Artifcial eur ral networks based estimation of optical parameters by diffuse reflectance imaging under in vitro conditions

Optical parameters(properties)of tissue-mimicking phantoms are determined through nonin-vasive optical imaging.Objective of this study is to decompose obtained difuse reflectance into these optical properties such as absorption and scattering coefficients.To do so,transmission spectroscopy is firstly used to measure the coefficients via an experimental setup.Next,the optical properties of each characterized phantom are input for Monte Carlo(MC)simulations to get diffuse reflectance.Also,a surface image for each single phantom with its known optical properties is obliquely captured due to reflectance-based geometrical setup using CMOS camera that is positioned at 5°angle to the phantoms.For the illumination of light,a laser light source at 633 nm wavelength is preferred,because optical properties of different components in a biological tissue on that wavelength are nonoverlapped.During in vitro measurements,we prepared 30 different mixture samples adding clinoleic intravenous lipid emulsion(CILE)and evans blue(EB)dye into a distilled water.Finally,all obtained difuse reflectance values are used to estimate the optical coefficients by artificial neural networks(ANNs)in inverse modeling.For a biological tissue it is found that the simulated and measured values in our results are in good agreement.

THE VARIATIONS OF WATER IN HUMAN TISSUE UNDER CERTAIN COMPRESSION:STUDIED WITH DIFFUSE REFLECTANCE SPECTROSCOPY

The reflectance spectrun has been widely adopted to extract diagnosis information of human tissue because it possesses the advantages of noninvasive and rapidity.The external pressure brought by fiber optic probe may influence the accuracy of measurement.In this paper,a sys-tematic study is focused on the effects of probe pressure on intrinsic changes of water and scattering particles in tissue.According to the biphasic nonlinear mixture model,the pressure modulated reflectance spectrum of both in vitro and in vivo tissue is measured and processed with second-derivation.The results indicate that the variations of bulk and bonded water in tissue have a nonlinear relationship with the pressure.Diferences in tissue structure and morphology contribute to site specific probe pressure effects.Then the finite element(FEM)and Monte Carlo(MC)method is employed to simulate the deformation and reflectance spectrum variations of tissue before and after compression.The simulation results show that as the pressure of fiber optic probe applied to the detected skin increased to 80kPa,the effective photon proportion form dermis decreases significantly from 86%to 76%.Future designs might benefit from the research of change of water volume inside the tissue to mitigate the pressure applied to skin.

Deep tissue near-infrared imaging for vascular network analysis

Subcutaneous vein network plays important roles to maintain microcirculation that is related to some diagnostic aspects.Despite developments of optical imaging technologies,still the difficulties about deep skin vascular imaging have been continued.On the other hand,since hemoglobin con-centration of human blood has key role in the veins imaging by optical manner,the used wavelength in vascular imaging,must be chosen considering absorption of hemoglobin.In this research,we constructed a near infrared(NIR)light source because of lower absorption of hemoglobin in this optical region.To obtain vascular image,reflectance geometry was used.Next,from recorded images,vascular network analysis,such as calculation of width of vascular of interest and complexity of selected region were implemented.By comparing with other modalities,we observed that proposed imaging system has great advantages including nonionized radiation,moderate penetration depth of 0.5-3 mm and diameter of 1 mm,cost-effective and algorit hmic simplicity for analysis.

Glucose detection in a highly scattering medium with diffuse photon-pair density wave

We propose a novel optical method for glucose measurement based on difuse photon-pair density wave(DPPDW)in a multiple scattering medium(MSM)where the light scattering of photon-pair is induced by refractive index mismatch between scatters and phantom solution.Experi-mentally,the DPPDW propagates in MSM via a two frequency laser(TFL)beam wherein highly correlated pairs of linear polarized photons are generated.The reduced scattering coefficientμ2s and absorption coefficientμ2a of DPPDW are measured simultaneously in terms of the amplitude and phase measurements of the detected heterodyne signal under arrangement at different dis-tances between the source and detection fibers in MSM.The results show that the sensitivity of glucose detection via glucose-induced change of reduced scattering coefficient(δμ′2)is 0.049%mM^(-1)in a 1%intralipid solution.In addition,the linear range ofδμ′2s vs glucose concentration implies that this DPPDW method can be used to monitor glucose concentration continuously and noninvasively subcutaneously.

