Tehranzadeh J, Kelley M J
Radiology. 1979 Oct;133(1):23-30. doi: 10.1148/133.1.23.
Chest radiographs of 100 patients with suspected pericardial effusion who underwent echocardiography were reviewed. Fifty were echo-positive and 50 were negative. The differential density sign was present in 34 patients (68%) who were echo-positive and 2 patients (4%) who were negative; on frontal (62%) and lateral (41%) projections; and in patients with small, moderate, and large effusions. Computed tomographic findings in 1 patient correlated closely with those obtained radiographically. Experimental models suggest this sign is related to different tissue attenuation coefficients for blood and saline, different tissue thicknesses of the spherically shaped heart, the presence of epicardial fat around the heart, and chest film exposure factors. "Trapping" of the middle lobe or anterior lingula may also contribute. When pericardial effusion is not suspected, the presence of this sign should be an indication for echocardiography.
回顾了100例疑似心包积液并接受超声心动图检查患者的胸部X光片。其中50例超声心动图检查呈阳性，50例呈阴性。差异密度征在50例超声心动图检查呈阳性的患者中出现34例（68%），在50例阴性患者中出现2例（4%）；在正位（62%）和侧位（41%）投照中均有出现；在少量、中等量和大量积液的患者中也有出现。1例患者的计算机断层扫描结果与X光片结果密切相关。实验模型表明，该征象与血液和盐水不同的组织衰减系数、球形心脏不同的组织厚度、心脏周围的心外膜脂肪的存在以及胸部X光片的曝光因素有关。中叶或舌叶的“被困”也可能起作用。当不怀疑有心包积液时，该征象的出现应提示进行超声心动图检查。
