Patent ID: 6448773
Filing Date: 2002-09-10
Classification: G01R

Abstract:
A method for evaluating eddy currents induced during gradient switching in an MRI system having a static magnetic field, B0, and gradient coils to induce gradients in the static field, the method comprising the steps of:a) placing an MR active test object at a center of an imaging volume of the MRI system and aligning the object along a predetermined direction for measurement of eddy currents; b) applying a first gradient pulse to a gradient coil to produce a switching gradient in the magnetic field B0 and acquiring signal data samples from a first pair of spin-echo NMR signals corresponding to two MRI slices located symmetrically apart along said measurement direction away from a center of the magnetic field B0; c) applying a second gradient pulse to the gradient coil, the second gradient pulse having a polarity opposite to the first gradient pulse, and acquiring signal data samples from a second pair of spin-echo NMR signals corresponding to the slices of step (b); d) determining precessing frequencies from acquired signal data samples for each spin-echo signal of the first and second pair of spin-echo NMR signals; and e) quantifying field gradients and/or field oscillations produced due to eddy currents from the precessing frequencies determined in step (d).