Biokinetics of 18F-choline studied in four prostate cancer patients

Biokinetic data are important when calculating the absorbed dose to the patients and can also be used to find the optimal time between injection and imaging. To the authors' knowledge, there are no published biokinetic data in humans for (18)F-choline, except some distribution data at single time points. Four patients with suspicion of metastases due to biochemical recurrence (measurable prostate-specific antigen in plasma) after radical prostatectomy were injected with (18)F-choline. Four whole-body PET/CT images were taken with 1 h interval, starting immediately after injection. Blood samples were taken and all urine was collected for 3.5 h. The corrected decay activity content in the kidneys was 22-37 % higher immediately after injection when compared with the later time points. The highest activity concentration was found in kidneys (43 kBq ml(-1)). The organ with highest activity content was the liver (11 % of injected activity, % IA). Thirty minutes after the injection 4-16 % IA was left in the blood. Less than 9 % IA was excreted with the urine during the first 3.5 h after injection.