Teunis Schuurman Department of Precision and Microsystems Engineering

1. Abdominal Wall Vibration Analysis for Evaluation of Biomechanical Properties and Physiological Diagnosis of Internal AbdomenFinal MSc presentation Supervisors: Prof. Dr. Ir. Daniel Rixen Dr. Jan-Willem Hinnen Dr. Ir. Cees Swenne Teunis Schuurman Department of Precision and Microsystems Engineering

3. Contents: Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations • Introduction; • Measurement setup; • Data processing techniques; • Results; • Conclusion; • Future Work & recommendations.

4. Introduction Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations

5. Goal Evaluate the use of vibration analysis to assess the biomechanical properties of internal abdomen Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations

6. Human Abdomen Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations Largest and most cramp human body cavity. Contains stomach, liver, intestines, kidneys, abdominal aorta, vena cava, etc. Organs suspended freely in peritoneum. Accessible for physical Examination.

7. Abdomen Examination Physical Examination Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations • Palpation: • “Feeling or pushing to determine medical condition as the normality of organs or the presence or absence of tumors, swelling, muscle tension, etc” [1], [2] • Auscultation, listen for sounds • Percussion:“ • “The tapping of the body to asses underlying structures” [1], [2] [1] http://en.wiktionary.org, 2011 [2] Ferguson, 1990

8. Abdomen Examination Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations • Based on change in `feel’, identifying: • Rigidities; • Unusual sliding friction; • Unusual masses • pulsation sources } mechanical properties } dynamic properties

9. Influence on dynamics Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations • Vibration: • “Periodic process around an equilibrium position” [1] • Undamped: • Damped: Frequency [rad/s] Amplitude [1 http://en.wiktionary.org/, 2011 Damping

10. Influence on dynamics Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations • Rigidity  stiffness k m k

11. Influence on dynamics Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations Mass distribution  mass m m k

12. Influence on dynamics Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations Friction  damping c m c k

13. Influence on dynamics Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations Excitation source x(t): forced vibrations Transfer function y(t) m c k x(t)

14. Abdominal Vibration systems Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations Abdominal cavity as a mechanical system

15. Abdominal Vibration systems Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations • Excitation sources Digestive track Bowel sounds Peaking above 100 Hz [4] Respiration Large Amplitude Low frequency [0.1 – 0.2 Hz] Respiratory sounds: [+ 150 Hz] [3] Cardiac cycle Heartbeat freq [1 – 2 Hz] Expansion of heart; Dilation of arteries [Abdominal Aorta: 2 – 20 %][5] [3] Dellinger et al, 2008 [4] Politzer, 1976 [5] Son, 1993

16. Abdominal Vibration systems Summarized: Physiological Examination assesses mechanical properties; Mechanical properties influence dynamics Excitation sources present in abdomen, dynamics in abdomen expected Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations

17. Measurement setup Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations

18. Abdominal Vibration measurements Vibration measurement: Uses Doppler effect on light Easy Setup Large frequency & velocity range Velocity of surface less influenced by respiration. Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations

19. Single beam measurement One beam = one measurement Approximate parallel scan with triggered sequential scan Abdominal Vibration measurements Measurement setup Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations t = 1 t = 2 t = 3 t = 4

20. Abdominal Vibration measurements Measurement setup LDV measures skin velocity ECG monitor triggers on QRS complex Subject positioned supine to relax abdominal wall Reflective stickers to improve signal quality Some measurement performed with Finometer, measuring `input’ bloodpressure waveform Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations

21. Abdominal Vibration measurements Measurement setup Vibration pattern synchronizes with cardiac cycle Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations

22. Data processing techniques Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations

23. Instantanous Deflection Surface Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations Plot parallel approximation S(t):

24. Individual velocity profiles Plot individual velocity profiles and assess in regard to their position on the abdominal surface Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations

25. Frequency Response Function Transfer function H(f) between input x(t) and output signal y(t) Input: blood pressure waveform dP/dt Output: velocity signal Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations

26. Results Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations

27. Results Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations Vibration of abdominal wall contains repeatable patterns in synchronization with cardiac cycle; LDV is able to detect them, using an ECG as trigger and retro-reflective stickers to improve returned signal power; Clear pulsation shown above Abdominal Aorta, other locations more complex

28. Conclusion Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations Abdominal wall shows repeatable vibration patterns dominated by cardiac activity.

29. Future work & recommendationsFuture work: Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations A patent application has filed yesterday If granted, expected TU will continue research. Publication of article discussing results of research on short term.

30. Future workRecommendations: Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations • Implement respiration tracking • Improve reflection • reflective clothing, non-health risky spray coatings) • Use light frequencies with improved reflection properties • Implement parallel scanning • Multi-beam LDV systems, photogrammetry

31. Future workRecommendations: Increase number of volunteers Check for inter-patient variability; Observe intra-patient variability in other subjects; Investigate origin of the more complex vibration profiles Increased velocity amplitudes observed in AAA patients increased pulse pressures, reduction in artery stiffness patient-specific anatomy? Introduction Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations

32. Thank you for your attention!

33. Frequency domain analysis Identification of major frequency components Introduction Meas. setup Data proc. techn. Results Conclusion

34. Frequency – time domain Non-steady frequency analysis: Continous Wavelet Transform Mexican hat Wavelet Pseudo-freq

35. Frequency Response Function Transfer function between input x(t) and output signal y(t)

36. Measurement methods Vibration measurements on abdominal wall Accelerometers [a] Photogrammetry [b] Laser Doppler Vibrometry [c] [a] www.sensorsmag.com, 2011 [b] www.gom.com, 2010 [c] www.polytec.de, 2010

37. Respiration

38. Respiration Organ motion

39. LDV operation principle

40. Signal quality

41. Reflective stickers • Air – skin: 4 – 7 % light reflection; • Epidermis: mostly transmitting, UV absorbed; • Dermis: 600 – 1300 nm penetrates deep back scattering due to micro-structures

42. ECG monitor Muscle contract after small drop en rice of electric potential on cell membranes; Heart contraction causes fluctuating electric field ECG leads measures the changes 3 lead ECG 12 lead ECG

43. Spectral Leakage Using sampling and discrete Fourier transform causes spectral leakage

44. Spectral Leakage Using sampling and discrete Fourier transform causes spectral leakage • Rectangular window (blue) • Tukey (r = 0.5) window (cyan) • The Hann (green) window • Blackman-Harris (red) window • Flat-Top (magenta) window