DETERMINATION OF 3D POSITIONS OF PACEMAKER LEADS FROM BIPLANE ANGIOGRAPHIC SEQUENCES

In vitro and in vivo analyses of stress on pacemaker leads and their c omponents during the heart cycle have become especially important beca use of incidences of failure of some of these mechanical components. F or stress analyses, the three-dimensional (3D) position, shape, and mo tion of the pacemaker leads must be known accurately at each time poin t during the cardiac cycle. We have developed a method for determinati on of the in vivo 3D positions of pacemaker leads during the entire he art cycle. Sequences of biplane images of patients with pacemakers wer e obtained at 30 frames/s for each projection. The sequences usually i ncluded at least two heart cycles. After patient imaging, biplane imag es of a calibration object were obtained from which the biplane imagin g geometry was determined. The centerlines of the leads and unique, id entifiable points on the attached electrodes were indicated manually f or all acquired images. Temporal interpolation of the lead and electro de data was performed so that the temporal nonsynchronicity of the ima ge acquisition was overcome. Epipolar lines, generated from the calcul ated geometry, were employed to identify corresponding points along th e leads in the pairs of biplane images for each time point. The 3D pos itions of the lead and electrodes were calculated from the known geome try and from the identified corresponding points in the images. Using multiple image sets obtained with the calibration object at various or ientations, the precision of the calculated rotation matrix and of the translation vector defining the imaging geometry was found to be appr oximately 0.7 degrees and 1%, respectively. The 3D positions were repr oducible to within 2 mm, with the error lying primarily along the axis between the focal spot and the imaging plane. Using data obtained by temporally downsampling to 15 frames/s, the interpolated data were fou nd to lie within approximately 2 mm of the true position for most of t he heart cycle. These results indicate that, with this technique, one can reliably determine pacemaker lead positions throughout the heart c ycle, and thereby it will provide the basis for stress analysis on pac emaker leads. (C) 1997 American Association of Physicists in Medicine.