Studies of the kinetics of cerebral metabolism and hemodynamics require fast, non-invasive neuroimaging techniques with high biochemical specificity. Although functional magnetic resonance imaging (fMRI) techniques are fast, noninvasive, and have relatively high spatial resolution, they do not provide the biochemical specificity needed to characterize the behavior of important physiological parameters such as oxy- and deoxyhemoglobin concentrations. Near-infrared spectroscopy (NIRS), however, does have the biochemical specificity necessary to measure hemodynamic changes, in terms of the concentrations of both oxy- and deoxyhemoglobin, but is typically characterized by relatively poor spatial resolution. To explore the advantages of using NIRS together with fMRI we propose the study of dynamic aspects of cerebral blood flow and metabolism by designing sensors able to perform high sensitivity simultaneous NIRS and fMRI experiments. We will use fMRI methods to determine the location of hemodynamic change and NIRS data to uncouple temporal changes in oxy- and deoxyhemoglobin and to determine the spatial location of these latter changes. As a result we expect to develop more realistic biophysical models of functional cerebral perfusion and oxidative metabolism, and to understand more fully the physiological mechanisms of the blood-oxygen-level-dependent (BOLD) effect used in fMRI. A broader impact of this project will be the further development of low-cost, noninvasive, and fast near-infrared techniques for neuroimaging. This method will allow measurement of local cerebral oxygenation and hemodynamic changes in humans and will be fully compatible with MRI instrumentation. ? ? ?
| Toronov, Vladislav Y; Zhang, Xiaofeng; Webb, Andrew G (2007) A spatial and temporal comparison of hemodynamic signals measured using optical and functional magnetic resonance imaging during activation in the human primary visual cortex. Neuroimage 34:1136-48 |
| Jacob, Mathews; Bresler, Yoram; Toronov, Vlad et al. (2006) Level-set algorithm for the reconstruction of functional activation in near-infrared spectroscopic imaging. J Biomed Opt 11:064029 |
| Gratton, Enrico; Toronov, Vladislav; Wolf, Ursula et al. (2005) Measurement of brain activity by near-infrared light. J Biomed Opt 10:11008 |
