Estimation of porcine pancreas optical properties in the 600–1100 nm wavelength range for light-based therapies

This work reports the optical properties of porcine pancreatic tissue in the broad wavelength range of 600–1100 nm. Absorption and reduced scattering coefficients (µa and µs′) of the ex vivo pancreas were obtained by means of Time-domain Diffuse Optical Spectroscopy. We have investigated different experimental conditions—including compression, repositioning, spatial sampling, temporal stability—the effect of the freezing procedure (fresh vs frozen-thawed pancreas), and finally inter-sample variability. Good repeatability under different experimental conditions was obtained (median coefficient of variation less than 8% and ~ 16% for µa and µs′, respectively). Freezing–thawing the samples caused an irreversible threefold reduction of µs′ and no effect on µa. The absorption and reduced scattering spectra averaged over different samples were in the range of 0.12–0.74 cm−1 and 12–21 cm−1 with an inter-sample variation of ~ 10% and ~ 40% for µa and µs′, respectively. The calculated effective transport coefficient (µeff) for fresh pancreatic tissue shows that regions between 800–900 nm and 1050–1100 nm are similar and offer the lowest tissue attenuation in the considered range (i.e., µeff ranging from 2.4 to 2.7 cm−1). These data, describing specific light-pancreas interactions in the therapeutic optical window for the first time, provide pivotal information for planning of light-based thermotherapies (e.g., laser ablation) and instruction of light transport models for biophotonic applications involving this organ.