TY - JOUR
T1 - Quantification and compensation of eddy-current-induced magnetic-field gradients
AU - Spees, William M.
AU - Buhl, Niels
AU - Sun, Peng
AU - Ackerman, Joseph J.H.
AU - Neil, Jeffrey J.
AU - Garbow, Joel R.
N1 - Funding Information:
Support for this work was provided by the National Institute of Health NCI Small Animal Imaging Resource Program (U24CA083060) and National Institute of Biomedical Imaging and Bioengineering (5R01EB002083-11). Niels Buhl was supported by funding from the Danish National Research Foundation. Dr. Daniel Green of Agilent Technologies is gratefully acknowledged for valuable discussions. We are indebted to Dr. G. Larry Bretthorst for assistance with Bayesian modeling. Free download of the Bayesian tool box and users manual is available at URL http://bayesiananalysis.wustl.edu/ .
PY - 2011/9
Y1 - 2011/9
N2 - Two robust techniques for quantification and compensation of eddy-current-induced magnetic-field gradients and static magnetic-field shifts (ΔB0) in MRI systems are described. Purpose-built 1-D or six-point phantoms are employed. Both procedures involve measuring the effects of a prior magnetic-field-gradient test pulse on the phantom's free induction decay (FID). Phantom-specific analysis of the resulting FID data produces estimates of the time-dependent, eddy-current-induced magnetic field gradient(s) and ΔB0 shift. Using Bayesian methods, the time dependencies of the eddy-current-induced decays are modeled as sums of exponentially decaying components, each defined by an amplitude and time constant. These amplitudes and time constants are employed to adjust the scanner's gradient pre-emphasis unit and eliminate undesirable eddy-current effects. Measurement with the six-point sample phantom allows for simultaneous, direct estimation of both on-axis and cross-term eddy-current-induced gradients. The two methods are demonstrated and validated on several MRI systems with actively-shielded gradient coil sets.
AB - Two robust techniques for quantification and compensation of eddy-current-induced magnetic-field gradients and static magnetic-field shifts (ΔB0) in MRI systems are described. Purpose-built 1-D or six-point phantoms are employed. Both procedures involve measuring the effects of a prior magnetic-field-gradient test pulse on the phantom's free induction decay (FID). Phantom-specific analysis of the resulting FID data produces estimates of the time-dependent, eddy-current-induced magnetic field gradient(s) and ΔB0 shift. Using Bayesian methods, the time dependencies of the eddy-current-induced decays are modeled as sums of exponentially decaying components, each defined by an amplitude and time constant. These amplitudes and time constants are employed to adjust the scanner's gradient pre-emphasis unit and eliminate undesirable eddy-current effects. Measurement with the six-point sample phantom allows for simultaneous, direct estimation of both on-axis and cross-term eddy-current-induced gradients. The two methods are demonstrated and validated on several MRI systems with actively-shielded gradient coil sets.
KW - Eddy currents
KW - Eddy-current compensation
KW - Gradient pre-emphasis
KW - MRI
UR - http://www.scopus.com/inward/record.url?scp=84855410933&partnerID=8YFLogxK
U2 - 10.1016/j.jmr.2011.06.016
DO - 10.1016/j.jmr.2011.06.016
M3 - Article
C2 - 21764614
AN - SCOPUS:84855410933
SN - 1090-7807
VL - 212
SP - 116
EP - 123
JO - Journal of Magnetic Resonance
JF - Journal of Magnetic Resonance
IS - 1
ER -