Error analysis and correction of MRI ADC measurements for gradient nonlinearity
AssigneeThe Regents of the University of Michigan
InventorsThomas L. Chenevert, Brian D. Ross, Dariya I. Malyarenko
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Abstract
Techniques for correcting gradient non-linearity bias in mean diffusivity measurements by MRI systems are shown and include minimal number of spatial correction terms to achieve sufficient error control using three orthogonal diffusion weighted imaging (DWI) gradients. The correction is based on rotation of system gradient nonlinearity tensor into a DWI gradient frame where spatial bias of b-matrix is described by its Euclidian norm. The techniques obviate time consuming multi-direction acquisition and noise-sensitive mathematical diagonalization of a full diffusion tensor for medium of arbitrary anisotropy.
Claims30
A method of correcting diffusivity measurements of a medium of arbitrary anisotropy, the method comprising;
- (a.). generating three-dimensional spatial correction maps for an arbitrary set of no more than three orthogonal diffusion gradient waveforms using gradient coil non-linearity characteristics of a magnetic resonance imaging (MRI) scanner,
- (b.). performing a diffusion weighted MRI scan of the medium using the selected arbitrary set of no more than three orthogonal diffusion gradient waveform at any nominal b-value, and acquiring diffusion weighted images (DWIs),
- (c.). applying the three-dimensional spatial correction maps to correct intensity of each pixel of the acquired DWIs to compensate for MRI scanner-specific gradient non-linearity bias in diffusion weighting gradients, and
- (d.). determining corrected diffusivity images for a mean diffusivity of the medium from the corrected DWIs and nominal b-values.
A method of correcting diffusivity measurements of a medium of arbitrary anisotropy, the diffusivity measurements taken by a magnetic resonance scanning system, the method comprising:
- obtaining a set of diffusion imaging gradient waveforms, wherein the set of diffusion imaging gradient waveforms describe orientations of diffusion weighted image (DWI) gradients as three-coordinate vectors in a gradient coil frame of reference;
- performing a diffusion weighted scan of the medium, using the scanning system and any three orthogonal diffusion imaging gradient waveforms, to obtain a diffusion weighted magnetic resonance image set of the medium;
- obtaining a spatial correction map for diffusion weighting of each of the any three diffusion imaging gradient waveforms;
- and
- applying the spatial correction maps to the diffusion weighted magnetic resonance image set to correct for spatially-dependent bias errors in diffusion weighting by correcting the intensity of each pixel in the diffusion weighted magnetic resonance image set.
A non-transitory computer-readable storage medium having stored thereon a set of instructions, executable by a processor, for correcting diffusivity measurements of a medium of arbitrary anisotropy taken by a magnetic resonance scanning system, the instructions comprising:
- a) instructions for obtaining a set of diffusion imaging gradient waveforms, wherein the set of diffusion imaging gradient waveforms describe orientations of diffusion weighted image (DWI) gradients as three-coordinate vectors in a gradient coil frame of reference;
- b) instructions for performing a diffusion weighted scan of the medium, using the scanning system and any three orthogonal diffusion imaging gradient waveforms, to obtain a diffusion weighted magnetic resonance image set of the medium;
- c) instructions for obtaining a spatial correction map for each of the any three diffusion imaging gradient waveforms;
- and
- d) instructions for applying the spatial correction maps to the diffusion weighted magnetic resonance image set to correct for spatially-dependent bias errors in image intensities induced by the incorrect diffusion weighting of the magnetic resonance image set.
A non-transitory computer-readable storage medium having stored thereon a set of instructions, executable by a processor, for correcting diffusivity measurements of a medium of arbitrary anisotropy, the instructions comprising:
- instructions for generating three-dimensional spatial correction maps for an arbitrary set of no more than three orthogonal diffusion gradient waveforms using gradient coil non-linearity characteristics of a magnetic resonance imaging (MRI) scanner;
- instructions for performing a diffusion weighted MRI scan of the medium using the selected arbitrary set of no more than three orthogonal diffusion gradient waveform at any nominal b-value, and acquiring diffusion weighted images (DWIs);
- instructions for applying the three-dimensional spatial correction maps to correct intensity of each pixel of the acquired DWIs to compensate for MRI scanner-specific gradient non-linearity bias in diffusion weighting;
- and
- instructions for determining corrected diffusivity images for a mean diffusivity of the medium from the corrected DWIs and nominal b-values.
Dependencies are inferred from the claim text.