ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
High performance magnetic field gradient coils have always been desirable in today's ultrafast magnetic resonance imaging (MRI) applications, such as single-shot echo-planar imaging and fast spin echo imaging, as well as MR diffusion imaging and microscopy. We present a Lagrange multiplier technique of a minimum inductance gradient coil with spherical geometry. Based on this minimization approach, we construct a functional F in terms of the stored magnetic energy, the magnetic field and a set of field constraint points which are chosen over the desired imaging volume. Minimizing F, we obtain the continuous current density distribution for the spherical gradient coil. Applying the stream function technique to the continuous current distribution, the discrete current pattern can then be generated. Employing the Biot–Savart law to the discrete current loops, the gradient magnetic field has been re-evaluated in order to validate the theory. Using this approach, we have been able to design a spherical z-gradient coil which is capable of generating a gradient field of 176 mT/m with slew rate of 3422 T/m/s over a 30-cm-diam spherical volume if driven by a 350 V–220 A current amplifier. A prototype of the spherical z-gradient coil has been built. The agreement between the analytical and experimental results is excellent. Initial imaging experiments have been conducted. The results indicate the potential use of such a coil for in vivo and in vitro fast NMR applications. © 1997 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.364899
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