Relação dos pontos-chave cirúrgicos no crânio com áreas eloquëntes detectadas por ressonância magnética funcional / Relation of surgical key-points in skull with eloquent areas detected by functional magnetic resonance

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

Neuroimaging studies have a pivotal role in pre-surgical assessment of patients with brain lesions. Magnetic Resonance Imaging (MRI) and Computerized Tomography (CT) are established techniques providing anatomic information of the lesion and surrounding areas. Functional MRI (fMRI) is a recent method applied to probe brain function via hemodynamic response of brain regions involved in certain tasks, and thus provide useful information to the neurosurgeon. On the other hand, these new techniques have to be added to the knowledge necessary to the neurosurgery act. Ribas (2005) have established a system based on key-points aimed to guide microsurgical interventions. The system consists of anatomical relationships between points in the surfaces of the skull and the cerebrum and is reported to have errors below 2 cm of the intended cerebral sulci and giri in a post-mortem study. Nevertheless, this method does not allow for studying the relationship of the cerebral regions showing hemodynamic response to somatosensory and motor tasks. Our aim was to evaluate image fusion techniques applicable to CT, MRI and fMRI in order to verify the craniometrical relations between skull surface, cerebral surface and areas with maximal hemodynamic response to somatosensory and motor tasks. METHODS: We performed MRI and fMRI studies in ten subjects who had a CT scan performed for other reasons (8 healthy volunteers and 2 patients with localized brain lesions) using somatosensory and motor paradigms in a 3T MRI system. We have selected four out of the ten key points determined by Ribas to perform this analysis: the intersection between the inferior frontal and pre-central sulci; the intersection between the superior frontal and precentral sulci; the superior rolandic point; and the intersection between the intraparietal and post-central sulci. This choice was based on the classical localization of brain regions associated with somatossensory and motor functions. CT, MRI and fMRI data were analysed using different software packages, and the results were compared. The final goal of the process was to spatially co-register the three techniques and distance measurements in three dimensions (3D). RESULTS: we have established a pipeline using different computational processes to measure the spatial anatomic congruency between the key points shown in CT, MRI and fMRI images. We did not find a single software package enabling all the functionalities necessary to accomplish our goals. The implementation of the three imaging modalities fusion process was feasible using four public domain softwares (Osirix, Register, Mricro e FSL). We have determined the distances between the key points in four subjects (e patient). The average distance between the skull surface and brain surface points was 2.5cm (±0.6cm) and taking into account the calvarium thickness and cerebro-spinal fluid dimensions, this value is within what was observed in Ribass study. The average distance between the key points in the skull surface and the fMRI maximum response point, and the average between the brain surface and the fMRI maximum response point was larger, respectively 5.0cm (±1, 7cm) and 3.6cm (±2,1cm). These findings show that the intersubject functional variability is apparently larger then the inter-subject anatomical variability. Our results show that image fusion between CT, MRI and fMRI is possible. We believe that an increased number of subjects and appropriate statistical analysis will help to guide the possible application of this method in clinical routine.

ASSUNTO(S)

tomography x-ray computed neurosurgery magnetic resonance imaging neurocirurgia imagem por ressonância magnética tomografia computadorizada por raios x

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