Heat sensitive microbubbles for intraoperative assessment of cancer ablation margin
Author(s):
Jiwei Huang;
Jeff S. Xu;
Carl Schmidt;
Ronald X. Xu
Show Abstract
We developed a heat-sensitive microbubble (HSM) agent for intraoperative assessment of
thermal ablation margins in cancer ablation therapies. The HSM agent, comprising a core
of liquid perfluorocarbon (PFC) compound and a shell of biodegradable poly lactic-coglycolic
acid (PLGA), was fabricated using an emulsion evaporation method. In our
previous study, significant increase of ultrasound contrast was observed after heat
activation of HSMs. In this study, intraoperative ultrasonic assessment of thermal
ablation margins by HSMs was demonstrated in vivo in a pig model. HSMs were
delivered to the pig liver by portal vein injection. Liver ablation was done using a RF
ablation probe. Intraoperative ultrasound imaging with HSMs clearly delineated the
ablation margin. Fluorescence images of liver tissue samples confirmed the existence and
activation of HSMs. This result demonstrated that the HSM agent can be potentially
utilized as a multimodal contrast agent for intraoperative ultrasonic and fluorescence
assessment of thermal ablation margins in cancer ablation therapies.
PH-sensitive fluorescence detection by diffuse fluorescence tomography
Author(s):
Jiao Li;
Feng Gao;
Linjing Duan;
Xin Wang;
Limin Zhang;
Huijuan Zhao
Show Abstract
The importance of cellular pH has been shown clearly in the study of cell activity, pathological feature, drug metabolism,
etc. Monitoring pH changes of living cells and imaging the regions with abnormal pH values in vivo could provide the
physiologic and pathologic information for the research of the cell biology, pharmacokinetics, diagnostics and
therapeutics of certain diseases such as cancer. Thus, pH-sensitive fluorescence imaging of bulk tissues has been
attracting great attention in the regime of near-infrared diffuse fluorescence tomography (DFT), an efficient small-animal
imaging tool. In this paper, the feasibility of quantifying pH-sensitive fluorescence targets in turbid medium is
investigated using both time-domain and steady-state DFT methods. By use of the specifically designed time-domain and
continuous-wave systems and the previously proposed image reconstruction scheme, we validate the method through
2-dimensional imaging experiments on a small-animal-sized phantom with multiply targets of distinct pH values. The
results show that the approach can localize the targets with reasonable accuracy and achieve quantitative reconstruction
of the pH-sensitive fluorescent yield.
Mammogram-based diffuse optical tomography
Author(s):
Hung-Chih Chiang;
Jhao-Ming Yu;
Liang-Yu Chen;
Min-Cheng Pan;
Sheng-Yih Sun;
Chia-Cheng Chou;
Min-Chun Pan
Show Abstract
The study aims at developing an optical measurement module incorporated with an X-ray mammographic
system to obtain diffuse optical images (DOI) for the detection of breast tumors. Two goals steer the study: (1) to
enhance sensitivity and specificity of tumor detection through the use of functional DOI; and (2) to reduce radiation
exposure by using only one mammogram, instead of two, as structure information to compute optical-coefficient
images. A dual-direction (downward and upward) scanning device to project illuminated near infrared light with
multiple-channel switching for both sources and detectors was designed and constructed to obtain double information.
The designed and constructed NIR scanning module incorporates with GE Senographe 2000D to assist breast tumor
detection.
In vivo quantification of human dermal skin aging using SHG and autofluorescence
Author(s):
Stefan Puschmann;
Christian-Dennis Rahn;
Horst Wenck;
Stefan Gallinat;
Frank Fischer
Show Abstract
There are visible changes during skin aging. In the extracellular matrix these changes referred to as intrinsic aging (skin areas not exposed to sunlight) and extrinsic aging can be measured using various methods, such as subjective clinical evaluation, histology and molecular analysis. In this study we developed a new parameter for the non-invasive quantitative determination of dermal skin aging utilizing a five-dimensional intravital tomography (5D-IVT). This device, also known as 5D - multi-photon laser scanning microscopy, is a powerful tool to investigate (photo)aging-associated
alterations in vivo.
