Eur Radiol (2007) 17: 467–473 DOI 10.1007/s00330-006-0362-7 CHEST W. De Wever L. Meylaerts L. De Ceuninck S. Stroobants J. A. Verschakelen Received: 15 March 2006 Revised: 12 May 2006 Accepted: 12 June 2006 Published online: 3 October 2006 # Springer-Verlag 2006 Additional value of integrated PET-CT in the detection and characterization of lung metastases: correlation with CT alone and PET alone Abstract The purpose was evaluat- ing retrospectively the additional value of integrated positron emission tomography (PET) and computed tomography (CT) in the detection of pulmonary metastases in comparison with CT and PET alone. Fifty-six lung nodules, divided into three groups according their size, detected in 24 consecutive patients with a known primary tumor were retrospectively evaluated with integrated PET-CT, CT and PET. The nature of these nodules was determined by either histopathol- ogy or a follow-up of at least 6 months. The CT and PET images of the integrated PET-CT were evaluated separately by a radiologist and a nuclear medicine physician, the inte- grated PET-CT images were evaluated by a chest radiologist and nuclear medicine physician in consensus. The investigators were asked to search lung nodules and to determine whether these nodules were metasta- ses or not. Sensitivity and accuracy for CT, PET and integrated PET-CT for characterization of all pulmonary nodules were, respectively: 100%, 90%, 100% and 57%, 55%, 55%. There was no significant difference in the characterization of pulmonary nodules between integrated PET-CT and CT alone (P=1.000) and PET alone (P=0.1306). An accurate evaluation is only possible for lesions larger than 1 cm. Keywords Integrated PET-CT . Pulmonary metastases . Detection . Characterization Introduction Surgical resection has become a well-established technique for treatment of pulmonary metastases in certain circum- stances. Complete resection of all metastatic disease is critical to achieve long-term survival. Precise preoperative diagnosis of the extent of pulmonary metastasis is necessary for correct patient selection and to avoid un- necessary interventions [1, 2]. For detection of pulmonary nodules, helical computed tomography (CT) is the preferred imaging modality [3, 4]. Recent advantages in positron emission tomography (PET) with 2-deoxy-2fluoro-(F-18)-D-glucose (FDG) has made a significant contribution to differentiate between benign and malignant nodules. Several reports have suggested that PET examinations reduce the number of patients with indeter- minate nodules undergoing unnecessary surgical biopsy [5, 6]. FDG-PET has proved to be accurate for the differen- tiation of pulmonary nodules as small as 1 cm in diameter; however, FDG-PET is neither specific nor sensitive in the characterization of pulmonary nodules smaller than 1 cm and metastases from low-grade malignant tumors, such as bronchiolo-alveolar carcinoma and carcinoid, which are frequently negative on FDG-PET due to their low glucose metabolism. Otherwise, active inflammation can show hotspots due to their high glucose metabolism [5, 7–11]. The diagnostic accuracy of FDG-PET depends on the size of the lesion and the intensity of FDG accumulation. W. De Wever (*) . L. Meylaerts . J. A. Verschakelen Department of Radiology, University Hospitals Gasthuisberg, Herestraat 49, 3000 Leuven, Belgium e-mail: walter.dewever@uz.kuleuven.ac.be Tel.: +32-16-343782 Fax: +32-16-343765 L. De Ceuninck . S. Stroobants Department of Nuclear Medicine, University Hospitals Gasthuisberg, Herestraat 49, 3000 Leuven, Belgium