Investigation of optical detection strategies for transabdominal fetal heart rate detection using three-layered tissue model and Monte Carlo simulation

In this paper, the Monte Carlo technique is used to determine the optical detection strategies in three-layered (maternal, amniotic fluid and fetal) tissue model. This model is utilized to estimate the transabdominal optical power and optimum source-detector (S-D) separation. Results based on the launching of 2 million photons with 1 mW optical power showed that the expected optical power output is in the range of 10-6-10-10 W/cm2 depending on S-D separation. Considering the limit of the signal processing methods (such as adaptive noise cancelling) and the use of silicon photodetector, an S-D separation of 4 cm has been selected as a practical compromise between signal level and percentage of optical power (70%) coming from the fetal layer. Based on these findings, transabdominal fetal heart rate detection system using NIR and adaptive filtering can be designed and developed.