Time-Resolved Diffuse Optical Spectroscopy up to 1700 nm by Means of a Time-Gated InGaAs/InP Single-Photon Avalanche Diode

Abstract:The in-vivo optical properties of the human head are investigated in the 600-1100 nm range on different subjects using continuous wave and time domain diffuse optical spectroscopy. The work was performed in collaboration with different research groups and the different techniques were applied to the same subject. Data analysis was carried out using homogeneous and layered models and final results were also confirmed by Monte Carlo simulations. The depth sensitivity of each technique was investigated and related to the probed region of the cerebral tissue. This work, based on different validated instruments, is a contribution to fill the existing gap between the present knowledge and the actual in-vivo values of the head optical properties.

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“…The system [29] developed by POLIMI (see affiliation list), used also in a variety of applications, [30][31][32] is depicted in Fig. 1(b).…”

Section: Time-resolved Broadband Spectroscopy System (Tr-spectr)mentioning

confidence: 99%

In-vivo multilaboratory investigation of the optical properties of the human head

Farina¹,

Torricelli²,

Bargigia³

et al. 2015

Biomed. Opt. Express

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“…Some research has been done on the characterization of collagen in the NIR range [13] but SPADs have never been used for singlet-oxygen detection: in fact, they are not compatible with the long time constant of singlet-oxygen decay (> 40 ns in vivo, > 3 µs for aqueous solutions) and the low photon flux expected.…”

Section: Introductionmentioning

confidence: 99%

Time-resolved singlet-oxygen luminescence detection with an efficient and practical semiconductor single-photon detector

Boso¹,

Ke²,

Korzh³

et al. 2015

Biomed. Opt. Express

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Abstract:In clinical applications, such as PhotoDynamic Therapy, direct singlet-oxygen detection through its luminescence in the near-infrared range (1270 nm) has been a challenging task due to its low emission probability and the lack of suitable single-photon detectors. Here, we propose a practical setup based on a negative-feedback avalanche diode detector that is a viable alternative to the current state-of-the art for different clinical scenarios, especially where geometric collection efficiency is limited (e.g. fiber-based systems, confocal microscopy, scanning systems etc.). The proposed setup is characterized with Rose Bengal as a standard photosensitizer and it is used to measure the singlet-oxygen quantum yield of a new set of photosensitizers for site-selective photodynamic therapy. Tower, and J. Ferraro, "Geiger-mode avalanche photodiode focal plane arrays for three-dimensional imaging LADAR," Proc. SPIE 7808, 78080C

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“…The system used is described in detail in Refs. [49,50] and allows coverage of the 600-900 nm spectral range. The diffusion constant (and absorption coefficient) can be determined from the temporal shape of the transmitted pulse.…”

Section: Diffusion Equation In Spherical Shells (Derivation Given Inmentioning

confidence: 99%

“…9 and has been described in detail in [49,50]. It consists of a supercontinuum source (SuperK Extreme, NKT) emitting mode-locked laser pulses in the range 450-1750 nm at a repetition rate of 20 MHz.…”

Section: Optical Time-of-flight Experimentsmentioning

confidence: 99%

Light diffusion in quenched disorder: Role of step correlations

Svensson

Vynck

Adolfsson³

et al. 2014

Phys. Rev. E

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We present a theoretical and experimental study of light transport in disordered media with strongly heterogeneous distribution of scatterers formed via non-scattering regions.Step correlations induced by quenched disorder are found to prevent diffusivity from diverging with increasing heterogeneity scale, contrary to expectations from annealed models. Spectral diffusivity is measured for a porous ceramic where nanopores act as scatterers and macropores render their distribution heterogeneous. Results agree well with Monte Carlo simulations and a proposed analytical model.Series of incremental random changes govern the evolution of countless systems around us, from the movement of particles and molecules [1][2][3][4] and wave propagation in disordered media [5,6], to the foraging of animals [7] and spread of disease [8]. By virtue of the central limit theorem, macroscopic evolution of such random walk processes can often be explained in terms of classical diffusion. Although therefore ubiquitous, diffusion is in each particular case determined by unique microscopic mechanisms. These mechanisms are often complex and understanding the onset and speed of diffusion is generally a challenge [9][10][11][12][13][14]. The matter is particularly relevant to research in optics of disordered media, including the study of radiative transfer through planetary atmospheres [15][16][17], optical imaging and spectroscopy in biomedical [18] and material science [19] and, more recently, anomalous diffusion in engineered disordered materials [20][21][22][23][24].Multiple scattering of light is typically viewed as a Poissonian random walk of independent and exponentially-distributed steps. This viewpoint inherently assumes a uniform random distribution of scatterers throughout the medium and results in a well-known expression for the diffusion constant [25], D = v t /3, where v is the average transport velocity for light in the medium and t the transport mean free path. This diffusivity relation, however, breaks down in systems with an heterogeneous distribution of scatterers, such as clouds, biological tissues, porous materials and foams. The reason is two-fold. First, the presence of non-scattering regions in the scattering medium leads to a broader (nonexponential) distribution of step lengths, which, in turn, induces an increase of the diffusivity [26]. Second, the quenched (i.e. spatially frozen) heterogeneity induces step correlations that tend to counteract the increase in diffusivity caused by long steps [21,26]. Due to the complexity of these aspects, understanding of light transport in systems with heterogeneous distribution of scatterers remains rather limited. Important insight has, nonetheless, been reached with the development of generalized transport equations and homogenization theory [27][28][29][30][31][32][33][34][35] as well as probabilistic analysis of random walks [26,36,37]. When it comes to quenched disorder, most works are theoretical and fall within the context of anomalous diffusion [21,23,24,[38][39][40]....

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Time-Resolved Diffuse Optical Spectroscopy up to 1700 nm by Means of a Time-Gated InGaAs/InP Single-Photon Avalanche Diode

Cited by 54 publications

References 33 publications

In-vivo multilaboratory investigation of the optical properties of the human head

In-vivo multilaboratory investigation of the optical properties of the human head

Time-resolved singlet-oxygen luminescence detection with an efficient and practical semiconductor single-photon detector

Light diffusion in quenched disorder: Role of step correlations

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