Wahle A, Krauß U,
Oswald H, Fleck E:
Image Preprocessing
for 3-D Reconstruction from Biplane Angiograms.
18th Annual International Conference of
the IEEE Engineering in Medicine and Biology Society
(EMBS), Amsterdam NL, IEEE Press
Volume 2, Page 654-655, 1996/97
Image preprocessing for 3-D reconstruction from biplane
angiograms, especially concerning dynamic influences
of sigmoidal effects and contrast problems (Continued)
(Paper) (Images)
(Links)
Abstract:
The accuracies of systems for Quantitative Coronary
Angiography, as well as for 3-D reconstruction from
biplane angiograms, strongly depend on the quality
of the used image data. To complete our highly accurate
reconstruction system, we developed several methods
for equalizing gray value contrasts to enhance vessel
detection, and improved algorithms for elimination
of geometric image distortions. Conventional rectification
algorithms using a regular grid mostly neglect dynamic
influences like the magnetic field of the earth.
To avoid the necessity of determining the distortion
for each possible angulation individually, we rectify
by using a specific polynomial 
that is interpolated
from (at least) two extrema. In first studies the
rectification was sufficiently performed. Further
research involving all devices of the four cath labs
in German Heart Institute and Virchow-Klinikum is
still under way to obtain a reliable base for statistics.
The quality of the interpolated rectifications can
be determined by comparison of the derived polynomial
coefficients with those of the direct assessment
by using the grid image for a specific orientation.
Approximating the distortion patterns of a specific
orientation by interpolation from extrema is feasible
to provide sufficient accuracy for quantitative analyses
and 3-D reconstructions from angiograms. Since the
estimation of rectification data for each possible
angulation in each frame of time is not applicable
in clinical routine, we found a pragmatic solution
with minimum expense.