Spatial intensity correction for RF shading non-uniformities in MRI
View Patent ↗An MRI MAP prescan data from a predetermined imaged patient volume is decomposed to produce a transmit RF field inhomogeneity map and a receive RF field inhomogeneity map for the imaged patient volume based on a three-dimensional geometrical model of the inhomogeneity maps. At least one of the transmit RF field inhomogeneity map and the receive RF field inhomogeneity map is used to generate intensity-corrected target MRI diagnostic scan image data representing the imaged patient volume.
1. A method for MRI comprising use of an MRI gantry and associated computers and hardware to:
acquire MRI MAP prescan data from a predetermined imaged patient volume;
decompose said acquired MAP prescan data to produce a transmit RF field inhomogeneity map and a receive RF field inhomogeneity map for said imaged patient volume based on a three-dimensional geometrical model of said inhomogeneity maps; and
use at least one of said transmit RF field inhomogeneity map and said receive RF field inhomogeneity map to generate intensity-corrected target MRI diagnostic scan image data representing said imaged patient volume.
2. The method of claim 1 , wherein said three-dimensional geometrical model is defined by a closed form mathematical function that has smoothly varying spatial dependence.
3. The method of claim 1 , wherein said geometrical model includes a plurality of variable geometric parameter values selected in an optimization process to fit in said predetermined imaged patient volume.
4. The method of claim 3 , wherein said geometric parameter values include parameters representing the center and/or characteristic widths in said predetermined imaged patient volume.
5. The method of claim 1 , wherein said geometrical model incorporates only smoothly varying spatial dependencies substantially conforming to a Gaussian shape.
6. The method of claim 1 , wherein said MRI gantry includes a static magnet producing a static magnetic field of 1.5 Tesla or greater.
7. The method of claim 1 , wherein said transmit RF field inhomogeneity map and said received RF field inhomogeneity map are constrained to have a predetermined functional interdependence.
8. The method of claim 7 , wherein said transmit RF field inhomogeneity map and said receive RF field inhomogeneity map are identical.
9. The method of claim 7 , wherein said transmit RF field inhomogeneity map and said receive RF field inhomogeneity map are mirrored symmetric copies of each other.
10. The method of claim 1 , wherein intensity corrections are limited to a lesser relative amount in spatial areas having relatively smaller signal-to-noise ratios such that local noise components are not substantially increased beyond a predetermined amount.
11. An MRI system comprising:
means for acquiring MRI MAP prescan data from a predetermined imaged patient volume;
means for decomposing said acquired MAP prescan data to produce a transmit RF field inhomogeneity map and a receive RF field inhomogeneity map for said imaged patient volume based on a three-dimensional geometrical model of said inhomogeneity maps; and
means for using at least one of said transmit RF field inhomogeneity map and said receive RF field inhomogeneity map to generate intensity-corrected target MRI diagnostic scan image data representing said imaged patient volume.
12. The MRI system of claim 11 , wherein said three-dimensional geometrical model is defined by a closed form mathematical function that has smoothly varying spatial dependence.
13. The MRI system of claim 11 , wherein said geometrical model includes a plurality of variable geometric parameter values selected in an optimization process to fit in said predetermined imaged patient volume.
14. The MRI system of claim 13 , wherein said geometric parameter values include parameters representing the center and/or characteristic widths in said predetermined imaged patient volume.
15. The MRI system of claim 11 , wherein said geometrical model incorporates only smoothly varying spatial dependencies substantially conforming to a Gaussian shape.
16. The MRI system of claim 11 , wherein said MRI gantry includes a static magnet producing a static magnetic field of 1.5 Tesla or greater.
17. The MRI system of claim 11 , wherein said transmit RF field inhomogeneity map and said received RF field inhomogeneity map are constrained to have a predetermined functional interdependence.
18. The MRI system of claim 17 , wherein said transmit RF field inhomogeneity map and said receive RF field inhomogeneity map are identical.
19. The MRI system of claim 17 , wherein said transmit RF field inhomogeneity map and said receive RF field inhomogeneity map are mirrored symmetric copies of each other.
20. The MRI system of claim 11 , wherein intensity corrections are limited to a lesser relative amount in spatial areas having relatively smaller signal-to-noise ratios such that local noise components are not substantially increased beyond a predetermined amount.