[Development and validation of a graphic method for spatial interpretation and evaluation of biplanar coronary angiograms]

Visual evaluation and measurement of the lesion geometry is impaired by the foreshortening of the radiographically displayed target coronary segment. For this reason, we developed and validated a simple graphic procedure that facilitates the spatial interpretation and allows an objectifiable assessment of the view of the target coronary segment. The method computes a spatial axis of the coronary segment imaged in two planes and determines its inclination in the radiation path of each projection view. A triangle made up of the axis of the imaged segment, the unforeshortened axis of the imaged segment and the foreshortening height is displayed in each projection plane. The shape of the triangle indicates the degree of foreshortening while its position in the angiogram indicates the orientation of the spatial axis relative to the observer. The method was validated by comparing calculated and true foreshortening in the radiographic views of a centimetre grid obtained in the usual angiographic projections. The method has an accuracy and precision of 0.05 +/- 0.62%. It is applied clinically to evaluate biplane segmental visualization during coronary interventions and to select valid segmental views for measurements during quantitative biplane coronary angiography. This application may considerably facilitate the interpretation and assessment of biplane angiograms.