Cerebral blood flow in an asphyxiated child is best measured by:
Ans is 'a' i.e. NIRS Frankly, we are not very sure of the answer; NIRS appears to be the best option.Near infrared spectroscopy (NIRS) is a spectroscopic method which uses the near infrared region of the electromagnetic spectrumNIRS depends on two physical properties of biological tissue:1. Biological tissue absorbs light in the near infrared spectrum (700-1000 nm) far less than visible light; photons at near infrared wavelengths are thus able to penetrate greater distances. Pulse oximeters, which use visible light, function over 1 to 2 cm. Greater photon penetrance allows NIRS to be performed over 6 or 8 cm; enough to transilluminate an infant's head.2. Brain contains only three mobile chromophore (compounds which absorb light); oxyhemoglobin, deoxyhemoglobin and cytochrome oxidase (the terminal component of the mitochondrial electron transport chain).Attenuation of transmitted light in the brain due to other causes can be assumed to be constant. Consequently any change in observed absorption is due to a change in the concentration of a mobile chromophore. Using suitable algorithms, changes in absorption can be converted into changes in concentration of the three mobile chromophore.* Thus near infrared spectroscopy derives information on cerebral hemodynamics and oxygenation from changes in the absorption of light. NIRS can be used to estimate cerebral blood flow, cerebral blood volume and other indices of cerebral hemodynamics.
NIRS
PET
Radionuclide imaging
MRI angiography
Brain Imaging: Anatomy, Trauma, and Tumors