Background:
18F-fluoro-2-deoxyglucose positron emission tomography (18F-FDG PET) imaging has been shown to be an accurate method for diagnosing pulmonary lesions, and the standardized uptake value (SUV) has been shown to be useful in differentiating benign from malignant lesions.
Purpose: To survey the interobserver variability of SUVmax and SUVmean measurements on 18F-FDG PET/CT scans and compare them with tumor size measurements on diagnostic CT scans in the same group of patients with focal pulmonary lesions.
Material and Methods: Forty-three pulmonary nodules were measured on both 18F-FDG PET/CT and diagnostic chest CT examinations. Four independent readers measured the SUVmax and SUVmean of the 18F-FDG PET images, and the unidimensional nodule size of the diagnostic CT scans (UDCT) in all nodules. The region of interest (ROI) for the SUV measurements was drawn manually around each tumor on all consecutive slices that contained the nodule. The interobserver reliability and variability, represented by the intraclass correlation coefficient (ICC) and coefficient of variation (COV), respectively, were compared among the three parameters. The correlation between the SUVmax and SUVmean was also analyzed.
Results: There was 100% agreement in the SUVmax measurements among the 4 readers in the 43 pulmonary tumors. The ICCs for the SUVmax, SUVmean, and UDCT by the four readers were 1.00, 0.97, and 0.97, respectively. The root-mean-square values of the COVs for the SUVmax, SUVmean, and UDCT by the four readers were 0%, 13.56%, and 11.03%, respectively. There was a high correlation observed between the SUVmax and SUVmean (Pearson's r=0.958; P <0.01).
Conclusion: This study has shown that the SUVmax of lung nodules can be calculated without any interobserver variation. These findings indicate that SUVmax is a more valuable parameter than the SUVmean or UDCT for the evaluation of therapeutic effects of chemotherapy or radiation therapy on serial studies.
