Effects of cold storage on double integrating sphere optical property measurements of porcine dermis and subcutaneous fat from 400 to 1100 nm.

Significance: Accurate values of skin optical properties are essential for developing reliable computational models and optimizing optical imaging systems. However, published values show a large variability due to a variety of factors, including differences in sample collection, preparation, experimental methodology, and analysis.

Aim: We aim to explore the influence of storage conditions on the optical properties of the excised skin from 400 to 1100 nm.

Approach: We utilize a double integrating sphere system and inverse adding-doubling approach to determine absorption, ${\mu }_a$ , and reduced scattering, ${\mu }_s^{\text{'}}$ , coefficients of the porcine dermis and subcutaneous fat before and after refrigeration, freezing, or flash freezing.

Results: Our findings indicate a small average change of $-0.005$ , $-0.003$ , and $0.002{\mathrm{mm}}^{-1}$ in ${\mu }_a$ for the dermis and 0.001, $-0.003$ , and $-0.008{\mathrm{mm}}^{-1}$ for the subcutaneous tissue after refrigeration, freezing, and flash freezing, respectively, with the most notable differences observed in the hemoglobin absorption region. The value of ${\mu }_s^{\text{'}}$ shows a negligible average change of $-0.05$ , $-0.001$ , and $-0.02\hspace{0.17em}{\mathrm{mm}}^{-1}$ for the dermis, and 0.06, $-0.1$ , and $0.03{\mathrm{mm}}^{-1}$ change for the subcutaneous tissue for refrigerated, frozen, and flash-frozen samples, respectively.

Conclusions: The results provide additional context for the variability of published values of optical parameters and enable informed selection of sample storage conditions for future measurements. In addition, the results discussed here can be used to improve study planning, particularly with regard to maximizing the use of finite samples that have been collected.