Two- and three-dimensional numerical analysis of gradient and parasitic gradient fields of a three-channel surface gradient coil for magnetic resonance imaging

For many organ-specific magnetic resonance imaging (MRI) applications, surface gradient coils (SGCs) offer an attractive alternative to the whole-body gradient coils presently employed in MR scanners. This investigation develops a 2D and 3D numerical analysis and design strategy based on the magnetic scalar and vector potentials to obtain the field strength and field linearity within a localized imaging area. It is demonstrated that for a predefined volume of interest, a given planar SGC configuration can achieve up to 80 Gauss/cm magnetic field gradient, which significantly exceeds the 1-3 Gauss/cm of whole-body coils based on the same current excitation of 100 A and inductance employed in typical whole-body instruments. In order to test the accuracy of the authors´ numerical design, a G_y gradient coil was fabricated. It is found that the measured field distribution is in excellent agreement with the authors´ 3D theoretical predictions. Furthermore, this G_y gradient coil was installed in a GE CSI II 2 Tesla 15 cm bore MRI instrument which permits a direct comparison of the image quality with the computer predicted field linearity. Therefore, this numerical modeling approach proves very useful in analyzing and ultimately optimizing planar SGC coils for organ-specific MRI applications