The response of different magnetic resonance (MR) techniques to tissue parameters - T1, T2, and N(H) - is a determinant of clinical efficacy. The large possible number of imaging techniques and range of variable parameters for each make it difficult to perform exhaustive evaluations in a single patient or even in animal models. In addition, changes in operating magnetic field strength change the relaxation times sufficiently so that the efficacy of a technique at a given field does not imply similar results at another field value. Tools are demonstrated that permit the evaluation of the efficacy of any model of response to tissue parameters, and also allow the investigation of the effects of changing magnetic field. Global maps of signal difference between tissues as well as calculated images are obtainable from a minimally sufficient data set. These tools serve as an important adjunct to experimental work.
Spin-echo magnetic resonance (MR) imaging detects a variety of pathologic states with great sensitivity. A technique for producing multiple spin-echo images in multisection operation is presented. This method of intensity-image acquisition is compared with retrospective intensity-image synthesis from routine data sets. Both yield long echo time (TE) images with similar image contrast and comparable and often increased diagnostic utility. Technical and clinical considerations are addressed, including signal-to-noise levels, flow effects, and patient throughput.
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