Vibro-Acoustography and Vibrometry for Imaging and Measurement of Biological Tissues

Transcription

1 Vibro-Acoustography and Vibrometry for Imaging and Measurement of Biological Tissues James. F. Greenleaf Mostafa Fatemi Radall Kinnick Shigao Chen Cristina Pislaru Xiaoming Zhang Matt Urban Mayo Clinic College of Medicine Rochester MN

2 Background Palpation Radiation force Imaging approach Vibrometry approach Imaging of breast in vivo Quant with calcification Imaging of vessel in vivo Quant of vessel modes Summary

3 Palpation Ancient method of disease detection. Breast, Prostate, Aorta, Pulmonary. Not sensitive because uses fingers. Not an imaging method. Not objective, depends on skill. Only works superficially.

4 Radiation Force Radiation Force = (Total Power) / Speed F=dP/c 0<d< Beam Speed of sound in air = 0.33 km/s F=3.303mN/W Speed of sound in water = 1.5 km/s F=0.66mN/W Speed of light = 300,000 km/s F=3.33nN/W F Object

5 Radiation Force Methods Sarvazyan et al., Ultrasound Med. Biol. (1998) Fatemi & Greenleaf Science, Vol 80, (1998) Nightingayle et al., JASA 115, (001) Berkoff et al., IEEE UFFC (004)

6 Goal of Method M. Fatemi, J. Greenleaf

7 Schleiren Image of Confocal Beam 40mm MHz MHz 65mm T. Pitts, J. Greenleaf

8 Vibro-Acoustography Imaging System RF Gen. w w+dw Hydrophone Filter Detector RF Gen. Confocal Transducers Object Monitor Transducer Face

9 Acoustic Emission vs Incident Ultrasound Pressure Modulated Ultrasound Beam Measurement point Emission Dw Velocity U Acoustic emission: P r r ( Dw, t, r) = S d( Dw, t, r) H( Dw, t, r) Q( Dw, t, r) Pw r r 0 Q p b Z = = Acoustic outflow per unit force ~ Mech. Admittance H = Medium Transfer Function d = Drag Coefficient

10 Vibro-acoustography of Arteries Fatemi and Greenleaf, Science (1998)

11 Breast images in vivo

12 Stereotactic Biopsy Mammograph Detector X-ray source

13 Addition of VA Tank

14 Scan Tank with Ultrasound Transducer and Scan Window Ultrasound Transducer Interface Boot Stage Assy

15 In vivo vibro-acoustography image of normal breast 5 cm

16 50 khz Vibro-acoustic Image of Normal Female Breast 5 cm Depth.5 cm 1.5 cm

17 5 cm Breast with large calcification and fibroadenoma X-ray VA (Depth=3.5cm) Fused VA+Xray

18 Mammography Vibro-acoustography, f = 50 khz VAN005.5 cm 3.0 cm 3.5 cm 4.0 cm 4.5 cm

19 Summary of Breast Imaging Breast images are high resolution Breast images are high contrast Images degrade at large depth Images are not quantitative

20 Can we measure tissue properties with particle (calcification) vibration?

21 Radiation Impedance of a Rigid Oscillating Sphere = aki k a aki k a h a ah i aki k a h a ah i h a ah i a i Z r ρω π µ ρω / h = ( ) λ µ ρω + = / k µ 1 ωµ µ i + = λ 1 ωλ λ i + = --Shear elasticity and viscosity --volume elasticity and viscosity Oestreicher H.L. J. Acoust. Soc. Am. 3: , 1951.

22 Experimental Setup Laser vibrometer Water tank f Transducer Gel Block S. Chen, J. Greenleaf

23 Experimental Data (mm/s) 0.44mm 0.85mm 0.63&0.59m m Four spheres in Gel: Radius=0.85, 0.63, 0.59, 0.44 mm µ = 4kPa µ = 0. 08Pa s 1 S. Chen, J. Greenleaf

24 Can We Quantitate Tissue Properties Without A Scatterer?

25 Homogeneous Model x x t x F u t C t u = + ν x Transduce r r ( ) [ ] β β ν β ν β β β β β ρ α α d c t Sin c r J f a Exp e c I a V t t x x Ω Ω Ω Ω + Ω Ω = Ω tan ) ( ) ( ) ( /8 A.P. Sarvazyan. Et al. Ultrasound in Med. & Biol. 4: , 1998.

