[¹⁸F]FNDP PET neuroimaging test–retest repeatability and whole-body dosimetry in humans

Purpose: Soluble epoxide hydrolase (sEH) is an enzyme that shapes immune signaling through its role in maintaining the homeostasis of polyunsaturated fatty acids and their related byproducts. [¹⁸F]FNDP is a radiotracer developed for use with positron emission tomography (PET) to image sEH, which has been applied to imaging sEH in the brains of healthy individuals. Here, we report the test–retest repeatability of [¹⁸F]FNDP brain PET binding and [¹⁸F]FNDP whole-body dosimetry in healthy individuals. Methods: Seven healthy adults (4 men, 3 women, ages 40.1 ± 4.6 years) completed [¹⁸F]FNDP brain PET on two occasions within a period of 14 days in a test–retest study design. [¹⁸F]FNDP regional total distribution volume (V_T) values were derived from modeling time-activity data with a metabolite-corrected arterial input function. Test–retest variability, mean absolute deviation, and intraclass correlation coefficient (ICC) were investigated. Six other healthy adults (3 men, 3 women, ages 46.0 ± 7.0 years) underwent [¹⁸F]FNDP PET/CT for whole-body dosimetry, which was acquired over 4.5 h, starting immediately after radiotracer administration. Organ-absorbed doses and the effective dose were then estimated. Results: The mean test–retest difference in regional V_T (ΔV_T) was 0.82 ± 5.17%. The mean absolute difference in regional V_T was 4.01 ± 3.33%. The ICC across different brain regions ranged from 0.92 to 0.99. The organs with the greatest radiation-absorbed doses included the gallbladder (0.081 ± 0.024 mSv/MBq), followed by liver (0.077 ± 0.018 mSv/MBq) and kidneys (0.063 ± 0.006 mSv/MBq). The effective dose was 0.020 ± 0.003 mSv/MBq. Conclusion: These data support a favorable test–retest repeatability of [¹⁸F]FNDP brain PET regional V_T. The radiation dose to humans from each [¹⁸F]FNDP PET scan is similar to that of other ¹⁸F-based PET radiotracers.