Lobar collapse: basic concepts.

Lobar collapse is important to diagnose when present, as it may indicate the presence of a central bronchial obstructing lesion. In some instances, its appearance is rather classical and easily diagnosed. In other instances, its appearance can challenge even the most experienced radiologist. In yet other instances, it may be simulated by other disease processes. This material represents a discussion of some basic concepts and signs the author considers important in determining whether or not lobar collapse is present.

Normal and abnormal vascular structures that simulate neoplasms on chest radiographs: clues to the diagnosis.

Despite increased use of and reliance on cross-sectional imaging techniques in the thorax, conventional chest radiography remains the most commonly performed imaging examination. However, conventional radiographic appearances of normal and abnormal vascular structures can be misinterpreted as representing neoplasms or soft-tissue masses and lead to inappropriate diagnostic procedures. Vascular structures that can simulate neoplasms include normal structures such as the subclavian artery and left brachiocephalic, azygos, and pulmonary veins and abnormal structures such as congenital and acquired anomalies of the thoracic aorta and its branches, pulmonary arteries and veins, superior and inferior venae cavae, and azygos and hemiazygos veins. Other entities such as postoperative changes, massive pulmonary embolism, false ventricular aneurysm, and esophageal varices can also be misinterpreted. Important radiographic features that help distinguish these vascular structures from true neoplasms include proximity to known vascular structures, smooth margination, mural calcification, round or oval configuration, poor or nonvisualization in one of two orthogonal views, and absence or altered position of normal vascular structures. Knowledge of patient history and a detailed understanding of normal mediastinal anatomic structures and common variants help in making the correct diagnosis. Familiarity with these entities will result in the proper, most cost-efficient evaluation.

Magnetic resonance imaging confirmation of pulmonary artery aneurysm in Behçet's disease.

Behçet's disease (BD) is a multisystem disorder thought to be the result of an autoimmune vasculitis. Patients classically present with the clinical triad of recurrent oral and genital ulcers and relapsing uveitis. Complications have been reported following pulmonary angiography to diagnose associated pulmonary artery aneurysms. We report a case of pulmonary artery aneurysm in BD confirmed by magnetic resonance (MR) imaging.

Conventional chest radiographs: anatomic understanding of newer observations.

Despite the advances in medical imaging modalities over the past several years, conventional chest radiography still remains the most commonly performed imaging examination. In this report, the author discusses four radiographic observations, all visible on the conventional chest radiograph, and the anatomic basis for each: (a) the normal apical opacity, produced by the subclavian artery and easily confused with parenchymal abnormality; (b) vascular reorientation with upper lobe volume loss, a characteristic divergent or parallel pattern helpful in recognizing upper lobe volume loss; (c) extrapleural fat, which simulates pleural plaques along the lateral chest walls and pleural thickening at the chest apices; and (d) mobility of the mediastinum, which contributes to incorrect mediastinal mass localization and creates soft-tissue bands in the retrosternal area.

The left paratracheal reflection.

The left paratracheal reflection, which is found medial to the left subclavian artery reflection, was sought in 302 normal posteroanterior (PA) chest radiographs, 93 conventional chest tomograms, and 113 thoracic computed tomographic (CT) scans. The left paratracheal reflection was visible on 31% of normal PA chest radiographs. Conventional tomography and CT showed that this finding is produced by contact of the lung with the mediastinum anterior to the left subclavian artery. The CT scans studied showed that the left paratracheal reflection actually represents contact of the lung with left paratracheal mediastinal fat 94% of the time, with the proximal 1-2 cm of the lateral wall of the left common carotid artery 5% of the time, and with the left tracheal wall 1% of the time. A variety of entities may alter the left paratracheal reflection.

Diagnosis of anemia on computed tomography scans of the thorax.

Scans of 14 patients with hemoglobin levels of 7.6 to 10.2 grams/deciliter (gm/dL) were positive for the diagnosis of anemia. All demonstrated the interventricular septum and ascending and descending aortic walls. Scans of 23 patients with hemoglobin levels of 10.5 to 12.8 gm/dL were positive for the diagnosis of anemia in 11 and negative in 12. The ascending and descending aortic walls were seen 39% and 48% of the time, respectively. Scans of 13 patients with hemoglobin levels of 12.9 to 16.0 gm/dL were negative for the diagnosis of anemia.

Upper lobe volume loss: divergent and parallel patterns of vascular reorientation.

The authors present what they believe to be a previously unreported sign of marked upper lobe volume loss. Recognition of the finding may be helpful when other signs of volume loss are equivocal or absent.

Lung torsion: case report and literature review.

A 65-year-old woman with endobronchial carcinoma had torsion of the left upper lobe. A posteroanterior chest radiograph showed apparent atelectasis in the left upper lobe, but the lateral view disclosed an inappropriate posterior displacement of the collapsed lobe. The vasculature of the affected area showed an unusual curvature. Review of 21 examples of lung torsion disclosed no characteristic age, sex, or affected lobe. The most common associations were with previous surgery (n = 10) or a history of trauma (n = 5). The most common radiographic findings are opacification of the affected lobe (n = 12), an abnormal vascular pattern (n = 6), and an abnormal location for the atelectatic lung (n = 5). Affected lobes often show hemorrhagic infarction or necrosis.