Kinetic metrics of ¹⁸F-FDG in normal human organs identified by systematic dynamic total-body positron emission tomography

To investigate the kinetic metrics of 2-[¹⁸F]-fluoro-2-deoxy-d-glucose (¹⁸F-FDG) in normal organs by using dynamic total-body (TB) positron emission tomography (PET).

Dynamic TB-PET was performed for nine healthy volunteers. Time-to-activity curves (TACs) were obtained by drawing regions of interest in the organs. A two-tissue compartment model was fitted for each tissue TAC. Constant rates, including k₁, k₂, and k₃, and the metabolic rate of FDG (MRFDG) were obtained. The parameter statistics, including the average, standard deviation, coefficient of variance, and inter-site and inter-individual variances, were compared.

Constant rates and MRFDG varied significantly among organs and subjects, but not among sides or sub-regions within an organ. The mean k₁ and k₂ ranged from 0.0158 min⁻¹ in the right lower lung to 1.1883 min⁻¹ in the anterior wall of the left ventricle (LV) myocardium and from 0.1116 min⁻¹ in the left parietal white matter to 4.6272 min⁻¹ in the left thyroid, respectively. The k₃ was lowest in the right upper area of the liver and highest in the septal wall of the LV myocardium. Mean MRFDG ranged from 23.1696 μmol/100 g/min in the parietal cortex to 0.5945 μmol/100 g/min in the lung. Four groups of organs with similar kinetic characteristics were identified: (1) the cerebral white matter, lung, liver, muscle, bone, and bone marrow; (2) cerebral and cerebellar cortex; (3) LV myocardium and thyroid; and (4) pancreas, spleen, and kidney.

The kinetic rates and MRFDG significantly differed among organs. The kinetic metrics of FDG parameters in normal organs can serve as a reference for future dynamic PET imaging and research.