The Role of PET-CT in Evaluation of Solitary Pulmonary Nodules

Introduction: The solitary pulmonary nodule (SPN) may be an early sign of lung cancer. Due to the difficulties of radiological imaging techniques in differentiation of benign/malignant nodules, functional imaging techniques like PET-CT are required in patients diagnosed with SPN. The aim of this study was the evaluation of the role of PET-CT in differentiation of malignant/benign SPN by some characteristic findings in PET-CT. Moreover, among the nodules with histopathologically diagnosed as benign, malignant or metastatic, the SUVmax and Hounsfield Units (HU) of PET-CT imaging were also aimed to be compared to assess the role of PET-CT in discrimination of malignant/ benign SPN. Material and Method: Among the patients evaluated with PET-CT with the pre-diagnosis of pulmonary nodule or non-pulmonary malignancies, between July 2010 and January 2012, in Konya University Meram Medical School Nuclear Medicine Department, 241 patients (167 male, 74 female) diagnosed with pulmonary nodule were enrolled in the study. In visual evaluation of PET-CT of all patients, there was only one nodule in lung parenchyma. The diameter in cm, location as central or peripheral, regularity of borders, presence of calcification and HU and Maximum standardized uptake values (SUVmax) values with quantitative analysis of all nodules was recorded. The histopathological evaluation of nodules was available in 91 of those 241 patients and they were also recorded. Results: In comparison of mean SUVmax values in regards to the characteristic findings of nodules in PET-CT, the mean SUVmax value of patients was statistically significantly higher in patients with the nodule diameter ≥ 1cm, centrally located nodules, or nodules with irregular borders. Conclusion: In malignant/benign differentiation of solitary pulmonary nodules with the diameter of higher than 1 cm, PET-CT plays an essential role; however, for the nodules smaller than 1 cm in diameter, in small, single metastatic nodules and some benign nodules with high SUVmax values, PET-CT may be unsatisfactory. However, it is clear that, in especially undetermined nodules, PET-CT is an important complementary tool in diagnosis.