Driving mutually coupled gradient array coils in magnetic resonance imaging

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buir.contributor.authorErtan, Koray
dc.citation.epage1198en_US
dc.citation.issueNumber3en_US
dc.citation.spage1187en_US
dc.citation.volumeNumber82en_US
dc.contributor.authorErtan, Korayen_US
dc.date.accessioned2020-02-11T11:09:31Z
dc.date.available2020-02-11T11:09:31Z
dc.date.issued2019
dc.departmentDepartment of Electrical and Electronics Engineeringen_US
dc.departmentNational Magnetic Resonance Research Center (UMRAM)en_US
dc.description.abstractPurpose In contrast to conventional linear gradients, gradient coil arrays with arbitrary spatial dependency might experience strong mutual coupling. Although conventional gradient power amplifiers with feedback loop might compensate the effect of coupling, required voltages for the compensation are generally unknown and has to be considered beforehand to ensure that amplifier voltage limits are not exceeded. A first‐order circuit model is proposed to be used as a feedforward model which enables analytical formulas of required voltages to drive the mutually coupled gradient coil arrays. Theory and Methods A first‐order circuit model including the mutual couplings is provided to analytically calculate the input voltages and minimum achievable rise times for a given set of gradient array currents and amplifier limitations. Previously designed 9‐channel Z‐gradient coil array and home‐built gradient amplifiers (50 V and 20 A) are used in the experiments. Three sets of currents optimized for linear Z‐gradient, second‐order Z2, and third‐order Z3 fields are used in the bench‐top experiments. The current weightings for the linear Z‐gradient are also used as the readout gradient in the 3T MRI experiments. Results Current measurements for the example magnetic field profiles with minimum rise times are demonstrated for the simultaneous use of 9‐channel gradient coils and amplifiers. MRI experiments verify that a linear Z‐gradient field with a desired time waveform can be generated using a mutually coupled array coils. Conclusion Bench‐top and MRI experiments demonstrate the feasibility of the proposed circuit model and analytical formulas to drive the mutually coupled gradient coils.en_US
dc.embargo.release2020-09-01
dc.identifier.doi10.1002/mrm.27768en_US
dc.identifier.issn0740-3194
dc.identifier.urihttp://hdl.handle.net/11693/53267
dc.language.isoEnglishen_US
dc.publisherInternational Society for Magnetic Resonance in Medicineen_US
dc.relation.isversionofhttps://doi.org/10.1002/mrm.27768en_US
dc.source.titleMagnetic Resonance in Medicineen_US
dc.subjectFeedforward modelen_US
dc.subjectGradient arraysen_US
dc.subjectGradient power amplifiersen_US
dc.subjectMRIen_US
dc.subjectMutual couplingen_US
dc.subjectMutual inductanceen_US
dc.subjectMutually coupled gradient array coilsen_US
dc.titleDriving mutually coupled gradient array coils in magnetic resonance imagingen_US
dc.typeArticleen_US
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