Wahle A, Prause GPM, von Birgelen C, Erbel R, Sonka M:


Automated Calculation of the Axial Orientation of Intravascular Ultrasound Images by Fusion with Biplane Angiography.

In:

Hanson KM (ed):

Medical Imaging 1999: Image Processing.

SPIE Proceedings

Volume 3661, Page 1094-1104, 1999

Comprehensive paper about the automated determination of the absolute orientation of the IVUS frames, preliminary in-vivo results (Journal) (Paper) (Poster) (Images) (Links)

Abstract: This paper presents an approach for fusion of the two major cardiovascular imaging modalities, angiography and intravascular ultrasound (IVUS). While the path of the IVUS catheter, which follows the vessel curvature during pullback, is reconstructed from biplane angiograms, cross-sectional information about the vessel is derived from IVUS. However, after mapping of the IVUS frames into their correct 3-D locations along the catheter path, their orientations remain ambiguous. We determine the relative catheter twisting analytically, followed by a statistical method for finding the absolute orientation from the out-of-center position of the IVUS catheter. Our results as obtained from studies with cadaveric pig hearts and from three patients undergoing routine coronary intervention showed a good match of the absolute orientation by the algorithm. In all tested cases, the method determined the visually correct orientations of the IVUS frames. Local distortions were reliably identified and discarded.

First, the 2-D catheter path and vessel outline are extracted from both angiograms and then reconstructed to a 3-D model. From the 3-D catheter path, the relative catheter twist can be estimated and serves as a basis for the relation between adjacent IVUS frames. The lumen is segmented in both IVUS image data and angiograms, where the angiographic lumen is represented in 3-D by elliptical contours derived from the 2-D outlines. In both data sets, the out-of-center position of the imaging catheter relative to the lumen is determined. Then, the IVUS data is mapped into 3-D using an initial orientation along with the relative twist. For each frame location, the out-of-center strength and the difference angles of angiographic vs. IVUS reconstruction are determined. Within a moving window of arbitrary but fixed size, a statistical analysis is performed. A reliability weight is calculated for each location of the moving window, giving higher weight to locations with high out-of-center strength, and limiting those with a high standard deviation of the difference angle function, which is indicating local distortions. A single correction angle is determined and applied to all IVUS frames relative to the initial orientation.

Note: The poster associated with this contribution received a Honorable Mention Poster Award of the Image Processing Conference.