Determination of reference values for optical properties of liquid phantoms based on Intralipid and India ink

Abstract

A multi-center study has been set up to accurately characterize the optical properties of diffusive liquid phantoms based on Intralipid and India ink at near-infrared (NIR) wavelengths. Nine research laboratories from six countries adopting different measurement techniques, instrumental set-ups, and data analysis methods determined at their best the optical properties and relative uncertainties of diffusive dilutions prepared with common samples of the two compounds. By exploiting a suitable statistical model, comprehensive reference values at three NIR wavelengths for the intrinsic absorption coefficient of India ink and the intrinsic reduced scattering coefficient of Intralipid-20% were determined with an uncertainty of about 2% or better, depending on the wavelength considered, and 1%, respectively. Even if in this study we focused on particular batches of India ink and Intralipid, the reference values determined here represent a solid and useful starting point for preparing diffusive liquid phantoms with accurately defined optical properties. Furthermore, due to the ready availability, low cost, long-term stability and batch-to-batch reproducibility of these compounds, they provide a unique fundamental tool for the calibration and performance assessment of diffuse optical spectroscopy instrumentation intended to be used in laboratory or clinical environment. Finally, the collaborative work presented here demonstrates that the accuracy level attained in this work for optical properties of diffusive phantoms is reliable.

Computationally effective solution of the inverse problem in time-of-flight spectroscopy

“…This value matches perfectly with the presented value by Ninni et al [42]. Our results also fall within the range of specific absorption coefficients presented in [43] with large batch to batch deviations recorded. As it may be expected [28], LKM and WMC evaluated μ s ′ remains fairly constant with measurement precision within 5% whereas a μ grows linearly in proportion to the added ink volume.…”

Fast silicon photomultiplier improves signal harvesting and reduces complexity in time-domain diffuse optics

“…The center of the cylinder is placed at a depth z within a homogeneous liquid phantom based on a water dilution of Intralipid-20% as diffusive medium and India ink as absorber. The reduced scattering coefficient for Intralipid and the absorption coefficient for ink have been widely characterized, using both CW apparatuses [32,33] and TD systems [34], reaching a consensus estimate among many laboratories worldwide better than 3% [35]. For the following measurements, a liquid phantom with μ a = 0.1 cm −1 and μ s ' = 10 cm −1 is employed as bulk medium in which the perturbation is placed.…”

Chromophore decomposition in multispectral time-resolved diffuse optical tomography

“…Currently, the most advanced multilaboratory validation of phantom materials for Diffuse Optics relies on water dilution of Intralipid and ink [21]. Nevertheless, optical phantoms containing heterogeneities are difficult to obtain and each lab has its own protocol [21,23].…”

“…Nevertheless, optical phantoms containing heterogeneities are difficult to obtain and each lab has its own protocol [21,23]. For purely absorbing inclusions assessed at a single wavelength we preferred the Equivalent Black Volume (EBV) approach, which can mimic a wide Equivalence Class of realistic perturbations with different combination of volume, shape and absorption changes [24,25].…”