[The angiogram sign in pulmonary atelectases studied by spiral computed tomography. Its incidence and semeiologic value].

PURPOSE: We investigated the yield of Helical CT in the study of lung vessels, the incidence of the angiogram sign and its actual value.

MATERIAL AND

METHODS

July 1997 to December 1998, we studied 30 cases of pulmonary collapse of different origin. We found 15 cases of passive collapse (10 from pleural effusion, 2 from diaphragmatic compression, 2 from traumatic pneumothorax, and 1 from isthmic aortic aneurysm), 12 cases of obstructive collapse (9 from bronchogenic carcinoma, 1 from mucoid obstruction, 1 from hilar lymphadenopathy, and 1 from mediastinal cancer), 2 cases of adhesive collapse and 1 case of round atelectasis. All the examinations were performed with the Helical technique during nonionic iodinated contrast agent injection (bolus, 300-350 mg/mL); we used an automatic injector set at 2-3 mL/s. We studied the images for the angiogram sign, that is hyperdense bands, usually longer than 2 cm, through the collapsed lung, which correspond to normal pulmonary vascular branches.

RESULTS

The angiogram sign was found in 95% of passive (14/15) and in 80% of obstructive (10/12) collapses. However in 2 of those we also found some hyperdense spots referable to vessels seen on transverse slices. The angiogram sign was missing in 1 of 2 adhesive collapses because of vascular distortion from irradiation-related fibrosis. The "comet-tail" vascular pattern was seen in round atelectasis. We had no cases of cicatricial collapse.

CONCLUSIONS

Thanks to its fast acquisition capabilities, Helical CT well depicts peak vascular enhancement, which permitted identification of the angiogram sign in several pulmonary collapse cases. Thus, this sign becomes even less specific, and just one of the signs of pulmonary consolidation.