Assessment of obstruction length and optimal viewing angle from biplane X-ray angiograms

Abstract

Three-dimensional quantitative coronary angiography (3D QCA) has been encouraged by the increasing need to better assess vessel dimensions and geometry for interventional purposes. A novel 3D QCA system based on biplane X-ray angiograms is presented in this paper. By correcting for the isocenter offset and by improving the epipolar constraint for corresponding two angiographic projections, accurate and robust reconstruction of the vessel centerline is achieved and the reproducibility of its applications, e.g., the assessments of obstruction length and optimal viewing angle, is guaranteed. The accuracy and variability in assessing the obstruction length and optimal bifurcation viewing angle were investigated by using phantom experiments. The segment length assessed by 3D QCA correlated well with the true wire segment length (r (2) = 0.999) and the accuracy and precision were 0.04 +/- 0.25 mm (P < 0.01). 3D QCA slightly underestimated the rotation angle (difference: -1.5 degrees +/- 3.6 degrees , P < 0.01), while no significant difference was observed for the angulation angle (difference: -0.2 degrees +/- 2.4 degrees , P = 0.54). In conclusion, the new 3D QCA approach allows highly accurate and precise assessments of obstruction length and optimal viewing angle from X-ray angiography.

Fig. 1

3D biplane model with an isocenter offset

Fig. 2

Correspondence before correcting for the isocenter offset

Fig. 3

Correspondence after correcting for the isocenter offset

Fig. 4

Possible difficulties in corresponding two projection centerlines by using epipolar constraint

Fig. 5

Comparison of 3D QCA and 2D QCA in assessing obstruction length. Frontal image (top left) and lateral image (top right) are biplane data. Courtesy: Department of Cardiology, Leiden University Medical Center (LUMC), The Netherlands

Fig. 6

The definition of bifurcation main plane

Fig. 7

A biplane data: frontal image (left); lateral image (right). Courtesy: Department of Cardiology, Leiden University Medical Center (LUMC), The Netherlands

Fig. 8

The reconstructed bifurcation under the optimal viewing angle: LAO 52.0° and Caudal 20.1°

Fig. 9

Wire phantoms used in the validation study

Fig. 10

Determining the ground truth of optimal viewing angle by using the orthogonal iron sticks: left image (a) under RAO 4.0° and Cranial 40.0°; right image (b) under LAO 44.0° and Cranial 3.0°. The arrow indicates which bifurcation is optimally visualized

Fig. 11

Correlation of 3D QCA segment length and the true wire segment length

Fig. 12

Bland–Altman plot of 3D QCA segment length and the true wire segment length

Fig. 13

Scatter plot for the difference of optimal view angle between 3D QCA assessment and the ground truth