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

Volume

7

Issue

3

fYear

1988

fDate

9/1/1988 12:00:00 AM

Firstpage

247

Lastpage

254

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;

fLanguage

English

Journal_Title

Medical Imaging, IEEE Transactions on

Publisher

ieee

ISSN

0278-0062

Type

jour

DOI

10.1109/42.7789

Filename

7789