共查询到20条相似文献,搜索用时 15 毫秒
1.
Based on the generalized pulse spectrum technique that was previously developed for time-domain diffuse optical tomography, we propose a linear framework of time-domain fluorescence molecular tomography for simultaneous reconstruction of both the yield and lifetime of multi-fluorophores. The methodology is exemplified for mono-component case and validated with simulated data. 相似文献
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Alexander D. Klose Andreas H. Hielscher 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,72(5):715-732
Optical tomography is a novel imaging modality that is employed to reconstruct cross-sectional images of the optical properties of highly scattering media given measurements performed on the surface of the medium. Recent advances in this field have mainly been driven by biomedical applications in which near-infrared light is used for transillumination and reflectance measurements of highly scattering biological tissues. Many of the reconstruction algorithms currently utilized for optical tomography make use of model-based iterative image reconstruction (MOBIIR) schemes. The imaging problem is formulated as an optimization problem, in which an objective function is minimized. In the simplest case the objective function is a normalized-squared error between measured and predicted data. The predicted data are obtained by using a forward model that describes light propagation in the scattering medium given a certain distribution of optical properties.In part I of this two-part study, we presented a forward model that is based on the time-independent equation of radiative transfer. Using experimental data we showed that this transport-theory-based forward model can accurately predict light propagation in highly scattering media that contain void-like inclusions. In part II we focus on the details of our image reconstruction scheme (inverse model). A crucial component of this scheme involves the efficient and accurate determination of the gradient of the objective function with respect to all optical properties. This calculation is performed using an adjoint differentiation algorithm that allows for fast calculation of this gradient. Having calculated this gradient, we minimize the objective function with a gradient-based optimization method, which results in the reconstruction of the spatial distribution of scattering and absorption coefficients inside the medium. In addition to presenting the mathematical and numerical background of our code, we present reconstruction results based on experimentally obtained data from highly scattering media that contain void-like regions. These types of media play an important role in optical tomographic imaging of the human brain and joints. 相似文献
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We describe a new fluorescence imaging device for clinical cancer photodetection in hollow organs in which the tumor/normal
tissue contrast is derived from the fluorescence lifetime of endogenous or exogenous fluorochromes. This fluorescence lifetime
contrast gives information about the physicochemical properties of the environment which are different between normal and
certain diseased tissues. The excitation light from a CW laser is modulated in amplitude at a radio frequency by an electrooptical
modulator and delivered by an optical fiber through an endoscope to the hollow organ. The image of the tissue collected by
the endoscope is separated in two spectral windows, one being the backscattered excitation light and the other the fluorescence
of the fluorochrome. Each image is then focused on the photocathode of image intensifiers (II) whose optical gain is modulated
at the same frequency as the excitation intensity, resulting in homodyne phase-sensitive images. By acquiring stationary phase-sensitive
frames at different phases between the excitation and the detection, it is possible to calculate in quasi-real time the apparent
fluorescence lifetime of the corresponding tissue region for each pixel. A result obtained by investigating the endogenous
fluorochromes present in the mucous membrane of an excised human bladder is presented to illustrate this method and most of
the optical parameters which are of major importance for this photodetection modality have been evaluated. 相似文献
5.
Andr Müller Sebastian Marschall Ole Bjarlin Jensen Jrg Fricke Hans Wenzel Bernd Sumpf Peter E. Andersen 《Laser \u0026amp; Photonics Reviews》2013,7(5):605-627
Diode lasers are by far the most efficient lasers currently available. With the ever‐continuing improvement in diode laser technology, this type of laser has become increasingly attractive for a wide range of biomedical applications. Compared to the characteristics of competing laser systems, diode lasers simultaneously offer tunability, high‐power emission and compact size at fairly low cost. Therefore, diode lasers are increasingly preferred in important applications, such as photocoagulation, optical coherence tomography, diffuse optical imaging, fluorescence lifetime imaging, and terahertz imaging. This review provides an overview of the latest development of diode laser technology and systems and their use within selected biomedical applications. 670 nm external cavity diode laser for Raman spectroscopy built on a 13 × 4 mm2 microbench (Copyright FBH/Schurian.com ). 相似文献
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We present a full three-dimensional, featured-data algorithm for time-domain fluorescence diffuse optical tomography that inverts the Laplace-transformed time-domain coupled diffusion equations and employs a pair of appropriate transform-factors to effectively separate the fluorescent yield and lifetime parameters. By use of a time-correlation single-photon counting system and the normalized Born formulation, we ex-perimentally validate that the proposed scheme can achieve simultaneous reconstruction of the fluorescent yield and lifetime distributions with a reasonable accuracy. 相似文献
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John J. Birmingham 《Journal of fluorescence》1997,7(1):45-54
Fluorescence lifetime imaging methodology has been successfully implemented at Unilever Research in a frequency-domain manner.