In vivo percutaneous reflectance spectroscopy of fatty liver development in rats suggests that the elevation of the scattering power is an early indicator of hepatic steatosis

This study assessed whether there was a scat tering spectral mar ker quantifiable by reflectance measurements that could indicate early development of hepatic steatosis in rats for potential applications to pre procurement organ evaluation.Sixteen rats were fed a methionine choline-deficient(MCD)diet and eight rats were fed a normal diet.Direct assessment of the liver parenchyma of rats in vivo was performed by percut aneous reflect ance spectroscopy using a single fiber probe at the beginning of diet-intake and arbitrary post-diet-intake times up to 11 weeks to render longitudinal comparison.Histological sampling of the liver over the duration of diet adm inistration was performed on two MCD diet treated rats and one control rat eutha-nized after reflectance spectroscopy measurement.The images of hematoxylin/eosin-stained liver specimens were analyzed morphometrically to evahuate the lipid size changes associated with the level of steatosis.The MCD-diet-treated group(n=16)had mild steatosis in seven rats,moderate in three rats,severe in six rats,and no other significant pathology.No control rats(n=8)developed hepatic steatosis.Among the parameters retrieved from per-SfS,only the scat tering power(can be either positive or negative)appeared to be statist ically diferent between MCD-treated and control livers.The scattering power for the 16 MCD-diet-treated livers at the time of euthanasia and presenting various levels of steatosis was 033±0.21,in comparison to 0.036±0.25 of the eight control livers(p=0.0189).When evaluated at days 12 and 13 combined,the scattering power of the 16 MCD-diet-treated livers was 032±0.17,in comparison to 0.10±0.11 of the eight control livers(p=0.0017).All of four MCD-treated livers harvested at days 12 and 13 presented mild steatosis with sub-micron size lipid droplets,even though none of the MCD-treated livers were sonogr aphically remarkable for fatty changes.The elevation of the scattering power may be a valuable marker indicating early hepatic steatosis before the steatosis is sonographically detectable.

Three-dimensional quantication of protoporphyrin IX in photodynamic therapy using SFDI/DFT:A pilot experimental validation

Photodynamic therapy(PDT)dosimetry,induding light dose,photosensitizer dose and tissue oxygen,has been a research focus in PDT.In this work,we present a three-dimensional(3D)quantification of protoporphyrin X(PpIX)using combined spatial frequency domain imaging(SFDI)and diffuse fuorescence tomography(DFT).The SFDI maps both the distributions of tissue absorption and scattering properties at three wavelengths and accordingly provides the optical background for DFT and extracts the tissue oxygenation for assessing the therapeutic outcomes,while DFT dynamically monitors the 3D distribution of PpEX dose from measured fluorescence signals for the procedure optimization.A pilot in vrivo application in tumor nude models showed that the proposed SFDI/DFT is able to dynamically trace changes in the PpX concentration and tissue oaxygen during the treatment,rendering it a potentially powerful tool for PDT to improve clinical eficacy.

Formation Mechanism of Precursor Films at High Temperatures:A Review

The formation of a precursor flm(PF)is always coupled with better wettability;thus,clarifying the formation mechanism is required to optimize the interfacial structures.However,recent research focuses on inert wetting systems at room temperature,which cannot guide practical material processing at high temperatures.In this review,PF formation mechanisms at high temperatures were reviewed.The mechanisms are surface difusion,evaporation–condensation,subcutaneous infltration,and rapid absorption and flm overfow.In experimental metal/metal systems,the most probable mechanism is subcutaneous infltration,related to the apparent contact angle,radius,and height of the gap between the substrate metal and the oxide flm.The rapid absorption and flm overfow mechanism usually occurs in metal/ceramic systems.The PF appearance for the adsorption mechanism must satisfy the paradox,that is,the relative inertial and high-afnity liquid/solid interface.Finally,another possible mechanism of PF appearance for the reactive wetting system at high temperatures was proposed,that is,the thin-surface transport mechanism.The PF formation is sensitive to external conditions.Therefore,it is necessary to develop thermodynamic and dynamic models for predicting and simulating PFs.

An Efficient Second-Order Convergent Scheme for One-Side Space Fractional Diffusion Equations with Variable Coefficients

In this paper,a second-order fnite-diference scheme is investigated for time-dependent space fractional difusion equations with variable coefcients.In the presented scheme,the Crank-Nicolson temporal discretization and a second-order weighted-and-shifted Grünwald-Letnikov spatial discretization are employed.Theoretically,the unconditional stability and the second-order convergence in time and space of the proposed scheme are established under some conditions on the variable coefcients.Moreover,a Toeplitz preconditioner is proposed for linear systems arising from the proposed scheme.The condition number of the preconditioned matrix is proven to be bounded by a constant independent of the discretization step-sizes,so that the Krylov subspace solver for the preconditioned linear systems converges linearly.Numerical results are reported to show the convergence rate and the efciency of the proposed scheme.

