Neurological Research A Journal of Progress in Neurosurgery, Neurology and Neurosciences ISSN: 0161-6412 (Print) 1743-1328 (Online) Journal homepage: http://www.tandfonline.com/loi/yner20 15 [ O]-water PET and intraoperative brain mapping: A comparison in the localization of eloquent cortex Federico Viñas, Lucia Zamorano, Ralph-Axel Mueller, Zhaowei Jiang, Harry Chugani, Darren Fuerst, Otto Muzik, Thomas Mangner & Fernando Diaz To cite this article: Federico Viñas, Lucia Zamorano, Ralph-Axel Mueller, Zhaowei Jiang, Harry 15 Chugani, Darren Fuerst, Otto Muzik, Thomas Mangner & Fernando Diaz (1997) [ O]-water PET and intraoperative brain mapping: A comparison in the localization of eloquent cortex, Neurological Research, 19:6, 601-608, DOI: 10.1080/01616412.1997.11740867 To link to this article: http://dx.doi.org/10.1080/01616412.1997.11740867 Published online: 20 Jul 2016. Submit your article to this journal Article views: 2 View related articles Citing articles: 2 View citing articles Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=yner20 Download by: [University of Florida] Date: 02 May 2017, At: 07:58 [ 15 0 ]-water PET and intraoperative brain mapping: A comparison in the localization of eloquent cortex Federico C. Vinas, Lucia Zamorano, Ralph-Axel Mueller*, Zhaowei Jiang, Harry Chugani*, Darren Fuerst, Otto Muzik*, Thomas j. Mangner* and Fernando G. Diaz Department of Neurosurgery, *PET Center, Children's Hospital, Wayne State University, Detroit, Ml, USA PET was performed on 12 patients with structural lesions for localization of the motor (n = 5), r 0]-water(receptive and expressive; = 6), and visual cortex (n = 1). All these patients underwent 5 n language interactive image-guided surgery using an infrared digitizer and intraoperative electrical stimulation mapping for motor, sensory, language, and visual cortex location. MRI-PET coregistration was performed using a surface matching approach that integrated functional information with interactive image guidance during the surgical procedure. An awake craniotomy with motor and sensory intraoperative stimulation was performed using a registered bipolar electrode that was tracked on real-time during the surgical procedure. Intraoperative functional findings were displayed and saved on the registered MRI images. The sites of functional PET activation during the performance of motor, visual and language tasks were then compared to the results of intraoperative cortical stimulation in 11 patients and visual evoked potentials in one. The results of the PET activation studies were concordant with the findings of intraoperative stimulation in all cases. During resection of the s-truCtural lesions, intraoperative stimulation was continued in the subcortical pathways, and five patients had positive responses on areas not identified by the functional PET. Furthermore, 3 patients showed transitory changes in function (speech arrest 1, naming difficulty 1, and , motor weakness 1) that were reversible after changing the dissection technique or a brain retractor. 5 0]water PET was reliable in identifying the motor, visual, and language cortex. Language-related rCBF increases were highly distributive, although only part of these activations were subjected to intraoperative stimulation. We conclude that 5 0]-water PET can be used for preoperative noninvasive identification of functional cortex and may be useful in neurosurgical preplanning. Intraoperative mapping still remains the main means to avoid neurological damage as it can be performed during the entire surgical procedure to avoid damage to cortex, pathways, and damage secondary to ischemia or edema (brain retraction). [Neural Res 1997; 19: 601-608] t t Keywords: Eloquent cortex; functional mapping; intraoperative localization; water PET INTRODUCTION Neurosurgical procedures rely on precise delineation of the relation between structure and function in the central nervous system. Techniques for image-guided localization are frequently being used in the surgical management of a variety of intracranial lesions including brain tumors, arteriovenous malformations, and those found in epilepsy patients 1 - 3 • Functional localization is also necessary for neurosurgical procedures near or involving eloquent cortical regions. For this group of patients, intraoperative localization can be performed either anatomically (by visual identification of anatomical landmarks) or by registered intraoperative electrical stimulation (intraoperative functional mapping). [150]water positron emission tomography is a technique that provides noninvasive localization of cortical function, in terms of task-related regional cerebral blood flow (rCBF) Correspondence and reprint requests to: LuCia Zamorano MD, Dr Med, Department of Neurosurgery, Wayne State University, 4160 john R Suite 930, Detroit, Ml 48201, USA. Accepted for publication August 1997. © 1997 Forefront Publishing Group 0161-6412/97/060601-{)8 changes. The present study attempts to validate the findings of [15 0]-water positron emission tomography ([ 15 0]-water PET) comparing its accuracy and clinical usefulness with more traditional techniques, such as the registered intraoperative mapping. Special emphasis was given to evaluate