During brain surgery it is critical to be able to assess cortical function in order to minimize resection of eloquent areas of the brain whenever possible: Although pre-operative functional magnetic resonance imaging (fMRI) is often used to define functional areas of the cortex, it does not provide the surgeon with real-time feedback during surgery, and interpretation of the BOLD fMRI signal can be difficult. The current standard for intraoperative functional mapping is electrocortical stimulation mapping with direct observation of 'ability disruption'. However, while this technique provides real-time feedback to the surgeon, it provides only coarse (approximately 1 cm), qualitative spatial assessment of cortical function. The goal of this proposal is to develop a dual CCD based optical imaging system capable of real-time quantitative imaging of brain function during neurosurgery by imaging changes in cerebral blood flow, blood volume, hemoglobin oxygenation and oxygen metabolism. To accomplish this, laser speckle contrast imaging will be combined with multi-wavelength reflectance imaging. We will develop, in Aim 1, a laser speckle contrast imaging instrument suitable for use within the operating room, and use the instrument to image the cerebral blood flow changes during somatosensory and motor stimulation in patients undergoing neurosurgery. We will also develop and implement improved algorithms for processing and filtering of speckle contrast images to enable real-time visualization of cerebral blood flow.
In Aim 2 we will extent the capabilities of the imaging instrumentation to include multi-wavelength imaging of reflectance changes for quantitative imaging of hemoglobin volume and oxygenation changes. Together, these images will enable calculation of the stimulation-induced changes in oxygen metabolism. This unique instrument has the potential for high resolution, real-time intraoperative mapping of cortical function through multiple hemodynamic and metabolic parameters, with the potential to provide valuable guidance during neurosurgery.
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