Simultaneous use of linear and nonlinear gradients for B1 + inhomogeneity correction

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buir.contributor.authorAtalar, Ergin
dc.citation.epage15en_US
dc.citation.issueNumber9en_US
dc.citation.spage1en_US
dc.citation.volumeNumber30en_US
dc.contributor.authorErtan, K.en_US
dc.contributor.authorAtalar, Erginen_US
dc.date.accessioned2018-04-12T10:38:44Z
dc.date.available2018-04-12T10:38:44Z
dc.date.issued2017en_US
dc.departmentNational Magnetic Resonance Research Center (UMRAM)en_US
dc.departmentDepartment of Electrical and Electronics Engineeringen_US
dc.description.abstractThe simultaneous use of linear spatial encoding magnetic fields (L-SEMs) and nonlinear spatial encoding magnetic fields (N-SEMs) in B1 + inhomogeneity problems is formulated and demonstrated with both simulations and experiments. Independent excitation k-space variables for N-SEMs are formulated for the simultaneous use of L-SEMs and N-SEMs by assuming a small tip angle. The formulation shows that, when N-SEMs are considered as an independent excitation k-space variable, numerous different k-space trajectories and frequency weightings differing in dimension, length, and energy can be designed for a given target transverse magnetization distribution. The advantage of simultaneous use of L-SEMs and N-SEMs is demonstrated by B1 + inhomogeneity correction with spoke excitation. To fully utilize the independent k-space formulations, global optimizations are performed for 1D, 2D RF power limited, and 2D RF power unlimited simulations and experiments. Three different cases are compared: L-SEMs alone, N-SEMs alone, and both used simultaneously. In all cases, the simultaneous use of L-SEMs and N-SEMs leads to a decreased standard deviation in the ROI compared with using only L-SEMs or N-SEMs. The simultaneous use of L-SEMs and N-SEMs results in better B1 + inhomogeneity correction than using only L-SEMs or N-SEMs due to the increased number of degrees of freedom.en_US
dc.description.provenanceMade available in DSpace on 2018-04-12T10:38:44Z (GMT). No. of bitstreams: 1 bilkent-research-paper.pdf: 179475 bytes, checksum: ea0bedeb05ac9ccfb983c327e155f0c2 (MD5) Previous issue date: 2017en
dc.embargo.release2019-08-15en_US
dc.identifier.doi10.1002/nbm.3742en_US
dc.identifier.issn0952-3480
dc.identifier.urihttp://hdl.handle.net/11693/36403
dc.language.isoEnglishen_US
dc.publisherJohn Wiley and Sons Ltden_US
dc.relation.isversionofhttp://dx.doi.org/10.1002/nbm.3742en_US
dc.source.titleNMR in Biomedicineen_US
dc.subjectB1 + inhomogeneityen_US
dc.subjectExcitation k-spaceen_US
dc.subjectNonlinear gradientsen_US
dc.subjectSimultaneous use of linear and nonlinear gradientsen_US
dc.subjectSmall tip angleen_US
dc.subjectSpoke excitationen_US
dc.titleSimultaneous use of linear and nonlinear gradients for B1 + inhomogeneity correctionen_US
dc.typeArticleen_US

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