An Optical Investigation of Silver Nanoclusters Composite Soda-lime Glass Formed by Electric Field Assisted Diffusion

Silver nanoclusters（NCs） embedded in soda-lime glass was synthesized by the electric fieldassisted diffusion（EFAD） and successive annealing. The samples were characterized by UV-Vis absorption spectroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy（XPS）, and lifetime measurements. The experimental results show that the growth of silver clusters is favored by the annealing temperature and dwell time. The as-diffused and annealed glass samples show photoluminescence around 550 nm under UV excitation, which can be associated with the presence of L-center and Ag3~＋ cluster. And the increasing of the annealing temperature and dwell time results in an appearance of the SPR peak and the decreasing of the luminescence intensities because the Ag3~＋ clusters grow up into the Ag nanoparticles.

Spatial sensitivity to absorption changes for various near-infrared spectroscopy methods:A compendium review

This compendium review focuses on the spatial distribution of sensitivity to localized absorption changes in optically diffuse media,particularly for measurements relevant to near-infrared spectroscopy.The three temporal domains,continuous wave,frequency domain,and time domain,each obtain different optical data types whose changes may be related to effective homogeneous changes in the absorption coefficient.Sensitivity is the relationship between a localized perturbation and the recovered effective homogeneous absorption change.Therefore,spatial sensitivity maps representing the perturbation location can be generated for the numerous optical data types in the three temporal domains.The review first presents a history of the past 30 years of work investigating this sensitivity in optically diffuse media.These works are experimental and theoretical,presenting one-,two-,and three-dimensional sensitivity maps for different Near-Infrared Spectroscopy methods,domains,and data types.Following this history,we present a compendium of sensitivity maps organized by temporal domain and then data type.This compendium provides a valuable tool to compare the spatial sensitivity of various measurement methods and parameters in one document.Methods for one to generate these maps are provided in Appendix A,including the code.This historical review and comprehensive sensitivity map compendium provides a single source researchers may use to visualize,investigate,compare,and generate sensitivity to localized absorption change maps.

Development of a handheld diffuse optical breast cancer assessment probe

Diffuse Optical Spectroscopy(DOS)is a promising non-invasive and non-ionizing technique for breast anomaly detection.In this study,we have developed a new handheld DOS probe to measure optical properties of breast tissue.In the proposed probe,the breast tissue is illuminated with four near infrared(NIR)wavelengths light emitting diodes(LED),which are encapsulated in a package(eLEDs),and two PIN photodiodes measure the intensity of the scattered photons at two di®erent locations.The proposed technique of using eLEDs is introduced,in order to have a multi-wavelength pointed-beam illumination source instead of using the laser-coupledflberoptic technique,which increases the complexity,size,and cost of the probe.Despite the fact that the proposed technique miniaturizes the probe and reduces the complexity of the DOS,the study proves that it is accurate and reliable in measuring optical properties of the tissue.The measurements are performed at the rate of 10 Hz which is suitable for dynamic measurement of biological activity,in-vivo.The multi-spectral evaluation algorithm is used to reconstruct four main absorber concentrations in the breast including oxy-hemoglobin(cHb),deoxy-hemoglobin(cHbO_(2)),water(cH2O),fat(cFat),and average scattering coeficient of the medium,as well as concentration changes in Hb(
cHb)and HbO_(2)(
cHbO_(2)).Although the probe is designed for breast cancer diagnosis,it can be used in a wide range of applications for both static and dynamic measurements such as functional brain imaging.A series of phantoms,comprised of Delrinr,Intralipidr,PierceTM and Black ink,are used to verify performance of the device.The probe will be tested on human subjects,in-vivo,in the next phase.

Handheld diffuse optical breast scanner probe for cross-sectional imaging of breast tissue

Diffuse optical spectroscopy is a relatively new,noninvasive and nonionizing technique for breast cancer diagnosis.In the present study,we have introduced a novel handheld diffuse optical breast scan(DOB-Scan)probe to measure optical properties of the breast in vivo and create functional and compositional images of the tissue.In addition,the probe gives more information about breast tissue's constituents,which helps distinguish a healthy and cancerous tissue.Two symmetrical light sources,each including four different wavelengths,are used to illuminate the breast tissue.A high-resolution linear array detector measures the intensity of the back-scattered photons at different radial destinations from the illumination sources on the surface of the breast tissue,and a unique image reconstruction algorithm is used to create four cross-sectional images for four different wavelengths.Different fromfiber optic-based illumination techniques,the proposed method in this paper integrates multi-wavelength light-emitting diodes to act as pencil beam sources into a scattering medium like breast tissue.This unique design and its compact structure reduce the complexity,size and cost of a potential probe.Although the introduced technique miniaturizes the probe,this study points to the reliability of this technique in the phantom study and clinical breast imaging.We have received ethical approval to test the DOB-Scan probe on patients and we are currently testing the DOB-Scan probe on subjects who are diagnosed with breast cancer.

