MAGNET DEVICE AND MAGNETIC RESONANCE IMAGING USING THE SAME

摘要

A magnet device which obtains a clear and sharp MR image by eliminating any irregular magnetic field generated in a magnetic field in an image pickup space of an MRI apparatus. A pair of stationary magnetic field generation sources (2a and 2b) and a pair of magnetic poles (4a and 4b) disposed facing each other in the vertical direction to sandwich an image pickup space (10) are supported by two ferromagnetic stays (8a and 8b) disposed in the right-and-left direction. Annular projections (6a and 6b) are disposed on opposing sides of the magnetic poles (4a and 4b). The width of a section in the radial direction is set to be small values (D1 and D3) in the right-and-left direction, and a large value (D0) in the longitudinal direction, so that the value is gradually changed between the two. In the magnet device (1), a positive irregular magnetic field is generated in an area close to the stays (8a and 8b) of the image pickup space (10). However, by setting the width of the annular projections (6a and 6b) in the right-and-left direction to be smaller than that of the other parts, the magnetic flux passing through the area and converged in the image pickup space (10) is reduced, thereby canceling the aforementioned positive irregular magnetic field.