gms | German Medical Science

To review the utility, feasibility and the preliminary experience using an intraoperative low-field strength magnetic resonance imaging (iMRI) during resection of pituitary adenomas.

12 patients were operated on a pituitary adenoma in a standardized microsurgical procedure (transnasal transphenoidal approach, standard microsurgical instruments). The adenoma was located purely intrasellar in 1 patient and showed suprasellar extension in 11 patients. Intraoperative imaging was performed using the Pole Star N20 0,15 T-scanner with an integrated navigation system (Odin, Israel). After sharp head fixation one preoperative scan for head positioning control was performed with an e-steady sequence (mixed T1/ T2 contrast 8mm slices 8s scan). For navigation and tumour visualization a coronal T1- weighted gadolinium contrast-enhanced scan was performed (0.4ml/ kg body weight, 3-4mm slice thickness, 6-7 minute scan time). Surgical procedure was started using the navigation system for guidance based on a 3 planar reconstruction of the previous scan. After complete resection of the adenoma - as judged by the surgeon - a T1 weighted Gd-enhanced coronal scan was repeated to confirm surgical resection. If tumour remnants were visible on the control scan, surgery was continued until further scan(s) documented complete resection (tumours extending into the cavernous sinus or with an extreme adherent tumour capsule were not considered for complete removal).

Image quality was appropriate to visualize chiasma, pituitary stalk, adenomas and tumour remnants in all patients. In 6 (50%) patients, resection was total as documented by the first intraoperative post-resection scan. However subtotal resection was found in 6 (50%) patients and surgery was continued until all surgical accessible tumour remnants were removed. Therefore, the goal of surgery was achieved in all patients and documented by iMRI. Neurosurgical work flow is not affected by the use of the iMRI including positioning of the patients. The surgical procedure can be performed using instant online navigation without registration and avoiding X-ray exposure to patients and operative staff.

The 0,15T iMRI is a safe, helpful and feasible tool to navigate the surgeon and to demonstrate tumour resection during pituitary surgery. Clinical long-term follow-up and 3 months control scans are necessary to correlate the intraoperative images with routine postoperative scans and to proof the benefit of this new technique.