26 MRI Experiment for Measurement of Shear Wave Produced by Radiation Force in Homogeneous Material Surface coil Magnet Bore Shear waves Phantom Water tank FUS transducer 8 cm 10 cm S. Chen, T. Wu, J. Greenleaf

27 Experimental Data µ = kpa µ = 0. 5 Pa s S. Chen, T. Wu, J. Greenleaf

28 Can we make quantitative measurements in tissue with shear waves?

29 Background Shear wave speed dispersion: (Voigt model) c s = ( µ + ω µ ) ( ) + µ + ω µ ρ µ µ 1 : shear modulus?: density µ : shear viscosity? : frequency Y. Yamakoshi, J. Sato, and T. Sato, IEEE. Trans. UFFC., 37: 45-53, 1990.

30 Background (cont.) Shear wave speed dispersion: ( µ + ω µ ) ( ) + µ + ω µ ρ µ Single frequency methods: Time of flight A.P. Sarvazyan et al., Ultrasound in Med. & Biol. 4: Magnetic Resonance Elastography (MRE) R. Muthupillai, Lomas, Greenleaf, Ehman, Science, c s = 1 1 1

31 Shear Speed Simulation µ = 1. 0Pa s µ = 5 1 kpa

32 Proposed Method Transducer AM Input Detection Points? r c s ( ω) ω r = φ φ 1 Force? Viscoelastic Medium F 1 F? ( µ + ω µ ) c s = ( ) + µ + ω µ ρ µ 1 1 1

33 Experimental Setup Laser Vibrometer Water tank Micro-mirror Transducer Phantom Lock-in Amplifier Phase f Reference Modulation AM Input ~ ~ cos? L t cos? 0 t

34 Experimental Data 1 Chen, Greenleaf

35 Experimental Data Chen, Greenleaf

36 Conclusion for Tissue Shear Waves Shear speed dispersion can be used to quantify shear modulus and viscosity of a medium. Phase delay can be used to measure shear wave speed. Reality Piecewise homogeneous assumption Must use pulse-echo ultrasound to detect tissue motion

37 These have been point measurements of properties: Can we make quantitative images of, say, density?

38 Theory of Spheres in Viscoelastic Medium Dynamic radiation force on a sphere (( ) ) F = πay E cos ω ω t d 0 1 Y: Radiation force function for sphere a: Radius of sphere Velocity V = Z r F + d Z m

39 Theory of Spheres in Viscoelastic Medium Z r 3i 3 i 1 ak ah ah ah ah aki 1 π a + = i ρ ω 3 i 1 ak ak + ah ah + aki+ 1 aki + 1 ( ) h = ρ ω µ k = ρ ω µ + λ λ = λ1+ i ωλ µ = µ 1+ i ωµ Z r : Radiation impedance λ 1 : Bulk elasticity ~ 10 9 Pa λ : Bulk viscosity ~ 0 Pa s µ 1 : Shear elasticity ~10 4 Pa µ : Shear viscosity ~ 10 - Pa s i ωt dve F = m = im ωve dt i ωt 3 F 4π a Zm = = im ω = iρ i t s ω Ve ω 3 Z m : Mechanical impedance ρ s : Density of sphere

40 Simulation Results Acrylic: 1190 kg/m 3, Soda lime glass: 468 kg/m 3, Silicon nitride: 310 kg/m 3, 440-C stainless steel: 7840 kg/m 3, Brass: 8467 kg/m 3 a = mm µ 1 = 6.7 x 10 3 Pa µ = 0.5 Pa s λ 1 = 10 9 Pa λ = 0 Pa s

41 Experimental Setup Signal Generator 1 Signal Generator Power Amplifier A A f 0 - Df/ f 0 + Df/ Confocal Ultrasound Transducer Gelatin Phantom Laser Vibrometer Mixer Low-pass Filter Df Reference Lock-in Amplifier

42 Measurement Results a = 0.80 mm

43 Imaging Results Df = 700 Hz Acrylic Glass Silicon Nitride Stainless Steel Brass Normalized Scale Acrylic Glass Silicon Nitride Stainless Steel Brass Degrees a = 0.80 mm

