Intraoperative Magnetic Resonance Imaging for Pituitary Adenomas.

Surgery for pituitary adenomas attempts the optimally possible amount of tumor resection, which ideally is total excision. However, there are limitations in the resectability and in the intraoperative assessment of the radicality of an adenomectomy. Postoperative imaging is usually performed with a few months delay after tumor resection. Intraoperative magnetic resonance imaging (MRI) is used to depict the extent of tumor removal already achieved in the operating theater during surgery. To date, there are different low- and high-field intraoperative MRI systems available. Decompression of optic pathways, preservation of the pituitary and residual tumor can be largely predicted from the intraoperative images. Several studies convincingly show that intraoperative depiction of residual tumor allows targeted attack of the remnant. Not only is the amount of tumor resected increased, but also the percentage of total tumor excisions. Intraoperative MRI provides an immediate feedback to the surgeon and is thus a valuable quality control for pituitary surgery. It also allows the acquisition of data sets for precise intraoperative navigation. However, the MRI scanners are heavy and expensive and some systems even require extensive modification of the operating theater. Imaging slightly prolongs the operation but is not associated with an increased complication rate. There are also potential artifacts which must be considered.