OCE operates on the principle that the mechanical properties of tissues, such as elasticity and stiffness, influence the propagation of mechanical waves within them. These mechanical waves can be induced by external stimuli, such as acoustic radiation or direct mechanical deformation, and their propagation can be monitored using OCT. When a tissue is subjected to mechanical stress or compression, it undergoes deformation, and this deformation affects the speed and amplitude of the propagating waves. By analyzing the changes in the properties of these waves, OCE can provide quantitative measures of tissue stiffness and elasticity.

1. A new Ultrasound modality:
US Elastography
Joel Chabriais

2. Why Elastography?
 In old Egypt, 5 000 years ago, physicians
examined the different parts of the body to
evaluate elasticity, they knew that a hard mass in
an organ is pathologic.
 In Greek ancient age, for Hippocratic medicine,
palpating was an essential time of physical
examination.
 In 21st century, imaging take preeminent place in
medicine and Elastography could be considered as
an « imaging palpation »…

3. What is Elastography?
 Elastography is an imaging technique to measure
the stiffness of tissues.
 Images are acquired before and after soft
compression of tissues and the deformation is
evaluated.
 Initially elastography used manual compression
and was only qualitative, now some methods
appears to apply a non operator dependant
compression.

4. Elastography and US
 Elastography was developed first in the US
field.
 Three step approach:
 Organs mechanically stressed by either external
or internal forces.
 Measurement of tissues movement induced.
 Qualitative or quantitative evaluation of tissue
elastic properties from the measured
displacement of tissues.

5. Several Approaches
 Manual compression by operator using the
transducer (static elastography).
 Organ compression by heartbeat or vascular
pulsations.
 Push pulse waves compression.
 Supersonic shear waves.

6. Axial and lateral
deformations
after an axial
constraint
s
e
Courtesy of Dr Anne Tardivon - Institut Curie - Paris
Static Elastography

7. Ueno Staging
1 = Lesion distortion similar than in surrounding tissues
2 = Heterogeneous distortion versus surrounding tissues
3 = Lesion center distort less than surrounding tissues
4 = Whole the lesion distort less than surrounding tissues
5 = Whole the lesion and adjacent tissues distort less
than surrounding tissues

8. SCORE 3
DCIS
SCORE 4
Fibroadenoma
Courtesy of Dr Anne Tardivon - Institut Curie - Paris

9. 9x6 mm 14x8 mm
IDC
6 x 5 mm 5 x 3 mm
Fibroadenoma
Courtesy of Dr Anne Tardivon - Institut Curie - Paris

10. IDC
Courtesy of Dr Anne Tardivon - Institut Curie - Paris

11. This measurement quantify elasticity
correlation between two regions.
The FLR is independent of the
compression movement.
The 1st region define the lesion
and the 2d is the reference (fat).
a b c d
1 1.5 2.3 3.7
FLR=
Mean Elasto Fat
Mean Elasto Lesion
Courtesy of Dr Anne Tardivon - Institut Curie - Paris
Static Elastography
Development: Quantitative Analysis

12. FLR=1.
2
FLR=8.
9
Tsukuba University Hospital, JAPAN
Courtesy of Dr Anne Tardivon - Institut Curie - Paris

13. 5
20
25
30
35
40
15
10
4.3
cut-off = 4.3
Specificity = 88.8%
Sensitivity = 89.4%
Exactitude = 89.0%
Area under curve = 0.906
FLR
BENIGN MALIGN
(Mean: 2.95) (Mean: 11.61)
155 lesions (108 Benign and 47 Malign) / 140 Patients
Courtesy of Dr Anne Tardivon - Institut Curie - Paris

14. Courtesy of Dr Anne Tardivon - Institut Curie - Paris
Elastography: improvements
 Compression/Decompression Movements
 Displacement speed measurement
 Integral -> Elasticity
 Elasto Q Mode
 Information at decompression
 Automatic selection of the best cycle
 ROI on fat and lesion
 Quantification

15. Courtesy of Dr Anne Tardivon - Institut Curie - Paris

16. 4% -1% Agar-
Gelatin Elastic
phantom
~ 100 µs
Step 1: Volumetric force
creation using
ultrasound beam focus
1D Cross-correlation
Step 3: Image
acquisition and
processing
Ultrasound beam
US
images
Uz(x,t)
Step 2: Ultra fast imaging
of the displacement
generated by ultrasounds
Texp=20 ms
~ 0.3 ms
Acquisition time < 30 ms !!
Courtesy of Dr Anne Tardivon - Institut Curie - Paris
SuperSonic Elastography

17.  Significant difference benign versus malign:
 Cancers: E = 170.1 ± 41.6 kPa
 Benign lesions: E = 53.5 ± 19.8 kPa
n= 36
Courtesy of Dr Anne Tardivon - Institut Curie - Paris
Supersonic Elastography

18. µ (kPa)
µ (kPa)
IDC GRADE III
Fibrous Mastopathy
Courtesy of Dr Anne Tardivon - Institut Curie - Paris

22. Fields of Application in Medicine
 Breast
 Thyroid
 Liver
 Prostate
 …

23. Elastography in DICOM: Why?
 Now, several vendors are coming on the market:
 Until 2008: 1 vendor had products for sale.
 2008: 3 vendors.
 2009: several announcements  6 vendors or more.
 … probably every US vendor at short term.
 At this time, only secondary capture or US objects.
 All specific information to elastography are lost.

24. Elastography in DICOM: Why?
 More and more clinical applications.
 New BI-RADS edition, planned for 2010, will take
into account US elastography for breast imaging.
 Users would like to be able to store elastography
information in their PACS:
 Additional attributes in US objects?
 New objects?
 Some pathology needs elastography follow-up:
 Probably DICOM SR templates needed

25. Elastography in DICOM:
Who is Concerned?
 Elastography is US  WG 12
 Elastography for Breast imaging  WG 15
 Elastography needs DICOM SR templates  WG
8
 Other?

26. Elastography in DICOM:
How To Go Further?
 A motion to ask the concerned WG to investigate
the domain to determine if further works needed?
 Report to DICOM Standards Committee?
 …

27. US Elastography
And after?

28. Clinical device with mechanical
impulsion compression
MRI Elasticity module (kPa)

29. …MRE* is coming!!!
But it is another story… ;-)
WG 16 wake-up…
*Magnetic Resonance Elastography