Gach H M, Lowe I J, Madio D P, Caprihan A, Altobelli S A, Kuethe D O, Fukushima E
Department of Physics and Astronomy, University of Pittsburgh, Pennsylvania, USA.
Magn Reson Med. 1998 Sep;40(3):427-31. doi: 10.1002/mrm.1910400313.
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.
