SONOELASTOGRAPHY

JSS Medical College, Mysuru
SONOELASTOGRAPHY
PRESENTER-Dr.Vishwanath patil
PG Resident
MODERATOR-DR. RUDRESH HIREMATH
PROFESSOR OF RADIOLOGY

Definition.
Principle.
Terminologies used in elastography.
Different elastography techniques.
1. Compression Elastography
2. ARFI
3. SWE
Depiction of elastograms.

DEFINITION
• It is non invasive novel technique of imaging & mapping the
stiffness or elasticity of tissues induced by compression.
• Elastography can be performed with ultrasound and MRI. In
ultrasound it is also known as sonoelastography.

PRINCIPLE
• Every tissue in the human body pertains some amount of
elastic properties. This elastic property get distorted or
hampered by the diseases, particularly by the malignant
lesions.
• This change in the elastic property of the diseased tissue is
used as principle in elastography.
• The technique is first described in 1987 by Krouskop et al.

Physicians & surgeons have
acquired clinical skill of
palpation of masses to detect
differences in tissue stiffness as
an aid to diagnosis.
We radiologist lack this as
we stick to our ultrasound
machines and probes.

So what do we call
this technique as ?
We can call elastography as VIRTUAL PALPATION technique
designed for radiologists to differentiate stiffer tissues from
softer one.

The advantage we have with this technique is we can
virtually palpate the masses situated deep, which is
not available for manual palpation.

Terminologies used in elastography
• STRESS
• STRAIN
• ELASTICITY
• VISCOSITY.
• VISCOELASTICITY.
• YOUNG’S MODULUS

STRESS: Stress is defined as force per unit area
Stress perpendicular to the object
shortening of object
Stress parallel to the object
distortion of object.

STRAIN: Amount of Change or deformation in the size and
shape of an object subjected to stress is strain.
LONGITUDINALSTRAIN- change in the
length of an object.
SHEAR STRAIN- change in the angles of
an object
• Stress parallel
to the object
• Stress perpendicular
to the object

• The property of materials to return back to the its original form after stress
is removed is known as elasticity.
Elasticity

Viscosity
• Viscosity is the measure of resistance of a fluid when it
undergoes shear stress or tensile stress.

VISCOELASTICITY
• This is property of materials to exhibit both viscous and elastic
properties

YOUNG'S MODULUS
• Tissue stiffness can be quantified using the a value known as
Young's Modulus.
• Ratio of the compression force applied to tissue (stress) and the
resulting tissue deformation (strain).
• Young’s modulus(elasticity) = Stress/Strain.
• This is measured in kilopascals (kPa).

Typical values of elasticity in different types of tissues .

DIFFERENT ELASTOGRAPHY
TECHNIQUES,

FREE HAND SONOELASTOGRAPHY OR
COMPRESSION ELASTOGRAPHY OR STATIC
ELASTOGRAPHY
• Is based on the signals acquired before and after tissue
displacement induced by the manual probe compression.

STRAIN ELASTOGRAPHY
• Manual compression is applied by probe over the mass lesion
in the direction perpendicular to the tissue surface.
Radiofrequency signals are obtained from the tissues before
and after compression.
• Tiny changes produced by the manual compression induces
change in the phase of radiofrequency echoes. The amount of
shift in the signals equals the amount of tissue displacement at
the point in the image frame.

Pre
compression
RF A LINE
Post
compression
RF A LINE

• Tissue displacements are registered and converted into B mode
images.
• A dedicated software is then used to calculate the relative
difference in tissue movement from one frame to another and
then estimates tissue deformation.

• PRE
COMPRESSION
RF A LINE
POST
COMPRESSION
RF A LINE
REGISTERED AND
CONVERTED INTO B
MODE IMAGES
REGISTERED AND
CONVERTED INTO B
MODE IMAGES
Dedicated software to
calculate difference in tissue
movements from one frame to
another
Elastograms

What to look for in elastographic images ?
• In case of sonoelastographic images, lesion brightness,
uniformity and the size ratio helps to differentiate benign from
malignant lesions.

Display of elastogram
 Images are displayed as darker and brighter images.
 Color scale images which are superimposed on B mode
images.
 Strain ratio – calculated to compare two area of different
stiffness.

• Images are displayed as darker and brighter images.
• Harder areas exhibit less tissue displacement, displaying darker
strain images while soft areas exhibit more tissue displacement
and brighter strain images.