Structural alterations in the dermis of extrinsically aged (chronically sun-exposed) and intrinsically aged (sun-protected) human skin were recorded utilizing the collagen-specific second harmonic generation (SHG) signal and the elastin-specific autofluorescence (AF) signal. Recording took place in young and elderly volunteers. The resulting images were processed in order to gain the elastin percentage and the collagen percentage per image. Then, the elastin - to - collagen ratio (ELCOR) was calculated. With respect to volar forearm skin, the ELCOR significantly increased with age. In elderly volunteers, the ELCOR value calculated for the chronically sun-exposed temple area was significantly augmented compared with the sun-protected upper arm area.
Based on 5D-IVT we introduce the ELCOR as a new means to quantify age-associated alterations in the extracellular matrix of in vivo human skin. This novel parameter is compared to the currently
used "SHG to AF aging index" of the dermis (SAAID).
Multimodal full-field optical coherence tomography on biological tissue: toward all optical digital pathology
Author(s):
F. Harms;
E. Dalimier;
P. Vermeulen;
A. Fragola;
A. C. Boccara
Show Abstract
Optical Coherence Tomography (OCT) is an efficient technique for in-depth optical biopsy of biological tissues, relying
on interferometric selection of ballistic photons. Full-Field Optical Coherence Tomography (FF-OCT) is an alternative
approach to Fourier-domain OCT (spectral or swept-source), allowing parallel acquisition of en-face optical sections.
Using medium numerical aperture objective, it is possible to reach an isotropic resolution of about 1x1x1 ìm. After
stitching a grid of acquired images, FF-OCT gives access to the architecture of the tissue, for both macroscopic and
microscopic structures, in a non-invasive process, which makes the technique particularly suitable for applications in
pathology. Here we report a multimodal approach to FF-OCT, combining two Full-Field techniques for collecting a
backscattered endogeneous OCT image and a fluorescence exogeneous image in parallel. Considering pathological
diagnosis of cancer, visualization of cell nuclei is of paramount importance. OCT images, even for the highest resolution,
usually fail to identify individual nuclei due to the nature of the optical contrast used. We have built a multimodal optical
microscope based on the combination of FF-OCT and Structured Illumination Microscopy (SIM). We used x30 immersion objectives, with a numerical aperture of 1.05, allowing for sub-micron transverse resolution. Fluorescent staining of nuclei was obtained using specific fluorescent dyes such as acridine orange. We present multimodal images of healthy and pathological skin tissue at various scales. This instrumental development paves the way for improvements of standard pathology procedures, as a faster, non sacrificial, operator independent digital optical method compared to frozen sections.
Combined FLIM and reflectance confocal microscopy for epithelial imaging
Author(s):
Joey M. Jabbour;
Shuna Cheng;
Sebina Shrestha;
Bilal Malik;
Javier A. Jo;
Brian Applegate;
Kristen C. Maitland
Show Abstract
Current methods for detection of oral cancer lack the ability to delineate between normal and precancerous tissue
with adequate sensitivity and specificity. The usual diagnostic mechanism involves visual inspection and palpation
followed by tissue biopsy and histopathology, a process both invasive and time-intensive. A more sensitive and
objective screening method can greatly facilitate the overall process of detection of early cancer. To this end, we
present a multimodal imaging system with fluorescence lifetime imaging (FLIM) for wide field of view guidance
and reflectance confocal microscopy for sub-cellular resolution imaging of epithelial tissue. Moving from a 12 x 12
mm2 field of view with 157 ìm lateral resolution using FLIM to 275 x 200 μm2 with lateral resolution of 2.2 μm using confocal microscopy, hamster cheek pouch model is imaged both in vivo and ex vivo. The results indicate that
our dual modality imaging system can identify and distinguish between different tissue features, and, therefore, can
potentially serve as a guide in early oral cancer detection..
Optical characters and texture maps of skin and the aging mechanism by use of multiphoton microscopy and optical coherence tomography
Author(s):
Shulian Wu;
Hui Li;
Xiaoman Zhang;
Yudian Huang;
Xiaohui Xu
Show Abstract
Cutaneous aging is a complicated biological process affecting different constituents of
skin, which can be divided into two types: the chronological aging and the photo-aging. The two
cutaneous aging processes often co-exist accompanying with each other. The effects are often
overlapped including changes in epithelium and dermis. The degeneration of collagen is a major
factor in dermal alteration with aging. In this study, multiphoton microscopy (MPM) with its high
resolution imaging and optical coherence tomography (OCT) with its depth resolved imaging were
used to study the anti-aging dermatology in vivo. It was attempted to make the optical parameter
and texture feature to evaluate the process of aging skin using mathematical image processing.
