Evaluating disease progression using magnetic resonance imaging

Abstract

An orthopedic magnetic resonance imaging system is disclosed. This system includes a source of magnetic resonance imaging data sets resulting from successive magnetic resonance imaging acquisitions from a diseased joint of a patient. A segmentation module segments surfaces in the joint based on information contained within at least one of the data sets, and a registration module spatially registers, in three dimensions, information represented by a first of the data sets with respect to information represented by one or more further data sets for the same patient. A comparison module detects differences between information represented by the data sets caused by progression of the disease in the joint of the patient between acquisitions. A cross-patient comparison module can compare detected differences for the patient with detected differences for at least one other patient.

1 . An orthopedic magnetic resonance imaging system, comprising: 
 a source of magnetic resonance imaging data sets resulting from successive magnetic resonance imaging acquisitions from a diseased joint of a patient,    a segmentation module responsive to the source of magnetic resonance imaging data sets and operative to segment surfaces in the joint based on information contained within at least one of the data sets,    a registration module responsive to the source of magnetic resonance imaging data sets and operative to spatially register, in three dimensions, information represented by a first of the data sets with respect to information represented by one or more further data sets for the same patient, and    a comparison module responsive to the registration module and operative to detect differences between information represented by the data sets caused by progression of the disease in the joint of the patient between acquisitions.    
     
     
         2 . The apparatus of  claim 1  wherein the segmentation module employs global constraints for at least a subset of the magnetic resonance imaging data.  
     
     
         3 . The apparatus of  claim 1  wherein the segmentation module is operative to perform low-pass filtering of at least some of the magnetic resonance imaging data.  
     
     
         4 . The apparatus of  claim 1  wherein the segmentation module is operative to perform segmentation operations in slices in which a plurality of separate anatomical features are present.  
     
     
         5 . The apparatus of  claim 1  wherein the segmentation module is operative to perform segmentation operations for diseased cartilage.  
     
     
         6 . The apparatus of  claim 1  wherein the registration module is a bone registration module.  
     
     
         7 . The apparatus of  claim 1  wherein the comparison module is operative to compare data for two joint surfaces that bear against each other.  
     
     
         8 . The apparatus of  claim 1  wherein the comparison module is operative to compare data for images of the femur.  
     
     
         9 . The apparatus of  claim 1  wherein the segmentation module, the registration module and the comparison module together are operative to detect statistically significant cartilage volume losses within six months.  
     
     
         10 . The apparatus of  claim 1  further including result storage responsive to the comparison module for storing results from the comparison module.  
     
     
         11 . A method of monitoring disease progression in a joint, comprising: 
 obtaining successive images of a same joint for each of a plurality of patients, wherein at least some of the joints are diseased,    segmenting joint surfaces within at least one of the images for each patient,    for each of the patients, spatially registering joint features for one of the successive images with another of the successive images,    detecting differences between the registered successive images for each of the individual patients,    comparing the differences obtained for different ones of the patients, and    storing results of the step of detecting.    
     
     
         12 . The method of  claim 11  wherein the step of storing stores the results in a high capacity storage medium.  
     
     
         13 . The method of  claim 11  wherein the step of storing stores the results in a database.  
     
     
         14 . A method of monitoring a joint, comprising: 
 obtaining image data for a joint of a first patient,    segmenting joint surfaces within the image data for the first patient,    obtaining data from results of a step of segmenting for at least one image of a joint for at least one patient different from the first patient, and    detecting differences between results of the step of segmenting joint surfaces within the image for the first patient and the data from the at least one different patient.    
     
     
         15 . The method of  claim 14  further including the step of storing results of the step of detecting.  
     
     
         16 . The method of  claim 15  wherein the step of storing stores the results in a high capacity storage medium.  
     
     
         17 . The method of  claim 15  wherein the step of storing stores the results in a database.  
     
     
         18 . The method of  claim 14  wherein the step of segmenting segments an outline of a boundary between two anatomical features of the joint of the patient in three dimensions by detecting an outline in each of a plurality of at least generally parallel planes, wherein the outline in at least some of the planes is based on data from at least one other of the planes.  
     
     
         19 . The method of  claim 14  further including fitting a biparametric surface to a three-dimensional anatomical feature described by the data for the patient, and projecting at least a portion of the data representing the three-dimensional anatomical feature onto the biparametric surface.  
     
     
         20 . The method of  claim 14  wherein the data from results of a step of segmenting is derived from a step of comparing segmented image data with volumetric image data.  
     
     
         21 . The method of  claim 14  wherein the step of obtaining includes performing a magnetic resonance imaging acquisition and further including the step of immobilizing the joint with the joint at a predetermined flexion angle during the step of performing a magnetic resonance imaging acquisition.  
     
