Spectral characterisation of short-wave infrared (SWIR) tissue chromophores and tissue-mimicking phantom optical properties

Abstract

Significance Short-wave infrared (SWIR) sensors promise to expand the capabilities of optical sensing technologies, but the lack of robust data characterising tissue-constituent optical properties in the SWIR makes instrument design challenging. Aim We characterise and evaluate the optical properties of the dominant chromophores in tissue and tissue- mimicking phantoms, from visible to SWIR wavelengths. Approach Using single-integrating sphere systems, we measured the optical properties of single-component chromophores (H2O, haemoglobin, corn oil, synthetic melanin) and multi-component tissues (whole blood, lard), to decouple contributions from optical scattering, H2O absorption and other contributing chromophores; we also characterised commonly-used phantom materials and investigated their potential to mimic soft tissues in the SWIR range using simulations. Results We provide a consistent dataset of absorption and reduced scattering coefficients ({micro}a and {micro}'s) that characterise the dominant tissue chromophores from 450 nm out to 1600 nm. These results were shown to be consistent with literature data, where available. We integrate these data into an open-source Python toolkit, SIMPA, for optical modelling and demonstrate soft tissue simulations that can be probed continuously from visible to SWIR wavelengths. Our findings are compared with tissue-mimicking phantoms, highlighting a need for additives for polymer-based phantoms that mimic SWIR water absorption. Conclusions By providing this open-source dataset, we aim to enable future studies exploring SWIR light-tissue interactions that facilitate rapid assessment and prototyping of next-generation spectroscopy and imaging techniques.