Feasibility of frequency domain NIR spectrometer to measure fetal cerebral blood oxygenation in utero

We present a preliminary assessment of the feasibility of using a frequency domain spectrometer for measuring fetal cerebral blood oxygenation in-utero at 750 and 780 nm of modulation at 70 MHz. The amplitude and phase of the diffuse photon density wave which propagates through the tissue is detected by a photomultiplier tube. The absorption coefficient ?a and the reduced scattering coefficient ?'s are calculated based on the analytic solution of the photon diffusion equation for a semi-infinite geometry. The accuracy of the instrument and the algorithm in measuring ?a is tested by an experiment performed on a homogeneous ink/intralipid tissue phantom. Also the sensitivity of the system to the change of blood volume and oxgenation is evaluated through a homogeneous blood/intralipid tissue phantom experiment. Clinical data was recorded during the elective Cesarean section of human subjects. The measurements were made on maternal abdomen in the post-epidural stage and on the fontanel region of neonate before (pre-cord) and after (post-cord) the umbilical cord was detached. The source detector separation used were 7 and 3(or 4) cm respectively. The deoxygenated and oxygenated hemoglobin concentration, blood volume and saturation were calculated based on ?a of 2 wavelength. The averaged optical properties and blood parameters for each stage are presented. The post-epidural blood saturation value correlates well with the pre-cord saturation value. A larger number of human subjects are being evaluated to provide statistically significant results.