Abstract
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Objectives We previously reported the pilot evaluation of a simultaneous PET/MRI scanner with TOF capability (1), as well as the use of combined 18F NaF/18F FDG PET/CT in cancer patients (2,3). Here we prospectively compared the combined 18F NaF/18F FDG PET/ MRI against 99mTc-MDP bone scintigraphy in patients with breast and prostate cancers.
Methods 30 patients referred for 99mTc-MDP bone scans were prospectively enrolled from Oct 2014 to Jan 2016. The cohort included 23 men with prostate cancer and 7 women with breast cancer, 41 - 85 year-old (average 65 ± 11). 18F NaF (0.7-2.2 mCi, mean: 1.1 mCi) and 18F FDG (3.6-5.5 mCi, mean: 4.2 mCi) were subsequently injected from separate syringes. The PET/MRI was done 6-30 days (average 9.3 ± 3.2) after bone scan. The whole body MRI protocol consisted of MRAC, T2-weighted, DWI, and contrast-enhanced T1-weighted imaging. Lesions detected with each test were tabulated and the results were compared.
Results All patients tolerated the PET/MRI exam and PET image quality was diagnostic despite the marked reduction in the administered dosage of radiopharmaceuticals (80% less for 18F NaF and 67% less for 18F FDG compared to standard PET/CT protocols). 11 patients had no bone metastases identified on either scans. Bone scintigraphy and PET/MRI showed osseous metastases in 16 patients, but more numerous bone findings were noted on PET/MRI than on bone scintigraphy in 8 of these patients. 1 patient had a negative bone scan, but bone metastases were seen on PET/MRI. Lesions outside the skeleton were identified by PET/MRI in 3 patients.
Conclusions The combined 18F NaF/18F FDG PET/MRI is superior to 99mTc-MDP scintigraphy for evaluation of skeletal disease extent. Further, it detected extra-skeletal disease that may change the management of these patients, while allowing a significant reduction in radiation exposure from lower dosages of PET radiopharmaceuticals administered. 18F NaF/18F FDG PET/MRI appears well suited for detection of metastases in patients with breast and prostate cancers.