gms | German Medical Science

Objective: High-field intra-operative MRI (iMRI) systems offer excellent imaging quality and are used in a number of centers for resection control and update of the image guidance systems. Although expensive, such a system improves not only the radicality of tumor resections but can improve the safety of neurosurgical procedures by using functional MR imaging. A ceiling mounted intra-operative MRI system has several advantages compared to a conventional iMRI system. We report on the first clinical experience in Europe using such a state of the art 1.5T iMRI system.

Methods: Between October 2010 and June 2011 an iMRI System “Visius Surgical Theatre” (IMRIS, Calgary, Canada) offering a 1.5 Tesla ceiling mounted moveable magnet was installed. Between July and November 2011 a total of 40 consecutive patients with tumors and vascular lesions were operated in the iMRI-Unit. Neuronavigation was used with intra-operative update of the image guidance system and localization of tumor remnants. Patients' data, surgical time, radicality of tumor removal and other parameters were analyzed.

Results: Patients' mean age was 48 years (range 8–77 years) and the median duration of the surgical procedures was 6 hours. The lesions included 4 low grade gliomas, 6 grade III astrocytomas, 7 glioblastomas, 7 metastases, 6 pituitary adenomas, 2 cavernomas, 2 lymphomas, 1 cortical dysplasia, 3 aneurysms, 1 arterio venous malformation and 1 extra-intracranial bypass. In all 5 vascular cases, special MRI sequences such as diffusion and perfusion sequences confirmed successful treatment of the pathology while it depicted intact regional perfusion but no early ischemia. In tumor lesions, intraoperative imaging depicted tumor remnant in 45% of the cases, which led to further tumor resection. Despite the high magnet field, intra-operative monitoring (IOM) was used in all 4 cases of tumors in eloquent areas. In 3 of these cases resection had to be stopped due to IOM changes, which resulted in subtotal tumor removal.

Conclusions: In almost half of the cases, the tumor resection was continued based on the iMRI scans showing the value of this imaging tool. The combination of iMRI and IOM showed that IOM adds great value to an iMRI system. Long-term follow-up and more experience with this state of the art system are necessary to further evaluate its full benefit for neurosurgical procedures.