Lung nodule detection and characterization with multislice CT

Pulmonary nodules remain a diagnostic dilemma. Nodules are frequently incidentally detected in patients undergoing chest radiography for unrelated symptoms. Not infrequently, patients undergoing diagnostic chest CT for nodules identified on radiograph are found to have more nodules of smaller size [1 -3]. A pulmonary nodule is generally defined as a rounded opacity, at least moderately well marginated and no greater than 3 cm in maximum diameter [4]. The most common causes for nodules detected by chest radiograph are gramilomatous disease and lung cancer [5]. Other etiologies include solitary pulmonary metastases, hamartomas, and carcinoid tumors [6,7]. Approximately 30% to 40% of solitary pulmonary nodules identified by chest radiography are malignant [6,7]. The likelihood of a nodule representing malignancy is dependent on the overall relative prevalence of disease. Patients with nodules in endemic areas with fungi have a lower likelihood that a nodule represents cancer. CT plays a major role in the detection and further characterization of pulmonary nodules. On CT, as also true for chest radiography [8], attempts to differentiate nodules as benign versus malignant have relied on classifications focused on attenuation, enhancement characteristics, morphology, and size. The ability to obtain high-resolution imaging is vital for maximizing the ability to characterize pulmonary nodules and manage them with subsequent assessment of growth. Recently, multislice CT (MSCT) technology has facilitated nodule evaluation by enabling one to obtain contiguous thin sections on the order of 0.5 to 1 mm while minimizing respiratory and cardiac motion artifact.