Algebraic reconstruction techniques for spectral reconstruction in diffuse optical tomography
Brendel, Bernhard; Ziegler, Ronny; Nielsen, Tim
2008-12-01
Reconstruction in diffuse optical tomography (DOT) necessitates solving the diffusion equation, which is nonlinear with respect to the parameters that have to be reconstructed. Currently applied solving methods are based on the linearization of the equation. For spectral three-dimensional reconstruction, the emerging equation system is too large for direct inversion, but the application of iterative methods is feasible. Computational effort and speed of convergence of these iterative methods are crucial since they determine the computation time of the reconstruction. In this paper, the iterative methods algebraic reconstruction technique (ART) and conjugated gradients (CGs) as well as a new modified ART method are investigated for spectral DOT reconstruction. The aim of the modified ART scheme is to speed up the convergence by considering the specific conditions of spectral reconstruction. As a result, it converges much faster to favorable results than conventional ART and CG methods.
The Algebraic Reconstruction Technique(ART)
NASA Astrophysics Data System (ADS)
Raparia, D.; Alessi, J.; Kponou, A.
1997-05-01
Projections of charged particle beam current density are used as a measure of beam position and size. In conventional practice only two projections, usually horizontal and vertical, are measured. This puts a severe limit on the of detail of information that can be achieved. A third projection provides a significant improvement. The Algebrabic Reconstruction Technique (ART) (R. Gordon, et at) ``Three-Dimensional Reconstruction from Projections: A Review of Algorithms'', Iternational Review of Cytology, Vol. 38, pp 111 (1974) uses three or more projections to reconstruct the 2-dimensional density profiles. We have used this technique to measure beam density and it has proved very helpful, especially in measuring coupling in x-y phase space. We will present examples of measurements of current densities using this technique.
Effective regularized algebraic reconstruction technique for computed tomography
Prun, V. E.; Nikolaev, D. P.; Buzmakov, A. V.; Chukalina, M. V.; Asadchikov, V. E.
2013-12-15
A new fast version of the reconstruction algorithm for computed tomography based on the simultaneous algebraic reconstruction technique (SART) is proposed. The algorithm iteration is asymptotically accelerated using the fast Hough transform from O(n{sup 3}) to O(n{sup 2}logn). Similarly to the algebraic reconstruction technique (RegART), which was proposed by us previously, the regularization operator is applied after each iteration. A bilateral filter plays the role of this operator. The algorithm behavior is investigated using the model experiment.
Simultaneous algebraic reconstruction technique based on guided image filtering.
Ji, Dongjiang; Qu, Gangrong; Liu, Baodong
2016-07-11
The challenge of computed tomography is to reconstruct high-quality images from few-view projections. Using a prior guidance image, guided image filtering smoothes images while preserving edge features. The prior guidance image can be incorporated into the image reconstruction process to improve image quality. We propose a new simultaneous algebraic reconstruction technique based on guided image filtering. Specifically, the prior guidance image is updated in the image reconstruction process, merging information iteratively. To validate the algorithm practicality and efficiency, experiments were performed with numerical phantom projection data and real projection data. The results demonstrate that the proposed method is effective and efficient for nondestructive testing and rock mechanics. PMID:27410859
Tropospheric wet refractivity tomography using multiplicative algebraic reconstruction technique
NASA Astrophysics Data System (ADS)
Xiaoying, Wang; Ziqiang, Dai; Enhong, Zhang; Fuyang, K. E.; Yunchang, Cao; Lianchun, Song
2014-01-01
Algebraic reconstruction techniques (ART) have been successfully used to reconstruct the total electron content (TEC) of the ionosphere and in recent years be tentatively used in tropospheric wet refractivity and water vapor tomography in the ground-based GNSS technology. The previous research on ART used in tropospheric water vapor tomography focused on the convergence and relaxation parameters for various algebraic reconstruction techniques and rarely discussed the impact of Gaussian constraints and initial field on the iteration results. The existing accuracy evaluation parameters calculated from slant wet delay can only evaluate the resultant precision of the voxels penetrated by slant paths and cannot evaluate that of the voxels not penetrated by any slant path. The paper proposes two new statistical parameters Bias and RMS, calculated from wet refractivity of the total voxels, to improve the deficiencies of existing evaluation parameters and then discusses the effect of the Gaussian constraints and initial field on the convergence and tomography results in multiplicative algebraic reconstruction technique (MART) to reconstruct the 4D tropospheric wet refractivity field using simulation method.
Continuous analog of multiplicative algebraic reconstruction technique for computed tomography
NASA Astrophysics Data System (ADS)
Tateishi, Kiyoko; Yamaguchi, Yusaku; Abou Al-Ola, Omar M.; Kojima, Takeshi; Yoshinaga, Tetsuya
2016-03-01
We propose a hybrid dynamical system as a continuous analog to the block-iterative multiplicative algebraic reconstruction technique (BI-MART), which is a well-known iterative image reconstruction algorithm for computed tomography. The hybrid system is described by a switched nonlinear system with a piecewise smooth vector field or differential equation and, for consistent inverse problems, the convergence of non-negatively constrained solutions to a globally stable equilibrium is guaranteed by the Lyapunov theorem. Namely, we can prove theoretically that a weighted Kullback-Leibler divergence measure can be a common Lyapunov function for the switched system. We show that discretizing the differential equation by using the first-order approximation (Euler's method) based on the geometric multiplicative calculus leads to the same iterative formula of the BI-MART with the scaling parameter as a time-step of numerical discretization. The present paper is the first to reveal that a kind of iterative image reconstruction algorithm is constructed by the discretization of a continuous-time dynamical system for solving tomographic inverse problems. Iterative algorithms with not only the Euler method but also the Runge-Kutta methods of lower-orders applied for discretizing the continuous-time system can be used for image reconstruction. A numerical example showing the characteristics of the discretized iterative methods is presented.
Peng, Jiaju; Zhao, Jun
2011-07-01
To reduce the motion artifacts, a new scanning configuration is proposed for tomosynthesis in dynamic reconstruction. In this new configuration, multiple x-ray sources are uniformly distributed on the circular scanning trajectory and moving simultaneously. Numerical experiments are performed using two dynamic digital phantoms and algebraic reconstruction technique. The reconstruction images of single-source tomosynthesis and multi-source tomosynthesis are compared and evaluated. The results show that multi-source tomosynthesis could reduce artifacts effectively, thus improving image quality. The advantages of multi-source tomosynthesis in dynamic reconstruction are important to cardiac imaging and respiratory imaging. PMID:22097745
Li, Shu; Chan, Cheong; Stockmann, Jason P.; Tagare, Hemant; Adluru, Ganesh; Tam, Leo K.; Galiana, Gigi; Constable, R. Todd; Kozerke, Sebastian; Peters, Dana C.
2014-01-01
Purpose To investigate algebraic reconstruction technique (ART) for parallel imaging reconstruction of radial data, applied to accelerated cardiac cine. Methods A GPU-accelerated ART reconstruction was implemented and applied to simulations, point spread functions (PSF) and in twelve subjects imaged with radial cardiac cine acquisitions. Cine images were reconstructed with radial ART at multiple undersampling levels (192 Nr x Np = 96 to 16). Images were qualitatively and quantitatively analyzed for sharpness and artifacts, and compared to filtered back-projection (FBP), and conjugate gradient SENSE (CG SENSE). Results Radial ART provided reduced artifacts and mainly preserved spatial resolution, for both simulations and in vivo data. Artifacts were qualitatively and quantitatively less with ART than FBP using 48, 32, and 24 Np, although FBP provided quantitatively sharper images at undersampling levels of 48-24 Np (all p<0.05). Use of undersampled radial data for generating auto-calibrated coil-sensitivity profiles resulted in slightly reduced quality. ART was comparable to CG SENSE. GPU-acceleration increased ART reconstruction speed 15-fold, with little impact on the images. Conclusion GPU-accelerated ART is an alternative approach to image reconstruction for parallel radial MR imaging, providing reduced artifacts while mainly maintaining sharpness compared to FBP, as shown by its first application in cardiac studies. PMID:24753213
Myers, K.J. . Center for Devices and Radiological Health); Hanson, K.M. )
1990-01-01
A method for comparing reconstruction algorithms is presented based on the ability to perform certain detection tasks on the resulting images. The reconstruction algorithms compared are the algebraic reconstruction technique and the maximum entropy reconstruction method. Task performance is assessed through a Monte Carlo simulation of the complete imaging process, including the generation of a set of object scenes, followed by data-taking, reconstruction, and performance of the specified task by a machine observer. For these detection tasks the figure of merit used for comparison is the detectability index. When each algorithm is run with approximately optimized parameters, these studies find comparable values for the detectability index. 19 refs., 6 figs., 2 tabs.
NASA Astrophysics Data System (ADS)
Wen, Debao; Liu, Sanzhi
2010-08-01
For the limitation of the conventional multiplicative algebraic reconstruction technique (MART), a constrained MART (CMART) is proposed in this paper. In the new tomographic algorithm, a popular two-dimensional multi-point finite difference approximation of the second order Laplacian operator is used to smooth the electron density field. The feasibility and superiority of the new method are demonstrated by using the numerical simulation experiment. Finally, the CMART is used to reconstruct the regional electron density field by using the actual GNSS data under geomagnetic quiet and disturbed days. The available ionosonde data from Beijing station further validates the superiority of the new method.
Development of a GNSS water vapour tomography system using algebraic reconstruction techniques
NASA Astrophysics Data System (ADS)
Bender, Michael; Dick, Galina; Ge, Maorong; Deng, Zhiguo; Wickert, Jens; Kahle, Hans-Gert; Raabe, Armin; Tetzlaff, Gerd
2011-05-01
A GNSS water vapour tomography system developed to reconstruct spatially resolved humidity fields in the troposphere is described. The tomography system was designed to process the slant path delays of about 270 German GNSS stations in near real-time with a temporal resolution of 30 min, a horizontal resolution of 40 km and a vertical resolution of 500 m or better. After a short introduction to the GPS slant delay processing the framework of the GNSS tomography is described in detail. Different implementations of the iterative algebraic reconstruction techniques (ART) used to invert the linear inverse problem are discussed. It was found that the multiplicative techniques (MART) provide the best results with least processing time, i.e., a tomographic reconstruction of about 26,000 slant delays on a 8280 cell grid can be obtained in less than 10 min. Different iterative reconstruction techniques are compared with respect to their convergence behaviour and some numerical parameters. The inversion can be considerably stabilized by using additional non-GNSS observations and implementing various constraints. Different strategies for initialising the tomography and utilizing extra information are discussed. At last an example of a reconstructed field of the wet refractivity is presented and compared to the corresponding distribution of the integrated water vapour, an analysis of a numerical weather model (COSMO-DE) and some radiosonde profiles.
Shih, Cheng-Ting; Chang, Yuan-Jen; Hsu, Jui-Ting; Chuang, Keh-Shih; Chang, Shu-Jun; Wu, Jay
2015-12-01
Optical computed tomography (optical CT) has been proven to be a useful tool for dose readouts of polymer gel dosimeters. In this study, the algebraic reconstruction technique (ART) for image reconstruction of gel dosimeters was used to improve the image quality of optical CT. Cylindrical phantoms filled with N-isopropyl-acrylamide polymer gels were irradiated using a medical linear accelerator. A circular dose distribution and a hexagonal dose distribution were produced by applying the VMAT technique and the six-field dose delivery, respectively. The phantoms were scanned using optical CT, and the images were reconstructed using the filtered back-projection (FBP) algorithm and the ART. For the circular dose distribution, the ART successfully reduced the ring artifacts and noise in the reconstructed image. For the hexagonal dose distribution, the ART reduced the hot spots at the entrances of the beams and increased the dose uniformity in the central region. Within 50% isodose line, the gamma pass rates for the 2 mm/3% criteria for the ART and FBP were 99.2% and 88.1%, respectively. The ART could be used for the reconstruction of optical CT images to improve image quality and provide accurate dose conversion for polymer gel dosimeters. PMID:26165178
Levakhina, Y. M.; Mueller, J.; Buzug, T. M.; Duschka, R. L.; Vogt, F.; Barkhausen, J.
2013-03-15
Purpose: This paper introduces a nonlinear weighting scheme into the backprojection operation within the simultaneous algebraic reconstruction technique (SART). It is designed for tomosynthesis imaging of objects with high-attenuation features in order to reduce limited angle artifacts. Methods: The algorithm estimates which projections potentially produce artifacts in a voxel. The contribution of those projections into the updating term is reduced. In order to identify those projections automatically, a four-dimensional backprojected space representation is used. Weighting coefficients are calculated based on a dissimilarity measure, evaluated in this space. For each combination of an angular view direction and a voxel position an individual weighting coefficient for the updating term is calculated. Results: The feasibility of the proposed approach is shown based on reconstructions of the following real three-dimensional tomosynthesis datasets: a mammography quality phantom, an apple with metal needles, a dried finger bone in water, and a human hand. Datasets have been acquired with a Siemens Mammomat Inspiration tomosynthesis device and reconstructed using SART with and without suggested weighting. Out-of-focus artifacts are described using line profiles and measured using standard deviation (STD) in the plane and below the plane which contains artifact-causing features. Artifacts distribution in axial direction is measured using an artifact spread function (ASF). The volumes reconstructed with the weighting scheme demonstrate the reduction of out-of-focus artifacts, lower STD (meaning reduction of artifacts), and narrower ASF compared to nonweighted SART reconstruction. It is achieved successfully for different kinds of structures: point-like structures such as phantom features, long structures such as metal needles, and fine structures such as trabecular bone structures. Conclusions: Results indicate the feasibility of the proposed algorithm to reduce typical
NASA Astrophysics Data System (ADS)
Bilski, B. J.; Jozwicka, A.; Kujawinska, M.
2007-09-01
Constant development of microelements' technology requires a creation of new instruments to determine their basic physical parameters in 3D. The most efficient non-destructive method providing 3D information is tomography. In this paper we present Digital Holographic Tomography (DHT), in which input data is provided by means of Di-git- al Holography (DH). The main advantage of DH is the capability to capture several projections with a single hologram [1]. However, these projections have uneven angular distribution and their number is significantly limited. Therefore - Algebraic Reconstruction Technique (ART), where a few phase projections may be sufficient for proper 3D phase reconstruction, is implemented. The error analysis of the method and its additional limitations due to shape and dimensions of investigated object are presented. Finally, the results of ART application to DHT method are also presented on data reconstructed from numerically generated hologram of a multimode fibre.
NASA Astrophysics Data System (ADS)
Hui-Hui, Xia; Rui-Feng, Kan; Jian-Guo, Liu; Zhen-Yu, Xu; Ya-Bai, He
2016-06-01
An improved algebraic reconstruction technique (ART) combined with tunable diode laser absorption spectroscopy(TDLAS) is presented in this paper for determining two-dimensional (2D) distribution of H2O concentration and temperature in a simulated combustion flame. This work aims to simulate the reconstruction of spectroscopic measurements by a multi-view parallel-beam scanning geometry and analyze the effects of projection rays on reconstruction accuracy. It finally proves that reconstruction quality dramatically increases with the number of projection rays increasing until more than 180 for 20 × 20 grid, and after that point, the number of projection rays has little influence on reconstruction accuracy. It is clear that the temperature reconstruction results are more accurate than the water vapor concentration obtained by the traditional concentration calculation method. In the present study an innovative way to reduce the error of concentration reconstruction and improve the reconstruction quality greatly is also proposed, and the capability of this new method is evaluated by using appropriate assessment parameters. By using this new approach, not only the concentration reconstruction accuracy is greatly improved, but also a suitable parallel-beam arrangement is put forward for high reconstruction accuracy and simplicity of experimental validation. Finally, a bimodal structure of the combustion region is assumed to demonstrate the robustness and universality of the proposed method. Numerical investigation indicates that the proposed TDLAS tomographic algorithm is capable of detecting accurate temperature and concentration profiles. This feasible formula for reconstruction research is expected to resolve several key issues in practical combustion devices. Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 61205151), the National Key Scientific Instrument and Equipment Development Project of China (Grant
Blob-enhanced reconstruction technique
NASA Astrophysics Data System (ADS)
Castrillo, Giusy; Cafiero, Gioacchino; Discetti, Stefano; Astarita, Tommaso
2016-09-01
A method to enhance the quality of the tomographic reconstruction and, consequently, the 3D velocity measurement accuracy, is presented. The technique is based on integrating information on the objects to be reconstructed within the algebraic reconstruction process. A first guess intensity distribution is produced with a standard algebraic method, then the distribution is rebuilt as a sum of Gaussian blobs, based on location, intensity and size of agglomerates of light intensity surrounding local maxima. The blobs substitution regularizes the particle shape allowing a reduction of the particles discretization errors and of their elongation in the depth direction. The performances of the blob-enhanced reconstruction technique (BERT) are assessed with a 3D synthetic experiment. The results have been compared with those obtained by applying the standard camera simultaneous multiplicative reconstruction technique (CSMART) to the same volume. Several blob-enhanced reconstruction processes, both substituting the blobs at the end of the CSMART algorithm and during the iterations (i.e. using the blob-enhanced reconstruction as predictor for the following iterations), have been tested. The results confirm the enhancement in the velocity measurements accuracy, demonstrating a reduction of the bias error due to the ghost particles. The improvement is more remarkable at the largest tested seeding densities. Additionally, using the blobs distributions as a predictor enables further improvement of the convergence of the reconstruction algorithm, with the improvement being more considerable when substituting the blobs more than once during the process. The BERT process is also applied to multi resolution (MR) CSMART reconstructions, permitting simultaneously to achieve remarkable improvements in the flow field measurements and to benefit from the reduction in computational time due to the MR approach. Finally, BERT is also tested on experimental data, obtaining an increase of the
Numerical linear algebra for reconstruction inverse problems
NASA Astrophysics Data System (ADS)
Nachaoui, Abdeljalil
2004-01-01
Our goal in this paper is to discuss various issues we have encountered in trying to find and implement efficient solvers for a boundary integral equation (BIE) formulation of an iterative method for solving a reconstruction problem. We survey some methods from numerical linear algebra, which are relevant for the solution of this class of inverse problems. We motivate the use of our constructing algorithm, discuss its implementation and mention the use of preconditioned Krylov methods.
NASA Astrophysics Data System (ADS)
Jiang, Yu; Xu, Feiyun; Xu, Bingsheng
2015-12-01
Acoustic Emission (AE) tomography based on Simultaneous Algebraic Reconstruction Technique (SART), which combines the traditional location algorithm with the SART algorithm by using AE events as its signal sources, is a new visualization method for inspecting and locating the internal damages in the structure. In this paper, the proposed method is applied to examine and visualize two man-made damage source locations in the Q235B steel plate to validate its effectiveness. Firstly, the Q235B steel plate with two holes specimen is fabricated and the pencil lead break (PLB) signal is taken as the exciting source for AE tomography.Secondly, A 6-step description of the SART algorithm is provided and the three dimensional(3D)image contained the damage source locations is visualized by using the proposed algorithm in terms of a locally varying wave velocity distribution. It is shown that the AE tomography based on SART has great potential in the application of structure damage detection. Finally, to further improve the quality of 3D imaging, the Median Filter and the Adaptive Median Filter are used to reduce the noises resulting from AE tomography. The experiment results indicate that Median Filter is the optimal method to remove Salt & Pepper noises.
Optimal Discretization Resolution in Algebraic Image Reconstruction
NASA Astrophysics Data System (ADS)
Sharif, Behzad; Kamalabadi, Farzad
2005-11-01
In this paper, we focus on data-limited tomographic imaging problems where the underlying linear inverse problem is ill-posed. A typical regularized reconstruction algorithm uses algebraic formulation with a predetermined discretization resolution. If the selected resolution is too low, we may loose useful details of the underlying image and if it is too high, the reconstruction will be unstable and the representation will fit irrelevant features. In this work, two approaches are introduced to address this issue. The first approach is using Mallow's CL method or generalized cross-validation. For each of the two methods, a joint estimator of regularization parameter and discretization resolution is proposed and their asymptotic optimality is investigated. The second approach is a Bayesian estimator of the model order using a complexity-penalizing prior. Numerical experiments focus on a space imaging application from a set of limited-angle tomographic observations.
Algebraic reconstruction and postprocessing in one-step diffuse optical tomography
Konovalov, A B; Vlasov, V V; Mogilenskikh, D V; Kravtsenyuk, O V; Lyubimov, V V
2008-06-30
The photon average trajectory method is considered, which is used as an approximate method of diffuse optical tomography and is based on the solution of the Radon-like trajectory integral equation. A system of linear algebraic equations describing a discrete model of object reconstruction is once inverted by using a modified multiplicative algebraic technique. The blurring of diffusion tomograms is eliminated by using space-varying restoration and methods of nonlinear colour interpretation of data. The optical models of the breast tissue in the form of rectangular scattering objects with circular absorbing inhomogeneities are reconstructed within the framework of the numerical experiment from optical projections simulated for time-domain measurement technique. It is shown that the quality of diffusion tomograms reconstructed by this method is close to that of tomograms reconstructed by using Newton-like multistep algorithms, while the computational time is much shorter. (special issue devoted to application of laser technologies in biophotonics and biomedical studies)
Kim, Joshua; Ionascu, Dan; Zhang, Tiezhi
2013-01-01
Purpose: To accelerate iterative algebraic reconstruction algorithms using a cylindrical image grid. Methods: Tetrahedron beam computed tomography (TBCT) is designed to overcome the scatter and detector problems of cone beam computed tomography (CBCT). Iterative algebraic reconstruction algorithms have been shown to mitigate approximate reconstruction artifacts that appear at large cone angles, but clinical implementation is limited by their high computational cost. In this study, a cylindrical voxelization method on a cylindrical grid is developed in order to take advantage of the symmetries of the cylindrical geometry. The cylindrical geometry is a natural fit for the circular scanning trajectory employed in volumetric CT methods such as CBCT and TBCT. This method was implemented in combination with the simultaneous algebraic reconstruction technique (SART). Both two- and three-dimensional numerical phantoms as well as a patient CT image were utilized to generate the projection sets used for reconstruction. The reconstructed images were compared to the original phantoms using a set of three figures of merit (FOM). Results: The cylindrical voxelization on a cylindrical reconstruction grid was successfully implemented in combination with the SART reconstruction algorithm. The FOM results showed that the cylindrical reconstructions were able to maintain the accuracy of the Cartesian reconstructions. In three dimensions, the cylindrical method provided better accuracy than the Cartesian methods. At the same time, the cylindrical method was able to provide a speedup factor of approximately 40 while also reducing the system matrix storage size by 2 orders of magnitude. Conclusions: TBCT image reconstruction using a cylindrical image grid was able to provide a significant improvement in the reconstruction time and a more compact system matrix for storage on the hard drive and in memory while maintaining the image quality provided by the Cartesian voxelization on a
Lin, Yu; Liao, Ning-fang; Luo, Yong-dao; Cui, De-qi; Tan, Bo-neng; Wu, Wen-min
2010-08-01
In the present paper, the authors will introduce our research on spectral reconstruction of Fourier transform computed tomography imaging spectrometer by means of the algebraic reconstruction technology. A simulation experiment was carried out to demonstrate the algorithm. The spatial similarities and spectral similarities were evaluated using the normalized correlation coefficient. The performance of ART was evaluated when the quantity of projection is 45. In that case, filter back projection can't work well. Actual spectral slices were reconstructed by using ART in the last part of this paper. PMID:20939312
Experimental investigation of iterative reconstruction techniques for high resolution mammography
NASA Astrophysics Data System (ADS)
Vengrinovich, Valery L.; Zolotarev, Sergei A.; Linev, Vladimir N.
