Total-body dynamic PET/CT imaging reveals kinetic distribution of [N]NH in normal organs.

PURPOSE

To systematically investigate kinetic metrics and metabolic trapping of [N]NH in organs.

METHODS

Eleven participants performed total-body [N]NH dynamic positron emission tomography (PET). Regions of interest were drawn in organs to obtain time-to-activity curves (TACs), which were fitted with an irreversible two-tissue compartment model (2TC) to investigate constant rates K, k and k, and to calculate Ki. Additionally, one-tissue compartment model using full data (1TC) and the first four minutes of data (1TC) were fitted to TAC data. K and k were compared among different models to assess [N]NH trapping in organs.

RESULTS

Kinetic rates of [N]NH varied significantly among organs. The mean K ranged from 0.049 mL/cm/min in the muscle to 2.936 mL/cm/min in the kidney. The k and k were lowest in the liver (0.001 min) and in the pituitary (0.009 min), while highest in the kidney (0.587 min) and in the liver (0.800 min), respectively. The Ki was largest in the myocardium (0.601 ± 0.259 mL/cm/min) while smallest in the bone marrow (0.028 ± 0.022 mL/cm/min). Three groups of organs with similar kinetic characteristics were revealed: (1) the thyroid, the lung, the spleen, the pancreas, and the kidney; (2) the liver and the muscle; and (3) the cortex, the white matter, the cerebellum, the pituitary, the parotid, the submandibular gland, the myocardium, the bone, and the bone marrow. Obvious k was identified in multiple organs, and significant changes of K in multiple organs and k in most organs were found between 2TC and 1TC, but both K and k were comparable between 2TC and 1TC.

CONCLUSION

The kinetic rates of [N]NH differed among organs with some have obvious N-anmmonia trapping. The normal distribution of kinetic metrics of N-anmmonia in organs can serve as a reference for its potential use in tumor imaging.