Application of Intraoperative MRI in Neurosurgery for Resection Control

Methods We performed intraoperative MRI in 161 patients using a 0.2 Tesla Magnetom Open (Siemes AG, Erlangen, Germany), which is located in the radiofrequency shielded part of our ‘twin’ operating theatre. In brain tumor surgery (n=54) (46 cases of glioma located around eloquent areas and 8 cases of tumors in the lateral or third ventricle e.g. neurocytoma or subependymoma) and in surgery for temporal lobe epilepsy (n=35) the patient is operated in the conventional part of the ‘twin’-OR and transported into the scanner on an aircushioned OR table. A 3D-FLASH (fast low angle shot) sequence (slab thickness: 168 mm, slice thickness: 1.5 mm, TR: 16 ms, TE: 7 ms, FOV: 250 mm) was used for imaging, allowing image data update for neuro-navigation. Contrast agent (Gadolinium-DTPA) was applied if the tumor showed enhancement in the preoperative pictures. In selected cases, as low grade astrocytomas, a T2-weighted sequence (slice thickness: 3 mm, 19 slices, TR: 6000 ms, TE: 117 ms, FOV: 230 mm) was performed additionally. For intraoperative update of neuronavigation bone fiducials were attached around the craniotomy, allowing intraoperative registration of the new image data. The intraoperative image data were transferred to the navigation system (MKM microscope, Zeiss, Oberkochen, Germany) via ethernet. Pituitary adenoma and craniopharyngioma micro-surgery (n=43) with MR-compatible equipment was performed on the movable table of the MR scanner in the MR-Suite itself. Coronal and sagittal oriented scans (T1-weighted, slice thickness: 3mm, TR: 340ms, TE: 26ms, FOV: 200mm) were obtained after 8 minutes each. In 28 patients resection control was performed for other lesions, such as cavernoma, cysts, etc.