A study of porcine liver motion during respiration for improving targeting in image-guided needle placements.

PURPOSE: Liver motion due to respiration restricts targeting and needle placement accuracy during image-guided interventional procedures. Breath holds, imaging techniques, and navigation systems are used to improve targeting accuracy. Data of in-vivo liver behavior under respiration can enhance these approaches.
METHODS: An experimental study was performed using the swine model to capture the dynamics of liver motion during respiration using needles tipped with electromagnetic sensors. The swine liver was segmented into four lobes (right lateral, right medial, left medial and left lateral), and two sensor-tipped needles were placed in each location to acquire representative displacement data.
RESULTS: Maximum displacement was found to occur in the left medial and left lateral lobes, in the anterior-posterior direction. Significant lobe-dependent variation in motion behavior was recorded, but a variation within a lobe was minimal and independent of needle approach. Magnitude of displacement in all lobes was found to be monotonically correlated to breathing volume. Displacement of liver was found to be out of phase with breathing by approximately 2 Hz. The positioning of the animal was also found to influence direction and magnitude of liver displacement in different lobes.
CONCLUSIONS: We have presented previously unavailable data and insight into the role of easily controllable parameters such as breathing volume, patient positioning, and lobe-specific heterogeneity in the displacement of liver due to respiration.