SNM has issued guidelines to assist healthcare professionals in performance, interpretation and reporting the results of PET/CT bone scans performed with 18F-Fluoride.
18F-Fluoride, an IV-administered diagnostic molecular imaging agent used for identification of new bone formation, was approved by the FDA in 1972, but has been listed as a discontinued drug since 1984.
The use of new hybrid PET/CT systems has significantly improved the specificity of 18F- Fluoride imaging as the CT component of the study allows morphologic characterization of the functional lesion and more accurate differentiation between benign lesions and metastases, said SNM.
SNM stated that PET/CT 18F bone scans may be used to identify skeletal metastases, including localization and determination of the extent of disease at the time of initial diagnosis or following therapy. Insufficient information exists to recommend the following indications in all patients, but 18F imaging may be appropriate in certain individuals.
The results of prior imaging studies in patients should be reviewed, including plain film x-ray, CT, MR, bone scan and FDG PET/CT. Relevant prior studies should be directly compared to current imaging findings when possible, according to the guidelines.
18F-Fluoride is injected intravenously by direct venipuncture or intravenous catheter. The guidelines suggest that adult activity is 185-370 MBq (5-10 mCi). A higher activity (370 MBq, 10 mCi) may be used in obese patients. Pediatric activity should be weight-based (2.59 MBq/kg, 0.07 mCi/kg), using a minimum and maximum activity of 11 to 185 MBq (0.3 to 5 mCi).
Significant abnormalities should be verbally communicated to the appropriate healthcare provider if a delay in treatment might result in significant morbidity. An example of such an abnormality would be a lesion with a high risk of pathologic fracture. An abnormality suggesting a high likelihood of unexpected malignancy should also be communicated verbally.
Written documentation of verbal reporting should be made in the medical record, usually as part of the PET/CT report, and the contents of the report should include study identification, clinical information, procedure description, description of the findings and impression of diagnosis.
The effective dose for 18F is 0.024 mSv/MBq (0.089 mrem/mCi). For a typical activity of 370 MBq (10 mCi), the effective dose is 10 mSv (1 rem).
For comparison, the effective dose for 99mTc-methylene diphosphonate (MDP) is 0.0057 mSv/MBq (0.021 rem/mCi). For a typical activity of 925 MBq (25 mCi), the effective dose is 5.3 mSv (0.53 rem). Thus, the radiation dose to patients is approximately 70 percent higher using 18F-fluoride (370 MBq x 0.024 mSv/MBq = 8.9 mSv) compared to 99mTc-MDP, SNM reported.