@article{BrostWimmerLiaoetal., author = {Brost, Joachim and Wimmer, Andreas and Liao, Rui and Bourier, Felix and Koch, Martin and Strobel, Norbert and Kurzidim, Klaus and Hornegger, Joachim}, title = {Constrained registration for motion compensation in atrial fibrillation ablation procedures}, series = {IEEE Trans Med Imaging}, volume = {31}, journal = {IEEE Trans Med Imaging}, number = {4}, doi = {10.1109/tmi.2011.2181184}, pages = {870 -- 881}, abstract = {Fluoroscopic overlay images rendered from preoperative volumetric data can provide additional anatomical details to guide physicians during catheter ablation procedures for treatment of atrial fibrillation (AFib). As these overlay images are often compromised by cardiac and respiratory motion, motion compensation methods are needed to keep the overlay images in sync with the fluoroscopic images. So far, these approaches have either required simultaneous biplane imaging for 3-D motion compensation, or in case of monoplane X-ray imaging, provided only a limited 2-D functionality. To overcome the downsides of the previously suggested methods, we propose an approach that facilitates a full 3-D motion compensation even if only monoplane X-ray images are available. To this end, we use a training phase that employs a biplane sequence to establish a patient specific motion model. Afterwards, a constrained model-based 2-D/3-D registration method is used to track a circumferential mapping catheter. This device is commonly used for AFib catheter ablation procedures. Based on the experiments on real patient data, we found that our constrained monoplane 2-D/3-D registration outperformed the unconstrained counterpart and yielded an average 2-D tracking error of 0.6 mm and an average 3-D tracking error of 1.6 mm. The unconstrained 2-D/3-D registration technique yielded a similar 2-D performance, but the 3-D tracking error increased to 3.2 mm mostly due to wrongly estimated 3-D motion components in X-ray view direction. Compared to the conventional 2-D monoplane method, the proposed method provides a more seamless workflow by removing the need for catheter model re-initialization otherwise required when the C-arm view orientation changes. In addition, the proposed method can be straightforwardly combined with the previously introduced biplane motion compensation technique to obtain a good trade-off between accuracy and radiation dose reduction.}, language = {en} } @incollection{KuechlerSchoberLiebschneretal., author = {K{\"u}chler, Andreas and Schober, F. and Liebschner, M. and Berger, Frank and Exner, W. and Krause, Ch. and Fritsche, R. and Wimmer, R.}, title = {Dielectric Behaviour of HVDC Insulating Materials, Polarization and Conduction Processes in Mineral Oil and in Pressboard Impregnated with Different Fluids}, series = {19th International Symposium on High Voltage Engineering}, booktitle = {19th International Symposium on High Voltage Engineering}, address = {Pilsen, Czech Repbulic}, language = {en} }