intraoperative usefulness to improve neurological outcome in patients with lesions in or around eloquent cortex. MATERIALS AND METHODS Patient population During the period January to September 1996, at Wayne State University, 18 patients with structural lesions reguiring surgical resection underwent a preoperative [ 150]-water PET scan for localization of the motor (n = 14), language (n = 15), and visual cortex (n = 1). Subsequently, they underwent an image-guided craniotomy and registered intraoperative electrical stimulation (functional mapping) and surgical resection of their intracranial lesions. In our patient group there were 6 Neurological Research, 7997, Volume 79, December 601 [1 5 0]-water PET and intraoperative brain mapping: Federico C. Vinas et al. women and 12 men . Ages ranged from 8 years to 74 years; mean age was 36.3 years. Eleven patients had brain tumors , while one patient had a cerebra l arteriovenous malform ation (AVM). The results obtained by [ 15 0]-wat er PET scan were then compared with the results of intraoperative functio nal mapping. Methodology Each patient underw ent FDG PET and [15 0]-wat er PET scans prior to surgery . The day of surgery they underw ent MRI that was registered with the PET scan using surface matching techniques. Functional volumes defined by the PET scan were transfered to the MRI images. The patients underw ent awake craniotomy, and interactive image localiza tion was done using an infrared-based system. During surgery each patient underwent intraoperative functional mapping, the results of which were compared with the positive findings obtained from the preoperative PET scan. ., [ 15 0]-wat er PET scan The [15 0]-wat er PET technique measures regional cerebral blood flow (rCBF) associated with neural activation in response t<;> sensory stimulation or cognitive tasks4 ' 5 . [ 15 0]-wat er PET was performed using a Siemens EXACT HR positron scanner (Knoxville, TN, USA) with an axial field-of -view of 15 em . The reconstructed image resolution obtained in the study was 5.5 ± 0.35 mm at full-wid th at half maxim um (FWHM) in-plane ·and 6.0 ± 0.49 mm FWHM in axial direction (reconstruction parameters: Shepp filter with 0.3 cycles/pixel cutoff frequency). A 'scout scan' was performed for determination of delay between injectio n in the antecubital vein and tracer arrival in the brain. The isotope dose for this scan was 5 mCi. An external 68 Ga line s'ource transmission scan was performed for attenuation correction. The dose for each activation scan was 25 mCi in adult patients. In children, the dose was 0.357 mCi kg- 1 of the patient's weight6 . The [15 0]-wat er dose diluted in 6 ml of normal saline was administered as a slow bolus over 20 sec, using a volume tric pump via a peripheral intravenous line. A static 60 sec scan acquisition was initiated after the delay determined in the scout scan. The stimulation/task window was 50 sec, starting 20 sec before the PET scan. A minimu m of 10 min was allowed between scans for decay of 15 0 (physical half-life 123 sec). A maxim um of 5 experimental conditions was selected for each patient according to lesion location. Each selected conditi on was scanned twice in each patient, with counterbalanced . order of repeat scans. For each patient, a selection was made according to lesion localiza tion from the followi ng set of experimental conditions: 1. Resting (with eyes closed and cqvered) . 2. Oppos ing finger- thumb movem ent of right/left · hand: Patient sequentially taps thumb with fingers of right/left hand. 602 Neurological Research, 1997, Volume 19, Decembe r 3. Listening to 10 short sentences (e.g., 'The game was very interesting', 'He'll be back in three hours') played through earphones from an analogue tape recorder. Each sentence was presented over c. 2 sec followe d by a 3 sec interval. 4. Listening and immediate repetition of 8 sentences of similar type as used for conditi on 2. Interstimulus interval in this conditi on was slightly longer to allow time for repetition . 5. Stimulation of the right/left visual half-field by means of simple geometric objects displayed on the right/left of a fixation cross on a computer monitor, which is positioned in the patient's field of view. PET data analysis For each scan, 47 transaxial image planes were reconstructed, each containing 128 x 128 pixels, with a pixel size of 1.73 x 1.73 mm and a plane separation of 3.125 mm. The volume was analyzed using the automated PET activation analysis package by Minosh ima et aJ.l' 8 , The algorithm performs an intra-subject motion correction (image coregistration), pixel normalization, pixel-by-pixel subtraction between image sets (control and stimulation), and a peak activation analysis, which provides stereotactic Talairach coordinates 9 , mean rCBF increase, z-score, and p-value for any given peak of rCBF increase. Statistical assessment is based on smoothness estimation 10 and a pooled-variance t(ZJstatistic model 11 . Subtractions serve to identify compo nents of rCBF changes associated with experimental task conditions. The followi ng subtractions were performed, according to selection of experimental conditi on: • Movem ent of the right/left hand minus resting • Listening to sentences minus resting ('language perception') • Repeating sentences minus listenin g ('language produc tion') • Stimula tion of right/le ft visual half-fie ld minus resting. MRI-PET coregistration In an effort to acquire correlated information about a patient's brain, volumes generated from different image modalities were matched to each other in Cartesian space. Current existing correlation techniques include point-p oint matching, surface matching, and volume matching. Since all our patients had their CTs and MRis done on the same day of the surgery, matching between CT and MRI was performed with implanted fiducial markers, using the point-p oint matching scheme. Since all patients had their PET studies done days before the surgery date, we used surface matching techniques, implementing JhRr's algorithm 12 in the Neurosurgical Planning System (NSPS) software. Initially, segmentation methods were used to segment brain volume out of both MRI and PET images . Brain surface images were generated from these segmented brain volumes. Then an automated algorithm was employed to align two t 0}-water PET and intraoperative brain mapping: Federico C. Viiias et al. 5 surfaces together in a three-dimensional (3-D) Cartesian space. The criteria for our alignment was to minimize the distance between two surfaces. The transformation matrix is then calculated as soon as minimum distances are reached. To increase the speed of this automatic alignment process, a distance volume called chamfer distance volume was created prior to the matching. The average accuracy of the surface matching methods is around 2.5-3.6 mm. Intraoperative interactive image localization Intraoperative interactive localization was done using an infrared detecting system developed at Wayne State University, using a 3-D opto-electronic motion analysis system (Optotrak 3-D Bar, Northern Digital, Waterloo, Canada) that uses light-emitting diodes (LEOs). Details of this system have been presented elsewhere 13- 15 • Three infrared sensors track target points defined by several miniature LEOs placed in the surgeon's instrument, in a predefined relationship referred to as a 'pointer'. Another device with several infrared emitters on it is attached to the patient's head and then mounted into the head holder or stereotactic frame ('dynamic body reference'). The dynamic body reference indicates the patient's position in relation to other LEOs, while the pointer indicates the position of the surgical instrument. With this information the system can combine the virtual patient and virtual instrument information and transmit it to the neurosurgeon. Each time the surgeon moves the instrument, three monitors mounted in the room display the instrument position on the pre-acquired computergenerated images. The surgical procedure starts by mapping the image studies with the intraoperative space (intraoperative registration). This is achieved by touching the pointer on at least three or four 'real' points that can be easily located in the pre-acquired images. We use known points of the stereotactic frame or fiducial markers. Once this is accomplished, any time the pointer is used, its tip position and trajectory are simultaneously displayed on the computer images, giving real-tjme orientation. For our patients the display was on their MRI images with the volumes of interest of functional areas defined by a [ 15 0]-water PET scan . Registered intraoperative electrical stimulation The registered intraoperative electrical stimulation involved both cortical and subcortical intraoperative mapping of motor, sensory, and language functions. Patients were positioned in the supine, semilateral, or lateral position according to the location of the lesion and surgeon's preference, and underwent an awake, centered craniotomy. Propofol anesthesia was then induced intravenously, and a local anesthetic field block was placed, using a mixture of equal volumes of 0.5 percent lidocaine and 0.25 percent bupivacaine (Marcaine), both with 1 :100,000 epinephrine 16 . This block was performed around the entire area of the planned incision. The scalp incision and centered craniotomy were then performed in the usual manner, according to the surgical preplanning protocol. During the surgical exposure, the infrared probe was used at all times to confirm the entry point, trajectory, and target localization. Before opening the dura, patients were awakened by interruption of the propofol administration. Upon exposure of the cerebral cortex, a modified bipolar probe (Neuro NSO, Fischer, Freiburg, Germany) adapted with LEOs was brought to the surgical field, for registered stimulation of language, motor, and sensory functions. All patients were awake and conversant within 6-10 min of stopping the propofol. Initially, anatomical localization was performed by touching the surface of the brain with the infrared digitizer. Each time that the pointer touched the cerebral cortex, the position of the instrument was simultaneously displayed on the MRI/PET image-reconstructions in axial, coronal, and saggittal planes. Functional localization was performed by applying an electric current to the cortical surface with the N-50 modified bipolar instrument. When searching for the primary motor