F. Experimental Protocols
VIII. Problems and Perspectives
This book covers the methods for functional brain imaging. Assuming that all neuroimaging approaches are available and one could freely choose one’s instrument, where is the role of near-infrared spectroscopy and imaging? Table 2 gives an overview of advantages and dis- advantages of NIR methods and indicates most likely appli- cations of the method.
The most significant disadvantages are the relatively poor spatial resolution (on the order of centimeters) and the limited depth penetration (probably mostly confined to the cortex). The most important advantages are the biochemical specificity of the signals and the flexibility of the approach.
Table 2
Advantage Disadvantage Research application Potential clinical application
Good temporal resolution Poor spatial resolution Neurovascular coupling (linearity, Assessment of disturbed neurovascular individual determination of coupling in neurological disorders coupling index? etc.)
Biochemically defined Poor depth penetration Functional imaging in babies, Monitoring of cerebral oxygenation in
measurement parameters children comatose patients in intensive care unit
Assessment of intra vascular Susceptibility to artifacts Functional imaging in “natural” Monitoring of tissue at risk during surgery and intracellular metabolic situation (walking, standing, etc.) or after stroke (ischemic penumbra) events and neuronal activity
High flexibility (bedside Add-on information to f MRI and Detection of hematoma (epidural, subdural)
examination) PET studies (Cyt-Ox, fast signals)
Extremely good sensitivity to Molecular imaging in the mouse Molecular imaging in neurological disorders
small concentrations brain
Furthermore, the ability to detect extremely small substance concentrations should give the perspective of an alternative to PET. In rodent studies, cross-sectional optical CT for detection of fluorescent tracers (Ntziachristos and Weissleder, 2001) is feasible; in humans, it is questionable whether information about the entire brain can be obtained;
however, the cortex should also be accessible to molecular studies.
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7
Dynamic Measurements
of Local Cerebral Blood Flow:
Examples from Rodent Whisker Barrel Cortex
Thomas A. Woolsey, Ling Wei, and Joseph P. Erinjeri
Departments of Neurology and Neurological Surgery, Washington University School of Medicine, St. Louis, Missouri 63110