Comparison of 18F sodium fluoride PET/CT and diffusion-weighted whole-body MR imaging with background body signal suppression for the imaging of skeletal metastasis in carcinoma prostate

Objectives We designed a study for head-to-head comparison of F-18 Fluoride (NaF) PET/CT and DWIBS for the detection of skeletal metastasis in prostate cancer patients.

Methods 36 histopathologically proven newly diagnosed prostate cancer patients (Age=67.05+ 6.09 years) were prospectively enrolled to undergo F-18 NaF PET/CT and DWIBS within one week. The average activity administered for NaF was 154 + 30.9 MBq. Imaging was started 30 minutes post-injection on a 64-slice Biograph mCT scanner (Siemens). PET scans were evaluated for site and number of lesions and corresponding CT changes. All lesions with abnormal uptake corresponding to sclerotic lesions on CT were considered as metastasis. Transverse breath-hold DWI sequence (TR/TE, 2500/50 and 60 ms; slice thickness, 5 mm; interslice gap of 1 mm; FOV, 36-40 cm; matrix, 128 × 128; sensitivity encoding [SENSE] factor, 2) was obtained by using a single-shot spin-echo echo-planar sequence without administration of contrast material with b values of 0 , 500,800 and 1000 sec/mm2..Lesions appearing hyperintense at b value 1000 was considered as metastasis. Each scan was evaluated, separately by an experienced nuclear physician and a radiologist, blinded to each others finding. Kappa statistic for concordance between NaF and DWIBS was scored.

Results Patient wise concordance between DWIBS and NaF was seen in 26 (72%) patients. On a lesion- basis, NaF identified more lesions (141) than DWIBS (108). Lesion detection was easier on NaF than DWIBS. Weighted kappa for concordance between NaF and DWIBS was 0.43 (95 % CI=0.14 to 0.72 , SE=0.14 ).

Conclusions We conclude, 18F NaF PET/CT is superior to DWIBS for the detection of skeletal metastases in prostate cancer patients.