Multiple-region gradient arrays for extended field of view, increased performance, and reduced nerve stimulation in magnetic resonance imaging.
This article presents a novel design for magnetic resonance imaging (MRI) gradient systems. This design may allow the development of MRI scanners that are capable of imaging large regions with high performance while minimizing the potential for nerve stimulation. The general concept of the gradient system is that spatial oscillation is incorporated such that each gradient coil creates multiple, approximately linear gradient regions that oscillate in gradient polarity. Separate radiofrequency (RF) coil arrays are designed to be sensitive to the signals within each linear region and thus allow signal measurements to be obtained separately from each region. Enabling image acquisition in the transition region that separates each pair of adjacent linear regions requires a second gradient system with imaging regions that overlap and coincide with the transition regions of the first gradient system. Imaging the extended field of view (FOV) is accomplished by interleaved operation of the two gradient systems. Simulated annealing is used to create designs for both longitudinal and transverse gradient systems with two imaging regions.