High-Order Local Discontinuous Galerkin Algorithm with Time Second-Order Schemes for the Two-Dimensional Nonlinear Fractional Diffusion Equation

In this article,some high-order local discontinuous Galerkin(LDG)schemes based on some second-order θ approximation formulas in time are presented to solve a two-dimen-sional nonlinear fractional diffusion equation.The unconditional stability of the LDG scheme is proved,and an a priori error estimate with O(h^(k+1)+At^(2))is derived,where k≥0 denotes the index of the basis function.Extensive numerical results with Q^(k)(k=0,1,2,3)elements are provided to confirm our theoretical results,which also show that the second-order convergence rate in time is not impacted by the changed parameter θ.

Quantification of glucose and glycerol diffusion in myocardium

The results on determination of glucose and glycerol difusion cofficients in myocardium tissuse are presented.The method is based on the measurement and analysis of temporal dependence of tissue optical collimated transmittance umder action of a hyperosmotic agent.This temporal tissue response is related to the rate of the agent and water diffusion in a tissue.The diffusion coefficients for tssue fAuid fluxes at glucose and glycerol application to the myocardium at 20℃ have been estimated as(4.75±3.40)×10^(-7) and(7.71±4.63)×10^(-7) cm^(2)/s,respectively.

OPTICAL MEA SUREMENTS OF RAT MUSCLE SAMPLES UND ER TREATMENT WITH ETHYLENE GLYCOL AND GLUCOSE

With the objective to study the variation of optical properties of rat muscle during optical clearing,we have performed a set of optical measurements from that kind of tissue.The.measurements performed were total tr ansmittance,ollimated transmit tance,specular reflec-tance and total reflectance.This set of measurements is suficient to determine diffuse reflectance and absorbance of the sample,also necessary to est imate the optical properties.All the per formed measurements and calculated quantities will be used later in inverse Monte Carlo(IMC)simu-lations to determine the evolution of the optical properties of muscle during treatments with ethylene glycol and glucose.The results obt ained with the measurements already provide some information about the optical c learing treatments applied to the muscle and translate the mechanisms of turning the tissue more transparent and sequence of regimes of optical clearing.

Capacity Contribution Mechanism of rGO for SnO_(2)/rGO Composite as Anode of Lithium-ion Batteries

Compared with ordinary graphite anode,SnO_(2) possesses higher theoretical specifc capacity,rich raw materials and low price.While the severe volume expansion of SnO_(2) during lithium-ion extraction/intercalation limits its further application.To solve this problem,in this work the reduced graphene oxide(rGO)was introduced as volume bufer matrix of SnO_(2).Herein,SnO_(2)/rGO composite is obtained through one-step hydrothermal method.Three-dimensional structure of rGO could efectively hinder the polymerization of SnO_(2) nanoparticles and provide more lithium storage sites attributed to high specifc surface area and density defects.The initial discharge capacity of the composite cathode is 959 mA·h·g^(-1) and the capacity remained at 300 mA·h·g^(-1) after 1000 cycles at 1 C.It proved that the rGO added in the anode has a capacity contribution to the lithium-ion battery.It changes the capacity contribution mechanism from difusion process dominance to surface driven capacitive contribution.Due to the addition of rGO,the anode material gains stable structure and great conductivity.

Higher Order Collocation Methods for Nonlocal Problems and Their Asymptotic Compatibility

We study the convergence and asymptotic compatibility of higher order collocation methods for nonlocal operators inspired by peridynamics,a nonlocal formulation of continuum mechanics.We prove that the methods are optimally convergent with respect to the polynomial degree of the approximation.A numerical method is said to be asymptotically compatible if the sequence of approximate solutions of the nonlocal problem converges to the solution of the corresponding local problem as the horizon and the grid sizes simultaneously approach zero.We carry out a calibration process via Taylor series expansions and a scaling of the nonlocal operator via a strain energy density argument to ensure that the resulting collocation methods are asymptotically compatible.We fnd that,for polynomial degrees greater than or equal to two,there exists a calibration constant independent of the horizon size and the grid size such that the resulting collocation methods for the nonlocal difusion are asymptotically compatible.We verify these fndings through extensive numerical experiments.

