| A dual wavelength time-resolved reflectance system was developed for monitoring hemoglobin saturation noninvasively. The ability of the system to determine the optical properties of tissue-simulating phantoms was examined. To quantify the accuracy of the technique in monitoring hemoglobin saturation, measurements were performed in a homogeneous phantom containing human erythrocytes in a scattering solution. The hemoglobin saturation of this phantom could be controlled and monitored with an alternate technique. After system validation in this simple model, a more realistic, two-layer phantom model was investigated. The top layer was chosen to simulate either skin or fat and the oxygenation of the bottom layer, which corresponded to muscle, was controlled. The thickness of the fat layer was varied from 1.5 to 10 mm to investigate the effects of increasing the top layer thickness. Time-resolved measurements of reflectance, performed through the top layer were analyzed with a simple homogeneous diffusion model to quantify the hemoglobin saturation of the bottom layer. These data were compared with simultaneous measurements of oxygenation made directly in the bottom layer. Errors in estimating hemoglobin saturation with this method ranged from 5–11% depending on top layer thickness. Preliminary in vivo measurements were also undertaken which demonstrated promising results, although no comparative technique was used in these studies. |
