A combinatorial method based on simulated annealing to design a biplanar MRI gradient system

Gradient coils are a main part of a Magnetic Resonance Imaging (MRI) system. The aim of gradient coils in a MRI system is to encode spatially the Field of View (FoV). Different gradient coil design methods have been presented in the last years. Some factors such as linearity, inductance and resistance must be taken in account to obtain an optimized design for the gradient coils. A combinatorial method to design the MRI gradient coils is presented. The method developed uses very simple shapes to obtain the coil path pattern and it allows finding the best coil design in a time less than 2 minutes. Path combination which generates the highest gradient field is chosen for the X/Y gradient coil, and also the most homogeneous magnetic field is considered to select the Z-gradient path combination. Efficiencies values of 9.3 and 19.4 mT/m/A are obtained for X/Y and Z gradient coil, respectively. The gradient system has been tested in a biplanar permanent magnet (PM) system. Experimental gradient coil evaluation shows the ability to generate a strong gradient field (0.56 and 0.75 T/m for X/Y and Z gradient coil, respectively). A preliminary 2D MRI image with 1mm accuracy is obtained.