Purpose: The purpose of the present study was to evaluate whether 2-fluoro[fluorine-18]-2-deoxy-D: -glucose (F-18 FDG) positron emission tomography (PET) could differentiate malignant and benign bone lesions and whether obtaining delayed F-18 FDG PET images could improve the accuracy of the technique.
Methods: In a prospective study, 67 patients with bone lesions detected by computed tomography (CT) or magnetic resonance imaging were included. Whole body PET/CT imaging was performed at 1 h (early) after the F-18 FDG injection and delayed imaging at 2 h post injection was performed only in the abnormal region. Semiquantitative analysis was performed using maximum standardized uptake value (SUV(max)), obtained from early and delayed images (SUV(maxE) and SUV(maxD), respectively). The retention index (RI) was calculated according to the equation: RI = (SUV(maxD) - SUV(maxE)) x 100/SUV(maxE.) Histopathology of surgical specimens and follow-up data were used as reference criteria. The SUV(maxE) and RI were compared between benign and malignant lesions.
Results: The final diagnoses revealed 53 malignant bone lesions in 37 patients and 45 benign lesions in 30 patients. There were statistically significant differences in the SUV(maxE) between the malignant and benign lesions (P = 0.03). The mean SUV(maxE) was 6.8 +/- 4.7 for malignant lesions and 4.5 +/- 3.3 for benign lesions. However, a considerable overlap in the SUV(maxE) was observed between some benign and malignant tumors. With a cutoff value of 2.5 for the SUV(maxE), the sensitivity, specificity, and accuracy were 96.0%, 44.0%, and 72.4%, respectively. The positive predictive value (PPV) and negative predictive value (NPV) were 67.1% and 90.9%, respectively. There were significant differences in the RI between the malignant and benign lesions (P = 0.004). But there was overlap between the two groups. The mean RI was 7 +/- 11 for the benign lesions and 18 +/- 11 for the malignant lesions. When an RI of 10 was used as the cutoff point, the sensitivity, specificity, and accuracy were 90.6%, 76.0%, and 83.7.0%, respectively. The PPV and NPV were 81.4% and 87.1%, respectively.
Conclusions: The results of this study indicate that dual-time point F-18 FDG PET may provide more help in the differentiation of malignant tumors from benign ones.