Registration of multi-view echocardiography data

Three-dimensional transesophageal echocardiography (TEE) is a non-invasive imaging technique that is particularly suited for visualizing the heart in real-time. For these reasons, TEE is an useful imaging modality for intraprocedural guidance, for example in the case of catheter ablations for the treatment atrial fibrillation (AF). AF is a common cardiac arrhythmia that is characterized by rapid and irregular atrial contraction and it is associated with significant health problems. The ablation procedure aims at restoring the normal heart rhythm by isolating the pulmonary veins, which are a frequent source of ectopic electrical triggers, from the left atrium (LA). Conventionally, these ablation procedures relied on fluoroscopy, though these two-dimensional projections are less suited for soft tissue visualization. These days, the option to integrate preprocedural computed tomography or cardiac magnetic resonance data into the electro-anatomical mapping system resulted in shorter fluoroscopy times and improved outcome of the ablation procedures. Next to these developments, TEE is a technique of interest to reduce radiation exposure even further. Since the LA is too large to be visualized in a single TEE view, image mosaicing is required to obtain a wideview TEE data set of the LA. The envisioned clinical implementation demands a method to align the acquired TEE views in a limited amount of time, preferably without any user interaction. Automatic registration of the multi-view TEE data of the LA is challenged by the small amount of overlap between the views and the large transformations that are involved. To capture the LA by means of TEE a standardized acquisition protocol was developed. Since regular pairwise registration of the views of this protocol did not lead to satisfactory results, atlas-based mosaicing (ABM) was introduced as method for the registration of these data. ABM uses an atlas set that consists of comparable TEE data of other patients. This method employs the fact that all data is acquired following a common protocol by including the registration of the individual TEE views to the atlas data as an intermediate step. The compounded atlas data offers full volume information to facilitate the registration of the newly acquired TEE data. The outcomes of these registrations are used to initialize the pairwise registration of the individual TEE views, which results in a set of candidate transformations from which the best transformation has to be selected. Using this approach, wideview TEE data of the LA was obtained after accurate and automatic registration of the involved data. This is an essential step towards our envisioned implementation: the use of TEE as imaging modality to assist in the guidance of the ablation procedures in AF patients.