An Experimental Study on the Effect of the Anisotropic Regions in a Realistically Shaped Torso Phantom
Date
2008-07-04
Journal Title
Journal ISSN
Volume Title
Publisher
Annals of Biomedical Engineering
Abstract
Determination of electrically active regions in the
human body by observing generated bioelectric and/or
biomagnetic signals is known as source reconstruction. In
the reconstruction process, it is assumed that the volume
conductor consists of isotropic compartments and homoge neous tissue bioelectric parameters but this assumption
introduces errors when the tissue of interest is anisotropic.
The aim of this study was to investigate changes in the
measured signal strengths and the estimated positions and
orientations of current dipoles in a realistically shaped torso
phantom having a heart region built from single guar gum
skeins. Electric data were recorded with 60 electrodes on the
front of the chest and 195 sensors measured the magnetic
field 2 cm above the chest. The artificial rotating dipoles were
located underneath the anisotropic skeins distant from the
sensors. It was found that the signal strengths and estimated
dipole orientations were influenced by the anisotropy while
the estimated dipole positions were not significantly influ enced. The signal strength was reduced between 17% and
43% for the different dipole positions when comparing the
parallel alignment of dipole orientation and anisotropy
direction with the orthogonal alignment. The largest error
in the estimation of dipole orientation was 42 degrees. The
observed changes in the magnetic fields and electric poten tials can be explained by the fact that the anisotropic skeins
force the current along its direction. We conclude that taking
into account anisotropic structures in the volume conductor
might improve signal analysis as well as source strength and
orientation estimations for bioelectric and biomagnetic
investigations.