     
         22 . The method of  claim 14  wherein the step of obtaining includes performing a magnetic resonance imaging acquisition and further including the step of completely immobilizing the joint with the joint at a predetermined three-dimensional position during the step of performing a magnetic resonance imaging acquisition.  
     
     
         23 . The method of  claim 22  wherein the step of immobilizing is operative to repeatedly immobilize the joint at predetermined three-dimensional positions that fall within a range of less than 7 millimeters along the longitudinal axis of the magnetic resonance imaging system used to perform the magnetic resonance imaging acquisition.  
     
     
         24 . The method of  claim 22  wherein the step of immobilizing is operative to repeatedly immobilize the joint at predetermined three-dimensional positions that fall within a range of less than 17 millimeters along the longitudinal axis of the magnetic resonance imaging system used to perform the magnetic resonance imaging acquisition.  
     
     
         25 . The method of  claim 14  wherein the step of obtaining includes performing a magnetic resonance imaging acquisition, further including the step of positioning one or more markers proximate the joint during the magnetic resonance imaging, and further including the step of evaluating image distortion for the joint based on acquired image data for the markers.  
     
     
         26 . The method of  claim 14  wherein the step of obtaining includes performing a magnetic resonance imaging acquisition, further including the step of positioning one or more markers proximate the joint during the magnetic resonance imaging, and further including the step of evaluating patient movement artifact for the joint based on acquired image data for the marker.  
     
     
         27 . The method of  claim 26  wherein the step of positioning positions a pair of cylinders in orthogonal locations proximate the joint.  
     
     
         28 . The method of  claim 14  wherein the step of detecting differences is operative to detect differences between information represented by the data within one or more sub-regions of a surface of the joint.  
     
     
         29 . The method of  claim 28  wherein the sub-regions are based on polar coordinates.  
     
     
         30 . The method of  claim 28  wherein the sub-regions are based on Cartesian coordinates.  
     
     
         31 . An orthopedic imaging system, comprising: 
 at least one source of patient data including data resulting from image acquisition from at least one joint for each of a plurality of patients,    a segmentation module that is responsive to the at last one source of imaging data and is operative to detect a boundary between two anatomical features of the joint, and    a cross-patient comparison module responsive to the segmentation module and operative to compare data resulting from segmentation of data for one of the patients with data for another of the patients.    
     
     
         32 . The apparatus of  claim 31  further including result storage responsive to the comparison module for storing results from the comparison module.  
     
     
         33 . The apparatus of  claim 53  wherein the segmentation module is operative to detect a boundary between two anatomical features of the joint in three dimensions by detecting an outline in each of a plurality of at least generally parallel planes, wherein the outline in at least some of the planes is based on data from at least one other of the planes.  
     
     
         34 . The apparatus of  claim 31  further including a fitting module operative to fit a biparametric surface to a three-dimensional anatomical feature described by the data for the patient, and a projection module operative to project at least a portion of the data representing the three-dimensional anatomical feature onto the biparametric surface.  
     
     
         35 . The apparatus of  claim 34  wherein the surface is a biparametric surface having a three-dimensional topology.  
     
     
         36 . The apparatus of  claim 34  further including a display module responsive to the projection module to display the two dimensional surface on a planar display.  
     
     
         37 . The apparatus of  claim 34  wherein the anatomical feature includes at least the condyles of the femur and wherein the surface is a cylinder.  
     
     
         38 . The apparatus of  claim 34  wherein the anatomical feature includes at least the plateau regions of the tibia and wherein the surface is a plane.  
     
     
         39 . The apparatus of  claim 34  wherein the anatomical feature includes at least the posterior surface of the patella and wherein the surface is a plane.  
     
     
         40 . The apparatus of  claim 34  further including means for performing image manipulations on data representing the two dimensional surface.  
     
     
         41 . The apparatus of  claim 34  further including a repositioning module operative to user input to project the three-dimensional anatomical feature onto a further biparametric surface layers proximate the biparametric surface.  
     
     
         42 . The apparatus of  claim 31  wherein data for at least some of the patients is obtained from a comparison module operative to compare boundary surface data resulting from segmentation for a first data set with volumetric data from a second data set.  
     
     
         43 . The apparatus of  claim 31  wherein the comparison module is operative to detect differences in cartilage thickness within the joint.  
     
     
         44 . The apparatus of  claim 31  wherein the comparison module is operative to detect differences in cartilage volume within the joint.  
     
     
         45 . The apparatus of  claim 31  wherein the comparison module is operative to detect differences in characteristics of cartilage material within the joint.  
     
     
         46 . The apparatus of  claim 45  wherein the differences in characteristics of cartilage material within the joint are reflected in differences in magnetic resonance signal from the cartilage material.  
     
     
         47 . The apparatus of  claim 31  wherein the segmentation module is an automatic segmentation module responsive to the patient data source and operative to automatically segment anatomical features in the patient with substantially only supervisory and artifact-correcting user input.  
     