The experimental rig constructed comprises a wide-bandwidth electrooptic modulator operating on a CW argon-ion laser. The
modulated excitation with a typical upper modulation frequency limit of 200 MHz falls on macroscopic samples and the resultant
scattered light or fluorescence emission is then imaged onto a custom gain-modulatable image intensifier and slow-scan CCD
camera combination. Phase adjustment of the image intensifier relative to the laser modulator is achieved by the RF function
generator driving the intensifier. Both homodyne and heterodyne (500-Hz) strobing modes are employed to generate a double
image stack (scattered light reference and fluorescence emission) comprising an image sequence as a function of instrumental
phase difference. These image stacks are analyzed by Fourier least-squares methods to yield lifetime images by both phase
delay and normalized demodulation. Correct operation of the apparatus is deduced from the direct imaging of a quencher-induced
lifetime variation of BODIPY disulfonate over a range of concentrations. A typical industrially relevant sample, comprising
an investigation of the lifetime aspects of human dental enamel autofluorescence at 50MHz modulation frequency, is given.
This shows that there are real emission lifetime decreases of about 0.5 nsec in white-spot lesion areas compared to the surrounding
sound enamel. 相似文献
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光源附近组织的空间分辨漫反射是近年来生物医学光子学领域的一个研究热点,其目的是发展一种能够测定活体生物组织光学参量的新技术。漫射近似理论研究光源附近组织的空间分辨漫反射具有很大局限性。P3近似理论考虑了相函数的三阶矩,能较准确地描述光源附近组织的光辐射分布。研究了基于P3近似的空间分辨漫反射,从输运理论的PN方程组出发,导出了P3近似方程组和P3近似的格林函数解;阐述了漫射近似与P1近似的关系,给出了外推边界条件下,准直光束近似后的P3近似漫反射率的完整表示,讨论了相函数二阶参量对P3近似漫反射的影响,并与漫射近似和蒙特卡罗模拟结果进行了比较,指出了P3近似的应用范围。 相似文献
10.
《Comptes Rendus de l''Academie des Sciences Series IV Physics》2001,2(8):1073-1089
Based on photon migration the new goal of diffuse optical imaging is to reveal optical contrasts in the depth of biological tissues. We discuss first the origin of contrast mechanism (absorption, fluorescence and scattering) used on diffuse optical imaging and spectroscopy. Then, various experimental approaches are described based on CW, pulsed and modulated light excitation and detection. Theoretical models which provide solutions for direct and inverse problems are presented using random walk theory. Finally two studies on breast imaging and on the use of fluorescence exogeneous markers are discussed in detail. 相似文献
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S. A. Lysenko 《Optics and Spectroscopy》2018,125(1):113-122
A method for correcting the influence of light attenuation processes in biological tissues on their fluorescent images is proposed. The transfer function that takes into account the radiation losses in the medium at the wavelengths of excitation and emission of fluorescence is calculated analytically, depending on the transport scattering index and the hemoglobin tissue index. The latter is determined on the basis of a color image of the tissue in reflected visible light. Verification of the developed method was carried out on the basis of computer simulation of fluorescent images of biological tissue by the Monte Carlo method. 相似文献
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离散坐标法在计算生物组织内光场空间角分布中的应用 总被引:5,自引:5,他引:0
从辐射传输理论出发,研究了准直光照下层状生物组织内漫射光场的角分布.在辐射传输方程的基础上,采用离散坐标法得到了描述层状生物组织内漫射光传输问题的微分方程组形式,并用特征值-特征矢量方法对其进行了求解,给出了通解形式.结合边界条件对两类典型生物组织内漫射光场角分布进行了数值计算-各向同性组织和前向散射组织,给出了组织内不同深度处漫射光场空间角分布曲线.通过对计算结果比较分析,得到了生物组织内漫射光场空间角分布随深度的变化规律,及边界效应和光学参量对组织内漫射光场空间角分布的影响. 相似文献
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The accuracy of diffuse optical tomography (DOT) highly depends on two important factors: first, the knowledge of the tissue optical heterogeneities for accurate modeling of light propagation, and second, the uniqueness of reconstructed values of optical properties. Previous studies illustrated that the inverse problem associated with steady-state DOT does not have unique solutions. In this study, we propose a simple method that can be applied to improve this challenging problem of steady-state DOT. In this method, we study the propagation of photons through compressed breast phantoms. The applied mechanical pressure can change the values of optical properties and this pressure dependence of optical properties as a set of constraint equations can be used to improve the inverse problem. The applied pressure can help us to restrict the distribution of possible values of depth and radius of defect inside breast phantom reconstructed by inverse problem. 相似文献
14.