2014-02-01
The further development of the new iterative reconstruction algorithms to improve three-dimensional breast images quality restored from incomplete and noisy mammograms, is provided. The algebraic reconstruction method with simultaneous iterations - Simultaneous Algebraic Reconstruction Technique (SART) and the iterative method of statistical reconstruction Bayesian Iterative Reconstruction (BIR) are referred here as the preferable iterative methods suitable to improve the image quality. For better processing we use the Graphics Processing Unit (GPU). Method of minimizing the Total Variation (TV) is used as a priori support for regularization of iteration process and to reduce the level of noise in the reconstructed image. Preliminary results with physical phantoms show that all examined methods are capable to reconstruct structures layer-by-layer and to separate layers which images are overlapped in the Z- direction. It was found that the method of traditional Shift-And-Add tomosynthesis (SAA) is worse than iterative methods SART and BIR in terms of suppression of the anatomical noise and image blurring in between the adjacent layers. Despite of the fact that the measured contrast/noise ratio in the presence of low contrast internal structures is higher for the method of tomosynthesis SAA than for SART and BIR methods, its effectiveness in the presence of structured background is rather poor. In our opinion the optimal results can be achieved using Bayesian iterative reconstruction BIR.
Algebraic filter approach for fast approximation of nonlinear tomographic reconstruction methods
NASA Astrophysics Data System (ADS)
Plantagie, Linda; Batenburg, Kees Joost
2015-01-01
We present a computational approach for fast approximation of nonlinear tomographic reconstruction methods by filtered backprojection (FBP) methods. Algebraic reconstruction algorithms are the methods of choice in a wide range of tomographic applications, yet they require significant computation time, restricting their usefulness. We build upon recent work on the approximation of linear algebraic reconstruction methods and extend the approach to the approximation of nonlinear reconstruction methods which are common in practice. We demonstrate that if a blueprint image is available that is sufficiently similar to the scanned object, our approach can compute reconstructions that approximate iterative nonlinear methods, yet have the same speed as FBP.
Algebraic and analytic reconstruction methods for dynamic tomography.
Desbat, L; Rit, S; Clackdoyle, R; Mennessier, C; Promayon, E; Ntalampeki, S
2007-01-01
In this work, we discuss algebraic and analytic approaches for dynamic tomography. We present a framework of dynamic tomography for both algebraic and analytic approaches. We finally present numerical experiments. PMID:18002059
Iterative reconstruction techniques for industrial CT: application and performance
Arrowood, Lloyd; Gregor, Jens; Bingham, Philip R
2008-01-01
BWXT Y-12, Oak Ridge National Laboratory, and the University of Tennessee have been working toward improved high-resolution X-ray computed tomography for non-destructive testing of manufactured objects. The emphasis of this work has been on iterative reconstruction, calibration, and performance testing. Algebraic reconstruction algorithms for CT have been developed that are more robust in handling incomplete and noisy data and permit high-resolution volumetric imaging on metallic part assemblies. A key source of artifacts in reconstructed CT images for industrial components is poor image statistics due to areas of high attenuation. This loss of information in the captured projections not only affects reconstruction of those areas, but also the surrounding regions. To overcome numerical instabilities arising from the ill-posed nature of inverse problems, standard regularization techniques can be applied as can Bayesian reconstruction techniques using prior data such as CAD information to improve image quality. To accelerate the reconstruction of certain regions of interest and reduce memory requirements, subvolume reconstruction has been implemented and tested. A computational framework has been implemented that facilitates the use of sophisticated iterative algorithms for reconstruction of three-dimensional images from high-resolution X-ray cone-beam projection data. The code supports parallel computing at two levels: message passing is used to farm the computation out across a network of computers while threads allow all processors available on any one computer to be used.
Fu, Jian; Hu, Xinhua; Velroyen, Astrid; Bech, Martin; Jiang, Ming; Pfeiffer, Franz
2015-01-01
Due to the potential of compact imaging systems with magnified spatial resolution and contrast, cone-beam x-ray differential phase-contrast computed tomography (DPC-CT) has attracted significant interest. The current proposed FDK reconstruction algorithm with the Hilbert imaginary filter will induce severe cone-beam artifacts when the cone-beam angle becomes large. In this paper, we propose an algebraic iterative reconstruction (AIR) method for cone-beam DPC-CT and report its experiment results. This approach considers the reconstruction process as the optimization of a discrete representation of the object function to satisfy a system of equations that describes the cone-beam DPC-CT imaging modality. Unlike the conventional iterative algorithms for absorption-based CT, it involves the derivative operation to the forward projections of the reconstructed intermediate image to take into account the differential nature of the DPC projections. This method is based on the algebraic reconstruction technique, reconstructs the image ray by ray, and is expected to provide better derivative estimates in iterations. This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured with a three-grating interferometer and a mini-focus x-ray tube source. It is shown that the proposed method can reduce the cone-beam artifacts and performs better than FDK under large cone-beam angles. This algorithm is of interest for future cone-beam DPC-CT applications. PMID:25775480
Microtia reconstruction: autologous rib and alloplast techniques.
Cabin, Jonathan A; Bassiri-Tehrani, Michael; Sclafani, Anthony P; Romo, Thomas
2014-11-01
Microtia represents a spectrum of maldevelopment of the external ear. Reconstructive techniques may utilize an autogenous rib cartilage framework and require 2-4 stages; alternatively, an alloplastic framework can be used and typically requires 1-2 stages. Successful reconstruction of microtia with either technique can provide a significant quality of life improvement, and both techniques are described in this article. PMID:25444733
A grid spacing control technique for algebraic grid generation methods
NASA Technical Reports Server (NTRS)
Smith, R. E.; Kudlinski, R. A.; Everton, E. L.
1982-01-01
A technique which controls the spacing of grid points in algebraically defined coordinate transformations is described. The technique is based on the generation of control functions which map a uniformly distributed computational grid onto parametric variables defining the physical grid. The control functions are smoothed cubic splines. Sets of control points are input for each coordinate directions to outline the control functions. Smoothed cubic spline functions are then generated to approximate the input data. The technique works best in an interactive graphics environment where control inputs and grid displays are nearly instantaneous. The technique is illustrated with the two-boundary grid generation algorithm.
Pixel-based reconstruction (PBR) promising simultaneous techniques for CT reconstructions
Fager, R.S. . Office of the Associate Provost for Research); Peddanarappagari, K.V.; Kumar, G.N. . Dept. of Electrical Engineering)
1993-03-01
The authors present some new algorithms belonging to a class of algorithms, pixel-based reconstruction (PBR), similar to SIRT' (simultaneous iterative reconstruction techniques) methods for reconstruction of objects from their fan beam projections in x-ray transmission tomography. The general logic of these algorithms is discussed, and, as a corollary, two new ideas are presented, which gave promising results in the simulation studies. It was found in the simulation studies, contrary to previous results with parallel beam projections, that these iterative algebraic algorithms don't diverge when a more logical technique of obtaining the pseudo-projections is used. These simulations were carried out under conditions where the number of object pixels exceeded (double) the number of detector pixel readings, i.e., the equations were highly under-determined; however, the reconstructions were quite satisfactory. The effect of the number of projections on the reconstruction and the convergence to the exact solution is shown. For comparison, the reconstructions obtained by convolution back-projection are also given.
A maximum entropy reconstruction technique for tomographic particle image velocimetry
NASA Astrophysics Data System (ADS)
Bilsky, A. V.; Lozhkin, V. A.; Markovich, D. M.; Tokarev, M. P.
2013-04-01
This paper studies a novel approach for reducing tomographic PIV computational complexity. The proposed approach is an algebraic reconstruction technique, termed MENT (maximum entropy). This technique computes the three-dimensional light intensity distribution several times faster than SMART, using at least ten times less memory. Additionally, the reconstruction quality remains nearly the same as with SMART. This paper presents the theoretical computation performance comparison for MENT, SMART and MART, followed by validation using synthetic particle images. Both the theoretical assessment and validation of synthetic images demonstrate significant computational time reduction. The data processing accuracy of MENT was compared to that of SMART in a slot jet experiment. A comparison of the average velocity profiles shows a high level of agreement between the results obtained with MENT and those obtained with SMART.
Reconstruction techniques for optoacoustic imaging
NASA Astrophysics Data System (ADS)
Frenz, Martin; Koestli, Kornel P.; Paltauf, Guenther; Schmidt-Kloiber, Heinz; Weber, Heinz P.
2001-06-01
Optoacoustics is a method to gain information from inside a tissue. This is done by irradiating a tissue with a short light pulse, which generates a pressure distribution inside the tissue that mirrors the absorber distribution. The pressure distribution measured on the tissue-surface allows, by applying a back-projection method, to calculate a tomography image of the absorber distribution. This study presents a novel computational algorithm based on Fourier transform, which, at least in principle, yields an exact 3D reconstruction of the distribution of absorbed energy density inside turbid media. The reconstruction is based on 2D pressure distributions captured outside at different times. The FFT reconstruction algorithm is first tested in the back projection of simulated pressure transients of small model absorbers, and finally applied to reconstruct the distribution of artificial blood vessels in three dimensions.
FIRT: Filtered iterative reconstruction technique with information restoration.
Chen, Yu; Zhang, Yan; Zhang, Kai; Deng, Yuchen; Wang, Shengliu; Zhang, Fa; Sun, Fei
2016-07-01
Electron tomography (ET) combining subsequent sub-volume averaging has been becoming a unique way to study the in situ 3D structures of macromolecular complexes. However, information missing in electron tomography due to limited angular sampling is still the bottleneck in high-resolution electron tomography application. Here, based on the understanding of smooth nature of biological specimen, we present a new iterative image reconstruction algorithm, FIRT (filtered iterative reconstruction technique) for electron tomography by combining the algebra reconstruction technique (ART) and the nonlinear diffusion (ND) filter technique. Using both simulated and experimental data, in comparison to ART and weight back projection method, we proved that FIRT could generate a better reconstruction with reduced ray artifacts and significant improved correlation with the ground truth and partially restore the information at the non-sampled angular region, which was proved by investigating the 90° re-projection and by the cross-validation method. This new algorithm will be subsequently useful in the future for both cellular and molecular ET with better quality and improved structural details. PMID:27134004
Reconstruction of symmetric Dirac-Maxwell equations using nonassociative algebra
NASA Astrophysics Data System (ADS)
Kalauni, Pushpa; Barata, J. C. A.
2015-01-01
In the presence of sources, the usual Maxwell equations are neither symmetric nor invariant with respect to the duality transformation between electric and magnetic fields. Dirac proposed the existence of magnetic monopoles for symmetrizing the Maxwell equations. In the present work, we obtain the fully symmetric Dirac-Maxwell's equations (i.e. with electric and magnetic charges and currents) as a single equation by using 4 × 4 matrix presentation of fields and derivative operators. This matrix representation has been derived with the help of the algebraic properties of quaternions and octonions. Such description gives a compact representation of electric and magnetic counterparts of the field in a single equation.
An efficient simultaneous reconstruction technique for tomographic particle image velocimetry
NASA Astrophysics Data System (ADS)
Atkinson, Callum; Soria, Julio
2009-10-01
To date, Tomo-PIV has involved the use of the multiplicative algebraic reconstruction technique (MART), where the intensity of each 3D voxel is iteratively corrected to satisfy one recorded projection, or pixel intensity, at a time. This results in reconstruction times of multiple hours for each velocity field and requires considerable computer memory in order to store the associated weighting coefficients and intensity values for each point in the volume. In this paper, a rapid and less memory intensive reconstruction algorithm is presented based on a multiplicative line-of-sight (MLOS) estimation that determines possible particle locations in the volume, followed by simultaneous iterative correction. Reconstructions of simulated images are presented for two simultaneous algorithms (SART and SMART) as well as the now standard MART algorithm, which indicate that the same accuracy as MART can be achieved 5.5 times faster or 77 times faster with 15 times less memory if the processing and storage of the weighting matrix is considered. Application of MLOS-SMART and MART to a turbulent boundary layer at Re θ = 2200 using a 4 camera Tomo-PIV system with a volume of 1,000 × 1,000 × 160 voxels is discussed. Results indicate improvements in reconstruction speed of 15 times that of MART with precalculated weighting matrix, or 65 times if calculation of the weighting matrix is considered. Furthermore the memory needed to store a large weighting matrix and volume intensity is reduced by almost 40 times in this case.
Unsupervised color image segmentation using a lattice algebra clustering technique
NASA Astrophysics Data System (ADS)
Urcid, Gonzalo; Ritter, Gerhard X.
2011-08-01
In this paper we introduce a lattice algebra clustering technique for segmenting digital images in the Red-Green- Blue (RGB) color space. The proposed technique is a two step procedure. Given an input color image, the first step determines the finite set of its extreme pixel vectors within the color cube by means of the scaled min-W and max-M lattice auto-associative memory matrices, including the minimum and maximum vector bounds. In the second step, maximal rectangular boxes enclosing each extreme color pixel are found using the Chebychev distance between color pixels; afterwards, clustering is performed by assigning each image pixel to its corresponding maximal box. The two steps in our proposed method are completely unsupervised or autonomous. Illustrative examples are provided to demonstrate the color segmentation results including a brief numerical comparison with two other non-maximal variations of the same clustering technique.
Tissue transfer techniques in reconstructive urology
Bryk, Darren J; Yamaguchi, Yuka
2015-01-01
Tissue transfer techniques are an essential part of the reconstructive urologist's armamentarium. Flaps and graft techniques are widely used in genital and urethral reconstruction. A graft is tissue that is moved from a donor site to a recipient site without its native blood supply. The main types of grafts used in urology are full thickness grafts, split thickness skin grafts and buccal mucosa grafts. Flaps are transferred from the donor site to the recipient site on a pedicle containing its native blood supply. Flaps can be classified based on blood supply, elevation methods or the method of transfer. The most used flaps in urology include penile, preputial, and scrotal skin. We review the various techniques used in reconstructive urology and the outcomes of these techniques. PMID:26175866
Surgical technique affects outcomes in acromioclavicular reconstruction.
Grassbaugh, Jason A; Cole, Chad; Wohlrab, Kurt; Eichinger, Josef
2013-01-01
Optimal treatment for acromioclavicular (AC) dislocation is unknown. Numerous surgical procedures for AC injuries have been described with little comparison. This study sought to compare the clinical and radiographic results of various surgical techniques in order to identify the optimal surgical technique. Ninety patients met inclusion criteria of AC reconstruction at this institution. A retrospective review of outcomes was performed using the electronic records system. Radiographs were measured for pre- and postoperative grade and percent elevation versus the contralateral side. Overall revision rate was 9%. Suture button fixation had a revision rate of 0% compared to 14% (p = .01). Reconstruction procedures performed with distal clavicle excision showed a higher revision rate, 17% compared to 0% (p = .003). There were no statistically significant clinical differences. AC reconstructions performed with suture button construct were superior to other surgical techniques. Procedures performed with distal clavicle excision were inferior to those without. PMID:23449059
Application of computer algebra-techniques to metabolic control analysis.
Bayram, Mustafa; Celik, Ercan
2003-05-01
For practical purposes the calculation of rate constants is not particularly valuable, since their physical significance is not clear. Of greater practical use are metabolic control coefficients and elasticities. Given the definition of the flux control coefficients C(E)(J), concentration control coefficient C(E)(X) and elasticity epsilon (X)(v(1)). We can calculate symbolic formulae for these using computer algebra-techniques. These are then functions of V(max), K(m), K(i) enzyme and concentrations. Having derived estimates of V(max), K(m), K(i) using the fitting method we can then calculate values of the control coefficients and elasticities. Furthermore we can calculate the metabolic control parameters using symbolic values for the conventional kinetic parameters. Using these we have verified the summation and connectivity theorems. This is a useful cross check on the reliability of the calculations. PMID:12821311
Pancreatectomy with vein reconstruction: technique matters
Dua, Monica M; Tran, Thuy B; Klausner, Jill; Hwa, Kim J; Poultsides, George A; Norton, Jeffrey A; Visser, Brendan C
2015-01-01
Background A variety of techniques have been described for portal vein (PV) and/or superior mesenteric vein (SMV) resection/reconstruction during a pancreatectomy. The ideal strategy remains unclear. Methods Patients who underwent PV/SMV resection/reconstruction during a pancreatectomy from 2005 to 2014 were identified. Medical records and imaging were retrospectively reviewed for operative details and outcomes, with particular emphasis on patency. Results Ninety patients underwent vein resection/reconstruction with one of five techniques: (i) longitudinal venorrhaphy (LV, n = 17); (ii) transverse venorrhaphy (TV, n = 9); (iii) primary end-to-end (n = 28); (iv) patch venoplasty (PV, n = 17); and (v) interposition graft (IG, n = 19). With a median follow-up of 316 days, thrombosis was observed in 16/90 (18%). The rate of thrombosis varied according to technique. All patients with primary end-to-end or TV remained patent. LV, PV and IG were all associated with significant rates of thrombosis (P = 0.001 versus no thrombosis). Comparing thrombosed to patent, there were no differences with respect to pancreatectomy type, pre-operative knowledge of vein involvement and neoadjuvant therapy. Prophylactic aspirin was used in 69% of the total cohort (66% of patent, 81% of thrombosed) and showed no protective benefit. Conclusions Primary end-to-end and TV have superior patency than the alternatives after PV/SMV resection and should be the preferred techniques for short (<3 cm) reconstructions. PMID:26223388
Kim, D; Kang, S; Kim, T; Suh, T; Kim, S
2014-06-01
Purpose: In this paper, we implemented the four-dimensional (4D) digital tomosynthesis (DTS) imaging based on algebraic image reconstruction technique and total-variation minimization method in order to compensate the undersampled projection data and improve the image quality. Methods: The projection data were acquired as supposed the cone-beam computed tomography system in linear accelerator by the Monte Carlo simulation and the in-house 4D digital phantom generation program. We performed 4D DTS based upon simultaneous algebraic reconstruction technique (SART) among the iterative image reconstruction technique and total-variation minimization method (TVMM). To verify the effectiveness of this reconstruction algorithm, we performed systematic simulation studies to investigate the imaging performance. Results: The 4D DTS algorithm based upon the SART and TVMM seems to give better results than that based upon the existing method, or filtered-backprojection. Conclusion: The advanced image reconstruction algorithm for the 4D DTS would be useful to validate each intra-fraction motion during radiation therapy. In addition, it will be possible to give advantage to real-time imaging for the adaptive radiation therapy. This research was supported by Leading Foreign Research Institute Recruitment Program (Grant No.2009-00420) and Basic Atomic Energy Research Institute (BAERI); (Grant No. 2009-0078390) through the National Research Foundation of Korea(NRF) funded by the Ministry of Science, ICT and Future Planning (MSIP)
Geometric and algebraic multigrid techniques for fluid dynamics problems on unstructured grids
NASA Astrophysics Data System (ADS)
Volkov, K. N.; Emel'yanov, V. N.; Teterina, I. V.
2016-02-01
Issues concerning the implementation and practical application of geometric and algebraic multigrid techniques for solving systems of difference equations generated by the finite volume discretization of the Euler and Navier-Stokes equations on unstructured grids are studied. The construction of prolongation and interpolation operators, as well as grid levels of various resolutions, is discussed. The results of the application of geometric and algebraic multigrid techniques for the simulation of inviscid and viscous compressible fluid flows over an airfoil are compared. Numerical results show that geometric methods ensure faster convergence and weakly depend on the method parameters, while the efficiency of algebraic methods considerably depends on the input parameters.
NASA Astrophysics Data System (ADS)
Nara, T.; Koiwa, K.; Takagi, S.; Oyama, D.; Uehara, G.
2014-05-01
This paper presents an algebraic reconstruction method for dipole-quadrupole sources using magnetoencephalography data. Compared to the conventional methods with the equivalent current dipoles source model, our method can more accurately reconstruct two close, oppositely directed sources. Numerical simulations show that two sources on both sides of the longitudinal fissure of cerebrum are stably estimated. The method is verified using a quadrupolar source phantom, which is composed of two isosceles-triangle-coils with parallel bases.
Reconstruction techniques of holograms from Spacelab 3
NASA Technical Reports Server (NTRS)
Witherow, William K.
1987-01-01
Fluid transport effects in a ground-based laboratory are fairly well known. Bouyancy driven transport occurs when there is a local density change in the fluid. In a low-g environment these density changes become less important, and other transport mechanisms dominate. To better understand fluid flows in a low-g environment, a fluid experiment system (FES) was designed to fly aboard the Shuttle orbiter in Spacelab. The FES is a holographic system designed for acquisition of the maximum amount of data from an experiment. The FES flew for the first time in May 1985 on Spacelab 3 for investigation of triglycine sulfate (TGS) crystal growth in low-g. This paper describes the FES optical system. The reconstruction techniques of the holograms are examined in detail, and the multiuser and reflight capabilities are discussed. Proposed future experiments are mentioned.
Auricular reconstruction for microtia: Part II. Surgical techniques.
Walton, Robert L; Beahm, Elisabeth K
2002-07-01
Reconstruction of the microtic ear represents one of the most demanding challenges in reconstructive surgery. In this review the two most commonly used techniques for ear reconstruction, the Brent and Nagata techniques, are addressed in detail. Unique to this endeavor, the originator of each technique has been allowed to submit representative case material and to address the pros and cons of the other's technique. What follows is a detailed, insightful overview of microtia reconstruction, as a state of the art. The review then details commonly encountered problems in ear reconstruction and pertinent technical points. Finally, a glimpse into the future is offered with an accounting of the advances made in tissue engineering as this technology applies to auricular reconstruction. PMID:12087261
Optimization techniques for OpenCL-based linear algebra routines
NASA Astrophysics Data System (ADS)
Kozacik, Stephen; Fox, Paul; Humphrey, John; Kuller, Aryeh; Kelmelis, Eric; Prather, Dennis W.
