Methods and apparatus for phase correction in magnetic resonance imaging

摘要

Methods, apparatuses, systems, and software for extended phase correction in phase sensitive magnetic resonance imaging utilizing an optimized region-growing based phase correction algorithm. Phase correction is formulated as selecting a vector for each pixel of an image from two input candidate vectors so that the orientation of the output vector is spatially smooth. In certain embodiments, the optimized region growing algorithm uses automated quality guidance for determining the sequence of region growing and jointly considers the two input candidate vectors during region growing. Further, the algorithm tracks the quality and the mode at each step of the processing. Spatially isolated tissue regions are automatically segmented and processed with different threads of region growing and the correct vector is reliably identified as the output vector for each thread of region growing. Final phase correction was performed by pixel level optimization.

主权项

1. A computerized method for generating a phase corrected magnetic resonance image comprising:
(a) acquiring a first magnetic resonance image containing error and intrinsic phase information; (b) calculating two or more candidate input vector images from the acquired image; and (c) performing an optimized region growing based phase correction algorithm to determine an output vector image that is spatially smooth in orientation and is substantially represented at each pixel by one of the calculated vector images at the same pixel, wherein phase correction is performed by:
selecting an initial seed pixel for a new thread of region growing and placing the initial seed pixel onto a highest priority pixel stack;selecting a pixel that is placed on a pixel stack with a highest priority order from a list of pixel stacks that hold unprocessed pixels;determining an updated vector pair for the selected pixel by jointly considering its input vector pair (A and B) with a reference vector pair (Ar and Br);placing each of neighboring pixels of the selected pixel onto one of pixel stacks according to a quality metric by jointly comparing an input vector pair of a neighbor pixel with a reference vector pair;recording and monitoring the priority and the mode of region growing for the selected pixel;using the recorded mode of region growing to determine which vector pairs need to be considered and which vector of the updated vector pair is a correct vector; andperforming a final pixel-level optimization in which a vector O of a pixel is assigned as its original input vector A or B depending on if A or B has a smaller angular difference with the locally average O of the pixel over a selected boxcar.