What Is Impedance Tomography?

by johnpeter
Impedance tomography

Impedance Tomography is a technique of measuring electrical impedance in the body. It was developed in 1983 by Barber and Brown. It uses the same principle as computed tomography. The technique involves superimposing 16 voltage profiles and using selective boundary filtering to remove artifacts. The result is a three-dimensional image that shows the patient’s impedance. Typically, the upper part of the image shows the ventral side of the patient and the lower part shows the right side.

Electrical impedance scanning

Electrical impedance scanning (EIT) is a non-invasive diagnostic imaging procedure that uses electrical currents to produce images of internal organs. It utilizes 16 or 32 electrodes placed around the thorax. The currents are transmitted through the thorax in a specific pattern, which depends on the shape and distribution of thoracic impedances. The images produced by EIT can be highly accurate, providing a map of lung function.

Reconstruction from absolute impedance measurements

The quality of the reconstruction of an EIT image depends on the electrodes and the method used to acquire them. The electrodes can be used in different ways to achieve the desired spatial resolution and improve the contrast of the image. For a good image reconstruction, electrodes must be placed properly and be accurate in their position. The electrode-body contact impedance needs to be modeled carefully. Another important factor is electrode adhesion.

Applications of Impedance Tomography

Impedance tomography is a type of electromagnetic imaging. It works by measuring the change in the resistance between two electrodes. The impedance of a particular fluid or tissue varies depending on the content of free ions. For example, muscle is much more conductive than blood or fat. Consequently, an image of the body is created by building up a series of these signals.

Requirements for accurate body shape

When using impedance tomography to map the human body, it is critical to obtain accurate body shape measurements. There are various requirements for the correct electrode placement in order to produce an accurate image of the body.

Requirements for exact position of electrodes

One of the requirements for the exact position of electrodes in impedance imaging is a uniform spacing. Informational blogs highlight that in impedance tomography, electrodes have a spacing of approximately 7 cm and can move laterally or distally if misplaced.

Requirements for FEM-based reconstruction

A numerical differential function (NDF) is a mathematical function that transforms a differential quotient into a difference scheme. This technique reduces the complexity of the problem by using a finite-element mesh. However, this method has some limitations, particularly in the case of curve-boundary problems. Furthermore, it is not suited for use in human tissue EIT.

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