• In benign tumors, the transverse diameters measured on
elastographic images are almost always the same as or smaller
than the diameters of the tumors seen on B-mode images,
whereas the diameters of malignant tumors on elastographic
images are larger than those seen on B-mode images.

Infiltrative ductal carcinoma – depicting dark strain images with surrounding normal
tissue revealing bright strain.
Lesion is larger in elastography images compared to the normal B mode ultrasound.

Cysts have a typical “bull’s eye” appearance (smaller size,
white center, black peripheral circle) (Siemens machines) or
characteristic noise pattern(philips). (Philips).

B. Color scale images which are superimposed on B
mode images.
 On ultrasound machines, a color elastograms is displayed on
the screens.
 Itoh proposed an elasticity score which is compared to the BI-
RADS.

 Itoh et al, evaluated the color pattern of images in both the
hypoechoic lesion and in the surrounding breast tissue.
 An elasticity score on a five-point scale was attributed :
 The risk of malignancy increases from Score 1 (a benign
lesion) to score 5 (malignant lesion).

A score of 1 ~ an entirely green lesion (even strain throughout
the lesion),

A score of 2 ~ strain in most of the hypoechoic lesion, with some
strain free areas (a mosaic pattern of green and blue),

A score of 3 ~ strain at the periphery of the hypoechoic lesion, with
sparing of the center of the lesion (the peripheral part of the lesion in
green, and the central part in blue),

A score of 4 indicated no strain throughout the hypoechoic lesion (the entire
lesion in blue, but the area surrounding it is not included).

A score of 5 indicated no strain in the entire hypoechoic lesion or in
the surrounding area (both the lesion and surrounding area are
blue).

Mosaic Green & blue appearance- benign- Fibro
adenoma

Homogenously blue appearance on elastograms- suggestive of
malignancy – infiltrative ductal carcinoma.

PHILIPS MACHINES :
• In color mode, malignant lesions are depicted in blue whereas benign
lesions appear in red (soft).
• Cystic lesions have a typical three-color mixed appearance (red, green,
blue).
• Finally, with a specific software, a pure cystic content appears in yellow,
and can be differentiated from a dense cyst exhibiting a blue center.

THREE COLOR MIXED APPERANCE SEEN IN BENIGN
CYSTIC LESION

C. Strain ratio – calculated to compare two area of different
stiffness.
 Two Regions of Interest (ROI) are simultaneously set in the center of the lesion,
and in the surrounding breast tissue.
 Elasticity values are shown on compression-decompression time curves.

Strain ratio
 The higher the ratio between the two curves at time , greater
the stiffness, and the higher the risk of malignancy, especially
for a lesion with little elasticity.
 Conversely, a benign lesion shows similar elasticity values on
the time/intensity curves as the surrounding tissue.

High difference between the compression and decompression time curves

Similar the compression and decompression time curves

• Limitations :
 Pressure on the probe should be very light much lighter than for a normal
ultrasound acquisition.
 The technique is qualitative imaging of tissue stiffness.
 Can be utilized as semi quantitative technique with the evaluation of strain
ratio.

Transient Elastography (TE):
• A system developed and commonly used for liver fibrosis
• Mechanical piston within a ultrasound transducer is used to apply a push to
the skin over an intercostal space.
• The speed of the produced shear waves into the liver, along the direction of
the ultrasound beam, is measured in a way similar to M-mode.

ARFI TECHNOLOGY: ACOUSTIC RADIATION
FORCE IMAGING
• Advantage of being objective and independent of the sonographer.

PRINCIPLE
Ultrasound scanners are used to generate short-duration acoustic
radiation forces that impart small (1–10 micrometer) localized
displacements in the tissue, the response of which is observed
using conventional B-mode imaging that correlates with local
stiffness.
No requirement of external compression.

• Velocity of the shear wave depends on tissue stiffness, so it is possible to
apply ARFI technology to evaluate deep tissue stiffness.
• This technology was first available on abdominal probes and mostly used
to evaluate the degree of fibrosis in a cirrhotic liver.
• ARFI technology is now available on high-frequency (9 MHz) probes, and
can be used for breast imaging.

• Although it is independent of the operator, it is still important
to apply very light pressure to the probe, because high pressure
on a probe can affect the compression and elasticity of breast
tissues, and modify stiffness values.

