OPTIMIZATION OF TORQUE-BALANCED ASYMMETRIC HEAD GRADIENT COILS

Local gradient coils can improve the performance of echo-planar, diffu sion, and short TE imaging in the brain, A modified singular value dec omposition algorithm, which allows the rapid optimization and comparis on of designs, was employed to optimize head size gradient coils, A th eoretical expression for the torque on a cylindrical coil is presented and used to design coils that are free from torque while pulsed withi n a magnetic field, Gradient coils of various lengths both with and wi thout torque constraints were compared; although torque-free coils do not perform as well as unbalanced coils, asymmetric torque-balanced co ils can achieve comparable homogeneity with only a modest increase in inductance and resistance, Both types of coils outperform body size gr adient coils by a dramatic margin, A three-axis head gradient designed using these techniques was constructed and used for brain imaging on a clinical scanner.