Evaluating disease progression using magnetic resonance imaging

Details Evaluating disease progression using magnetic resonance imaging Evaluating disease progression using magnetic resonance imaging

2000-11-01

2003-05-06

Walberg, Teresa (Department: 3742)

Surgery

Diagnostic testing

Detecting nuclear, electromagnetic, or ultrasonic radiation

C600S415000, C382S130000

Reexamination Certificate

active

06560476

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to methods and apparatus for tracking disease progression using magnetic resonance imaging, including methods and apparatus for efficiently and precisely tracking the progression of rheumatic diseases affecting cartilage.
BACKGROUND OF THE INVENTION
Osteoarthritis is a prevalent disease characterized mainly by cartilage degradation that is clinically reflected by a gradual development of joint pain, stiffness, and loss of motion. Osteoarthritis is extremely frequent in the general population, and it is estimated that its radiological prevalence is close to 50% overall. This figure is even higher in the elderly, with as much as 75% of the population between ages of 55 and 64 exhibiting some degree of radiological osteoarthritis in one or more joints. Although this disease is often benign, severe degenerative changes may cause serious disability.
Clinical osteoarthritis is now understood to be a complex interaction of degradation and repair of the cartilage, bone, and synovium, with secondary components of inflammation. The biochemical changes of osteoarthritis affect several cartilage components, including major matrix constituents, proteoglycans, and collagens. Decreased proteoglycan content in conjunction with damaged collagen structure leads to functional loss of normal matrix physiologic properties. Although the etiology of osteoarthritis is multiple and includes mechanical and biochemical factors, it appears that these culminate in an increased synthesis of proteolytic enzymes by the chondrocytes, which in turn leads to cartilage destruction.
There is no known cure for osteoarthritis, and current treatments are essentially limited to reliving the patient's symptoms. Research is under way, however, to find a therapeutic agent that will slow or stop the progression of the disease. One current approach to developing pharmacological treatments for osteoarthritis focuses on subchondral bone sclerosis, which is a well-recognized manifestation of osteoarthritis that could play a major role in the onset and/or progression of the disease.
Unfortunately, evaluating the efficacy of such agents is not an easy, straightforward process. For many years, studies of drug interventions on symptomatic knee osteoarthritis focused only on clinical parameters like pain and joint function, without assessing the anatomical impact of the disease (i.e., cartilage degradation and bone sclerosis). Simple radiographs are now often used in clinical trials for osteoarthritis to establish inclusion criteria, but such trials have not employed them to assess disease progression. More complex radiographic methods have also been proposed for measuring joint space width, such as the Buckland-Wight method, which may be used in clinical trials. Arthroscopy appears reliable and sensitive to changes, but it only allows for evaluation of the cartilage surface. It also appears to be somewhat subjective even when independently trained evaluators review video recordings of the procedures, and, above all, it is invasive.
A number of academic researchers have evaluated the use of Magnetic Resonance Imaging (MRI) for orthopedic investigations over the last ten years. Some researchers have proposed using MRI to reproducibly quantify articular dimensions to follow disease progression, and thereby assess whether proposed treatments may be responsible for changing the rate of cartilage loss. But the actual application of these proposed systems to the complex problem of making meaningful measurements on acutal diseased joints has not been shown to be entirely successful. This may be due to one or more of a variety of shortcomings, including extensive manual treatment and interpretation of data, excessive reliance on subjective human judgment, insufficient accuracy or repeatability to achieve meaningful results when used on actual diseased joints, inability to distinguish secondary symptoms, and/or excessively long scan times.
SUMMARY OF THE INVENTION
Several aspects of the invention are presented in this application. These relate to methods and apparatus for tracking disease progression using magnetic resonance
In one general aspect, the invention features an orthopedic magnetic resonance imaging system that includes a source of magnetic resonance imaging data sets
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resulting from successive magnetic resonance imaging acquisitions from a diseased joint of a patient. A segmentation module is 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
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is 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. A comparison module
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is 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.
In preferred embodiments, the comparison module can be operative to detect changes in cartilage thickness within the joint. The comparison module can be operative to detect changes in cartilage volume within the joint. The comparison module can be operative to detect changes in characteristics of cartilage material within the joint, which can be reflected in changes in magnetic resonance signal from the cartilage material. The system can further include a cross-patient comparison module
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responsive to the comparison module to compare detected differences for the patient with detected differences for at least one other patient. The system can further include a multi-patient database with the cross-patient comparison module including a statistical analysis module operative to derive statistical information about the progression of disease in the joints of a number of patients. The registration module can be operative to spatially register the data sets to within an average RMS value of about 50 microns, or even 10 microns. The registration module can include an automatic registration module operative to perform at least a three-dimensional preliminary spatial registration independent of user input. The registration module can be operative to perform the registration based on previously acquired magnetic resonance imaging data for the same patient. The segmentation module can be an automatic segmentation module responsive to the source of magnetic resonance imaging data sets and operative to automatically segment anatomical features in the patient with substantially only supervisory and artifact-correcting user input. The source of magnetic resonance imaging data can be operative to provide data sets optimized for the detection of at least bone and cartilage. The source of magnetic resonance imaging data can include a magnetic resonance imaging system operative to acquire the data sets using a sequence is less than about 30 minutes in duration. The source of magnetic resonance imaging data sets can include a magnetic resonance imaging system and a support assembly operative to immobilize the diseased joint within the magnetic resonance imaging system with the joint at a predetermined three-dimensional position. The magnetic resonance imaging system can include a knee coil with the support assembly including 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. The support assembly can be operative to repeatedly immobilize the joint at predetermined three-dimensional positions that fall within a range of less than 17 or even 7 millimeters along the longitudinal axis of the magnetic resonance imaging system. The system can further include a differential display module operative to generate a difference map depicting differences between the data sets detected by the comparison module. The joint can b

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