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Coil optimization for MRI by conjugate gradient descent
Author(s) -
Wong Eric C.,
Jesmanowicz A.,
Hyde James S.
Publication year - 1991
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910210107
Subject(s) - conjugate gradient method , gradient descent , descent (aeronautics) , conjugate , computer science , nuclear magnetic resonance , nonlinear conjugate gradient method , artificial intelligence , physics , mathematics , algorithm , mathematical analysis , artificial neural network , meteorology
A flexible iterative algorithm is presented for optimizing gradient and radio frequency coils for MRI. It is based on a model using discrete current elements and direct Biot‐Savart calculation of the fields. An error function is defined over a region of interest (ROI) and is minimized by conjugate gradient descent. The choice of error function allows optimization of the field uniformity, the inductance, and the efficiency of the coil in any combination. Neither the coil nor the ROI is restricted to any particular geometry. A 40‐ turn cylindrical z‐gradient coil of radius a and length 4 a , designed for a ROI of radius 0.7 a and length 2 a has an average error in the gradient fields generated of 0.85%, an inductance of 0.014 a mH/cm, and an efficiency of 6.65 a −2 Gem/A. A 16‐turn birdcage‐like RF coil of radius 5 cm, designed for a ROI of radius 4 cm has an average error of 0.79%. © 1991 Academic Press, Inc.