Ultrasound Imaging of Tissue Stiffness by Spatially Modulated Acoustic Radiation Force Impulse (SM-ARFI)

Tissue stiffness is a known marker of disease, but it is difficult to see in conventional imaging. Significant change in tissue stiffness can occur without a related change in ultrasound echogenicity or x-ray density.   Quantitative measurements of stiffness, in terms of the shear modulus, would be useful clinically in the diagnosis of liver fibrous, and for finding tumors the 40% of all prostrate tumors which are not visible in ordinary ultrasound, but which can be detected by palpation because of a tissue stiffness.
Acoustic radiation force impulse (ARFI) ultrasound is currently limited to “focal” disease states, in which there are well defined areas of modified stiffness; it cannot image disease states in which the stiffness increase is general and diffuse in the organ, but our spatially modulated ARFI can obtain a quantitative measure of stiffness in such an organ and provide an indication of the degree of disease.  Other applications include diffuse vascular diseases, which causes a systemic stiffness increase, which cannot be detected by current conventional acoustic radiation force impulse (ARFI) ultrasound, but could be detected with our spatially modulated ARFI technique. The technique could also be useful in RF ablation therapy for liver cancer, in which the progress of the therapy must now be checked by an off-line CT scan, but which could be monitored real-time with our SM-ARFI ultrasound.

Acoustic radiation force impulse (ARFI) ultrasound provides an indication of the local shear modulus of tissue, which is fast, has good penetration, works by local generation of shear wave which minimizes shear wave attenuation difficulties. but it is not quantitative.  This Spatially Modulated ARFI method provides a quantitative measurement, in addition to the other benefits of ARFI.   An alternative method, transient elastography is quantiative, but is noise sensitive. Sonoelastography is potentially quantitative, but it is difficult to propagate shear waves tgo the region of interest because of attentuation and refraction.  Vibroacoustaography can be quantitative but it is both very slow and sensitive to background noise.   A biopsy is quantitative and definitive but is not fast, is invasive, expensive and can be done only on a limited number of small samples.  Palpation is fast and inexpensive, but is not quantitative and can only be used in areas of limited pentetration.
URV Reference Number: 2-11149-07012
Patent Information:
Title Country Patent No. Issued Date
Shear Modulus Estimation by Application of Spatially Modulated Impulse Acoustic Radiation Force Approximation United States 8,225,666 7/24/2012
Methods and Systems for Spatially Modulated Ultrasound Radiation Force Imaging United States 8,753,277 6/17/2014
For Information, Contact:
McKenna Geiger
Licensing Manager
University of Rochester
Stephen Mcaleavey