Elastography is a noninvasive imaging technique that uses ultrasound to image the elasticity or stiffness of tissues. It works by applying slight pressure and measuring how tissues deform. Hard tissues appear stiffer on elastograms. Elastography has many medical applications including differentiating benign from malignant breast lesions, assessing liver fibrosis, and evaluating prostate lesions. Shear wave elastography provides quantitative stiffness measurements and is the most accurate method. While useful, elastography has limitations such as difficulty imaging large or painful lesions and certain anatomical areas. Overall, elastography provides important clinical information about tissue composition when used along with other imaging tests.

2. ELASTICITY FOR ME

3. THEY SPOILED MY CHILDHOOD..

4. 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.

5. 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.

7. 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.

8. 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.

9. 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

10. 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.

11. 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

12. 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.

13. STRESS
Static Elastography. Bmode (left) and elastogram (right).
On the elastogram, less deformed tissue appears darker

14. 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.

15. Dynamic elastography images from MRI .Displacements @
50Hz . Elasticity map (bottom right).

16. 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

17.  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.

18. A shear wave induced by an ultrasound beam focused
in the center of the image

19. ADVANCES IN SHEAR WAVE
IMAGING
 SPATIALLY MODULATED
ULTRASOUND RADIATION FORCE
(SMURFS)
 SUPERSONIC SHEAR WAVE
IMAGING
 AXIAL SHEAR STRAIN IMAGING

20. APPLICATIONS
 Breast Imaging
 Prostate Imaging
 Thyroid Imaging
 Liver Imaging
 Treatment Monitoring
 Intravascular Strain Imaging
 Cardiac Elastography
 Deep Vein Thrombosis
 Kidney Transplant Monitoring

21. 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.

22. 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

24. 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

25. FIBROADENOMA

26. 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

27. Large simple cyst which shows no elasticity within the lesion and
hence black

28. COMPLICATED CYST- HOMOGENEOUSLY BLUE

29. 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

30. 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.

31. ADVANTAGE
Oval circumscribed hypoechoic mass on gray-scale imaging, which has
benign ultrasound features. However, elastography demonstrates a

32. 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

33. On compression elastography,
hard tissue appears blue and soft tissue appears red to green.

34. 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.

35. 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

36. 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

37. 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

38. MR elastography
Conventional MR
Wave images at 60 Hz
MR elastography
Shorter wavelength
Normal: 1.7 kPa
Longer wavelength
Cirrhosis: 18.83 kPa
.

39. LSM According to different etiologies of CLD

40. FOCAL LIVER LESIONS
Hemangioma, elastic score (ES) =17.31kPa.

41. Malignant tumor, V= 3.73m/sec, elastic score = 41.76kPa.

42. LIMITATIONS OF US ELASTOGRAPHY
OF LIVER
 Uninterpretable results
 Acute liver injury
 Extrahepatic cholestasis
 Increased CVP
 Ascites
 Narrow intercostal spaces

43. 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

44. 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.

46. 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.

47. 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

48. PROSTATE
 TO DIAGNOSE PRIMARY
 TO GUIDE FOR CORE BIOPSY
 TO SEE EXTRA CAPSULAR
EXTENSION

49. ROTATOR CUFF TEAR

50. BURSITIS

51. BAKER’S CYST

52. 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