The information contained in this presentation is proprietary and confidential Βασικές...
-
Upload
trista-ranger -
Category
Documents
-
view
219 -
download
0
Transcript of The information contained in this presentation is proprietary and confidential Βασικές...
The information contained in this presentation is proprietary and confidential
Βασικές αρχές της Ελαστογραφίας.
Εξέλιξη της τεχνολογίας στην Ελαστογραφία ShearWave.
Αθήνα, 23 Ιανουαρίου 2010
Θανάσης Λούπας, PhDPrincipal Scientist,
SUPERSONIC IMAGINE SA, France
1
The information contained in this presentation is proprietary and confidential
Elastography BackgroundElastography Background
2
In ancient Egypt, a link was established between
a hard mass within the human body & pathology.
In Hippocratic medicine, palpation was an essential part of a physical examination.
In the 21st century, «remote palpation» by means
of elastographic imaging is becoming a reality.
The information contained in this presentation is proprietary and confidential
Young’s ModulusYoung’s Modulus
E = StressStrain
esSTRESSSTRESS
STRAINSTRAIN
kPaELASTICITYELASTICITY
High Strain Easy to deform Low ElasticityLow Strain Hard to deform High Elasticity
3
Palpation Qualitative estimation of tissue elasticity
Young’s Modulus E quantifies elasticity in units of kiloPascals, as the ratio of the Stress S (compression) applied to a body
divided by the Strain e (relative deformation) it produces.
The information contained in this presentation is proprietary and confidential
Different types of soft tissue have similar density but exhibit significant variation in elasticity.
Elasticity variations can help detect / characterize focal (e.g. malignant masses) and diffuse (e.g. fibrosis) pathologies.
4
Organ / Soft tissue type Young’s modulus E (kPa)
Density (kg/L)
Breast Normal fat 18-24
1.0 ± 10% ~ water
Normal glandular 28-66
Fibrous tissue 96-244
Carcinoma 22-560
Prostate Normal anterior 55-63
Normal posterior 62-71
BPH 36-41
Carcinoma 96-241
Muscle 6-7
Liver Healthy tissue 0.4-6
Kidney Fibrous tissue 10-55
“Virtual” Biopsy“Remote” Palpation
Soft Tissue ElasticitySoft Tissue Elasticity
The information contained in this presentation is proprietary and confidential
Elasticity Imaging R&DElasticity Imaging R&D
Many R& D techniques have emerged since the 1990s, based on the Ultrasound and Magnetic Resonance imaging modalities. Sonoelasticity: KJ Parker et al, 1990 Ultrasound Strain Elastography: J Ophir et al, 1991 MR Elastography: R Sinkus et al, 2000 Shear Wave Elastography: J Bercoff et al, 2004
All techniques are based on the same principle: Generate a stress, and then use an imaging technique to map the
tissue response to this stress in every point of the image.
but differ substantially in terms of their performance characteristics: Qualitative / quantitative nature, absolute / relative
quantification. Accuracy / precision / reproducibility, … Spatial / temporal resolution, sensitivity / penetration, …
COMMERCIALY AVAILABLE
5
The information contained in this presentation is proprietary and confidential
The basic principle used is the one proposed by Ophir’s group in the early 1990s:
1. Tissue compression (Stress) is induced manually by the user.
2. Multiple images are recorded using conventional imaging at standard frame rates.
3. The relative deformation (Strain) is estimated using Tissue Doppler techniques.
4. The derived strains are displayed as a qualitative elasticity image.
Initially introduced by Hitachi, and later on Siemens,
in the early 2000s.
More manufacturers have followed in the last year(s).
StrainStrain ElastographyElastography
6
The information contained in this presentation is proprietary and confidential
Pre-compression RF line
Post-compression RF line
dT T
Pre-compressionRF lines
Post-compressionRF lines
Local Cross Correlation Analysis
STRAIN ESTIMATION
Strain represents relative deformation, and is expressed in qualitative units (soft / hard)
Soft objects High Strain
Hard objects Low Strain
Strain = dT / T
StrainStrain Elastography ProcessingElastography Processing
7
The information contained in this presentation is proprietary and confidential
StrainStrain Elastography SummaryElastography Summary
Straightforward implementation on current scanners (standard acquisition architecture, plus Tissue-Doppler-like processing). Stress penetration / uniformity issues. User-applied compression is attenuated by soft objects &
depth,and cannot penetrate hard-shelled lesions.
