The kinetics and reproducibility of 18F-Sodium Fluoride (NaF) PET imaging

Objectives Although Sodium Fluoride (18F-NaF) bone scanning has been used for many decades, recent advances in PET-CT camera technology mandate a reappraisal of recommended doses and scanning guidelines. We evaluated the kinetics of 18F-NaF using a current PET-CT scanner to reassess the recommended dose, optimal uptake period and inter-study reproducibility.

Methods In this prospective study, 73 patients underwent multiple sequential PET/CT images after receiving 3-5mCi 18F-NaF IV. Twenty-one of these patients underwent repeat baseline studies (mean interval 5 days) to evaluate reproducibility.

Results Imaging with doses in the range of 3-5mCi 18F-NaF produces excellent scan quality. Estimated Radiation dosimetry made using OLINDA1.0, yield an estimated Effective Dose (ED) of 0.062rem/mCi with the urinary bladder, osteogenic cells and the red marrow receiving the highest doses at 0.300, 0.288 and 0.104 rad/mCi respectively. Visual analysis shows that uptake in both normal and abnormal bone increase with time, however, the rate of increase decreases with time. A semi-automated workflow was created (MIM5.2) to provide objective uptake parameters, including the SUV10mean (mean SUV of all pixels within bone with SUV >10) and the mSUVmean (the average of the SUVmean of all malignant lesions identified by the algorithm). The rate of change between 60 and 120minutes for SUV10mean and mSUVmean is 0.1 %/minute. At 60minutes p.i. critical percent differences of 20.9% for SUV10mean and 33.2% for mSUVmean were achieved. This indicates that SUV changes must be greater than these critical values if they are to be considered “real” during treatment monitoring.

Conclusions 18F-NaF PET/CT images can be obtained with modest radiation exposures and can result in highly reproducible imaging parameters at a 60 minute uptake period. This may enable more quantitative measurement of metastatic bone disease.

Research Support Center for Cancer Research/ NCI Intramural Progra