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Development and optimization of hardware for delta relaxation enhanced MRI
Author(s) -
Harris Chad T.,
Handler William B.,
Araya Yonathan,
MartínezSantiesteban Francisco,
Alford Jamu K.,
Dalrymple Brian,
Sas Frank,
Chronik Blaine A.,
Scholl Timothy J.
Publication year - 2014
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.25014
Subject(s) - electromagnet , electromagnetic shielding , resistive touchscreen , magnet , cryostat , eddy current , electromagnetic coil , shielded cable , nuclear magnetic resonance , shield , magnetic field , superconducting magnet , computer science , magnetic resonance imaging , acoustics , physics , materials science , mechanical engineering , electrical engineering , superconductivity , condensed matter physics , engineering , petrology , telecommunications , medicine , radiology , quantum mechanics , geology , computer vision
Purpose Delta relaxation enhanced magnetic resonance (dreMR) imaging requires an auxiliary B 0 electromagnet capable of shifting the main magnetic field within a clinical 1.5 Tesla (T) MR system. In this work, the main causes of interaction between an actively shielded, insertable resistive B 0 electromagnet and a 1.5T superconducting system are systematically identified and mitigated. Methods The effects of nonideal fabrication of the field‐shifting magnet are taken into consideration through careful measurement during winding and improved accuracy in the design of the associated active shield. The shielding performance of the resultant electromagnet is compared against a previously built system in which the shield design was based on an ideal primary coil model. Hardware and software approaches implemented to eliminate residual image artifacts are presented in detail. Results The eddy currents produced by the newly constructed dreMR system are shown to have a significantly smaller “long‐time‐constant” component, consistent with the hypothesis that less energy is deposited into the cryostat of the MR system. Conclusion With active compensation, the dreMR imaging system is capable of 0.22T field shifts within a clinical 1.5T MRI with no significant residual eddy‐current fields. Magn Reson Med 72:1182–1190, 2014. © 2013 Wiley Periodicals, Inc.