Evaluation of reference tissue model and tissue ratio method for 5-HTT using [(123)I] ADAM tracer

Area of Science:

• Neuroscience
• Radiochemistry
• Nuclear Medicine

Background:

• Serotonin transporters (5-HTT) are key targets for antidepressants.
• [(123)I] ADAM is a novel radiotracer for imaging central nervous system 5-HTT.

Purpose of the Study:

• Compare four-parameter (FPM) and three-parameter (TPM) models for 5-HTT quantification.
• Evaluate tracer kinetic models against the tissue ratio (TR) method.
• Assess the utility of the cerebellum as an indirect input function.

Main Methods:

• Non-invasive reference tissue modeling (RTM) using SPECT.
• Comparison of kinetic models (FPM, TPM) and TR method.
• Utilized [(123)I] ADAM radiotracer.

Main Results:

• Binding potential (BP) values were similar between FPM and TPM.
• TPM showed a smaller standard deviation for the ratio of delivery (R(1)) compared to FPM.
• Significant correlation observed between BP and specific uptake ratio (SUR).

Conclusions:

• Simplified reference tissue model (SRTM) is recommended for its stability and ease of use in brain SPECT studies.
• The correlation between BP and SUR supports the TR method for 5-HTT quantification, potentially avoiding arterial sampling.