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 (µ(a) and µ(s)′) 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 µ(a) and µ(s)′, respectively). Freezing–thawing the samples caused an irreversible threefold reduction of µ(s)′ and no effect on µ(a). 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 µ(a) and µ(s)′, respectively. The calculated effective transport coefficient (µ(eff)) 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., µ(eff) 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

Solid phantom recipe for diffuse optics in biophotonics applications: a step towards anatomically correct 3D tissue phantoms

We present a tissue mimicking optical phantom recipe to create robust well tested solid phantoms. The recipe consists of black silicone pigment (absorber), silica microspheres (scatterer) and silicone rubber (SiliGlass, bulk material). The phantom recipe was characterized over a broadband spectrum (600-1100 nm) for a wide range of optical properties (absorption 0.1-1 cm−1, reduced scattering 5-25 cm−1) that are relevant to human organs. The results of linearity show a proper scaling of optical properties as well as the absence of coupling between the absorber and scatterer at different concentrations. A reproducibility of 4% among different preparations was obtained, with a similar grade of spatial homogeneity. Finally, a 3D non-scattering mock-up phantom of an infant torso made with the same recipe bulk material (SiliGlass) was presented to project the futuristic aspect of our work that is 3D printing human organs of biomedical relevance

Coherent fluctuations in time-domain diffuse optics

Near infrared light pulses, multiply scattered by random media, carry useful information regarding the sample key constituents and their microstructures. Usually, the photon diffusion equation is used to interpret the data, which neglects any interference effect in the detected light fields. However, in several experimental techniques, such as diffuse correlation spectroscopy or laser speckle flowmetry, the effect of light coherence is exploited to retrieve the information on the sample dynamical properties. Here, using an actively mode-locked Ti:Sapphire laser, we report the observation of temporal fluctuations in the diffused light pulse, which cannot be described by the diffusion theory. We demonstrate the sensitivity of these fluctuations on the sample dynamical properties and on the number of detected coherence areas (i.e., speckles). In addition, after interpreting the effect as a time-resolved speckle pattern, we propose a simple statistical method for its quantification. The proposed approach may enable the simultaneous monitoring of the static (absorption and scattering coefficients) and dynamical (Brownian diffusion coefficient) properties of the sample, and also provide physical insight on the propagation of optical waves in random media

Phantoms to accelerate technology development and standardization in Biophotonics

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In vivo Study of the Layered Structure on the Abdomen by Broadband Time-Domain Diffuse Optical Spectroscopy

We investigate the effect of depth heterogeneity in the abdomen by multidistance time-domain diffuse optical spectroscopy on 4 volunteers finding a higher water content in shallower regions, possibly due to fat heterogeneity and/or dermis contributions

Multi-laboratory performance assessment of diffuse optics instruments: the BitMap exercise

SIGNIFICANCE: Multi-laboratory initiatives are essential in performance assessment and standardization-crucial for bringing biophotonics to mature clinical use-to establish protocols and develop reference tissue phantoms that all will allow universal instrument comparison. AIM: The largest multi-laboratory comparison of performance assessment in near-infrared diffuse optics is presented, involving 28 instruments and 12 institutions on a total of eight experiments based on three consolidated protocols (BIP, MEDPHOT, and NEUROPT) as implemented on three kits of tissue phantoms. A total of 20 synthetic indicators were extracted from the dataset, some of them defined here anew. APPROACH: The exercise stems from the Innovative Training Network BitMap funded by the European Commission and expanded to include other European laboratories. A large variety of diffuse optics instruments were considered, based on different approaches (time domain/frequency domain/continuous wave), at various stages of maturity and designed for different applications (e.g., oximetry, spectroscopy, and imaging). RESULTS: This study highlights a substantial difference in hardware performances (e.g., nine decades in responsivity, four decades in dark count rate, and one decade in temporal resolution). Agreement in the estimates of homogeneous optical properties was within 12% of the median value for half of the systems, with a temporal stability of <5  %   over 1 h, and day-to-day reproducibility of <3  %  . Other tests encompassed linearity, crosstalk, uncertainty, and detection of optical inhomogeneities. CONCLUSIONS: This extensive multi-laboratory exercise provides a detailed assessment of near-infrared Diffuse optical instruments and can be used for reference grading. The dataset-available soon in an open data repository-can be evaluated in multiple ways, for instance, to compare different analysis tools or study the impact of hardware implementations

Interstitial null-distance time-domain diffuse optical spectroscopy using a superconducting nanowire detector

We demonstrate a novel realization of Interstitial fiber, broadband, Time Domain Diffuse Optical Spectroscopy (TD-DOS) in Null Source-Detector separation (NSDS) approach without temporal gating, by using a Superconducting Nanowire single photon detector (SNSPD) for acquisition. As per the MEDPHOT protocol, we test experimentally, the absorption linearity of the system on tissue-equivalent liquid phantoms, and demonstrate the scattering-independent retrieval of the absorption spectrum of water using Intralipid phantoms in the wavelength range of 600-1100 nm. This work has been published in the Journal of Biomedical Optics - https://doi.org/10.1117/1.JBO.28.12.121202. Here, we present the dataset containing the acquired data pertaining to the aforementioned publication, including a brief overview, the tools to read it and the analysis corresponding to the figures in the article