Radiographics : a review publication of the Radiological Society of North America, Inc
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In addition to existing strategies for reducing radiation dose in computed tomographic (CT) examinations, such as the use of automatic exposure control, use of the optimal tube potential also may help improve image quality or reduce radiation dose in pediatric CT examinations. The main benefit of the use of a lower tube potential is that it provides improved contrast enhancement, a characteristic that may compensate for the increase in noise that often occurs at lower tube potentials and that may allow radiation dose to be substantially reduced. ⋯ The power limits of the CT scanner and the desired scanning speed also must be considered. The use of a lower tube potential and the amount by which to reduce radiation dose must be carefully evaluated for each type of examination to achieve an optimal tradeoff between contrast, noise, artifacts, and scanning speed.
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The Fontan procedure refers to any operation that results in the flow of systemic venous blood to the lungs without passing through a ventricle. It is performed to treat several complex congenital heart abnormalities including tricuspid atresia, pulmonary atresia with intact ventricular septum, hypoplastic left heart syndrome, and double-inlet ventricle. ⋯ Complications of Fontan circulation include exercise intolerance, ventricular failure, right atrium dilatation and arrhythmia, systemic and hepatic venous hypertension, portal hypertension, coagulopathy, pulmonary arteriovenous malformation, venovenous shunts, and lymphatic dysfunction (eg, ascites, edema, effusion, protein-losing enteropathy, and plastic bronchitis). Magnetic resonance imaging is best for postoperative evaluation of patients who underwent the Fontan procedure, and cardiac transplantation remains the only definitive treatment for those with failing Fontan circulation.
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Review
MR imaging mapping of skeletal muscle denervation in entrapment and compressive neuropathies.
The diagnoses of entrapment and compressive neuropathies have been based on the findings from clinical examinations and electrophysiologic tests, such as electromyography and nerve conduction studies. The use of magnetic resonance (MR) imaging for the diagnosis of entrapment or compressive neuropathies is increasing because MR imaging is particularly useful for discerning potential causes and for identifying associated muscle denervation. ⋯ The analysis of denervated muscle distributions by using MR imaging, with a knowledge of nerve innervation patterns, would be helpful for determining the nerves involved and the levels of nerve entrapment or compression. In this context, the mapping of skeletal muscle denervation with MR imaging has a supplementary or even a primary role in the diagnosis of entrapment and compressive neuropathies.
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As the largest tarsal bone and the most inferior bone in the body, the calcaneus is responsible for supporting the axial load from the weight of the body. It is most commonly fractured after a fall from a height in which axial loads exceed its support capacity. Calcaneal fractures account for 60% of all tarsal fractures. ⋯ The classification of extraarticular fractures has been less controversial and makes use of anatomic landmarks on the calcaneus to divide the bone into anterior, middle, and posterior areas. Soft-tissue involvement is an important aspect of calcaneal fracture assessment because it has been linked with poor functional outcomes. Familiarity with the normal anatomy of the calcaneus, the classification of calcaneal fractures, and the various complications of these fractures is essential for treatment assessment, especially if surgical intervention is required.