MRA is capable of detecting clot in central and up to third-order pulmonary vessels but remains inferior to angiography for visualizing more peripheral emboli. The ultimate place and cost-effectiveness of MRA in the evaluation of thromboembolic disease remains to be established. Pleural effusions present as hypoechoic or nonechoic regions. In one study, ultrasonographic guidance led to positive results in 88 percent of failed blind thoracenteses. Pleural-based masses can be visualized with approximately 95 percent specificity and sensitivity, providing guidance for biopsies.
Consolidation is seen as hypoechoic regions that move with the patient's breathing.
Air bronchograms are hyperechoic, whereas liquid-filled airways associated with atelectasis or endobronchial obstruction are hypoechoic. Abscesses are seen as irregularities in density in an otherwise homogeneous region, and tumors may be distinguished within a consolidated area by their relatively homogeneous consistency and by their regular borders. Specificity and sensitivity of the method do not permit ultrasonography to replace computed tomography or other radiologic methods, but it may be viewed as a complementary technique.