Original article Standardized uptake value-based evaluations of solitary pulmonary nodules using F-18 fluorodeoxyglucose-PET/ computed tomography Berna Degirmenci a,d , David Wilson b , Charles M. Laymon a , Carl Becker a , N. Scott Mason a , Badreddine Bencherif a , Anurag Agarwal a , James Luketich c , Rodney Landreneau c and Norbert Avril a Objective Combined positron emission tomography and computed tomography (PET/CT) might improve the accuracy of PET tracer quantification by providing the exact tumour contour from coregistered CT images. We compared various semiquantitative approaches for the characterization of solitary pulmonary nodules (SPNs) using F-18 fluorodeoxyglucose PET/CT. Methods The final diagnosis of 49 SPNs (46 patients) was based on histopathology (n = 33) or patient follow-up (n = 16). The regions of interest (ROIs) were drawn around lesions based on the CT tumour contour and mirrored to the coregistered PET images. Quantification of F-18 fluorodeoxyglucose uptake was accomplished by calculating the standardized uptake value (SUV) using three different methods based on: activity from the maximum-valued pixel within the tumour (SUV-max); the mean ROI activity within the transaxial slice containing the maximum-valued pixel (SUV-mean); and the mean activity over the full tumour volume (SUV-vol). SUVs were corrected for partial volume effects and normalized by body surface area, lean body weight, and blood glucose. Recovery coefficients for partial-volume correction were derived from phantom studies. The ability of various SUVs to differentiate between benign and malignant SPNs was determined by calculating the area under the receiver operating characteristic (ROC) curves. Results Twenty-six SPNs were malignant and 23 were benign. The area under the ROC curve was 0.78 for SUV- mean, 0.83 for SUV-max, and 0.78 for SUV-vol. SUV-max and its normalizations yielded the highest area under the ROC curve (0.83–0.85); SUV-mean-partial volume corrected-lean body weight resulted in the lowest area under the ROC curve (0.76). At a specificity of 80%, SUV- max-body surface area provided the highest sensitivity (81%) and accuracy (80%) to detect malignant SPN. Using SUV-max with a cutoff of 2.4 at a specificity of 80% resulted in a sensitivity of 62% (accuracy 71%). Conclusion Various normalizations applied to SUV-max provided the highest diagnostic accuracy for characterization of SPNs. Quantification methods using the exact tumour contour derived from CT in combined PET/CT imaging (ROI mean activity within a single transaxial slice and mean tumour volume activity) did not result in improved differentiation between benign and malignant SPN. Obtaining SUV-max might be sufficient in the clinical setting. Nucl Med Commun 29:614–622 c 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins. Nuclear Medicine Communications 2008, 29:614–622 Keywords: F-18 fluorodeoxyglucose-PET/computed tomography, solitary pulmonary nodules, standardized uptake value, tracer quantification a Department of Radiology, Divisions of b Pulmonary Medicine, c Thoracic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, USA and d Dokuz Eylul University Medical School, Izmir, Turkey Correspondence to Dr Norbert Avril, MD, Department of Nuclear Medicine, Barts and The London School of Medicine, West Smithfield (QE II), London EC1A 7BE, UK Tel: + 44 20 7601 7144; fax: + 44 20 7601 7149; e-mail: n.e.avril@qmul.ac.uk Received 27 September 2007 Accepted 23 January 2008 Introduction A solitary pulmonary nodule (SPN) is defined as a single spherical lesion of 3 cm or less in diameter completely surrounded by lung parenchyma without any associated atelectasis or lymphadenopathy [1]. The probability of lung cancer increases with tumour size and pulmonary nodules (PNs) larger than 3 cm in diameter are fre- quently malignant [2]. A wide range regarding the incidence of cancer in SPN, varying from 5 to 70% [1,2] is reported in the literature. The occurrence rate of SPNs depends on the patient population studied as well as the geographic location and the prevalence of inflammatory lung disease. Uniform biopsy or resection of all SPNs evident in diagnostic imaging would result in a large number of unnecessary invasive procedures. Although certain radiological features are associated with a benign The present address of Norbert Avril is Department of Nuclear Medicine, Barts and The London School of Medicine, Queen Mary, University of London, London, UK. 0143-3636 c 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.