Differential Diagnosis of Pulmonary Nodules - Efficacy of Two-Phase Enhanced Spiral CT

Abstract

To evaluate the efficacy of two-phase enhanced spiral CT in differentiating between benign and malignant pulmonary nodules, 31 patients with pulmonary nodules with less than 5 cm in diameter underwent spiral CT at unenhanced, early, and late enhanced phases. Enhanced scans were carried out 30(early phase) and 70-180 sec (late phase) after intravenous injection of mixed solution of 100 mL 60% iodinated contrast media and 60 mL normal saline in a rate of 2.5 mL/sec. The pattern, measured degree of enhancement, and nodule-to-muscle enhancement ratio were compared between 17 benign (mean size: 2.8 cm, 15 tuberculomas included) and 14 malignant nodules (mean size: 3.6㎝). The degree of enhancement of nodules was higher in the late enhanced phase than in the early phase. The measured degree of enhancement was significantly greater in malignant nodules in the early (mean±SD: 13.0±10.9 HU) and late (19.0±9.7 HU) enhanced phases than in benign nodules (early: 3.4±4.2HU, late: 7.2±9.6 HU) (p<0.01 by Wilcoxon rank-sum test). Nodule-to-musde enhancement ratio was greater in malignant (2.1±1.2) than in benign nodules (0.5±0.7) in the late enhanced phase (p<0.01). The enhancing pattern of nodules was more efficiently evaluated with the late enhanced images. Most (70%) of the benign nodules showed no enhancement (23%) or thin rim enhancement in the peripheral region (47%). Malignant nodules were enhanced in homogeneous (57%), mosaic (29%), or peripheral pattern with thick enhancing rim (14%). Two-phase enhanced spiral CT is efficient in evaluation of the pattern and the degree of enhancement of pulmonary nodules and useful for noninvasive differential diagnosis.