3D position of radiation sources using an automated gamma camera and ML algorithm with energy-dependent response functions

Wonho Lee, David Wehe

Research output: Contribution to journalConference articlepeer-review

5 Citations (Scopus)


Portable γ-ray imaging systems operating from 100keV to 3MeV are used in nuclear medicine, astrophysics and industrial applications. 2D images of γ-rays are common in many fields using radiation-detection systems (Appl. Opt. 17 (3) (1978) 337; IEEE Trans. Nucl. Sci. Ns- 31 (1984) 771; IEEE Trans. Nucl. Sci. NS- 44 (3) (1997) 911). In this work, the 3D position of a radiation source is determined by a portable gamma-ray imaging system. 2D gamma-ray images were obtained from different positions of the gamma camera and the third dimension, the distance between the detector and the radiation source, was calculated using triangulation. The imaging system consists of a 4 × 4 array of CsI(Tl) detectors coupled to photodiode detectors that are mounted on an automated table which can precisely position the angular axis of the camera. Lead shields the detector array from the background radiation. Additionally, a CCD camera is attached to the top of the gamma camera and provides coincident 2D visual information. The inferred distances from the center of the two measurement points and a radiation source had less than a 3% error within a range of 3m. The radiation image from the gamma camera and the visual image from CCD camera are superimposed into one combined image using a maximum-likelihood (ML) algorithm to make the image more precise. The response functions for the ML algorithm depend on the energy of incident radiation, and are obtained from both experiments and simulations. The energy-dependent response functions are shown to yield better imaging performance compared with the fixed energy response function commonly used previously.

Original languageEnglish
Pages (from-to)270-275
Number of pages6
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Issue number1-2
Publication statusPublished - 2004 Sept 21
Externally publishedYes
EventProceedings of the 5th International Worshop on Radiation - Riga, Latvia
Duration: 2003 Sept 72003 Sept 11


  • 3D-Position
  • Gamma camera
  • Maximum-likelihood method

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Instrumentation


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