Purpose: The aim of our prospective study was to compare the diagnostic accuracy of early, delayed and dual-time-point positron emission tomography (PET) acquisition with contrast enhanced computed tomography (CT) within a PET-CT examination in the evaluation of pulmonary solitary nodules (SPNs).
Materials and methods: Thirty patients were enrolled in the study. All the patients underwent a dual-time-point PET-CT examination. Whole-body PET images were acquired at 50 min after fluorine18-fluorodeoxyglucose ((18)F-FDG) administration (early), followed by a chest acquisition (delayed). Lung nodules with maximum standardised uptake value SUVmax > or =2.5 were considered malignant. SUVmax was calculated on early and delayed images; SUV increasing > or =10% (Delta SUVmax) was considered suggestive of malignancy. Absence of significant lung nodule enhancement (<15 Delta HU) at CT was considered strongly predictive of benignity. For the CT morphological assessment, the irregularity of the shape of each lesion was rated. PET-CT results were related to histological assays and clinical records. Diagnostic accuracy was assessed by area under the receiveroperarting characteristic (ROC) curves analysis.
Results: Early and delayed SUVmax of malignant nodules were significantly higher than those of benign disease. Early SUVmax sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were 77%, 91%, 79.5% and 66.7%; delayed SUVmax corresponding values were 77%, 66%, 74% and 66%; dual-time-point SUVmax values were 83%, 67%, 75% and 74%; DeltaHU values were 94%, 34%, 67%, 96%; CT morphologic evaluation values were 61%, 46%, 60%, 47%. Area under the curve (AUC) for early SUVmax was 0.79, for delayed SUVmax 0.80, for dual-time-point SUVmax 0.85, for DeltaHU 0.63 and for CT morphologic assessment 0.58.
Conclusions: In our small series of patients, early and delayed SUVmax showed comparable accuracies, whereas morphological and contrast enhanced CT evaluations showed the lowest accuracies. Dual-time-point SUVmax showed the largest AUC. However, dual-time-point SUVmax was most sensitive, whereas single-time-point SUVmax was most specific.