Beta-ray imaging system with γ-ray coincidence for multiple-tracer imaging

Tomonori Fukuchi, Seiichi Yamamoto, Jun Kataoka, Kei Kamada, Akira Yoshikawa, Yasuyoshi Watanabe, Shuichi Enomoto

Research output: Contribution to journalArticle

Abstract

Purpose: Beta-ray imaging systems are widely used for various biological objects to obtain a two-dimensional (2D) distribution of β-ray emitting radioisotopes. However, a conventional β-ray imaging system is unsuitable for multiple-tracer imaging, because the continuous energy distribution of β-rays complicates distinguishing among different tracers by energy information. Therefore, we developed a new type of β-ray imaging system, which is useful for multiple tracers by detecting coincidence γ-rays with β-rays, and evaluated its imaging performance. Methods: Our system is composed of position-sensitive β-ray and γ-ray detectors. The former is a 35 × 35 × 1-mm3 Ce-Doped((La, Gd)2Si2O7) (La-GPS) scintillation detector, which has a 300-µm pitch of pixels. The latter is a 43 × 43 × 16-mm3 bismuth germanium oxide (BGO) scintillation detector. Both detectors are mounted on a flexible frame and placed in a user-selectable position. We experimentally evaluated the performance of the β-ray detector and the γ-ray efficiencies of the γ-ray detector with different energies, positions, and distances. We also conducted point sources and phantom measurements with dual isotopes to evaluate the system performance of multiple-tracer imaging. Results: For the β-ray detector, the β-ray detection efficiencies for 45Ca (245-keV maximum energy) and 90Sr/90Y (545 and 2280-keV maximum energy) were 14.3% and 21.9%, respectively. The total γ-ray detection efficiency of the γ-ray detector for all γ-rays from 22Na (511-keV annihilation γ-rays and a 1275-keV γ-ray) in the center position with a detector distance of 20 mm was 17.5%. From a point-source measurement using 22Na and 90Sr/90Y, we successfully extracted the position of a positron-γ emitter 22Na. Furthermore, for a phantom experiment using 45Ca and 18F or 18F and 22Na, we successfully extracted the distribution of the second tracer using the annihilation γ-ray or de-excitation γ-ray coincidence. In all the imaging experiments, the event counts of the extracted images were consistent with the counts estimated by the measured γ-ray efficiencies. Conclusions: We successfully demonstrated the feasibility of our β-ray autoradiography system for imaging multiple isotopes. Since our system can identify not only a β-γ emitter but also a positron emitter using the coincidence detection of annihilation γ-rays, it is useful for PET tracers and various new applications that are otherwise impractical.

Original languageEnglish
Pages (from-to)587-596
Number of pages10
JournalMedical Physics
Volume47
Issue number2
DOIs
Publication statusPublished - 2020 Feb 1

Keywords

  • coincidence measurement
  • multiple tracers
  • scintillation detector
  • β-ray
  • β-ray imaging
  • γ-ray

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

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    Fukuchi, T., Yamamoto, S., Kataoka, J., Kamada, K., Yoshikawa, A., Watanabe, Y., & Enomoto, S. (2020). Beta-ray imaging system with γ-ray coincidence for multiple-tracer imaging. Medical Physics, 47(2), 587-596. https://doi.org/10.1002/mp.13947