Jingying Jiang

Availability of thiazone as an enhancer for optical clearing of skin tissue in vitro

Dimethyl sulfoxside (DMSO) has been used as enhancer for tissue optical clearing technique. However, due to its potential toxicity and possible side effects, taking clearing effects and clinical availability into accounts, a new enhancer will be needed in order to facilitate practical application of tissue optical clearing technique to non-invasive light-based diagnostic and imaging technique. In this talk, it is our aim to introduce a new skin penetration promoter, thiazone, used in the fields of pharmaceutic industry, cosmetic, etc and investigate its availability as a new enhancer for tissue optical clearing technique. Firstly, we analyzed its structure, physical and chemical properties. And then we performed experimental investigation of the effect of DMSO and thiazone as enhancers mixed with polyethylene glycol (PEG) respectively on optical clearing of porcine skin tissue in vitro. Results of direct observation from camera reveal that thiazone has a higher penetration enhancing effect when compared with DMSO as an enhancer when porcine skin was topically impregnated by different mixed-solutions. Optical property parameters, obtained by using double integrating-spheres system and Inverse Adding-Doubling (IAD) method, showed that thiazone led to almost similar reduction in scattering to DMSO did during the same time period. Therefore, in terms of optical application and clinical safety, thiazone could be a better choice than DMSO as an enhancer for optical clearing of skin tissue.

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

The reflectance spectrum 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 systematic 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. Differences 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 80 kPa, 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.

An analytic reflection method for time-domain fluorescence diffuse optical tomography based on a generalized pulse spectrum technique

An image reconstruction scheme for time-domain fluorescence diffuse optical tomography is proposed using a reflection-mode for a semi-infinite turbid geometry. The method is based on a generalized pulse spectrum technique that employs analytic expressions of the Laplace-transformed time-domain photon-diffusion model to construct a Born normalized inverse model, and a pair of real domain transform-factors to separate distributions of the fluorescent yield and lifetime. The methodology is validated with a specifically-developed fluorescent Monte-Carlo simulator or finite-element-based methods and its robustness to the background uncertainties is investigated.

A device to improve the SNR of the measurement of the positional floating reference point

Previous studies have preliminarily validated the floating reference method and shown that it has the potential to improve the accuracy of non-invasive blood glucose sensing by Near-Infrared Spectroscopy. In order to make this method practical, it is necessary to precisely verify and measure the existence and variation features of the positional floating reference point. In this talk, a device which can precisely verify and measure the positional floating reference point is built. Since the light intensity of diffuse reflectance from the tested sample is very weak, a multipath detecting fibers system was built to improve signal-to-noise ratio. In this system, the fibers encircle the light source fiber which is regarded as the reference center of detecting fibers while they are moving. In addition, the position of each fiber is accurately controlled by manual translation stage to keep all detecting fibers always in the same radius around light source fiber. This ensures that received signal is coming from the same radial distance of light source. The variation of signal-to-noise ratio along with the different radial distance was investigated based on experiments. Results show that the application of this device could improve signal-to-noise ratio, and provide a new experimental method for the further study of positional floating reference point.

QUANTITATIVE CONTROL OF OPTICAL CLEARING EFFECTS STUDIED WITH TISSUE-LIKE PHANTOM

Tissue optical clearing by use of optical clearing agents (OCAs) has been proven to have potential to reduce the highly scattering effect of biological tissues in optical techniques. However, the difference in tissue samples could lead to unreliable results, making it difficult to quantitatively control the dose of OCAs during the course of tissue optical clearing. In this work, in order to study the effects of optical clearing, we customized tissue-like phantoms with optical properties of some biological tissue. Diffuse reflectance and total transmittance of tissue-like phantoms with different OCAs (DMSO or glycerol) and porcine skin tissues were measured. Then optical property parameters were calculated by inverse adding-doubling (IAD) algorithm. Results showed that OCAs could lead to a reduction in scattering of tissue-like phantoms as it did to porcine skin tissue in vitro. Furthermore, a series of relational expressions could be fit to quantitatively describe the relationship between the doses of OCAs and the reduction of scattering effects. Therefore, proper tissue-like phantom could facilitate optical clearing to be used in quantitative control of tissue optical properties, and further promote the application potential of optical clearing to light-based noninvasive diagnostic and therapeutic techniques.

