Limiting RF alternating magnetic field in MRI

A method for limiting an RF (radio frequency) alternating magnetic field in MR (magnetic resonance) scanning, wherein the method comprises:

• measuring a perpendicular distance between a local coil placed on a scanned part of a patient and a top point of a detection hole wall of an MR scanner;
• acquiring a maximum permissible field strength of the RF alternating magnetic field required when a surface temperature of the local coil is equal to a safe temperature upper limit;
• and
• based on the perpendicular distance and the maximum permissible field strength, determining an RF operating voltage of the MR scanner.

An apparatus for limiting an RF (radio frequency) alternating magnetic field in MRI (magnetic resonance imaging), comprising:

• a distance measurement module configured to measure a perpendicular distance between a local coil placed on a scanned part of a patient and a center of a detection hole of an MR scanner;
• a field strength deviation detection module configured to determine, based on the perpendicular distance between the local coil and the center of the detection hole, a deviation between the field strength of the RF alternating magnetic field at a position of the local coil during an MR scan and the field strength of the RF alternating magnetic field at the center of the detection hole;
• a field strength conversion coefficient computing module configured to compute, based on the deviation, a conversion coefficient for conversion between the field strength of the RF alternating magnetic field at the position of the local coil and the field strength of the RF alternating magnetic field at the center of the detection hole;
• and
• a field strength limiting module configured to compute, based on the field strength of the RF alternating magnetic field required when a surface temperature of the local coil is equal to a safe temperature upper limit and the conversion coefficient, a maximum permissible field strength of the RF alternating magnetic field at the center of the detection hole.

An apparatus for limiting an RF (radio frequency) alternating magnetic field in MR (magnetic resonance) scanning, comprising:

• a distance measurement module configured to measure a perpendicular distance between a local coil placed on a scanned part of a patient and a top point of a detection hole wall of an MR scanner;
• a field strength limiting module configured to acquire a maximum permissible field strength of the RF alternating magnetic field required when a surface temperature of the local coil is equal to a safe temperature upper limit;
• and
• a scanning control module configured to determine an RF operating voltage of the MR scanner based on the perpendicular distance and the maximum permissible field strength.