The Experts below are selected from a list of 207 Experts worldwide ranked by ideXlab platform

Andreas H. Hielscher - One of the best experts on this subject based on the ideXlab platform.

  • pde constrained fluorescence tomography with the frequency Domain Equation of radiative transfer
    IEEE Journal of Selected Topics in Quantum Electronics, 2010
    Co-Authors: Andreas H. Hielscher
    Abstract:

    We present the first fluorescence tomography algorithm that is based on a partial differential Equation (PDE) constrained approach. PDE methods have been increasingly employed in many numerical applications, as they often lead to faster and more robust solutions of many inverse problems. In particular, we use a sequential quadratic programming (SQP) method, which allows solving the two forward problems in fluorescence tomography (one for the excitation and one for the emission radiances) and one inverse problem (for recovering the spatial distribution of the fluorescent sources) simultaneously by updating both forward and inverse variables in simultaneously at each of iteration of the optimization process. We evaluate the performance of this approach with numerical and experimental data using a transport-theory frequency-Domain algorithm as forward model for light propagation in tissue. The results show that the PDE-constrained approach is computationally stable and accelerates the image reconstruction process up to a factor of 15 when compared to commonly employed unconstrained methods.

  • Modeling Fluorescence Light Propagation in Arbitrarily Shaped Domains with the Equation of Radiative Transfer on Block-Structured Grids
    Biomedical Optics and 3-D Imaging, 2010
    Co-Authors: Ludguier D. Montejo, Alexander D. Klose, Andreas H. Hielscher
    Abstract:

    We solve the frequency Domain Equation of radiative transfer on block-structured grids (BSG) that are adaptively refined only near boundaries. We compare solutions on BSG to solutions on single finely discretized grids.

  • A parallel reduced-space sequential-quadratic programming algorithm for frequency-Domain small animal optical tomography
    Optical Tomography and Spectroscopy of Tissue VIII, 2009
    Co-Authors: Hyun Keol Kim, James M. Masciotti, Andreas H. Hielscher
    Abstract:

    Computational speed and available memory size on a single processor are two limiting factors when using the frequency-Domain Equation of radiative transport (FD-ERT) as a forward and inverse model to reconstruct three-dimensional (3D) tomographic images. In this work, we report on a parallel, multiprocessor reducedspace sequential quadratic programming (RSQP) approach to improve computational speed and reduce memory requirement. To evaluate and quantify the performance of the code, we performed simulation studies employing a 3D numerical mouse model. Furthermore, we tested the algorithm with experimental data obtained from tumor bearing mice.

  • a pde constrained sqp algorithm for optical tomography based on the frequency Domain Equation of radiative transfer
    Inverse Problems, 2009
    Co-Authors: Andreas H. Hielscher
    Abstract:

    It is well acknowledged that transport-theory-based reconstruction algorithm can provide the most accurate reconstruction results especially when small tissue volumes or high absorbing media are considered. However, these codes have a high computational burden and are often only slowly converging. Therefore, methods that accelerate the computation are highly desirable. To this end, we introduce in this work a partial-differential-Equation (PDE) constrained approach to optical tomography that makes use of an all-at-once reduced Hessian sequential quadratic programming (rSQP) scheme. The proposed scheme treats the forward and inverse variables independently, which makes it possible to update the radiation intensities and the optical coefficients simultaneously by solving the forward and inverse problems, all at once. We evaluate the performance of the proposed scheme with numerical and experimental data, and find that the rSQP scheme can reduce the computation time by a factor of 10–25, as compared to the commonly employed limited memory BFGS method. At the same time accuracy and robustness even in the presence of noise are not compromised.

  • Fluorescence Tomography with the Frequency Domain Equation of Radiative Transfer
    Biomedical Optics, 2008
    Co-Authors: Alexander D. Klose, Hyun K. Kim, Andreas H. Hielscher
    Abstract:

    We have developed an image reconstruction algorithm for fluorescence tomography based on the frequency Domain Equation of radiative transfer. Transport properties of tissue become significant when strong light absorption is encountered in small animal tissue.

Liming Ruan - One of the best experts on this subject based on the ideXlab platform.

  • application of sqp algorithm for fluorescence tomography with the time Domain Equation of radiative transfer
    Journal of Quantitative Spectroscopy & Radiative Transfer, 2017
    Co-Authors: Yaobin Qiao, Hong Qi, Liming Ruan
    Abstract:

    Abstract A reconstruction scheme for the fluorescence tomography is investigated based on the time-Domain radiative transfer Equation (TD-RTE). Two coupled TD-RTEs, which can provide considerable measurement data, are used as the forward model and solved by the discrete ordinate method. The sequential quadratic programming (SQP) is employed to build the reconstruction scheme for solving the inverse problem. The gradient of objective function is calculated efficiently by the adjoint Equation technique. Considering the ill-posed nature of the inverse problem, the regularization term based on the generalized Gaussian Markov random field (GGMRF) model is adopted to enhance the reconstructed image. Influence of the initial guess, contrast, noisy data, and shape of the fluorescent target are analyzed. Simulated results show that the proposed algorithm performs efficiently and accurately on reconstructing the distribution of the fluorescence yield.

