Although most lesions that occur in the chest have a nonspecific soft-tissue appearance, fat-containing lesions are occasionally encountered at cross-sectional computed tomography (CT) or magnetic resonance imaging. The various fat-containing lesions of the chest include parenchymal and endobronchial lesions such as hamartoma, lipoid pneumonia, and lipoma. Endobronchial hamartoma usually appears at CT as a lesion with a smooth edge, focal collections of fat, or fat collections that alternate with foci of calcification. Mediastinal fat-containing lesions include germ cell neoplasms, thymolipomas, lipomas, and liposarcomas. The most frequent CT manifestation of the germ cell neoplasm teratoma is a heterogeneous mass with soft-tissue, fluid, fat, and calcium attenuation. Cardiac lesions with fat content include lipomatous hypertrophy of the interatrial septum and arrhythmogenic right ventricular dysplasia. Diagnosis of the former is made with CT when a smooth, nonenhancing, well-marginated fat-containing lesion is identified in the interatrial septum. Finally, fat may herniate into the chest at several characteristic locations. When such a lesion is identified, the time required for differential diagnosis is significantly reduced, often allowing a definitive radiologic diagnosis. Sagittal and coronal reformatted images can add valuable information by showing diaphragmatic defects and hernia contents.
Multisection computed tomography (CT) was introduced in 1992 with the advent of dual-section-capable scanners and was improved in 1998 following the development of quad-section technology. With a recent increase in gantry speed from one to two revolutions per second, multisection CT scanners are now up to eight times faster than conventional single-section helical CT scanners. The benefits of quad-section CT relative to single-section helical CT are considerable. They include improved temporal resolution, improved spatial resolution in the z axis, increased concentration of intravascular contrast material, decreased image noise, efficient x-ray tube use, and longer anatomic coverage. These factors substantially increase the diagnostic accuracy of the examination. The multisection CT technique has enabled faster and superior evaluation of patients across a wide spectrum of clinical indications. These include isotropic viewing, musculoskeletal applications, use of multiplanar reformation in special situations, CT myelography, long coverage and multiphase studies, CT angiography, cardiac scoring, evaluation of brain perfusion, imaging of large patients, evaluation of acute chest pain or dyspnea, virtual endoscopy, and thin-section scanning with retrospective image fusing. Multisection CT is superior to single-section helical CT for nearly all clinical applications.
Pulmonary manifestations are the hallmark of histoplasmosis. Clinical syndromes range from asymptomatic infection to diffuse alveolar disease causing respiratory difficulty and even death. Serologic tests for antibodies and antigen detection are especially helpful in the diagnosis of histoplasmosis but are frequently overlooked. Detection of Histoplasma capsulatum antigen in bronchoalveolar lavage fluid may be particularly helpful in patients with acute pulmonary histoplasmosis or disseminated disease with pulmonary involvement. Topics of special importance for pulmonary disease specialists include the approach to the exclusion of histoplasmosis in the evaluation of patients with suspected sarcoidosis, differentiation of pulmonary histoplasmosis and malignancy in those with lung masses or mediastinal lymphadenopathy, and recognition and management of chronic pulmonary and mediastinal manifestations of histoplasmosis. Although histoplasmosis is mild and self-limited in most healthy individuals, antifungal therapy is indicated in those with acute diffuse pulmonary infection, chronic pulmonary histoplasmosis, progressive disseminated disease, and perhaps mediastinal adenitis accompanied by obstructive symptoms. Antifungal therapy to prevent reactivation of histoplasmosis during immunosuppressive therapy, or transition of mediastinal adenitis to fibrosing mediastinitis, although controversial, is not recommended. Several new drugs active against H. capsulatum offer alternatives in patients failing or intolerant of current therapies.
Comparison of tumor volumes at serial CT examinations reveals a very wide range of growth rates. Some tumors grow so slowly that biopsy is required to prove they are malignant.
Multi-detector row CT has an accuracy of 91% in the depiction of suspected acute PE when conventional PA is used as the reference standard.
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