cortex, stimulation was started with a frequency of 2-50 Hertz, pulses of 0.5-1 msec, and a current as low as 2 MA and usually up to 5-7 MA. When searching for sensory cortex or language, stimulation was initiated with the same settings, but the current was increased to 10-15 MA. Mapping and monitoring neurological function were continued in cortical and subcortical areas throughout the surgical procedure. A neuropsychologist was present in the operating room in all cases to assess motor, sensory, visual, and language functions during the mapping, and throughout the surgical procedure. Language functions were evaluated with standard stimuli and methods used by neurologists and neuropsychologists for the clinical assessment of aphasia. The evaluation included tests of receptive language (comprehension), repetition, and expressive language (fluency). As visual stimuli could not be presented to many patients due to position and draping, the language evaluation used auditory stimuli only. Immediately prior to electrical stimulation mapping, a thorough baseline evaluation was completed, against which performance during stimulation could be judged. As the language tasks and stimuli that were used are relatively simple and are performed perfectly by normal adults, any dysfluency, arrest, or error (i.e. paraphasic, perseverative, or inappropriate response) during stimulation mapping was considered significant. When a site tested positive, stimulation was removed until speech returned to baseline, and then retested at least once to confirm the result. Motor functions were mapped by exposing and observing the appropriate side of the patient's body, watching for involuntary muscle activity at the same frequency as the electrical stimulation. Somatosensory functions were mapped using patient self-report of somatosensory phenomena. As with language testing, sites positive for somatosensory function were retested at least once to confirm the reliability of the patient's selfreport. Neurological Research, 1997, Volume 19, December 603 [1 5 0]-water PET and intraoperative brain mapping: Federico C. Vinas et al. Visual evoked potentials are performed by presenting the patient a checkerboard pattern of black and white squares, and analyzing the occipital signal following the pattern reversal. Continuous intraoperative language monitorin g was performed in the same fashion as during stimulation mapping. Again, as the tasks used for testing were relatively simple ones usually performed perfectly by intact adults, any change from baseline performance was considered significant. Continuous monitorin g of motor functions was done using those aspects of the standard neurological motor examination that could be adapted to each patient's position, restraints, and drapes. Grip strength was also tested using a hand dynamometer. Generally, patients were able to tolerate continuous motor evaluation for periods up to 2 h without signs of significant fatigue. Any noticeable change in strength (or, in the case of grip strength, a decline greater than 20% from the baseline measurement) was considered significant. Correlation between [15 0]-water PET and registered intraoperative electrical stimulation Prior to the surgical procedure, the PET subtraction images for motor, visual, and language tasks had been superimposed onto the co-registered MRI images. Upon completion of the registered intraoperative electrical stimulation, the silhouettes corresponding to areas of eloquent cortex (recognized by registered intraoperative stimulation on 11 patients and visual evoked potentials in one), were saved as bi-dimensional coordinates, for a subsequent comparison with the bi-dimensional coordinates of the eloquent regions determined by [15 0]-water PET. Stereotactic coordinates determined by the registered intraoperative electrical stimulations were ~ransferred as volumes into the co-registered MRI/PET images. The fusion of images obtained by [15 0]-water PET and registered intraoperative electrical stimulation onto the MRI-based compute r reconstructions allowed us to perform a visual comparison with_in and between volumes determined by [15 0]-water PET and by registered intraoperative electrical stimulation, with a resolution of a few millimeters. RESULTS During the localizati on of motor function (n=5), the findings of the [ 15 0]-water PET motor activation studies were concorda nt with · the findings of intraoperative cortical stimulation in all patients. The intraoperative stimulation was continue d in the subcortical pathways, and during tumor resection . During the stimulation of subcortical areas, three patients had positive responses, manifested by movement of an extremity when the subcortical fibers were electrica lly stimulated. Since [ 15 0]-water PET primarily assesses blood flow changes on gray matter, these eloquent subcortical white matter fibers were not seen in the PET/MRI co-registered images. 