Prospective comparison of combined 18F-FDG and 18F-NaF PET/CT vs. 18F-FDG PET/CT imaging for detection of malignancy
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Typically, 18F-FDG PET/CT and 18F-NaF PET/CT scans are done as two separate studies on different days to allow sufficient time for the radiopharmaceutical from the first study to decay. This is inconvenient for the patients and exposes them to two doses of radiation from the CT component of the examinations. In the current study, we compared the clinical usefulness of a combined 18F-FDG/18F-NaF PET/CT scan with that of a separate 18F-FDG-only PET/CT scan.
There were 62 patients enrolled in this prospective trial. All had both an 18F-FDG-alone PET/CT scan and a combined 18F-FDG/18F-NaF PET/CT scan. Of the 62 patients, 53 (85%) received simultaneous tracer injections, while 9 (15%) received 18F-NaF subsequent to the initial 18F-FDG dose (average delay 2.2 h). Images were independently reviewed for PET findings by two Board-Certified nuclear medicine physicians, with discrepancies resolved by a third reader. Interpreters were instructed to only report findings that were concerning for malignancy. Reading the 18F-FDG-only scan first for half of the patients controlled for order bias.
In 15 of the 62 patients (24%) neither the 18F-FDG-only PET/CT scan nor the combined 18F-FDG/18F-NaF PET/CT scan identified malignancy. In the remaining 47 patients who had PET findings of malignancy, a greater number of lesions were detected in 16 of 47 patients (34%) using the combined 18F-FDG/18F-NaF PET/CT scan compared to the 18F-FDG-only PET/CT scan. In 2 of these 47 patients (4%), the 18F-FDG-only scan demonstrated soft tissue lesions that were not prospectively identified on the combined study. In 29 of these 47 patients (62%), the combined scan detected an equal number of lesions compared to the 18F-FDG-only scan. Overall, 60 of all the 62 patients (97%) showed an equal or greater number of lesions on the combined scan than on the 18F-FDG-only scan.
The current study demonstrated that 18F-FDG and 18F-NaF can be combined in a single PET/CT scan by administering the two radiopharmaceuticals simultaneously or in sequence on the same day. In addition to patient convenience and reduced radiation exposure from the CT component, the combined 18F-FDG/18F-NaF PET/CT scan appeared to increase the sensitivity for detection of osseous lesions compared to the 18F-FDG-only PET/CT scan in the studied population.
KeywordsPET/CT combined scan PET/CT bone imaging 18F-NaF PET/CT Osseous lesion detection
This research was supported in part by NCI ICMIC CA114747 (S.S.G.) and clinical studies were supported in part by the Doris Duke Foundation and Canary Foundation (S.S.G.). We would also like to thank Mr. Atul Gada (senior technologist) whose help and support was immense.
Conflicts of interest
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