44 Imaging Arteries In Vivo with VA

45 Experiment for In Vivo Pig Experiment

46 Normal Right Femoral Artery with Catheter and Guide Wire: pig b cm C. Pislaru, J. Greenleaf

47 Images of normal and artificially calcified femoral artery in pig Normal Calcified Zhang, Pislaru, Greenleaf

48 Calcification within femoral artery of pig Zhang, Pislaru, Greenleaf

49 Summary of Vessel Imaging Images are high resolution Images are high contrast Calcification can be detected Images are not quantitative

50 Can we make quantitative measurements in vessels with shear waves?

51 Use of Ultrasound Excited Shear Wave Propagate shear wave from radiation force site on vessel wall. Measure phase and group velocity dispersion. Solve for complex shear modulus given relevant model.

52 Mode Excitation in Vessel Ultrasound Transducer Laser Velocimeter or Doppler Wave Modes Pulse Bending Vessel Torsion t

53 Pig Femoral Artery Embedded in Gelatin Hz Drive Point J. Zhang, R. Kinnick, C. Pislaru, J. Greenlea

54 Phase and Amplitude from Arterial Wall Motion Φ(x) c m F=100Hz A(x) F = 00Hz F = 400 Hz Optical and vibrometry image J. Zhang, R. Kinnick, C. Pislaru, J. Greenlea

55 Pulse wave velocity without gelatin The pulse wave velocity is 10 mm / 1.78 ms = 5.6 m/s

56 Pulse wave velocity with gelatin The pulse wave velocity is 5 mm / 0.5 ms = 10 m/s

57 Another mode for quantitative measurement of vessel wall mechanical properties with ring resonance

58 Ring Resonant Frequency Method No longitudinal movement Motion is in the circumferential and radial direction The artery tube vibrates like a ring The ring resonance can be used to estimate arterial circumferential elastic modulus. Transducer Tissue Artery λ=πd d

59 A typical experimental setup Artery in gelatin Confocal ultrasound transducer Laser Vibrometer Doppler ultrasound transducer

60 Ring resonant frequency f t the torsion frequency ft f b f b the breathing frequency

61 Modulus estimation Estimation with the torsion resonant frequency, E = 3 ρπ ( Df t ) f t = 356 Hz, E C1 = 135 kpa. Estimation with the breath resonant frequency, E = 3 ρπ ( Df b ) /4 f b = 718 Hz, E C = 137 kpa. Mass density 1000 kg/m 3, Poisson s ratio 0.5, outer diameter 6 mm

62 In Vivo Pig Experiment Attach water bath to leg. Place Confocal Transducer in water focused on artery. Measure motion of artery with Doppler transducer.

63 In vivo pig femoral artery measurements Experimental setup

64 Conclusion for Ring Waves 1. Three ring resonant modes are identified for estimation of the elastic modulus of arterial wall.. The estimation only requires the diameter, but not the thickness, which is difficult to measure. 3. The PWV method needs both the diameter and thickness. 4. These modes contain basically local or cross sectional information of the artery. 5. Local elastic modulus can be estimated. HOWEVER

65 Reality Vessel modulus is nonlinear Some recent methods address this problem Vessel modulus is anisotropic Different resonances and propagation modes depend on different moduli Vessel modulus is complex Frequency dispersion may address viscosity

66 Vessel Imaging Conclusions Vessels can be seen in soft tissue. Appropriate intensities can be used in vivo. Images are high signal to noise and free of speckle. Material property of vessels may be measured

67 Overall Conclusions Radiation force can be used for many applications requiring non-invasive, contact-free, mechanical property analysis. Imaging is currently qualitative although with high resolution and no speckle. Quantitative measurement of material properties can be made through analysis of induced shear waves. Modal vibration analysis can be used for quantitative measurement of mechanical properties in piecewise homogeneous tissue and in mechanical parts.

68 Ultrasound Research Lab Mambi Medzivere Miguel Bernal Lizette Warner Mathew Urban Shigao Chen Xiaoming Zhang Heather Argadine Glauber Silva Farid Mitri Julie Patterson Randy Kinnick Tom Kinter Jennifer Milliken James Greenleaf Cristina Pislaru Mostafa Fatemi Azra Alizad

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