Magnetic resonance imaging apparatus
To suppress eddy current generation by a gradient magnetic field while an RF shield has a function of reducing magnetic coupling of an RF coil with a gradient magnetic coil, the RF shield must be formed of a conductive material of a tiled or slitted strip-shaped thin plate. On the other hand, cooling must be performed to suppress temperature rise due to heat generation by the eddy current. Furthermore, to enlarge an opening through which a patient is inserted, the gradient magnetic coil, the RF coil, and the RF shield, which are located in a static field magnet and have roughly concentrically cylindrical shapes, are required to be reduced in thickness. To solve the above problem, the present invention provides a structure, where an RF shield, which is obtained by forming a tiled or slitted thin-plate conductive material into a sheet, is adhered or attached to an inner cylindrical surface of the gradient magnetic coil, where the RF shield is configured to be adhered or attached to a region including the vicinity of each of turn centers of an X-gradient magnetic coil pattern and a Y-gradient magnetic coil pattern, or is adhered or attached along a pattern on or a slit in the thin plate conductive material of the RF shield.
1. A magnetic resonance imaging apparatus, comprising:
a magnetic pole generating a static magnetic field in an imaging space;
a gradient magnetic coil generating a dynamic magnetic field with linear magnetic field strength with respect to a position in the imaging space;
a radio frequency coil generating a radio-frequency magnetic field in the imaging space; and
a radio frequency (RF) shield located between the gradient magnetic coil and the radio-frequency coil and reducing electromagnetic coupling of the radio-frequency magnetic field with the gradient magnetic coil,
wherein the RF shield is installed so as to be adhered or attached to a surface of the gradient magnetic coil, and an adhesion or attachment position corresponds to a region near the turn center of a winding of an X- or Y-gradient magnetic coil conductor forming the gradient magnetic coil.
2. The magnetic resonance imaging apparatus according to claim 1 , wherein the RF shield is formed by attaching a pattern of a strip-shaped thin-film conductive material to a sheet-shaped member formed of an insulating material, and is adhered or attached to the gradient magnetic coil at an end of the pattern of the conductive material forming the RF shield or at a position along a groove between the patterns.
3. The magnetic resonance imaging apparatus according to claim 2 , wherein at least one-third of area of the RF shield formed in the sheet shape is adhered or attached to the gradient magnetic coil.
4. The magnetic resonance imaging apparatus according to claim 3 , wherein the magnetic pole, the gradient magnetic coil, the radio-frequency coil, and the RF shield have roughly concentrically cylindrical shapes and are located on a roughly common axis including the imaging space, and the RF shield is adhered or attached to an inner cylindrical surface of the gradient magnetic coil.
5. The magnetic resonance imaging apparatus according to claim 3 , wherein the magnetic pole, the gradient magnetic coil, the radio-frequency coil, and the RF shield each have a rough shape of a pair of discs opposed across the imaging space to each other, and the RF shield is adhered or attached to a surface on a side near the imaging space of the gradient magnetic coil.
6. The magnetic resonance imaging apparatus according to claim 2 , wherein the magnetic pole, the gradient magnetic coil, the radio-frequency coil, and the RF shield have roughly concentrically cylindrical shapes and are located on a roughly common axis including the imaging space, and the RF shield is adhered or attached to an inner cylindrical surface of the gradient magnetic coil.
7. The magnetic resonance imaging apparatus according to claim 2 , wherein the magnetic pole, the gradient magnetic coil, the radio-frequency coil, and the RF shield each have a rough shape of a pair of discs opposed across the imaging space to each other, and the RF shield is adhered or attached to a surface on a side near the imaging space of the gradient magnetic coil.
8. The magnetic resonance imaging apparatus according to claim 1 , wherein the magnetic pole, the gradient magnetic coil, the radio-frequency coil, and the RF shield have roughly concentrically cylindrical shapes and are located on a roughly common axis including the imaging space, and the RF shield is adhered or attached to an inner cylindrical surface of the gradient magnetic coil.
9. The magnetic resonance imaging apparatus according to claim 1 , wherein the magnetic pole, the gradient magnetic coil, the radio-frequency coil, and the RF shield each have a rough shape of a pair of discs opposed across the imaging space to each other, and the RF shield is adhered or attached to a surface on a side near the imaging space of the gradient magnetic coil.