Automatic gating window positioning for 3D rotational coronary angiography (3DRCA)

Three-dimensional rotational coronary angiography (3DRCA) is a new technique for imaging coronary vessels in the human body. Due to the residual cardiac motion, projections being in the same cardiac motion state are extracted from the acquired series using electrocardiogram (ECG) information. A gating window is determined at a pre-defined trigger delay relative to the R-peaks with a constant width. In order to achieve the best possible image quality, cardiac phases must be found during which the heart is nearly stationary. However, the (ECG) signal represents the electrical activity of the heart and corresponds to the heart movement only approximately. Currently, the optimum gating window positioning is based on values derived by experience. It is difficult to determine where the heart is most stable in the cycle due to a high patient variability. Furthermore, the optimal gating window position is depending on the coronary vessel segment. The purpose of this work is to introduce a simple and efficient image based technique, which is able to determine the optimal gating window position fully automatically. The measurements in this paper are based on the analysis of two-dimensional X-ray projection data of the coronary arteries in an animal (pig) model.