Positron emission tomography with additional γ-ray detectors for multiple-tracer imaging

Area of Science:

• Nuclear Medicine
• Medical Imaging
• Biophysics

Background:

• Positron emission tomography (PET) is a valuable in vivo imaging technique for quantifying radiotracer distribution.
• Conventional PET is limited to single-tracer imaging due to the fixed energy of annihilation photons.
• Distinguishing multiple tracers is challenging as their annihilation photons share the same energy signature.

Purpose of the Study:

• To develop and evaluate a novel multi-isotope PET (MI-PET) system capable of simultaneous multi-tracer imaging.
• To overcome the limitations of conventional PET for simultaneous quantitative imaging of multiple radiotracers.
• To assess the performance of the MI-PET system in phantom and in vivo mouse studies.

Main Methods:

• Developed an MI-PET system integrating a standard PET scanner with additional gamma-ray detectors (BGO).
• The system distinguishes tracers by detecting prompt gamma rays unique to each radionuclide.
• Simultaneous acquisition of double (PET) and triple (PET + prompt gamma) coincidence events was enabled.
• Dual-radionuclide imaging (18F and 22Na) was performed using phantoms and a mouse model.

Main Results:

• The MI-PET system achieved a maximum detection efficiency of approximately 7% for 1275 keV gamma rays from 22Na.
• Dual-radionuclide imaging demonstrated preserved PET spatial resolution and quantitative accuracy for the second tracer.
• Successful simultaneous acquisition of double and triple coincidence events from a mouse was achieved.
• Reconstructed dual-tracer distributions in the mouse were physiologically and pharmacokinetically reasonable.

Conclusions:

• The developed MI-PET system demonstrates the feasibility of simultaneous multi-tracer imaging.
• This approach enables quantitative reconstruction of multiple-tracer images.
• The MI-PET system holds significant promise for analyzing complex multiple-molecular dynamics in vivo.