Interobserver variability among measurements of the maximum and mean standardized uptake values on ¹⁸F-FDG PET/CT and measurements of tumor size on diagnostic CT in patients with pulmonary tumors

Abstract

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 SUV_max and SUV_mean 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 SUV_max and SUV_mean of the ¹⁸F-FDG PET images, and the unidimensional nodule size of the diagnostic CT scans (UD_CT) 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 SUV_max and SUV_mean was also analyzed.

Results: There was 100% agreement in the SUV_max measurements among the 4 readers in the 43 pulmonary tumors. The ICCs for the SUV_max, SUV_mean, and UD_CT by the four readers were 1.00, 0.97, and 0.97, respectively. The root-mean-square values of the COVs for the SUV_max, SUV_mean, and UD_CT by the four readers were 0%, 13.56%, and 11.03%, respectively. There was a high correlation observed between the SUV_max and SUV_mean (Pearson's r=0.958; P <0.01).

Conclusion: This study has shown that the SUV_max of lung nodules can be calculated without any interobserver variation. These findings indicate that SUV_max is a more valuable parameter than the SUV_mean or UD_CT for the evaluation of therapeutic effects of chemotherapy or radiation therapy on serial studies.

Key words::

• ¹⁸F-fluorodeoxyglucose
• standardized uptake value
• computed tomography
• lung nodules

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.