2014-06-01
The OpenCL standard for general-purpose parallel programming allows a developer to target highly parallel computations towards graphics processing units (GPUs), CPUs, co-processing devices, and field programmable gate arrays (FPGAs). The computationally intense domains of linear algebra and image processing have shown significant speedups when implemented in the OpenCL environment. A major benefit of OpenCL is that a routine written for one device can be run across many different devices and architectures; however, a kernel optimized for one device may not exhibit high performance when executed on a different device. For this reason kernels must typically be hand-optimized for every target device family. Due to the large number of parameters that can affect performance, hand tuning for every possible device is impractical and often produces suboptimal results. For this work, we focused on optimizing the general matrix multiplication routine. General matrix multiplication is used as a building block for many linear algebra routines and often comprises a large portion of the run-time. Prior work has shown this routine to be a good candidate for high-performance implementation in OpenCL. We selected several candidate algorithms from the literature that are suitable for parameterization. We then developed parameterized kernels implementing these algorithms using only portable OpenCL features. Our implementation queries device information supplied by the OpenCL runtime and utilizes this as well as user input to generate a search space that satisfies device and algorithmic constraints. Preliminary results from our work confirm that optimizations are not portable from one device to the next, and show the benefits of automatic tuning. Using a standard set of tuning parameters seen in the literature for the NVIDIA Fermi architecture achieves a performance of 1.6 TFLOPS on an AMD 7970 device, while automatically tuning achieves a peak of 2.7 TFLOPS
Jiang, Tongsong; Jiang, Ziwu; Zhang, Zhaozhong
2015-08-15
In the study of the relation between complexified classical and non-Hermitian quantum mechanics, physicists found that there are links to quaternionic and split quaternionic mechanics, and this leads to the possibility of employing algebraic techniques of split quaternions to tackle some problems in complexified classical and quantum mechanics. This paper, by means of real representation of a split quaternion matrix, studies the problem of diagonalization of a split quaternion matrix and gives algebraic techniques for diagonalization of split quaternion matrices in split quaternionic mechanics.
NASA Astrophysics Data System (ADS)
Jiang, Tongsong; Jiang, Ziwu; Zhang, Zhaozhong
2015-08-01
In the study of the relation between complexified classical and non-Hermitian quantum mechanics, physicists found that there are links to quaternionic and split quaternionic mechanics, and this leads to the possibility of employing algebraic techniques of split quaternions to tackle some problems in complexified classical and quantum mechanics. This paper, by means of real representation of a split quaternion matrix, studies the problem of diagonalization of a split quaternion matrix and gives algebraic techniques for diagonalization of split quaternion matrices in split quaternionic mechanics.
Investigating a hybrid perturbation-Galerkin technique using computer algebra
NASA Technical Reports Server (NTRS)
Andersen, Carl M.; Geer, James F.
1988-01-01
A two-step hybrid perturbation-Galerkin method is presented for the solution of a variety of differential equations type problems which involve a scalar parameter. The resulting (approximate) solution has the form of a sum where each term consists of the product of two functions. The first function is a function of the independent field variable(s) x, and the second is a function of the parameter lambda. In step one the functions of x are determined by forming a perturbation expansion in lambda. In step two the functions of lambda are determined through the use of the classical Bubnov-Gelerkin method. The resulting hybrid method has the potential of overcoming some of the drawbacks of the perturbation and Bubnov-Galerkin methods applied separately, while combining some of the good features of each. In particular, the results can be useful well beyond the radius of convergence associated with the perturbation expansion. The hybrid method is applied with the aid of computer algebra to a simple two-point boundary value problem where the radius of convergence is finite and to a quantum eigenvalue problem where the radius of convergence is zero. For both problems the hybrid method apparently converges for an infinite range of the parameter lambda. The results obtained from the hybrid method are compared with approximate solutions obtained by other methods, and the applicability of the hybrid method to broader problem areas is discussed.
Computational Techniques in Radio Neutrino Event Reconstruction
NASA Astrophysics Data System (ADS)
Beydler, M.; ARA Collaboration
2016-03-01
The Askaryan Radio Array (ARA) is a high-energy cosmic neutrino detector constructed with stations of radio antennas buried in the ice at the South Pole. Event reconstruction relies on the analysis of the arrival times of the transient radio signals generated by neutrinos interacting within a few kilometers of the detector. Because of its depth dependence, the index of refraction in the ice complicates the interferometric directional reconstruction of possible neutrino events. Currently, there is an ongoing endeavor to enhance the programs used for the time-consuming computations of the curved paths of the transient wave signals in the ice as well as the interferometric beamforming. We have implemented a fast, multi-dimensional spline table lookup of the wave arrival times in order to enable raytrace-based directional reconstructions. Additionally, we have applied parallel computing across multiple Graphics Processing Units (GPUs) in order to perform the beamforming calculations quickly.
Advanced Techniques for Fourier Transform Wavefront Reconstruction
Poyneer, L A
2002-08-05
The performance of Fourier transform (FT) reconstructors in large adaptive optics systems with Shack-Hartmann sensors and a deformable mirror is analyzed. FT methods, which are derived for point-based geometries, are adapted for use on the continuous systems. Analysis and simulation show how to compensate for effects such as misalignment of the deformable mirror and wavefront sensor gain. Further filtering methods to reduce noise and improve performance are presented. All these modifications can be implemented at the filtering stage, preserving the speed of FT reconstruction. Simulation of a large system shows how compensated FT methods can have equivalent or better performance to slower vector-matrix-multiply reconstructions.
Oncologic reconstruction: General principles and techniques.
Ho, Adelyn L; Lyonel Carre, Antoine; Patel, Ketan M
2016-06-01
Halsted's principle of radical mastectomy influenced cancer treatment for decades. Randomized controlled trials resulted in a paradigm shift to less radical surgery and the use of adjuvant therapies. Oncologic reconstruction performed by plastic surgeons has evolved, ranging from skin grafts and local flaps for smaller defects to pedicled flaps and free flaps for larger and more complex defects. Immediate reconstruction facilitates resection is oncologically safe and contributes to meaningful improvements in quality of life. J. Surg. Oncol. 2016;113:852-864. © 2016 Wiley Periodicals, Inc. PMID:26939879
Analysis of higher order optical aberrations in the SLC final focus using Lie Algebra techniques
Walker, N.J.; Irwin, J.; Woodley, M.
1993-04-01
The SLC final focus system is designed to have an overall demagnification of 30:1, with a {beta} at the interaction point ({beta}*) of 5 mm, and an energy band pass of {approximately}0.4%. Strong sextupole pairs are used to cancel the large chromaticity which accrues primarily from the final triplet. Third-order aberrations limit the performance of the system, the dominating terms being U{sub 1266} and U{sub 3466} terms (in the notation of K. Brown). Using Lie Algebra techniques, it is possible to analytically calculate the soave of these terms in addition to understanding their origin. Analytical calculations (using Lie Algebra packages developed in the Mathematica language) are presented of the bandwidth and minimum spot size as a function of divergence at the interaction point (IP). Comparisons of the analytical results from the Lie Algebra maps and results from particle tracking (TURTLE) are also presented.
Novel technique for ulnar collateral ligament reconstruction of the elbow.
Acevedo, Daniel C; Lee, Brian; Mirzayan, Raffy
2012-11-01
Ulnar collateral ligament (UCL) reconstruction of the elbow has been shown to restore function in overhead athletes with valgus instability. Since the initial description of using bone tunnels for reconstruction, many modifications to the surgical technique have been introduced, including the modified Jobe technique, the docking technique, fixation with interference screws, and button fixation. The authors introduce a technique that uses a button on each of the humeral and ulnar sides for fixation. This method allows proper tensioning of the graft and provides immediate secure fixation that relies on metal implants as opposed to sutures over bone bridges alone. PMID:23127439
Anatomic Reconstruction Technique for a Plantar Calcaneonavicular (Spring) Ligament Tear.
Palmanovich, Ezequiel; Shabat, Shay; Brin, Yaron S; Feldman, Viktor; Kish, Benny; Nyska, Meir
2015-01-01
Acquired flatfoot deformity in adults is usually due to partial or complete tearing of the posterior tibial tendon, with secondary failure of other structures such as the plantar calcaneonavicular (spring) ligament (SL), which maintain the medial longitudinal arch. In flexible cases, the tibialis posterior can be replaced with the flexor digitorum longus. It is common practice to suture the SL directly in the case of a tear; however, if the tear is complete, suturing directly to the ligament alone will not be possible. Reconstruction of the ligament is needed; however, no validated methods are available to reconstruct this ligament. The operative technique of SL reconstruction described in this report as a part of acquired flatfoot deformity reconstruction consists of augmenting remnants of the spring from the navicularis to the sustentaculum tali and suspending it to the medial malleolus using 2-mm-wide, long-chain polyethylene suture tape. This technique results in the firm anatomic reconstruction of the SL, in addition to "classic" medial arch reconstruction. We recommend SL reconstruction for medial arch reconstruction when the SL is torn. PMID:26253476
Nipple-areola complex reconstruction techniques: A literature review.
Sisti, A; Grimaldi, L; Tassinari, J; Cuomo, R; Fortezza, L; Bocchiotti, M A; Roviello, F; D'Aniello, C; Nisi, G
2016-04-01
Many techniques for nipple-areola complex (NAC) reconstruction are described. Clarity is required on the currently available options. Since a complete list of all the techniques described until now is not available, a possibly comprehensive literature overview was carried out from 75 papers (years 1946-2015). The local flap was the most frequently described technique for the nipple reconstruction with no significant difference in complications' rate among the various types of techniques. Complications in nipple reconstruction were 46.9% after graft, 7.9% after local flap, and 5.3% in case of flaps with autologous graft/alloplastic/allograft augmentation, while complications in areola reconstruction were 10.1% after graft, and 1.6% after areola tattoo. Flaps appear to be more reliable than grafts in nipple reconstruction, while tattoo is thought to be safer than graft in areola reconstruction. The loss of projection, although considerable (45%-75%), had not significant impact on patients' satisfaction. Due to contraction, overcorrection of 25-50% of the desired result is advisory when adopting local flaps, in order to prevent loss of projection. The use of flaps with autologous graft/alloplastic/allograft augmentation (cartilage, fat, calcium hydroxylapatite, acellular dermal matrix, polymethylmethacrylate, biologic collagen) showed a minor loss of nipple projection but may expose to a relative increased number of postoperative flap necrosis. PMID:26868167
Wu, Gang; Yaffe, Martin J.; Mainprize, James G.
2013-10-15
Purpose: The order in which the projection views are employed in the reconstruction of tomosynthesis by iterative algorithms, such as simultaneous algebraic reconstruction technique and maximum likelihood, has a strong effect on the rate of convergence, accuracy, and the edge-blurring artifacts in the reconstructed image. The purpose of this investigation was to characterize and evaluate the effects of ordering schemes on image quality for breast tomosynthesis reconstruction and to explore a new constrained paired-view technique that could provide reduction of reconstruction artifacts. In this work, the authors compared several different ordering schemes and characterized the image quality and the formation of out-of-plane artifacts. Furthermore, a new normalization method is presented. It produces more accurate reconstructions with reduced artifacts comparing to the standard method of sequential ordering.Methods: In addition to visual assessment of image quality, several indices such as the signal-difference-to-noise ratio, the artifact-spread function, and the lesion detectability (d{sup ′}) were computed to quantitatively evaluate the effect of ordering scheme. The sets of breast tomosynthesis projection images were simulated for reconstruction; one set had uniform background (white noise only) and the other two contained both anatomic background and quantum noise. Clinical breast images were also studied for comparison.Results: The authors have quantified the image quality in reconstructed slices for a range of tumor sizes. The authors’ proposed method provides better performance for all of the metrics tested (contrast, d{sup ′}, and the level of artifacts) both for the uniform phantom case and in the presence of anatomical structure.Conclusions: The paired projection normalization provides better performance in the image quality of the reconstructed slices, and results in a lower level of artifacts in the Z direction. This implies that even a relatively
Height reconstruction techniques for synthetic aperture lidar systems
NASA Technical Reports Server (NTRS)
Chen, Curtis W.; Hensley, Scott
2003-01-01
The data-processing techniques and acquisition modes of a synthetic aperture lidar (SAL) instrument operating at optical wavelengths are closely related to the analogous modes of a synthetic aperture radar (SAR) instrument operating at microwave frequencies. It is consequently natural to explore the applicability of SAR processing techniques to SAL sensors. In this paper, we examine the feasibility of adopting SAR height-reconstruction techniques with SAL sensors to obtain high-resolution 3-D imagery at optical wavelengths.
Allidina, A.Y.; Malinowski, K.; Singh, M.G.
1982-12-01
The possibilities were explored for enhancing parallelism in the simulation of systems described by algebraic equations, ordinary differential equations and partial differential equations. These techniques, using multiprocessors, were developed to speed up simulations, e.g. for nuclear accidents. Issues involved in their design included suitable approximations to bring the problem into a numerically manageable form and a numerical procedure to perform the computations necessary to solve the problem accurately. Parallel processing techniques used as simulation procedures, and a design of a simulation scheme and simulation procedure employing parallel computer facilities, were both considered.
Reconstruction Techniques for Sparse Multistatic Linear Array Microwave Imaging
Sheen, David M.; Hall, Thomas E.
2014-06-09
Sequentially-switched linear arrays are an enabling technology for a number of near-field microwave imaging applications. Electronically sequencing along the array axis followed by mechanical scanning along an orthogonal axis allows dense sampling of a two-dimensional aperture in near real-time. In this paper, a sparse multi-static array technique will be described along with associated Fourier-Transform-based and back-projection-based image reconstruction algorithms. Simulated and measured imaging results are presented that show the effectiveness of the sparse array technique along with the merits and weaknesses of each image reconstruction approach.
Minimally Invasive Techniques for Total Aortic Arch Reconstruction
Faulds, Jason; Sandhu, Harleen K.; Estrera, Anthony L.; Safi, Hazim J.
2016-01-01
The cumulative experience with endovascular aortic repair in the descending thoracic and infrarenal aorta has led to increased interest in endovascular aortic arch reconstruction. Open total arch replacement is a robust operation that can be performed with excellent results. However, it requires cardiopulmonary bypass and circulatory arrest and, therefore, may not be tolerated by all patients. Minimally invasive techniques have been considered as an alternative and include hybrid arch debranching, parallel stent graft deployment in the chimney and snorkel configurations, and complete endovascular branched reconstruction with multi-branched devices. This review discusses the evolving use of endovascular techniques in the management of aortic arch pathology and considers their relevance in an era of safe and durable open aortic arch reconstruction. PMID:27127562
Minimally Invasive Techniques for Total Aortic Arch Reconstruction.
Faulds, Jason; Sandhu, Harleen K; Estrera, Anthony L; Safi, Hazim J
2016-01-01
The cumulative experience with endovascular aortic repair in the descending thoracic and infrarenal aorta has led to increased interest in endovascular aortic arch reconstruction. Open total arch replacement is a robust operation that can be performed with excellent results. However, it requires cardiopulmonary bypass and circulatory arrest and, therefore, may not be tolerated by all patients. Minimally invasive techniques have been considered as an alternative and include hybrid arch debranching, parallel stent graft deployment in the chimney and snorkel configurations, and complete endovascular branched reconstruction with multi-branched devices. This review discusses the evolving use of endovascular techniques in the management of aortic arch pathology and considers their relevance in an era of safe and durable open aortic arch reconstruction. PMID:27127562
Benhammouda, Brahim
2016-01-01
Since 1980, the Adomian decomposition method (ADM) has been extensively used as a simple powerful tool that applies directly to solve different kinds of nonlinear equations including functional, differential, integro-differential and algebraic equations. However, for differential-algebraic equations (DAEs) the ADM is applied only in four earlier works. There, the DAEs are first pre-processed by some transformations like index reductions before applying the ADM. The drawback of such transformations is that they can involve complex algorithms, can be computationally expensive and may lead to non-physical solutions. The purpose of this paper is to propose a novel technique that applies the ADM directly to solve a class of nonlinear higher-index Hessenberg DAEs systems efficiently. The main advantage of this technique is that; firstly it avoids complex transformations like index reductions and leads to a simple general algorithm. Secondly, it reduces the computational work by solving only linear algebraic systems with a constant coefficient matrix at each iteration, except for the first iteration where the algebraic system is nonlinear (if the DAE is nonlinear with respect to the algebraic variable). To demonstrate the effectiveness of the proposed technique, we apply it to a nonlinear index-three Hessenberg DAEs system with nonlinear algebraic constraints. This technique is straightforward and can be programmed in Maple or Mathematica to simulate real application problems. PMID:27330880
NASA Astrophysics Data System (ADS)
Moinul Hossain, Md; Lu, Gang; Sun, Duo; Yan, Yong
2013-07-01
This paper presents an experimental investigation, visualization and validation in the three-dimensional (3D) reconstruction of flame temperature and emissivity distributions by using optical tomographic and two-colour pyrometric techniques. A multi-camera digital imaging system comprising eight optical imaging fibres and two RGB charged-couple device (CCD) cameras are used to acquire two-dimensional (2D) images of the flame simultaneously from eight equiangular directions. A combined logical filtered back-projection (LFBP) and simultaneous iterative reconstruction and algebraic reconstruction technique (SART) algorithm is utilized to reconstruct the grey-level intensity of the flame for the two primary colour (red and green) images. The temperature distribution of the flame is then determined from the ratio of the reconstructed grey-level intensities and the emissivity is estimated from the ratio of the grey level of a primary colour image to that of a blackbody source at the same temperature. The temperature measurement of the system was calibrated using a blackbody furnace as a standard temperature source. Experimental work was undertaken to validate the flame temperature obtained by the imaging system against that obtained using high-precision thermocouples. The difference between the two measurements is found no greater than ±9%. Experimental results obtained on a laboratory-scale propane fired combustion test rig demonstrate that the imaging system and applied technical approach perform well in the reconstruction of the 3D temperature and emissivity distributions of the sooty flame.
An algebraic grid generation technique for multi body launch vehicle configurations
Balu, R.; Unnikrishnan, C.
1996-12-31
A simple algebraic grid generation method is used to generate three dimensional computational grids over multi body launch vehicle configurations. Sample grids for various configurations like, axisymmetric bodies with fins and multi body launch vehicles having a number of strap-on boosters, are presented. These grids appear to be of comparative quality to those generated by sophisticated techniques like Poisson`s equation solutions, which take enormous computing times. Viscous flow simulations using the present grids are found to be quite satisfactory for practical purposes.
Reconstruction of reflectance data using an interpolation technique.
Abed, Farhad Moghareh; Amirshahi, Seyed Hossein; Abed, Mohammad Reza Moghareh
2009-03-01
A linear interpolation method is applied for reconstruction of reflectance spectra of Munsell as well as ColorChecker SG color chips from the corresponding colorimetric values under a given set of viewing conditions. Hence, different types of lookup tables (LUTs) have been created to connect the colorimetric and spectrophotometeric data as the source and destination spaces in this approach. To optimize the algorithm, different color spaces and light sources have been used to build different types of LUTs. The effects of applied color datasets as well as employed color spaces are investigated. Results of recovery are evaluated by the mean and the maximum color difference values under other sets of standard light sources. The mean and the maximum values of root mean square (RMS) error between the reconstructed and the actual spectra are also calculated. Since the speed of reflectance reconstruction is a key point in the LUT algorithm, the processing time spent for interpolation of spectral data has also been measured for each model. Finally, the performance of the suggested interpolation technique is compared with that of the common principal component analysis method. According to the results, using the CIEXYZ tristimulus values as a source space shows priority over the CIELAB color space. Besides, the colorimetric position of a desired sample is a key point that indicates the success of the approach. In fact, because of the nature of the interpolation technique, the colorimetric position of the desired samples should be located inside the color gamut of available samples in the dataset. The resultant spectra that have been reconstructed by this technique show considerable improvement in terms of RMS error between the actual and the reconstructed reflectance spectra as well as CIELAB color differences under the other light source in comparison with those obtained from the standard PCA technique. PMID:19252659
Reconstruction of transoral robotic surgery defects: principles and techniques.
de Almeida, John Rukshan; Park, Richard Chan Woo; Genden, Eric M
2012-09-01
Early functional and oncological outcome studies suggest that transoral robotic surgery (TORS) may have a role for early stage cancers of the oropharynx. Unlike with traditional mandibular swing or pharyngotomy approaches, access to the oropharynx for reconstruction in TORS cases is limited. Maintaining a good functional result necessitates preserving physiological function where possible. The principles that should guide reconstructive surgeons include maintaining a velopharyngeal sphincter to prevent velopharyngeal insufficiency, maintaining sensate mucosa and restoring bulk in the tongue base to prevent aspiration, maintaining separation between the cervical and pharyngeal components, and covering exposed vessels in the pharynx. We present here principles and surgical techniques of TORS to reconstruct oropharyngeal defects using a subsite-based approach using secondary healing, local musculomucosal flaps, and free tissue transfer guided by the above principles. PMID:22744899
A novel technique for hepatic vein reconstruction during hepatectomy.
Surjan, Rodrigo C; Basseres, Tiago; Pajecki, Denis; Puzzo, Daniel B; Makdissi, Fabio F; Machado, Marcel A C; Battilana, Alexandre Gustavo Bellorio
2016-01-01
Surgical resection is the treatment of choice for malignant liver tumours. Nevertheless, surgical approach to tumours located close to the confluence of the hepatic veins is a challenging issue. Trisectionectomies are considered the first curative option for treatment of these tumours. However, those procedures are associated with high morbidity and mortality rates primarily due to post-operative liver failure. Thus, maximal preservation of functional liver parenchyma should always be attempted. We describe the isolated resection of Segment 8 for the treatment of a tumour involving the right hepatic vein and in contact with the middle hepatic vein and retrohepatic vena cava with immediate reconstruction of the right hepatic vein with a vascular graft. This is the first time this type of reconstruction was performed, and it allowed to preserve all but one of the hepatic segments with normal venous outflow. This innovative technique is a fast and safe method to reconstruct hepatic veins. PMID:27076622
A novel technique for hepatic vein reconstruction during hepatectomy
Surjan, Rodrigo C.; Basseres, Tiago; Pajecki, Denis; Puzzo, Daniel B.; Makdissi, Fabio F.; Machado, Marcel A.C.; Battilana, Alexandre Gustavo Bellorio
2016-01-01
Surgical resection is the treatment of choice for malignant liver tumours. Nevertheless, surgical approach to tumours located close to the confluence of the hepatic veins is a challenging issue. Trisectionectomies are considered the first curative option for treatment of these tumours. However, those procedures are associated with high morbidity and mortality rates primarily due to post-operative liver failure. Thus, maximal preservation of functional liver parenchyma should always be attempted. We describe the isolated resection of Segment 8 for the treatment of a tumour involving the right hepatic vein and in contact with the middle hepatic vein and retrohepatic vena cava with immediate reconstruction of the right hepatic vein with a vascular graft. This is the first time this type of reconstruction was performed, and it allowed to preserve all but one of the hepatic segments with normal venous outflow. This innovative technique is a fast and safe method to reconstruct hepatic veins. PMID:27076622
Reconstruction techniques for sparse multistatic linear array microwave imaging
NASA Astrophysics Data System (ADS)
Sheen, David M.; Hall, Thomas E.
