Title :
Exact temporal eddy current compensation in magnetic resonance imaging systems
Author :
Morich, M.A. ; Lampman, David A. ; Dannels, Wayne R. ; Goldie, Frederick T D
Author_Institution :
Picker Int. Inc., Highland Heights, OH, USA
fDate :
9/1/1988 12:00:00 AM
Abstract :
A step-response method has been developed to extract the properties (amplitudes and decay time constants) of intrinsic-eddy-current-sourced magnetic fields generated in whole-body magnetic resonance imaging systems when pulsed field gradients are applied. Exact compensation for the eddy-current effect is achieved through a polynomial rooting procedure and matrix inversion once the 2 N properties of the N-term decay process are known. The output of the inversion procedure yields the required characteristics of the filter for spectrum magnitude and phase equalization. The method is described for the general case along with experimental results for one-, two-, and three-term inversions. The method´s usefulness is demonstrated for the usually difficult case of long-term (200-1000-ms) eddy-current compensation. Field-gradient spectral flatness measurements over 30 mHz-100 Hz are given to validate the method
Keywords :
biomedical NMR; eddy currents; patient diagnosis; 30 mHz to 100 Hz; N-term decay process; exact temporal eddy current compensation; field-gradient spectral flatness; magnetic resonance imaging systems; matrix inversion; medical diagnostic imaging; phase equalization; polynomial rooting procedure; pulsed field gradients; spectrum magnitude; step-response method; whole-body NMR imaging; Current measurement; Eddy currents; Filters; Magnetic field measurement; Magnetic fields; Magnetic properties; Magnetic resonance imaging; Nuclear magnetic resonance; Pulse generation; Superconducting magnets;
Journal_Title :
Medical Imaging, IEEE Transactions on
