title: A programmable pre-emphasis system.
abstract: MRI systems often use magnetic field gradient and shim pulse-shaping networks (pre-emphasis) to correct for magnetic field distortions caused by eddy currents. A pre-emphasis system that uses up to 16 fixed resistor-capacitor (RC) time constants per channel with programmable amplitude coefficients is described. The magnetic fields induced by the pre-emphasis RC time constants serve as a set of basis functions for compensating eddy-current fields induced by the gradient set. The resultant time-varying magnetic field gradient accurately reflects the gradient specified by the pulse programmer. Reductions in eddy-current fields are demonstrated for actively shielded and unshielded gradient sets.
authors.affiliation: Department of Physics and Astronomy, University of Pittsburgh, Pennsylvania, USA.
authors.forename: H M
authors.initials: HM
authors.lastname: Gach
authors.forename: I J
authors.initials: IJ
authors.lastname: Lowe
authors.forename: D P
authors.initials: DP
authors.lastname: Madio
authors.forename: A
authors.initials: A
authors.lastname: Caprihan
authors.forename: S A
authors.initials: SA
authors.lastname: Altobelli
authors.forename: D O
authors.initials: DO
authors.lastname: Kuethe
authors.forename: E
authors.initials: E
authors.lastname: Fukushima
mesh_terms: D016477:Artifacts; D003199:Computer Systems; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D012984:Software