Method of enhancing the focus of magnetic resonance images
AssigneeThe Board of Trustees of the Leland Stanford Junior University
InventorsDouglas C. Noll, John M. Pauly, Albert Macovski
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Abstract
Disclosed is a method for automatically removing blur in magnetic resonance image signals introduced due to inhomogeneity in the magnetic field and variations in magnetic susceptibility of an object being imaged. Detected signals are demodulated at several different frequencies and reconstructed to create a series of base images. The amount of blur is determined by establishing a focusing measure for each point or part in each base image, and a composite image is then constructed using only the unblurred regions from each base image. Focusing criterion can include minimization of the imaginary part of the complex MRI after removal of constant and low frequency phase information.
Claims19
A method of enhancing the focus of a magnetic resonance image (MRI) of a body comprising:
- (a) placing a body in a magnetic field (B.sub.0),
- (b) applying a RF excitation pulse (B.sub.1) to said body,
- (c) detecting resultant signals from said body,
- (d) demodulating said resultant signals at a plurality of frequencies to obtain MRI signals I.sub.i (x,y),
- (e) applying a focusing criterion to said MRI signals to obtain focusing measures S.sub.i (x,y),
- (f) comparing said focusing measures for said MRI signals at said plurality of frequencies, and
- (g) selecting an MRI signal based on said focusing measures.
A method of enhancing the focus of a composite magnetic resonance image (MRI) of a body comprising:
- (a) detecting signals emitted from a plurality of parts in said composite MRI in response to magnetic stimulation, said signals having a Larmor frequency depending on the magnetic field through said parts and the magnetogyric ratio for nuclei in said parts,
- (b) selecting a plurality of frequencies for the Larmor frequency,
- (c) determining MRI signals for each of said plurality of frequencies in each part,
- (d) comparing said MRI signals from each part using a focusing criterion,
- (e) selecting an optimum MRI signal for each of said selected parts based on said focusing criterion, and
- (f) forming said composite MRI of said body based on the selected optimum MRI signals for said selected parts.
Apparatus for obtaining magnetic resonance image (MRI) signals for a body comprising:
- (a) means for generating a magnetic field (B.sub.0) through said body,
- (b) means for applying a RF pulse (B.sub.1) to said body,
- (c) means for detecting resultant signals from said body,
- (d) means for demodulating the detected signals at a plurality of frequencies to obtain MRI signals,
- (e) means for applying a focusing criterion to said MRI signals to obtain focusing measures S.sub.i (x,y),
- (f) means for comparing said focusing measures for said MRI signals at said plurality of frequencies, and
- (g) means for selecting an MRI signal based on said focusing measures.
Dependencies are inferred from the claim text.