Determination of the absolute axial orientation of intracoronary ultrasound images in fusion with biplane angiography

While intravascular ultrasound (IVUS) gains increasing importance, assessment of spatial structures still lacks a geometrically correct 3D reconstruction. The IVUS frames are usually stacked up to form a straight vessel, neither considering any curvature nor the axial twisting of the catheter during the pullback. Quantification of this simplified data inevitably results in significantly distorted values. To solve this problem, the authors' approach assigns the results from IVUS segmentation to their geometrically correct spatial locations and orientations. One of the major tasks in this reconstruction is the determination of the axial rotation of the IVUS frames. This paper presents a new method to derive the absolute orientation of an IVUS frame set from the out-of-center location of the imaging catheter without any additional user interaction.