In this study, we evaluated the biodistribution of the 18F-/18F-FDG administration, compared with separate 18F-NaF and 18F-FDG administrations. We also estimated the interaction of 18F-NaF and 18F-FDG in the 18F-/18F-FDG administration by semiquantitative analysis. Methods: We retrospectively analyzed the data of 49 patients (39 men, 10 women; mean age ± SD, 59.3 ± 15.2 y) who underwent separate 18F-FDG PET/CT and 18F-NaF PET/CT scans as well as 18F-/18F-FDG PET/CT sequentially. The most common primary diagnosis was prostate cancer (n 5 28), followed by sarcoma (n 5 9) and breast cancer (n 5 6). The mean standardized uptake values (SUVs) were recorded for 18 organs in all patients, and maximum SUV and mean SUV were recorded for all the identified malignant lesions. We also estimated the 18F-/18F-FDG uptake as the sum of18F-FDG uptake and adjusted 18F-NaF uptake based on the ratio of18F-NaF injected dose in 18F-/18F-FDG PET/CT. Lastly, we compared the results to explore the interaction of 18F-FDG and18F-NaF uptake in the 18F-/18F-FDG scan. Results: The18F-/18F-FDG uptake in the cerebral cortex, cerebellum, parotid grand, myocardium, and bowel mostly reflected the18F-FDG uptake, whereas the uptake in the other analyzed structures was influenced by both the 18F-FDG and the 18F-NaF uptake. The 18F-/18F-FDG uptake in extraskeletal lesions showed no significant difference when compared with the uptake from the separate18F-FDG scan. The18F-/18F-FDG uptake in skeletal lesions reflected mostly the 18F-NaF uptake. The tumor-to-background ratio of 18F-/18F-FDG in extraskeletal lesions showed no significant difference when compared with that from 18F-FDG alone (P 5 0.73). For skeletal lesions, the tumor-to-background ratio of 18F-/18F-FDG was lower than that from 18F-NaF alone (P , 0.001); however, this difference did not result in missed skeletal lesions on the 18F-/18F-FDG scan. Conclusion: The understanding of the biodistribution of radiopharmaceuticals and the lesion uptake of the 18F-/18F-FDG scan as well as the variations compared with the uptake on the separate 18F-FDG PET/CT and 18F-NaF PET/CT are valuable for more in-depth evaluation of the combined scanning technique.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging