Effects of time-gated detection in diffuse optical imaging at short source-detector separation

Contini, Davide; Mora, Alberto Dalla; Spinelli, Lorenzo; Farina, Andrea; Torricelli, Alessandro; Cubeddu, Rinaldo; Martelli, Fabrizio; Zaccanti, Giovanni; Tosi, Alberto; Boso, Gianluca; Zappa, Franco; Pifferi, Antonio

doi:10.1088/0022-3727/48/4/045401

Cited by 42 publications

(52 citation statements)

References 37 publications

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“…This effect is not ascribed to a behavior of the optical fibers like a fluorescence, but it is a well-known characteristic of the SPAD: the "diffusion tail" due to carriers absorbed outside the high electric field region of the silicon junction [32]. For the 100 and 200 mm core fibers (Figure 3a), some minor peaks are present both before and after the main peak of the curve.…”

Section: Instrument Response Functionmentioning

confidence: 93%

Towards the use of bioresorbable fibers in time‐domain diffuse optics

Sieno

Boetti

Mora

et al. 2017

Journal of Biophotonics

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In the last years bioresorbable materials are gaining increasing interest for building implantable optical components for medical devices. In this work we show the fabrication of bioresorbable optical fibers designed for diffuse optics applications, featuring large core diameter (up to 200 mm) and numerical aperture (0.17) to maximize the collection efficiency of diffused light. We demonstrate the suitability of bioresorbable fibers for timedomain diffuse optical spectroscopy firstly checking the intrinsic performances of the setup by acquiring the instrument response function. We then validate on phantoms the use of bioresorbable fibers by applying the MEDPHOT protocol to assess the performance of the system in measuring optical properties (namely, absorption and scattering coefficients) of homogeneous media. Further, we show an ex-vivo validation on a chicken breast by measuring the absorption and scattering spectra in the 500-1100 nm range using interstitially inserted bioresorbable fibers. This work represents a step toward a new way to look inside the body using optical fibers that can be implanted in patients. These fibers could be useful either for diagnostic (e. g. for monitoring the evolution after surgical interventions) or treatment (e. g. photodynamic therapy) purposes. Picture: Microscopy image of the 100 mm core bioresorbable fiber.

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Section: Instrument Response Functionmentioning

confidence: 93%

Towards the use of bioresorbable fibers in time‐domain diffuse optics

Sieno

Boetti

Mora

et al. 2017

Journal of Biophotonics

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“…16 Its shape is usually evaluated not only in terms of full-width at half maximum (FWHM, i.e., width at 0.5 of the peak value) but also down to some orders of magnitude below the peak value (i.e., 0.1 or 0.01 of the peak value), where the effect of reflections, bumps, or decay tails can enlarge the response, thus affecting performances. A first step of this work is therefore the evaluation of the laser pulse shape at different supply voltages V HV of the laser, ranging from 17 to 35 V. The setup used was composed of the laser described earlier, whose optical pulses were collected by a 1-mm silica fiber (NA ¼ 0.39, Thorlabs GmbH, Germany) that was connected to the input of a U-bracket.…”

Section: Laser Characterizationmentioning

confidence: 99%

“…Additionally, physics itself limits the development of improved CW systems since it has been demonstrated that an ultimate ideal CW system can achieve a significantly lower penetration depth in tissues with respect to an ideal TD one (∼3 cm instead of ∼6 cm for the same paradigmatic case) and orders of magnitude lower sensitivity to localized heterogeneities. 15 These ultimate performances for TD are reachable, provided that large area detectors are available in contact with the tissue under investigation (to maximize the collected light) with a proper time-gating mechanism (to reject early-arriving photons), 16 and that many pulsed sources can be arranged one close to another to maximize the injected light up to the safety limits.…”

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confidence: 99%

Miniaturized pulsed laser source for time-domain diffuse optics routes to wearable devices

et al. 2017

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, "Miniaturized pulsed laser source for time-domain diffuse optics routes to wearable devices," J. Biomed. Opt. Abstract. We validate a miniaturized pulsed laser source for use in time-domain (TD) diffuse optics, following rigorous and shared protocols for performance assessment of this class of devices. This compact source (12 × 6 mm 2 ) has been previously developed for range finding applications and is able to provide short, high energy (∼100 ps, ∼0.5 nJ) optical pulses at up to 1 MHz repetition rate. Here, we start with a basic level laser characterization with an analysis of suitability of this laser for the diffuse optics application. Then, we present a TD optical system using this source and its performances in both recovering optical properties of tissue-mimicking homogeneous phantoms and in detecting localized absorption perturbations. Finally, as a proof of concept of in vivo application, we demonstrate that the system is able to detect hemodynamic changes occurring in the arm of healthy volunteers during a venous occlusion. Squeezing the laser source in a small footprint removes a key technological bottleneck that has hampered so far the realization of a miniaturized TD diffuse optics system, able to compete with already assessed continuous-wave devices in terms of size and cost, but with wider performance potentialities, as demonstrated by research over the last two decades.

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“…32 As demonstrated in Ref. 33, the tails in the response function can seriously affect the performance of the device in TD diffuse optics in general, possibly preventing the capability to detect and localize absorption perturbations within the diffusive medium. Additionally, this long tail limits the dynamic range of the detector response function to about 2 orders of magnitude, 32 thus possibly affecting DOT reconstructions due to the reduced range suitable for data analysis.…”

Section: Introductionmentioning

confidence: 99%

Time-domain diffuse optical tomography using silicon photomultipliers: feasibility study

et al. 2016

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Abstract. Silicon photomultipliers (SiPMs) have been very recently introduced as the most promising detectors in the field of diffuse optics, in particular due to the inherent low cost and large active area. We also demonstrate the suitability of SiPMs for time-domain diffuse optical tomography (DOT). The study is based on both simulations and experimental measurements. Results clearly show excellent performances in terms of spatial localization of an absorbing perturbation, thus opening the way to the use of SiPMs for DOT, with the possibility to conceive a new generation of low-cost and reliable multichannel tomographic systems. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Effects of time-gated detection in diffuse optical imaging at short source-detector separation

Cited by 42 publications

References 37 publications

Towards the use of bioresorbable fibers in time‐domain diffuse optics

Towards the use of bioresorbable fibers in time‐domain diffuse optics

Miniaturized pulsed laser source for time-domain diffuse optics routes to wearable devices

Time-domain diffuse optical tomography using silicon photomultipliers: feasibility study

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