gms | German Medical Science

Objective: We have integrated a 1.5 T MRI system into a fully equipped OR. It was our goal, to provide the capabilities of a conventional OR with advanced imaging and guidance technology. In September 2005 the OR was fully operational. We use a short bore system (Philips Medical Systems) which allows us to do operations with conventional tools under the microscope outside the 5 Gauss line, and then pivot and transfer the patient to the scanner.

Methods: From September 2005 to October 2006, 100 operations were performed,consisting of 69 gliomas, 21 pituitary adenomas, 5 metastases, 4 cavernomas and 1 meningioma. In all patients we used the ceiling mounted navigation system (BrainLab). In 45 patients intraoperative images were used for updated Navigation. 12 patients were operated under conscious sedation for tumours in eloquent areas. 11 patients were operated using fluourescence guidance (5-ALA). A specifically adapted Mayfield head clamp allows rigid fixation. Routine imaging consists of T1, T2, DWI, Flair and post-contrast studies, as well as dynamic perfusion studies in recurrent gliomas. In selected cases, we do spectroscopy and DTI. There are at least 3 imaging sessions: the first after positioning, then after a considerable tumour resection, and finally before closure. Tumour resection is carried out using standard neuronavigation and microsurgical techniques. Subsequent image data sets are registered and used for updated navigation when deemed necessary.

Results: The set-up provides rapid access to imaging and updated navigation for all lesions. The transfer time is negligible. However, depending on the information to be extracted, the scanning time can be up to 45 minutes. The necessity of using the table to serve imaging needs limits its degrees of freedom to raising and lowering of the head, as well as total height adjustment.

Conclusions: Imaging of high-grade and recurrent gliomas remains a challenge, due to slow contrast leakage (spread enhancement) as well as fast, time dependent contrast distribution for recurrent lesions and radiation changes. Intraoperative MRI provides a good basis for surgical decision making and guidance. However, the pathology of these tumors, in particular gliomas, demands tailored approaches in respect to imaging, as well as to surgical techniques, such as conscious sedation or fluorescence guidance.