| MR image contrast at high field strength. | |
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MedLine Citation:
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PMID: 1790367 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The T1 of soft tissues increases with magnetic field strength. Some tissue contrast may be diminished on high-field-strength magnetic resonance (MR) images when conventional TRs are used, because of altered T1 effects on the MR signals. This necessitates longer TRs in techniques that use long TRs, which prolongs the examination excessively. Behavior of macroscopic magnetization is governed by the Bloch equations. Therefore, T1 contributions to the MR signal can be modulated by means of both timing intervals and radio-frequency pulses. The analytic solution to the Block equations allowed calculation of white matter/gray matter and gray matter/cerebrospinal fluid contrast in both spin-echo and inversion-recovery (IR) imaging. Rabbit brains (normal and tumor-containing) were then imaged in vivo at 1.5 and 4.7 T. In addition, MR images of a human head were obtained at 4.0 T. Experimental results supported the theoretical predictions that brain contrast on long TR spin-echo or IR images increases with field strength. However, varying the excitation flip angle allowed optimization of the T1 contribution to the MR signals, improving image contrast and/or reducing examination time. Thus, the dependence of T1 on field strength determines the optimum choice of imaging techniques and parameters in a predictable fashion. |
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Authors:
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S Vinitski; R H Griffey |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Journal of magnetic resonance imaging : JMRI Volume: 1 ISSN: 1053-1807 ISO Abbreviation: J Magn Reson Imaging Publication Date: 1991 Jul-Aug |
Date Detail:
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Created Date: 1992-04-02 Completed Date: 1992-04-02 Revised Date: 2004-11-17 |
Medline Journal Info:
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Nlm Unique ID: 9105850 Medline TA: J Magn Reson Imaging Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 451-6 Citation Subset: IM |
Affiliation:
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Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, PA 19107. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals Brain / anatomy & histology Brain Neoplasms / diagnosis Humans Magnetic Resonance Imaging / methods* Rabbits |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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