Functional cranial neuronavigation. Direct integration of fMRI and pet data

Objective: We report our first experiences with the direct integration of f MRI data into cranial neuronavigation. Method: For navigation we used the MKM system and thin-sliced T1 contrast e nhanced images. As a first step 21 patients had fMRI for localization of th e precentral gyrus, 2 patients for Broca area detection. By anatomical corr elation, these functional data were indirectly compared to the intraoperati ve findings using cortical SSEP (n = 20) or cortical stimulation (n = 3). E ncouraged by these preliminary results, we started the direct integration o f fMRI into neuronavigation in June 1999, followed by PET in January 2000, enabling us to compare functional images with intraoperative findings direc tly. fMRI and PET data were integrated by landmark matching referring on sk in fiducials. Meanwhile, fMRI data of 8 patients (6 motorcortex. 2 Broca) a nd PET images of 1 patient were directly integrated into neuronavigation. S ix out of 8 patients had additional cortical monitoring, 2/8 were exclusive ly operated on by functional neuronavigation. Results:Using indirect comparison between fMRI and intraoperative findings we observed a good correlation in every case for the motorcortex, but only in 1/2 for the speech area. In all 6 direct integrated fMRI cases, these fi ndings corresponded well to the conventional ones. Both patients with sole functional navigation did not have any postoperative neurological deficit. The inaccuracy of the fMRI double left right arrow T1 matching was 2.7 mm ( sigma = 0.9 mm) and 1.3 mm (sigma = 0.4 mm) of the subsequent referenciatio n of the navigation. The tumor delinement shown by 11C-methionine PET could be proven by intraoperative biopsy outside its indicated tumor margin. The inaccuracy of the PET matching was 0.8 mm. Conclusion: Functional neuronavigation enables to visualize and preserve re levant brain areas. Other functional areas like short-term memory, which so lely can be detected by fMRI might also be monitored in the future. The int egration of PET data expect to gain a better differentiation of tumor and e dema.