Abstract

Broad band light absorption spectroscopy in the visible range (520-590nm) has been carried out using implanted small optical fibers to probe the hemodynamics of deep tissues (striatum) in rat brain subjected to hypoxia. We observe a decrease of the cerebral blood oxygenation by a factor of up to two, while the cerebral blood volume (CBV) does not seem to increase significantly. However, nuclear magnetic resonance measurements of CBV in the same conditions using a magnetic contrast agent show that CBV increases by about 50%. This shows that absorption spectroscopy in the visible range strongly underestimates the CBV, probably due to the confinement of blood in vessels. This effect is confirmed by absorption spectroscopy measurements performed in phantoms with similar geometry.

© 2001 OSA/SPIE