MAGNETIC RESONANCE IMAGE PICKUP DEVICE AND METHOD OF DESIGNING GRADIENT COIL FOR MAGNETIC RESONANCE IMAGE PICKUP DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a nuclear magnetic resonance camera instrument capable of facilitating the equipment and constitution of a gradient coil and by which the access to patient body is promoted in the examination area and pictures are improved. SOLUTION: The nuclear magnetic resonance camera instrument includes a superconducting magnet 10 that generates a temporally constant magnetic field in a bore 12. Both of the bore and the superconducting magnet have lengths which are relatively short compared to their respective diameters, for example, ratio of length to diameter is smaller than 1.5:1, and preferably 1:1. The gradient coil assembly 30 of the instrument is disposed around the bore and it generates a gradient magnetic field across the bore. With this relatively short bore magnet, in the region in which the gradient magnetic field coil is disposed, the main magnetic field suffers nonuniformities including radial magnetic field components. While current pulses are fed through the windings of a primary gradient coil 32 and a secondary gradient coil 34 of the gradient coil assembly, the currents interact in an unbalanced manner with the nonuniformities and the radial components of the temporally constant magnetic field, causing a net force in axial and/or transverse direction.