Claims
- 1. In a magnetic resonance imaging apparatus in which the magnetic field homogeneity is perturbed by the presence of an object, a method of compensating for the perturbations comprising:
a) placing at least one electromagnetic coil around the object, and b) passing electrical currents through the coils to counteract the perturbations in the static magnetic field outside of the object.
- 2. The method as defined by claim 1 wherein at least two coils are used.
- 3. The method as defined by claim 2 wherein two coils are placed on opposing sides of the object.
- 4. The method as defined by claim 3 wherein the object is an x-ray detector, the plurality of coils including two coils positioned on two opposing sides of the detector and two coils positioned on two opposing ends of the detector.
- 5. The method as defined by claim 4 wherein the plurality of coils further includes a plurality of coplanar coils positioned adjacent to the bottom of the detector.
- 6. In a magnetic resonance imaging apparatus having a perturbing object which causes perturbations in a static magnetic field of the apparatus, a method of compensating for the perturbations outside of the perturbing object comprising:
a) placing compensating objects near the perturbing object, said compensating objects altering the magnetic field beyond the perturbing object, and b) adjusting the magnetic fields produced by the compensating objects to offset said perturbations.
- 7. The method as defined by claim 6 wherein the compensating objects are electromagnetic coils.
- 8. A combined modality imaging apparatus comprising:
a) first and second magnets which are axially aligned and spaced apart for creating a static magnetic field for magnetic resonance imaging, b) x-ray imaging apparatus provided between the first and second magnets, said apparatus containing components that cause perturbations in the static magnetic field, and c) at least one coil substantially adjacent to said components and energized to offset perturbations in the static magnetic field caused by the x-ray imaging apparatus.
- 9. The apparatus as defined by claim 8 wherein the x-ray apparatus includes an x-ray detector which causes the perturbations, the at least one coil being placed around the detector.
- 10. The apparatus as defined by claim 9 wherein two coils are placed on opposing sides of the object.
- 11. The apparatus as defined by claim 10 wherein two coils are positioned on opposing ends of the detector.
- 12. The apparatus as defined by claim 11 wherein the plurality of coils further includes a plurality of coplanar coils positioned adjacent to the bottom of the detector.
- 13. In a magnetic resonance imaging system including an object which perturbs the homogeneity of a static magnetic field of the system, apparatus for compensating for the perturbations comprising:
a) at least one magnetic coil positioned substantially adjacent to the object, and b) a current source for energizing the coil with current so that the coil creates magnetic fields which compensate for the perturbations outside of the object.
Government Interests
[0001] The U.S. government has rights in the disclosed invention pursuant to NIH contract no. RR09784 with Stanford University.