EXTERNAL MAGNETIC FIELD MEASURING DEVICE, STATIC MAGNETIC FIELD CORRECTING METHOD, EXTERNAL MAGNETIC FIELD MEASURING DEVICE AND MRI SYSTEM

摘要

PURPOSE: To cancel influence of an external magnetic field on a static magnetic field of an MRI system. CONSTITUTION: A compensating magnetic field is generated from small coils 16t and 16b to cancel a component of the static magnetic field B0 imparted to a magnetic sensor 16z, and the external magnetic field is highly accurately detected by the magnetic sensor 16z. A corrective current I based on the highly accurately detected external magnetic field is made to flow to a B0 correction coil 21 to cancel the external magnetic field having influence on the static magnetic field B0. Thus, the magnetic sensor 16z having a dynamic range capable of highly accurately detecting the external magnetic field can be arranged in the vicinity of a magnet unit 31, and the external magnetic field having influence on the static magnetic field B0 can be highly accurately measured. The influence of the external magnetic field on the static magnetic field B0 can be highly accurately canceled.