A Dual Defocused Camera System For Reconstructing the Cardiac Z-axis Vibrations

Area of Science:

• Biomedical Engineering
• Cardiovascular Physiology
• Medical Imaging

Background:

• Regular cardiac monitoring is crucial for early detection of cardiovascular diseases and chronic disease management.
• Current video-based seismocardiography (SCG) methods using defocused speckle imaging often yield signals contaminated with gyrocardiography (GCG) components.
• Accurate SCG signal extraction is vital for reliable cardiac health assessment.

Purpose of the Study:

• To investigate the feasibility of using two cameras with different defocus levels to reconstruct a pure cardiac Z-axis vibration signal (true SCG).
• To assess the accuracy of the reconstructed SCG signals compared to a reference accelerometer.
• To evaluate the performance of the reconstructed SCG in detecting key cardiac biomarkers.

Main Methods:

• Utilized two cameras with varying defocus levels to capture speckle motion signals.
• Reconstructed SCG signals from the captured data.
• Compared reconstructed SCG signals and raw speckle motion signals against a chest-mounted accelerometer reference.
• Assessed waveform similarity and accuracy of cardiac biomarker detection (AO/AC, MO/MC, IM).

Main Results:

• The reconstructed SCG signals demonstrated higher Pearson correlation (r=0.822) with the reference accelerometer signal.
• Biomarker detection accuracies with a 6 ms error range were high: 99.43% (AO/AC), 71.83% (MO/MC), 69.49% (IM), 69.30% (overall), and 81.50% (specific metric).
• Preliminary results from 10 subjects under ice pack stimulation validated the method's effectiveness.

Conclusions:

• The proposed method effectively reconstructs a pure SCG signal using two defocused cameras with different focal lengths.
• This technique offers significant potential for improved SCG-based cardiac monitoring and health management.
• Further validation is warranted, but the findings provide a promising advancement in non-invasive cardiac assessment.