Dynamic Contrast Enhancement Patterns of Solitary Pulmonary Nodules on 3D Gradient-Recalled Echo MRI

The purpose of this study was to determine whether contrast enhancement features on 3D volumetric gradient-recalled echoMR images allow differentiation of benign from malignant solitary pulmonary nodules. Forty patients with solitary pulmonary nodules (range of greatest diameter, 7-40 mm) detected on CT underwent unenhanced MRI and contrast-enhanced MRI performed in 10 consecutive dynamic 3D volumetric gradient-recalled echo sequences every 30 seconds. Contrast enhancement patterns (homogeneous, heterogeneous, rim, peripheral, and central) of the lesions were visually evaluated, and time-intensity curves of the lesions were drawn. Twenty patients had benign lesions (nine, tuberculoma; one, aspergilloma; nine, round atelectasis; one, postinflammatory nodule). The other 20 patients had malignant lesions (18, primary lung cancer; two, metastasis). At visual analysis, all 20 malignant lesions displayed peripheral enhancement with progressive heterogeneous fill-in on the late images. All nine tuberculomas and the aspergilloma had rim enhancement, and all nine round atelectasis lesions and the postinflammatory nodule had early intense homogeneous enhancement. Regarding the time-intensity curves, all malignant lesions except one lung cancer lesion had early peak enhancement with rapid washout. All benign lesions displayed early increasing enhancement with an early plateau in the second minute after contrast administration (nine tuberculomas and one aspergilloma) or a late plateau in the fourth minute (nine round atelectasis lesions and one postinflammatory nodule). Rim contrast enhancement is highly valuable in the diagnosis of tuberculoma. Time-intensity curve types can be taken into consideration for noninvasive differentiation of lung cancer, tuberculoma, and round atelectasis.