dAcquisition setting optimization and quantitative imaging for 124I studies with the Inveon microPET-CT system

Area of Science:

• Small animal imaging
• Preclinical research
• Nuclear medicine

Background:

• Noninvasive multimodality imaging is vital for preclinical assessment of radionuclide therapy, including biodistribution, pharmacokinetics, and tumor response.
• Iodine-124 (124I) PET imaging offers promise but requires precise activity quantification due to its unique decay scheme.
• Optimizing acquisition settings and correction processing is essential for accurate 124I quantification.

Purpose of the Study:

• To determine optimal acquisition parameters for 124I imaging in small animals using the Inveon PET/CT system.
• To evaluate the impact of various image reconstruction algorithms and corrections on 124I activity quantification.
• To establish best practices for small animal 124I PET imaging.

Main Methods:

• Noise Equivalent Count Rate (NECR), Scatter Fraction (SF), and Gamma-Prompt Fraction (GF) were used to optimize acquisition parameters for mouse and rat phantoms.
• Image quality was assessed using a National Electrical Manufacturers Association (NEMA) phantom.
• Reconstruction algorithms included 2D filtered back projection, 2DOSEM, and 3DOSEM/MAP, with and without attenuation, scatter, and gamma-prompt corrections.

Main Results:

• Optimal energy windows for 124I were determined as 390-550 keV for rat phantoms and 400-590 keV for mouse phantoms.
• The 3DOSEM/MAP algorithm with attenuation and scatter corrections underestimated activity by 9.9%, while adding gamma-prompt correction resulted in a 23% underestimation.
• Corrections for attenuation, scatter, and gamma-prompt significantly reduced residual signal in cold regions.

Conclusions:

• Optimal energy windows were identified using NECR, SF, and GF evaluations.
• Further assessment of image quality and activity quantification is necessary to select the most suitable reconstruction algorithm and corrections for 124I small animal imaging.
• This research provides a foundation for accurate preclinical 124I PET studies.