Far-Field 3-D Localization of Radioactive Hotspots via Four-Eyes Stereo Gamma Camera

Abstract

In the fields of radiation environment monitoring and unknown radioactive materials search, locating the far-field gamma-ray sources with high accurate coordinates is an important and necessary capability for a gamma imager. However, traditional coded gamma-ray imaging systems only provide 2-D radiation images without distance information. In this work, a four-eyes stereo gamma camera is proposed, which consists of four independent coded aperture detectors with an adjacent spacing of 286 mm. Each detector is comprised of pixelated scintillators with a pixel array of 44 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times44$ </tex-math></inline-formula> , forming a global detection area of 140 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times140$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The ranging capability is related to the resolution and the adjacent spacing of the detectors. With the setup of the above device, the traditional binocular-based ranging method has a short measurement range and a large measurement deviation. Here, a min-area distance measurement algorithm based on a four-eyes stereo gamma camera is proposed, combined with “manual” fine sampling and Gaussian fitting method to successfully achieve the high-precision localization of the far-field source. The simulation results show that compared with the traditional binocular-based ranging method, the min-area method based on a four-eyes stereo camera lengthens the range from 20 m to more than 50 m and improves the ranging accuracy within 20 m by more than six times. The accuracy of 20 and 50 m is less than 1.4 m (7.13%) and 10.5 m (21%), respectively. The reliability of the simulation results has been verified by experiments. Furthermore, the ranging capability of this algorithm for multipoint sources in the far field has been verified.