Imaging techniques REGISTRATION OF THREE DIMENSIONAL LEFT ATRIAL IMAGES WITH INTERVENTIONAL SYSTEMS

Correspondence to: Dr Jasbir Sra, University of Wisconsin Medical School-Milwaukee Clinical Campus, Milwaukee, Wisconsin, USA; bdanek@ hrtcare.com _________________________ I mage registration is the process of aligning images. 2 During interventional procedures to deliver electrical therapy, the catheters or leads are usually manipulated under the guidance of a fluoroscopy system. Typically, as in the case of ablation of atrial fibrillation (AF), the most complex of the cardiac arrhythmias, mapping and ablation catheters must be manipulated in and around the pulmonary veins (PVs) and the left atrium (LA). These anatomical structures are not visualised by x ray fluoroscopy as they do not present contrast against the surrounding anatomical structures. Currently available cardiac mapping systems can record catheter location, cardiac electrical activation information, and lesion location. However, these systems cannot reproduce complex cardiac chamber anatomy such as the LA-PV junction. Segmentation of various body organs can be performed by such imaging techniques as computed tomography (CT) and magnetic resonance imaging. However, these imaging systems are not capable of tracking a catheter in real time or recording electrical activation. Combining the explicit three dimensional (3D) anatomy of a cardiac chamber such as the LA with the electrical and navigational information obtained with an interventional system, through a process known as registration, should increase the efficacy of ablation procedures. Although various other modalities have been used in an attempt to delineate cardiac structures, 3D imaging of the LA using CT will be discussed in detail in this review. Currently, there is little application of 3D image registration in the treatment of cardiac arrhythmias. This review will describe the methods available for cardiac image registration in an attempt to give the reader a grasp of the main concept of registration without getting into great detail on the mathematical constructs underlying this evolving new technology.