Graph Image Language Techniques Supporting Advanced Classification and Cognitive Interpretation of CT Coronary Vessel Visualizations - Computational Intelligence Paradigms in Advanced Pattern Classification - page 97

the morphology of the examined arteries. This is an indisputable advantage of
computed tomography over other diagnostic methods for acquiring these types of
images, in which one cannot avoid using advanced techniques for segmenting the
acquired images, and those may still contain fewer details and be of worse quality
in the end. The heart vascularisation reconstructions analysed here were acquired
using a SOMATOM CT scanner [4]. This apparatus offers a number of functional-
ities for data acquisition and creating 3D reconstructions on its basis. It also has
predefined procedures built in, which allow vascularisation to be quickly extracted
from the visible structures of the cardiac muscle.
Since image data has been saved in the form of animations showing coronary
vessels in various projections, for the further analysis we should select the appro-
priate projection which will show the examined coronary vessels in the most
transparent form most convenient for describing and interpreting. In our research
we have attempted to automate the procedure of finding such a projection by using
selected geometric transformations during image processing. Using the fact that
the spatial layout of an object can be determined by projecting it onto the axes of
the Carthesian coordinate system, values of horizontal Feret diameters [19], which
are a measure of the horizontal extent of the diagnosed coronary artery tree, are
calculated for every subsequent animation frame during the image rotation
(fig. 5.).
Fig. 5 The projection of the coronary arteries with the longest Feret diameter, obtained
from an animation stored in the MPEG4 format
The projection for which the horizontal Feret diameter is the greatest is selected
for further analyses, as this visualisation shows both the right and the left coronary
artery in the most convenient take. In a small number of analysed images, regard-
less of selecting the projection with the longest horizontal Feret diameter, vessels
may obscure one another in space, which causes a problem at subsequent stages of
the analysis. The best method to avoid this would be to use advanced techniques