Moving table MRI with frequency-encoding in the z-direction
First Claim
1. A method of imaging large volumes without resulting slab-boundary artifacts, the method comprising:
- defining a desired FOV larger than an optimal imaging volume of an MR scanner in at least a first direction;
defining desired phase encode locations in at least one dimension perpendicular to the first direction;
choosing a plurality of slab thicknesses in the first direction wherein slab thickness varies with each phase encode location and is smaller than the desired FOV and within the optimal imaging volume of the MR scanner; and
continuously moving one of the optimal imaging volume and an imaging object in the first direction while repeatedly exciting and encoding spins with readout in the first direction to acquire data that is restricted to a slab thickness for a set of phase encode locations until a set of MR data for the FOV for the first set of phase encode locations is acquired;
reversing the direction of motion of one of the optimal imaging volume and the imaging object in the first direction;
continuously moving one of the optimal imaging volume and the imaging object in the a reversed direction while repeatedly exciting and encoding spins with readout in the first direction to acquire data that is restricted to the slab thickness for a second set of phase encode locations until a set of MR data for the FOV for the second set of phase encode locations is acquired; and
reconstructing at least one image of the FOV from the set of MR data for the first set of phase encode locations and the set of MR data for the second set of phase encode locations.
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Accused Products
Abstract
A system and method are disclosed using continuous table motion while acquiring data to reconstruct MR images across a large FOV without significant slab-boundary artifacts that reduces acquisition time. At each table position, full z-encoding data are acquired for a subset of the transverse k-space data. The table is moved through a number of positions over the desired FOV and MR data are acquired over the plurality of table positions. Since full z-data are acquired for each slab, the data can be Fourier transformed in z, interpolated, sorted, and aligned to match anatomic z locations. The fully sampled and aligned data is then Fourier transformed in remaining dimension(s) to reconstruct the final image that is free of slab-boundary artifacts.
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Citations
41 Claims
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1. A method of imaging large volumes without resulting slab-boundary artifacts, the method comprising:
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defining a desired FOV larger than an optimal imaging volume of an MR scanner in at least a first direction;
defining desired phase encode locations in at least one dimension perpendicular to the first direction;
choosing a plurality of slab thicknesses in the first direction wherein slab thickness varies with each phase encode location and is smaller than the desired FOV and within the optimal imaging volume of the MR scanner; and
continuously moving one of the optimal imaging volume and an imaging object in the first direction while repeatedly exciting and encoding spins with readout in the first direction to acquire data that is restricted to a slab thickness for a set of phase encode locations until a set of MR data for the FOV for the first set of phase encode locations is acquired;
reversing the direction of motion of one of the optimal imaging volume and the imaging object in the first direction;
continuously moving one of the optimal imaging volume and the imaging object in the a reversed direction while repeatedly exciting and encoding spins with readout in the first direction to acquire data that is restricted to the slab thickness for a second set of phase encode locations until a set of MR data for the FOV for the second set of phase encode locations is acquired; and
reconstructing at least one image of the FOV from the set of MR data for the first set of phase encode locations and the set of MR data for the second set of phase encode locations. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of imaging large volumes without resulting slab-boundary artifacts, the method comprising:
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defining a desired FOV larger than an optimal imaging volume of an MR scanner in at least a first direction;
defining desired phase encode locations in at least one dimension perpendicular to the first direction;
enabling readout in the first direction;
choosing a plurality of slab thicknesses in the first direction wherein slab thickness varies with each phase encode location and is smaller than the desired FOV and within the optimal imaging volume of the MR scanner; and
continuously moving one of the optimal imaging volume and an imaging object in the first direction while repeatedly exciting and encoding spins with readout in the first direction to acquire MR data that is restricted to a chosen slab thickness for the phase encode location being encoded until at least one image of the FOV can be reconstructed by;
altering a phase of the acquired MR data to correct for motion;
Fourier transforming the MR data in the first direction;
gridding and transforming the MR data in at least one dimension perpendicular to the first direction; and
sorting and aligning the transformed data to match anatomical locations.