2014-06-01
Sequentially-switched linear arrays are an enabling technology for a number of near-field microwave imaging applications. Electronically sequencing along the array axis followed by mechanical scanning along an orthogonal axis allows dense sampling of a two-dimensional aperture in near real-time. The Pacific Northwest National Laboratory (PNNL) has developed this technology for several applications including concealed weapon detection, groundpenetrating radar, and non-destructive inspection and evaluation. These techniques form three-dimensional images by scanning a diverging beam swept frequency transceiver over a two-dimensional aperture and mathematically focusing or reconstructing the data into three-dimensional images. Recently, a sparse multi-static array technology has been developed that reduces the number of antennas required to densely sample the linear array axis of the spatial aperture. This allows a significant reduction in cost and complexity of the linear-array-based imaging system. The sparse array has been specifically designed to be compatible with Fourier-Transform-based image reconstruction techniques; however, there are limitations to the use of these techniques, especially for extreme near-field operation. In the extreme near-field of the array, back-projection techniques have been developed that account for the exact location of each transmitter and receiver in the linear array and the 3-D image location. In this paper, the sparse array technique will be described along with associated Fourier-Transform-based and back-projection-based image reconstruction algorithms. Simulated imaging results are presented that show the effectiveness of the sparse array technique along with the merits and weaknesses of each image reconstruction approach.
Evaluation of the spline reconstruction technique for PET
Kastis, George A. Kyriakopoulou, Dimitra; Gaitanis, Anastasios; Fernández, Yolanda; Hutton, Brian F.; Fokas, Athanasios S.
2014-04-15
Purpose: The spline reconstruction technique (SRT), based on the analytic formula for the inverse Radon transform, has been presented earlier in the literature. In this study, the authors present an improved formulation and numerical implementation of this algorithm and evaluate it in comparison to filtered backprojection (FBP). Methods: The SRT is based on the numerical evaluation of the Hilbert transform of the sinogram via an approximation in terms of “custom made” cubic splines. By restricting reconstruction only within object pixels and by utilizing certain mathematical symmetries, the authors achieve a reconstruction time comparable to that of FBP. The authors have implemented SRT in STIR and have evaluated this technique using simulated data from a clinical positron emission tomography (PET) system, as well as real data obtained from clinical and preclinical PET scanners. For the simulation studies, the authors have simulated sinograms of a point-source and three digital phantoms. Using these sinograms, the authors have created realizations of Poisson noise at five noise levels. In addition to visual comparisons of the reconstructed images, the authors have determined contrast and bias for different regions of the phantoms as a function of noise level. For the real-data studies, sinograms of an{sup 18}F-FDG injected mouse, a NEMA NU 4-2008 image quality phantom, and a Derenzo phantom have been acquired from a commercial PET system. The authors have determined: (a) coefficient of variations (COV) and contrast from the NEMA phantom, (b) contrast for the various sections of the Derenzo phantom, and (c) line profiles for the Derenzo phantom. Furthermore, the authors have acquired sinograms from a whole-body PET scan of an {sup 18}F-FDG injected cancer patient, using the GE Discovery ST PET/CT system. SRT and FBP reconstructions of the thorax have been visually evaluated. Results: The results indicate an improvement in FWHM and FWTM in both simulated and real
The anatomic coracoclavicular ligament reconstruction: surgical technique and indications.
Carofino, Brad C; Mazzocca, Augustus D
2010-03-01
The anatomic coracoclavicular ligament reconstruction (ACCR) is a surgical procedure to address acriomioclavicular joint instability. The coracoclavicular ligaments are reconstructed using a semitendinosus allograft passed beneath the coracoid and through bone tunnels in the clavicle. The graft is secured with interference screw fixation, and the acromioclavicular joint is retained. Here we describe the authors' surgical technique, indications, and rehabilitation protocol. Also, a preliminary case series of seventeen patients is presented. Patients demonstrated significant improvement in pain levels and function. The mean ASES score increased from 52 preoperatively to 92. The Constant Murley rose from 66.6 to 94.7. There were three failures in this series, and two required revision surgery. PMID:20188267
NASA Astrophysics Data System (ADS)
Do, Synho; Liang, Zhuangli; Karl, William Clem; Brady, Thomas; Pien, Homer
2008-03-01
Modern CT systems have advanced at a dramatic rate. Algebraic iterative reconstruction techniques have shown promising and desirable image characteristics, but are seldom used due to their high computational cost for complete reconstruction of large volumetric datasets. In many cases, however, interest in high resolution reconstructions is restricted to smaller regions of interest within the complete volume. In this paper we present an implementation of a simple and practical method to produce iterative reconstructions of reduced-sized ROI from 3D helical tomographic data. We use the observation that the conventional filtered back-projection reconstruction is generally of high quality throughout the entire volume to predict the contributions to ROI-related projections arising from volumes outside the ROI. These predictions are then used to pre-correct the data to produce a tomographic inversion problem of substantially reduced size and memory demands. Our work expands on those of other researchers who have observed similar potential computational gains by exploiting FBP results. We demonstrate our approach using cardiac CT cone-beam imaging, illustrating our results with both ex vivo and in vivo multi-cycle EKG-gated examples.
Basket-Weave Technique for Medial Patellofemoral Ligament Reconstruction.
Kodkani, Pranjal S
2015-06-01
The anatomy of the medial patellofemoral ligament (MPFL) has been well defined, with parts of its uppermost fibers having a soft-tissue insertion onto the vastus intermedius. Bone tunnels and implants on the patellar side therefore cannot replicate this anatomic construct precisely. Because of implants and tunnels, complications have been reported with bone tunnel fracture. Similarly, on the femoral side, rigid fixation with implants can result in over-constraint with compromised results. Moreover, bone tunnels cannot be used in skeletally immature cases. To overcome issues related to bone tunneling and implants, as well as to reconstruct the MPFL in a precise anatomic manner, an all-soft-tissue fixation technique was devised. Bony landmarks were used as reference points instead of radiologic markers to achieve a more precise construct and to eliminate intraoperative radiography. Hamstring graft was used to reconstruct the MPFL. Special suturing techniques were used to achieve optimal graft fixation with minimal suture knots. A special tissue elevator-suture passer device was designed to facilitate graft passage and ease in performing the procedure. This technique permits differential tensioning, and therefore one achieves stability throughout the range of motion. PMID:26258044
Performance validation of phase diversity image reconstruction techniques
NASA Astrophysics Data System (ADS)
Hirzberger, J.; Feller, A.; Riethmüller, T. L.; Gandorfer, A.; Solanki, S. K.
2011-05-01
We present a performance study of a phase diversity (PD) image reconstruction algorithm based on artificial solar images obtained from MHD simulations and on seeing-free data obtained with the SuFI instrument on the Sunrise balloon borne observatory. The artificial data were altered by applying different levels of degradation with synthesised wavefront errors and noise. The PD algorithm was modified by changing the number of fitted polynomials, the shape of the pupil and the applied noise filter. The obtained reconstructions are evaluated by means of the resulting rms intensity contrast and by the conspicuousness of appearing artifacts. The results show that PD is a robust method which consistently recovers the initial unaffected image contents. The efficiency of the reconstruction is, however, strongly dependent on the number of used fitting polynomials and the noise level of the images. If the maximum number of fitted polynomials is higher than 21, artifacts have to be accepted and for noise levels higher than 10-3 the commonly used noise filtering techniques are not able to avoid amplification of spurious structures.
Fast Multigrid Techniques in Total Variation-Based Image Reconstruction
NASA Technical Reports Server (NTRS)
Oman, Mary Ellen
1996-01-01
Existing multigrid techniques are used to effect an efficient method for reconstructing an image from noisy, blurred data. Total Variation minimization yields a nonlinear integro-differential equation which, when discretized using cell-centered finite differences, yields a full matrix equation. A fixed point iteration is applied with the intermediate matrix equations solved via a preconditioned conjugate gradient method which utilizes multi-level quadrature (due to Brandt and Lubrecht) to apply the integral operator and a multigrid scheme (due to Ewing and Shen) to invert the differential operator. With effective preconditioning, the method presented seems to require Omicron(n) operations. Numerical results are given for a two-dimensional example.
Image reconstruction techniques applied to nuclear mass models
NASA Astrophysics Data System (ADS)
Morales, Irving O.; Isacker, P. Van; Velazquez, V.; Barea, J.; Mendoza-Temis, J.; Vieyra, J. C. López; Hirsch, J. G.; Frank, A.
2010-02-01
A new procedure is presented that combines well-known nuclear models with image reconstruction techniques. A color-coded image is built by taking the differences between measured masses and the predictions given by the different theoretical models. This image is viewed as part of a larger array in the (N,Z) plane, where unknown nuclear masses are hidden, covered by a “mask.” We apply a suitably adapted deconvolution algorithm, used in astronomical observations, to “open the window” and see the rest of the pattern. We show that it is possible to improve significantly mass predictions in regions not too far from measured nuclear masses.
The use of prefabrication technique in microvascular reconstructive surgery
Maciejewski, Adam; Szymczyk, Cezary; Wierzgoń, Janusz; Szumniak, Ryszard; Jędrzejewski, Piotr; Grajek, Maciej; Dobrut, Mirosław; Ulczok, Rafał; Półtorak, Stanisław
2013-01-01
Aim of the study The aim of the study was to develop standards for the prefabrication of free microvascular flaps in an animal model, followed by their application in clinical practice, and quantitative/qualitative microscopic assessment of the extent of development of a new microvascular network. Material and methods The study was carried out in 10 experimental pigs. As the first stage, a total of 20 prefabricated flaps were created using polytetrafluoroethylene (PTFE) as a support material, placed horizontally over an isolated and distally closed vascular pedicle based on superficial abdominal vessels. After completing the animal model study, one patient was selected for the grafting of the prefabricated free flap. Results All 20 free flaps prefabricated in the animal model were analyzed microscopically, exhibiting connective tissue rich in fibroblasts and small blood vessels in the porous areas across the entire thickness of the PTFE element. Conclusions Flap prefabrication is a new and fast developing reconstruction technique. The usefulness of prefabrication techniques and their status in reconstructive surgery still needs to be investigated experimentally and clinically. The method based on prefabricated free flaps is the first step towards anatomical bioengineering that will make it possible to replace missing organs with their anatomically perfect equivalents. PMID:23788942
Air data position-error calibration using state reconstruction techniques
NASA Technical Reports Server (NTRS)
Whitmore, S. A.; Larson, T. J.; Ehernberger, L. J.
1984-01-01
During the highly maneuverable aircraft technology (HiMAT) flight test program recently completed at NASA Ames Research Center's Dryden Flight Research Facility, numerous problems were experienced in airspeed calibration. This necessitated the use of state reconstruction techniques to arrive at a position-error calibration. For the HiMAT aircraft, most of the calibration effort was expended on flights in which the air data pressure transducers were not performing accurately. Following discovery of this problem, the air data transducers of both aircraft were wrapped in heater blankets to correct the problem. Additional calibration flights were performed, and from the resulting data a satisfactory position-error calibration was obtained. This calibration and data obtained before installation of the heater blankets were used to develop an alternate calibration method. The alternate approach took advantage of high-quality inertial data that was readily available. A linearized Kalman filter (LKF) was used to reconstruct the aircraft's wind-relative trajectory; the trajectory was then used to separate transducer measurement errors from the aircraft position error. This calibration method is accurate and inexpensive. The LKF technique has an inherent advantage of requiring that no flight maneuvers be specially designed for airspeed calibrations. It is of particular use when the measurements of the wind-relative quantities are suspected to have transducer-related errors.
Yin Fangfang; Guan Huaiqun; Lu Wenkai
2005-09-15
The technologies with kilovoltage (kV) and megavoltage (MV) imaging in the treatment room are now available for image-guided radiation therapy to improve patient setup and target localization accuracy. However, development of strategies to efficiently and effectively implement these technologies for patient treatment remains challenging. This study proposed an aggregated technique for on-board CT reconstruction using combination of kV and MV beam projections to improve the data acquisition efficiency and image quality. These projections were acquired in the treatment room at the patient treatment position with a new kV imaging device installed on the accelerator gantry, orthogonal to the existing MV portal imaging device. The projection images for a head phantom and a contrast phantom were acquired using both the On-Board Imager{sup TM} kV imaging device and the MV portal imager mounted orthogonally on the gantry of a Varian Clinac{sup TM} 21EX linear accelerator. MV projections were converted into kV information prior to the aggregated CT reconstruction. The multilevel scheme algebraic-reconstruction technique was used to reconstruct CT images involving either full, truncated, or a combination of both full and truncated projections. An adaptive reconstruction method was also applied, based on the limited numbers of kV projections and truncated MV projections, to enhance the anatomical information around the treatment volume and to minimize the radiation dose. The effects of the total number of projections, the combination of kV and MV projections, and the beam truncation of MV projections on the details of reconstructed kV/MV CT images were also investigated.
ERIC Educational Resources Information Center
Kieran, Carolyn; Drijvers, Paul
2006-01-01
This paper addresses the dialectical relation between theoretical thinking and technique, as they co-emerge in a combined computer algebra (CAS) and paper-and-pencil environment. The theoretical framework in this ongoing study consists of the instrumental approach to tool use and an adaptation of Chevallard's anthropological theory. The main aim…
Novel techniques and the future of skull base reconstruction.
Meier, Joshua C; Bleier, Benjamin S
2013-01-01
The field of endoscopic skull base surgery has evolved considerably in recent years fueled largely by advances in both imaging and instrumentation. While the indications for these approaches continue to be extended, the ability to reconstruct the resultant defects has emerged as a rate-limiting obstacle. Postoperative failures with current multilayer grafting techniques remain significant and may increase as the indications for endoscopic resections continue to expand. Laser tissue welding represents a novel method of wound repair in which laser energy is applied to a chromophore doped biologic solder at the wound edge to create a laser weld (fig. 1). These repairs are capable of withstanding forces far exceeding those exerted by intracranial pressure with negligible collateral thermal tissue injury. Recent clinical trials have demonstrated the safety and feasibility of endoscopic laser welding while exposing the limitations of first generation hyaluronic acid based solders. Novel supersaturated gel based solders are currently being tested in clinical trials and appear to possess significantly improved viscoelastic properties. While laser tissue welding remains an experimental technique, continued success with these novel solder formulations may catalyze the widespread adoption of this technique for skull base repair in the near future. PMID:23257563
Singh, Vivek Ajit; Elbahri, Hassan; Shanmugam, Rukmanikanthan
2016-01-01
Background. Periacetabular resections with reconstruction has high rates of complications due to the complexity of the reconstruction. We have improvised a novel technique of reconstruction for type II and type II + III pelvic resections with the use of a commercially available acetabulum reconstruction cage (gap II, Stryker) and threaded rods. Objectives. The aim of our study is to determine the biomechanical strength of our reconstruction compared to the traditional cemented total hip replacement (THR) designs in normal acetabulum and establish its mode of failure. Methods. Five sets of hemipelvises were biomechanically tested (Instron® 3848, MA, USA). These constructs were subjected to cyclic loading and load to failure. Results. The reconstructed acetabulum was stiffer and required a higher load to failure compared to the intact pelvis with a standard THR. The mean stiffness of the reconstructed pelvis was 1738.6 ± 200.3 Nmm−1 compared to the intact pelvis, which was 911.4 ± 172.7 Nmm−1 (P value = 0.01). The mean load to failure for the standard acetabular cup construct was 3297.3 ± 117.7 N while that of the reconstructed pelvis with the acetabulum cage and threaded rods was 4863.8 ± 7.0 N. Conclusion. Reconstruction of the pelvis with an acetabular reconstruction cage and threaded rods is a biomechanical viable option. PMID:27340368
Singh, Vivek Ajit; Elbahri, Hassan; Shanmugam, Rukmanikanthan
2016-01-01
Background. Periacetabular resections with reconstruction has high rates of complications due to the complexity of the reconstruction. We have improvised a novel technique of reconstruction for type II and type II + III pelvic resections with the use of a commercially available acetabulum reconstruction cage (gap II, Stryker) and threaded rods. Objectives. The aim of our study is to determine the biomechanical strength of our reconstruction compared to the traditional cemented total hip replacement (THR) designs in normal acetabulum and establish its mode of failure. Methods. Five sets of hemipelvises were biomechanically tested (Instron® 3848, MA, USA). These constructs were subjected to cyclic loading and load to failure. Results. The reconstructed acetabulum was stiffer and required a higher load to failure compared to the intact pelvis with a standard THR. The mean stiffness of the reconstructed pelvis was 1738.6 ± 200.3 Nmm(-1) compared to the intact pelvis, which was 911.4 ± 172.7 Nmm(-1) (P value = 0.01). The mean load to failure for the standard acetabular cup construct was 3297.3 ± 117.7 N while that of the reconstructed pelvis with the acetabulum cage and threaded rods was 4863.8 ± 7.0 N. Conclusion. Reconstruction of the pelvis with an acetabular reconstruction cage and threaded rods is a biomechanical viable option. PMID:27340368
A review of reconstruction techniques for capacitance tomography
NASA Astrophysics Data System (ADS)
Isaksen, Øyvind
1996-03-01
Capacitance tomography has been used to image several processes, such as liquid/gas pipe flow, oil/water/gas gravity separation, pneumatic conveying, fluidized beds and flame combustion. The nature of the capacitance sensors is such that reconstruction algorithms well developed for medical tomography are not applicable. The main problem is that the relationship between the measured quantity (capacitance) and the parameter of interest (distribution of the dielectric constant) is nonlinear. Furthermore, it is impossible to establish an explicit expression which relates the dielectric constant distribution to the measured capacitance. Also it should be pointed out that the number of measurements in capacitance tomography is small (typically less than 100) compared to medical tomography. For these reasons the first tested algorithm in capacitance tomography was based on the crude back projection algorithm. This algorithm has over the years been enhanced for use with a capacitance tomograph. In addition other techniques, such as various iterative methods, algorithms based on artificial neural networks and `look-up' tables have been developed and tested. This paper outlines the working principles for the different techniques and presents the main results.
Ternary Virasoro - Witt algebra.
Zachos, C.; Curtright, T.; Fairlie, D.; High Energy Physics; Univ. of Miami; Univ. of Durham
2008-01-01
A 3-bracket variant of the Virasoro-Witt algebra is constructed through the use of su(1,1) enveloping algebra techniques. The Leibniz rules for 3-brackets acting on other 3-brackets in the algebra are discussed and verified in various situations.
Cierniak, Robert; Lorent, Anna
2016-09-01
The main aim of this paper is to investigate properties of our originally formulated statistical model-based iterative approach applied to the image reconstruction from projections problem which are related to its conditioning, and, in this manner, to prove a superiority of this approach over ones recently used by other authors. The reconstruction algorithm based on this conception uses a maximum likelihood estimation with an objective adjusted to the probability distribution of measured signals obtained from an X-ray computed tomography system with parallel beam geometry. The analysis and experimental results presented here show that our analytical approach outperforms the referential algebraic methodology which is explored widely in the literature and exploited in various commercial implementations. PMID:27289536
Seo, Seung Suk; Kim, Do Hun; Park, Byung Yoon
2015-01-01
Popliteal artery compression rarely occurs after posterior cruciate ligament (PCL) reconstruction using the tibial inlay technique that allows for direct visualization of the surgical field. However, we experienced a popliteal artery compression after PCL reconstruction performed using the technique, which eventually required re-operation. Here, we report this rare case and discuss reasons of popliteal artery compression. PMID:26673356
A modified surgical technique for reconstruction of an acute acromioclavicular joint dislocation
Marchie, Anthony; Kumar, Arun; Catre, Melanio
2009-01-01
We report a modified surgical technique for reconstruction of coracoclavicular and acromioclavicular ligaments after acute dislocation of acromioclavicular joint using suture anchors. We have repaired 3 consecutive type III acromioclavicular dislocations with good results. This technique is simple and safe and allows anatomical reconstruction of the ligaments in acute dislocations. PMID:20671868
A nonlinear image reconstruction technique for ECT using a combined neural network approach
NASA Astrophysics Data System (ADS)
Marashdeh, Q.; Warsito, W.; Fan, L.-S.; Teixeira, F. L.
2006-08-01
A combined multilayer feed-forward neural network (MLFF-NN) and analogue Hopfield network is developed for nonlinear image reconstruction of electrical capacitance tomography (ECT). The (nonlinear) forward problem in ECT is solved using the MLFF-NN trained with a set of capacitance data from measurements based on a back-propagation training algorithm with regularization. The inverse problem is solved using an analogue Hopfield network based on a neural-network multi-criteria optimization image reconstruction technique (HN-MOIRT). The nonlinear image reconstruction based on this combined MLFF-NN + HN-MOIRT approach is tested on measured capacitance data not used in training to reconstruct the permittivity distribution. The performance of the technique is compared against commonly used linear Landweber and semi-linear image reconstruction techniques, showing superiority in terms of both stability and quality of reconstructed images.
Iterative image reconstruction techniques: cardiothoracic computed tomography applications.
Cho, Young Jun; Schoepf, U Joseph; Silverman, Justin R; Krazinski, Aleksander W; Canstein, Christian; Deak, Zsuzsanna; Grimm, Jochen; Geyer, Lucas L
2014-07-01
Iterative image reconstruction algorithms provide significant improvements over traditional filtered back projection in computed tomography (CT). Clinically available through recent advances in modern CT technology, iterative reconstruction enhances image quality through cyclical image calculation, suppressing image noise and artifacts, particularly blooming artifacts. The advantages of iterative reconstruction are apparent in traditionally challenging cases-for example, in obese patients, those with significant artery calcification, or those with coronary artery stents. In addition, as clinical use of CT has grown, so have concerns over ionizing radiation associated with CT examinations. Through noise reduction, iterative reconstruction has been shown to permit radiation dose reduction while preserving diagnostic image quality. This approach is becoming increasingly attractive as the routine use of CT for pediatric and repeated follow-up evaluation grows ever more common. Cardiovascular CT in particular, with its focus on detailed structural and functional analyses, stands to benefit greatly from the promising iterative solutions that are readily available. PMID:24662334
Kang, Yan; Yao, Yin-Ping; Kang, Zhi-Hua; Ma, Lin; Zhang, Tong-Yi
2015-06-01
We present different signal reconstruction techniques for implementation of compressive ghost imaging (CGI). The different techniques are validated on the data collected from ghost imaging with the pseudothermal light experimental system. Experiment results show that the technique based on total variance minimization gives high-quality reconstruction of the imaging object with less time consumption. The different performances among these reconstruction techniques and their parameter settings are also analyzed. The conclusion thus offers valuable information to promote the implementation of CGI in real applications. PMID:26367039
Yang, Alice C; Kretzler, Madison; Sudarski, Sonja; Gulani, Vikas; Seiberlich, Nicole
2016-06-01
The family of sparse reconstruction techniques, including the recently introduced compressed sensing framework, has been extensively explored to reduce scan times in magnetic resonance imaging (MRI). While there are many different methods that fall under the general umbrella of sparse reconstructions, they all rely on the idea that a priori information about the sparsity of MR images can be used to reconstruct full images from undersampled data. This review describes the basic ideas behind sparse reconstruction techniques, how they could be applied to improve MRI, and the open challenges to their general adoption in a clinical setting. The fundamental principles underlying different classes of sparse reconstructions techniques are examined, and the requirements that each make on the undersampled data outlined. Applications that could potentially benefit from the accelerations that sparse reconstructions could provide are described, and clinical studies using sparse reconstructions reviewed. Lastly, technical and clinical challenges to widespread implementation of sparse reconstruction techniques, including optimization, reconstruction times, artifact appearance, and comparison with current gold standards, are discussed. PMID:27003227
On N = 2 compactifications of M-theory to AdS{sub 3} using geometric algebra techniques
Babalic, E. M.; Coman, I. A.; Condeescu, C.; Micu, A.; Lazaroiu, C. I.
