and method for locating radioactive sources with a large FOV based on combining a coded aperture with pinholes. This method addresses the limited FOV issue encountered in the aforementioned system.

Methods

The coded aperture component of the system uses a modified uniformly redundant array as the uniform redundant array mask. The base mode class is 11, with a unit size of 3.3 mm?.3 mm, leading to a total size of 69.3 mm?9.3 mm. The mask thickness is 9 mm, and tungsten is used as the material. The detector section includes a 26?6 NaI (Tl) array, where each crystal pixel has dimensions of 1.45 mm?.45 mm?.00 mm. A crystal gap of 0.2 mm exists between each pixel, and the distance between the center of the coded aperture and the position-sensitive sensor is 77.5 mm.For the pinhole part of the system, a tapered pinhole with a center size of 4 mm is used. The pinhole is embedded in a shield with equally large pinholes on all four sides. For performance assessment of the system, Monte Carlo simulation experiments were performed with GATE software. A large FOV radioactive source location system is constructed, and simulation data are produced. MATLAB is employed to process the simulation data, compute the system transmission matrix using the Sidden algorithm, and conduct reconstruction using the maximum likelihood expectation maximization method. The projection and reconstruction results of the point sources at various positions are compared and analyzed. Thus, this work shows a comprehensive analysis and assessment of the developed system for locating radioactive sources with a large FOV using a combination of coded aperture and pinhole imaging techniques.

Results

The results indicate that the full coding and semipseudo-film FOV of the coded aperture camera are 19.33?and 70.80? respectively, and the added pinhole extends the FOV of the system to 123.40? The developed system attains an angular resolution of 2.95?within the coded aperture FOV and 6.30?within the extended pinhole FOV, effectively imaging a 10 mCi radioactive source at a distance of 3 m.

Conclusions

The developed wide FOV radiation source location system and method effectively address the limited imaging field of the coded aperture camera.

CLC number: O572.21+2 Document code: A Article ID: 1000-0054(2024)08-1516-05

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Journal of Tsinghua University (Science and Technology)
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Cite this article:
LIU Y, DAI T, JIANG N, et al. Large field-of-view radioactive source location system based on a coded aperture and pinholes. Journal of Tsinghua University (Science and Technology), 2024, 64(8): 1516-1520. https://doi.org/10.16511/j.cnki.qhdxxb.2024.27.003

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Received: 21 September 2023
Published: 15 August 2024
© Journal of Tsinghua University (Science and Technology). All rights reserved.