Computer tomographic analysis of organ motion caused by respiration and intraoperative pneumoperitoneum in a porcine model for navigated minimally invasive esophagectomy.
Navigation systems have the potential to facilitate intraoperative orientation and recognition of anatomical structures. Intraoperative accuracy of navigation in thoracoabdominal surgery depends on soft tissue deformation. We evaluated esophageal motion caused by respiration and pneumoperitoneum in a porcine model for minimally invasive esophagectomy. In ten pigs (20-34 kg) under general anesthesia, gastroscopic hemoclips were applied to the cervical (CE), high (T1), middle (T2), and lower thoracic (T3) level, and to the gastroesophageal junction (GEJ) of the esophagus. Furthermore, skin markers were applied. Three-dimensional (3D) and four-dimensional (4D) computed tomography (CT) scans were acquired before and after creation of pneumoperitoneum. Marker positions and lung volumes were analyzed with open source image segmentation software. Respiratory motion of the esophagus was higher at T3 (7.0 ± 3.3 mm, mean ± SD) and GEJ (6.9 ± 2.8 mm) than on T2 (4.5 ± 1.8 mm), T1 (3.1 ± 1.8 mm), and CE (1.3 ± 1.1 mm). There was significant motion correlation in between the esophageal levels. T1 motion correlated with all other esophagus levels (r = 0.51, p = 0.003). Esophageal motion correlated with ventilation volume (419 ± 148 ml) on T1 (r = 0.29), T2 (r = 0.44), T3 (r = 0.54), and GEJ (r = 0.58) but not on CE (r = - 0.04). Motion correlation of the esophagus with skin markers was moderate to high for T1, T2, T3, GEJ, but not evident for CE. Pneumoperitoneum led to considerable displacement of the esophagus (8.2 ± 3.4 mm) and had a level-specific influence on respiratory motion. The position and motion of the esophagus was considerably influenced by respiration and creation of pneumoperitoneum. Esophageal motion correlated with respiration and skin motion. Possible compensation mechanisms for soft tissue deformation were successfully identified. The porcine model is similar to humans for respiratory esophageal motion and can thus help to develop navigation systems with compensation for soft tissue deformation.