Automatic dynamic quantification of oesophagus position from intra-cardiac echocardiography during atrial fibrillation ablation

Left atrium posterior wall (LAPW) is an essential target for transcatheter radiofrequency ablation (RFA) of atrial fibrillation (AF), but poses problems due to retro-atrial structures potentially damaged by RF. Intracardiac echocardiography (ICE) can be integrated with the 3D electro-anatomical map and can give unique real-time anatomical information about all closely-located peri-cardiac structures. The present study aimed to automatically detect dynamic oesophagus position and its spatial relationship from the LAPW by ICE during RFA. A fast algorithm based on the evaluation of gray-level intensity distribution in the image and was developed to detect distal and proximal oesophagus boundaries. The algorithm was tested in 15 ICE acquisitions. The detected oesophagus boundaries and those manually traced (MT) were compared and in 5 ICE sequences, dynamic tracking of proximal oesophagus boundary was performed. Mean analysis time was 4.5 sec/frame. Detected oesophagus wall positions were in good agreement with MT. Mean minimum dynamic distance between LAPW and oesophagus proximal wall during acquisition was 0.3±0.2mm (range: 0.0-0.6mm). This technique allows automated and accurate dynamic detection of LAPW and oesophagus position in ICE sequences. It represents a first step for dynamic quantification of oesophagus real-time position' changes and its distance from the LAPW to prevent oesophagus injuries.