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  • 1. ELASTICITY FOR ME
  • 2. THEY SPOILED MY CHILDHOOD..
  • 3. PHYSICS OF ELASTOGRAPHY  Elastography is a noninvasive technique of imaging stiffness or elasticity of tissues by measuring movement or transformation of tissue in response to a small applied pressure.  ‘VIRTUAL PALPATION’ which can overcome the subjectivity flaw and provide objective as well as quantitative measure of tissue stiffness.
  • 4. Going back to school days….  Stress: It is defined as force per unit area. Unit- Pascal.  Stress can due to: Compression-which acts Perpendicular to the surface and causes shortening of an object : Shear stress which acts parallel to the surface and causes deformation.
  • 5. DEFINITIONS…..(cont…)  Strain: When subjected to stress an object tends to undergo deformation of its original size and shape; the amount of deformation is known as strain. Unit less-expressed as change in length per unit length of the object.  Elasticity: It is the property of the materials to return back to its original form after stress is removed.
  • 6. The Basics of Human Tissue Elasticity  Tissue stiffness is generally measured by a physical quantity called Young’s modulus and expressed in pressure units - Pascals or kilo Pascals (kPa).  The Young’s modulus is defined simply as the ratio between the applied stress and the induced strain.  Young’s modulus, or elasticity E, quantifies tissue stiffness. Hard tissues have a higher Young’s modulus than soft ones.
  • 7. TYPE OF SOFT TISSUE YOUNG’S MODULUS –(E = s (in kPa) e) 18-24 28-66 FIBROUS TISSUE 96-244 CARCINOMA PROSTATE NORMAL FAT NORMAL GLANDULAR BREAST 22-560 NORMAL 55-71 BPH 36-41 CARCINOMA LIVER 96-241 NORMAL 0.4-6 CIRRHOSIS 15-100
  • 8. HOW EXACTLY DOES THIS CRAP WORK?? Three step methodology: 1. Generate a low frequency vibration in tissue to induce shear stress 2. Image the tissue with the goal of analyzing the resulting stress 3. Deduce from this analysis a parameter related to tissue stiffness  If the Young’s modulus, or elasticity of the tissue, can be determined directly from the analysis, the technique is considered quantitative.
  • 9. TYPES OF ELASTOGRAPHY  Elastography techniques are commonly classified according to the type of vibration applied to the tissue. There are three classes of Elastography :  Static  Dynamic and  Shear wave based
  • 10. STATIC ELASTOGRAPHY  Static elastography uses a uniform compression at the surface of the body to cause deformation of the tissue.  The compression is applied by the user and the ultrasound scanner calculates and displays the induced deformation in the imaging plane.  Young’s modulus cannot be reconstructed as the stress within the tissues induced is unknown.
  • 11. STRESS Static Elastography. Bmode (left) and elastogram (right). On the elastogram, less deformed tissue appears darker
  • 12. DYNAMIC ELASTOGRAPHY  Dynamic elastography utilizes a continuous (monochromatic) vibration.  Stationary waves induced in the body are analyzed to deduce tissue elasticity.  Dynamic elastography is well suited for MR systems as the vibration pattern is not time dependent but must be assessed in a volume.  It is a quantitative approach but suffers from the usual MR drawbacks: high cost, limited availability, and lack of real time imaging.
  • 13. Dynamic elastography images from MRI .Displacements @ 50Hz . Elasticity map (bottom right).
  • 14. SHEAR WAVE ELASTOGRAPHY  Shear wave based elastography makes use of transient pulses to generate shear waves in the body.  The tissue’s elasticity is directly deduced by measuring the speed of wave propagation.  Shear wave based elastography is the only approach able to provide quantitative and local elastic information in real time
  • 15.  Shear Wave Elastography uses the acoustic radiation force induced by ultrasound beams to perturb underlying tissues. This pressure or “acoustic wind” pushes the tissue in the direction of propagation.  An elastic medium such as human tissue will react to this push by a restoring force. This force induces mechanical waves and, more importantly, shear waves which propagate transversely in the tissue.
  • 16. A shear wave induced by an ultrasound beam focused in the center of the image
  • 17. ADVANCES IN SHEAR WAVE IMAGING  SPATIALLY MODULATED ULTRASOUND RADIATION FORCE (SMURFS)  SUPERSONIC SHEAR WAVE IMAGING  AXIAL SHEAR STRAIN IMAGING
  • 18. APPLICATIONS  Breast Imaging  Prostate Imaging  Thyroid Imaging  Liver Imaging  Treatment Monitoring  Intravascular Strain Imaging  Cardiac Elastography  Deep Vein Thrombosis  Kidney Transplant Monitoring
  • 19. BREAST IMAGING  Compared to gray-scale ultrasound, malignant lesions tend to be larger and more irregular on elastography likely secondary to stiff peripheral desmoplastic reaction.  When measuring lesion size on elastography, the lesion should be measured in the exact position on both the elastogram and B-mode image.
