PROBLEM TO BE SOLVED: To address such a problem that, in a small-sized magnet that is short in an axial direction of an MRI magnet requiring a uniform magnetic field space, the uniform magnetic space becomes short in the axial direction and a region to be imaged at one time is limited； and to provide a magnetic-field adjusting shim coil capable of expanding the uniform magnetic field space in response to a necessary part of a body, and an MRI apparatus comprising the same.SOLUTION: The superconducting magnet device calculates a response matrix from a line current group disposed on a small circular cylinder having a smaller radius than that of a main coil, to an imaging region, and selects from eigenmodes obtained by a singular value decomposition. Especially, a fifth one of the eigenmodes that is axially symmetrical and a third eigenmode is used. The uniform magnetic space to be expanded as the need arises can be secured by designing the coil just like a current having positive/negative five peaks of the eigenmode.SELECTED DRAWING: Figure 3COPYRIGHT: (C)2018,JPO&INPIT【課題】 均一な磁場空間を必要とするＭＲＩ用磁石の軸方向に短い小型の磁石では、均一磁場空間が軸方向短くなり、一度に撮像できる領域が制限される。これを、身体の必要部分に応じて、均一磁場空間を拡張できる磁場調整用シムコイルおよびこれを備えたＭＲＩ装置を提供する。【解決手段】 主コイルより半径の小さい円筒上に配置した線電流群から撮像領域への応答行列を求め、この特異値分解で得られる固有モードから選択する。特に、５番目で、軸対称のもので３番目の固有モードを用いる。この固有モードの正負５個のピークを持つ電流のようにコイル設計を行うことで、必要に応じて拡張された均一磁場空間を確保できる。【選択図】 図３