A Local Discontinuous Galerkin Method for Two-Dimensional Time Fractional Diffusion Equations

For two-dimensional(2D)time fractional diffusion equations,we construct a numerical method based on a local discontinuous Galerkin(LDG)method in space and a finite differ-ence scheme in time.We investigate the numerical stability and convergence of the method for both rectangular and triangular meshes and show that the method is unconditionally stable.Numerical results indicate the effectiveness and accuracy of the method and con-firm the analysis.

Efects of Rare Earth on Austenite–Ferrite Phase Transformation in a Low‑Carbon Fe–C Alloy

The infuence of rare earth(RE)elements on austenite–ferrite phase transformation in Fe–0.14%C alloy has been investigated by in situ observing the nucleation,growth and morphology of ferrite using high temperature laser scanning confocal microscopy,and controlled atmosphere decarburization experiments.It is found that under the low-oxygen condition in steel,trace RE addition can signifcantly infuence the nucleation,morphology and growth of ferrite in Fe–0.14%C alloy by the combined efects of RE slowing down the carbon difusion and decreasing grain boundary energy by segregating at grain boundaries.This research provides evidences of adjusting the phase transformation and improving the mechanical properties of steels by RE addition.

Inorganic A‑site cations improve the performance of band‑edge carriers in lead halide perovskites

In lead halide perovskites,organic A-site cations are generally introduced to fne-tune the properties.One of the questions under debate is whether organic A-site cations are essential for high-performance solar cells.In this study,we compare the band edge carrier dynamics and difusion process in MAPbBr_(3)and CsPbBr_(3)single-crystal microplates.By transient absorption microscopy,the band-edge carrier difusion constants are unraveled.With the replacement of inorganic A-site cations,the difusion constant in CsPbBr_(3)increases almost 8 times compared to that in MAPbBr_(3).This work reveals that introducing inorganic A-site cations can lead to a much larger difusion length and improve the performance of band-edge carriers.

Assessing structural integrity of the pyramidal tracts with difusion spectrum imaging to predict postoperative motor function in pediatric epilepsy patients with hemispherectomy

Background:Hemispherectomy is an efective treatment option for patients with drug-resistant epilepsy caused by hemispheric lesions.However,patients often have deterioration of their motor functions postoperatively.Difusion spectrum imaging(DSI)was reliable in presenting the natural shape of the white matter fbers.At the same time,the natural sprawl pyramid tract(PT)might be more intuitive for predicting postoperative motor functions.Therefore,we assessed the motor functions by the natural shape revealed by DSI tractography.Methods:Ten children with drug-resistant epilepsy who were candidates for hemispherectomy performed DSI PTs tractography and transcranial magnetic stimulation(TMS)for motor mapping.The motor function was evaluated with muscle strength and hand grasping capability.Pyramidal tract(PT)structural integrity and TMS mapping results were compared between patients who remained stable and those with deteriorated motor functions.Receiver operating characteristic(ROC)curves with PTs asymmetric ratio were analyzed to evaluate DSI tractography diagnostic value.Results:All patients underwent DSI acquisition,while four patients successfully performed TMS.One patient had no response to TMS until the maximal machine output was reached.Four patients failed to perform TMS due to lacking cooperation.One patient was contraindicated to TMS.DSI successfully reconstructed the sharp angle fan-shaped PTs within the hemisphere.The accurate fber distribution with fber termination and thickness within the lesioned hemisphere was replicated with DSI tractography.No signifcance was found in patients’age,sex,seizure frequency,or medication between patients with stable or deteriorated postoperative motor functions.DSI efectively predicted postoperative motor function as stable with damaged PTs,mild deterioration with atrophied PTs,and intact PTs with contralateral innervation confrmed by intracranial stimulation.The area under the curve(AUC)of DSI tractography was 0.84.According to ROC,the cut-of value of PTs asymmetric ratio was 11.5%with 100%sensitivity and 75%specifcity.The sensitivity and specifcity of TMS were 2/3 and 1/2,respectively.Conclusions:The anatomic integrity of PTs with DSI tractography could efectively predict postoperative motor function after hemispherectomy.This enables neurosurgeons to inform patients and relatives about postoperative motor functions with direct morphological evidence of PTs to help them with their surgical decisions.