The links among optical parameter, spectrum and texture feature in collagen with aging process
were established to uncover mechanism of aging skin.
Quantifying the cortical contribution to the NIRS signal using simultaneous NIRS-BOLD measurements
Author(s):
Louis Gagnon;
Meryem A. Yücel;
Mathieu Dehaes;
Robert J. Cooper;
Katherine L. Perdue;
Juliette Selb;
David A. Boas
Show Abstract
Near-Infrared Spectroscopy (NIRS) measures the functional hemodynamic response occuring at the surface of
the cortex. Large pial veins are located above the surface of the cerebral cortex. Following activation, these
veins exhibit oxygenation changes but their volume likely stays constant. The back-reflection geometry of the
NIRS measurement renders the signal very sensitive to these superficial pial veins. As such, the measured NIRS
signal contains contributions from both the cortical region as well as the pial vasculature. In this work, the
cortical contribution to the NIRS signal was investigated using (1) Monte Carlo simulations over a realistic
geometry constructed from anatomical and vascular MRI and (2) multimodal NIRS-BOLD recordings during
motor stimulation. A good agreement was found between the simulations and the modeling analysis of in vivo
measurements. Our results suggest that the cortical contribution to the deoxyhemoglobin signal change (ΔHbR)
is equal to 16-22% of the cortical contribution to the total hemoglobin signal change (ΔHbT). Similarly, the
cortical contribution of the oxyhemoglobin signal change (ΔHbO) is equal to 73-79% of the cortical contribution
to the ΔHbT signal. These results suggest that ΔHbT is far less sensitive to pial vein contamination and
therefore, it is likely that the ΔHbT signal provides better spatial specificity and should be used instead of
ΔHbO or ΔHbR to map cerebral activity with NIRS. While different stimuli will result in different pial vein
contributions, our finger tapping results do reveal the importance of considering the pial contribution.
Fluorescence-enhanced optical tomography and nuclear imaging system for small animals
Author(s):
I-Chih Tan;
Yujie Lu;
Chinmay Darne;
John C. Rasmussen;
Banghe Zhu;
Ali Azhdarinia;
Shikui Yan;
Anne M. Smith;
Eva M. Sevick-Muraca
Show Abstract
Near-infrared (NIR) fluorescence is an alternative modality for molecular imaging that has been demonstrated in animals
and recently in humans. Fluorescence-enhanced optical tomography (FEOT) using continuous wave or frequency
domain photon migration techniques could be used to provide quantitative molecular imaging in vivo if it could be
validated against "gold-standard," nuclear imaging modalities, using dual-labeled imaging agents. Unfortunately,
developed FEOT systems are not suitable for incorporation with CT/PET/SPECT scanners because they utilize benchtop
devices and require a large footprint. In this work, we developed a miniaturized fluorescence imaging system installed in
the gantry of the Siemens Inveon PET/CT scanner to enable NIR transillumination measurements. The system consists
of a CCD camera equipped with NIR sensitive intensifier, a diode laser controlled by a single board compact controller,
a 2-axis galvanometer, and RF circuit modules for homodyne detection of the phase and amplitude of fluorescence
signals. The performance of the FEOT system was tested and characterized. A mouse-shaped solid phantom of uniform
optical properties with a fluorescent inclusion was scanned using CT, and NIR fluorescence images at several
projections were collected. The method of high-order approximation to the radioactive transfer equation was then used to
reconstruct the optical images. Dual-labeled agents were also used on a tumor bearing mouse to validate the results of
the FEOT against PET/CT image. The results showed that the location of the fluorophore obtained from the FEOT
matches the location of tumor obtained from the PET/CT images. Besides validation of FEOT, this hybrid system could
allow multimodal molecular imaging (FEOT/PET/CT) for small animal imaging.
