10-6-2015 delft university of technology abdominal wall vibration analysis for evaluation of...

18-04-23

DelftUniversity ofTechnology

Abdominal Wall Vibration Analysis for Evaluation of Biomechanical Properties and Physiological Diagnosis of Internal Abdomen

Final MSc presentation

Teunis Schuurman

Department of Precision and Microsystems Engineering

Supervisors:

Prof. Dr. Ir. Daniel Rixen

Dr. Jan-Willem Hinnen

Dr. Ir. Cees Swenne

Final MSc. presentation 2


Contents:

• Introduction;

• Measurement setup;

• Data processing techniques;

• Results;

• Conclusion;

• Future Work & recommendations.

Introduction

Meas. setup

Data proc.

techn.

Results

Conclusion

Future Work &

recommendatio

ns


Introduction

Introduction

Meas. setup

Data proc.

techn.

Results

Conclusion

Future Work &

recommendatio

ns


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 &

recommendatio

ns


Largest and most cramp human body cavity.

Contains stomach, liver, intestines, kidneys, abdominal aorta, vena cava, etc.

Organs suspended freely inperitoneum.

Accessible for physical Examination.

Human Abdomen

Introduction

Meas. setup

Data proc.

techn.

Results

Conclusion

Future Work &

recommendatio

ns


[1] http://en.wiktionary.org, 2011 [2] Ferguson, 1990

Abdomen Examination Physical Examination

• 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]

Introduction

Meas. setup

Data proc.

techn.

Results

Conclusion

Future Work &

recommendatio

ns


Abdomen Examination

Based on change in `feel’, identifying:

• Rigidities;• Unusual sliding friction;

• Unusual masses• pulsation sources

}mechanical properties

}dynamic properties

Introduction

Meas. setup

Data proc.

techn.

Results

Conclusion

Future Work &

recommendatio

ns


Influence on dynamics

Vibration: “Periodic process around an equilibrium position” [1]

Undamped:

Damped:

[1 http://en.wiktionary.org/, 2011

Introduction

Meas. setup

Data proc.

techn.

Results

Conclusion

Future Work &

recommendatio

ns

cos nx t A t

2cos 1ntdamped nx t Xe t

Amplitude

Frequency [rad/s]

Damping



Rigidity stiffness k Introduction

Meas. setup

Data proc.

techn.

Results

Conclusion

Future Work &

recommendatio

ns

m

k



Mass distribution mass m

Introduction

Meas. setup

Data proc.

techn.

Results

Conclusion

Future Work &

recommendatio

ns

m

k



Friction damping c Introduction

Meas. setup

Data proc.

techn.

Results

Conclusion

Future Work &

recommendatio

ns

m

k c



Excitation source x(t): forced vibrations

Transfer function

Introduction

Meas. setup

Data proc.

techn.

Results

Conclusion

Future Work &

recommendatio

ns

m

k c

x(t)

Y fH f

X f

y(t)


Abdominal Vibration systems

Abdominal cavity as a mechanical system

Introduction

Meas. setup

Data proc.

techn.

Results

Conclusion

Future Work &

recommendatio

ns


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]


• Excitation sources Introduction

Meas. setup

Data proc.

techn.

Results

Conclusion

Future Work &

recommendatio

ns [3] Dellinger et al, 2008 [4] Politzer, 1976[5] Son, 1993



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 &

recommendatio

ns


Measurement setup

Introduction

Meas. setup

Data proc. techn.

Results

Conclusion

Future Work &

recommendations


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


Single beam measurementOne beam = one measurement

Approximate parallel scan with triggered sequential scan

Abdominal Vibration measurementsMeasurement setup

Introduction

Meas. setup

Data proc. techn.

Results

Conclusion

Future Work &

recommendations

t = 1 t = 2t = 3 t = 4



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



Vibration pattern synchronizes with cardiac cycle Introduction

Meas. setup

Data proc. techn.

Results

Conclusion

Future Work &

recommendations


Data processing techniques

Introduction

Meas. setup

Data proc.

techn.

Results

Conclusion

Future Work &

recommendations


Instantanous Deflection Surface

Plot parallel approximation S(t): Introduction

Meas. setup

Data proc.

techn.

Results

Conclusion

Future Work &

recommendations


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


Frequency Response Function

Transfer function H(f) between input x(t) and output signal y(t)

Input: blood pressure waveform dP/dtOutput: velocity signal

Introduction

Meas. setup

Data proc.

techn.

Results

Conclusion

Future Work &

recommendations


Results

Introduction

Meas. setup

Data proc. techn.

Results

Conclusion

Future Work &

recommendations


Results

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

Introduction

Meas. setup

Data proc. techn.

Results

Conclusion

Future Work &

recommendations


Conclusion

Abdominal wall shows repeatable vibration patterns dominated by cardiac activity.

Introduction

Meas. setup

Data proc. techn.

Results

Conclusion

Future Work &

recommendations


Future work & recommendationsFuture work:

A patent application has filed yesterdayIf granted, expected TU will continue research.

Publication of article discussing results of research on short term.

Introduction

Meas. setup

Data proc. techn.

Results

Conclusion

Future Work &

recommendatio

ns


Future workRecommendations:

• 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

Introduction

Meas. setup

Data proc. techn.

Results

Conclusion

Future Work &

recommendatio

ns


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 &

recommendatio

ns


Thank you for your attention!


Frequency domain analysis

Identification of major frequency components Introduction

Meas. setup

Data proc.

techn.

Results

Conclusion

x t X fF

xxAPS X f X f


Frequency – time domain

Non-steady frequency analysis: Continous Wavelet Transform

Mexican hat Wavelet

Pseudo-freq


Frequency Response Function

Transfer function between input x(t) and output signal y(t)

1

yx

xx

CPS fH f

APS

1 1

1 1,

a aN N

xx yxxx yxn na a

APS APS CPS CPSN N


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


Respiration


Respiration

Organ motion


LDV operation principle


Signal quality


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


ECG monitorMuscle contract after small drop en rice of electric potential

on cell membranes;Heart contraction causes fluctuating electric fieldECG leads measures the changes

3 lead ECG

12 lead ECG


Spectral LeakageUsing sampling and discrete Fourier transform causes

spectral leakage

10-6-2015 delft university of technology abdominal wall vibration analysis for evaluation of...

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