AJR. American journal of roentgenology
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Physiologic changes during pregnancy affect nearly every organ system. In the thorax, the diaphragm elevates as much as 4 cm because of displacement of the abdominal organs by the gravid uterus, resulting in lower lung volumes. Maternal blood volume and cardiac output increase approximately 45% by mid-pregnancy. ⋯ Pregnant patients are also prone to a number of pulmonary insults, including infection, aspiration, and neoplastic disease. These abnormalities have several radiographic patterns: cardiogenic and noncardiogenic pulmonary edema, focal pulmonary abnormalities, and extraalveolar air. Radiologists must recognize not only the normal chest radiographic appearance in these patients but also the thoracic complications associated with pregnancy.
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AJR Am J Roentgenol · Oct 1993
Cause of regional ventilation-perfusion mismatching in patients with idiopathic pulmonary fibrosis: a combined CT and scintigraphic study.
Regional ventilation and perfusion were studied in patients with idiopathic pulmonary fibrosis (cryptogenic fibrosing alveolitis) to seek an explanation for the mismatched ventilation/perfusion (V/Q) seen on scintigrams, which may suggest pulmonary embolic disease. ⋯ The cystic air spaces that are often seen on CT scans of patients with idiopathic pulmonary fibrosis are unperfused (probably due to vascular obliteration) but are usually normally ventilated. This V/Q mismatch on scintigrams explains the large physiologic dead space seen at rest and on exercise and could suggest pulmonary embolism unless a CT scan is obtained. Conversely, the larger cystic spaces might be mistaken for emphysema unless V/Q scintigraphy is done.
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AJR Am J Roentgenol · Oct 1993
Differences in CT density between dependent and nondependent portions of the lung: influence of lung volume.
Lung tissue, blood, and air determine the physical density of the lung and hence the attenuation measured on CT scans. These components are not homogeneously distributed throughout the lungs, and their relative proportion changes continuously during respiration. The objective of this study was to measure densities in various areas of the normal lung with CT and to examine the influences of gravity and of the degree of lung inflation on these densities. ⋯ Changes in lung volume have different effects on changes in lung density in dependent and nondependent parts of the lung. The largest changes in lung density occur in the dependent regions. The difference in density between dependent and nondependent lung regions is smallest for lung volumes near total lung capacity. These findings may be useful as a baseline for interpreting CT measurements of regional lung density in suspected cases of lung disease, which would alter the physical density of lung tissue. Our results also suggest that measurements near total lung capacity should be included.
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AJR Am J Roentgenol · Sep 1993
Calcaneus as a site for assessment of bone mineral density: evaluation in cadavers and healthy volunteers.
The value of calcaneal dual-energy X-ray absorptiometry for monitoring changes in bone mineral density has not yet been established. Accordingly, the focus of this study was to determine the usefulness of the calcaneus as the site for bone mineral density measurement with dual-energy X-ray absorptiometry. ⋯ Taken together, these results suggest that the calcaneus can be used as an additional site for determining bone mineral density to assess osteopenia in patients when deformities of the spine make quantitative CT or other methods of density measurement impossible.
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AJR Am J Roentgenol · Sep 1993
High-dose chloral hydrate sedation for children undergoing MR imaging: safety and efficacy in relation to age.
Sedation is frequently essential for successful MR imaging, and chloral hydrate is the most commonly used drug for this purpose in infants and children. Our experience with these patients suggested that this sedative is less effective in older children, even when administered in high doses. However, no prospective study comparing the efficacy of chloral hydrate sedation for children of different ages undergoing MR imaging has been reported. Accordingly, we performed a study to evaluate the effectiveness and safety of chloral hydrate sedation in children of various ages. ⋯ The higher failure rate for chloral hydrate sedation in children more than 48 months old suggests that the patient's age is an important limitation to the usefulness of chloral hydrate sedation for children undergoing MR imaging. However, the low rate of adverse reactions makes chloral hydrate a safe drug for sedation of children undergoing MR imaging.