Time-reversal optical tomography: detecting and locating extended targets in a turbid medium
Author(s):
Binlin Wu;
W. Cai;
M. Xu;
S. K. Gayen
Show Abstract
Time Reversal Optical Tomography (TROT) is developed to locate extended target(s) in a highly scattering turbid
medium, and estimate their optical strength and size. The approach uses Diffusion Approximation of Radiative Transfer
Equation for light propagation along with Time Reversal (TR) Multiple Signal Classification (MUSIC) scheme for
signal and noise subspaces for assessment of target location. A MUSIC pseudo spectrum is calculated using the
eigenvectors of the TR matrix T, whose poles provide target locations. Based on the pseudo spectrum contours, retrieval
of target size is modeled as an optimization problem, using a "local contour" method. The eigenvalues of T are related to
optical strengths of targets.
The efficacy of TROT to obtain location, size, and optical strength of one absorptive target, one scattering target, and
two absorptive targets, all for different noise levels was tested using simulated data. Target locations were always
accurately determined. Error in optical strength estimates was small even at 20% noise level. Target size and shape were
more sensitive to noise. Results from simulated data demonstrate high potential for application of TROT in practical
biomedical imaging applications.
Towards single snapshot multispectral skin assessment
Author(s):
Janis Spigulis;
Dainis Jakovels;
Liene Elste
Show Abstract
Skin assessment technology based on comparative analysis of single-pixel RGB signal values at poly-chromatic
illumination has been proposed. Multi-spectral imaging information from a single snapshot RGB image data set with the
inter-channel crosstalk correction can be extracted this way. Proof-of-concept evaluations and measurement results are
presented and discussed. Potential of bi-chromatic illumination for skin hemoglobin mapping during arterial occlusion
test has been demonstrated.
Coaxial electrospray for multimodal imaging and image-guided therapy
Author(s):
Ting Si;
Leilei Zhang;
Guangbin Li;
Cynthia J. Roberts;
Laibin Jia;
Xiezhen Yin;
Ronald Xu
Show Abstract
Recent development in multimodal imaging and image-guided therapy requires multifunctional microparticles that
encapsulate several imaging and therapeutic agents in the same carrier for simultaneous detection and treatment of the
diseases. However, commonly used microfabrication processes for these microparticles have multiple limitations such as
the low encapsulation efficiency and the loss of bioactivity for the encapsulated biological cargos. To overcome these
limitations, we have carried out both the experimental and the theoretical studies on coaxial electrospray of
poly(lactide-co-glycolide) PLGA microparticles. On the experimental side, a coaxial electrospray setup has been
developed and tested. The setup consists of a customized coaxial needle assembly, two ring electrodes, two high-voltage
power supplies, two syringe infusion pumps, a particle collection reservoir, and a process monitoring system. On the
theoretical side, a classical normal mode method has been used for instability analysis of the coaxial electrified jet based
on the experimental parameters. The effects of different dimensionless process parameters on the formation of different
unstable modes have also been studied. The reported research represents the first step toward the quantitative control and
optimization of the coaxial electrospray process for the fabrication of multifunctional microparticles in multimodal
imaging and image-guided therapy.
Combined three-dimensional computer vision and epi-illumination fluorescence imaging system
Author(s):
Dimitris Gorpas;
Dido Yova;
Kostas Politopoulos
Show Abstract
Most of the reported fluorescence imaging methods and systems highlight the need for three-dimensional information of
the inspected region surface geometry. The scope of this manuscript is to introduce an epi-illumination fluorescence
imaging system, which has been enhanced with a binocular machine vision system for the translation of the inverse
problem solution to the global coordinates system. The epi-illumination fluorescence imaging system is consisted of a
structured scanning excitation source, which increases the spatial differentiation of the measured data, and a telecentric
lens, which increases the angular differentiation. On the other hand, the binocular system is based on the projection of a
structured light pattern on the inspected area, for the solution of the correspondence problem between the stereo pair. The
functionality of the system has been evaluated on tissue phantoms and calibration objects. The reconstruction accuracy
of the fluorophores distribution, as resulted from the root mean square error between the actual distribution and the
outcome of the forward solver, was more than 80%. On the other hand, the surface three-dimensional reconstruction of
the inspected region presented 0.067±0.004 mm accuracy, as resulted from the mean Euclidean distance between the
three-dimensional position of the real world points and those reconstructed.
