Abdominal Wall Vibration Analysis for Evaluation of Biomechanical

Abdominal Wall Vibration Analysis for Evaluation of Biomechanical Properties and Physiological Diagnosis of Internal Abdomen Final MSc presentation Teunis Schuurman Supervisors: Department of Precision and Microsystems Engineering Prof. Dr. Ir. Daniel Rixen 13 -6 -2021 Dr. Ir. Cees Swenne Delft University of Technology Dr. Jan-Willem Hinnen

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

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

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

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

Abdomen Examination Physical Examination • Palpation: Introduction “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] Meas. setup Data proc. techn. Results • Auscultation, listen for sounds Conclusion • Percussion: “ Future Work & “The tapping of the body to asses underlying structures” [1], [2] recommendations [1] http: //en. wiktionary. org, 2011 [2] Ferguson, 1990 Final MSc. presentation 7

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

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

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

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

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

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

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

Abdominal Vibration systems • Excitation sources Introduction Meas. setup Digestivecycle Respiration Cardiac track Data proc. techn. Bowel Amplitude Large Heartbeat sounds freq [1 – 2 Hz] Results [4] Hz] Peaking Low Expansion frequency above of heart; 100 [0. 1 Hz – 0. 2 Conclusion Respiratory Dilation of arteries sounds: [Abdominal [+ 150 Hz] [3] Aorta: 2 – 20 %][5] Future Work & recommendations [3] Dellinger et al, 2008 [4] Politzer, 1976 [5] Son, 1993 Final MSc. presentation 15

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

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

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

Abdominal Vibration measurements Measurement setup Single beam measurement Introduction One beam = one measurement Meas. setup Approximate parallel scan with triggered sequential scan Data proc. techn. Results Conclusion Future Work & recommendations t = 13 t = 24 Final MSc. presentation 19

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

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

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

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

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 Final MSc. presentation 24

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

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

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

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

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

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

Future work Recommendations: • Increase number of volunteers Introduction • 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 Meas. setup Data proc. techn. Results Conclusion Future Work & recommendations • increased pulse pressures, • reduction in artery stiffness • patient-specific anatomy? Final MSc. presentation 31

Thank you for your attention! Final MSc. presentation 32

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

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

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

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 Final MSc. presentation 36

Respiration Final MSc. presentation 37

Respiration Organ motion Final MSc. presentation 38

LDV operation principle Final MSc. presentation 39

Signal quality Final MSc. presentation 40

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

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 Final MSc. presentation 42

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

Spectral Leakage Using sampling and discrete Fourier transform causes spectral leakage • Rectangular window (blue) • Blackman-Harris (red) • Tukey (r = 0. 5) window (cyan) • Flat-Top (magenta) window • The Hann (green) window Final MSc. presentation 44