Martin Koch, Sebastian Bauer, Joachim Hornegger, Norbert Strobel

Modeling the deformable shape of the left atrium is of strong
interest for many applications in cardiac diagnosis and intervention. In
this paper, we propose a method for left atrium shape modeling using
non-rigid point cloud registration. In particular, we build upon the
concept of Coherent Point Drift (CPD) registration that considers the
alignment as a probability density estimation problem. Based on the set
of non-rigidly registered point clouds, we perform a principle component
analysis to establish a deformable shape model. In an experimental study
on ten clinical data sets, we evaluated the registration accuracy in terms
of average mesh-to-mesh distance, as well as on anatomical landmarks
on the left atrium. With the proposed method, we achieved registration
results with an average mesh-to-mesh error of 3:4mm. The average
landmark oset was 8:5mm.

Martin Koch, Alexander Brost, Atilla Kiraly, Norbert Strobel, Joachim Hornegger 

Minimally invasive catheter ablation of electric foci, performed in electrophysiology labs, is an attractive treatment option for atrial fibrillation (AF) - in particular if drug therapy is no longer effective or tolerated. There are different strategies to eliminate the electric foci inducing the arrhythmia. Independent of the particular strategy, it is essential to place transmural lesions. The impact of catheter contact force on the generated lesion quality has been investigated recently, and first results are promising. There are different approaches to measure catheter-tissue contact. Besides traditional haptic feedback, there are new technologies either relying on catheter tip-to-tissue contact force or on local impedance measurements at the tip of the catheter. In this paper, we present a novel tool for post-procedural ablation point evaluation and visualization of contact force characteristics. Our method is based on localizing ablation points set during AF ablation procedures. The 3-D point positions are stored together with lesion specific catheter contact force (CF) values recorded during the ablation. The force records are mapped to the spatial 3-D positions, where the energy has been applied. The tracked positions of the ablation points can be further used to generate a 3-D mesh model of the left atrium (LA). Since our approach facilitates visualization of different force characteristics for post-procedural evaluation and verification, it has the potential to improve outcome by highlighting areas where lesion quality may be less than desired. 

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