Technical note: enhanced MR-guided stereotaxic brain surgery with the patient under general anesthesia.

Stereotaxic surgery guided with CT has long been a valuable tool in neurosurgical practice and has a high degree of accuracy with a low morbidity rate [1]. MR imaging, with its inherently greater soft-tissue contrast resolution and its ability to obtain images directly in any desired plane, is increasingly useful in studying the brain. This latter characteristic is also useful for simulating the probe trajectory toward the target. Recent reports on MR-guided stereotaxic surgery have described its performance under local anesthesia andfor sedation, but not under general anesthesia because significant ferromagnetic artifacts from anesthesia equipment obscure the underlying anatomy [2-5]. We studied the possibility of the use of an anesthesia machine in an MR room. This study was conducted in two parts. First, a phantom study was designed to evaluate the influence of a ferromagnetic anesthesia machine on MR images by placing the machine in the MR room. The influence of the magnetic field on the anesthesia machine was also evaluated. Second, using a BrownRoberts-Wells (BRW) stereotaxic system, we performed contrast-enhanced MR-guided surgery on six patients who were under general anesthesia. Our results indicate that an anesthesia machine may be used in an MR room if the magnet has a small fringe field .