Intraoperative magnetic resonance imaging-guided neurosurgery

Over the last decade, neurosurgeons have become increasingly reliant on image guidance to perform surgery more safely, efficiently, and cost-effectively. Neuronavigational systems are either frame based or frameless and rely on the acquisition of computed tomography or magnetic resonance (MR) imaging (MRI) scans that are obtained either a few days or immediately before surgery to generate a 3-dimensional coordinate set. Unfortunately, neuronavigational systems do not allow the neurosurgeon to adjust for dynamic changes that occur during surgery such as brain shift. More recently, intraoperative MR (iMR) imaging systems have been developed and implemented to treat neurosurgical diseases. These systems consist of a low-field (0.12 or 0.23 T), midfleld (0-5 T), or high-field (1.5 T) MR imaging scanner located in an environment that allows general anesthesia to be administered. The main advantage of iMR imaging is the excellent soft tissue discrimination and 3-dimensional visualization of the operative site. Enhanced visualization of an intracranial target allows for a safe surgical trajectory to be chosen that avoids critical structures, the determination of the extent of the tumor resection, and the exclusion of intraoperative hemorrhage. All iMRI systems can provide the neurosurgeon with basic T1- and T2-weighted imaging sequences. High-field Mill systems can also perform advanced functional capabilities such as MR spectroscopy, functional MR imaging, MR venography (MRV), MR angiography (MRA), chemical shift imaging, and diffusion-weighted imaging, however. These MR imaging sequences can provide additional information that may facilitate the success of the operative procedure. identifying critical vascular structures with MRV and MRA may prevent their inadvertent injury during surgery. Locating an area of elevated choline level within a tumor at the time of biopsy may enhance the diagnostic yield of the procedure. Mapping out areas of neurologic function may influence the choice of the surgical approach to a tumor. In addition to using iMRI to resect tumors, it can be used for placement of deep brain stimulators for Parkinson disease, for the performance of psychosurgery for obsessive-computsive disorder, or for the treatment of common neurosurgical diseases such as hydrocephalus.