Dynamic Total-Body PET Imaging Unfolds [ 11 C]Choline Kinetics and Dosimetry in Primary Hyperparathyroidism

This study investigated the biodistribution profile, kinetic constants, and dosimetry of [¹¹C]choline in patients with primary hyperparathyroidism (pHPT) using total-body dynamic PET (dPET) imaging, to establish a baseline and standard reference for clinical practice. Methods: A 50-min dPET acquisition followed by a 20-min static acquisition at 100 ± 10 min postinjection was performed on 6 patients with a clinical diagnosis of primary hyperparathyroidism. Whole-body [¹¹C]choline distribution and pharmacokinetics were evaluated by SUV, tissue uptake, organ-absorbed doses, and, finally, multitime graphical analysis and kinetic modeling with compartment models. Results: Rapid whole-body uptake of [¹¹C]choline was observed, with adequate image quality for presurgical localization of parathyroid adenomas seen from 5 min postinjection onward. Average uptake values after 50 min for liver (17.61% ± 2.82%) and bowel (5.77% ± 1.80%), compared with kidneys (2.77% ± 0.24%) and urinary bladder (0.21% ± 0.16%), suggested alternative excretion pathways for [¹¹C]choline other than renal clearance. Gallbladder (0.019 ± 0.004 mGy/MBq), liver (0.037 ± 0.008 mGy/MBq), pancreas (0.022 ± 0.005 mGy/MBq), kidneys (0.016 ± 0.005 mGy/MBq), and spleen (0.023 ± 0.009 mGy/MBq) were the organs with the highest observed effective doses. These organs also showcased extreme values among $K_1$, $k_2$, $k_3$, and $k_4$, which provide them with the most distinctive kinetic patterns. Parathyroid adenomas exhibited significantly higher k₃, K_i, and distribution volume, and lower K₁, than reference thyroid tissue (P < 0.05). Conclusion: The high adenoma-to-background uptake of [¹¹C]choline observed 5 min postinjection onward may facilitate swift imaging protocols. The total-body dynamic approach further highlighted the pivotal role of liver metabolism, minimal renal excretion, and unique kinetic behaviors of parathyroid adenomas. These data advance our understanding of [¹¹C]choline’s uptake and may serve as a reference for future dPET studies.