Electrical Impedance Tomography

Electrical Impedance Tomography (EIT) is a non-invasive imaging technique used to create images of the conductivity or impedance of a part of the body. It is based on the principle that different tissues in the body have different electrical properties. By applying small electrical currents through electrodes placed on the skin and measuring the resulting voltages, EIT can reconstruct images of the internal conductivity distribution. This technique has applications in various medical fields, including pulmonology, neurology, and breast imaging.

Overview

Electrical Impedance Tomography operates by applying small alternating currents via a set of surface electrodes placed around the periphery of the body region of interest. The electrical conductivity and permittivity of tissues cause voltage differences, which are measured by the same or a different set of electrodes. These measurements are then used to reconstruct an image of the electrical impedance of the tissues, using algorithms that solve the inverse problem.

Applications

EIT is particularly useful in monitoring lung function and has been explored for its potential in diagnosing and managing conditions such as acute respiratory distress syndrome (ARDS) and pulmonary edema. It offers a real-time, bedside method for observing lung ventilation and perfusion without the need for radiation, making it an attractive option for continuous monitoring.

In neurology, EIT has been investigated for detecting cerebral ischemia and hemorrhage, providing a potential tool for the early detection of stroke and monitoring of brain function during surgery.

Breast imaging is another area where EIT is being explored, offering a non-invasive and radiation-free method for detecting breast cancer and monitoring treatment efficacy.

Advantages and Limitations

The main advantages of EIT include its non-invasiveness, absence of ionizing radiation, and potential for continuous monitoring. However, the technique also faces several limitations. The resolution of EIT images is lower compared to other imaging modalities like CT or MRI, and the quality of the reconstruction can be affected by the placement of electrodes and the homogeneity of the body region being imaged.

Technical Aspects

The quality of EIT images depends on several factors, including the number and placement of electrodes, the frequency of the applied current, and the algorithms used for image reconstruction. Advances in electrode design, imaging algorithms, and hardware are ongoing to improve the resolution and accuracy of EIT.

Future Directions

Research in EIT is focused on enhancing image quality, expanding its applications, and integrating it with other imaging modalities. There is also interest in developing portable EIT systems for use in various clinical settings, including intensive care units and emergency departments.

See Also

• Medical imaging
• Tomography
• Electrical conductivity
• Inverse problem