A programmable pre-emphasis system.
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.
Gach
H M
HM
Department of Physics and Astronomy, University of Pittsburgh, Pennsylvania, USA.
Lowe
I J
IJ
Madio
D P
DP
Caprihan
A
A
Altobelli
S A
SA
Kuethe
D O
DO
Fukushima
E
E
D016477:Artifacts; D003199:Computer Systems; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D012984:Software