Potential application of Chinese traditional medicine (CTM) as enhancer for tissue optical clearing

Many biocompatible hyperosmotic agents such as dimethyl sulfoxide(DMSO) have been used as enhancers for tissue optical clearing technique. However, previous investigations showed that DMSO can induce bradycardia, respiratory problems, and alterations in blood pressure. Also, DMSO could potentially alter the chemical structure, and hence the functional properties, of cell membranes. In this talk, Borneol among natural and nontoxic CTMs was introduced as new enhancer for optical clearing of porcine skin tissue since it has been widely used as new penetration promoter in the field of trandermial drug delivery system(TDDS) and been proved to be effective. In the first, the spectral characteristics of borneol was obtained and analyzed by Fourier Transformation Infrared (FTIR) spectrophotometer. And further experimental studies were performed to probe if borneol is capable of optical clearing of porcine skin tissue in vitro with near infrared spectroscopy, double integrating-spheres system and Inverse Adding-Doubling(IAD) algorithm. Spectral results show that light penetration depth into skin tissue got the increase. Meanwhile, absorption coefficient and scattering coefficient of porcine skin treated by borneol got the decrease during the permeation of Borneol. Therefore, Borneol could be potentially used as enhancer for tissue optical clearing to improve non-invasive light-based diagnostic and imaging techniques while practically optical application and clinical safety are under consideration.

Imaging Hemodynamic Changes in Preterm Infant Brains with Two-dimensional Diffuse Optical Tomography

We present our preliminary results on two-dimensional (2-D) optical tomographic imaging of hemodynamic changes of two preterm infant brains in different ventilation settings conditions. The investigations use the established two-wavelength, 16-channel time-correlated single photon counting system for the detection, and the generalized pulse spectrum technique based algorithm for the image reconstruction. The experiments demonstrate that two-dimensional diffuse optical tomography may be a potent and relatively simple way of investigating the functions and neural development of infant brains in the perinatal period.

Frequency-domain inverse Monte Carlo simulation for the diagnosis of the early cervical cancer based on NIR diffuse measurement

This article aims at the optical parameter reconstruction technology for the frequency- domain measurement of near-infrared diffused light. For mimicking the cervix, a cylindrical model with hole in the middle is used in the simulation and experiments. Concerning the structure of the cervix, Monte-Carlo simulation is adopted for describing the photon migration in tissue and Perturbation Monte-Carlo is used for the reconstruction of the optical properties of cervix. The difficulties in the reconstruction of cervical optical properties with frequency domain measurement are the description of the tissue boundary, expression of the frequency-domain signal, and development of rapid reconstruction method for clinical use. To get the frequency domain signal in Monte Carlos simulation, discrete Fourier transformation of the photon migration history in time-domain is employed. By combining the perturbation Monte-Carlo simulation and the LM optimization technology, a rapid reconstruction algorithm is constructed, by which only one Monte-Carlo simulation is needed. The reconstruction method is validated by simulation and experiments on solid phantom. Simulation results show that the inaccuracy in reconstruction of absorption coefficient is less than 3% for a certain range of optical properties. The algorithm is also proved to be robust to the initial guess of optical properties and noise. Experimental results showed that the absorption coefficient can be reconstructed with inaccuracy of less than 10%. The absorption coefficient reconstruction for one set of measurement data can be fulfilled within one minute.

Signal processing using wavelet transform in photoacoustic tomography

In order to improve the imaging contrast and resolution in photoacoustic tomography(PAT), the deconvolution between the transducer impulse response and the recorded photoacoustic(PA) signal of the tissue phantom is often used. The suppression of noise is critical in the deconvolution. Compared with the traditional band-pass filter in Fourier domain, wiener filter is more appropriate for the wide band PA signal. The scaling parameter in wiener filter is hard to determine using the traditional Fourier domain method. To solve the problem, the deconvolution algorithm with wiener filter based on the wavelet transform is presented. The scaling parameter is estimated using discrete wavelet transform(DWT) by its multi-resolution analysis(MRA) ability. The white noise had been effectively suppressed. Both numerical simulation and experimental results demonstrated that the contrast and resolution of PA images had been improved.

Coupling between radiative transport and diffusion approximation for enhanced near-field photon-migration modeling based on transient photon kinetics

Coupling between transport theory and its diffusion approximation in subdomain-based hybrid models for enhanced description of near-field photon-migration can be computationally complex, or even physically inaccurate. We report on a physically consistent coupling method that links the transport and diffusion physics of the photons according to transient photon kinetics, where distribution of the fully diffusive photons at a transition time is provided by a computation- saving auxiliary time-domain diffusion solution. This serves as a complementary or complete isotropic source of the temporally integrated transport equation over the early stage and the diffusion equation over the late stage, respectively, fromwhich the early and late photodensities can be acquired independently and summed up to achieve steady-state modeling of the whole transport process. The proposed scheme is validated with numerical simulations for a cubic geometry.