Table of Contents:
The purpose of this retrospective study was to investigate the value of transcutaneous contrast-enhanced ultrasound (CEUS) in the diagnosis of pulmonary nodules by describing their CEUS patterns and to determine their biological dignity employing the CEUS parameters.
Between 12/2003 and 03/2007 n = 72 consecutive patients with peripheral lung nodules found on B-mode ultrasound were examined with CEUS. 32 nodules were benign (pneumonic nodules (13), infarcted nodules (6), other benign nodules (7), unclear benign nodules (6)) while 40 lesions were malignant including metastatic nodules (23), primary lung cancer nodules (12) and nodules due to lymphoma (5). Their CEUS patterns were described and subgroups were compared to each other regarding the CEUS criteria. The following CEUS parameters were retrospectively analysed: 1. time to contrast enhancement (TE) of the nodules, 2. extent of contrast enhancement (EE) in the arterial and the parenchymal phase was determined and classified as reduced EE (anechoic, hypoechoic) versus marked EE (isoechoic, hyperechoic), 3. homogeneity of contrast enhancement (HE) was noted and classified as homogeneous versus inhomogeneous. For evaluation of EE and HE the tissue enhancement of the spleen was used as an «in-vivo-reference». Further more the vascularity of the lung nodules was noted and classified as “absence of perfusion” (no contrast enhancement), early pulmonary arterial supply (PA) and delayed bronchial arterial blood supply (BA).
The CEUS examinations were performed at the Department of Ultrasound Diagnostics, Philipps-University Marburg, using an adequate contrast-devoted unit (Acuson Sequoia ® 512 GI, Siemens Medical Solutions USA, Ultrasound Division) that had a contrast-specific, continuous-mode software. A low mechanical index (MI) was used and the pulmonary nodules were observed in real-time for evidence of contrast uptake over a period of 5 minutes by a single physician experienced with contrast-enhanced ultrasound of the lung. Contrast enhancement was achieved with SonoVue ® (Bracco SpA, Milan, Italy), a second-generation ultrasound contrast agent consisting of phospholipid-stabilized microbubbles of sulphur hexafluoride.
It could be demonstrated that CEUS examinations of peripheral lung nodules are feasible and pulmonary lesions of certain pathologies may show a characteristic CEUS pattern regarding time to enhancement (TE), extent of enhancement (EE) and the type of arterial blood supply.
CEUS can be helpful to confirm the diagnosis of pneumonic, infarcted and malignant peripheral nodules (metastatic and primary lung cancer nodules) because these pathologies predominantly show a characteristic CEUS pattern. Benign and malignant lung nodules did not vary significantly regarding TE, EE and HE. There were found significant differences between nodules with pulmonary arterial (PA) supply and lesions with bronchial arterial (BA) blood supply regarding TE, EE and their biological dignity (► p=0,005): “PA” nodules were benign in 60,7%, “BA” nodules were malignant in 76,3% of cases. Pneumonic nodules mainly showed a short time to contrast enhancement (mean: 5,0sec), a marked tissue enhancement (77%), homogeneous distribution of contrast enhancement (77%) and a “PA” blood supply in 100% of cases. Infarcted nodules were avascular in 83% and showed a reduced tissue enhancement in 100% of cases. Malignant nodules predominantly showed a delayed time to contrast enhancement (mean: 11,1sec), reduced tissue enhancement (75%), homogeneous distribution of contrast enhancement (67%) and a “BA” blood supply in 72% of cases. In subgroups no significant differences of “HE” could be found.
The results of this study confirm that CEUS enables to distinguish vascularized from avascular lung tissue and to differentiate an early pulmonary arterial blood supply (PA) from a delayed bronchial arterial blood supply (BA) of peripheral lung nodules. A diagnostic value of CEUS in the assessment of the biological dignity of pulmonary nodules could not be observed because benign and malignant lesions did not vary significantly regarding TE, EE and HE. It could be shown that pulmonary nodules with a “PA” blood supply tended to be benign and often demonstrated a marked tissue enhancement while peripheral nodules with a “BA” blood supply tended to malignancy and mostly showed a reduced tissue enhancement during CEUS. It could be demonstrated that CEUS allows a differentiation of an early “PA” blood supply from a delayed “BA” blood supply of pulmonary nodules. The results of the present investigation are encouraging and elucidate the potential of this modality in the workup of pulmonary nodules located in the peripheral regions of the lungs.