Magnetic resonance imaging in an inhomogeneous magnetic field
AssigneeGeneral Electric Company
InventorsJae K. Kim, Donald B. Plewes, Ross M. Henkelman
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Abstract
A method for MR imaging in an inhomogeneous magnetic field substantially without inhomogeneity induced artifacts is disclosed. The method includes acquiring more than one line of K-space per pulse sequence. The K-space data is acquired in partial line segments. The method allows shorter imaging times and higher image quality than conventional imaging methods for inhomogeneous fields.
Claims21
In an MR imaging system having an inhomogeneous magnetic field, a method for acquiring a K-space data set, having coordinates Kx, Ky and Kz, substantially without inhomogeneity induced artifacts, the method comprising:
- (a) applying an inhomogeneous magnetic field to a region of interest;
- (b) applying an RF excitation pulse to the region of interest to create a spin-state;
- (c) subsequently applying a predetermined sequence of RF refocusing pulses to repeatedly refocus the spin-state, allowing a data acquisition from a segment of a K-space line after each RF refocusing pulse, wherein each segment comprises more than one K-space data point and each data point is symmetrically arranged around a center of the refocused spin-state, such that the K-space line is acquired in a predetermined series of segments, wherein a complete set of segments is acquired from a predetermined number of K-space lines after applying the RF excitation pulse;
- and
- (d) repeating the initial RF excitation pulse and a corresponding predetermined sequence of RF refocusing pulses while varying the data acquisition along Kx and Ky to obtain a complete two-dimensional K-space data set.
In an MR imaging system having an inhomogeneous magnetic field, a method for acquiring a K-space data set, having coordinates Kx, Ky and Kz, substantially without artifacts, the method comprising:
- (a) applying an inhomogeneous magnetic field to a region of interest;
- (b) applying a 90.degree. RF excitation pulse to the region of interest to create a spin-state at an origin of K-space;
- (c) moving the spin-state to a predetermined starting position on a first K-space line;
- (d) applying a first 180.degree. RF refocusing pulse to move the spin-state through the origin of K-space and to refocus the spin-state at a conjugate position on a conjugate K-space line;
- (e) acquiring data from a segment of the conjugate K-space line while applying a first readout gradient to direct the data acquisition along Kx, wherein the segment comprises a plurality of data points such that the segment is symmetrically arranged around a center of the refocused spin-state;
- (f) applying a next 180.degree. RF refocusing pulse to move the spin-state through the origin of K-space and to refocus the spin-state at a conjugate position on the first K-space line, wherein a segment is acquired from the first K-space line while applying a second readout gradient opposite the first readout gradient, the segment comprising a plurality of data points such that the segment is symmetrically arranged around the center of a refocused spin-state;
- (g) subsequently applying a series of 180.degree. RF refocusing pulses to refocus the spin-state at corresponding conjugate positions along the first K-space line and the conjugate K-space line such that the first K-space line and the conjugate K-space line are partially acquired in segments;
- (h) repeating the pulse sequence as in steps (b) to (g), wherein the predetermined starting position is selected to be on the conjugate K-space line to acquire data from segments of the first K-space line and the conjugate K-space line not previously acquired such that a segment of the first K-space line will by acquired after the first 180.degree. RF refocusing pulse;
- and,
- (i) repeating steps (a) to (h) while varying the first K-space line along Ky to acquire a complete two-dimensional K-space data set.
Dependencies are inferred from the claim text.