Phasic three-dimensional impedance imaging of cardiac activity

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Physiological Monitoring

Background:

• Electrical impedance imaging (EII) offers a non-invasive method for visualizing internal body structures.
• Previous work established vertical resolution in EII using multi-layered electrodes.
• Understanding spatio-temporal conductivity changes is crucial for diagnosing thoracic conditions.

Purpose of the Study:

• To demonstrate the feasibility of obtaining physiologically relevant information from 3D EII of the chest.
• To investigate cephalo-caudal differences in thoracic conductivity during the cardiac cycle.
• To correlate observed conductivity changes with cardiac and pulmonary blood volume dynamics.

Main Methods:

• Utilized the ACT 3 instrument for simultaneous current application and voltage measurement across 32 electrodes.
• Developed a 3D reconstruction algorithm for cylindrical models with multi-layered electrodes.
• Applied four rows of eight hydrogel electrodes to the thorax of a human subject.
• Recorded impedance data during breath-holding to isolate cardiac activity.

Main Results:

• Phasic changes in electrical conductivity during the cardiac cycle differed significantly between heart and lung regions.
• During systole, anterior lower thoracic layers showed decreased conductivity, while upper layers exhibited increased conductivity.
• Cardiac activity was discernible across all electrode layers.
• Observed conductivity patterns align with known changes in heart and lung blood volume.

Conclusions:

• 3D electrical impedance imaging can produce real-time, physiologically interpretable images of the chest.
• Cephalo-caudal conductivity variations provide insights into cardiac and pulmonary function.
• This technique holds promise for non-invasive monitoring of thoracic physiological processes.