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A GRAPHICAL METHOD FOR REAL-TIME NON-LINEARITY CORRECTION IN MEDICAL IMAGING

IP.com Disclosure Number: IPCOM000033828D
Publication Date: 2004-Dec-29
Document File: 8 page(s) / 130K

Publishing Venue

The IP.com Prior Art Database

Abstract

In an embodiment, a graphical method for real-time non-linearity correction in medical imaging includes inverting the spherical harmonic expansion of the magnetic field to determine a warped surface of gradient iso-contours, and translating the warped space into physical space through an orthographic projection.

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A GRAPHICAL METHOD FOR REAL-TIME NON-LINEARITY CORRECTION IN MEDICAL IMAGING

FIELD OF THE INVENION

[0001]   This invention relates generally to non-linearity correction methods and more particularly, to a graphical method for non-linearity correction in real-time interventional procedures.

BACKGROUND OF THE INVENTION

[0002]    In general, applications requiring fast and accurate representations of location, such as real-time interventional procedures especially, cardiac procedures require real-time correction of gradient non-linearity. 

[0003]   Known methods correct for both spatial and intensity distortion of an object being imaged through post-processing routines that take a considerable time. Generally, spatial distortion is corrected by deriving the gradient error from an actual field map [1], which can be used to map the physical object to a warped gradient space. The correction enables calculating the physical image by determining the pixel intensity of each physical location from the corresponding warped image.  These values are calculated through interpolation since the signal does not usually lie on the pixel boundaries.  Voxel size is also affected by gradient non-linearity, so an intensity correction step is performed as well. 

[0004]   Thus, there exists a need for a real-time method for gradient non-linearity correction that reduces the number of corrective steps and also consumes less time.

                  BRIEF DESCRIPTION OF THE INVENTION

[0005]       In an embodiment, a graphical method for real-time non-linearity correction in medical imaging includes inverting the spherical harmonic expansion of the magnetic field to determine a warped surface of gradient iso-contours, and translating the warped space into physical space through an orthographic projection.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]    FIG. 1 shows an example of uncorrelated slices through a grid phantom.

[0007]    FIG. 2 shows an example of a curvature of a warped surface.

[0008]    FIG. 3 shows an example of an orientation of the 3D surfaces in orthographic projection.

[0009]    FIG. 4 shows an example of a display of a single phase of an in-vivo double-oblique cardiac acquisition.

DETAILED DESCRIPTION OF THE INVENTION

[0010]    Various embodiments of the present invention describe a graphical method for real-time non-linearity correction in medical imaging. 

[0011]   In general, an embodiment of this invention includes inverting the spherical harmonic expansion of the magnetic field to determine a warped surface of gradient iso-contours, and translating the warped space into physical space through an orthographic projection.

[0012]   In an embodiment, two coordinate systems are defined, namely (xp, yp, zp) as the physical magnet coordinate system and (xw, yw, zw) as the warped coordinate system.  The non-linearity of the gradients causes the distortion from (xp, yp, zp) to (xw, yw, zw). 

[0013]   For example, higher order polynomials may be used...