Preoperative Magnetic Resonance and Intraoperative Ultrasound Fusion Imaging for Real-Time Neuronavigation in Brain Tumor Surgery Präoperative MRI- und intraoperative Ultraschallfusion für die Echtzeit-Neuronavigation in der Kopftumorenchirurgie

Abstract ! Purpose: Brain shift and tissue deformation duringsurgery for intracranial lesions are the main actuallimitations of neuro-navigation (NN), which cur-rentlyreliesmainlyonpreoperativeimaging.Ultra-sound (US), being a real-time imaging modality,is becoming progressively more widespread du-ring neurosurgical procedures, but most neurosur-geons, trained on axial computed tomography (CT)and magnetic resonance imaging (MRI) slices, lackspecific US training and have difficulties recogniz-ing anatomic structures with the same confidenceas in preoperative imaging. Therefore real-time in-traoperativefusionimaging(FI)betweenpreopera-tive imaging and intraoperative ultrasound (ioUS)for virtual navigation (VN) is highly desirable. Wedescribe our procedure for real-time navigationduring surgery for differentcerebral lesions.Materials and Methods: We performed fusion ima-ging with virtual navigation for patients undergo-ing surgery for brainlesion removal usinganultra-sound-based real-time neuro-navigation systemthat fuses intraoperative cerebral ultrasound withpreoperative MRI and simultaneously displays anMRI slice coplanar to an ioUS image.Results: 58 patients underwent surgery at our in-stitutionforintracraniallesionremovalwithimageguidance using a US system equipped with fusionimaging for neuro-navigation. In all cases the ini-tial (external) registration error obtained by thecorresponding anatomical landmark procedurewas below 2mmand the craniotomy was correctlyplaced. The transdural window gave satisfactoryUSimagequalityand thelesionwas always detect-able and measurable on both axes. Brain shift/de-formation correction has been successfully em-ployed in 42 cases to restore the co-registrationduring surgery. The accuracy of ioUS/MRI fusion/overlapping was confirmed intraoperatively underdirect visualization ofanatomiclandmarks and theerror was <3mm in all cases (100%).