Positron emission tomography with additional c-ray detectors for multipletracer imaging

Tomonori Fukuchi*, Takashi Okauchi, Mika Shigeta, Seiichi Yamamoto, Yasuyoshi Watanabe, Shuichi Enomoto

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)


Purpose: Positron emission tomography (PET) is a useful imaging modality that quantifies the physiological distributions of radiolabeled tracers in vivo in humans and animals. However, this technique is unsuitable for multiple-tracer imaging because the annihilation photons used for PET imaging have a fixed energy regardless of the selection of the radionuclide tracer. This study developed a multiisotope PET (MI-PET) system and evaluated its imaging performance. Methods: Our MI-PET system is composed of a PET system and additional c-ray detectors. The PET system consists of pixelized gadolinium orthosilicate (GSO) scintillation detectors and has a ring geometry that is 95 mm in diameter with an axial field of view of 37.5 mm. The additional detectors are eight bismuth germanium oxide (BGO) scintillation detectors, each of which is 50 9 50 9 30 mm3, arranged into two rings mounted on each side of the PET ring with a 92-mminner diameter. This system can distinguish between different tracers using the additional c-ray detectors to observe prompt c-rays, which are emitted after positron emission and have an energy intrinsic to each radionuclide. Our system can simultaneously acquire double-(two annihilation photons) and triple-(two annihilation photons and a prompt c-ray) coincidence events. The system's efficiency for detecting prompt de-excitation c-rays was measured using a positron-c emitter, 22Na. Dual-radionuclide (18F and 22Na) imaging of a rod phantom and a mouse was performed to demonstrate the performance of the developed system. Our system's basic performance was evaluated by reconstructing two images, one containing both tracers and the other containing just the second tracer, from list-mode data sets that were categorized by the presence or absence of the prompt c-ray. Results: The maximum detection efficiency for 1275 keV c-rays emitted from 22Na was approximately 7% at the scanner's center, and the minimum detection efficiency was 5.1% at the edge of the field of view. Dual-radionuclide imaging of the point sources and rod phantom revealed that our system maintained PET's intrinsic spatial resolution and quantitative nature for the second tracer. We also successfully acquired simultaneous double-and triple-coincidence events from a mouse containing 18F-fluoro-deoxyglucose and 22Na dissolved in water. The dual-tracer distributions in the mouse obtained by our MI-PETwere reasonable from the viewpoints of physiology and pharmacokinetics. Conclusions: This study demonstrates the feasibility of multiple-tracer imaging using PET with additional c-ray detectors. This method holds promise for enabling the reconstruction of quantitative multiple-tracer images and could be very useful for analyzing multiple-molecular dynamics.

Original languageEnglish
Pages (from-to)2257-2266
Number of pages10
JournalMedical Physics
Issue number6
Publication statusPublished - 2017 Jun 1
Externally publishedYes


  • Dual-radionuclide imaging
  • Positron emission tomography
  • Positron gamma emitter
  • Small animal imaging

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging


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