  • 20. Heterogeneous echo texture , irregular shape and stiff color elastogram, which appears larger than the gray scale image. The color scale is a measure of stiffness. In these images, red indicates very stiff tissue, green/yellow indicates intermediate stiffness and blue indicates low stiffness IDC
  • 21. Benign lesions demonstrating : homogenoeus oval shape and very soft elastogram, which also appears the same size on both gray-scale and shearwave elastography.. Clustered microcysts
  • 22. FIBROADENOMA
  • 23. COMPLEX CYST V/S SOLID LESIONS  Elastography has the potential to differentiate complicated cysts form solid masses.  Shear-wave propagation does not occur in cysts and therefore cysts should have elastography values of zero and will appear mostly black or homogeneously blue on the color overlay elastogram
  • 24. Large simple cyst which shows no elasticity within the lesion and hence black
  • 25. COMPLICATED CYST- HOMOGENEOUSLY BLUE
  • 26. A bull’s eye artifact has also been described as a characteristic feature present in benign breast cysts, where central fluid may appear bright with a surrounding dark ring
  • 27. PROBLEM SOLVING  Elastography has the potential to downgrade BI-RADS 4a lesions to BI-RADS 3, using qualitative shear-wave elastography and color assessment of lesion stiffness, oval shape and a maximum elasticity value of less than 80 kPa without a significant loss in sensitivity.  Elastography may also be used to identify oval circumscribed cancers detected on ultrasound and may be used to upgrade a BI-RADS 3 lesion to BI-RADS 4.  Furthermore, elastography feature analysis also has the potential to downgrade BI-RADS 3 lesion to BI-RADS 2 lesions.
  • 28. ADVANTAGE Oval circumscribed hypoechoic mass on gray-scale imaging, which has benign ultrasound features. However, elastography demonstrates a
  • 29. QUANTITATIVE ASSESMENT  Lesion stiffness can also be measured quantitatively with shear wave elastography.  Stiffness of malignant lesions is generally greater than 80–100 kPa), while fat has relatively low elasticity values near 7 kPa and breast parenchyma have elasticity values ranging from 30-50 kPa.  However, one must be careful when using kPa in lesion evaluation, as some soft cancers may have low kPA values between 20-80 kPa, similar to benign lesions
  • 30. On compression elastography, hard tissue appears blue and soft tissue appears red to green.
  • 31. THE DOWNFALL….  Some cancers lack a significant desmoplastic reaction and may be soft, resulting in a false negative elastogram .  With shear-wave elastography, some cancers may have a mean stiffness of less than 50 kPa .  Similarly, some benign lesions may appear stiff including hyalinized fibroadenomas, fat necrosis and fibrosis.
  • 32. A heterogeneous mass with indistinct margins on grayscale ultrasound appears stiff, heterogeneous, large and suspicious on shearwave elstography. Biopsy demonstrated benign breast tissue with stromal fibrosis
  • 33. LIVER STIFFNESS  Assessed by US & more recently by MRI  Evaluates velocity of propagation of a shock wave within liver tissue (examines a physical parameter of liver tissue which is related to its elasticity)  Rationale : Normal liver is viscous Not favorable to wave propagation Fibrosis increases hardness of tissue Favors more rapid propagation
  • 34. Liver stiffness cut-offs in chronic liver diseases Matavir F0-F1 Fibrosis Mild F2 F3 Sign Severe F4 Cirrhosis LSM 2.5 – 7 kPa → Mild or absent fibrosis is likely LSM > 12.5 kPa → Cirrhosis is likely
  • 35. MR elastography Conventional MR Wave images at 60 Hz MR elastography Shorter wavelength Normal: 1.7 kPa Longer wavelength Cirrhosis: 18.83 kPa .
  • 36. LSM According to different etiologies of CLD
  • 37. FOCAL LIVER LESIONS Hemangioma, elastic score (ES) =17.31kPa.
  • 38. Malignant tumor, V= 3.73m/sec, elastic score = 41.76kPa.
  • 39. LIMITATIONS OF US ELASTOGRAPHY OF LIVER  Uninterpretable results  Acute liver injury  Extrahepatic cholestasis  Increased CVP  Ascites  Narrow intercostal spaces
  • 40. OTHER APPLICATIONS IN LIVER  Decreased stiffness post anti-viral treatment and increased stiffness in relapse.  Splenic stiffness > 9kPa correlates with portal hypertension.  To d/d between HCV and non HCV infections in liver transplant recipients.  Biopsy site from the stiffest region.  Much larger liver volume assessed then biopsy
  • 41. Lymph nodes  Mainly to d/d between benign and malignant nodes esp. in axillary and cervical nodes.  Score of metastatic nodes in axilla are > 3.5  Scores of metastatic nodes in neck > 2  Sensitivity of > 85 % but less specificity.
  • 42. Elastography image on left shows pattern 1, absent or small hard area. B-mode sonographic image on right shows score of 5, reactive. Final diagnosis from clinical and serologic findings was reactive lymph node.
  • 43. Longitudinal sonogram of level 5 lymph node in 52-year-old man with nasopharyngeal carcinoma. Elastography image on left shows pattern 4, peripheral hard and central soft areas. B-mode sonographic image on right shows score 7, metastatic
  • 44. PROSTATE  TO DIAGNOSE PRIMARY  TO GUIDE FOR CORE BIOPSY  TO SEE EXTRA CAPSULAR EXTENSION
  • 45. ROTATOR CUFF TEAR
  • 46. BURSITIS
  • 47. BAKER’S CYST
  • 48. PITFALLS  LARGE LESIONS CAN BE UNDER ASSESSED WITH PORTIONS OF LESION LYING OUT OF THE VIEW  PAINFULL LESIONS MAYBE UNDER REPRESENTED BECAUSE OF INCREASED DISCOMFORT  TECHNICALLY CHALLENGING IN ORGANS LIKE SALIVARY GLANDS AND OBEESE PEOPLE. INSPITE OF THE FEW SHORT COMINGS, IT’S A BIG RADIOLOGICAL FIND OF THIS CEENTURY AS AN ADJUNCT TO THE OTHER MODALITIES