Method and apparatus for anatomically tailored k-space sampling and recessed elliptical view ordering for bolus-enhanced 3D MR angiography

A method of increasing the resolution of volumetric MR imaging of arteries or other structures comprising the following:

• a) an image volume having x, y and z orthogonal coordinates and a thickness along z=Tv
• b) for every x, y location within the volume the structures to be imaged have a thickness Ts<Tv
• c) increase the maximum spatial frequency sampled by a factor F≦Tv/Ts by increasing the spacing of k space sampling along kz by a factor of F while maintaining the same total acquisition time
• d) reconstruct with 3-D Fourier Transformation utilizing a field of view in the z direction which is equal to Tv/F
• e) create 1/F duplicate copies of the reconstructed volumetric data and stacked together adjacent to each other in the z direction
• f) post-process the combined multiple copies of volumetric data to select a subset of the total combined volume containing a single complete data set of the structures of interest.

A method of MR imaging a region of interest comprising:

• administering a contrast agent to the region of interest;
• applying a static magnetic field to the region of interest;
• applying a magnetic gradient along at least one of first and second dimensions to produce a distributed magnetic response having a spatial distribution in k-space;
• sampling the magnetic response, wherein sampling is performed such that sampling of a center of the k-space is delayed from a start of sampling of the magnetic response, such that sampling of the center of the k-space is timed to coincide with a substantial peak of the contrast agent passing through the region of interest;
• wherein the sampling of the k-space center is preceded by sampling of a recessed-edge of k-space;
• wherein the sampling of k-space center is followed by sampling of an edge of k-space substantially corresponding to a maximum spatial frequency of the magnetic response in said region of interest;
• wherein a first time interval separates sampling of the k-space center and the recessed edge of the k-space and a second time interval separates sampling of k-space center and the edge of the k-space, wherein during the first time interval, sampling occurs in decreasing order of k-space radius from the recessed edge to the k-space center while sampling every Mth point (M>1), and wherein during the second time interval, sampling occurs in increasing order of k-space radius to sample each k-space point not sampled during the first time interval.

A method of MR imaging a region of interest comprising:

• administering a contrast agent to the region of interest;
• applying a static magnetic field to the region of interest;
• applying a magnetic gradient along at least one of first and second dimensions to produce a distributed magnetic response having a spatial distribution in k-space;
• sampling the magnetic response, wherein sampling is performed such that sampling of a center of the k-space is delayed from a start of sampling of the magnetic response, such that sampling of the center of the k-space is timed to coincide with a substantial peak of the contrast agent passing through the region of interest;
• wherein sampling the magnetic response produces N points, said method further comprising:
• forming an array [K] of said N points ordered in said array in order of ascending radius from the center of the k-space using index N;
• setting a recessed radius kR having a corresponding index NR−1 in said array to start said sampling;
• setting a recess time Trecess corresponding to a time between start of sampling and peak contrast agent in the region of interest;
• setting a sequence repetition time TR as a time to acquire one sample;
• wherein sampling order of the k-space prior to sampling of the k-space center is determined according to
• Index=NR−1−(NR/(Trecess/TR))*n for n, 0≦n<(Trecess/TR).

A method of MR imaging a region of interest comprising:

• a) administering a contrast agent to the region of interest;
• b) applying a static magnetic field to the region of interest;
• c) applying a magnetic gradient along at least one of first and second dimensions to produce a distributed magnetic response having a spatial distribution in k-space including a low spatial frequency, an intermediate spatial frequency and a high spatial frequency;
• d) sampling the magnetic response in order of the intermediate frequency, the low spatial frequency and the high spatial frequency, said high spatial frequency corresponding to a maximum radius value of the magnetic response in the k-space for said region of interest;
• wherein a first time interval separates sampling of the intermediate spatial frequency and the low spatial frequency, and a second time interval separates sampling of the low spatial frequency and the high spatial frequency, wherein during the first time interval, sampling occurs in decreasing order of spatial frequency from the intermediate spatial frequency to the low spatial frequency, sampling every Mth point (M>1), and wherein during the second time interval, sampling occurs in increasing order of spatial frequency to sample each point not sampled during the first time interval.

A method of MR imaging a region of interest comprising:

• a) administering a contrast agent to the region of interest;
• b) applying a static magnetic field to the region of interest;
• c) applying a magnetic gradient along at least one of first and second dimensions to produce a distributed magnetic response having a spatial distribution in k-space including a low spatial frequency, an intermediate spatial frequency and a high spatial frequency;
• d) sampling the magnetic response in order of the intermediate frequency, the low spatial frequency and the high spatial frequency, said high spatial frequency corresponding to a maximum radius value of the magnetic response in the k-space for said region of interest;
• wherein the sampling of the low spatial frequency substantially corresponds to a peak of the contrast agent passing through the region of interest.

A method of MR imaging a region of interest comprising:

• a) administering a contrast agent to the region of interest;
• b) applying a static magnetic field to the region of interest;
• c) applying a magnetic gradient along at least one of first and second dimensions to produce a distributed magnetic response having a spatial distribution in k-space including a low spatial frequency, an intermediate spatial frequency and a high spatial frequency;
• d) sampling the magnetic response in order of the intermediate frequency, the low spatial frequency and the high spatial frequency, said high spatial frequency corresponding to a maximum radius value of the magnetic response in the k-space for said region of interest;
• wherein sampling the magnetic response produces N points, said method further comprising:
• forming an array [K] of said N points ordered in said array in order of ascending radius from the center of the k-space using index N;
• setting a recessed radius kR having a corresponding index NR−1 in said array to start said sampling;
• setting a recess time Trecess corresponding to a time between start of sampling and peak contrast agent in the region of interest;
• setting a sequence repetition time TR as a time to acquire one sample;
• wherein sampling order of the k-space prior to sampling of the k-space center is determined according to
• Index=NR−1−(NR/(Trecess/TR))*n for n, 0≦n<(Trecess/TR).