Experimental study of the magnetic stereotaxis system for catheter manipulation within the brain

Object. The magnetic stereotaxis system (MSS) is a device designed to direct catheter tips through magnetic forces. In this study the authors tested the safety and performance of the MSS in directing catheters through a nonlinear path to obtain biopsy specimens in pig brains. Methods. Sixteen pigs underwent biopsy of the frontal brain region with the aid of an MSS (11 pigs) or a standard stereotactic biopsy tool (five pigs). Surgical preparation consisted of placement of six fiducial markers in the skull and the creation of a burr hole for attachment of a cranial bolt and passage of the biopsy catheter. The pigs underwent magnetic resonance (MR) imaging of the head to define a biopsy target and to plan a nonlinear path. Guided by the MSS, which used nearly real-time fluoroscopic imaging fused to the preoperative MR image, the authors advanced a catheter to the biopsy target. A biopsy tool was passed through the catheter and a tissue sample was obtained. The animals were observed for 3 to 5 days postoperatively, when they were assessed for neurological abnormalities or other signs of morbidity. Actual catheter placement was within 1.5 mm of the planned path to the biopsy site, using a minimum path radius of 30 mm. The registration error associated with the use of the MSS x-ray fluoroscopy and MR imaging averaged 1.7 mm. Tissue disruption caused by the MSS was similar to that of standard stereotactic procedures. Conclusions. The MSS affords accurate and safe guidance of brain catheters in animals. The application tested here, brain biopsy, is one of a number of potential catheter-guided procedures.