![]() ![]() This is generally relevant only in interpretation of a posteroanterior (PA) or anteroposterior (AP) projection and not of the lateral projection. The major difference between male and female chest x-rays is caused by differences in the amount of breast tissue. Even with digital or computed radiography, nothing can be done to an underexposed image to improve the image. Underexposure also makes it impossible to see the detail of the mediastinal, retrocardiac, or spinal anatomy (see Fig. It will make the small pulmonary blood vessels appear prominent and may lead to thinking that there are generalized infiltrates when none are really present. This is a major problem for adequate interpretation. Underexposure causes the image to be quite white. (B) Underexposure accentuates the pulmonary vascularity, but you cannot see behind the heart or behind the hemidiaphragms. (A) Overexposure makes it easy to see behind the heart and the regions of the clavicles and thoracic spine, but the pulmonary vessels peripherally are impossible to see. If the image was obtained by using either digital or computed radiography, the image can be “windowed” lower on the computer, resulting in an interpretable image. Under these circumstances, the thoracic spine, mediastinal structures, retrocardiac areas, and nasogastric and endotracheal tubes are well seen, but small nodules and the fine structures in the lung cannot be seen ( Fig. Overexposure causes the image to be dark. A correctly exposed image should allow visualization of vessels to at least the peripheral one-third of the lung and, at the same time, allow visualization of the paraspinous margins and the left hemidiaphragm behind the heart. The range stretches from small vessels in air-filled lungs to dense bony structures located behind the heart. ![]() Making a properly exposed chest x-ray is much more difficult than making x-rays of other parts of the body because the chest contains tissues with a great range of contrast. ![]()
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