Computational Algorithm for Estimating the Gradient Isocenter of an MRI Scanner

The isocenter of the magnetic gradient fields inside a magnetic resonance imaging scanner is an important parameter in gradient non-linearity distortion correction methods for MR images. Currently there is no established method for estimating the gradient isocenter. All existing correction methods assume that the gradient isocenter coincides with the DICOM coordinate center, which is close but not exactly the same as the gradient isocenter. A difference between gradient isocenter and DICOM coordinate center could compromise the accuracy of the correction method. The goal of this research was to develop a reasonably accurate estimation method of the 3D location of the gradient isocenter that was based on the geometry of a customdesigned phantom. We present a two-step algorithm for estimating the gradient isocenter and examine some of the possible numeric methods to be used on each step.