Technologies Advancing the Field of Tissue Stiffness Measurement (Elastography)
T2012-069 An array of technologies advancing device design, analytic techniques and scope of application of magnetic resonance elastography (MRE)
Magnetic resonance elastography (MRE) combines MRI imaging with sound waves, creating a visual map showing and quantitating the stiffness of body tissue. MRE's initial application has been to the liver, where chronic diseases such as Non-Alcoholic Fatty Liver Disease (estimated background prevalence in U.S; 30%) and hepatitis C infection promote fibrosis and irreversible liver damage. The numerous advantages of MRE include the ability to assess the entire organ, unlike the limited number of points of a biopsy. Because of its accuracy, MRE has become the preferred modality, over ultrasound, for assessing liver stiffness/fibrosis. The growing clinical interest in MRE has created a demand for improvements in sound wave generation, more accurate data analysis techniques, and technologies to expand the use of MRE to other organs. For example, in the heart, it can be used to measure myocardial stiffness, where stiffness is known to change in disease states such as myocardial infarction and hypertrophic cardiomyopathy. At present, non-invasive methods for assessing such cardiac stiffness changes do not exist.
Researchers at The Ohio State University, led by Dr. Arun Kolipaka, Technical Director of MRI for the College of Medicine, have developed a series of inventions for creating more robust MRE 3D stiffness maps and enabling translation of MRE procedures beyond liver to smaller target organs including spleen, heart, aorta, pancreas and kidneys. Current acoustic drivers for MRE, pneumatically driven, are limited to low frequency vibrations (less than 100 Hz). The generated wavelengths are therefore longer than the dimensions of these smaller organs, disallowing stable stiffness mapping. The Kolipaka group's novel, hydraulically powered driver system enables frequencies of 400 Hz and greater with resulting shorter wavelengths. Along with novel inversion algorithms, this allows stable 3D stiffness maps for smaller organs. In addition, the system's higher power allows deeper penetration into organs and both longitudinal and shear vibrations. For target organs with high noise levels, such as heart, lung and breast, the accuracy of current inversion algorithms that process the wave images into stiffness maps is limited by this noise as well as complicated wave patterns. Kolipaka has enabled accurate stiffness estimation in the presence of noise by an unconstrained optimization process. Other advances in the field include combining MRE stiffness estimation with current MRI blood flow measurement techniques for more accurate diagnosis and treatment planning of aneurysms, such as an abdominal aortic aneurysm. The invention allows this assessment to be done, for the first time, in a single MRI session. The invention portfolio includes processing algorithms enabling elastography on CT systems, which to date has been considered a technical impossibility.
- Magnetic resonance elastography with new or existing MRI scanners (retrofittable)
- Earlier, more accurate diagnosis and treatment planning for diseases involving increased organ stiffness
- Enables accurate 3D stiffness mapping of organs smaller than liver (e.g prostate, pancreas, heart)
- Higher driver-generated force allows deeper penetration into organs
- Higher system power enables both longitudinal and shear vibrations
- Stable stiffness maps even in noisy organ environments