gms | German Medical Science

Background: First mentioned in 1996, intraoperative MRI (iMRI) has increasingly been used for resection guidance in brain tumor surgery over the last 20 years. A growing number of studies have illustrated benefits of iMRI-guided surgery for extent of resection (EOR) and patient survival. Recently, eight centers with iMRI in Germany formed a collaborative study group to investigate the impact of iMRI in neurosurgery on a multicenter basis, called the German Study Group of Intraoperative MRI (GeSGIM). This study sought give an overview about the development of the method and the contemporary use of iMRI in Germany.

Methods: A questionnaire exploring general iMRI setup, sequences used during surgery, amount of intraoperative scans performed per case, additional surgical tools used in combination with iMRI and overall number of iMRI-cases and their indication for iMRI surgery within the past 5-years was sent to eight german iMRI centers. Research interests of centers were pooled to initiate multicenter collaborations.

Results: Completed questionnaires were retrieved from all eight centers. Seven of them were academic university institutions. Mean time of active iMRI use was 12±6 years. Two centers had >20 years of iMRI experience. Currently, seven 1.5 tesla (T) magnets are used and one center uses a 0.15T magnet. Anatomic T1w and T2w/FLAIR sequences are acquired by every center in a routine protocol. Additional sequences acquired in selected cases include perfusion and diffusion-weighted imaging, diffusion tensor imaging, MR-spectroscopy, MR-angiography and resting-state functional MRI. Additional guidance-tools including 5-ALA, intraoperative ultrasound, electrophysiology as well as awake surgery were combined with iMRI at the discretion of the respective center. Over the last 5-years, GeSGIM centers performed a total of 4973 iMRI cases. The majority of iMRI-cases were gliomas (2482, 50%), followed by pituitary tumors (849, 17%) and other tumor entities (495, 10%). IMRI was also used for planning of stereotactic procedures or epilepsy surgery (968, 20%). The GeSGIM published one retrospective multicenter study in 2016. A prospective study evaluating iMRI for glioblastoma and a prospective registry for low grade glioma are recruiting since 2015.

Conclusion: German iMRI centers have gathered extensive expertise in the field of iMRI-surgery over the last 20 years. The collaboration of eight iMRI centers within the GeSGIM formed a unique and powerful study group producing high annual iMRI case numbers for multicenter research. Among centers, there is consensus to use anatomic imaging for resection guidance and control of EOR in glioma surgery. However, there is great variation concerning additional iMRI-sequences used which depends on the research interest of respective centers. Future studies should aim to confirm the benefit of those additional iMRI sequences on a multicenter basis.