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16. A computer readable storage medium having stored thereon a computer program to control a medical imaging device and create large FOV images without boundary artifacts, the computer program having a set of instructions that when executed by a computer causes the computer to:
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define a desired FOV larger than an optimal imaging volume of an MR scanner in at least a first direction;
determine a slab in the first direction having a thickness that is smaller than the desired FOV and within the optimal imaging volume of the MR scanner;
define readout in a first direction;
select a set of phase encode locations to be proximate to a center of k-space in a transverse direction to the first direction and timing acquisition of the set of phase encode locations to capture optimal image contrast associated with passage of a bolus of extrinsic contrast agent; and
continuously move one of the optimal imaging volume and an imaging object in the first direction while repeatedly exciting and encoding spins with readout in the first direction to acquire data that is restricted to the slab until at least one image of the FOV can be reconstructed. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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24. An MRI apparatus, to acquire multiple sets of MR data with a moving table and reconstruct MR images without slab-boundary artifacts, the apparatus comprising:
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a magnetic resonance imaging (MRI) system having a plurality of gradient coils positioned about a bore of a magnet, and an RF transceiver system and an RF switch controlled by a pulse module to transmit RF signals to an RF coil assembly designed to acquire MR images;
a patient table movable fore and aft in the MRI system within the magnet bore; and
a computer programmed to;
receive input defining a desired FOV larger than an optimal imaging volume of the MRI system in at least a first direction;
define desired phase encode locations in at least one dimension perpendicular to the first direction;
divide desired phase encode locations into sets;
choose at least one slab thickness in the first direction wherein slab thickness is constant for each set of phase encode locations and is smaller than the desired FOV and within the optimal imaging volume of the MR scanner;
readout in the first direction;
continuously move one of the optimal imaging volume and an imaging object in the first direction while repeatedly exciting and encoding spins with readout in the first direction to acquire data restricted to the slab thickness for the defined phase encode locations until at least one image of the FOV can be reconstructed; and
correct for gradient non-linearities. - View Dependent Claims (25, 26, 27, 28, 29)
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30. A method of imaging large volumes without resulting slab-boundary artifacts, the method comprising:
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(A) defining a desired FOV larger than an optimal imaging volume of an MR scanner in at least a first direction;
(B) defining desired phase encode locations in at least one direction perpendicular to the first direction;
(C) dividing desired phase encode locations into sets;
(D) choosing at least one slab thickness in the first direction, wherein slab thickness is constant for each set of phase encode location and is smaller than the desired FOV and within the optimal imaging volume of the MR scanner;
(E) frequency encoding in the first direction;
(F) continuously moving one of optimal imaging volume and an imaging object in the first direction while repeatedly exciting and encoding spins with readout in the first direction to acquire data that is restricted to a slab thickness for a first set of phase encode locations until a set of MR data for the first set of phase encode locations is acquired for the entire FOV;
(G) reversing the direction of motion of one of the optimal imaging volume and the imaging object;
(H) continuously moving one of the optimal imaging volume and the imaging object in a reverse direction while repeatedly exciting and encoding spins with readout in the first direction to acquire data that is restricted to the slab thickness for a next set of phase encode locations until a set of MR data for the next set of phase encode locations is acquired; and
(I) reconstructing at least one image of the FOV from the acquired sets of MR data. - View Dependent Claims (31, 32, 33, 34, 35)
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36. An controller for imaging large volumes without resulting slab-boundary artifacts, the controller having a set of instructions that causes the controller to:
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define a desired FOV larger than an optimal imaging volume of an MR scanner in at least a first direction, the desired FOV having a number of sets of phase encode locations;
choose at least one slab thickness in the first direction wherein the at least one slab thickness is constant for each set of phase encode locations and is smaller than the desired FOV and within the optimal imaging volume of the MR scanner;
frequency encode in the first direction;
translate one of the optimal imaging volume and an imaging object in the first direction while repeatedly exciting and encoding spins with a first combination of exciting and encoding waveforms and with readout in the first direction to acquire MR data that is restricted to a slab thickness of a phase encode location; and
interleave a pre-defined temporal frequency between the first combination of exciting and encoding waveforms with another combination of RF and gradient waveforms configured to excite and encode spins outside the slab thickness-until at least one image of the FOV can be reconstructed. - View Dependent Claims (37, 38)
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39. A system for imaging large volumes without resulting slab-boundary artifacts, the system comprising:
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means for defining a desired FOV larger than an optimal imaging volume of an MR scanner in at least a first direction;
means for defining desired phase encode locations in at least one dimension perpendicular to the first direction;
means for dividing desired phase encode locations into sets;
means for defining readout in the first direction;
means for choosing at least one slab thickness in the first direction, wherein slab thickness is constant for each set of phase encode locations and is smaller than the desired FOV and within the optimal imaging volume of the MR scanner; and
means for continuously moving one of the optimal imaging volume and an imaging object in the first direction while repeatedly exciting and encoding spins with readout in the first direction to acquire multiple lines of MR data following each excitation until at least one image of the FOV can be reconstructed. - View Dependent Claims (40, 41)
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Specification