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Ultrasonic Nonlinear Imaging- Tissue Harmonic Imaging

Explore advanced methods in ultrasonic imaging to improve image quality and diagnostic accuracy, specifically focusing on tissue harmonic imaging and nonlinear propagation. Learn about reducing imaging artifacts and motion compensation for clearer results in technically challenging bodies.

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Ultrasonic Nonlinear Imaging- Tissue Harmonic Imaging

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  1. Ultrasonic Nonlinear Imaging-Tissue Harmonic Imaging

  2. Tissue Nonlinear Imaging • Imaging based on nonlinear propagation in tissue. • Motivation: • Performance of ultrasound has been sub-optimal on technically difficult bodies. • Most recent new developments have bigger impact on technically satisfactory bodies. • Poor image quality leads to uncertainty in diagnosis and costly repeat examinations.

  3. Tissue Harmonic Imaging • Methods to improve image quality: • Different acoustic window. • Lower frequency. • Adaptive imaging. • Non-linear imaging (or harmonic imaging).

  4. Finite Amplitude Distortion Sound Velocity and Density Change Phase velocity Nonlinearity Particle velocity

  5. When Peak Pressure Is Very High Shock Wave

  6. Non-linear Parameter B/A • B/A defines non-linearity of the medium. The larger the B/A, the higher the non-linear response.

  7. B/A Parameters: Typical Values • Typical values: • Water:5.5+/-0.3. • Liver: 7.23. • Fat: 10.9. • Muscle: 7.5. • B/A imaging may be used for tissue characterization.

  8. transducer transducer Nonlinear Propagation

  9. Reduction of Imaging Artifacts

  10. Reduction of Imaging Artifacts

  11. Advantages of Tissue Harmonic Imaging • Low sidelobes. • Better spatial resolution compared to fundamental imaging at the original frequency. • Less affected by tissue inhomogeneities – better performance on technically difficult bodies.

  12. Non-linear Propagation: Numerical Analysis (1) • The frequency domain solution to Burgers’ equation: where b=1+B/(2A).

  13. Wave at distance z angular spectrum method Linear propagation to z+Dz frequency domain solution to Burgers’ equation Nonlinear propagation at z+Dz Non-linear Propagation

  14. Non-linear Propagation: Numerical Analysis (2) • KZK equation: diffraction loss quadratic nonlinearity

  15. Characteristics in Tissue

  16. Non-Linear Propagation

  17. Non-Linear Propagation

  18. Non-Linear Propagation One way Two way

  19. Non-Linear Propagation

  20. Nonlinear Propagation with Tissue Inhomogeneities

  21. Sidelobe Reduction in Inhomogeneous Tissue

  22. Requisite Field Amplitude

  23. Increasing Harmonic Generation by Multiple Transmit Focusing

  24. Harmonic Generation and Multiple Transmit Focusing

  25. Harmonic Generation and Multiple Transmit Focusing

  26. Pulse Bandwidth and Spectral Leakage

  27. Axial Resolution vs. Harmonic Separation

  28. Harmonic Leakage and Image Quality Degradation

  29. Harmonic Leakage and Pulse Types

  30. Harmonic Leakage and Bandwidth

  31. Harmonic Leakage and Tissue Inhomogeneities

  32. Harmonic Leakage from System Nonlinearity

  33. Harmonic Leakage and Pulse Inversion

  34. Harmonic Leakage and Pulse Inversion

  35. Motion Artifacts in Pulse Inversion Imaging

  36. Axial Motion

  37. Lateral Motion

  38. Motion Artifacts

  39. Motion Artifacts

  40. Motion Compensation

  41. Motion Compensation • It is relatively easy to compensate for axial motion, but how about lateral and elevational motion?

  42. Higher Order Nonlinear Imaging (Higher Order  Higher Harmonic)

  43. Amplitude-Encoded Pulse Sequence For a point target:

  44. Amplitude-Encoded Pulse Sequence

  45. Spectral Convolution

  46. Phase-Encoded Pulse Sequence 2-pulse 3-pulse

  47. More Clinical Examples

  48. Clinical Examples (1)

  49. Clinical Examples (2)

  50. Clinical Examples (3)

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