Abstract: An apparatus for magnetic resonance imaging having a magnetic assembly with a main magnet, a shielding system positioned outside the main magnet, and a first and second space for positioning the imaged and non-imaged extremity. Various apparatus with distinct vessels and casings are described with a magnetic assembly and ferromagnetic shielding systems. In yet a further aspect, an apparatus for resonance imaging having additional shim elements for compensating effects from non-axisymmetrical shape of ferromagnetic shielding casing is disclosed. Additionally, an apparatus for magnetic resonance imaging is described having a dedicated space outside the imaging region and where the dedicated space has support element for resting non-image extremity as part of the structure of the imager.

Abstract: An imaging system 10 is provided comprising an imaging magnet 16 having a magnet bore 18. A plurality of passive shims 26 is positioned within the magnet bore 18. A plurality of resistive shims 46 is also positioned within the magnet bore 18. A plurality of thermometers 28 is coupled thermally to a select number of the plurality of passive shims 26 and read a passive shim temperature 36. A controller 32 is in communication with the plurality of thermometers 28 and the plurality of resistive shims 46. The controller 32 includes logic adapted to adjust control currents 40 sent to each of the plurality of resistive shims 46 in response to the resistive shim temperatures 36 received from each of the thermometers 28 such that the strength of the magnetic field and its homogeneity is maintained.