Introduction Theory Methods Experiments Results Application Summary Dr. Heiko Maaß Institut für Angewandte Informatik Noninvasive Measurement of Elastic Properties of Living Tissue Forschungszentrum Karlsruhe Technik und Umwelt

Introduction Theory Methods Experiments Results Application Summary Quantitative evaluation of diagnostical results Quantification of tissue mechanics Monitoring of healing processes Mechanical properties in medicine Detection of hardenings or softenings (palpation) Introduction

Theory Methods Experiments Results Application Summary The 'Karlsruhe Endoscopic Trainer' simulation of elastic tissue product design biophysics accident research Application of mechanical tissue parameters Introduction

Theory Methods Experiments Results Application Summary Elastography Sonoelastic Imaging Strain Imaging Magnetic Resonance Elastography State of the art Hz vibration deformation measurement using Ultrasound or MR-tomography Introduction

Theory Methods Experiments Results Application Summary Theory Christoffel-equation: restricted to soft tissue (no bone or cartilage) Phenomenological model general approach

Introduction Theory Methods Experiments Results Application Summary incompressible non-linear anisotrop viscous temperature dependent inhomogeneous plastic Theory dependent on metabolism, innervation and perfusion liver 1mm Mechanical properties of biological tissue

Introduction Theory Methods Experiments Results Application Summary Theory skin fat liver heart muscle 10µm 1µm Histology

Introduction Theory Methods Experiments Results Application Summary Theory Acoustical properties of biological tissue velocity of sound damping a: penetration depth b: lateral resolution c: axial resolution soft tissuebone, cartilagegases m/s penetration depth in cm resolution in mm sound frequency in MHz  ~ f a b c

Introduction Theory Methods Experiments Results Application Summary Theory purely longitudinal wave purely transversal wave propagation direction bulk wave Acoutsical methods of testing conductancereflection penetration continuousimpulses - damping - interferences - dispersion - propagation time measurements

Introduction Theory Methods Experiments Results Application Summary Methods tt ss Non-invasive testing principle

Introduction Theory Methods Experiments Results Application Summary Methods Simulation of the propagation of ultrasound waves

Introduction Theory Methods Experiments Results Application Summary Methods Screen shots of the ultrasound simulation

Introduction Theory Methods Experiments Results Application Summary Methods ultrasound device tomographical system graphic workstation position sensing system ultrasound head coupled with position sensor interaction Assembly used for the non-invasive measurement

Introduction Theory Methods Experiments Results Application Summary Experiments image overlay liver spatial orientation Performance of the sound speed measurement

Introduction Theory Methods Experiments Results Application Summary Experiments F US Pos F C = 1540 m/s   Testing devices

Introduction Theory Methods Experiments Results Application Summary Results compressive strain  d compressive stress in MPa compressive strain  d compressive stress in MPa Evaluation of the experimental series regression analysis 2: parametric regression 3: general regression 1: origin tangential gradient correlation analysis

Introduction Theory Methods Experiments Results Application Summary Results Resulting curves compression test: heart muscle Compression test: kidney tension test: muscle, detailtension test: muscle (stationary)(mobile) strain compressive strain stress in N/mm²

Introduction Theory Methods Experiments Results Application Summary Results sound speed in m/s origin tangent E U in MPa liver tissue Correlation analysis results  2 = 1,2 E P  d (1 _ 3  d + 17  d 2 ) sound speed in m/s parameter E P in MPa  1 = E U  d origin tangent parametric regression series intra vitam series post mortem

Introduction Theory Methods Experiments Results Application Summary Results sound speed in m/s a 1 in MPa Correlation analysis results II sound speed in m/s general regression sound speed in m/s a 2 /a 1 a 3 /a 1 series intra vitam series post mortem liver tissue

Introduction Theory Methods Experiments Results Application Summary Results Graphical correlation analysis liver heart musclekidney spleenfat Abscissa: sound speed in m/s Ordinate: gradient of the origin tangent in MPa series intra vitam series post mortem

Introduction Theory Methods Experiments Results Application Summary origin gradient in MPa (compression) 00,10,20,30,40,50,60,70,8 Results sound speed in m/s fat (soft) fat (harder) liver spleen heart muscle kidney fat liver spleen kidney post mortem intra vitam Ranges of sound speed and origin gradient

Introduction Theory Methods Experiments Results Application Summary Results Results of the measurements on human biceps Compression test on human biceps in vivo sound speed in m/s origin tangent in MPa tensed bicepsrelaxed biceps

Introduction Theory Methods Experiments Results Application Summary Application stress  strain  t 0,51,00 tension compression -0,5 -1,0 F(s) Simulation of soft biological tissue

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

Introduction Theory Methods Experiments Results Application Summary Thank you for paying attention