Siegel J Elson DS Webb SE Parsons-Karavassilis D Lévêque-Fort S Cole MJ Lever MJ French PM Neil MA Juskaitis R Sucharov LO Wilson T 《Optics letters》2001,26(17):1338-1340
We report a novel whole-field three-dimensional fluorescence lifetime imaging microscope that incoporates multispectral imaging to provide five-dimensional (5-D) fluorescence microscopy. This instrument, which can acquire a 5-D data set in less than a minute, is based on potentially compact and inexpensive diode-pumped solid-state laser technology. We demonstrate that spectral discrimination as well as optical sectioning minimize artifacts in lifetime determination and illustrate how spectral discrimination improves the lifetime contrast of biological tissue. 相似文献
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《Current Applied Physics》2003,3(2-3):177-184
Development of optical biosensors is an active area of research in the field of medical technology. Sol–gel matrices made from alkoxide silicates, tetraethyl orthosilicate (TEOS) appear to be suitable glassy host matrix for the sensing system. However, the major problem in the TEOS based sol–gel matrices is stability. So it is important to study dopant–matrix interaction as a function of time. In the present study, we report fluorescence emission and excited state lifetime measurements on fluorescent probes entrapped in TEOS sol–gel for monitoring the physico-chemical processes for characterization and monitoring of local environment (pores) of dopant molecule (fluorescent probes) for construction of sensing layer for optical transducer. Different types of fluorescent probes viz., Hoechst 33258 (H258) and pyranine (PY) were used. Sol–gels containing these probes were prepared at pH=6.0 and the physical and spectroscopic parameters were monitored as a function of storage time (days). The emission intensity from entrapped H258 has shown relatively higher extent of decrease during aging. The excited state fluorescence lifetime measurements on these probes depicted single exponential decay component at 5.4 ns (PY) and 3.6 ns (H258) in fresh sol–gels. After a few days of storage the sol–gel containing H258 revealed an additional short decay component whereas no such alteration could be observed with the probe molecule PY. Further confirmation of multicomponents decay was obtained by distribution analysis of lifetime of H258 where an increase in width of mean lifetime was observed with storage whereas no such change was indicated from PY. Thus it appears that H258 is a better probe molecule for characterizing and monitoring local environment of pores in sol–gel. 相似文献
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Tanja Tarvainen Ville Kolehmainen Jari P. Kaipio 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(16):2600-2608
The coupled radiative transport-diffusion model can be used as light transport model in situations in which the diffusion equation is not a valid approximation everywhere in the domain. In the coupled model, light propagation is modelled with the radiative transport equation in sub-domains in which the approximations of the diffusion equation are not valid, such as within low-scattering regions, and the diffusion approximation is used elsewhere in the domain. In this paper, an image reconstruction method for diffuse optical tomography based on using the coupled radiative transport-diffusion model is developed. In the approach, absorption and scattering distributions are estimated by minimising a regularised least-squares error between the measured data and solution of the coupled model. The approach is tested with simulations. Reconstructions from different cases including domains with low-scattering regions are shown. The results show that the coupled radiative transport-diffusion model can be utilised in image reconstruction problem of diffuse optical tomography and that it produces as good quality reconstructions as the full radiative transport equation also in the presence of low-scattering regions. 相似文献
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Dynamic fluorescence diffuse optical tomography (FDOT) is important in drug deliver research. In this letter, we first image the metabolic processes of micelles indocyanine green throughout the whole body of a nude mouse using the full-angle FDOT system with line illumination (L-FDOT). The resolution of L-FDOT is evaluated using phantom experiment. Next, in vivo dynamic tomographic images (100 frames; approximately 170 min) of mouse liver and abdomen are shown and cross-validated by planar fluorescence reflectance imaging in vitro. Results provide evidence on applicability of the tomographic image wholebody biological activities in vivo on minute timescale (approximately 1.7 min) using L-FDOT. 相似文献
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紫外灯下,化石树脂常见荧光现象,但其磷光现象仍有待表征与研究.将印度尼西亚产出的类似多米尼加蓝珀的化石树脂分为白色包体(PartⅠ)、暗色包体(PartⅡ)和基底(PartⅢ)三个部分,使用红外光谱确定其植物来源,借助三维荧光光谱仪表征化石树脂的光致发光现象(包括荧光和磷光),并探讨印尼化石树脂发光现象随地质过程变化的... 相似文献
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We demonstrate inhibition of the sidelobes of the axial point spread function in optical coherence tomography by shaping the power spectrum of the light source with a remaining power of 4.54 mW. A broadband amplified spontaneous emission source radiating at 1565 +/- 40 nm is employed in a free-space optical coherence tomography system. The axial point spread functions before and after optical spectral shaping are presented. Results show that spectral shaping of the source can inhibit sidelobes of the point spread function up to 12.9 dB, with an associated small increase of 2.2 dB in noise floor in the far field. The effect of spectral shaping on axial resolution is demonstrated according to three metrics. Image quality improvement is also illustrated with optical coherence tomography images of an onion before and after spectral shaping. 相似文献
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Spectral properties of erbium-doped heavy metal oxyfluoride silicate glasses for broadband amplification 总被引:1,自引:0,他引:1 下载免费PDF全文
Erbium-doped glasses showing a wide 1.55μm emission band are reported in a novel heavy metal oxyfluoride glass system SiO_2-PbO-PbF_2 and their optical properties such as emission spectra, fluorescence lifetime and the refractive index have been investigated. The broad and flat {}^4I_{13/2}→{}^4I_{15/2} emission of Er^{3+} ions around 1.55μm can be used as host materials for potential optical amplifiers in wavelength-division-multiplexing network system. We find that with increasing PbF_2 content in the glass composition, the fluorescence full width at half maximum and fluorescence lifetime of the {}^4I_{13/2} level of Er^{3+} increase, while refractive index and density decrease. 相似文献