604 Neurological Research, 1997, Volume 19, December During the localization for language (n = 15), a centered craniotom y was performed. This limited surgical approach did not expose all language areas identified preoperatively by the [15 0]-water PET studies. There was, however, a concordance between eloquent exposed cortex and PET. Additiona lly, while performing the registered electrical stimulation we investigated areas considered silent by the PET activation studies. Although we did not find any cortical functional area not detected by PET, during the stimulation of subcortical areas, two of the 12 patients had a temporary dysphasia, associated with the stimulation of subcortical fibers. In patient number 18 (Table 1), who had a tumor located close to the primary visual cortex, there was a concordance between the region identified by the [15 0]water PET visual activation studies and the visual evoked potentials . During the resection of structural lesions, three patients showed transitory changes in function, manifested by speech arrest in one patient, naming difficulty in another, and extremity motor weakness in a third patient, which were reversed upon temporary cessation of the tumor resection in two patients; or repositioning of the brain retractors in the third. Representative cases Case 7 A 33 year-old right-handed woman presented with a 2 month history of new-onset partial seizures involving the right-upper extremity. Her initial work-up included a CT scan and MRI which revealed an anterior left temporal mass. The neurological exam was significant for a small visual field defect, and minimal disarthria. Before the surgical procedure, the patient underwent a [ 1 5 0]-water PET for the localizati on of the expressive and receptive language cortex (Figure 1). The tumor was found to be located immediately behind the receptive language cortex. She underwe nt an awake centered craniotomy with registered intraoperative electrical stimulation. Upon superimposition of the results, there was concordance between the exposed language area and the results of [15 0]-water PET. The tumor was resected through a small corticoto my in front of the language cortex. Her post-operative course was unremarkable and she was discharged home without new neurological deficits. The pathology was consistent with anaplastic astrocytoma (patient 7). Case 2 A 30 year-old right-handed woman with generalized tonic-clo nic seizures was referred from an outside institution. Her MRI demonstrated a right posterior frontal mass, located in the neighborhood of the motor cortex. The neurological exam revealed no deficits. Before the surgical procedure, a [15 0]-water PET was performed with motor activation of the left foot (Figure 2) . The motor cortex corresponding to the left foot was found to be located just behind the mass. During the surgical procedure, findings on the registered intra- t 0}-water PET and intraoperative brain mapping: Federico C. Vinas et al. 5 Table 1: Clinical information of 18 patients 2 3 Age/sex Side Location (FOG PET) Etiology Tasks Intraoperative 31M Left Frontal Oligoastrocytoma MLR RES 61 M Left Post. Parietal 40 M Left Parietal MLR RES Anaplastic astrocytoma LR RES Astrocytoma grade II M RES 4 54 M Right Frontal 5 56 M Left Frontal Anaplastic astrocytoma MLR RES Glioblas\oma multiforme MLR RES 6 74 M Right Frontotemporal 7 33M Left Temporal Epilepsy LRGVr RES Left Fronto-temporoparietal Anaplastic astrocytoma MLR RES LR RES 8 41 M 9 33 F Left Temporal Anaplastic astrocytoma 10 53 M Left Frontoparietal Anaplastic astrocytoma MLR RES Right Ant. cingulate 01 igodendrogl ioma M RES MLR RES 11 30 F 12 47 F Bilat. Left parietal Right temporal Glioblastoma multiforme 13 22 F Left Frontotemporal AVM MLR RES RES 14 8M Left Diffuse Epilepsy MLR 15 16 F Bilat. Diffuse Epilepsy VHF VEP ? Right Diffuse Epilepsy MLR RES RES RES 16 20M 17 20M Left Diffuse Epilepsy MLR 18 16 F Right Diffuse Epilepsy MLP Ant, anterior; AVM, arteriovenous malformation; E, encoding verbal stimuli; L, listening to sentences; M, motor; Post, posterior; R, repeating sentences; RES, registered electrical stimulation; VEP, visual evoked potentials; VHF, visual half field stimulation method;Vr, visual recall operative electrical stimulation were superimposed with the [15 0]-water PET scan, and found to be concordant. The tumor was resected and the patient was discharged home without neurological deficits. The pathology was consistent with oligodendroglio ma (patient 11 ). DISCUSSION When planning the resection of cortical and subcortical structural lesions, the identification location of eloquent areas of the brain is critical 1 • Recent technological developments in surgical techniques and neuroimaging such as interactive image-guided surgical procedures have opened new frontiers in the surgical treatment of neurosurgical patients. It is possible to localize preoperatively anatomically structural lesions. By noninvasive means, speech, motor, sensory, and visual areas of the brain can be recognized. However, it is necessary to superimpose this functional information into the anatomical image, and the usefulness of this technique needs to be validated. During most intracranial procedures, eloquent cortical areas can be either anatomically or functionally identified . A frequent problem encountered during conventional anatomical localization is that anatomical landmarks (i .e. Rolandic area) are difficult to discern through the intact pia. Furthermore, in many cases the normal anatomy is distorted or displaced by edema or tumores 