Assessment of hepatic motion secondary to respiration for computer assisted interventions.

This article reviews the published efforts to characterize hepatic motion secondary to respiration, with the specific goal of defining the limitations and potential applications of image-guided systems in percutaneous liver interventions (computer assisted interventions). Hepatic motion and deformation due to respiration remain obstacles to applying stereotactic localization techniques to the liver. Respiratory-associated hepatic motion is complex. Nine studies using diagnostic imaging or modeling are reviewed, and their findings are tabulated herein. The significant variations in their findings are discussed, including cranio-caudal translation, anterior-posterior and lateral translation, movement secondary to tissue deformation, and motion with respect to surrounding tissue. Techniques for correcting for hepatic respiratory motion are then described, including gating techniques, modeling approaches, real-time liver tracking, and magnetic tracking technology.