Virtual Touch Imaging (VTI):
• Series of acoustic push pulse/detection pulse sequences: Acoustic push
pulse is transmitted to compress tissue than detection pulses are used to
track the amount of displacement on axis to the push pulse within the ROI.
• The relative tissue displacements are mapped to the image.

Infiltrative ductal carcinoma- black elastogram indicative of
malignancy
VTIB MODE

Virtual Touch Quantification (VTQ):
• Push pulse (orange) generates shear waves (blue) through a user-placed region of
interest.Detection pulses (green) track displacement vs. time off axis to the acoustic
push pulse. Time to Peak (TTP) is measured along each detection beam and speed
is computed. The speed of shear wave propagation is related to tissue stiffness.

Virtual Touch Quantification (VTQ):
 It provides the quantitative numerical measurement of the lesion.
 The shear waves propagate faster in stiffer tissue than in the soft tissues.
 In most of the malignant breast lesions, speed is usually higher than 2 m/s.

Speed of shear wave

Advantages
 More homogenous and
better contrast than
compression elastography.
 Elastography of deeper
tissue can be performed
(liver).
Disadvantages
 Physiological and
transducer motion can
degrade the image quality.
 Tissues deeper than 10 cms
cannot be accurately
assessed.

SWE: SHEAR WAVE ELASTICITY: SUPERSONIC IMAGING
• Features of this technique are similar to those of ARFI technology.
• Supersonic speed is a rate of travel of an object that exceeds the speed of
the sound.

Shear wave Elastography
• Supersonic imagine is the company which has developed & utilizing this
technique in their machines (Aixplorer).
• FDA APPROVED IN 2013

Shear Wave Elastography
• Impulsive Acoustic radiation force of a focused ultrasound beam.
• Shear wave propagation perpendicular to the axial displacement caused by
ultrasound wave

• A very fast (5000 frames /sec) US acquisition sequence is used to capture
the propagation of shear waves.

 The displacement induced creates a shear wave that provides information
about the local viscoelastic properties of the tissue. Hence providing the
quantitative information.
 Stiffness information is given in kPa.
 A color scale linked to the value in kPa which ranges from 0 to 240 kPa is
also available

Cystic lesion showing 0 kPa and blue color on color code.

• Optimal cut-off value to differentiate benign and malignant breast lesions
in recent studies, was 80.17 kPa.

Advantages
 More objective measurement.
 Direct assessment of elasticity &
quantitative measurements are
provided.
Disadvantages
• Assessment of superficial
structures may be difficult, as
certain depth of ultrasound
penetration is needed for shear
waves to be produced.

Uses
• Differentiating malignant and benign neoplasms (especially breast)
• Identifying early traumatic changes in muscles and tendons
• Aiding in deciding the biopsy site more accurately, reducing negative
biopsy rates assessing liver fibrosis
• Assessing liver steatosis (eg non-alcoholic fatty liver disease and
steatohepatitis).
• Splenic stiffness >9kPa correlates with portal hypertension.

Uses
• Some studies show that the biopsy rate could be reduced in case of
BIRADS 3-4a benign lesions in women with a high risk of breast cancer .

Recent Advances
• Spatially Modulated Ultrasound Radiation Force (SMURF):propagation of shear
waves generated at separated excitation locations is monitored at a single tracking location.
• Shear Wave Spectroscopy

SUMMARY

SUMMARY
• ShearWave Elastography is the result of the exploration of a new type of
wave – the shear wave - by a revolutionary new architecture which enables
quantification of soft tissue elasticity in real time.

References
• 1. Sigrist R, Liau J, Kaffas A, Chammas M, Willmann J. Ultrasound Elastography: Review of Techniques and Clinical
Applications. Theranostics. 2017;7(5):1303-1329.
• 2.Gallotti A, D’Onofrio M, Romanini L, Cantisani V, Pozzi Mucelli R. Acoustic radiation force impulse (ARFI) ultrasound
imaging of solid focal liver lesions. Eur J Radiol 2012;81(March (3)):451–5.
• 3.A. Arcidiacono, A. Corazza, S. Perugin Bernardi, R. Sartoris, D. Orlandi, E. Silvestri; Genova/IT, Real-time Shear Wave
and Strain Sonoelastography in muscles and tendons.
• 4.Itoh A, Ueno E, Tohno E, et al. Breast disease: clinical application of US elastography for diagnosis. Radiology
2006;239(May (2)):341–50.
•

• THANK YOU….,

SONOELASTOGRAPHY

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