17 • Even with the use of interactive image guidance it is not possible to define the functional areas. In addition, there is a significant variability in the location of language areas among individuals that can _ result in post-operative deficit for some. Hemodynamic imaging methods ([ 1 s0]-water PET, fMRI), although still limited to large research centers, are becoming more accepted for functional imaging studies. Activation PET studies using intravenously administered [ 15 0]-water as the diffusible blood-flow tracer, is a noninvasive approach for the mapping of higher brain functions in humans 18 • The technique is, however, extremely expensive and not readily available in most centers. Relatively few studies have compared the reliability of hemodynamic techniques with the intraoperative registered electrical stimulation; most validation studies were based on functional MRI, and describe its usefulness for the determination of motor and language areas 19 . Other studies reported concordance between findings of functional MRI and [ 15 0]-water PET 20- 22 . The technique for cortical stimulation and mapping of language was initially developed by Penfield in 1959, for the surgical treatment of patients with epilepsy 23 • Since Penfield's original description, several modifications have been added to the technique 17' 24 • Previous studies have demonstrated that during bipolar cortical stimulation, electrical neuronal changes are confined to a few millimeters of cortex between the electrodes 25 , 26 • Most centers perform functional mapping only in the cerebral cortex, prior to tumor resection. On the other hand, in the present study, the registered intraoperative Neurological Research, 1997, Volume 19, December 605 t 0]-water PET and intraoperative brain mapping: Federico C. Vinas et al. 5 Fi~ure 1: Localization of receptive language. Simultaneous overlay of the receptive language findings obtained by [15 0]-water PET onto the T-1 PET. The receptive language was mapped while the patient was listening to sentences, and was found to be located behind the hypointense region . This was thereafter confirmed by the registered intraoperative electrical stimulation. In this patient, the localization of the receptive speech cortex allowed the resection of the tumor without new neurological deficits (patient 7) [ 1 0]-water electrical stimulation was performed in both cortical and subcortical areas, before and through the duration of the resection, in order to increase the safety of this type of procedure. The stimulation of the subcortical pathways allows us to identify and preserve 'eloquent tracts', and to prevent neurological deficits. For the same reasons, continuous monitor ing of functions are performed through the surgical procedure. [ 1 sO]-wat er activatio n PET is useful only for gray matter localiza tion (cerebral cortex and basal ganglia), where significant changes in blood flow are related to specific tasks. When functional mapping is performed only in the cerebral cortex, findings are consistent with those ."of the [ 15 0]-wate r PET activation studies. However, we found registered intraoperative electrical stimulation to be a more valuable tool for surgical procedures, since it allowed us to identify subcortical eloquent pathways, in addition to eloquent cortex. Continuous subcortical functional mapping during the tumor resection allowed us to prevent permanent deficits in three of our patients, who developed transitory changes in function . The neurosurgeon should 606 Neurological Research, 1997, Volume 19, Decembe r be aware of these important 'eloquen t tracts' rather than rely only on the preoperative cortical localization. Advances in imaging techniques have created the need for more precise navigational assistance to approach image-defined lesions. The coupling of interactive image-guidance with registered intraoperative electrical stimulation allows for optimiza tion of surgical procedures, maximiz ing the extent of resection and reducing the onset of neurological deficits. CONCLUSION [ 15 0]-wate r PET is useful in identifyi ng the motor, visual, and language cortex, as identified by the intraoperative registered electrica l stimulat ion. This techniq ue is applicable to resection of any lesion located close to eloquent areas, includin g resection for intrinsic brain tumors and vascular arteriovenous malformations, in which the goal is to maximiz e the extent of the resection with minimal risk of motor, sensory, or speech deficits. Language-related rCBF increases were highly distributive, and only some of this activati on-foci were t 0]-water PET and intraoperative brain mapping: Federico C. Vinas et al. 5 Figure 2: Loca lization of the motor cortex. Simultaneous display of the [15 0]-water PET results upon left foot activation onto the axial, sagitta l, and coronal MRI reconstructions. The green area represents the motor cortex activated during movements of the left foot. This area was concordant with the results of the registered intraoperative electrical stimulation. The tumor was resected and the patient discharged without neurological deficits (patient 11) subjected to intraoperative stimulation. 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