No abstract

Patterns of intracranial signal intensity on magnetic resonance (MR) images were studied in nine patients undergoing long-term total parenteral nutrition therapy. The duration of therapy ranged from 5 months to 11 years (mean, 5.3 years). Symmetric increased signal intensity on T1-weighted MR images (hyperintense relative to white matter) was observed in the basal ganglia of all patients, without corresponding abnormality on T2-weighted images. Analysis of signal-intensity characteristics and distribution pattern suggests that the basis for these changes may be deposition of intravenously administered paramagnetic trace elements, especially manganese, and/or an astrogliotic reaction to such deposition.

Echo-planar imaging is a very fast magnetic resonance (MR) imaging technique capable of acquiring an entire MR image in only a fraction of a second. In single-shot echo-planar imaging, all the spatial-encoding data of an image can be obtained after a single radio-frequency excitation. Multishot echo-planar imaging results in high-quality images comparable to conventional MR images. However, echo-planar imaging offers major advantages over conventional MR imaging, including reduced imaging time, decreased motion artifact, and the ability to image rapid physiologic processes of the human body. The use of echo-planar imaging has already resulted in significant advances in clinical diagnosis and scientific investigation, such as in evaluation of stroke and functional imaging of the human brain, respectively. The clinical indications for echo-planar imaging are expanding rapidly, and it can now be applied to many parts of the body, including the brain, abdomen, and heart. Today, with the availability of echo-planar imaging-capable MR imagers at many sites, the general radiologist can benefit from echo-planar imaging and its clinical applications.