title: An inverse methodology for high-frequency RF coil design for MRI with de-emphasized B1 fields.
abstract: An inverse methodology for the design of biologically loaded radio-frequency (RF) coils for magnetic resonance imaging applications is described. Free space time-harmonic electromagnetic Green's functions and de-emphasized B1 target fields are used to calculate the current density on the coil cylinder. In theory, with the B1 field de-emphasized in the middle of the RF transverse plane, the calculated current distribution can generate an internal magnetic field that can reduce the central overemphasis effect caused by field/tissue interactions at high frequencies. The current distribution of a head coil operating at 4 T (170 MHz) is calculated using an inverse methodology with de-emphasized B1 target fields. An in-house finite-difference time-domain routine is employed to evaluate B1 field and signal intensity inside a homogenous cylindrical phantom and then a complete human head model. A comparison with a conventional RF birdcage coil is carried out and demonstrates that this method can help in decreasing the normal bright region caused by field/tissue interactions in head images at 170 MHz and higher field strengths.
authors.affiliation: School of Information Technology and Electrical Engineering, University of Queensland, Brisbane QLD 4072, Australia.
authors.forename: Bin
authors.initials: B
authors.lastname: Xu
authors.forename: Qing
authors.initials: Q
authors.lastname: Wei
authors.forename: Feng
authors.initials: F
authors.lastname: Liu
authors.forename: Stuart
authors.initials: S
authors.lastname: Crozier
mesh_terms: D001921:Brain / Q000033:anatomy & histology* / Q000502:physiology*; D017076:Computer-Aided Design; D055590:Electromagnetic Phenomena / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005240:Feasibility Studies; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D008954:Models, Biological; D011846:Radio Waves; D014159:Transducers