Construction of the Jacobian matrix for fluorescence diffuse optical tomography using a perturbation Monte Carlo method
Author(s):
Xiaofeng Zhang
Show Abstract
Image formation in fluorescence diffuse optical tomography is critically dependent on construction of the Jacobian
matrix. For clinical and preclinical applications, because of the highly heterogeneous characteristics of the medium,
Monte Carlo methods are frequently adopted to construct the Jacobian. Conventional adjoint Monte Carlo method
typically compute the Jacobian by multiplying the photon density fields radiated from the source at the excitation
wavelength and from the detector at the emission wavelength. Nonetheless, this approach assumes that the source and
the detector in Green's function are reciprocal, which is invalid in general. This assumption is particularly questionable
in small animal imaging, where the mean free path length of photons is typically only one order of magnitude smaller
than the representative dimension of the medium. We propose a new method that does not rely on the reciprocity of the
source and the detector by tracing photon propagation entirely from the source to the detector. This method relies on the
perturbation Monte Carlo theory to account for the differences in optical properties of the medium at the excitation and
the emission wavelengths. Compared to the adjoint methods, the proposed method is more valid in reflecting the
physical process of photon transport in diffusive media and is more efficient in constructing the Jacobian matrix for
densely sampled configurations.
Hybrid light transport model based bioluminescence tomography reconstruction for early gastric cancer detection
Author(s):
Xueli Chen;
Jimin Liang;
Hao Hu;
Xiaochao Qu;
Defu Yang;
Duofang Chen;
Shouping Zhu;
Jie Tian
Show Abstract
Gastric cancer is the second cause of cancer-related death in the world, and it remains difficult to cure because it has
been in late-stage once that is found. Early gastric cancer detection becomes an effective approach to decrease the gastric
cancer mortality. Bioluminescence tomography (BLT) has been applied to detect early liver cancer and prostate cancer
metastasis. However, the gastric cancer commonly originates from the gastric mucosa and grows outwards. The
bioluminescent light will pass through a non-scattering region constructed by gastric pouch when it transports in tissues.
Thus, the current BLT reconstruction algorithms based on the approximation model of radiative transfer equation are not
optimal to handle this problem. To address the gastric cancer specific problem, this paper presents a novel reconstruction
algorithm that uses a hybrid light transport model to describe the bioluminescent light propagation in tissues. The
radiosity theory integrated with the diffusion equation to form the hybrid light transport model is utilized to describe
light propagation in the non-scattering region. After the finite element discretization, the hybrid light transport model is
converted into a minimization problem which fuses an l1 norm based regularization term to reveal the sparsity of
bioluminescent source distribution. The performance of the reconstruction algorithm is first demonstrated with a digital
mouse based simulation with the reconstruction error less than 1mm. An in situ gastric cancer-bearing nude mouse based
experiment is then conducted. The primary result reveals the ability of the novel BLT reconstruction algorithm in early
gastric cancer detection.
Bimodal BLT source reconstruction based on adjoint diffusion equations
Author(s):
Yanbin Hou;
Jimin Liang;
Xiaochao Qu;
Duofang Chen;
Shouping Zhu;
Jie Tian
Show Abstract
As one of molecular imaging, bioluminescence tomography (BLT) aims to recover internal source from surface
measurement. Being an ill-posed inverse problem, BLT source reconstruction is usually converted to an optimization
problem through regularization. In this contribution, we build a bimodal hybrid imaging system consisting of BLT and
micro-CT, and then propose an improved source reconstruction method based on adjoint diffusion equations (ADEs).
Compared with conventional methods based on constrained minimization problem (CMP), ADEs-based method replaces
expensive iterative computation with solving a group of linear ADEs. Given surface flux density, internal source power
density and photon fluence rate can be efficiently determined in one step. Both numerical and physical experiments are
performed to evaluate the bimodal BLT/micro-CT imaging system and this novel reconstruction method. The relevant
results demonstrate the feasibility and potential of this source reconstruction method.
