Imaging pathologic pulmonary air and fluid accumulation by functional and absolute EIT

Area of Science:

• Medical Imaging
• Physiology
• Biomedical Engineering

Background:

• Electrical Impedance Tomography (EIT) is increasingly used in clinical research for critically ill lung patients.
• Pathologic impedance distributions from air or fluid accumulation can affect EIT tomogram validity.
• Non-linearities in imaging problems arise from conditions like pneumothorax, emphysema, haematothorax, and atelectases.

Purpose of the Study:

• To clarify the influence of pathologic impedance distributions on EIT tomogram validity in lung imaging.
• To assess the reliability of functional EIT (f-EIT) and absolute EIT (a-EIT) in detecting pleural abnormalities.
• To compare EIT findings with CT scans and healthy volunteer data in intensive care patients.

Main Methods:

• Investigated stepwise air and Ringer solution instillation into the pleural space of pigs.
• Generated EIT images using a modified Sheffield back projection algorithm for f-EIT.
• Applied a modified simultaneous iterative reconstruction technique (SIRT) for absolute resistivity quantification (a-EIT).
• Applied f-EIT and a-EIT to intensive care patients and compared results with CT and healthy volunteer data.

Main Results:

• f-EIT using back projection was not significantly disturbed by artificial pneumothorax or haematothorax in the animal model.
• SIRT enabled reliable discrimination and detection of the location and amplitude of pneumothorax and haematothorax.
• EIT results in patients showed good agreement with CT scans.
• Significant differences in regional resistivity were found between patients and healthy volunteers.

Conclusions:

• EIT, particularly with SIRT, reliably detects and quantifies pleural air and fluid accumulation in lung imaging.
• EIT provides a valuable, non-invasive tool for assessing lung conditions in critically ill patients.
• The findings support the clinical utility of EIT in managing inhomogeneous lung conditions.