~(18)F-FDG PET/CT in diagnosis of skeletal metastases

This work is to evaluate correlated lesions in PET and CT images of patients suffering skeletal metastases so as to improve efficacy of 18F-FDG PET/CT in diagnosing bone metastases. PET and CT images of 25 patients with malignant tumor suspected bone metastases were reviewed independently by three experts. A region of interest was placed over each lesion, and the standardized uptake value (SUV) was calculated at the maximal single pixel value. The t and χ2 tests were used for statistical analysis. Of the 203 lesions detected on the PET and CT images, 189 were malignant and 14 were benign lesions. PET alone identified 159 malignant lesions and 6 benign lesions, CT alone identified 152 malignant lesions and 11 benign lesions. For PET, the diagnostic sensitivity, specificity and accuracy were 84.1%, 71.4% and 83.3%, respectively, while 80.4%, 71.4% and 83.3% for CT. No significant difference was found between PET and CT in detecting bone metastases (χ2=0.89, 0.19, 0.59, P0.05). Statistical difference of positive ratio of PET was found between osteoblastic and osteolytic or mixed lesions (χ2=47.33, 7.93, both P0.05). Of the 122 positive lesions on both CT and PET scan, the mean SUV was 5.76±3.41, 8.52±5.37 and 7.78±4.96 in osteoblastic lesions, osteolytic lesions and mixed lesions, respectively. Significant difference was found between osteoblast lesions and osteolytic lesions (t=2.28, P0.05). PET images alone may leave out half of osteoblastic letions, but combined analysis of PET and CT images gives better diagnosis.