The use of near infrared light has the advantage of photon penetration. This kind of light is used in near infrared fluorescence imaging. Because there is little NIR fluorescence contrast generated by most tissues, most in vivo studies administer exogenous contrast agents. In relation to the brain, this technique can be used to map the brain vasculature, which can be useful when dealing with brain cancer for example. Assessment of post-resection margins would benefit from high sensitivity and specificity. Vascular malformations can be assessed as well. Here is a review paper describing this technique:
Frangioni John V, In Vivo near-infrared fluorescence imaging, Current opinion in chemical biology, 2003, 7: 626-634.
Adolfo Cotter, MD