GPU-accelerated Monte-Carlo modeling for fluorescence propagation in turbid medium
Author(s):
Xi Yi;
Weiting Chen;
Linhui Wu;
Wenjuan Ma;
Wei Zhang;
Jiao Li;
Xin Wang;
Feng Gao
Show Abstract
In biomedical optics, the Monte Carlo (MC) simulation is widely recognized as a gold standard for its high accuracy and
versatility. However, in fluorescence regime, due to the requirement for tracing a huge number of the consecutive events
of an excitation photon migration, the excitation-to-emission convention and the resultant fluorescent photon migration
in tissue, the MC method is prohibitively time-consuming, especially when the tissue has an optically heterogeneous
structure. To overcome the difficulty, we present a parallel implementation of MC modeling for fluorescence propagation
in tissue, on the basis of the Graphics Processing Units (GPU) and the Compute Unified Device Architecture (CUDA)
platform. By rationalizing the distribution of blocks and threads a certain number of photon migration procedures can be
processed synchronously and efficiently, with the single-instruction-multiple-thread execution mode of GPU. We have
evaluated the implementation for both homogeneous and heterogeneous scenarios by comparing with the conventional
CPU implementations, and shown that the GPU method can obtain significant acceleration of about 20-30 times for
fluorescence modeling in tissue, indicating that the GPU-based fluorescence MC simulation can be a practically effective
tool for methodological investigations of tissue fluorescence spectroscopy and imaging.
A high-sensitive diffuse fluorescence tomography system with CT-analogous scanning mode
Author(s):
Xin Wang;
Jiao Li;
Xi Yi;
Linhui Wu;
Wenjuan Ma;
Wei Zhang;
Feng Gao
Show Abstract
Diffuse fluorescence tomography (DFT) provides spatial distributions of fluorescence parameters by measuring
fluorescence signals of probes or agents that are targeted to interior specific molecules or tissues. The potential
applications of DFT can be found in drug development and early tumor diagnosis. This work proposes a CT-analogous
mode of DFT, where the imaging chamber is impinged by collimated beam from a fiber-coupled laser diode and the
resultant fluorescence re-emissions on the opposite side, i.e., the so-called "projections", are collected by eight detection
fibers placed from 101.25º to 258.75º perspectives opposite to the incidence that are then successively filtered out into a
photon-counting channel for quantification. By rotating the imaging chamber or phantom at an angular, the system
acquires the "projections" of surface-emitted fluorescence under different perspectives as a CT system does. This ease of
acquiring a large data-set enables realization of high-quality imaging. Pilot experiments on phantoms with Cy5.5-target
embedded have validated the efficacy of the proposed method.
A CT-analogous method for high-resolution fluorescence molecular tomography
Author(s):
Jiao Li;
Feng Gao;
Qingzhen Zhu;
Fenghui Li;
Xin Wang;
Limin Zhang;
Huijuan Zhao
Show Abstract
In vivo biomedical imaging using near-infrared light must overcome the effects of highly light scattering, which limit the
spatial resolution and affect image quality. The high-resolution, sensitive and quantitative fluorescence imaging tool is an
urgent need for the applications in small-animal imaging and clinical cancer research. A CT-analogous method for
fluorescence molecular tomography (FMT) on small-animal-sized models is presented to improve the spatial resolution
of FMT to a limit of several millimeters, depending on the size of the tissue region to be imaged. The method combines
FMT physics with the filtered back-projection scheme for image reconstruction of the fan-beam computed tomography,
based on the early-photon detection of time-resolved optical signals, and is suitable for two-dimensional (2D) imaging of
small size biological models. By use of a normalized Born formulation for the inversion, the algorithm is validated using
full time-resolved simulated data for 2D phantom that are generated from a hybrid finite-element and
finite-time-difference photon diffusion modeling, and its superiority in the improvement of the spatial resolution is
demonstrated by imaging different target-to-background contrast ratios.
Time-domain diffuse fluorescence tomography using BEM forward solver
Author(s):
Linhui Wu;
Yiming Lu;
Wei Zhang;
Xi Yi;
Wenjuan Ma;
Jiao Li;
Xin Wang;
Huijuan Zhao;
Feng Gao
Show Abstract
Traditionally, volume based finite element method (FEM) or finite difference method (FDM) are applied to the forward
problem of the time-domain diffuse fluorescence tomography (DFT), this paper presents a new numerical method for
solving the problem: the boundary element method (BEM). Using BEM forward solver is explored as an alternative to
the FEM or FDM solution methodology for the elliptic equations used to model the generation and transport of
fluorescent light in highly scattering media. In contrast to the FEM or FDM, the boundary integral method requires only
representation of the surface meshes, thus requires many fewer nodes and elements than the FEM and FDM. By using
BEM forward solver for time-domain DFT, we can simultaneously reconstruct both fluorescent yield and lifetime images.
The results have demonstrated that the BEM is suitable for solving the forward problem of time-domain DFT.