User-dependence. The extent of tissue compression affects the elasticity image.
8
The information contained in this presentation is proprietary and confidential
From Strain to Shear Wave Elastography From Strain to Shear Wave Elastography
E = Stress Strain
kPa
E = 3 cS2 kPa
Sarvazyan AP: Method and device for shear wave elasticity imaging. US Patent 5,606,971 1997.
Sarvazyan et al : Shear wave elasticity imaging -- A new ultrasonic technology of medical diagnostics. Ultrasound Med Biol 1998; 24:1419-35.
L Sandrin, S Catheline, M Tanter, C Vinçonneau, M Fink : 2D Transient Elastography Acoust. Imag., Vol. 25, pp 485-492, 2000. M Tanter, J Bercoff, L Sandrin, M Fink : Ultrafast compound imaging for 2D motion vector estimation : Application to transient elastography IEEE Trans UFFC, Vol. 49, pp 1363-1374, 2002.
9
The information contained in this presentation is proprietary and confidential
Shear Waves in Medical UltrasoundShear Waves in Medical Ultrasound
Until now, Medical Ultrasound imaging has been
based entirely on Longitudinal waves.
PropagationDirection
PropagationDirection
Tissue Motion
Tissue Motion
SHEARWAVE
LONGITUDINALWAVE
10
The information contained in this presentation is proprietary and confidential
Shear Wave SourcesShear Wave Sources
Natural
Heart
External
Mechanical force
Focused Ultrasound
PW Doppler
11
The information contained in this presentation is proprietary and confidential
Shear Wave GenerationShear Wave Generation
Focused ultrasound is transmited at multiple points along a line of interest.
An individual Shear Wave is generated and starts propagating around each focal point.
The superposition of the individual Shear waves creates a Shear Wave-front similar to the Super Sonic Mach Cone.
SonicTouch
12
The SonicTouch Shear Wave generation process is completely automated and user-independent.
The information contained in this presentation is proprietary and confidential
Shear Wave DetectionShear Wave Detection
Shear Wave Speed = 5 m/s
1 mm in 0.2 milliseconds
The typical Shear Wave speed cS in soft tissue is ~ 5 m/s.
This means that the Shear Wave needs 0.2 ms to travel 1 mm.
Thereforein order to have a spatial resolution of 1 mm, we must image the Shear Wave once every 0.2 ms, i.e. 5000 times per second.
5000 images per second needed!Almost 100 times more than the frame rates that current ultrasound scanners can offer (best case, 50-100 frames/second).
13
The information contained in this presentation is proprietary and confidential
Ultrafast Imaging
Plane-wave transmissions are performed, each of them covering the whole image area.
For each transmission, the data received from all points of the image are processed using advanced reconstruction techniques to form the full image at once.
One frame is produced for every transmission, resulting in frame rates of up to 20 000 Hz.
More than one transmit events may be combined to improve image quality by trading-off some frame rate.
14
Shear Wave DetectionShear Wave Detection
The information contained in this presentation is proprietary and confidential
Shear Wave Imaging StepsShear Wave Imaging Steps
Uniform-elasticityphantom
~ 100 µs
Step 1 Shear Wave generation
60 frames at a frame rate of 3000 Hz0.33 ms
Total duration: 20 ms !
Step 3 Shear Wave propagation
image formation
15
Shear Waves
Longitudinal Waves
SonicTouch
Ultrafast Imaging
Step 2 Shear Wave Detection
The information contained in this presentation is proprietary and confidential
Shear Wave ElastographyShear Wave Elastography
Shear Wave Imaging sequence @ 3000Hz
Breast Elastography phantom withuniform background + hard lesion
E= 3cS2
J. Bercoff, M. Tanter, M. Fink: Supersonic shear imaging: A new technique for soft tissue elasticity mappingIEEE Trans Ultrason Ferroelectr Freq Control, pp 396-409, 2004
16
Key Reference
Shear WaveSpeed cS
Estimation
The information contained in this presentation is proprietary and confidential
Shear Wave ElastographyShear Wave Elastography
Real-time operation
17
The information contained in this presentation is proprietary and confidential
Shear Wave ElastographyShear Wave Elastography
Mean =5.1 kPaStdDev =0.15 kPa (3%)
Mean =10.5 kPa StdDev =0.8 kPa (7%)
10-13 Kpa
5 -7 Kpa
Calibrated Elastometer values
Accuracy / precision testing using calibrated elasticity phantoms
Shear-Wave Elastography measurements
TRULY-QUANTITATIVE NATURE• Absolute elasticity quantification• High accuracy / precision.
