Vessel target location estimation during the TIPS procedure

Abstract

Creation of a Transjugular Intrahepatic Portosystemic Shunt (TIPS) requires passage of a needle toward a moving target that is only seen transiently by x-ray prior to needle passage. Intraoperative, 3D target localization would facilitate target access and improve the safety of the procedure. The clinical assumption is that patients undergoing the TIPS procedure possess rigid, cirrhotic livers that undergo only intraoperative translation without significant deformation or rotation. Based upon this assumption, we hypothesize that the position of any unseen, 3D target point within the liver can be determined intraoperatively by precalculation of the relative positions of the target point to a different 3D point that can be tracked intraoperatively. This paper examines this hypothesis using intraoperatively acquired, biplane, x-ray images of 7 patients. In 6, we tracked the effects of cardiac and respiratory motion, and in 3 the effects of needle pressure. Methods involved reconstruction of 3D vessel bifurcation and other trackable intrahepatic points from biplane angiograms, measurement of liver deformation by examining changing distances between these 3D points over time, and comparison of expected to actual displacements of these points with respect to a fixed reference point in the liver. We conclude that, for the rigid livers associated with patients undergoing TIPS, that there is less intraoperative deformation than previously reported by other groups addressing healthy liver deformation, and that the location of an unseen target can be predicted within 3 mm accuracy.

Intravascular Ultrasound in the Creation of Transhepatic Portosystemic Shunts Reduces Needle Passes, Radiation Dose, and Procedure Time: A Retrospective Study of a Single-Institution Experience

“…Attempts have been made to improve visualization and reduce radiation exposure during the procedure, including the use of biplanar angiography (10); guide wire placement targeting the hepatic artery (11), computed tomography (CT)-guided direct percutaneous transhepatic puncture of the left portal vein through a snare placed in the left hepatic vein (12,13); and the "gun-sight" technique, which involves transhepatic needle puncture through two snares, one placed in the right portal vein with CT guidance and the other placed in the retrohepatic IVC (14). Although these methods have been reported to aid in portal vein puncture, there has been particular interest in the use of ultrasound (US) guidance (15)(16)(17)(18) because it does not involve increased radiation.…”