A time domain noncontact fluorescence tomography system for breast cancer diagnosis
Author(s):
Hui Guo;
Wei Meng;
Tingting Wang;
Jiao Li;
Huijuan Zhao;
Feng Gao
Show Abstract
A time domain noncontact fluorescence tomography system and the corresponding reconstruction algorithm towards the
early diagnosis of breast cancer are developed. The time domain system based on the time-correlated single photon
counting technique is adopted to provide both the high sensitivity in detection and good capability in multi-parameter
reconstruction. Comparing to the conventional contact measurement mode, the noncontact system with light scanning
can provide more measurement data for improving the spatial resolution of the images. The performance and efficacy of
the system is evaluated with measurements on solid phantoms. For the phantom with single fluorescent target, the
fluorescence yield and lifetime were simultaneously reconstructed with good quality. For the phantom with two
fluorescent targets, the targets with the center-to-center separation of 20mm and the edge separation of 15mm can be
distinguished. Measurements also show that the reconstructed yields are linear to the concentration of the fluorescence
dye. The results demonstrated the potential of the system in the in vivo diagnosis of the early breast cancer.
Fluorescence guided diffusion optical tomography based on wavelet transform and singular value decomposition
Author(s):
Limin Zhang;
Wei Zhang;
Feng Gao;
Jiao Li;
Huijuan Zhao
Show Abstract
A novel method for optical breast imaging was presented based on fluorescence guided diffusion optical tomography
(DOT). In this paper, the time-domain fluorescence parameters (yield and lifetime) were reconstructed based on discrete
wavelet transform at first, then the fluorescence images were used to guide and constrain the diffusion optical
tomography reconstruction, and the image segmentation strategy based on wavelet coefficient was applied to improve
the image quality in DOT. To validate the proposed method, the numerical simulation was performed to demonstrate its
computational efficacy. The results showed the feasibility of this method, and the spatial resolution, quantification and
computational efficiency in fluorescence diffusion optical tomography and DOT were enhanced evidently.
Development of multimodal microscope combined with confocal imaging and two-photon imaging
Author(s):
Wanhee Chun;
Dukho Do;
Dae-Gab Gweon
Show Abstract
Multimodal microscope which obtains various images for the same interest area simultaneously plays an
important role in the process of comprehensive analysis for biological information. Confocal imaging for reflection and
fluorescence emission light and two-photon imaging dealing with nonlinear optical effect are operated in the unified
platform by sharing system configuration commonly used for those imaging. Reflection light, fluorescence light and
nonlinear optical signal from the same focal point are detected through separate channels and converted to respective
images. Common optical system is especially customized to satisfy their requirements considering wavelength band of
light used for imaging. Multimodal microscope is implemented and verified through multichannel images for bioexperiments.
Confocal reflection imaging for label-free specimen, confocal fluorescence imaging and two-photon
fluorescence imaging for specifically stained target are realized and make complementary analysis. The used light
signals, continuous wave light from NUV to NIR and pulsed light, is verified through imaging results of designed
multimodal microscope.
Examination of a demyelinated fiber by action-potential-encoded second harmonic generation
Author(s):
Xin-guang Chen;
Zhi-hui Luo;
Hong-qin Yang;
Yi-mei Huang;
Shu-sen Xie
Show Abstract
Axonal demyelination is a common phenomenon in the nervous system in human. Conventional measured approaches
such as surface recording electrode and diffusion tensor imaging, are hard to fast and accurately determine the
demyelinated status of a fiber. In this study, we first presented a mathematical model of nerve fiber demyelination, and it
was combined with second harmonic generation(SHG) technique to study the characteristics of action-potential-encoded
SHG and analyze the sensitivity of SHG signals responded to membrane potential. And then, we used this approach to
fast examine the injured myelin sheaths resulted from demyelination. Each myelin sheath of a fiber was examined
simultaneously by this approach. The results showed that fiber demyelination led to observable attenuation of action
potential amplitude. The delay of action potential conduction would be markedly observed when the fiber demyelination
was more than 80%. Furthermore, the normal and injured myelin sheaths of a myelinated fiber could be distinguished via
the changes of SHG signals, which revealed the possibility of SHG technique in the examination of a demyelinated fiber.
Our study shows that this approach may have potential application values in clinic.