2013-11-13
We investigate the most general warped compactification of eleven-dimensional supergravity on eight-dimensional manifolds to AdS{sub 3} spaces (in the presence of non-vanishing four-form flux) which preserves N = 2 supersymmetry in three dimensions. Without imposing any restrictions on the chirality of the internal part of the supersymmetry generators, we use geometric algebra techniques to study some implications of the supersymmetry constraints. In particular, we discuss the Lie bracket of certain vector fields constructed as pinor bilinears on the compactification manifold.
Fatigue loading history reconstruction based on the rainflow technique
NASA Technical Reports Server (NTRS)
Khosrovaneh, A. K.; Dowling, N. E.
1990-01-01
Methods are considered of reducing a non-random fatigue loading history to a concise description and then of reconstructing a time history similar to the original. In particular, three methods of reconstruction based on a rainflow cycle counting matrix are presented. A rainflow matrix consists of the numbers of cycles at various peak and valley combinations. Two methods are based on a two-dimensional rainflow matrix, and the third on a three-dimensional rainflow matrix. Histories reconstructed by any of these methods produce a rainflow matrix identical to that of the original history, and the resulting time history is expected to produce a fatigue life similar to that for the original. The procedures described allow lengthy loading histories to be stored in compact form.
Teaching Algebra without Algebra
ERIC Educational Resources Information Center
Kalman, Richard S.
2008-01-01
Algebra is, among other things, a shorthand way to express quantitative reasoning. This article illustrates ways for the classroom teacher to convert algebraic solutions to verbal problems into conversational solutions that can be understood by students in the lower grades. Three reasonably typical verbal problems that either appeared as or…
Reconstruction of the maxilla using a fibula graft and virtual planning techniques
Rude, Kristian; Thygesen, Torben H; Sørensen, Jens Ahm
2014-01-01
Summary Use of a vascularised free fibula flap has been a popular method of osseous reconstruction because of its adequate length and acceptance of dental implants. In this article we describe a case of maxillary reconstruction in which virtual planning techniques and rapid prototyping were used to insert a microvascular osteomyocutaneous fibula graft, Medpor implant, and immediate dental implants. PMID:24827656
Implementation of control point form of algebraic grid-generation technique
NASA Technical Reports Server (NTRS)
Choo, Yung K.; Miller, David P.; Reno, Charles J.
1991-01-01
The control point form (CPF) provides explicit control of physical grid shape and grid spacing through the movement of the control points. The control point array, called a control net, is a space grid type arrangement of locations in physical space with an index for each direction. As an algebraic method CPF is efficient and works well with interactive computer graphics. A family of menu-driven, interactive grid-generation computer codes (TURBO) is being developed by using CPF. Key features of TurboI (a TURBO member) are discussed and typical results are presented. TurboI runs on any IRIS 4D series workstation.
NASA Astrophysics Data System (ADS)
Hart, Vern Philip, II
A methodology is presented for creating tomographic reconstructions from various projection data, and the relevance of the results to applications in atmospheric science and biomedical imaging is analyzed. The fundamental differences between transform and iterative methods are described and the properties of the imaging configurations are addressed. The presented results are particularly suited for highly ill-conditioned inverse problems in which the imaging data are restricted as a result of poor angular coverage, limited detector arrays, or insufficient access to an imaging region. The class of reconstruction algorithms commonly used in sparse tomography, the algebraic reconstruction techniques, is presented, analyzed, and compared. These algorithms are iterative in nature and their accuracy depends significantly on the initialization of the algorithm, the so-called initial guess. A considerable amount of research was conducted into novel initialization techniques as a means of improving the accuracy. The main body of this paper is comprised of three smaller papers, which describe the application of the presented methods to atmospheric and medical imaging modalities. The first paper details the measurement of mesospheric airglow emissions at two camera sites operated by Utah State University. Reconstructions of vertical airglow emission profiles are presented, including three-dimensional models of the layer formed using a novel fanning technique. The second paper describes the application of the method to the imaging of polar mesospheric clouds (PMCs) by NASA's Aeronomy of Ice in the Mesosphere (AIM) satellite. The contrasting elements of straight-line and diffusive tomography are also discussed in the context of ill-conditioned imaging problems. A number of developing modalities in medical tomography use near infrared light, which interacts strongly with biological tissue and results in significant optical scattering. In order to perform tomography on the
Computer Program For Linear Algebra
NASA Technical Reports Server (NTRS)
Krogh, F. T.; Hanson, R. J.
1987-01-01
Collection of routines provided for basic vector operations. Basic Linear Algebra Subprogram (BLAS) library is collection from FORTRAN-callable routines for employing standard techniques to perform basic operations of numerical linear algebra.
Acoustic holography: Problems associated with construction and reconstruction techniques
NASA Technical Reports Server (NTRS)
Singh, J. J.
1978-01-01
The implications of the difference between the inspecting and interrogating radiations are discussed. For real-time, distortionless, sound viewing, it is recommended that infrared radiation of wavelength comparable to the inspecting sound waves be used. The infrared images can be viewed with (IR visible) converter phosphors. The real-time display of the visible image of the acoustically-inspected object at low sound levels such as are used in medical diagnosis is evaluated. In this connection attention is drawn to the need for a phosphor screen which is such that its optical transmission at any point is directly related to the incident electron beam intensity at that point. Such a screen, coupled with an acoustical camera, can enable instantaneous sound wave reconstruction.
Kanazawa, Takeharu; Sarukawa, Shunji; Fukushima, Hirofumi; Takeoda, Shoji; Kusaka, Gen; Ichimura, Keiichi
2011-01-01
Various techniques have been developed to reconstruct head and neck defects following surgery to restore function and cosmetics. Free tissue transfer using microvascular anastomosis has transformed surgical outcomes and the quality of life for head and neck cancer patients because this technique has made it possible for surgeons to perform more aggressive ablative surgery, but there is room for improvement to achieve a satisfactory survival rate. Reconstruction using the free tissue transfer technique is closely related to cardiovascular surgery because the anastomosis techniques used by head and neck surgeons are based on those of cardiovascular surgeons; thus, suggestions from cardiovascular surgeons might lead to further development of this field. The aim of this article is to present the recent general concepts of reconstruction procedures and our experiences of reconstructive surgeries of the oral cavity, mandible, maxilla, oropharynx and hypopharynx to help cardiovascular surgeons understand the reconstructions and share knowledge among themselves and with neck surgeons to develop future directions in head and neck reconstruction. PMID:23555452
NASA Astrophysics Data System (ADS)
Han, Kai-Feng; Zeng, Xin-Wu
2011-06-01
Based on the dual source cumulative rotation technique in the time-domain proposed by Zeng and MacBeth (1993), a new algebraic processing technique for extracting shear-wave splitting parameters from multi-component VSP data in frequency-dependent medium has been developed. By using this dual source cumulative rotation technique in the frequency-domain (DCTF), anisotropic parameters, including polarization direction of the shear-waves and timedelay between the fast and slow shear-waves, can be estimated for each frequency component in the frequency domain. It avoids the possible error which comes from using a narrow-band filter in the current commonly used method. By using synthetic seismograms, the feasibility and validity of the technique was tested and a comparison with the currently used method was also given. The results demonstrate that the shear-wave splitting parameters frequency dependence can be extracted directly from four-component seismic data using the DCTF. In the presence of larger scale fractures, substantial frequency dependence would be found in the seismic frequency range, which implies that dispersion would occur at seismic frequencies. Our study shows that shear-wave anisotropy decreases as frequency increases.
Chakraborty, Shubhankar; Roy Chaudhuri, Partha; Das, Prasanta Kr
2016-07-01
In this communication, a novel optical technique has been proposed for the reconstruction of the shape of a Taylor bubble using measurements from multiple arrays of optical sensors. The deviation of an optical beam passing through the bubble depends on the contour of bubble surface. A theoretical model of the deviation of a beam during the traverse of a Taylor bubble through it has been developed. Using this model and the time history of the deviation captured by the sensor array, the bubble shape has been reconstructed. The reconstruction has been performed using an inverse algorithm based on Bayesian inference technique and Markov chain Monte Carlo sampling algorithm. The reconstructed nose shape has been compared with the true shape, extracted through image processing of high speed images. Finally, an error analysis has been performed to pinpoint the sources of the errors. PMID:27475597
NASA Astrophysics Data System (ADS)
Chakraborty, Shubhankar; Roy Chaudhuri, Partha; Das, Prasanta Kr.
2016-07-01
In this communication, a novel optical technique has been proposed for the reconstruction of the shape of a Taylor bubble using measurements from multiple arrays of optical sensors. The deviation of an optical beam passing through the bubble depends on the contour of bubble surface. A theoretical model of the deviation of a beam during the traverse of a Taylor bubble through it has been developed. Using this model and the time history of the deviation captured by the sensor array, the bubble shape has been reconstructed. The reconstruction has been performed using an inverse algorithm based on Bayesian inference technique and Markov chain Monte Carlo sampling algorithm. The reconstructed nose shape has been compared with the true shape, extracted through image processing of high speed images. Finally, an error analysis has been performed to pinpoint the sources of the errors.
ERIC Educational Resources Information Center
Roland, Catherine B.
1993-01-01
Describes two memory-enhancing techniques, visualization and concrete reconstruction, that have been successful in counseling adult survivors of sexual abuse. Includes suggested implementations, case examples, and implications for incorporating memory techniques into counseling process. Describes various risk factors involved in using these…
Kiran, Kopuri Ravi; Srikanth, I Muni; Chinnusamy, Lenin; Deepti, K
2015-01-01
The medial patellofemoral ligament (MPFL) is the primary stabilizer of the patellofemoral joint; its reconstruction has been recommended in adults over the past decade after recurrent patellar instability. However, there has been no standardized technique for reconstruction, therefore, ideal graft and technique for reconstruction are yet undetermined. However, dynamic MPFL reconstruction studies claim to be superior to other procedures as it is more anatomical. This preliminary study aims at assessing the outcomes of MPFL reconstruction in a dynamic pattern using hamstring graft. We performed this procedure in four consecutive patients with chronic patellar instability following trauma. MPFL reconstruction was done with hamstring tendons detached distally and secured to patellar periosteum after being passed through a bony tunnel in the patella without an implant and using the medial collateral ligament as a pulley. In all 4 knees, the MPFL reconstruction was isolated and was not associated with any other realignment procedures. No recurrent episodes of dislocation or subluxation were reported at 24 months followup. PMID:26806970
Wilde, Frank; Cornelius, Carl-Peter; Schramm, Alexander
2014-01-01
We investigated the workflow of computer-assisted mandibular reconstruction that was performed with a patient-specific mandibular reconstruction plate fabricated with computer-aided design and computer-aided manufacturing (CAD/CAM) techniques and a fibula flap. We assessed the feasibility of this technique from virtual planning to the completion of surgery. Computed tomography (CT) scans of a cadaveric skull and fibula were obtained for the virtual simulation of mandibular resection and reconstruction using ProPlan CMF software (Materialise®/DePuy Synthes®). The virtual model of the reconstructed mandible provided the basis for the computer-aided design of a patient-specific reconstruction plate that was milled from titanium using a five-axis milling machine and CAM techniques. CAD/CAM techniques were used for producing resection guides for mandibular resection and cutting guides for harvesting a fibula flap. Mandibular reconstruction was simulated in a cadaveric wet laboratory. No problems were encountered during the procedure. The plate was fixed accurately to the residual bone without difficulty. The fibula segments were attached to the plate rapidly and reliably. The fusion of preoperative and postoperative CT datasets demonstrated high reconstruction precision. Computer-assisted mandibular reconstruction with CAD/CAM-fabricated patient-specific reconstruction plates appears to be a promising approach for mandibular reconstruction. Clinical trials are required to determine whether these promising results can be translated into successful practice and what further developments are needed. PMID:25045420
Wilde, Frank; Cornelius, Carl-Peter; Schramm, Alexander
2014-06-01
We investigated the workflow of computer-assisted mandibular reconstruction that was performed with a patient-specific mandibular reconstruction plate fabricated with computer-aided design and computer-aided manufacturing (CAD/CAM) techniques and a fibula flap. We assessed the feasibility of this technique from virtual planning to the completion of surgery. Computed tomography (CT) scans of a cadaveric skull and fibula were obtained for the virtual simulation of mandibular resection and reconstruction using ProPlan CMF software (Materialise(®)/DePuy Synthes(®)). The virtual model of the reconstructed mandible provided the basis for the computer-aided design of a patient-specific reconstruction plate that was milled from titanium using a five-axis milling machine and CAM techniques. CAD/CAM techniques were used for producing resection guides for mandibular resection and cutting guides for harvesting a fibula flap. Mandibular reconstruction was simulated in a cadaveric wet laboratory. No problems were encountered during the procedure. The plate was fixed accurately to the residual bone without difficulty. The fibula segments were attached to the plate rapidly and reliably. The fusion of preoperative and postoperative CT datasets demonstrated high reconstruction precision. Computer-assisted mandibular reconstruction with CAD/CAM-fabricated patient-specific reconstruction plates appears to be a promising approach for mandibular reconstruction. Clinical trials are required to determine whether these promising results can be translated into successful practice and what further developments are needed. PMID:25045420
2013-01-01
Background This study described a novel, minimally invasive reconstruction technique of lateral tibial plateau fractures using a three-screw jail technique and compared it to a conventional two-screw osteosynthesis technique. The benefit of an additional screw implanted in the proximal tibia from the anterior at an angle of 90° below the conventional two-screw reconstruction after lateral tibial plateau fracture was evaluated. This new method was called the jail technique. Methods The two reconstruction techniques were tested using a porcine model (n = 40). Fracture was simulated using a defined osteotomy of the lateral tibial plateau. Load-to-failure and multiple cyclic loading tests were conducted using a material testing machine. Twenty tibias were used for each reconstruction technique, ten of which were loaded in a load-to-failure protocol and ten cyclically loaded (5000 times) between 200 and 1000 N using a ramp protocol. Displacement, stiffness and yield load were determined from the resulting load displacement curve. Failure was macroscopically documented. Results In the load-to-failure testing, the jail technique showed a significantly higher mean maximum load (2275.9 N) in comparison to the conventional reconstruction (1796.5 N, p < 0.001). The trend for better outcomes for the novel technique in terms of stiffness and yield load did not reach statistical significance (p > 0.05). In cyclic testing, the jail technique also showed better trends in displacement that were not statistically significant. Failure modes showed a tendency of screws cutting through the bone (cut-out) in the conventional reconstruction. No cut-out but a bending of the lag screws at the site of the additional third screw was observed in the jail technique. Conclusions The results of this study indicate that the jail and the conventional technique have seemingly similar biomechanical properties. This suggests that the jail technique may be a feasible alternative to
A facial reconstruction and identification technique for seriously devastating head wounds.
Joukal, Marek; Frišhons, Jan
2015-07-01
Many authors have focused on facial identification techniques, and facial reconstructions for cases when skulls have been found are especially well known. However, a standardized facial identification technique for an unknown body with seriously devastating head injuries has not yet been developed. A reconstruction and identification technique was used in 7 cases of accidents involving trains striking pedestrians. This identification technique is based on the removal of skull bone fragments, subsequent fixation of soft tissue onto a universal commercial polystyrene head model, precise suture of dermatomuscular flaps, and definitive adjustment using cosmetic treatments. After reconstruction, identifying marks such as scars, eyebrows, facial lines, facial hair and partly hairstyle become evident. It is then possible to present a modified picture of the reconstructed face to relatives. After comparing the results with photos of the person before death, this technique has proven to be very useful for identifying unknown bodies when other identification techniques are not available. This technique is useful for its being rather quick and especially for its results. PMID:25965304
Current concept in dysplastic hip arthroplasty: Techniques for acetabular and femoral reconstruction
Bicanic, Goran; Barbaric, Katarina; Bohacek, Ivan; Aljinovic, Ana; Delimar, Domagoj
2014-01-01
Adult patients with developmental dysplasia of the hip develop secondary osteoarthritis and eventually end up with total hip arthroplasty (THA) at younger age. Because of altered anatomy of dysplastic hips, THA in these patients represents technically demanding procedure. Distorted anatomy of the acetabulum and proximal femur together with conjoined leg length discrepancy present major challenges during performing THA in patients with developmental dysplasia of the hip. In addition, most patients are at younger age, therefore, soft tissue balance is of great importance (especially the need to preserve the continuity of abductors) to maximise postoperative functional result. In this paper we present a variety of surgical techniques available for THA in dysplastic hips, their advantages and disadvantages. For acetabular reconstruction following techniques are described: Standard metal augments (prefabricated), Custom made acetabular augments (3D printing), Roof reconstruction with vascularized fibula, Roof reconstruction with pedicled iliac graft, Roof reconstruction with autologous bone graft, Roof reconstruction with homologous bone graft, Roof reconstruction with auto/homologous spongious bone, Reinforcement ring with the hook in combination with autologous graft augmentation, Cranial positioning of the acetabulum, Medial protrusion technique (cotyloplasty) with chisel, Medial protrusion technique (cotyloplasty) with reaming, Cotyloplasty without spongioplasty. For femoral reconstruction following techniques were described: Distraction with external fixator, Femoral shortening through a modified lateral approach, Transtrochanteric osteotomies, Paavilainen osteotomy, Lesser trochanter osteotomy, Double-chevron osteotomy, Subtrochanteric osteotomies, Diaphyseal osteotomies, Distal femoral osteotomies. At the end we present author’s treatment method of choice: for acetabulum we perform cotyloplasty leaving only paper-thin medial wall, which we break during
Bicanic, Goran; Barbaric, Katarina; Bohacek, Ivan; Aljinovic, Ana; Delimar, Domagoj
2014-09-18
Adult patients with developmental dysplasia of the hip develop secondary osteoarthritis and eventually end up with total hip arthroplasty (THA) at younger age. Because of altered anatomy of dysplastic hips, THA in these patients represents technically demanding procedure. Distorted anatomy of the acetabulum and proximal femur together with conjoined leg length discrepancy present major challenges during performing THA in patients with developmental dysplasia of the hip. In addition, most patients are at younger age, therefore, soft tissue balance is of great importance (especially the need to preserve the continuity of abductors) to maximise postoperative functional result. In this paper we present a variety of surgical techniques available for THA in dysplastic hips, their advantages and disadvantages. For acetabular reconstruction following techniques are described: Standard metal augments (prefabricated), Custom made acetabular augments (3D printing), Roof reconstruction with vascularized fibula, Roof reconstruction with pedicled iliac graft, Roof reconstruction with autologous bone graft, Roof reconstruction with homologous bone graft, Roof reconstruction with auto/homologous spongious bone, Reinforcement ring with the hook in combination with autologous graft augmentation, Cranial positioning of the acetabulum, Medial protrusion technique (cotyloplasty) with chisel, Medial protrusion technique (cotyloplasty) with reaming, Cotyloplasty without spongioplasty. For femoral reconstruction following techniques were described: Distraction with external fixator, Femoral shortening through a modified lateral approach, Transtrochanteric osteotomies, Paavilainen osteotomy, Lesser trochanter osteotomy, Double-chevron osteotomy, Subtrochanteric osteotomies, Diaphyseal osteotomies, Distal femoral osteotomies. At the end we present author's treatment method of choice: for acetabulum we perform cotyloplasty leaving only paper-thin medial wall, which we break during acetabular
Retrograde intra-vesical reconstructive surgery (RIVRS): A novel technique
Laddha, Abhishek; Ganpule, Arvind; Mishra, Sahshikant; Sabnis, Ravindra; Desai, Mahesh
2016-01-01
Management of distal ureter by en block resection during radical nephrectomy for upper urinary tract transitional cell carcinoma (TCC) is considered as standard of care. In this report, we describe our technique for management of lower ureter which utilizes both the endoscopic and laparoscopic approach. The nephrectomy including the dissection of the lower ureter was completed laproscopically. The ureteral orifice was scored using a hook passed through a 24 Fr nephroscope and secured .Transurethral suturing of the defect with SewRight SR5 device passed through the working channel of the 24 Fr nephroscope was done. Our report highlights the fact that management of lower ureter in TCC pelvis can be done endoscopically/laproscopically without compromising the oncological principles. Our novel technique demonstrates feasibility of intra mural resection of the ureter and primary closure of the bladder endoscopically. PMID:27279408
Retrograde intra-vesical reconstructive surgery (RIVRS): A novel technique.
Laddha, Abhishek; Ganpule, Arvind; Mishra, Sahshikant; Sabnis, Ravindra; Desai, Mahesh
2016-01-01
Management of distal ureter by en block resection during radical nephrectomy for upper urinary tract transitional cell carcinoma (TCC) is considered as standard of care. In this report, we describe our technique for management of lower ureter which utilizes both the endoscopic and laparoscopic approach. The nephrectomy including the dissection of the lower ureter was completed laproscopically. The ureteral orifice was scored using a hook passed through a 24 Fr nephroscope and secured .Transurethral suturing of the defect with SewRight SR5 device passed through the working channel of the 24 Fr nephroscope was done. Our report highlights the fact that management of lower ureter in TCC pelvis can be done endoscopically/laproscopically without compromising the oncological principles. Our novel technique demonstrates feasibility of intra mural resection of the ureter and primary closure of the bladder endoscopically. PMID:27279408
NASA Astrophysics Data System (ADS)
Gómez-Navarro, Juan José; Werner, Johannes; Wagner, Sebastian; Luterbacher, Jürg; Zorita, Eduardo
2015-09-01
This study aims at assessing the skill of several climate field reconstruction techniques (CFR) to reconstruct past precipitation over continental Europe and the Mediterranean at seasonal time scales over the last two millennia from proxy records. A number of pseudoproxy experiments are performed within the virtual reality of a regional paleoclimate simulation at 45 km resolution to analyse different aspects of reconstruction skill. Canonical Correlation Analysis (CCA), two versions of an Analog Method (AM) and Bayesian hierarchical modeling (BHM) are applied to reconstruct precipitation from a synthetic network of pseudoproxies that are contaminated with various types of noise. The skill of the derived reconstructions is assessed through comparison with precipitation simulated by the regional climate model. Unlike BHM, CCA systematically underestimates the variance. The AM can be adjusted to overcome this shortcoming, presenting an intermediate behaviour between the two aforementioned techniques. However, a trade-off between reconstruction-target correlations and reconstructed variance is the drawback of all CFR techniques. CCA (BHM) presents the largest (lowest) skill in preserving the temporal evolution, whereas the AM can be tuned to reproduce better correlation at the expense of losing variance. While BHM has been shown to perform well for temperatures, it relies heavily on prescribed spatial correlation lengths. While this assumption is valid for temperature, it is hardly warranted for precipitation. In general, none of the methods outperforms the other. All experiments agree that a dense and regularly distributed proxy network is required to reconstruct precipitation accurately, reflecting its high spatial and temporal variability. This is especially true in summer, when a specifically short de-correlation distance from the proxy location is caused by localised summertime convective precipitation events.
