Journal of magnetic resonance imaging : JMRI
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Contrast agents have greatly expanded the role of MR imaging (MRI) to allow assessment of physiologic, or "functional," parameters. Although activation mapping generally does not require contrast agents, other forms of functional MRI, including mapping of cerebral hemodynamics (eg, perfusion imaging), are best done with the use of contrast agents. Serial echo planar images are obtained after bolus injection of lanthanide chelates. ⋯ Functional MRI perfusion imaging of intraaxial tumors is analogous to positron emission tomography for delineation of metabolic activity, yet may be even more sensitive to neovascularity and possesses improved image quality. Clinical applications include biopsy site selection and postirradiation follow-up. Further improvements in data analysis and map generation techniques may improve diagnostic accuracy and utility.
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J Magn Reson Imaging · Jan 1997
ReviewEffects of contrast dose, delayed imaging, and magnetization transfer saturation on gadolinium-enhanced MR imaging of brain lesions.
This paper discusses the types of paramagnetic agents available for clinical brain imaging and reviews investigations that have sought to optimize the use of these agents by varying the administered dose, delaying the imaging time after contrast administration, and altering image contrast by using magnetization transfer saturation pulses.
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J Magn Reson Imaging · Jan 1997
ReviewContrast-enhanced MR imaging in the evaluation of treatment response and prediction of outcome in multiple sclerosis.
MR imaging is becoming increasingly important in the evaluation of multiple sclerosis based on its sensitivity to acute, often subclinical events in the brain and because it provides a basis for measuring the accumulation of disease over time. Contrast-enhanced MR imaging in particular evaluates disease at the fundamental level of events affecting the blood-brain barrier. This review emphasizes (a) recent developments in the use of contrast-enhanced MR imaging as a measure of disease in patient groups and individuals and (b) its emerging role in evaluating new therapies.
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The objective of this study was to demonstrate the appearance of ampullary carcinoma using current MR techniques, including fat suppression, gadolinium enhancement, and MR cholangiography. Nine patients with ampullary carcinoma were examined by MRI at 1.5 T. MR examinations included T1-weighted spoiled gradient echo, T1-weighted fat-suppressed, and immediate postgadolinium spoiled gradient echo images for all patients and MR cholangiography for three patients. ⋯ MR cholangiography demonstrated high grade obstruction of the common bile duct and mild dilatation of the pancreatic duct at the level of the ampulla with abrupt termination of the ducts in two untreated patients and moderate dilatation of the common bile duct in one patient who had a biliary stent. Ampullary carcinomas can be demonstrated on MR images as small masses arising at the ampulla. Tumors are well defined on immediate postgadolinium spoiled gradient echo images.
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J Magn Reson Imaging · Jan 1997
ReviewPrinciples of contrast enhancement in the evaluation of brain diseases: an overview.
Intravenous contrast media are widely used in MR imaging of the brain. Clinical utility is high in both neoplastic and non-neoplastic disease. The agents approved to date are all gadolinium chelates, with extracellular distribution and renal excretion. ⋯ In many cases, lesions cannot be identified before contrast administration. Lesion delineation, assessment of lesion activity, and differential diagnosis are all improved, in general, with the addition of postcontrast scans. The scope of applications continues to expand as the modality and clinical experience matures.