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Elastography: Imaging of Tissue Elastic Properties In-Vitro and In-Vivo

Elastography: Imaging of Tissue Elastic Properties In-Vitro and In-Vivo. J. Ophir, B. Garra*, F. Kallel, E.E. Konofagou, R. Righetti** and T. Varghese The University of Texas Medical School, Houston, TX *The University of Vermont Medical Center, Burlington, VT

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Elastography: Imaging of Tissue Elastic Properties In-Vitro and In-Vivo

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  1. Elastography: Imaging of Tissue Elastic Properties In-Vitro and In-Vivo J. Ophir, B. Garra*, F. Kallel, E.E. Konofagou, R. Righetti** and T. Varghese The University of Texas Medical School, Houston, TX *The University of Vermont Medical Center, Burlington, VT **The University of Florence, Italy Supported by National Cancer Institute (NCI) Program Project Grant P01-CA 64597

  2. Elastography • Definition • Motivation • Basic principles • Early experiments and images • Contemporary results • Future directions

  3. JO 6/97 DefinitionElastography:An imaging technique whereby local axial tissue strains are estimated from differentialultrasonic speckle displacements. These displacements are generated by a weak, quasi-static stress field.The resultant strain image is called anElastogram.

  4. Elastography • Definition • Motivation • Basic principles • Early experiments and images • Contemporary results • Future directions

  5. Motivation *Most pathological changes are associated with changes in tissue stiffness. *Palpation is an effective method for lesion detection and evaluation. *Many cancers (breast, prostate) are iso-echoic, and hence difficult to detect by ultrasound.

  6. Elastography • Definition • Motivation • Basic data and principles • Early experiments and images • Contemporary results • Future directions

  7. Basic data on breast tissues data courtesy of Dr. T. Krouskop, Baylor College of medicine JO 1/98

  8. Basic Principles: Normal strain

  9. One Dimensional Uniform Spring System

  10. Strain Profile in Uniform Spring strain Depth

  11. One Dimensional Non-Uniform Spring System

  12. Strain Profile in Non-uniform Spring strain Depth

  13. Basic Principles: Tissue Compression ModelTwo-dimensional representation/ perfect-slip conditions After compression Before compression 5/98

  14. Elastography data acquisition system

  15. ESTIMATION OF STRAIN ESTIMATION OF STRESS Theoretical Stress Distribution Applied Stress Post-compression RF A-lines Pre-compression RF A-lines Local Cross Correlation Analysis Absolute Axial Stress Estimation ELASTOGRAM Basic Principles: The Elastography Process

  16. RF signal compression: 2% applied strain precomp postcomp Notice that a small compression (strain) of the tissue results in a small compression of the signal (similar to frequency modulation)

  17. Basic Principles: Estimation of Strain Pre-compression RF line (T) del(t) Post-compression RF line Strain=del(t)/ (T) Strain=del(t)/(T)

  18. Elastography • Definition • Motivation • Basic principles • Early experiments and images • Contemporary results • Future directions

  19. Layered foam phantom (ca.1991) photograph sonogram elastogram

  20. sonogram photograph elastogram II elastogram I Sponge w/ diagonal cut (ca. 1991)

  21. Breast carcinoma in vitro (ca. 1992)sonogram elastogram

  22. Breast Carcinoma in-vivo (ca. 1993)

  23. Elastography • Definition • Motivation • Basic principles • Early experiments and images • Contemporary results • Future directions

  24. Elastogram from an ovine kidney Sonogram Elastogram Photograph

  25. Ovine Kidneys in-vitro (1997)Two longitudinal elastographic views at 5 MHz 4/98

  26. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL July 1998 Volume 45 Number 4 ITUCER (ISSN 0885-3010)

  27. Canine prostate in-vitro (1998)Transverse slice Elastogram Photograph Sonogram 9/98

  28. MRI, Elastogram, Sonogram and PathologyImages from a Canine Prostate at 5 MHz(1999)

  29. 1 cm Canine Prostate in vitro @ 5 MHz Trans. Long.

  30. Infiltrating Ductal Carcinoma of the Breastsonogram (1996) elastogram

  31. Invasive Ductal Carcinoma (1996) Sonogram Elastogram 1996

  32. Multifocal Breast Cancer in-vivo (1998) Sonogram Elastogram 2/98

  33. Infiltrating Ductal Carcinoma of the BreastIn Vivo at 5 MHz (1999)

  34. Sonograms Elastograms Breast tumors in-vivo (1999) Fibroadenoma Infil. Duct. Carcinoma

  35. HIFU lesion in Canine Liver elastogram T2 MRI Sonogram Pathology

  36. Elastography • Definition • Motivation • Basic principles • Early experiments and images • Contemporary results • Future directions

  37. Conclusions and Future Directions • Elastography conveys new and probably clinically important tissue information; • The tradeoffs among engineering/elastographic image parameters are now reasonably well understood; • Elastography can operate in hypoechoic areas (ex. shadows); • Reliable small elastic contrast exists among normal soft-tissue components; good CNR allows its visualization; • Pathology generally exhibits large elastic contrast; • Promising areas include breast, prostate, vasculature, small parts and treatment monitoring.

  38. Elastography: Block Diagram JO 6/98

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