Model-based super-resolution reconstruction techniques for underwater imaging
NASA Astrophysics Data System (ADS)
Chen, Yuzhang; Yang, Bofei; Xia, Min; Li, Wei; Yang, Kecheng; Zhang, Xiaohui
2012-01-01
The visibility of underwater imaging has been of long-standing interest to investigators working in many civilian and military areas such as oceanographic environments, efforts such as image restoration techniques can help to enhance the image quality; however, the resolution is still limited. Image super resolution reconstruction (SRR) techniques are promising approaches for improving resolution beyond the limit of hardware; furthermore, with the prior knowledge of the imaging system such as the point spread function and diffration limit, performance of the super resolution reconstruction can be further enhanced, which can also extend the imaging range as well. In order to improve the resolution to a best possible level, an imaging model based on beam propagation is established and applied to image super-resolution reconstruction techniques for an underwater range-gated pulsed laser imaging system in the presented effort. Experimental results show that the proposed approaches can effectively enhance the resolution and quality of underwater imaging
Model-based super-resolution reconstruction techniques for underwater imaging
NASA Astrophysics Data System (ADS)
Chen, Yuzhang; Yang, Bofei; Xia, Min; Li, Wei; Yang, Kecheng; Zhang, Xiaohui
2011-11-01
The visibility of underwater imaging has been of long-standing interest to investigators working in many civilian and military areas such as oceanographic environments, efforts such as image restoration techniques can help to enhance the image quality; however, the resolution is still limited. Image super resolution reconstruction (SRR) techniques are promising approaches for improving resolution beyond the limit of hardware; furthermore, with the prior knowledge of the imaging system such as the point spread function and diffration limit, performance of the super resolution reconstruction can be further enhanced, which can also extend the imaging range as well. In order to improve the resolution to a best possible level, an imaging model based on beam propagation is established and applied to image super-resolution reconstruction techniques for an underwater range-gated pulsed laser imaging system in the presented effort. Experimental results show that the proposed approaches can effectively enhance the resolution and quality of underwater imaging
A novel data processing technique for image reconstruction of penumbral imaging
NASA Astrophysics Data System (ADS)
Xie, Hongwei; Li, Hongyun; Xu, Zeping; Song, Guzhou; Zhang, Faqiang; Zhou, Lin
2011-06-01
CT image reconstruction technique was applied to the data processing of the penumbral imaging. Compared with other traditional processing techniques for penumbral coded pinhole image such as Wiener, Lucy-Richardson and blind technique, this approach is brand new. In this method, the coded aperture processing method was used for the first time independent to the point spread function of the image diagnostic system. In this way, the technical obstacles was overcome in the traditional coded pinhole image processing caused by the uncertainty of point spread function of the image diagnostic system. Then based on the theoretical study, the simulation of penumbral imaging and image reconstruction was carried out to provide fairly good results. While in the visible light experiment, the point source of light was used to irradiate a 5mm×5mm object after diffuse scattering and volume scattering. The penumbral imaging was made with aperture size of ~20mm. Finally, the CT image reconstruction technique was used for image reconstruction to provide a fairly good reconstruction result.
Fang, L; Zhang, J
2010-01-01
Two informants were interviewed for each of 416 living controls (individuals sampled from the normal population) interviewed in a Chinese case-control psychological autopsy study. The validity of proxy data, obtained using seven psychological autopsy information reconstruction techniques (types 1, 2 and A - E), was evaluated, with living controls' self reports used as the gold-standard. Proxy data for reconstruction technique types 1, 2 and D on the Impulsivity Inventory Scale (total impulsivity score) were no different from the living controls' self report gold standard, whereas data for types A and E were smaller than data from living controls. On the 'acceptance or resignation' sub-scale of the avoidance coping dimension of the Moos Coping Response Inventory, information obtained by reconstruction technique types 1 and D was not significantly different from the living controls' self reports, whereas proxy data from types 2, A and E were smaller than those from the living controls. No statistically significant differences were identified for other proxy data obtained by reconstruction technique types 1, 2, A, D and E. These results indicate that using a second informant does not significantly enhance information reconstruction for the target. PMID:20819420
Nha, Kyung-Wook; Han, Jae-Hwi; Kwon, Jae-Ho; Kang, Kyung-Woon; Park, Hyung-Joon
2015-01-01
Purpose In anatomical single-bundle (SB) anterior cruciate ligament (ACL) reconstruction, the traditional transtibial approach can limit anatomical placement of the femoral tunnel. Surgical Technique We present a novel three-point freehand technique that allows for anatomic SB ACL reconstruction with the transtibial technique. Materials and Methods Between January 2012 and December 2012, 55 ACL reconstructions were performed using the three-point freehand technique. All the patients were followed for a minimum of 12 months post-operatively. Clinical evaluation was done using the Lysholm score and International Knee Documentation Committee (IKDC) grade. All patients were analyzed by 3-dimensional computed tomography (3D CT) at 1 week after surgery. Results The mean Lysholm score improved from 68.2±12.7 points preoperatively to 89.2±8.2 points at final follow-up. At final follow-up, the IKDC grade was normal in 42 patients and nearly normal in 13 patients. None of the patients had a positive pivot shift test, anterior drawer test and Lachman test at final follow-up. The anatomical position of the femoral tunnel was confirmed on 3D CT scans. Conclusions The three-point freehand technique for SB transtibial ACL reconstruction is a simple, anatomic technique showing good clinical results. PMID:26060611
Scapholunate interosseus ligament reconstruction on a cadaver: A technique
Arenas-Prat, Joan
2014-01-01
Background: Acute rupture of the scapholunate interosseus ligament is a relatively frequent occurrence which can be repaired primarily by direct suturing. However, patients are often seen a few weeks after injury when most of the ligament fibers have degenerated. This poses a challenge because direct repair can be difficult and long term results have not been satisfying. In the present study, a technique is presented to address this problem and its possible advantages are discussed. Materials and Methods: A fresh frozen wrist cadaver specimen, thawed to room temperature, was used to carry out the procedure. The scapholunate joint was exposed through a dorsal approach and stabilized using two percutaneous Kirschner wires. Using a U shaped chisel, a groove along the scapholunate articular margin was created to accommodate a strip from the extensor retinaculum as a ligament plasty. This has been secured using six anchor sutures and several pictures taken during the procedure to expose the key steps. Results: The ligamentoplasty presented in this article preserves most of the articular surface of proximal carpus and at the same time stabilizes the scapholunate joint. However, more in vivo research should be carried out to validate this treatment. Conclusion: The technique suggests a possible way to repair a ruptured scapholunate interosseus ligament that cannot be repaired primarily. Because osteointegration of the ligament strips is not possible in the present experiment, biomechanics of the construct cannot be fully tested. PMID:25298562
Development of Acoustic Model-Based Iterative Reconstruction Technique for Thick-Concrete Imaging
Almansouri, Hani; Clayton, Dwight A; Kisner, Roger A; Polsky, Yarom; Bouman, Charlie; Santos-Villalobos, Hector J
2015-01-01
Ultrasound signals have been used extensively for non-destructive evaluation (NDE). However, typical reconstruction techniques, such as the synthetic aperture focusing technique (SAFT), are limited to quasi-homogenous thin media. New ultrasonic systems and reconstruction algorithms are in need for one-sided NDE of non-homogenous thick objects. An application example space is imaging of reinforced concrete structures for commercial nuclear power plants (NPPs). These structures provide important foundation, support, shielding, and containment functions. Identification and management of aging and degradation of concrete structures is fundamental to the proposed long-term operation of NPPs. Another example is geothermal and oil/gas production wells. These multi-layered structures are composed of steel, cement, and several types of soil and rocks. Ultrasound systems with greater penetration range and image quality will allow for better monitoring of the well s health and prediction of high-pressure hydraulic fracturing of the rock. These application challenges need to be addressed with an integrated imaging approach, where the application, hardware, and reconstruction software are highly integrated and optimized. Therefore, we are developing an ultrasonic system with Model-Based Iterative Reconstruction (MBIR) as the image reconstruction backbone. As the first implementation of MBIR for ultrasonic signals, this paper document the first implementation of the algorithm and show reconstruction results for synthetically generated data.
Development of Acoustic Model-Based Iterative Reconstruction Technique for Thick-Concrete Imaging
Almansouri, Hani; Clayton, Dwight A; Kisner, Roger A; Polsky, Yarom; Bouman, Charlie; Santos-Villalobos, Hector J
2016-01-01
Ultrasound signals have been used extensively for non-destructive evaluation (NDE). However, typical reconstruction techniques, such as the synthetic aperture focusing technique (SAFT), are limited to quasi-homogenous thin media. New ultrasonic systems and reconstruction algorithms are in need for one-sided NDE of non-homogenous thick objects. An application example space is imaging of reinforced concrete structures for commercial nuclear power plants (NPPs). These structures provide important foundation, support, shielding, and containment functions. Identification and management of aging and degradation of concrete structures is fundamental to the proposed long-term operation of NPPs. Another example is geothermal and oil/gas production wells. These multi-layered structures are composed of steel, cement, and several types of soil and rocks. Ultrasound systems with greater penetration range and image quality will allow for better monitoring of the well's health and prediction of high-pressure hydraulic fracturing of the rock. These application challenges need to be addressed with an integrated imaging approach, where the application, hardware, and reconstruction software are highly integrated and optimized. Therefore, we are developing an ultrasonic system with Model-Based Iterative Reconstruction (MBIR) as the image reconstruction backbone. As the first implementation of MBIR for ultrasonic signals, this paper document the first implementation of the algorithm and show reconstruction results for synthetically generated data.
Development of acoustic model-based iterative reconstruction technique for thick-concrete imaging
NASA Astrophysics Data System (ADS)
Almansouri, Hani; Clayton, Dwight; Kisner, Roger; Polsky, Yarom; Bouman, Charles; Santos-Villalobos, Hector
2016-02-01
Ultrasound signals have been used extensively for non-destructive evaluation (NDE). However, typical reconstruction techniques, such as the synthetic aperture focusing technique (SAFT), are limited to quasi-homogenous thin media. New ultrasonic systems and reconstruction algorithms are in need for one-sided NDE of non-homogenous thick objects. An application example space is imaging of reinforced concrete structures for commercial nuclear power plants (NPPs). These structures provide important foundation, support, shielding, and containment functions. Identification and management of aging and degradation of concrete structures is fundamental to the proposed long-term operation of NPPs. Another example is geothermal and oil/gas production wells. These multi-layered structures are composed of steel, cement, and several types of soil and rocks. Ultrasound systems with greater penetration range and image quality will allow for better monitoring of the well's health and prediction of high-pressure hydraulic fracturing of the rock. These application challenges need to be addressed with an integrated imaging approach, where the application, hardware, and reconstruction software are highly integrated and optimized. Therefore, we are developing an ultrasonic system with Model-Based Iterative Reconstruction (MBIR) as the image reconstruction backbone. As the first implementation of MBIR for ultrasonic signals, this paper document the first implementation of the algorithm and show reconstruction results for synthetically generated data.1
All-Inside Posterior Cruciate Ligament Reconstruction: GraftLink Technique
Prince, Matthew R.; Stuart, Michael J.; King, Alexander H.; Sousa, Paul L.; Levy, Bruce A.
2015-01-01
Posterior cruciate ligament (PCL) injuries account for nearly 20% of knee ligament injuries. PCL injuries can occur in isolation or, more commonly, in the setting of multiligamentous knee injuries. Isolated PCL disruptions are commonly treated nonoperatively; however, symptomatic grade III injuries, as well as PCL injuries found in multiligamentous injuries, are frequently treated surgically. Several reconstructive techniques exist for the treatment of PCL deficiency without a clear optimal approach. We describe our preferred operative technique to reconstruct the PCL using an all-inside arthroscopic approach with a quadrupled tibialis anterior or peroneus longus allograft with both tibial and femoral suspensory fixation. PMID:26900564
All-Inside Posterior Cruciate Ligament Reconstruction: GraftLink Technique.
Prince, Matthew R; Stuart, Michael J; King, Alexander H; Sousa, Paul L; Levy, Bruce A
2015-10-01
Posterior cruciate ligament (PCL) injuries account for nearly 20% of knee ligament injuries. PCL injuries can occur in isolation or, more commonly, in the setting of multiligamentous knee injuries. Isolated PCL disruptions are commonly treated nonoperatively; however, symptomatic grade III injuries, as well as PCL injuries found in multiligamentous injuries, are frequently treated surgically. Several reconstructive techniques exist for the treatment of PCL deficiency without a clear optimal approach. We describe our preferred operative technique to reconstruct the PCL using an all-inside arthroscopic approach with a quadrupled tibialis anterior or peroneus longus allograft with both tibial and femoral suspensory fixation. PMID:26900564
Falaggis, Konstantinos; Kozacki, Tomasz; Kujawinska, Malgorzata
2013-05-15
A previous Letter by Pedrini et al. [Opt. Lett. 30, 833 (2005)] proposed an iterative single-beam wavefront reconstruction algorithm that uses a sequence of interferograms recorded at different planes. In this Letter, the use of relaxation and multiresolution strategies is investigated in terms of accuracy and computational effort. It is shown that the convergence rate of the conventional iterative algorithm can be significantly improved with the use of relaxation techniques combined with a hierarchy of downsampled intensities that are used within a preconditioner. These techniques prove to be more robust, to achieve a higher accuracy, and to overcome the stagnation problem met in the iterative wavefront reconstruction. PMID:23938902
Millett, Peter J.; Warth, Ryan J.; Greenspoon, Joshua A.; Horan, Marilee P.
2015-01-01
Acromioclavicular joint injuries are common and are often seen in contact athletes. Good to excellent clinical results have been reported using soft-tissue grafts to reconstruct the coracoclavicular ligaments; however, complications remain. Some complications are unique to the surgical technique, particularly clavicle and coracoid fractures that are associated with drilling large or multiple bone tunnels. The described technique allows for an anatomic coracoclavicular reconstruction using a large soft-tissue graft while minimizing the risk of clavicle fracture by avoiding large bone tunnels. PMID:26900558
New signal processing technique for density profile reconstruction using reflectometry
Clairet, F.; Bottereau, C.; Ricaud, B.; Briolle, F.; Heuraux, S.
2011-08-15
Reflectometry profile measurement requires an accurate determination of the plasma reflected signal. Along with a good resolution and a high signal to noise ratio of the phase measurement, adequate data analysis is required. A new data processing based on time-frequency tomographic representation is used. It provides a clearer separation between multiple components and improves isolation of the relevant signals. In this paper, this data processing technique is applied to two sets of signals coming from two different reflectometer devices used on the Tore Supra tokamak. For the standard density profile reflectometry, it improves the initialization process and its reliability, providing a more accurate profile determination in the far scrape-off layer with density measurements as low as 10{sup 16} m{sup -1}. For a second reflectometer, which provides measurements in front of a lower hybrid launcher, this method improves the separation of the relevant plasma signal from multi-reflection processes due to the proximity of the plasma.
New signal processing technique for density profile reconstruction using reflectometry.
Clairet, F; Ricaud, B; Briolle, F; Heuraux, S; Bottereau, C
2011-08-01
Reflectometry profile measurement requires an accurate determination of the plasma reflected signal. Along with a good resolution and a high signal to noise ratio of the phase measurement, adequate data analysis is required. A new data processing based on time-frequency tomographic representation is used. It provides a clearer separation between multiple components and improves isolation of the relevant signals. In this paper, this data processing technique is applied to two sets of signals coming from two different reflectometer devices used on the Tore Supra tokamak. For the standard density profile reflectometry, it improves the initialization process and its reliability, providing a more accurate profile determination in the far scrape-off layer with density measurements as low as 10(16) m(-1). For a second reflectometer, which provides measurements in front of a lower hybrid launcher, this method improves the separation of the relevant plasma signal from multi-reflection processes due to the proximity of the plasma. PMID:21895243
Didier, Ryne A.; Vajtai, Petra L.
2014-01-01
Background Iterative reconstruction technique has been proposed as a means of reducing patient radiation dose in pediatric CT. Yet, the effect of such reductions on diagnostic accuracy has not been thoroughly evaluated. Objective This study compares accuracy of diagnosing pediatric acute appendicitis using contrast-enhanced abdominopelvic CT scans performed with traditional pediatric weight-based protocols and filtered back projection reconstruction versus a filtered back projection/iterative reconstruction technique blend with reduced volume CT dose index (CTDIvol). Materials and methods Results of pediatric contrast-enhanced abdominopelvic CT scans done for pain and/or suspected appendicitis were reviewed in two groups: A, 192 scans performed with the hospital’s established weight-based CT protocols and filtered back projection reconstruction; B, 194 scans performed with iterative reconstruction technique and reduced CTDIvol. Reduced CTDIvol was achieved primarily by reductions in effective tube current-time product (mAseff) and tube peak kilovoltage (kVp). CT interpretation was correlated with clinical follow-up and/or surgical pathology. CTDIvol, size specific dose estimates (SSDE) and performance characteristics of the two CT techniques were then compared. Results Between groups A and B, mean CTDIvol was reduced by 45%, and mean SSDE was reduced by 46%. Sensitivity, specificity and diagnostic accuracy were 96%, 97% and 96% in group A vs. 100%, 99% and 99% in group B. Conclusion Accuracy in diagnosing pediatric acute appendicitis was maintained in contrast-enhanced abdominopelvic CT scans that incorporated iterative reconstruction technique, despite reductions in mean CTDIvol and SSDE by nearly half as compared to the hospital’s traditional weight-based protocols. PMID:24996812
NASA Astrophysics Data System (ADS)
Wang, J.; Emile-Geay, J.; Guillot, D.; Smerdon, J. E.; Rajaratnam, B.
2014-01-01
Pseudoproxy experiments (PPEs) have become an important framework for evaluating paleoclimate reconstruction methods. Most existing PPE studies assume constant proxy availability through time and uniform proxy quality across the pseudoproxy network. Real multiproxy networks are, however, marked by pronounced disparities in proxy quality, and a steep decline in proxy availability back in time, either of which may have large effects on reconstruction skill. A suite of PPEs constructed from a millennium-length general circulation model (GCM) simulation is thus designed to mimic these various real-world characteristics. The new pseudoproxy network is used to evaluate four climate field reconstruction (CFR) techniques: truncated total least squares embedded within the regularized EM (expectation-maximization) algorithm (RegEM-TTLS), the Mann et al. (2009) implementation of RegEM-TTLS (M09), canonical correlation analysis (CCA), and Gaussian graphical models embedded within RegEM (GraphEM). Each method's risk properties are also assessed via a 100-member noise ensemble. Contrary to expectation, it is found that reconstruction skill does not vary monotonically with proxy availability, but also is a function of the type and amplitude of climate variability (forced events vs. internal variability). The use of realistic spatiotemporal pseudoproxy characteristics also exposes large inter-method differences. Despite the comparable fidelity in reconstructing the global mean temperature, spatial skill varies considerably between CFR techniques. Both GraphEM and CCA efficiently exploit teleconnections, and produce consistent reconstructions across the ensemble. RegEM-TTLS and M09 appear advantageous for reconstructions on highly noisy data, but are subject to larger stochastic variations across different realizations of pseudoproxy noise. Results collectively highlight the importance of designing realistic pseudoproxy networks and implementing multiple noise realizations of PPEs
[Regeneration of the ocular surface: stem cells and reconstructive techniques].
Fernández, A; Moreno, J; Prósper, F; García, M; Echeveste, J
2008-01-01
The cornea is a transparent tissue microscopically constituted by 5 well differentiated layers. The corneal epithelium is essential for corneal transparency and is found in a state of constant renovation throughout life on the basis of the population of limbocorneal stem cells. The localisation of these limbocorneal stem cells seems to be in the basal layers of the limbocorneal epithelium, of vital importance for maintaining the micro-environment of these limbocorneal stem cells, which depend on a variety of intrinsic and extrinsic factors. Limbic insufficiency occurs when there is a partial or total loss of these limbocorneal stem cells. These clinical features lead to a corneal clouding with a resulting loss of vision. In these cases, corneal transplant only represents a temporary replacement of the corneal epithelium; it is necessary to carry out a prior treatment involving transplant of the autologous or allogeneic limbus, which enables regeneration of the population of damaged limbocorneal cells. To reduce the risk involved in the transplant of the limbus of the donor eye, techniques of cultivation of limbocorneal cells on the basis of small limbocorneal biopsies are proposed. PMID:18496580
Jeong, Chang Wook; Oh, Jong Jin; Jeong, Seong Jin; Hong, Sung Kyu; Byun, Seok-Soo; Choe, Gheeyoung; Lee, Sang Eun
2012-07-01
The aim of the present study was to assess the impact of a novel posterior reconstruction technique during robot-assisted laparoscopic prostatectomy on continence recovery. A total of 116 consecutive patients who received the novel posterior reconstruction (case group) were retrospectively compared with a cohort of 126 patients who did not receive posterior reconstruction (control group). The primary end-point was the duration of continence recovery (no pad use) after robot-assisted laparoscopic prostatectomy. The posterior reconstruction was obtained by opposing the median dorsal fibrous raphe to the posterior counterpart of the detrusor apron, rather than the Denonvilliers' fascia. The case group showed higher continence rates at all points of evaluation, which were 2 weeks (30.1% vs 19.8%), 1 month (58.4% vs 45.7%), 3 months (82.7% vs 70.5%) and 6 months postoperatively (95.3% vs 86.4%) (P = 0.007). Application of the novel posterior reconstruction technique, age and length of membranous urethra were significant variables for the complete recovery of continence on multivariable analysis. This study shows that the application of this novel PR technique significantly improves the recovery of continence in patients undergoing robot-assisted laparoscopic prostatectomy. PMID:22404556
Ahmad, Munir; Shahzad, Tasawar; Masood, Khalid; Rashid, Khalid; Tanveer, Muhammad; Iqbal, Rabail; Hussain, Nasir; Shahid, Abubakar; Fazal-E-Aleem
2016-06-01
Emission tomographic image reconstruction is an ill-posed problem due to limited and noisy data and various image-degrading effects affecting the data and leads to noisy reconstructions. Explicit regularization, through iterative reconstruction methods, is considered better to compensate for reconstruction-based noise. Local smoothing and edge-preserving regularization methods can reduce reconstruction-based noise. However, these methods produce overly smoothed images or blocky artefacts in the final image because they can only exploit local image properties. Recently, non-local regularization techniques have been introduced, to overcome these problems, by incorporating geometrical global continuity and connectivity present in the objective image. These techniques can overcome drawbacks of local regularization methods; however, they also have certain limitations, such as choice of the regularization function, neighbourhood size or calibration of several empirical parameters involved. This work compares different local and non-local regularization techniques used in emission tomographic imaging in general and emission computed tomography in specific for improved quality of the resultant images. PMID:26714680
Fuzzy zoning for feature matching technique in 3D reconstruction of nasal endoscopic images.
