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Noninvasive Measurement of Elastic Properties of Living Tissue

Noninvasive Measurement of Elastic Properties of Living Tissue. Forschungszentrum Karlsruhe Technik und Umwelt. Institut für Angewandte Informatik. Dr. Heiko Maaß. Mechanical properties in medicine. Introduction. Quantification of tissue mechanics.

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Noninvasive Measurement of Elastic Properties of Living Tissue

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  1. Noninvasive Measurementof Elastic Propertiesof Living Tissue Forschungszentrum KarlsruheTechnik und Umwelt Institut für Angewandte Informatik Dr. Heiko Maaß

  2. Mechanical properties in medicine Introduction • Quantification of tissue mechanics • Quantitative evaluation of diagnostical results • Monitoring of healing processes • Detection of hardenings or softenings (palpation)

  3. Application of mechanical tissue parameters Introduction • simulation of elastic tissue The 'Karlsruhe Endoscopic Trainer' • accident research • product design • biophysics

  4. State of the art Introduction vibration • Elastography 10-1000 Hz • Sonoelastic Imaging • Strain Imaging deformation • Magnetic Resonance Elastography measurement using Ultrasound or MR-tomography

  5. Phenomenological model Christoffel-equation: Theory general approach restricted to soft tissue (no bone or cartilage)

  6. Mechanical properties of biological tissue • non-linear • inhomogeneous Theory • anisotrop • plastic • viscous • incompressible • temperature dependent • dependent on metabolism, • innervation and perfusion liver 1mm

  7. Acoustical properties of biological tissue velocity of sound 0 1000 3000 m/s 2000 4000 Theory gases soft tissue bone, cartilage damping a  ~ f a: penetration depth b resolution in mm penetration depth in cm b: lateral resolution c c: axial resolution sound frequency in MHz

  8. Non-invasive testing principle s t Methods

  9. Testing devices US F F Pos  C = 1540 m/s  Experiments

  10. Evaluation of the experimental series regression analysis 3 2 1: origin tangential gradient 1 compressive stress in MPa 2: parametric regression compressive strain d 3: general regression Results compressive stress in MPa correlation analysis compressive strain d

  11. Ranges of sound speed and origin gradient origin gradient in MPa (compression) 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 fat (soft) fat (harder) liver spleen heart muscle post mortem kidney Results fat intra vitam liver spleen kidney 1400 1420 1440 1460 1480 1500 1520 1540 1560 1580 1600 sound speed in m/s

  12. Simulation of soft biological tissue F(s) tension stress  -0,5 -1,0 0 0,5 1,0 Application strain t compression

  13. Summary • Development and employment of testing devices • Measurement of tissue parameters intra vitam • Comparison to tisssue properties post mortem • Simulation of the propagation of sound • Non-invasive differenciation of fat is possible • Curve shapes are specific to the tissue kind • Curves are independent on stress velocity • Phenomenological model is not quantifiable • Usage of curve approximations in complex simulations • Development of new non-invasive methods of testing

  14. Thank you for paying attention

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