Mri with static tissue removal

Abstract

A method of processing signals from an accelerated MRI scan of a dynamic event occurring in the body of a human patient. The patient is subjected to an MRI examination which includes the relevant portion of his body. Those voxels for which there is no substantially no change over the time of the scan are identified and subtracted from the overall scan signal.

What is claimed is: 
     
         1 . A method of processing signals from a magnetic resonance imaging scan of a dynamic event occurring in the body of a patient comprising;
 accessing original magnetic resonance imaging data of a relevant portion of a patient's body;   creating a subset of time spaced frames from the original magnetic resonance imaging data;   identifying static tissue voxels representing static tissue by comparing a change in each voxel signal between the subset of time spaced frames;   removing the signals of the static tissue voxels from the original magnetic resonance imaging data to create a modified magnetic resonance imaging data; and   reconstructing the modified magnetic resonance imaging data.   
     
     
         2 . The method of  claim 1  wherein identifying the static tissue voxels includes determining a threshold value of the difference between the voxel signals between the time spaced frames. 
     
     
         3 . The method of  claim 2  wherein the threshold value is automatically set at some level of variation above which there is a substantial increase in variation and this threshold is used to assign a weight to the examined voxels. 
     
     
         4 . The method of  claim 3 , wherein the threshold value is set at the maximum rate of curvature. 
     
     
         5 . The method of  claim 1  wherein removing the static voxel signals include subtracting the static voxel signals from the original MRI data. 
     
     
         6 . The method of  claim 1 , wherein reconstructing the modified magnetic resonance imaging data includes identifying a plurality of locations which do not encompass voxels associated with the dynamic event and the plurality of locations are excluded from the subsequent unaliasing reconstruction of an image from the voxels associated with the dynamic event. 
     
     
         7 . The method of  claim 1  wherein the data from a plurality of receiver channels which display low signal energy after the removal of the static tissue voxels is eliminated in the subsequent unaliasing reconstruction of an image from the receiver channels with significant signal energy that capture the voxels associated with the dynamic event. 
     
     
         8 . The method of  claim 2  further including creating a static tissue image by using the voxels for which there is substantially no change between the time spaced frames, the static tissue image is converted into k-space and subtracted from the k-space representation of the original MRI data and the residual k-space data is subject to unaliasing reconstruction. 
     
     
         9 . The method of  claim 6  further including combining the dynamic tissue image which is obtained from the unaliasing reconstruction of the residual k-space data with the static tissue image to yield a final image. 
     
     
         10 . The method of  claim 1  wherein at least two time spaced frames are used for the identification of which voxels for which there is substantially no change between the time spaced frames. 
     
     
         11 . The method of  claim 10  wherein the time spaced frames are approximately evenly temporally spaced. 
     
     
         12 . The method of  claim 11  wherein the dynamic event is the beating of the heart and the time spaced frames are spaced over one cardiac cycle. 
     
     
         13 . The method of  claim 1  wherein regions of clinical interest are identified by an image segmentation method and signals of the dynamic voxels outside of the regions of interest are removed from the original scan signals before unaliasing reconstruction. 
     
     
         14 . A method of processing signals from an accelerated MRI scan of a dynamic event occurring in the body of a human patient comprising;
 obtaining an MRI examination which includes a relevant portion of a patient;   identifying those voxels for which there is substantially no change over the time course of the scan; and   removing signals of those voxels from the original scan signal to improve image reconstruction in an accelerated MRI.   
     
     
         15 . The method of  claim 14  wherein those voxels which does not vary in signal with time are identified by a analyzing at least two time spaced frames of the MRI examination. 
     
     
         16 . The method of  claim 15  further including identifying those locations which do not encompass voxels associated with a dynamic event and such locations are excluded from the subsequent unaliasing reconstruction of an image from the voxels associated with the dynamic event. 
     
     
         17 . The method of  claim 14  wherein data from at least one receiver channels which display low signal energy after the step of subtracting is eliminated in the subsequent unaliasing reconstruction of an image from a plurality of receiver channels with significant signal energy that capture the voxels associated with the dynamic event. 
     
     
         18 . An apparatus for processing signals from an accelerated MRI scan of a dynamic event occurring in the body of a human patient who has had the relevant portion of his body subject to an MRI examination, comprising:
 a data processor configured to receive a scan signal from several different time windows and identify those voxels for which there is substantially no change over the time course of the scan and subtract signals of those voxels from the scan signals; and   subtract the signals of those voxels from the scan signal and create a modified scan data.   
     
     
         19 . The apparatus of  claim 18  wherein the data processor includes instructions to identify those locations which do not encompass voxels associated with the dynamic event and exclude such locations from the subsequent unaliasing reconstruction of an image from the voxels associated with the dynamic event. 
     
     
         20 . The apparatus of  claim 19  wherein the data processor eliminates the data from the receiver channels which display low signal energy after the subtraction from use in the subsequent unaliasing reconstruction of an image from the receiver channels with significant signal energy that capture the voxels associated with the dynamic event.