7096 Interventional endoscopy and ercp under mr guidance - preliminary experiments in an animal model.

Abstract

Background: Interventional endoscopy including ERCP has been performed under endoscopic and/or fluoroscopic monitoring for gastrointestinal and pancreatobiliary interventions. Saving radiation as well as improving targeting and visualizing of surrounding structures were the main aims of our first experiments in MR-guided therapeutic endoscopy. Methods: The Erlangen training model for interventional endoscopy was used for the experiments with 4 stomach and 2 whole upper abdominal organ sets (including liver and biliary system. One pig stomach carried a spontaneous 5 cm tumor, in the other stomach specimens, tumors were created by fibrin glue injection, polyurethane injection, or banding with tumor sizes between 5 and 15 mm.Two specimens with native bile ducts were used for MR-guided biliary interventions. Accessories used were nitinol baskets, snares and teflon wires. MR machines used for the experiments were the Siemens Magnotom open gantry 0.2 Tesla for the GI experiments and the Philipps ACS NT closed gantry 1.5 Tesla for biliary experiments. Results: With both machines, the endoscope was mainly visible in intragastric fluid; attempts to visualize the endoscope in air using various catheters (filled with gadolinium) or guidewires/probes failed; a gadolinium filled balloon with a diameter of 1 cm around the endoscope tip was the only way to localize the instrument tip. The open system (heavily weighted T2 FLAIR sequences, acquisition times 0.5 - 1.5 minutes) was used for visualization of intragastric tumors which could be seen down to the size of 5 mm. Fibrin glue was less effective than polyurethane and banding in creating visible tumors. Using faster image sequences deteriorated the image. Baskets and snares were partially visible when placed around tumors. For visualization of the biliary system, the open system did not yield sufficient images and therefore the closed system (heavily weighted T2 sequences) was necessary, where the endoscope tip in the duodenum and a papillotome in the CBD could be seen. Conclusions: Sophisticated imaging (preferentially real-time) of smaller structures for delicate therapeutic interventions under MR control (e.g. MR-guided ERCP) will probably require the use of closed MR systems which then have to be short enough for performing endoscopy in an adequate way. Open systems could be used for intermittent monitoring and localization of endoluminal procedures, but acquisition time has to be reduced.