¹⁸⁸Re image performance assessment using small animal multi-pinhole SPECT/PET/CT system

Area of Science:

• Nuclear Medicine
• Medical Imaging
• Radiochemistry

Background:

• Pre-clinical SPECT/PET/CT systems are crucial for evaluating novel radiotracers.
• Rhenium-188 (¹⁸⁸Re) is a promising radionuclide for targeted radionuclide therapy and imaging.
• Optimizing imaging protocols for ¹⁸⁸Re is essential for accurate pre-clinical studies.

Purpose of the Study:

• To evaluate the performance of a pre-clinical SPECT/PET/CT system for ¹⁸⁸Re imaging.
• To compare the efficacy of two multi-pinhole collimators: ultra-high resolution collimator (UHRC) and high-energy ultra-high resolution collimator (HE-UHRC).

Main Methods:

• Phantom studies using micro-Jaszczak and custom phantoms to assess spatial resolution, contrast, CNR, and quantification accuracy.
• Comparison of ¹⁸⁸Re images with ^99mTc (gold standard).
• Analysis of energy spectra and Monte Carlo simulations of the UHRC.
• In vivo validation using a mouse model injected with ¹⁸⁸Re-microspheres.

Main Results:

• ¹⁸⁸Re imaging achieved spatial resolution comparable to ^99mTc.
• HE-UHRC demonstrated superior contrast and CNR for ¹⁸⁸Re imaging compared to UHRC.
• Quantitative accuracy for ¹⁸⁸Re was within 10% error for both collimators, similar to ^99mTc.
• ¹⁸⁸Re imaging with UHRC was significantly impacted by down-scattered photons, while HE-UHRC showed better performance.
• Mouse studies revealed similar biodistribution patterns for ¹⁸⁸Re-microspheres with both collimators.

Conclusions:

• The VECTor/CT system provides quantitatively accurate ¹⁸⁸Re images with quality comparable to ^99mTc.
• The HE-UHRC is recommended for ¹⁸⁸Re imaging on the VECTor/CT system due to its ability to mitigate high-energy photon penetration.
• Optimized collimator selection is critical for high-quality ¹⁸⁸Re SPECT imaging in pre-clinical research.