Transcript A new Ultrasound modality: US Elastography Joel Chabriais

A new Ultrasound modality:
US Elastography
Joel Chabriais
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 »…
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.
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.
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.
Static Elastography
s
e
Axial and lateral
deformations
after an axial
constraint
Courtesy of Dr Anne Tardivon - Institut Curie - Paris
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
SCORE 3
DCIS
SCORE 4
Fibroadenoma
Courtesy of Dr Anne Tardivon - Institut Curie - Paris
IDC
14x8 mm
9x6 mm
Fibroadenoma
6 x 5 mm
5 x 3 mm
Courtesy of Dr Anne Tardivon - Institut Curie - Paris
IDC
Courtesy of Dr Anne Tardivon - Institut Curie - Paris
Static Elastography
Development: Quantitative Analysis
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).
FLR=
a
b
1
1.5
c
2.3
d
3.7
Mean Elasto Fat
Mean Elasto Lesion
Courtesy of Dr Anne Tardivon - Institut Curie - Paris
FLR=1.
2
FLR=8.
9
Tsukuba University Hospital, JAPAN
Courtesy of Dr Anne Tardivon - Institut Curie - Paris
155 lesions (108 Benign and 47 Malign) / 140 Patients
FLR
40
35
cut-off = 4.3
Specificity = 88.8%
Sensitivity = 89.4%
Exactitude = 89.0%
Area under curve = 0.906
30
25
20
15
10
4.3
5
BENIGN
(Mean: 2.95)
MALIGN
(Mean: 11.61)
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
Courtesy of Dr Anne Tardivon - Institut Curie - Paris
Courtesy of Dr Anne Tardivon - Institut Curie - Paris
SuperSonic Elastography
Acquisition time < 30 ms !!
Step 1: Volumetric force
creation using
ultrasound beam focus
Step 2: Ultra fast imaging Step 3: Image
acquisition and
of the displacement
generated by ultrasounds processing
Ultrasound beam
US
images
4% -1% AgarGelatin Elastic
phantom
1D Cross-correlation
~ 100 µs
~ 0.3 ms
Texp=20 ms
Uz(x,t)
Courtesy of Dr Anne Tardivon - Institut Curie - Paris
Supersonic Elastography
 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
µ (kPa)
IDC GRADE III
µ (kPa)
Fibrous Mastopathy
Courtesy of Dr Anne Tardivon - Institut Curie - Paris
Fields of Application in Medicine
 Breast
 Thyroid
 Liver
 Prostate
…
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.
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
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?
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?
…
US Elastography
And after?
Clinical device with mechanical
impulsion compression
MRI
Elasticity module (kPa)
…MRE* is coming!!!
WG 16 wake-up…
But it is another story… ;-)
*Magnetic Resonance Elastography