Mobile intraoperative MRI in neurosurgery at 1.5 T

Abstract

Introduction: Frameless navigation systems have been plagued by their inability to update preoperative MRI scans. Consequently, intraoperative MRI devices were integrated into several experimental operating rooms. They were of low-field strength, however, and we therefore planned to design and develop a 1.5 T, mobile system. Methods: The resulting design was a ceiling-mounted, mobile device permitting free access to the body. It's gradient coils have a 74 cm internal diameter and provide a maximum strength of 22 mT/m, a rise time of 400 μs for the x and y directions, and 315 μs for z. The cantilevered OR table is constructed of stainless steel, plastic, fiberglass and brass. A hydraulic system allows rotational and vertical movement in six degrees of freedom, and permits conventional patient positioning (including supine, prone and lateral). Three hundred and eighty-eight patients were operated on, and the results prospectively recorded and analysed. Results: A half of the epilepsy patients had residual target tissue when imaged at a time when the surgeon thought the surgical goals had been accomplished. Complete resection was then confirmed in all these cases prior to resection. A similar percentage of pituitary tumor patients benefited from this, as did approximately a quarter of low-grade gliomas. Discussion: Conventional images are being supplemented with MRA techniques, which allow complex vascular procedures to be performed. Carotid endarterectomy research is under way, with intraoperative DWI and perfusion studies evaluating different techniques. An MR-compatible robot has been design to couple with our system to perform guided stereotaxy.