Rattanalappaiboon, Surapong; Bhongmakapat, Thongchai; Ritthipravat, Panrasee
2015-12-01
3D reconstruction from nasal endoscopic images greatly supports an otolaryngologist in examining nasal passages, mucosa, polyps, sinuses, and nasopharyx. In general, structure from motion is a popular technique. It consists of four main steps; (1) camera calibration, (2) feature extraction, (3) feature matching, and (4) 3D reconstruction. Scale Invariant Feature Transform (SIFT) algorithm is normally used for both feature extraction and feature matching. However, SIFT algorithm relatively consumes computational time particularly in the feature matching process because each feature in an image of interest is compared with all features in the subsequent image in order to find the best matched pair. A fuzzy zoning approach is developed for confining feature matching area. Matching between two corresponding features from different images can be efficiently performed. With this approach, it can greatly reduce the matching time. The proposed technique is tested with endoscopic images created from phantoms and compared with the original SIFT technique in terms of the matching time and average errors of the reconstructed models. Finally, original SIFT and the proposed fuzzy-based technique are applied to 3D model reconstruction of real nasal cavity based on images taken from a rigid nasal endoscope. The results showed that the fuzzy-based approach was significantly faster than traditional SIFT technique and provided similar quality of the 3D models. It could be used for creating a nasal cavity taken by a rigid nasal endoscope. PMID:26498516
A constrained reconstruction technique of hyperelasticity parameters for breast cancer assessment
NASA Astrophysics Data System (ADS)
Mehrabian, Hatef; Campbell, Gordon; Samani, Abbas
2010-12-01
In breast elastography, breast tissue usually undergoes large compression resulting in significant geometric and structural changes. This implies that breast elastography is associated with tissue nonlinear behavior. In this study, an elastography technique is presented and an inverse problem formulation is proposed to reconstruct parameters characterizing tissue hyperelasticity. Such parameters can potentially be used for tumor classification. This technique can also have other important clinical applications such as measuring normal tissue hyperelastic parameters in vivo. Such parameters are essential in planning and conducting computer-aided interventional procedures. The proposed parameter reconstruction technique uses a constrained iterative inversion; it can be viewed as an inverse problem. To solve this problem, we used a nonlinear finite element model corresponding to its forward problem. In this research, we applied Veronda-Westmann, Yeoh and polynomial models to model tissue hyperelasticity. To validate the proposed technique, we conducted studies involving numerical and tissue-mimicking phantoms. The numerical phantom consisted of a hemisphere connected to a cylinder, while we constructed the tissue-mimicking phantom from polyvinyl alcohol with freeze-thaw cycles that exhibits nonlinear mechanical behavior. Both phantoms consisted of three types of soft tissues which mimic adipose, fibroglandular tissue and a tumor. The results of the simulations and experiments show feasibility of accurate reconstruction of tumor tissue hyperelastic parameters using the proposed method. In the numerical phantom, all hyperelastic parameters corresponding to the three models were reconstructed with less than 2% error. With the tissue-mimicking phantom, we were able to reconstruct the ratio of the hyperelastic parameters reasonably accurately. Compared to the uniaxial test results, the average error of the ratios of the parameters reconstructed for inclusion to the middle
Esthetic Craniofacial Bony and Skull Base Reconstruction Using Flap Wrapping Technique.
Yano, Tomoyuki; Suesada, Nobuko; Usami, Satoshi
2016-07-01
For a safe and esthetic skull base reconstruction combined with repair of craniofacial bone defects, the authors introduce the flap wrapping technique in this study. This technique consists of skull base reconstruction using the vastus lateralis muscle of an anterolateral thigh (ALT) free flap, and structural craniofacial bony reconstruction using an autologous calvarial bone graft. The key to this technique is that all of the grafted autologous bone is wrapped with the vascularized fascia of the ALT free flap to protect the grafted bone from infection and exposure. Two anterior skull base tumors combined with craniofacial bony defects were included in this study. The subjects were a man and a woman, aged 18 and 64. Both patients had preoperative proton beam therapy. First, the skull base defect was filled with vastus lateralis muscle, and then structural reconstruction was performed with an autologous bone graft and a fabricated inner layer of calvarial bone, and then the grafted bone was completely wrapped in the vascularized fascia of the ALT free flap. By applying this technique, there was no intracranial infection or grafted bone exposure in these 2 patients postoperatively, even though both patients had preoperative proton beam therapy. Additionally, the vascularized fascia wrapped bone graft could provide a natural contour and prevent collapse of the craniofacial region, and this gives patients a better facial appearance even though they have had skull base surgery. PMID:27300454
NASA Astrophysics Data System (ADS)
Wagner, S.; Gomez-Navarro, J. J.; Zorita, E.; Werner, J.; Luterbacher, J.
2014-12-01
In recent years important efforts were focused in the development of Climate Field Reconstructions (CFR). These techniques allow merging a limited number of local reconstructions to produce a regular grid which accommodates climatic information from different proxy sources. Pseudo Proxy Experiments (PPE) are idealized experiments performed with synthetic data, typically generated with comprehensive climate models. The PPEs aim at assessing the accuracy that can be expected by (statistical) state-of-the-art reconstruction techniques, but also at identifying potential shortcomings and improvements.In this study a number of PPEs are investigated in order to assess the ability of three different CFR techniques to reconstruct precipitation over Europe. The methods comprise of a linear fit (Canonical Correlation Analysis, CCA), a simple non-linear approach (the Analog Method, AM) and a Bayesian model (Bayesian Hierarchical Method, BHM). Given the inherent complexity of this variable, hardly reproduced by state-of-the-art global circulation models, some downscaling technique is necessary to design meaningful PPEs. In this study the synthetic data consist of a high-resolution climate simulation performed with a Regional Climate Model over Europe for the last two Millennia. Results indicate that unlike BHM, CCA systematically underestimates the variance. TheAM can be adjusted to overcome this shortcoming, presenting an intermediate behavior between the two aforementioned techniques. However, a trade-off between reconstruction target correlations and reconstructed variance is the drawback common to all CFR techniques. CCA (BHM) represent the largest (lowest) skill in preserving the temporal evolution, whereas the AM can be tuned to reproduce better correlation at the expense of a loss in variance. While BHM, in the form employed here, has been shown to perform well for temperatures, it does heavily rely on prescribed spatial correlation lengths. For temperature this
Medial Patellofemoral Ligament Reconstruction: A Technique With a “V”-Shaped Patellar Tunnel
Ahmad, Riaz; Jayasekera, Narlaka; Schranz, Peter; Mandalia, Vipul
2014-01-01
Patellofemoral dislocation is a common problem affecting the young and active population. The medial patellofemoral ligament (MPFL) is torn when the patella dislocates as it acts as a checkrein to lateral displacement. This leads to patellar instability, and MPFL reconstruction is required if the dislocation recurs after a trial of rehabilitation. We describe a “V”-shaped patellar tunnel technique to reconstruct the MPFL using an autologous gracilis graft. This modification of the patellar tunnel does not breach the lateral cortex of the patella, and it allows a broader attachment of the tendon graft to the patella, which mimics the normal anatomic attachment of the MPFL to the patella. PMID:25473612
Contact Nd:YAG Laser Technique Applied To Head And Neck Reconstructive Surgery
NASA Astrophysics Data System (ADS)
Nobori, Takuo; Miyazaki, Yasuhiro; Moriyama, Ichiro; Sannikorn, Phakdee; Ohyama, Masaru
1989-09-01
The contact Nd:YAG laser system with ceramics tip was applied to head and neck reconstructive surgery. Plastic surgery was performed in 78 patients with head and neck diseases during the past 11 years. Since 1984 reconstructive surgery in these patients was made on 60 cases and on 45 cases(75%) of these cases the contact Nd:YAG laser surgery was used. Using this laser technique, half volume of bleeding in the operation was obtained as compared with that of the conventional procedure.
Baltzer, Heather L; Spinner, Robert J; Bishop, Allen T; Shin, Alexander Y
2015-12-01
Deltoid paralysis after axillary nerve injury results in limitations in shoulder function and stability. In the setting of an isolated axillary nerve injury with no clinical or electromyographic evidence of recovery that is within 6 to 9 months postinjury, the authors' preferred technique to reinnervate the deltoid is to reconstruct the axillary nerve with sural nerve grafting. Intraoperative neuromuscular electrophysiology is critical to determine the continuity of the axillary nerve before proceeding with reconstruction. The majority of the time, both an anterior and posterior incision and dissection of the axillary nerve is required to adequately delineate the zone of injury. This also ensures that both proximally and distally, uninjured axillary nerve is present before graft inset and also facilitates the ability to perform a meticulous microsurgical inset of the nerve graft posteriorly. The nerve graft must be pulled through from posterior to anterior to span the zone of injury and reconstruct the axillary nerve. Careful infraclavicular brachial plexus dissection is necessary to prevent further injury to components of the brachial plexus in the setting of a scarred bed. Patients will require postoperative therapy to prevent limitations in shoulder range of motion secondary to postoperative stiffness. This paper presents a detailed surgical technique for axillary nerve reconstruction by an anterior-posterior approach with a pull-through technique of a sural nerve cable graft. PMID:26524659
NASA Astrophysics Data System (ADS)
Laepple, T.; Heue, K.; Friedeburg, C. V.; Wang, P.; Knab, V.; Pundt, I.
2002-12-01
Tomographic-Differential-Optical-Absorption-Spectroscopy (Tom-DOAS) is a new application of the DOAS method designed to measure 2-3-dimensional concentration fields of different trace gases (e.g. NO2, HCHO, Ozone) in the troposphere. Numerical reconstruction techniques are used to obtain spatially resolved data from the slant column densities provided by DOAS instruments. We discuss the detection of emission plumes by AMAX (Airborne Multi AXis) DOAS Systems which measure sunlight by telescopes pointing in different directions. 2D distributions are reconstructed from slant columns by using airmass factor matrices and inversion techniques. We discuss possibilities and limitations of this technique gained with the use of simulated test fields. Therefore the effect of the parameter choice (e.g. flight track, algorithm changes) and measurement errors is investigated. Further, first results from the Partenavia aircraft measurements over Milano (Italy) during the European FORMAT campaign will be presented.
D'Elia, Caio Oliveira; Bitar, Alexandre Carneiro; Castropil, Wagner; Garofo, Antônio Guilherme Padovani; Cantuária, Anita Lopes; Orselli, Maria Isabel Veras; Luques, Isabela Ugo; Duarte, Marcos
2015-01-01
Objective: The objective of this study was to describe the methodology of knee rotation analysis using biomechanics laboratory instruments and to present the preliminary results from a comparative study on patients who underwent anterior cruciate ligament (ACL) reconstruction using the double-bundle technique. Methods: The protocol currently used in our laboratory was described. Three-dimensional kinematic analysis was performed and knee rotation amplitude was measured on eight normal patients (control group) and 12 patients who were operated using the double-bundle technique, by means of three tasks in the biomechanics laboratory. Results: No significant differences between operated and non-operated sides were shown in relation to the mean amplitudes of gait, gait with change in direction or gait with change in direction when going down stairs (p > 0.13). Conclusion: The preliminary results did not show any difference in the double-bundle ACL reconstruction technique in relation to the contralateral side and the control group. PMID:27027003
Lee, Byung-Ill; Kwon, Sai-Won; Choi, Hyung-Suk; Chun, Dong-Il; Kim, Yong-Beom; Kim, Byoung-Min
2015-01-01
This report describes a modified anatomic single-bundle anterior cruciate ligament (ACL) reconstruction technique using the FlipCutter guide pin (Arthrex, Naples, FL) as a retrograde drill and a cortical suspensory fixation device (TightRope; Arthrex) with an adjustable graft loop length. Preservation of the ACL remnant as a biological sleeve for the graft is an important issue from the viewpoints of acceleration of revascularization and ligamentization, preservation of the proprioceptive nerve fibers, enhancement of the biological environment for healing, and maintenance of the anchor point at the native tibial attachment, in addition to yielding a lower incidence of tibial bone tunnel enlargement. The goal of our technique is to obtain some advantages of the remnant-preserving technique through an anatomic single-bundle ACL reconstruction, which is performed to minimize damage to the ACL tibial remnant. PMID:26759771
NASA Technical Reports Server (NTRS)
Wood, E. H.
1976-01-01
The paper discusses the development of computer-controlled three-dimensional reconstruction techniques designed to determine the dynamic changes in the true shape and dimensions of the epi- and endocardial surfaces of the heart, along with variable time base (stop-action to real-time) displays of the transmural distribution of the coronary microcirculation and the three-dimensional anatomy of the macrovasculature in all regions of the body throughout individual cardiac and/or respiratory cycles. A technique for reconstructing a cross section of the heart from multiplanar videoroentgenograms is outlined. The capability of high spatial and high temporal resolution scanning videodensitometry makes possible measurement of the appearance, mean transit and clearance of roentgen opaque substances in three-dimensional space through the myocardium with a degree of simultaneous anatomic and temporal resolution not obtainable by current isotope techniques. The distribution of a variety of selected chemical elements or biologic materials within a body portion can also be determined.
The Flap Sandwich Technique for a Safe and Aesthetic Skull Base Reconstruction.
Yano, Tomoyuki; Okazaki, Mutsumi; Tanaka, Kentarou; Iida, Hideo
2016-02-01
For safe and reliable skull base reconstruction combined with repair of cranial bone defects, we introduce the flap sandwich technique in this study. A titanium mesh is often used to repair structural cranial bone defects because it has less donor site morbidity and is easy to handle. However, titanium mesh has disadvantages of exposure and infection postoperatively. To improve surgical outcomes, we applied the flap sandwich technique to 3 cases of skull base reconstruction combined with cranial bone defect repair. Two anterior skull base defects and 1 middle skull base defect were included in this study. The subjects were all women, aged 30, 58, and 62 years. One patient had former multiple craniotomies and another patient had preoperative radiotherapy. The flap sandwich technique involves structural cranial bone reconstruction with a titanium mesh and soft tissue reconstruction with a chimeric anterolateral thigh free flap. First, the dead space between the repaired dura and the titanium mesh is filled with vastus lateralis muscle, and then structural reconstruction is performed with a titanium mesh. Finally, the titanium mesh is totally covered with the adiposal flap of the anterolateral thigh free flap. The muscle flap protects the dead space from infection, and the adiposal flap covers the titanium mesh to reduce mechanical stress on the covered skin and thus prevent the exposure of the titanium mesh through the scalp. By applying this technique, there was no intracranial infection or titanium mesh exposure in these 3 cases postoperatively, even though 2 patients had postoperative radiotherapy. Additionally, the adiposal flap could provide a soft and natural contour to the scalp and forehead region, and this gives patients a better facial appearance even though they have had skull base surgery. PMID:25954846
NASA Astrophysics Data System (ADS)
Thomas, L.; Tremblais, B.; David, L.
2014-03-01
Optimization of multiplicative algebraic reconstruction technique (MART), simultaneous MART and block iterative MART reconstruction techniques was carried out on synthetic and experimental data. Different criteria were defined to improve the preprocessing of the initial images. Knowledge of how each reconstruction parameter influences the quality of particle volume reconstruction and computing time is the key in Tomo-PIV. These criteria were applied to a real case, a jet in cross flow, and were validated.
NASA Astrophysics Data System (ADS)
Fahimian, Benjamin Pooya
Tomographic imaging has had a radical impact on diverse fields ranging from the study of the small in microscopy, to the study of the large in astronomy, but perhaps most significantly, it has unequivocally revolutionized the practice of medicine. Although the applications of tomography are wide and diverse, the central problems associated with its mathematical and experimental implementation are similar. Most notably, the problem of image reconstruction from missing and noisy projection data and the problem of radiation dose imparted to biological specimens and patients are persistent and prominent problems in tomographic applications. Since by virtue of its nature, tomographic reconstruction is a mathematical problem, the development of more accurate and sophisticated reconstruction algorithms capable of solving for missing projection data and or producing accurate lower noise reconstructions, may hold promise in alleviating such problems. In this work, a method of tomographic acquisition and exact iterative Fourier-based reconstruction is developed, which in conjunction with physical constraints, advanced regularization constraints, and an oversampling method, aims to solve for the missing projection data and arrive at a less noisy solution in a manner that is concurrently and strictly consistent with the experimental data. Specifically, the proposed technique, termed Equally-Sloped Tomography (EST), is experimentally implemented and evaluated on four important transmission tomographic imaging modalities: transmission electron microtomography, synchrotron x-ray phase contrast tomography, synchrotron x-ray absorption tomography, and kilovoltage x-ray medical CT. In each modality, using a series of image quality phantoms studies, the performance of technique is quantitatively assessed and compared to existing methods. The potential for dose reduction is investigated by determining the factor by which the number of projections or the source flux can be reduced
NASA Astrophysics Data System (ADS)
Jarry, Genevieve
Treatment delivery verification is an essential step of radiotherapy. The purpose of this thesis is to develop new methods to improve the verification of photon and electron beam radiotherapy treatments. This is achieved through developing and testing (1) a way to acquire portal images during electron beam treatments, (2) a method to reconstruct the dose delivered to patients during photon beam treatments and (3) a technique to improve image quality in kilovoltage (kV) cone beam computed tomography (CBCT) by correcting for scattered radiation. The portal images were acquired using the Varian CL21EX linac and the Varian aS500 electronic portal imaging device (EPID). The EGSnrc code was used to model fully the CL21EX, the aS500 and the kV CBCT system. We demonstrate that portal images of electron beam treatments with adequate contrast and resolution can be produced using the bremsstrahlung photons portion of the electron beam. Monte Carlo (MC) calculations were used to characterize the bremsstrahlung photons and to obtain predicted images of various phantoms. The technique was applied on a head and neck patient. An algorithm to reconstruct the dose given to patients during photon beam radiotherapy was developed and validated. The algorithm uses portal images and MC simulations. The primary fluence at the detector is back-projected through the patient. CT geometry to obtain a reconstructed phase space file. The reconstructed phase space file is used to calculate the reconstructed dose to the patient using MC simulations. The reconstruction method was validated in homogeneous and heterogeneous phantoms for conventional and IMRT fields. The scattered radiation present in kV CBCT images was evaluated using MC simulations. Simulated predictions of the scatter distribution were subtracted from CBCT projection images prior to the reconstruction to improve the reconstructed image quality. Reducing the scattered radiation was found to improve contrast and reduce shading
Reconstruction of the mandible and the maxilla: the evolution of surgical technique.
Genden, Eric M
2010-01-01
The upper and lower jaws play an essential role in mastication, articulation, and cosmetic form. The mandible provides support for tongue position and elevation of the larynx during swallowing, while the maxilla provides support for the nasal structures as well as an opposing structure to the mandible during mastication. The evolution of mandibular and maxillary reconstruction dates back to the early 19th century. Before the introduction of free tissue transfer, a variety of local flaps, regional flaps, and prosthetics were introduced, yet each was met with eventual failure. Since the introduction of free tissue transfer, mandibular and maxillary reconstruction has become as much of an art as it has a science. Whether the mandibular or the palatomaxillary defects are a result of trauma, congenital deformity, or tumor extirpation, the resultant effect often disrupts both form and function. With these considerations taken together, jaw reconstruction is a unique undertaking in which the artistic reconstruction of the facial skeleton is met with the science of reestablishing the mechanics of mastication. The site, size, and associated soft-tissue defects represent the 3 most important factors in determining the impact of a given defect on function and aesthetics. There is also an inherent difference between defects that are sustained in a controlled fashion, such as during cancer ablation, and those that result from trauma. The consideration of these complexities in jaw reconstruction is reflected in the wide variety of approaches and techniques that have evolved over the past century. PMID:20231587
NASA Astrophysics Data System (ADS)
Yongyingsakthavorn, Pisit; Vallikul, Pumyos; Fungtammasan, Bundit; Dumouchel, Christophe
2007-03-01
This work proposes a new deconvolution technique to obtain local drop size distributions from line-of-sight intensity data measured by laser diffraction technique. The tomographic reconstruction, based on the maximum entropy (ME) technique, is applied to forward scattered light signal from a laser beam scanning horizontally through the spray on each plane from the center to the edge of spray, resulting in the reconstructed scattered light intensities at particular points in the spray. These reconstructed intensities are in turn converted to local drop size distributions. Unlike the classical method of the onion peeling technique or other mathematical transformation techniques that yield unrealistic negative scattered light intensity solutions, the maximum entropy constraints ensure positive light intensity. Experimental validations to the reconstructed results are achieved by using phase Doppler particle analyzer (PDPA). The results from the PDPA measurements agree very well with the proposed ME tomographic reconstruction.
A novel reconstruction method for giant incisional hernia: Hybrid laparoscopic technique
Ozturk, G; Malya, FU; Ersavas, C; Ozdenkaya, Y; Bektasoglu, H; Cipe, G; Citgez, B; Karatepe, O
2015-01-01
BACKGROUND AND OBJECTIVES: Laparoscopic reconstruction of ventral hernia is a popular technique today. Patients with large defects have various difficulties of laparoscopic approach. In this study, we aimed to present a new reconstruction technique that combines laparoscopic and open approach in giant incisional hernias. MATERIALS AND METHODS: Between January 2006 and August 2012, 28 patients who were operated consequently for incisional hernia with defect size over 10 cm included in this study and separated into two groups. Group 1 (n = 12) identifies patients operated with standard laparoscopic approach, whereas group 2 (n = 16) labels laparoscopic technique combined with open approach. Patients were evaluated in terms of age, gender, body mass index (BMI), mean operation time, length of hospital stay, surgical site infection (SSI) and recurrence rate. RESULTS: There are 12 patients in group 1 and 16 patients in group 2. Mean length of hospital stay and SSI rates are similar in both groups. Postoperative seroma formation was observed in six patients for group 1 and in only 1 patient for group 2. Group 1 had 1 patient who suffered from recurrence where group 2 had no recurrence. DISCUSSION: Laparoscopic technique combined with open approach may safely be used as an alternative method for reconstruction of giant incisional hernias. PMID:26622118
Force reconstruction using the sum of weighted accelerations technique -- Max-Flat procedure
Carne, T.G.; Mayes, R.L.; Bateman, V.I.