  • Application of SQP algorithm for fluorescence tomography with the time-Domain Equation of radiative transfer
    Journal of Quantitative Spectroscopy and Radiative Transfer, 2017
    Co-Authors: Yaobin Qiao, Ya-tao Ren, Jian-ping Sun, Liming Ruan
    Abstract:

    Abstract A reconstruction scheme for the fluorescence tomography is investigated based on the time-Domain radiative transfer Equation (TD-RTE). Two coupled TD-RTEs, which can provide considerable measurement data, are used as the forward model and solved by the discrete ordinate method. The sequential quadratic programming (SQP) is employed to build the reconstruction scheme for solving the inverse problem. The gradient of objective function is calculated efficiently by the adjoint Equation technique. Considering the ill-posed nature of the inverse problem, the regularization term based on the generalized Gaussian Markov random field (GGMRF) model is adopted to enhance the reconstructed image. Influence of the initial guess, contrast, noisy data, and shape of the fluorescent target are analyzed. Simulated results show that the proposed algorithm performs efficiently and accurately on reconstructing the distribution of the fluorescence yield.

Yaobin Qiao - One of the best experts on this subject based on the ideXlab platform.

  • application of sqp algorithm for fluorescence tomography with the time Domain Equation of radiative transfer
    Journal of Quantitative Spectroscopy & Radiative Transfer, 2017
    Co-Authors: Yaobin Qiao, Hong Qi, Liming Ruan
    Abstract:

    Abstract A reconstruction scheme for the fluorescence tomography is investigated based on the time-Domain radiative transfer Equation (TD-RTE). Two coupled TD-RTEs, which can provide considerable measurement data, are used as the forward model and solved by the discrete ordinate method. The sequential quadratic programming (SQP) is employed to build the reconstruction scheme for solving the inverse problem. The gradient of objective function is calculated efficiently by the adjoint Equation technique. Considering the ill-posed nature of the inverse problem, the regularization term based on the generalized Gaussian Markov random field (GGMRF) model is adopted to enhance the reconstructed image. Influence of the initial guess, contrast, noisy data, and shape of the fluorescent target are analyzed. Simulated results show that the proposed algorithm performs efficiently and accurately on reconstructing the distribution of the fluorescence yield.

  • Application of SQP algorithm for fluorescence tomography with the time-Domain Equation of radiative transfer
    Journal of Quantitative Spectroscopy and Radiative Transfer, 2017
    Co-Authors: Yaobin Qiao, Ya-tao Ren, Jian-ping Sun, Liming Ruan
    Abstract:

    Abstract A reconstruction scheme for the fluorescence tomography is investigated based on the time-Domain radiative transfer Equation (TD-RTE). Two coupled TD-RTEs, which can provide considerable measurement data, are used as the forward model and solved by the discrete ordinate method. The sequential quadratic programming (SQP) is employed to build the reconstruction scheme for solving the inverse problem. The gradient of objective function is calculated efficiently by the adjoint Equation technique. Considering the ill-posed nature of the inverse problem, the regularization term based on the generalized Gaussian Markov random field (GGMRF) model is adopted to enhance the reconstructed image. Influence of the initial guess, contrast, noisy data, and shape of the fluorescent target are analyzed. Simulated results show that the proposed algorithm performs efficiently and accurately on reconstructing the distribution of the fluorescence yield.

Hyun K. Kim - One of the best experts on this subject based on the ideXlab platform.

  • Fluorescence Tomography with the Frequency Domain Equation of Radiative Transfer
    Biomedical Optics, 2008
    Co-Authors: Alexander D. Klose, Hyun K. Kim, Andreas H. Hielscher
    Abstract:

    We have developed an image reconstruction algorithm for fluorescence tomography based on the frequency Domain Equation of radiative transfer. Transport properties of tissue become significant when strong light absorption is encountered in small animal tissue.

  • a sensitivity function based conjugate gradient method for optical tomography with the frequency Domain Equation of radiative transfer
    Journal of Quantitative Spectroscopy & Radiative Transfer, 2007
    Co-Authors: Hyun K. Kim, Andre Charette
    Abstract:

    The Sensitivity Function-based Conjugate Gradient Method (SFCGM) is described. This method is used to solve the inverse problems of function estimation, such as the local maps of absorption and scattering coefficients, as applied to optical tomography for biomedical imaging. A highly scattering, absorbing, non-reflecting, non-emitting medium is considered here and simultaneous reconstructions of absorption and scattering coefficients inside the test medium are achieved with the proposed optimization technique, by using the exit intensity measured at boundary surfaces. The forward problem is solved with a discrete-ordinates finite-difference method on the framework of the frequency-Domain full Equation of radiative transfer. The modulation frequency is set to 600 MHz and the frequency data, obtained with the source modulation, is used as the input data. The inversion results demonstrate that the SFCGM can retrieve simultaneously the spatial distributions of optical properties inside the medium within a reasonable accuracy, by significantly reducing a cross-talk between inter-parameters. It is also observed that the closer-to-detector objects are better retrieved.

