The kinetics and reproducibility of 18F-sodium fluoride for oncology using current PET camera technology

We evaluated the kinetics of (18)F-sodium fluoride (NaF) and reassessed the recommended dose, optimal uptake period, and reproducibility using a current-generation PET/CT scanner.

In this prospective study, 73 patients (31 patients with multiple myeloma or myeloma precursor disease and 42 with prostate cancer) were injected with a mean administered dose of 141 MBq of (18)F-NaF. Sixty patients underwent 3 sequential sessions of 3-dimensional PET/CT of the torso beginning approximately 15 min after (18)F-NaF injection, followed by whole-body 3-dimensional PET/CT at 2 h. The remaining 13 prostate cancer patients were imaged only at 2 and 3 h after injection. Twenty-one prostate cancer patients underwent repeated baseline studies (mean interval, 5.9 d) to evaluate reproducibility.

The measured effective dose was 0.017 mSv/MBq, with the urinary bladder, osteogenic cells, and red marrow receiving the highest doses at 0.080, 0.077, and 0.028 mGy/MBq, respectively. Visual analysis showed that uptake in both normal and abnormal bone increased with time; however, the rate of increase decreased with time. A semiautomated workflow provided objective uptake parameters, including the mean standardized uptake value of all pixels within bone with SUVs greater than 10 and the average of the mean SUV of all malignant lesions identified by the algorithm. The values of these parameters for the images beginning at approximately 15 min and approximately 35 min were significantly different (0.3% change per minute). Differences between the later imaging time points were not significant (P < 0.01). Repeated baseline studies showed high intraclass correlations (>0.9) and relatively low critical percentage change (the value above which a change can be considered real) for these parameters. The tumor-to-normal bone ratio, based on the maximum SUV of identified malignant lesions, decreased with time; however, this difference was small, estimated at approximately 0.16%/min in the first hour.

(18)F-NaF PET/CT images obtained with modest radiation exposures can result in highly reproducible imaging parameters. Although the tumor-to-normal bone ratio decreases slightly with time, the high temporal dependence during uptake periods less than 30 min may limit accurate quantitation. An uptake period of 60 ± 30 min has limited temporal dependence while maintaining a high tumor-to-normal bone ratio.