“Snapper-Stereoguide” – A New Device for Image Guided, Frameless Stereotactic Procedures in the Open MR

Abstract

Summary A new device has been developed for planning, guiding and performing image guided stereotactic procedures. The burr hole mounted device is made of biocompatible composite (polyacetal) and consists of a probe holder within a ball-and-socket joint, to which a light-emitting diode reference stage is attached. In combination with intraoperative, near real-time imaging, this system aids in targeting burr hole entry points and trajectories. The open intraoperative MR (Signa SP, General Electric) used in this series fuses the anatomical space with imaging space and time space and transforms a “blind” stereotactic procedure into a visually controlled one. Planning and performing stereotactic interventions become a single step procedure without using registration, frames and fiducials. The snapper-stereoguide has been evaluated in more than 300 stereotactic procedures including biopsies, evacuations of cysts, abscesses, hematomas, insertion of laser fibres for laser induced interstitial thermotherapy (LITT) and guiding endoscopes. Although evaluated in an open MRI unit, this system could be used in all image guided procedures involving direction of a stereotactic instrument. On the basis of this clinical series this artefact free and frameless device for near real time stereotactic procedures proved to be easy to use, fast, accurate and safe. Taking into account the amount of brain and target shift observed in 30% of the procedures in this series, the dynamic accuracy of near real time MR imaging is not surpassed by any other system. The combination of the snapper-stereoguide and the OIMR was found to be a very helpful alternative to all currently used direct and indirect, frame-based and frameless systems.