Transcutaneous contrast enhanced sonography of the chest for evaluation of pleural based pulmonary lesions: experience in 137 patients

Abstract

Transcutaneous ultrasound enables visualization of pleural based lesions but with a poor correlation to specific pathology. Ultrasound contrast agents in conjunction with contrast specific imaging techniques are increasingly accepted in clinical use. Up to date there are no data about the use of contrast enhanced sonography (CES) in a large series of pleural based pulmonary lesions. From August 2004 to August 2005, 137 consecutive patients with pleural based pulmonary lesions on B-mode sonography were studied by CES using a transcapillary second-generation contrast agent (SonoVue(R)). The following CES parameters were retrospectively evaluated. Time to enhancement (TE) of contrast agent after i. v. application was determined and classified as short TE (< = 6 sec) vs. delayed TE (> 6 sec). Extent of enhancement (EE) was evaluated during the arterial phase (2 - 30 sec) and the parenchymal phase (1 - 5 minutes) by using the normal splenic tissue as an in vivo reference, and classified in reduced EE (anechoic/hypoechoic) vs. marked EE (isoechoic/hyperechoic) during both phases. Homogeneity of enhancement (HE) was classified as homogeneous vs. inhomogeneous. 60 patients had histologically confirmed malignant lesions due to central lung cancer (n = 31), and peripheral malignant lesions (n = 29). 77 patients had benign pleural based lesions including pneumonia (n = 32), pulmonary embolism (n = 20), compression atelectasis (17), and other benign pleural based lesions (n = 8). Malignant and benign lesions did not vary significantly regarding TE, EE, and HE. However, there were highly significant differences in the ratio of short vs. delayed TE and reduced vs. marked EE between the six disease groups. Characteristic patterns were short TE with marked EE in all compression atelectasis cases and in 62 % of patients with pneumonia. Delayed TE and reduced EE was seen in all patients with pulmonary embolism and in 62 % of patients with peripheral malignant lesions. Central lung cancer and benign nodules did not present with such specific patterns. No significant differences in HE were seen between subgroups. Pulmonary lesions are characterized by different CES-patterns of arterial supply as evidenced by TE and EE which depends on underlying causes, but CES does not allow to distinguish benign from malignant pleural based lesions in general.