Modelling of the thorax as a volume conductor

Modelling of the human thorax as a volume conductor -

Brief tutorial and some examples
Modelling group at TUT:

Project leaders:

Prof. Jaakko Malmivuo
Assoc. prof. Hannu Eskola

Why modelling?

The models of the human body as a volume conductor are employed to learn the relationship between the measured biopotentials and the sources generating them. The simulations of the sources provide the forward solution. The inverse solution of the sources are based on the measured potentials and the forward solution obtained with the model. (see bioelectromagnetism)

Modelling tools

We have developed tools for construction of patient tailored volume conductor model of the human body (both head and thorax) from sectional images (CT, MR). The tools include tissue segmentation from the image data, model construction, field calculation and visualization of the anatomy and the measured or calculated fields. The computational model is based on the finite difference method providing easy formation of accurate anatomical models.

VHM model

One application of the tools has been the utilization of the Visible Human Man data for the basis of the model.
From the cryosectional images of the VHM project 118 slices were selected. These were converted to b/w 8 bit images for data storage and image processing. All tissues visible in these selected slices were segmented and a very accurate FDM model of the thorax was constructed.

Examples of visualized results:

Electric field generated in the thorax generated by energization of the standard ECG lead I (this is the lead field, e.g. sensitivity distribution of the lead I) (VHM model):

Effect of changing the tissue conductivity's by 10% (cases: all inhomogeneities, intracardial blood masses) (VHM model).:

Body surface potential maps generated by simulated ischemic injury sources (model based on MR images):