18
The information contained in this presentation is proprietary and confidential
Shear Wave ElastographyShear Wave Elastography
TRULY-QUANTITATIVE NATURE• Absolute elasticity quantification• High accuracy / precision
19
SimulatedTissue
« Fat 1 »
« Fat 2 »
« Glandular »
« Cancer »
Reference Elasticity
(kPa)
15.8 23.9 37.4 105.7
SWE Mean (kPa)
14 20 36.4 105
SWEStdDev (kPa)
2.3 3.1 5.4 11.5
Extensive validations using calibrated tissue-mimicking phantoms.
The information contained in this presentation is proprietary and confidential
Shear Wave ElastographyShear Wave Elastography
Elasticity Ratio Axial Res (mm) Lateral Res (mm)
2 1 1.1
3 1.2 1.2
10 1.3 1.1
Lateral resolution
Axial resolution
Custom-made two-layer phantomswith multiple elasticity ratios
High spatial resolution• Typically, ~ 1 mm axially & laterally for the SL 15-4 linear transducer.
20
The information contained in this presentation is proprietary and confidential
Shear Wave ElastographyShear Wave Elastography
Highly-localized estimationof tissue elasticity • Especially, inside hard lesions
Phantom with liquid center inside hard lesion
Strain Elastography interprets the wholelesion as hard, because the applied manualcompression cannot penetrate the hard shell.
Shear Wave Elastography can “see” insidethe hard lesion, because the shear waves can propagate through the hard shell.
21
The information contained in this presentation is proprietary and confidential
Strain vs. Shear Wave ElastographyStrain vs. Shear Wave Elastography
22
Strain Elastography tends to produce abinary classification, where the whole lesion is either hard or soft.
Shear Wave Elastography provides richer& more complex information with manycases of hard borders plus soft centers.
The differences between Strain and Shear Wave Elastography are not surprising, given the very different principles on which they are based.
The information contained in this presentation is proprietary and confidential
Shear Wave Elastography Summary Shear Wave Elastography Summary
Unique to SuperSonic Imagine, due to need for advanced capabilities (SonicTouch, Ultrafast Imaging), and intellectual property protection.
Rich / complex mapping of hard lesions, with heterogeneous
elasticity in the lesion periphery and/or center.
23
The information contained in this presentation is proprietary and confidential
Shear Wave Elastography ApplicationsShear Wave Elastography Applications
SWE is fully-integrated feature of the Aixplorer premium Ultrasound scanner.
24
Organs currently targeted by SWE include:• Breast, Thyroid, and Liver.
Work-in-progress encompasses:• Prostate, Musculoskeletal, and 3D Breast applications.
R&D efforts focus on Cardiovascular and Ophthalmology applications.
The information contained in this presentation is proprietary and confidential25
Multi-center Breast Elastography TrialAssessment Of The Clinical Benefits Of SuperSonic
Shear Wave Elastography In The Ultrasonic Evaluation
Of Breast Lesions Dates: Q2 2008 to Q2 2010
Sites: 11 centers in Europe & 6 centers in USA Primary aim: Assess the benefit of Shear Wave Elastography for the characterization of breast lesions. Secondary aim: Assess the benefit of Shear Wave
Elastography for the visualisation of breast lesions.
Clinical trial and data analysis currently under way.
Preliminary results very promising. Improved sensitivity and specificity of breast ultrasound BIRADS diagnosis with SWE + ECHO versus ECHO only.
The information contained in this presentation is proprietary and confidential
Clinical Evaluation of SWE for Liver Fibrosis Staging
26
SWE: Fibroscan:
Bavu et al, “Non-invasive in-vivo Liver Fibrosis staging using Supersonic Shear Imaging: a Clinical Study”, Gastroenterology, 2010 (in press).
The information contained in this presentation is proprietary and confidential
CONCLUDING REMARKSCONCLUDING REMARKS
27
The information contained in this presentation is proprietary and confidential28