Abstract: A method for correcting diffusion-weighted echo-planar imaging data (DW-EPI) includes obtaining a first reference scan with no diffusion gradients applied, a second reference scan with a diffusion gradient applied only along a frequency direction, a third reference scan with the diffusion gradient applied only along a phase direction, and a fourth reference scan with the diffusion gradient applied only along a slice direction acquired utilizing an MRI scanner, wherein the reference scans lack phase encoding. The method includes obtaining DW-EPI data acquired utilizing the MRI scanner, wherein the DW-EPI data includes phase errors due to oscillatory eddy currents causing time-varying B0 shift. The method includes generating a phase correction factor based on the reference scans and correcting the phase errors due to the oscillatory eddy currents in the DW-EPI data independent of diffusion gradient direction utilizing the phase correction factor to generate corrected DW-EPI data.

Abstract: A magnetic resonance (MR) imaging method of correcting nonuniformity in diffusion-weighted (DW) MR images of a subject is provided. The method includes applying a DW pulse sequence along a plurality of diffusion directions with one or more numbers of excitations (NEX), and acquiring a plurality of DW MR images of the subject along the plurality of diffusion directions with the one or more NEX. The method also includes deriving a reference image and a base image based on the plurality of DW MR images, generating a nonuniformity factor image based on the reference image and the base image, and combining the plurality of DW MR images into a combined image. The method also includes correcting nonuniformity of the combined image using the nonuniformity factor image, and outputting the corrected image.

Abstract: A method for correcting diffusion-weighted echo-planar imaging data (DW-EPI) includes obtaining a first reference scan with no diffusion gradients applied, a second reference scan with a diffusion gradient applied only along a frequency direction, a third reference scan with the diffusion gradient applied only along a phase direction, and a fourth reference scan with the diffusion gradient applied only along a slice direction acquired utilizing an MRI scanner, wherein the reference scans lack phase encoding. The method includes obtaining DW-EPI data acquired utilizing the MRI scanner, wherein the DW-EPI data includes phase errors due to oscillatory eddy currents causing time-varying Bo shift. The method includes generating a phase correction factor based on the reference scans and correcting the phase errors due to the oscillatory eddy currents in the DW-EPI data independent of diffusion gradient direction utilizing the phase correction factor to generate corrected DW-EPI data.

Abstract: A magnetic resonance (MR) imaging method of correcting nonuniformity in diffusion-weighted (DW) MR images of a subject is provided. The method includes applying a DW pulse sequence along a plurality of diffusion directions with one or more numbers of excitations (NEX), and acquiring a plurality of DW MR images of the subject along the plurality of diffusion directions with the one or more NEX. The method also includes deriving a reference image and a base image based on the plurality of DW MR images, generating a nonuniformity factor image based on the reference image and the base image, and combining the plurality of DW MR images into a combined image. The method also includes correcting nonuniformity of the combined image using the nonuniformity factor image, and outputting the corrected image.

Abstract: Methods and systems for performing magnetic resonance diffusion weighted imaging of an object is provided. The method includes applying a plurality of diffusion gradients to a plurality of image slices of the object during a plurality of repetition times via an MRI system. A different diffusion gradient of the plurality is applied to each image slice during the same repetition time.

Abstract: Methods and systems are provided for hybrid slice encoding. In one embodiment, a method for magnetic resonance imaging comprises, during a scan with a pulse sequence, sampling k-space linearly for a predetermined number of echoes, and sampling k-space centrically for remaining echoes of the pulse sequence. In this way, blurriness along the slice direction may be reduced for 3D fast spin echo imaging.

Abstract: Various methods and systems are provided for ghost artifact reduction in magnetic resonance imaging (MRI). In one embodiment, a method for an MRI system comprises acquiring a non-phase-encoded reference dataset, calculating phase corrections for spatial orders higher than first order from the non-phase-encoded reference dataset, acquiring a phase-encoded k-space dataset, correcting the phase-encoded k-space dataset with the phase corrections, and reconstructing an image from the corrected phase-encoded k-space dataset. In this way, ghost artifacts caused by phase errors during EPI may be substantially reduced, thereby improving image quality especially when imaging with a large field of view.

Abstract: Methods and systems are provided for hybrid slice encoding. In one embodiment, a method for magnetic resonance imaging comprises, during a scan with a pulse sequence, sampling k-space linearly for a predetermined number of echoes, and sampling k-space centrically for remaining echoes of the pulse sequence. In this way, blurriness along the slice direction may be reduced for 3D fast spin echo imaging.

Abstract: Various methods and systems are provided for ghost artifact reduction in magnetic resonance imaging (MRI). In one embodiment, a method for an MRI system comprises acquiring a non-phase-encoded reference dataset, calculating phase corrections for spatial orders higher than first order from the non-phase-encoded reference dataset, acquiring a phase-encoded k-space dataset, correcting the phase-encoded k-space dataset with the phase corrections, and reconstructing an image from the corrected phase-encoded k-space dataset. In this way, ghost artifacts caused by phase errors during EPI may be substantially reduced, thereby improving image quality especially when imaging with a large field of view.

Abstract: Methods and systems for performing magnetic resonance diffusion weighted imaging of an object is provided. The method includes applying a plurality of diffusion gradients to a plurality of image slices of the object during a plurality of repetition times via an MRI system. A different diffusion gradient of the plurality is applied to each image slice during the same repetition time.

Abstract: A magnetic resonance imaging apparatus that carries out a pulse sequence for making a signal of a first substance within an object smaller than a signal of a second substance within the object. The pulse sequence includes an ?°-pulse for exciting the object, a refocus pulse for refocusing a phase of spin within a region excited by the ?°-pulse, and a readout gradient field for acquiring a magnetic resonance signal from the region. The ?°-pulse has a spectral selectivity such that a transverse magnetization of the first substance is made smaller than a transverse magnetization of the second substance. The refocus pulse has a spectral selectivity such that a phase of spin of the second substance is refocused and refocusing of a phase of spin of the first substance is suppressed.

Abstract: Time course MRI data is acquired from the hippocampal region of the brain and processed to produce two indices that are a measure of the functional connectivity between locations therein. The MRI data is acquired while the brain is substantially at rest and the spontaneous low frequency component of the time course data at each location in the hippocampus is extracted and compared in a cross-correlation process. Also acquired is fMRI data which indicates those locations in the brain that should be included in the index calculations.

Abstract: Time course MRI data is acquired from the hippocampal region of the brain and processed to produce two indices that are a measure of the functional connectivity between locations therein. The MRI data is acquired while the brain is substantially at rest and the spontaneous low frequency component of the time course data at each location in the hippocampus is extracted and compared in a cross-correlation process. Also acquired is fMRI data which indicates those locations in the brain that should be included in the index calculations.