Intravenous angiocardiography using digital image processing. II. Detection of left-to-right shunts in an animal model.

Digital image processing was applied in an experimental model to study the feasibility of intravenous angiocardiography for the detection of cardiac lesions with left-to-right shunting. Methods were designed to produce ventricular and atrial septal defects (VSD, ASD) as well as patent ductus arteriosus (PDA) equivalent in pigs. After intravenous (IV) injection of 0.5-1 ml of Urografin 76% per kg body weight, digitization and computerized processing of roentgen video images recorded at a rate of 50 fields per second was performed. The radiographic images were recorded in the four-chamber view obtained by 30-35 degrees of caudocranial angulation and 50-60 degrees of left anterior oblique positioning of the animal. The processing of images included electrocardiogramgated background subtraction, rescaling, and sometimes histogram equalization. Integration of multiple background and multiple contrast images was performed in order to increase the signal-to-noise ratio. Ventricular septal defects and patent ductus arteriosus could be detected per se, while atrial septal defect only could be indirectly detected. Respiratory motion artifacts could be avoided by cross-correlation respiratory gating or by subtracting left ventricular end systole from end diastole during the same cardiac cycle of left ventricular opacification. The results of the experiments in pigs are the basis for continued clinical use of digitized IV angiocardiography.