AMBULANT SUBJECT SCG MONITORING WITH MEMS

ACCELEROMETERS

Chenxi Yang

Stevens Institute of Technology

Real Time Heart Rate Recording1

*Varady, Peter, et al. "An advanced method in fetal phonocardiography." Computer Methods and programs in Biomedicine 71.3 (2003): 283-296.

Long term heart rate is a valuable diagnostic measurement

Can detect potential disease

Different techniques show varies information from heart(e.g. :ECG(electrodes), PCG(sound) and SCG(Movement))

Seismocardiogram reflects the mechanical event of heart beat

Could be monitored by MEMS accelerometers

Used to be at rest to avoid noise

Non-invasive attachment near sternal

Heart Rate (FHR) Monitor2

*Chen, Jianfeng, et al. “Fetal heart signal monitoring with confidence factor.” IEEE International Conference on Multimedia and Expo, 2006.

Method Sensor Type Portability Disadvantage

Electrocardiography (ECG) Electrode MediumRely on proper position of

multiple electrodes

Phonocardiogram (PCG) Microphone MediumLimited miniaturization,High environment noise

Seismocardiograph (SCG) MEMS Accelerometers High Motion Artifacts

Comparison between common methods

TOP JOB: Cancelling motion artifact3

MEMS accelerometer is the best choice if motion artifact is cancelled Least preparation needed

Low-cost

Low-power

High-resolution low-noise MEMS accelerometers Wireless transmission possible due to small size

and low power consumption

More details for medical analysis

Provide other information(falling status, sleeping quality, acitivity) at the same-time

Adaptive filter DSP system4

1st• Low-pass filter to reduce high-frequency noise

2nd

• Adaptive Normalized LMS filter

• Pick periodic signal that is useful

3rd

• Peak detection to calculate interval and heart rate

• Ensemble average for medical analysis

Low-pass filter

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• Subject is firstly steady position and then moving

• Raw data from MEMS Accelerometer • Data after low-pass filtering

Normalized LMS adaptive filter

6

Peak Detection

7

Ensemble Average

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Comparison with standard SCG

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Comparison with same-time ECG recording

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Comparison with same-time ECG recording

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