Multidetector CT of solitary pulmonary nodules

Abstract

With the increasing use of MDCT, more solitary pulmonary nodules are being detected. Although the majority of these lesions are benign, lung cancer constitutes an important consideration in the differential diagnosis of solitary pulmonary nodules. The goal of management is to correctly differentiate malignant from benign nodules to ensure appropriate treatment. Stratifying patients' risk factors for malignancy, including patient age, smoking history, and history of malignancy, is essential in the management of solitary pulmonary nodules. In terms of radiologic evaluation, obtaining prior films is important to assess for nodule growth. The detection of certain patterns of calcification and stability for 2 years or more have historically been the only useful findings for determining whether a nodule is or is not benign. However, recent technological advances in imaging, including MDCT and PET/CT, have improved nodule characterization and surveillance. For solid nodules, CT enhancement of less than 15 HU and hypometabolism on PET (SUVmax <2.5) favor a benign etiology. Potential pitfalls in nodule enhancement and PET evaluation of solitary pulmonary nodules include infectious and inflammatory conditions. Stratified according to patient risk factors for malignancy and nodule size, recent guidelines for the management of incidentally detected small pulmonary nodules have been useful in decision analysis. An important exception to these guidelines is the evaluation and management of the subsolid nodule. These lesions are not suitable for CT enhancement studies and may show low metabolic activity on PET imaging. Due to their association with bronchioloalveolar carcinoma and adenocarcinoma, subsolid nodules require a more aggressive approach in terms of reassessing serial imaging and/or obtaining tissue diagnosis. As data from the low-dose CT lung cancer screening trials are analyzed and further studies with new imaging techniques are performed, management strategies for the imaging evaluation of the solitary pulmonary nodule will continue to evolve.