Monitoring angiogenesis noninvasively with near-infrared spectroscopy.

Near-infrared (NIR) spectroscopy is used to quantify cerebral blood volume (CBV) as a marker of angiogenesis (formation of new blood vessels). Rats are exposed to chronic hypoxia for 3 weeks at half atmospheric pressure to stimulate angiogenesis, and second-differential NIR spectroscopy is used to quantify total cerebral hemoglobin before and after angiogenesis. The cerebral hemoglobin (from broadband NIR spectroscopy), and the large vessel hemoglobin and hematocrit (from blood samples), are used to derive values for the calculation of CBV. The total hemoglobin in brain is 46.6+/-1.9 micromoll (mean+/-SD, n=5) preacclimation and increases by 72% postacclimation. CBV is initially 3.26+/-0.41% v/v and increases by 31% with acclimation. Each individual animal shows a measureable increase in CBV. This study indicates that NIR broadband spectroscopy can be used for repeated measurements of CBV and can be applied as a noninvasive method to study angiogenesis.