Electron-beam CT is available at only a very few centers across the United States. A major nonemergent application is the detection of coronary artery calcification. The degree of coronary artery calcification bears a strong relationship to the presence of significant coronary artery stenosis. Cardiac anatomy, the relationship between chambers of the heart and great vessels, is readily determined using this modality. Since electron-beam CT can obtain cine images of the heart, cardiac function and focal wall motion abnormalities can be determined. Due to the limited availability of this modality, however, the remaining discussion will focus on non-electron-beam methods.

Although helical CT offers very rapid scanning, it is unable to assess cardiac function, since cine loops of the heart are not obtained. Cardiac anatomy, however, is well assessed. Focal abnormalities of the myocardial wall are indicative of cardiac tumor or thrombus ( Fig... 57-4). Differentiation of these possibilities usually requires cine imaging, so that patients with such masses are referred for echocardiography or MRI.

and left atrium (arrows). (Reprinted from Bluemke and Boxerman,19 with permission.)

CT offers a good depiction of pericardial disease ( Fig 57-5). Simple pericardial effusions show low density relative to the myocardium, and the extent of effusion can be readily quantified, if necessary. The presence of calcifications of the pericardium is an important factor in the diagnosis of constrictive pericarditis and, with the correct symptoms, improves the specificity of this diagnosis. High-density pericardial fluid collections are likely to represent localized hematomas, either from trauma or surgery.

FIG. 57-5. Computed tomographic scan after intravenous contrast administration shows pericardial effusion and enhancement ( arrows) due to pericarditis, with left pleural effusion and left lower lobe atelectasis. (Reprinted from Bluemke and Boxerman,19 with permission.)

Helical CT following intravenous administration of contrast is an excellent modality for assessing diseases of the pulmonary arteries. Pulmonary artery emboli appear as low-attenuation defects in the opacified pulmonary arteries. Helical CT can demonstrate emboli not only in the main pulmonary arteries but also in the third- and fourth-order branches, because of high spatial resolution and cross-sectional imaging of these vessels.

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