AN IMPROVED METHOD FOR MRI DATA ACQUISITION AND IMAGE RECONSTRUCTION
Publication Date: 2004-Nov-10
The IP.com Prior Art Database
This invention relates generally to image data acquisition, and more particularly, to Magnetic Resonance Imaging (MRI) data acquisition using Cartesian or rectilinear k-space sampling and reconstruction using Sensitivity Encoding (SENSE) method.
FIELD OF THE INVENTION
 This invention relates generally to image data acquisition, and more particularly, to Magnetic Resonance Imaging (MRI) data acquisition using Cartesian or rectilinear k-space sampling and reconstruction using Sensitivity Encoding (SENSE) method.
BACKGROUND OF THE INVENTION
 Parallel imaging techniques generally reduce MRI data acquisition time by using an array of multiple surface coils for receiving the signal. Acquisition time is reduced by increasing the step size between phase encoding lines (FIG 1A and FIG 1B), or equivalently, by reducing the field of view (FOV). However, if the object extends outside the reduced FOV, aliasing (or wrapping) occurs in the phase encoding direction. Parallel imaging techniques remove such aliasing using spatial information contained in the surface coil B1 fields (also called sensitivities) to find the unaliased spin distribution.
 Over the years, several parallel imaging techniques have been developed, including SENSitivity Encoding (SENSE) and SiMultaneous Acquisition of Spatial Harmonics (SMASH). SENSE and SMASH remove aliasing in the image and k-space domains, respectively. Several variations of SMASH have also been developed, including Generalized Encoding Matrix (GEM), AUTO-SMASH, Variable Density (VD) AUTO-SMASH GeneRalized Auto calibrating Partially Parallel Acquisition (GRAPPA), and Generalized SMASH. Parallel Imaging with Localized Sensitivities (PILS) is a simple method that snips away part of the aliasing from each image and pastes together the remnants. Another parallel imaging technique called Sensitivity Profiles from an Array of Coils for Encoding and Reconstruction In Parallel (SPACE RIP) does not fall into either category of image space or k-space technique.
 However, there exists a need for an image acquisition method wherein aliasing can be removed much easily using an improved SENSE reconstruction algorithm.
BRIEF DESCRIPTION OF THE INVENTION
 In an embodiment, an improved method for MRI data acquisition and image reconstruction is provided. MRI data is acquired using Cartesian or rectilinear k-space sampling and reconstructed using the SENSE method. The method comprises using an improved SENSE reconstruction algorithm for the case where variable density (VD) k-space sampling is used. VD k-space sampling acquires ky lines more densely near the center of k-space where most of the signal energy is concentrated. The phase encoding step size is smaller near the center of k-space than near the edge. The VD sampling produces aliasing that is more widely separated in the image, which is then removed by SENSE processing.
BRIEF DESCRIPTION OF THE DRAWINGS
 FIG 1A shows a fully sampled k-space with 16 ky lines according to prior art.
 FIG. 1B shows a uniformly sampled k-space for parallel imaging with two fold acceleration (8 fina...