Cranial surgery and navigation with a compact intraoperative MRI system.

Experience with a compact unit for intraoperative magnetic resonance imaging (iMRI) and integrated surgical navigation is presented. The system, commercially known as the PoleStar N-10 (Odin Medical Technologies, Yokne'am, Israel) includes a 0.12 Tesla permanent magnet that docks under a regular OR table. A passive infrared-based optical navigation system is included and the device can be controlled by the operating neurosurgeon and staff. We have operated on 93 patients using the PoleStar N-10. Diagnoses included glioma in 27, pituitary adenoma in 19, meningioma in 15, and others in 40. Lesions were removed from the skull base in 35 patients of whom 8 had posterior fossa masses. Surgery was affected by imaging in 51% of operations. Additional lesion, not otherwise apparent, was removed in 21; in 14 other patients unnecessary dissection was avoided when the new image confirmed that the surgical goals had been achieved. Additional time incurred with use of the PoleStar diminished with increasing experience. Testing of the navigation tool confirmed its accuracy to be comparable to other "frameless stereotactic" devices, on the order of 2 mm; likewise accuracy was increased by using T1 weighted imaging with thin slices. The introduction of new, faster imaging sequences and targeting tools has helped to make the PoleStar N-10 a routine tool for intracranial surgical navigation, with the added benefit of updated imaging during the procedure.