Non-invasive Measurements Of The Optical Properties In Newborn Infant Brain

Brain activity is associated with changes in optical properties of brain tissue. The measurements of optical properties in brain tissue can provide information on a variety of physiology and pathology processes. The near-infrared light could penetrate more deeply into the thick tissue make it possible to non-invasively determine the optical properties of brain. Near-infrared spectroscopy (NIRS) has been widely used in biomedical optics for more than twenty years. However, the optical properties of the head, especially the neonatal brain are not particularly well known. This work focus on the non-invasive measurements of the optical properties in new-born neonate brains. The frequency-domain NIRS instruments modulate the light with a RF sine wave, which generates diffuse photon density wave (DPDW) in turbid tissue like brain. The amplitude and phase of the DPDW change due to the absorption and scattering of the tissue. We present that the optical properties of tissue could be obtained for a single source-detector separation by comparing the tissue response to a calibration standard. Compared with the multi-distance method, this configuration is more accurate in imaging applications of macroscopically heterogeneous brain. This project involved the development and evaluation of a prototype of portable frequency-domain NIRS which could be used in clinical situations. Two kind of standard phantoms were employed in this project, including the Intralipid-Ink phantoms and solid silicon resin models. We have investigated the optical properties of the brain in forty four neonates in vivo using our frequency domain near-infrared spectroscopy (NIRS). For the first time, the distribution of optical properties and physiological parameters in normal infant brains were demonstrated.