FUNCTIONAL OPTICAL IMAGING OF BRAIN INJURY (F NIRI)

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DESCRIPTION (Adapted from Applicant's Abstract): Neurological activity underlying the function of the brain in a cognitive task can be reliably indicated by the closely associated local hemodynamic response. This response can characterize, not only functional activity, but also functional anatomy. PET is a technique that employs intravascular radio labeled positron emitting tracers and can measure regional cerebral blood flow. Functional (f)MRI uses blood oxygen level dependent imaging (BOLD) and affords information primarily dependent upon both blood oxygen, blood deoxyhemoglobin and on flow effects. For fMRI, particularly studies of the response of the primary visual cortex by photic stimulation where 5 sec after the stimulus, there is a large change of signal which is interpreted as a decrease of deoxyghemoglobin. Thus fMRI signal allows spatio and temporal coregistration and validation of the optical signal and will be used in 50 tests per year. Based upon optical studies of the exposed animal brain (Grinvald, A. et al. (1991)), both blood concentration and its oxygenation can be determined spectophotometrically. Transcranial studies of the adult human brain is made possible by photon migration techniques using continuous or rapidly modulated light, first used in the frequency domain to identify characteristics frequencies induced by functional activity of the prefrontal cortex (Change, B. et al.(1993)). Localization of the response in the pre-frontal cortex, a chronic problem with the optical method, is studied here by a 9-source, 4-detector continuous light imager (CWI) operating with a modified C.T. algorithm. This imager acquires data at 0.4 sec per point with an overall imaged acquisition and display time of ~10 sec per image. The imager gives shapes of blood oxygenation and blood concentration responses resolved to ~1 cm and showing magnitudes of response, approximately 0.1 deltaOD for sensory motor 0.03 deltaOD for occipital responses, and 0.03 deltaOD for cognitive responses based upon 182 images. The histogram displays validate the blood volume and oyxgenation increases in the pre-frontal region. The apparatus affords a measure of localized changes of these two parameters in response to a variety of cognitive tasks, particularly paired word analogies, and two types of pattern recognition. Since the apparatus is highly portable, economical and the data presented appear to be highly efficacious, basic research on pre-frontal responses of normal controls (200 tests/yr) and patients with mild traumatic injury (30 tests/yr) is proposed for year 1-4 with a more quantitative apparatus in year 3, and a hair penetrating apparatus in year 4 using fMRI co-registration as the "Gold Standard" (50/year).