Comprehensive analysis of anatomical sites for transcutaneous bilirubin measurements in neonates using Monte Carlo multi-layered simulations.

The study utilises the Monte Carlo Multi-Layered (MCML) simulation framework to investigate the anatomical-site-specific variation in transcutaneous bilirubin (TcB) measurements in neonates. Neonatal skin was modelled as a three-layered turbid medium, and simulations were conducted to evaluate the spectral reflectance response to varying concentrations of bilirubin, melanin, and blood across four anatomical sites: forehead, abdomen, palm, and sole. The findings reveal that spectral changes are most pronounced in chromophore-dependent spectral bands, particularly between 420-520 nm for bilirubin and 500-600 nm for haemoglobin. An inverse algorithm was proposed to calculate bilirubin concentration from light reflection and validated using both simulation-generated spectra and physical skin phantoms. Results demonstrate that the forehead consistently yields the lowest relative error in bilirubin estimation, while the abdomen exhibits significant inaccuracies. The study highlights the utility of MCML in informing algorithm development and guiding sensor placement for non-invasive neonatal monitoring. These insights provide a foundational framework for the design of clinically deployable, multi-parametric TcB devices and emphasise the need for anatomical site optimisation, algorithmic calibration, and eventual clinical validation.