     
         48 . The apparatus of  claim 31  wherein the patient data source is a source of magnetic resonance imaging data operative to provide data sets optimized for the detection of at least bone and cartilage.  
     
     
         49 . The apparatus of  claim 48  wherein the source of magnetic resonance imaging data includes a magnetic resonance imaging system operative to acquire the patient data using a sequence is less than about 30 minutes in duration.  
     
     
         50 . The apparatus of  claim 31  wherein the source of patient data is a source of magnetic resonance imaging data sets, which includes a magnetic resonance imaging system and a support assembly operative to immobilize the joint within the magnetic resonance imaging system with the joint at a predetermined three-dimensional position.  
     
     
         51 . The apparatus of  claim 50  wherein the source of patient data is a source of magnetic resonance imaging data sets, which includes a magnetic resonance imaging system that includes a knee coil and wherein the support assembly includes a heel constraint and at least two flexible wedges that are each operative to interact with a leg of the patient and the knee coil.  
     
     
         52 . The apparatus of  claim 51  wherein the support assembly is operative to repeatedly immobilize the joint at predetermined three-dimensional positions that fall within a range of less than 7 millimeters along the longitudinal axis of the magnetic resonance imaging system.  
     
     
         53 . The apparatus of  claim 51  wherein the support assembly is operative to repeatedly immobilize the joint at predetermined three-dimensional positions that fall within a range of less than 17 millimeters along the longitudinal axis of the magnetic resonance imaging system.  
     
     
         54 . The apparatus of  claim 31  further including a differential display module operative to generate a difference map depicting differences between the data for different patients.  
     
     
         55 . The apparatus of  claim 31  wherein the joint is a load-bearing joint, and wherein the patient data include imaging data for at least the majority of the load bearing surfaces of the joint.  
     
     
         56 . The apparatus of  claim 31  wherein the segmentation module employs an active contour algorithm.  
     
     
         57 . The apparatus of  claim 31  wherein the segmentation module employs a subpixel active contour algorithm.  
     
     
         58 . The apparatus of  claim 57  wherein the segmentation module employs an active contour algorithm configured to segment open contours with minimal operator intervention.  
     
     
         59 . The apparatus of  claim 57  wherein the segmentation module employs a three-dimensional gradient-driven active contour algorithm.  
     
     
         60 . The apparatus of  claim 31  wherein the cross-patient comparison module is operative to detect differences between information represented by the data within one or more sub-regions of a surface of the joint.  
     
     
         61 . The apparatus of  claim 60  wherein the sub-regions are based on polar coordinates.  
     
     
         62 . The apparatus of  claim 60  wherein the sub-regions are based on Cartesian coordinates.  
     
     
         63 . The apparatus of  claim 31  further including a multi-patient database and wherein the cross-patient comparison module includes a statistical analysis module.  
     
     
         64 . The apparatus of  claim 63  wherein the statistical analysis module is operative to derive statistical information about the joints of a number of patients.  
     
     
         65 . The apparatus of  claim 64  wherein the statistical analysis module is operative to derive statistical information about the progression of disease in the joints of a number of patients.  
     
     
         66 . A data memory, comprising result data resulting from steps of: 
 obtaining successive images of a same joint for each of a plurality of patients, wherein at least some of the joints are diseased,    segmenting joint surfaces within at least one of the images for each patient,    for each of the patients, spatially registering joint features for one of the successive images with another of the successive images,    detecting differences between the registered successive images for each of the individual patients, and    comparing the differences obtained for different ones of the patients.    
     
     
         67 . A data memory, comprising result data resulting from steps of: 
 obtaining image data for a joint of a first patient,    segmenting joint surfaces within the image data for the first patient,    obtaining data from results of a step of segmenting for at least one image of a joint for at least one patient different from the first patient, and    detecting differences between results of the step of segmenting joint surfaces within the image for the first patient and the data from the at least one different patient.    
     
     
         68 . An orthopedic magnetic resonance imaging system, comprising: 
 a source of magnetic resonance imaging data sets resulting from successive magnetic resonance imaging acquisitions from a diseased joint of a patient, wherein the source of image data provides image data that includes cartilage surface information and bone surface information, including bone surface information for a cartilage-bone interface,    a segmentation module responsive to the source of magnetic resonance imaging data sets and operative to segment surfaces in the joint based on information contained within at least one of the data sets,    a registration module responsive to the source of magnetic resonance imaging data sets and operative to spatially register, in three dimensions, the bone surface information represented by a first of the data sets with respect to the bone surface information represented by one or more further data sets for the same patient, and    a quantitative comparison module responsive to the registration module and operative to detect quantitative differences between information represented by the data sets caused by progression of the disease in the joint of the patient between acquisitions.