Quantitative Elasticity Imaging with Acoustic
Radiation Force Induced Shear Waves
Kathy Nightingale, Mark Palmeri, Ned Rouze,
Stephen Rosenzweig, Michael Wang, Gregg
Trahey
Department of Biomedical Engineering
Duke University
FEM: Homogeneous Medium
transducer
2αI ta
F=
c
µ=1 kPa, movie duration = 10 ms
Palmeri et al “A finite element method model of soft tissue response to
impulsive acoustic radiation force”, IEEE UFFC, 52(10): 1699-1712, 2005.
In Vivo - Liver - Hepatocellular Carcinoma
B-mode
ARFI
•Patient with liver cirrhosis, hepatitis C, HIV+
•HCC appears softer than surrounding cirrhotic liver tissue
Fahey , et al. “In vivo visualization of abdominal malignancies with acoustic radiation force elastography”, Phys.
Med. Biol. 53 (2008) 279–293.
Shear Wave Elasticity Quantification Methods
• External excitation methods:
– Sonoelastography (Parker 2001)
– FibroScan (Sandrin 2003)
• Radiation force based shear wave elasticity
imaging (SWEI*):
– Helmholtz inversion (Nightingale and Trahey, 2003)
– Supersonic Shear Imaging (SSI, Fink 2004)
– Shear Dispersion Ultrasound Vibrometry (SDUV, Greenleaf
2004)
– Lateral TTP (Palmeri, 2008)
– RANSAC (Wang, 2009)
– Spatially-Modulated Ultrasound Radiation Force (SMURF,
McAleavey, 2010)
*Sarvazyan et. al., 1998
Time of Flight (TOF) Based Algorithms
soft
soft
stiff
stiff
C=inverse slope
µ=ρc2
Acoustic Radiation Force Generated Shear Wave in
Human Liver, In Vivo
NASH Patient Population
sensitivity 90%
specificity 90%
AUC of 0.9
cutoff =4.24 kPa
Advanced fibrosis
Low grade fibrosis
Palmeri et al. “Evaluating Liver Fibrosis Non-invasively in NAFLD Patients Using Ultrasonic
Acoustic Radiation Force-Based Shear Stiffness Quantification”, J. of Hepatology, in press
Available online 21 January 2011, ISSN 0168-8278, DOI: 10.1016/j.jhep.2010.12.019.
Vertical Layer – resolution and precision
∆ RMS (m/s)
regression kernel size:
5 mm kernel
Resolution (mm)
2 mm kernel
∆ RMS (m/s)
Vertical Layer – shear wavelength
Heterogeneous Material (spherical lesion)
Simulated Spheres – Shear Wavelength
F/2
F/4
Quantitative SWS imaging sequences
lateral position
Experimentally Acquired Images:
ARFI
Sphere:
Concentric
Spheres:
SWS
Combined Concentric Sphere Image
Maintains resolution of ARFI
Adds quantitative information from SWS data
3D Monitoring Homogeneous Phantom
ISPPA0.7 = 1670 W/cm2, 400 cycles, 1.1 MHz Push
Shear Wave Speed Measurement
Reconstructed shear
wave speed cT = 1.8 m/s
Ex-vivo Muscle Data
ISPPA0.7 = 4400 W/cm2, 400 cycles, 1.1 MHz Push
Ex-vivo Muscle 3D Shear Wave Arrival Time
SWS (m/s) vs. direction
8
6
4
2
Summary
•
Tissue stiffness can be quantified with radiation
force based methods with high precision
• In heterogeneous media:
• Precision improves with
• larger regression kernels
• smaller shear wavelengths
• Resolution improves with smaller regression
kernels
• Commercial systems available (Siemens,
SuperSonic Imagine), many clinical applications
under investigation
• What’s coming?
• Combined on- and off-axis approaches
• 3D SWS monitoring
Acknowledgements
• NIH NIBIB R01EB002132
• NIH NCI R01CA142824
• Siemens Medical Solutions, USA, Inc.,
Ultrasound Division