Radiographics : a review publication of the Radiological Society of North America, Inc
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Vestibular schwannomas account for 85% of cerebellopontine angle tumors in adults and most commonly arise from the inferior division of the vestibular nerve. Surgical and imaging techniques have evolved to offer earlier detection and the potential for hearing preservation. Three main surgical techniques are currently being used for the removal of vestibular schwannomas: middle cranial fossa, suboccipital, and translabyrinthine approaches. ⋯ For example, the middle cranial fossa and suboccipital approaches make hearing preservation possible in selected patients, whereas the translabyrinthine approach precludes hearing preservation because it involves a labyrinthectomy. Imaging plays a key role in preoperative assessment and postoperative management in affected patients. A good understanding of the main surgical approaches, relevant anatomic considerations, surgical complications, and likelihood of tumor recurrence is essential for interpreting magnetic resonance images to the advantage of both the surgeon and the patient, particularly when hearing preservation is a consideration.
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Pancreatic cystic lesions are relatively common imaging findings and may be secondary to both benign and malignant disease processes. Accurate characterization of the internal features of a cyst--including fluid, hemorrhage, septa, and enhancing soft-tissue components--is important to guide the differential diagnosis, and cross-sectional magnetic resonance (MR) imaging is the optimal modality for depicting these features. ⋯ Primary cystic lesions are more common than solid neoplasms with cystic changes. Knowledge of the varied MR imaging appearances of pancreatic cystic lesions may help radiologists achieve greater specificity in diagnostic reporting.
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The most important advantage of 3.0-T magnetic resonance (MR) imaging systems is their increased signal-to-noise ratio (SNR) compared with 1.5-T systems. The higher SNR can be used to shorten acquisition time, achieve higher spatial resolution, or a combination of the two, thereby improving image quality and clinical diagnosis. In fact, 3.0-T MR imaging systems have already proved superior to 1.5-T systems in neuroradiologic and musculoskeletal applications. ⋯ Admittedly, 3.0-T abdominal imaging has important technical limitations, such as standing wave artifact, chemical shift artifact, susceptibility artifact, and safety issues such as increased energy deposition within the patient's body. Furthermore, 3.0-T abdominal MR imaging is still in the early stages of development and requires substantial modifications of the pulse sequences and hardware components used for 1.5-T imaging. Nevertheless, the ability to obtain physiologic and functional information within reasonably short acquisition times with 3.0-T abdominal MR imaging bodies well for the future of this imaging technique.
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The objective of this article is to review the current knowledge about nephrogenic systemic fibrosis (NSF) and how to prevent it. More than 300 cases of NSF in patients with severe chronic renal insufficiency or acute renal failure or in patients undergoing dialysis have been reported in the peer-reviewed literature, with an overwhelming majority occurring within weeks to months after injection of a gadolinium-based contrast agent (GBCA). Because administration of a high dose of a GBCA is a primary risk factor and because most high-dose magnetic resonance (MR) imaging applications involve abdominal imaging (eg, liver and abdominal MR angiography), NSF cases have been associated with abdominal MR imaging. ⋯ Recent recommendations to use GBCAs with caution in patients with acute renal failure, patients receiving dialysis, or patients with an estimated glomerular filtration rate of less than 30 mL/min have resulted in virtually no new NSF cases being reported with onset in 2008 or 2009 in spite of a high level of awareness about this entity. In conclusion, NSF has been virtually eliminated by using caution in administering GBCAs to patients known to have severe or acute renal failure. In these patients, avoid high doses; and for patients undergoing dialysis, schedule MR imaging to occur just before a dialysis session to ensure rapid elimination of gadolinium.
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Positron emission tomography (PET) with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) is increasingly being used in the evaluation of pediatric oncology patients. However, the normal distribution of (18)F FDG uptake in children is unique and may differ from that in adults. A number of physiologic variants are commonly encountered, including normal physiologic uptake in the head and neck, heart, breast, thymus, liver, spleen, gastrointestinal tract, genital system, urinary collecting system, bone marrow, muscles, and brown adipose tissue. ⋯ In addition, the use of combined PET/computed tomographic (CT) scanners is associated with pitfalls and artifacts such as attenuation correction and misregistration. Proper interpretation of pediatric (18)F FDG PET/CT studies requires knowledge of the normal distribution of (18)F FDG uptake in children, as well as of the aforementioned physiologic variants, benign lesions, and PET/CT-related artifacts. Knowing these potential causes of misinterpretation can increase accuracy in PET image interpretation, decrease the number of unnecessary follow-up studies or procedures, and improve patient treatment.