초록

A hybrid shielding arrangement for solenoid type cryogenic magnets used in MR systems uses both active and passive shielding elements to improve the effective shielding.

대표청구항 ▼

An integrated shielding arrangement for solenoid type cryogenic super conducting magnets such as used in magnetic resonance (MR) systems to reduce the fringe magnetic fields generated by the solenoid magnet, said arrangement comprising: a dewar having an inner wall and outer wall, a first solenoid c

An integrated shielding arrangement for solenoid type cryogenic super conducting magnets such as used in magnetic resonance (MR) systems to reduce the fringe magnetic fields generated by the solenoid magnet, said arrangement comprising: a dewar having an inner wall and outer wall, a first solenoid coil within said dewar for generating a first large static magnet field in a central bore of said magnet of the MR system, said field having a first lines of force extending in a first direction, a second solenoid coil within said dewar for generating an opposite going second magnetic field with second lines of force extending in an opposite direction to the first lines of force to cancel at least some of the first lines force external to the first solenoid to decrease fringe field effects, said second magnetic field also tending to decrease the lines of force in the central bore, first means for reducing the reluctance to flux lines located between the first and second solenoid coil to enable energizing the second coil with a lower current to assure less of a decrease in the central bore compared to the reduction of the magnetic field at the central bore when the first means for reducing the reluctance is absent, and second means for reducing the reluctance to flux lines located external to the second solenoid coil.