US 7,411,394 B2 · Method for imaging diffusion anisotropy and diffusion gradient simultaneously

Abstract

Inhomogeneous tissue structures cause spatial-varying water molecule diffusion that is characterized by the spatial derivative of diffusivity, i.e., diffusion gradient. In a magnetic resonance imaging (MRI) system, the effects of diffusion and diffusion gradient are simultaneously encoded in an echo signal using diffusion-encoding magnetic field gradient pulses. A method for imaging the diffusion gradient of water molecules in tissues and for delineating the interface between two tissues having different diffusion properties is disclosed. The method also describes imaging diffusion anisotropy and diffusion gradient simultaneously without any additional scans in comparison with diffusion tensor MRI.

Claims11

Dependent claims

A method for measuring intravoxel molecule diffusion gradient of spins in a specimen in a selected direction using an MRI system which comprises:

(a) utilizing diffusion-encoding magnetic gradient pulses in an MRI pulse sequence to encode diffusion into MR signals;
(b) applying diffusion-encoding gradient pulses in a selected direction to yield diffusion-weighted MR signals;
(c) applying no diffusion-encoding gradient pulses to yield MR signals without diffusion-weighting;
(d) demodulating the received MR signals to I and Q channel filtered signals;
(e) reconstructing I and Q images from the I and Q signals using a simple two-dimensional Fourier transformation;
(f) computing diffusion-weighted and diffusion-free phase images from their corresponding I and Q images;
(g) computing the phase difference between the diffusion-weighted phase image and the phase image without any diffusion-weighting;
and
(h) computing the intravoxel diffusion gradient along the direction of the diffusion-encoding gradient pulses from the phase difference with a display of images of the measured intravoxel molecule diffusion gradient in the MRI system.

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A method for measuring diffusion anisotropy and diffusion gradient simultaneously using an MRI system which provides a display of images of intravoxel molecule diffusion gradient which comprises:

(a) applying the diffusion-encoding gradient pulses in six non-collinear directions independently and separately to yield diffusion-weighted MR signals for the six directions;
(b) not applying any diffusion-encoding gradient pulses to yield MR signals without diffusion-weighting;
(c) demodulating the received MR signals to I and Q channel filtered signals;
(d) measuring the corresponding eddy current terms in the acquisition window for each of the six diffusion-encoding gradient pulses in (a);
(e) reconstructing I and Q images with eddy current correction from the I and Q signals using a simple two-dimensional Fourier transformation;
(f) computing six diffusion-weighted and one diffusion-free phase images from their corresponding I and Q images;
(g) computing the three components of diffusion gradient from the six diffusion-weighted phase images plus the phase image without diffusion-weighting;
(h) computing six diffusion-weighted and one diffusion-free intensity images from their corresponding I and Q images;
and
(i) computing the six components of diffusion tensor from the six diffusion-weighted intensity images plus the intensity image without diffusion-weighting.

7 more elements

Dependencies are inferred from the claim text.

Method for imaging diffusion anisotropy and diffusion gradient simultaneously

Life of this patent

Method for imaging diffusion anisotropy and diffusion gradient simultaneously

Life of this patent

Abstract

Claims11