Optical neuroimaging:advancing transcranial magnetic stimulation treatments of psychiatric disorders

Transcranial magnetic stimulation(TMS)has been established as an important and effective treatment for various psychiatric disorders.However,its effectiveness has likely been limited due to the dearth of neuronavigational tools for targeting purposes,unclear ideal stimulation parameters,and a lack of knowledge regarding the physiological response of the brain to TMS in each psychiatric condition.Modern optical imaging modalities,such as functional near-infrared spectroscopy and diffuse optical tomography,are promising tools for the study of TMS optimization and functional targeting in psychiatric disorders.They possess a unique combination of high spatial and temporal resolutions,portability,real-time capability,and relatively low costs.In this mini-review,we discuss the advent of optical imaging techniques and their innovative use in several psychiatric conditions including depression,panic disorder,phobias,and eating disorders.With further investment and research in the development of these optical imaging approaches,their potential will be paramount for the advancement of TMS treatment protocols in psychiatry.

DISCRIMINATION OF MENTAL WORKLOAD LEVELS IN HUMAN SUBJECTS WITH FUNCTIONAL NEAR-INFRARED SPECTROSCOPY

We have applied functional near-infrared spectroscopy(fNIRS)to the human forehead to distinguish different levels of mental workload on the basis of hemodynamic changes occurring in the prefrontal cortex.We report data on 3 subjects from a protocol involving 3 mental workload levels based on to working memory tasks.To quantify the potential of fNIRS for mental workload discrimination,we have applied a 3-nearest neighbor classification algorithm based on the amplitude of oxyhemoglobin(HbO2)and deoxyhemoglobin(HbR)concentration changes associated with the working memory tasks.We have found classification success rates in the range of 44%-72%,which are significantly higher than the corresponding chance level(for random data)of 19.1%.This work shows the potential of fNIRS for mental workload classification,especially when more parameters(rather than just the amplitude of concentration changes used here)and more sophisticated classification algorithms(rather than the simple 3-nearest neighbor algorithm used here)are considered and optimized for this application.

Transformational change in the field of diffuse optics:From going bananas to going nuts

The concept of region of sensitivity is central to the field of diffuse optics and is closely related to the Jacobian matrix used to solve the inverse problem in imaging.It is well known that,in diffuse reflectance,the region of sensitivity associated with a given source-detector pair is shaped as a banana,and features maximal sensitivity to the portions of the sample that are closest to the source and the detector.We have recently introduced a dual-slope(DS)method based on a special arrangement of two sources and two detectors,which results in deeper and more localized regions of sensitivity,resembling the shapes of different kinds of nuts.Here,we report the regions of sensitivity associated with a variety of source-detector arrangements for DS measurements of intensity and phase with frequency-domain spectroscopy(modulation frequency:140 MHz)in a medium with absorption and reduced scattering coefficients of 0.1 and 12 cm^(-1),respectively.The main result is that the depth of maximum sensitivity,considering only cases that use source-detector separations of 25 and 35 mm,progressively increases as we consider single-distance intensity(2.0mm),DS intensity(4.6mm),single-distance phase(7.5mm),and DS phase(10.9 mm).These results indicate the importance of DS measurements,and even more so of phase measurements,when it is desirable to selectively probe deeper portions of a sample with diffuse optics.This is certainly the case in non-invasive optical studies of brain,muscle,and breast tissue,which are located underneath the superficial tissue at variable depths.

NON-INVASIVE MEASUREMENT OF DEEP TISSUE TEMPERATURE CHANGES CAUSED BY APOPTOSIS DURING BREAST CANCER NEOADJUVANT CHEMOTHERAPY:A CASE STUDY

Treatment-induced apoptosis of cancer cells is one goal of cancer therapy.Interestingly,more heat is generated by mitochondria during apoptosis,especially the uncoupled apoptotic state,^(1,2) compared to the resting state.In this case study,we explore these thermal effects by longitudinally measuring temperature variations in a breast lesion of a pathological complete responder during neoadjuvant chemotherapy(NAC).Diffuse Optical Spectroscopic Imaging(DOSI)was employed to derive absolute deep tissue temperature using subtle spectral features of the water peak at 975 nm.^(3)A significant temperature increase was observed in time windows during the anthracycline and cyclophosphamide(AC)regimen but not in the paclitaxel and bevacizumab regimen.Hemoglobin concentration changes generally did not follow temperature,suggesting the measured temperature increases were likely due to mitochondrial uncoupling rather than a direct vascular effect.A simultaneous increase of tissue oxygen saturation with temperature was observed,suggesting that oxidative stress also contributes to apoptosis.Although preliminary,this study indicates longitudinal DOSI tissue temperature monitoring provides information that can improve our understanding of the mechanisms of tissue response during NAC.

