Active shield gradient coil for nuclear magnetic resonance imaging apparatus

A nuclear magnetic resonance imaging apparatus, comprising:

• a gradient coil including
• a primary coil having a fingerprint shaped current distribution formed on an inner cylinder in which at least a part of current return lines is cut out to form a cut out part with broken current return lines;
• a shield coil having a current distribution formed on an outer cylinder;
• and
• a bridging connection member for connecting the cut out part of the current return lines of the primary coil with the shield coil;
• wherein the current distribution of the shield coil is a composition of a first shield pattern for cancelling out a magnetic field produced by the primary coil outside the outer cylinder and a second shield pattern for cancelling out a magnetic field produced by the bridging connection member outside the outer cylinder;
• and
• imaging means for imaging a body to be examined placed in a homogeneous static magnetic field by applying a radio frequency magnetic field onto the body to be examined and operating the gradient coil to apply gradient magnetic fields onto the body to be examined according to a pulse sequence, detecting nuclear magnetic resonance signals emitted from the body to be examined in response to the radio frequency magnetic field and the gradient magnetic fields, and processing the nuclear magnetic resonance signals to construct nuclear magnetic resonance images.

A nuclear magnetic resonance imaging apparatus, comprising:

• a gradient coil including
• a primary coil having a fingerprint shaped current distribution formed on an inner cylinder in which at least a part of current return lines is cut out to form a cut out part with broken current return lines, and turn back current paths for leading the cut out part of the current return lines on one end of the gradient coil to another end of the gradient coil;
• and
• a shield coil having a current distribution formed on an outer cylinder for cancelling out a magnetic field produced by the primary coil outside the outer cylinder;
• and
• imaging means for imaging a body to be examined placed in a homogeneous static magnetic field by applying a radio frequency magnetic field onto the body to be examined and operating the gradient coil to apply gradient magnetic fields onto the body to be examined according to a pulse sequence, detecting nuclear magnetic resonance signals emitted from the body to be examined in response to the radio frequency magnetic field and the gradient magnetic fields, and processing the nuclear magnetic resonance signals to construct nuclear magnetic resonance images.