Abstract:
PURPOSE:Delta relaxation enhanced magnetic resonance (dreMR) imaging requires an auxiliary B0 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 B0 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.
journal_name
Magn Reson Medjournal_title
Magnetic resonance in medicineauthors
Harris CT,Handler WB,Araya Y,Martínez-Santiesteban F,Alford JK,Dalrymple B,Van Sas F,Chronik BA,Scholl TJdoi
10.1002/mrm.25014subject
Has Abstractpub_date
2014-10-01 00:00:00pages
1182-90issue
4eissn
0740-3194issn
1522-2594journal_volume
72pub_type
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