Artificial neural-network-based visible light positioning algorithm with a diffuse optical channel

Visible light positioning becomes popular recently. However, its performance is degraded by the indoor diffuse optical channel. An artificial neural-network-based visible light positioning algorithm is proposed in this Letter, and a trained neural network is used to achieve positioning with a diffuse channel. Simulations are made to evaluate the proposed positioning algorithm. Results show that the average positioning error is reduced about 13 times, and the positioning time is reduced about two magnitudes. Moreover, the proposed algorithm is robust with a different field-of-view of the receiver and the refiectivity of the wall, which is suitable for various position- ing applications.

LOCAL CONVERGENCE OF AN EM-LIKE IMAGE RECONSTRUCTION METHOD FOR DIFFUSE OPTICAL TOMOGRAPHY

In this paper, an EM-like image reconstruction iterative formula specifically developed for stable external sources is rewritten as a map towards a fixed point iteration. Eocal con- vergence of the image reconstruction method is then proved. Finally a three-dimensional numerical image reconstruction example is presented.

Diffuse optical tomography in the human brain: A briefly review from the neurophysiology to its applications

The present work describes the use of noninvasive diffuse optical tomography(DOT)technology to measure hemodynamic changes,providing relevant information which helps to understand the basis of neurophysiology in the human brain.Advantages such as portability,direct measurements of hemoglobin state,temporal resolution,non-restricted movements as occurs in magnetic resonance imaging(MRI)devices mean that DOT technology can be used in research and clinical fields.In this review we covered the neurophysiology,physical principles underlying optical imaging during tissue-light interactions,and technology commonly used during the construction of a DOT device including the source-detector requirements to improve the image quality.DOT provides 3 D cerebral activation images due to complex mathematical models which describe the light propagation inside the tissue head.Moreover,we describe briefly the use of Bayesian methods for raw DOT data filtering as an alternative to linear filters widely used in signal processing,avoiding common problems such as the filter selection or a false interpretation of the results which is sometimes due to the interference of background physiological noise with neural activity.

Determination of optimal source-detector separation in measuring chromophores in layered tissue with diffuse reflectance

Based on analysis of the relation between mean penetration depth and source-detector separation in a threelayer model with the method of Monte-Carlo simulation, an optimal source-detector separation is derived from the mean penetration depth referring to monitoring the change of chromophores concentration of the sandwiched layer. In order to verify the separation, we perform Monte-Carlo simulations with varied absorption coefficient of the sandwiched layer. All these diffuse reflectances are used to construct a calibration model with the method of partial least square （PLS）. High correlation coefficients and low root mean square error of prediction （RMSEP） at the optimal separation have confirmed correctness of the selection. This technique is expected to show light on noninvasive diagnosis of near-infrared spectroscopy.

Dynamic influence of pentoxifylline on the oxygen status o Pliss＇s lymph sarcoma in rat

Tumor oxygenation is one of the key factors influencing disease prognosis and the effectiveness of treatment. Assessment of tumor oxygenation levels facil- itates the selection of optimum conditions for radiation therapy, and plays an important role in creating alternative regimes of irradiation. Treating tumors with agents capable of increasing tumor oxygenation in order to increase radiosensitivity is a promising avenue of enquiry. Diffuse optical spectroscopy （DOS） allows a noninvasive determi- nation of tissue oxygen levels based on information about the local changes in optical parameters, and the visualiza- tion of metabolic processes in the region of interest. DOS allows reconstruction of the two-dimensional distribution of main tissue chromophores that characterize the processes of oxygen supply （oxygenated hemoglobin） and oxygen consumption （deoxygenated hemoglobin）, as well as the blood oxygen saturation levels, which indirectly reflect the tissue oxygenation levels. In the present study, a hemorheologic drug, pentoxifylline, which can improve microcirculation in regions with circulatory disturbances, was used for modifying tumor tissue oxygenation. Pliss＇s lymph sarcoma （PLS）, which is characterized by rapid growth and early occurrence of necrotic areas, was chosen as a tumor model. Tumor oxygenation was monitored by DOS with parallel plane geometry. Pentoxifylline could improve tumor oxygenation by increasing the concentration of oxyhemoglobin. The increased blood oxygen saturation persisted from 30 to 120 rain after drug administration. Normal healthy tissue （muscle） and tumor tissue responded differently to the drug. DOS can be used for testing new agents that influence tissue oxygen status and blood-filling rate.