High-resolution clustered pinhole (131)Iodine SPECT imaging in mice.

Area of Science:

• Nuclear medicine
• Medical imaging
• Radiochemistry

Background:

• High-resolution pre-clinical single-photon emission computed tomography (SPECT) is crucial for advancing radioiodine cancer therapies.
• High-energy gamma photons from iodine-131 (131I) can degrade image resolution due to pinhole edge penetration.
• Optimizing SPECT imaging for 131I requires specialized collimator designs to mitigate these effects.

Purpose of the Study:

• To introduce, optimize, and validate a dedicated high-energy clustered multi-pinhole collimator for 131I SPECT imaging in pre-clinical research.
• To improve image resolution and quantitative accuracy in SPECT imaging of 131I.

Main Methods:

• A SPECT-CT system (VECTor/CT) was equipped with a tungsten collimator featuring clustered pinholes.
• Image reconstruction utilized pixel-based ordered-subset expectation maximization (OSEM) with a dedicated 131I system matrix.
• System performance was evaluated using phantoms and in vivo static and dynamic 131I-NaI scans in mice.

Main Results:

• Achieved a reconstructed image resolution of 0.6 mm.
• Demonstrated quantitative accuracy of +3.6±3.5% for 131I uptake compared to the gold standard.
• Successfully visualized thyroid shape and 131I biodistribution in mice, enabling pharmacokinetic analysis with 15-second time frames.

Conclusions:

• High-resolution, quantitative, and dynamic 131I SPECT imaging in mice is feasible with a high-energy collimator and optimized system modeling.
• This technique facilitates the analysis of 131I uptake in small organs, crucial for developing and optimizing targeted cancer therapies.