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PROPELLER BLADE RECENTERING SYSTEM FOR MAGNETIC RESONANCE IMAGING

IP.com Disclosure Number: IPCOM000033820D
Publication Date: 2004-Dec-29
Document File: 8 page(s) / 378K

Publishing Venue

The IP.com Prior Art Database

Abstract

In an embodiment, the system includes generating an N x N image from a predetermined number of blades having a predetermined echo train length (Netl). Then a k-space shift is estimated from a phase roll of the generated image, by Fast Fourier Transformation (FFT) of the center Netl × Netl data and by using Ahn method.

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PROPELLER BLADE RECENTERING SYSTEM FOR MAGNETIC RESONANCE IMAGING

FIELD OF THE INVENTION

[0001]   This invention relates generally to propeller blade recentering system, and more particularly, to propeller blade recentering system in a propeller magnetic resonance imaging (MRI) system.

BACKGROUND OF THE INVENTION

[0002]    Propeller MRI is a hybrid between projection acquisitions (PR) that sample MR data on a polar lattice and standard spin echo imaging, which acquires on a Cartesian lattice.  Like PR, propeller oversamples the center of k-space, which improves contrast over standard spin echo imaging, and permits extensive data corrections.  However, propeller demands data corrections, which are not required for standard Cartesian acquisitions, and permits other data corrections for patient motion and hardware imperfections. 

[0003]   Eddy currents can easily cause a linear shift in k-space readout points.  During a standard Cartesian acquisition, these shifts are correlated throughout the acquisition, resulting in a phase roll across the final image, which does not affect the displayed magnitude of image.  During propeller acquisition, these shifts are different for each blade, resulting in incoherent phase errors.  This effect must be accounted for, during reconstruction. 

[0004]   Standard Propeller reconstruction technique is known to recenter and refocus each blade using a method analogous to homodyne reconstruction.  However, this method is found to be slow and hence not much favourable.

[0005]   Thus, there exists a need for a system for quick recentering of propeller blades.  

SUMMARY OF THE INVENTION

[0006]    In an embodiment, the system includes generating an N x N image from a predetermined number of blades having a predetermined echo train length (Netl).   Then a k-space shift is estimated from a phase roll of the generated image, by Fast Fourier Transformation (FFT) of the center Netl × Netl data and Ahn method.

[0007]   In another embodiment, the system includes using standard refocusing technique to refocus as well as recenter the echo when the residuals of the Ahn phase estimate are large. 

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]    FIG. 1 shows a schematic diagram of an example of the blades with predetermined echotrain lengths.

[0009]    FIG. 2 shows a comparative diagram of an example of blade positioning according to one embodiment of the present invention.

[0010]    FIG. 3 shows a comparative example of real and imaginary parts of reconstructed image according to one embodiment of the present invention.

[0011]    FIG. 4 shows comparative diagrams of an example of real parts of reconstructed images and magnitude images.

DETAILED DESCRIPTION OF THE INVENTION

[0012]      Various embodiments of the present invention describe a propeller blade recentering system in an MRI.

[0013]    In one embodiment, the system includes generating an N x N image from a predetermined number of blades having an echo train length (Netl).   Th...