Implementation of the ultra low field intraoperative MRI PoleStar N20 during resection control of pituitary adenomas.
OBJECTIVE
To describe our experience with the application of an intraoperative ultra low field magnetic resonance imaging system (ioMRI) PoleStar N20, Medtronic Surgical Navigation Technologies, Louisville, USA during resection control of pituitary adenomas.


METHODS
Forty-four patients were operated on a pituitary adenoma (1 microadenoma, 43 macroadenomas; mean size 26.0 ± 9.7 mm). The ioMRI system was used for navigation and resection control after transseptal, transsphenoidal microsurgical tumour removal using standard instruments and standard microscope. If any accessible tumour remnant was suspected surgery was continued for navigation guided re-exploration and if necessary continued resection.


RESULTS
The applications of the scanner integrated navigation system, with a 3-planar reconstruction of the coronal scan, enabled the surgeon to safely approach and remove the tumour. The quality of preoperative tumour visualization with the ultra low field ioMRI in patients with macroadenomas is very good and has a good congruency with the preoperative 1.5 T MRI. For microadenomas the preoperative visualization is poor and very difficult to interpret. In seven patients ioMRI resection control showed residual tumours leading to further resection. After final tumour resection the ioMRI scan documented adequate decompression of the optic pathway in all patients. However, the intraoperative image interpretation was equivocal in four patients in whom it was difficult to distinguish between small intrasellar tumour remnants and perioperative changes.


CONCLUSIONS
The PoleStar N20 is a safe, helpful and feasible tool for navigation guided pituitary tumour approach. Image interpretation is requires some experience, but decompression of the optic system can be reliable shown in cases with pituitary macroadenomas. This system is of limited value for resection control of pituitary microadenomas.
Department of Neurosurgery and Neuroradiological Institute, Johann Wolfgang Goethe- University, Schleusenweg 2-16, 60528 Frankfurt/Main, Germany. r.gerlach@em.uni-frankfurt.de
Ruediger
R
Gerlach
Richard du Mesnil
Rdu M
de Rochemont
Thomas
T
Gasser
Gerhard
G
Marquardt
Lioba
L
Imoehl
Volker
V
Seifert
D000236:Adenoma / Q000601:surgery*; D000328:Adult; D000368:Aged; D005260:Female; D006423:Hemianopsia / Q000209:etiology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000295:instrumentation* / Q000379:methods*; D018365:Neoplasm, Residual / Q000601:surgery; D019635:Neurosurgical Procedures / Q000379:methods*; D010911:Pituitary Neoplasms / Q000601:surgery*; D016896:Treatment Outcome