Verne L. Jacobs - One of the best experts on this subject based on the ideXlab platform.

  • Classical, semi-classical, and quantized-field descriptions of light propagation in general non-local and non-stationary dispersive and absorbing media
    Proceedings of SPIE, 2016
    Co-Authors: Verne L. Jacobs
    Abstract:

    Classical, semi-classical, and quantum-field descriptions for the interaction of light with matter are systematically discussed. Applications of interest include precise determinations of the linear and the non-linear electromagnetic response relevant to resonant pump-probe optical phenomena, such as electromagnetically induced transparency. In the quantum-mechanical description of matter systems, we introduce a general reduced-density-matrix framework. Time-Domain (Equation-of-motion) and frequency-Domain (resolvent-operator) formulations are developed in a unified and self-consistent manner, using a Liouville-space operator representation. A preliminary semi-classical perturbation treatment of the electromagnetic interaction is adopted, in which the electromagnetic field is described as a classical field satisfying the Maxwell Equations. Compact Liouville-space operator expressions are derived for the linear and the general (nth order) non-linear electromagnetic-response tensors describing moving many-electron systems. The tetradic matrix elements of the Liouville-space self-energy operators, which are introduced in the time-Domain and frequency-Domain formulations, are evaluated for environmental collisional and radiative interactions, in order to provide explicit forms for the quantum kinetic Equations and the spectral-line shape formulas. It is emphasized that a quantized-field approach is essential for a fully self-consistent quantum-mechanical description of the interacting light-matter system.

  • Liouville-space descriptions for intense-field coherent electromagnetic interactions
    Advanced Optical and Quantum Memories and Computing III, 2006
    Co-Authors: Verne L. Jacobs, Zachary Dutton, Mark Bashkansky, Michael Steiner, John F. Reintjes
    Abstract:

    Liouville-space (reduced-density-operator) descriptions are developed for resonant and coherent electromagnetic interactions of quantized electronic systems, taking into account environmental decoherence and relaxation phenomena. Applications of interest include electromagnetically-induced transparency and related pump-probe optical phenomena in many-electron atomic systems (in electron-ion beam interactions, gases, and high-temperature plasmas) and semiconductor materials (bulk crystals and nanostructures). Time-Domain (Equation-of-motion) and frequency-Domain (resolvent-operator) formulations are developed in a unified manner. The standard Born (lowest-order perturbationtheory) and Markov (short-memory-time) approximations are systematically introduced within the framework of the general non-perturbative and non-Markovian formulations. A preliminary semiclassical description of the entire electromagnetic interaction is introduced. Compact Liouville-space operator expressions are derived for the linear and the general (n'th order) non-linear electromagnetic-response tensors occurring in a perturbation-theory treatment of the semiclassical electromagnetic interaction. These expressions can be evaluated for coherent initial electronic excitations and for the full tetradic-matrix form of the Liouville-space self-energy operator representing the environmental interactions in the Markov approximation. Intense-field electromagnetic interactions are treated by means of an alternative, non-perturbative method, which is based on a Liouville-space Floquet-Fourier representation of the reduced density operator. Electron-electron quantum correlations are treated by the introduction of a cluster decomposition of the reduced density operator and a coupled hierarchy of reduced-density-operator Equations.

  • Kinetic and spectral descriptions of polarized atomic radiative emission from plasmas
    Journal of Quantitative Spectroscopy and Radiative Transfer, 2006
    Co-Authors: Verne L. Jacobs
    Abstract:

    Abstract A reduced-density-matrix description has been developed for the investigation of polarized radiative emission during single-photon transitions from bound and autoionizing states of ionized atomic systems in the presence of a general arrangement of static (or quasi-static) electric and magnetic fields. Particular emphasis has been given to excitation of the atomic states by electrons with an anisotropic velocity distribution, which can be produced in an electron–ion beam experiment or in a non-equilibrium plasma environment. It is desirable to consider the coherent excitation of a particular subspace of the atomic bound or autoionizing states, which can occur as a result of sufficiently intense electromagnetic interactions. A general expression for the matrix elements of the detected-photon density operator provides a unified framework for the analysis of the spectral intensity, angular distribution, and polarization of the Stark–Zeeman patterns. From a unified development of time-Domain (Equation-of-motion) and frequency-Domain (resolvent-operator) formulations of the reduced-density-matrix approach, the non-equilibrium atomic-state kinetics and the homogeneous spectral-line shapes are self-consistently described.