Electrodermal Imaging System (EDIS)

We are currently investigating the feasibility of a new body imaging technique based on skin surface electrical potentials and developing apparatus for this purpose. For more in-depth coverage of the background and system see what is E-DIS?

It has been known for centuries that the body produces electrical voltages and that the potentials can be measured on the external surface. Many specialised electrophysiological diagnostic tests have been established for a long time and are routinely used in hospitals clinically to aid doctors in identifying what is happening in the heart (ECG), the brain (EEG) and various muscles (EMG). Other more specific electrical tests have also been developed and are regularly in clinical use.

All the clinical electrophysiological tests focus on a particular organ or entity and very often the voltage at a single location is measured and recorded for later analysis and diagnosis. At times a cluster of electrodes around a specific region is used to obtain the necessary data.

The new system and technique being explored is a mapping method, systematically measuring skin potentials at many points over the body and displaying the results as an image rather than the conventional graphical presentation encountered in the existing diagnostic tests.

The image below shows the results from a very early study of electrical activity measured on the back of a subject.

Distinguishable shapes are noticeable in areas where one would expect the heart and lungs to be, over several measuring sessions similar features are observed.

The colour-coded scale to the right shows the colour representing the measured voltage ranging from minimum to maximum observed value as shown at the bottom along with the average voltage measurement.

There is some variation in raw voltage measurements that causes blurring; a degree of smoothing is applied to aid clarity.

This system is based on a resolution of over 10mm square gave some very encouraging and interesting results and led to development of the ‘mark 2’ version.

E-DIS 2 is still very much manually intensive and requires a single but preliminary measuring, marking and imaging session to manually create the empty data files.

The method can be considered as three separate stages:

  • Preliminary preparation

    Anatomical landmarks in the region(s) under investigation are identified and marked. Reference lines are added and measurements of distances are made.

    Next, digital images are taken and scaled images on a computer are generated to which grid-lines are added.

    This information is then transformed into a data file containing a set of empty cells arranged as a map of the body region(s). The image to the right shows a typical prepared image file.

  • Measurement and recording

    After the introductory groundwork has been completed, the skin of the region under investigation is cleaned and made ready for electrical measurements. Anatomical reference marks and lines identified previously are drawn on to the skin surface to aid location and positioning of the measuring electrode. Conductive gel is next applied to a small area of the skin and systematic electrical potential measurements are commenced with specially designed instrumentation; the value at each point being transferred to the previously prepared blank computer data file semi-automatically.

  • Processing and display presentation

    After all measurements are complete, the now filled data file is further modified and input to specially written software that processes the data and produces one of several image files like that shown near the beginning of this page. The software is able to process the data and colorize the cells either on an absolute basis or a relative one based on minimum and maximum values. In addition to generating maps of raw, measured voltage, it can also provide outputs of deviation from the mean value and there is also the facility to output differences between two files and to create an average map over several files. The software also permits a variable degree of smoothing to be applied to the values to enhance features in the plots and also calculates and displays basic statistical information about the data.

E-DIS 2 allowed us to test some dedicated instrumentation and explore some more of the potential of this modality, see the results for further detail.

Although we still use this version it is limited to 10mm square resolution however it does provide a useful benchmark for other equipment and technique development. It also enables us to explore the capabilities and limitations of biopotential measurement in this way whilst further developing the technology.

Although all areas are still under development and improvement to enhance this exciting and novel imaging system, we have a level of confidence with the instrumentation that enables us now to put more focus on exploring the capabilities of the possible applications. This does not mean we are ceasing development of the technology, on the contrary we have just completed a much-improved version – E-DIS 3 and are working on improvements and enhancements of results presentation.

E-DIS 3 eliminates the lengthy preliminary and manual preparations, whilst also increasing the resolution potentially to 1mm squares and reducing scanning time by about a factor of four for 10mm resolution. It also provides some enhanced dedicated software that will enable us to explore the most suited means of processing and presenting the resulting images. This updated version has just been completed and is ready for performance confirmation and evaluation; once this stage is complete we will move on, investing the following aspects of the technique to identify limitations and to establish the universality of the system:

For all these aspect we require subjects to assist with the program. If you are interested and want to know more, then please read the further information and complete the online form to register.

Click here for further information.