1993-12-31
Force reconstruction is a procedure in which the externally applied force is inferred from measured structural response rather than directly measured. In a recently developed technique, the response acceleration time-histories are multiplied by scalar weights and summed to produce the reconstructed force. This reconstruction is called the Sum of Weighted Accelerations Technique (SWAT). One step in the application of this technique is the calculation of the appropriate scalar weights. In this paper a new method of estimating the weights, using measured frequency response function data, is developed and contrasted with the traditional SWAT method of inverting the mode-shape matrix. The technique uses frequency response function data, but is not based on deconvolution. An application that will be discussed as part of this paper is the impact into a rigid barrier of a weapon system with an energy-absorbing nose. The nose had been designed to absorb the energy of impact and to mitigate the shock to the interior components.
NASA Astrophysics Data System (ADS)
Mathai, Pramod P.
the uncertainty in the parameters of the differential equations. There is a clear need to design better experiments for IEF without the current overhead of expensive chemicals and labor. We show how with a simpler modeling of the underlying chemistry, we can still achieve the accuracy that has been achieved in existing literature for modeling small ranges of pH (hydrogen ion concentration) in IEF, but with far less computational time. We investigate a further reduction of time by modeling the IEF problem using the Proper Orthogonal Decomposition (POD) technique and show why POD may not be sufficient due to the underlying constraints. The final problem that we address in this thesis addresses a certain class of dynamics with high stiffness - in particular, differential algebraic equations. With the help of simple examples, we show how the traditional POD procedure will fail to model certain high stiffness problems due to a particular behavior of the vector field which we will denote as twist. We further show how a novel augmentation to the traditional POD algorithm can model-reduce problems with twist in a computationally cheap manner without any additional data requirements.
NASA Astrophysics Data System (ADS)
Wang, J.; Emile-Geay, J.; Guillot, D.; Smerdon, J. E.; Rajaratnam, B.
2013-06-01
Pseudoproxy experiments (PPEs) have become an essential framework for evaluating paleoclimate reconstruction methods. Most existing PPE studies assume constant proxy availability through time and uniform proxy quality across the pseudoproxy network. Real multi-proxy networks are, however, marked by pronounced disparities in proxy quality, and a steep decline in proxy availability back in time, either of which may have large effects on reconstruction skill. Additionally, an investigation of a real-world global multi-proxy network suggests that proxies are not exclusively indicators of local climate; rather, many are indicative of large-scale teleconnections. A suite of PPEs constructed from a millennium-length general circulation model simulation is thus designed to mimic these various real-world characteristics. The new pseudoproxy network is used to evaluate four climate field reconstruction (CFR) techniques: truncated total least square embedded within the regularized EM algorithm (RegEM-TTLS), the Mann et al. (2009) implementation of RegEM-TTLS (M09), canonical correlation analysis (CCA), and Gaussian graphical models embedded within RegEM (GraphEM). Each method's risk properties are also assessed via a 100-member noise ensemble. Contrary to expectation, it is found that reconstruction skill does not vary monotonically with proxy availability, but rather is a function of the type of climate variability (forced events vs. internal variability). The use of realistic spatiotemporal pseudoproxy characteristics also exposes large inter-method differences. Despite the comparable fidelity in reconstructing the global mean temperature, spatial skill varies considerably between CFR techniques. Both GraphEM and CCA efficiently exploit teleconnections, and produce consistent reconstructions across the ensemble. RegEM-TTLS and M09 appear advantageous for reconstructions on highly noisy data, but are subject to larger stochastic variations across different realizations of
Arena Roof Technique for Complex Reconstruction After Extensive Chest Wall Resection.
Rocco, Gaetano; La Rocca, Antonello; La Manna, Carmine; Martucci, Nicola; De Luca, Giuseppe; Accardo, Rosanna
2015-10-01
Extensive primary resections or redos may produce significant chest wall defects requiring creative reconstructions in order to avoid reduction of the intrathoracic volume. We describe the successful use of an innovative technique for chest wall reconstruction based on the concept of roof coverage of sport arenas. In fact, titanium plates are anchored to the residual rib stumps along the parasternal and paravertebral lines. The acellular collagen matrix prosthesis was sutured to the free edges of the same titanium plates to create a roof, reproducing the chest wall dome geometric configuration. A 36-year-old female patient was diagnosed with an extensive desmoid tumor involving the lateral segments of second to fifth ribs on the right side. The arena roof technique allowed for adequate expansion of the uninvolved lung and optimal chest wall functional recovery. PMID:26434458
New less invasive ventricular reconstruction technique in the treatment of ischemic heart failure.
Faria, Rita; Melica, Bruno; Pires-Morais, Gustavo; Rodrigues, Alberto; Ribeiro, José; Guerra, Miguel; Gama, Vasco; Vouga, Luís
2014-01-01
Ischemic cardiomyopathy is the leading cause of heart failure. In patients with left ventricular (LV) dilatation, low ejection fraction, and transmural scar in an anteroseptal distribution, surgical ventricular reconstruction (SVR) is a treatment option. We describe our first experience with the Less Invasive Ventricular Enhancement (LIVE) technique using the Revivent™ system (Bioventrix Inc., San Ramon, CA), in the treatment of a large anteroapical aneurysm. PMID:25124657
Geometric Algebra for Physicists
NASA Astrophysics Data System (ADS)
Doran, Chris; Lasenby, Anthony
2007-11-01
Preface; Notation; 1. Introduction; 2. Geometric algebra in two and three dimensions; 3. Classical mechanics; 4. Foundations of geometric algebra; 5. Relativity and spacetime; 6. Geometric calculus; 7. Classical electrodynamics; 8. Quantum theory and spinors; 9. Multiparticle states and quantum entanglement; 10. Geometry; 11. Further topics in calculus and group theory; 12. Lagrangian and Hamiltonian techniques; 13. Symmetry and gauge theory; 14. Gravitation; Bibliography; Index.
Choi, Dong Hoon; Goh, Terence; Cho, Jae Young; Hong, Joon Pio
2014-11-01
Distant free flaps have become a routine option for reconstruction of large, complicated facial soft tissue defects. The challenge is to find a flap that is pliable to provide good contour and function. The purpose of this paper was to evaluate the use of superficial circumflex iliac artery perforator (SCIP) flaps for facial defects. From November 2010 to June 2013, facial reconstruction was performed on 6 patients (age range, 15-79 years). The harvesting technique was modified to elevate above the deep fat, and the pedicles were taken above or just below the deep fascia. The mean size of the flap was 75.6 cm2, with a thickness of 7 mm; the mean pedicle length was 4.9 cm; and the mean artery caliber was 0.7 mm. The supermicrosurgery technique was used successfully in all 6 cases. Donor sites were all closed primarily. The mean follow-up was 16.7 months. All flaps survived without flap loss, and the donor sites healed without complications including lymphorrhea. The patients were satisfied with contour and function after reconstruction. The result of these 6 cases suggested that the SCIP flap can be a reliable flap for moderate-sized to large defects in the face. The use of new instrumentation and supermicrosurgical techniques allows use of the SCIP flap reliably while providing patients with a good contour, function, and minimal donor site morbidity. PMID:25329846
A software channel compression technique for faster reconstruction with many channels.
Huang, Feng; Vijayakumar, Sathya; Li, Yu; Hertel, Sarah; Duensing, George R
2008-01-01
In magnetic resonance imaging, highly parallel imaging using coil arrays with a large number of elements is an area of growing interest. With increasing channel numbers for parallel acquisition, the increased reconstruction time and extensive computer memory requirements have become significant concerns. In this work, principal component analysis (PCA) is used to develop a channel compression technique. This technique efficiently reduces the size of parallel imaging data acquired from a multichannel coil array, thereby significantly reducing the reconstruction time and computer memory requirement without undermining the benefits of multichannel coil arrays. Clinical data collected with a 32-channel cardiac coil are used in all of the experiments. The performance of the proposed method on parallel, partially acquired data, as well as fully acquired data, was evaluated. Experimental results show that the proposed method dramatically reduces the processing time without considerable degradation in the quality of reconstructed images. It is also demonstrated that this PCA technique can be used to perform intensity correction in parallel imaging applications. PMID:17573223
Reconstruction of medial patello-femoral ligament: Comparison of two surgical techniques.
Criscenti, G; De Maria, C; Sebastiani, E; Tei, M; Placella, G; Speziali, A; Vozzi, G; Cerulli, G
2016-06-01
The medial patello-femoral ligament is considered the most important passive patellar stabilizer and its proper functionality is essential for the patello-femoral joint stability. In this work, 18 human knees were randomly divided into two groups and reconstructed through two different surgical techniques: the "Through tunnel tendon" and the "Double converging tunnel" reconstructions. Subsequently, the samples were mechanically tested to evaluate the structural properties of reconstructed femur-MPFL-Patella complex (rFMPC). Particular attention was given to maintain the anatomical orientation between the patella and the graft. Both procedures showed lower stiffness and higher ultimate strain and absorbed energy compared to the native MPFL, but the advantages of the double converging tunnel technique are related to the restoration of the native MPFL sail-shape, to a better stress distribution on the patella, to the use of a single interference screw as fixation device and to the simplicity, rapidity and cost-effectivity of the surgical procedure. The evaluation of the structural properties of rMPFL is fundamental to evaluate the adequacy of the different techniques to restore the physiological structural properties of the native MPFL. PMID:26894660
NASA Astrophysics Data System (ADS)
Sham, F. C.; Huang, Y. H.; Liu, L.; Chen, Y. S.; Hung, Y. Y.; Lo, T. Y.
2010-01-01
Infrared thermography is a rapid, non-invasive and full-field technique for non-destructive testing and evaluation (NDT&E). With all the achievements on IR instrumentation and image processing techniques attained, it has been extended far beyond simple hot-spot detection and becomes one of the most promising NDT&E techniques in the last decades. It has achieved increasing acceptance in different sectors include medical imaging, manufacturing component fault detection and buildings diagnostic. However, one limitation of IR thermography is that the testing results are greatly affected by object surface emissivity. Surface with various emissivities may lead to difficult discrimination between area of defect and area with different emissivity. Therefore, many studies have been carried out on eliminating emissivity, for example, the time derivative approach, lock-in processing and differential contrast measurements. In these methods, sequence of themo-data/images are recorded and being processed in order to eliminate differences of emissivity. Another problem of IR thermography is that any obstruction may limit stimulations and imaging which leads to the observation of unclear defect image. To solve this problem, this paper proposes an algorithm based on the principle of computerized tomography which permits the reconstruction of unavailable/partially available temperature distribution of the affected area using the measured surrounding temperature field. In the process, a set of imaginary rays are projected from many different directions across the area. For each ray, integration of the temperature derivatives along the ray is equals to the temperature difference between the boundary points intercepted by the ray. Therefore, a set of linear equations can be established by considering the multiple rays. Each equation expresses the unknown temperature derivatives in the affected area in terms of the measured boundary temperature data. Solution of the set of simultaneous
3-D flame temperature field reconstruction with multiobjective neural network
NASA Astrophysics Data System (ADS)
Wan, Xiong; Gao, Yiqing; Wang, Yuanmei
2003-02-01
A novel 3-D temperature field reconstruction method is proposed in this paper, which is based on multiwavelength thermometry and Hopfield neural network computed tomography. A mathematical model of multi-wavelength thermometry is founded, and a neural network algorithm based on multiobjective optimization is developed. Through computer simulation and comparison with the algebraic reconstruction technique (ART) and the filter back-projection algorithm (FBP), the reconstruction result of the new method is discussed in detail. The study shows that the new method always gives the best reconstruction results. At last, temperature distribution of a section of four peaks candle flame is reconstructed with this novel method.
Computed laminography and reconstruction algorithm
NASA Astrophysics Data System (ADS)
Que, Jie-Min; Cao, Da-Quan; Zhao, Wei; Tang, Xiao; Sun, Cui-Li; Wang, Yan-Fang; Wei, Cun-Feng; Shi, Rong-Jian; Wei, Long; Yu, Zhong-Qiang; Yan, Yong-Lian
2012-08-01
Computed laminography (CL) is an alternative to computed tomography if large objects are to be inspected with high resolution. This is especially true for planar objects. In this paper, we set up a new scanning geometry for CL, and study the algebraic reconstruction technique (ART) for CL imaging. We compare the results of ART with variant weighted functions by computer simulation with a digital phantom. It proves that ART algorithm is a good choice for the CL system.
Computer vision techniques for semi-automatic reconstruction of ripped-up documents
NASA Astrophysics Data System (ADS)
De Smet, Patrick; De Bock, Johan; Corluy, Els
2003-08-01
This paper investigates the use of computer vision techniques to aid in the semi-automatic reconstruction of torn or ripped-up documents. First, we discuss a procedure for obtaining a digital database of a given set of paper fragments using a flatbed image scanner, a brightly coloured scanner background, and a region growing algorithm. The contour of each segmented piece of paper is then traced around using a chain code algorithm and the contours are annotated by calculating a set of feature vectors. Next, the contours of the fragments are matched against each other using the annotated feature information and a string matching algorithm. Finally, the matching results are used to reposition the paper fragments so that a jigsaw puzzle reconstruction of the document can be obtained. For each of the three major components, i.e., segmentation, matching, and global document reconstruction, we briefly discuss a set of prototype GUI tools for guiding and presenting the obtained results. We discuss the performance and the reconstruction results that can be obtained, and show that the proposed framework can offer an interesting set of tools to forensic investigators.
NASA Astrophysics Data System (ADS)
Wakunami, K.; Oi, R.; Senoh, T.; Sasaki, H.; Ichihashi, Y.; Yamamoto, K.
2016-06-01
A hologram recording technique, generally called as "wavefront printer", has been proposed by several research groups for static three-dimensional (3D) image printing. Because the pixel number of current spatial light modulators (SLMs) is not enough to reconstruct the entire wavefront in recording process, typically, hologram data is divided into a set of subhologram data and each wavefront is recorded sequentially as a small sub-hologram cell in tiling manner by using X-Y motorized stage. However since previous works of wavefront printer do not optimize the cell size, the reconstructed images were degraded by obtrusive split line due to visible cell size caused by too large cell size for human eyesight, or by diffraction effect due to discontinuity of phase distribution caused by too small cell size. In this paper, we introduce overlapping recording approach of sub-holograms to achieve both conditions: enough smallness of apparent cell size to make cells invisible and enough largeness of recording cell size to suppress diffraction effect by keeping the phase continuity of reconstructed wavefront. By considering observing condition and optimization of the amount of overlapping and cell size, in the experiment, the proposed approach showed higher quality 3D image reconstruction while the conventional approach suffered visible split lines and cells.
Reconstruction of a maxillary defect with a fibula graft and titanium mesh using CAD/CAM techniques.
2010-01-01
We present a case of maxillary and orbital floor reconstruction with a microvascular fibula graft and an individualized titanium mesh. Both were planned virtually; templates were made by rapid prototyping. The postoperative computertomography scans showed that the planned positions were achieved correctly. This case report illustrates maxillary reconstruction performed with a special template technique and demonstrates the possibilities of computer aided design/computer aided manufacturing (CAD/CAM) applications in reconstructive surgery. PMID:20642821
An improved phase shift reconstruction algorithm of fringe scanning technique for X-ray microscopy
Lian, S.; Yang, H.; Kudo, H.; Momose, A.; Yashiro, W.
2015-02-15
The X-ray phase imaging method has been applied to observe soft biological tissues, and it is possible to image the soft tissues by using the benefit of the so-called “Talbot effect” by an X-ray grating. One type of the X-ray phase imaging method was reported by combining an X-ray imaging microscope equipped by a Fresnel zone plate with a phase grating. Using the fringe scanning technique, a high-precision phase shift image could be obtained by displacing the grating step by step and measuring dozens of sample images. The number of the images was selected to reduce the error caused by the non-sinusoidal component of the Talbot self-image at the imaging plane. A larger number suppressed the error more but increased radiation exposure and required higher mechanical stability of equipment. In this paper, we analyze the approximation error of fringe scanning technique for the X-ray microscopy which uses just one grating and proposes an improved algorithm. We compute the approximation error by iteration and substitute that into the process of reconstruction of phase shift. This procedure will suppress the error even with few sample images. The results of simulation experiments show that the precision of phase shift image reconstructed by the proposed algorithm with 4 sample images is almost the same as that reconstructed by the conventional algorithm with 40 sample images. We also have succeeded in the experiment with real data.
Lateral eyelid rotation flap: a novel technique for reconstruction of full thickness eyelid defect.
Pushker, Neelam; Batra, Jyoti; Meel, Rachna; Bajaj, Mandeep S; Chawla, Bhavna; Ghose, Supriyo
2015-12-01
The purpose of this study was to study anatomical, functional, and cosmetic outcomes of a novel technique, 'Lateral Eyelid Rotation Flap' for reconstruction of full thickness eyelid defect. In this prospective interventional study, 10 patients with full thickness eyelid defect measuring 1/2-2/3rd of eyelid width were included. Eyelid reconstruction was performed by single surgeon, using lateral eyelid rotation flap. Anatomic outcome was assessed by analyzing horizontal and vertical palpebral apertures (HPA and VPA), eyelid contour, and lateral canthus. Functional outcome was assessed by measuring tear film break-up time (TBUT) and Schirmer's test in both the eyes. Cosmetic outcome was evaluated by patients. Median age of patients was 56 years. Nine cases had full thickness defect following the excision of eyelid malignancy. The mean horizontal defect size was 17 ± 4.2 mm. HPA did not change significantly after surgery. VPA was statistically comparable to contralateral eye at 1-month follow-up. Lateral canthus angle recovered by 3rd month after surgery. TBUT and Schirmer's tests were comparable to contralateral eye. Eight patients graded cosmetic outcome as good to excellent. This is a new, single-stage technique for reconstruction of full thickness eyelid defects, with full thickness eyelid tissue including margin. PMID:25673519
Ray-tracing-based reconstruction algorithms for digital breast tomosynthesis
NASA Astrophysics Data System (ADS)
Zhou, Weihua; Lu, Jianping; Zhou, Otto; Chen, Ying
2015-03-01
As a breast-imaging technique, digital breast tomosynthesis has great potential to improve the diagnosis of early breast cancer over mammography. Ray-tracing-based reconstruction algorithms, such as ray-tracing back projection, maximum-likelihood expectation maximization (MLEM), ordered-subset MLEM (OS-MLEM), and simultaneous algebraic reconstruction technique (SART), have been developed as reconstruction methods for different breast tomosynthesis systems. This paper provides a comparative study to investigate these algorithms by computer simulation and phantom study. Experimental results suggested that, among the four investigated reconstruction algorithms, OS-MLEM and SART performed better in interplane artifact removal with a fast speed convergence.
Modified flexor digitorum superficialis slip technique for A4 pulley reconstruction.
Odobescu, A; Radu, A; Brutus, J-P; Gilardino, M S
2010-07-01
We describe a variation in the A4 pulley reconstruction technique using one slip of the flexor digitorum superficialis insertion and report the results of a biomechanical analysis of this reconstruction in cadavers. While conserving the distal bony insertion, one slip of flexor digitorum superficialis is transferred over the flexor digitorum profundus tendon and sutured to the contralateral superficialis slip insertion. This creates a new pulley at the base of the original A4 pulley that can be adjusted to accommodate an FDP repair of increased bulk. We found a 57% reduction in excess excursion due to bowstringing when compared with no repair. Furthermore the repairs were sturdy, 94% of specimens maintaining their integrity when a proximally directed force of 50 N was applied. PMID:20427405
Li, Quan; Zhang, Xin-Rui; Liu, Xue-Kui; Zhang, Zhi-Gang; Liu, Wei-Wei; Li, Hao; Guo, Zhu-Ming
2012-07-01
The free jejunum flap approach is the optimal option for circumferential pharyngolaryngectomy reconstruction. In this study, we designed a "watch window" for monitoring buried free jejunum flaps, thereby allowing us to assess graft viability. From 2007 to 2011, 14 patients with hypopharyngeal cancer underwent circumferential pharyngolaryngectomy that was reconstructed using a free jejunum flap at the Sun Yat-sen University Cancer Centre. During the closing of the neck incision, a "watch window" was designed for postoperative monitoring. Two patients experienced thrombosis of the pedicle. One was detected early and successfully rescued by removal of the thrombosis, the other one managed with a second free jejunum flap. The success rate of the buried flaps was 92.9%. No pharyngocutaneous fistulas or strictures occurred. All patients eventually resumed oral feeding and swallowing. The "watch window" technique for monitoring buried free jejunum flaps is simple, reliable and useful for finding vascular problems. Level of evidence Case series. PMID:22116384
Lin, Chao; Shen, Xueju; Wang, Zhisong; Zhao, Cheng
2014-06-20
We demonstrate a novel optical asymmetric cryptosystem based on the principle of elliptical polarized light linear truncation and a numerical reconstruction technique. The device of an array of linear polarizers is introduced to achieve linear truncation on the spatially resolved elliptical polarization distribution during image encryption. This encoding process can be characterized as confusion-based optical cryptography that involves no Fourier lens and diffusion operation. Based on the Jones matrix formalism, the intensity transmittance for this truncation is deduced to perform elliptical polarized light reconstruction based on two intensity measurements. Use of a quick response code makes the proposed cryptosystem practical, with versatile key sensitivity and fault tolerance. Both simulation and preliminary experimental results that support theoretical analysis are presented. An analysis of the resistance of the proposed method on a known public key attack is also provided. PMID:24979424
Temel, Metin; Gunal, Ertan; Kahraman, Serif Samil
2016-06-01
Congenital isolated alar defects are extremely rare, occurring in approximately 1 in 20,000 to 40,000 live births. The patients are presented here of 2 pediatric patients operated on for congenital isolated alar defect. The reconstruction of congenital isolated alar defects was made in a 3-layered fashion. The skin defects were covered using the Mutaf triangular closure technique in which 2 cutaneous local flaps are designed in an unequal Z-plasty manner. Conchal cartilage graft was used between the skin and mucosal closure to replace the missing part of the lower lateral cartilage in these patients. The early results were promising in Patient 1, but sufficient improvement was detected in the alar cartilage postoperative follow-up period in Patient 2. Hence, this patient required revision 1 to 2 years postoperatively. This technique provides excellent aesthetic and functional results, except for this problem in Tessier 2 cleft patients. The use of the Stair step flap technique with Mutaf triangle closure technique achieved cosmetically and functionally excellent results in the reconstruction and repair of a large, irregular, narrow cleft, in the inadequate rotation of the lateral part of the lower lateral cartilage. However, because of this problem, evaluation of the long-term follow-up of patients is necessary. PMID:27192642
ERIC Educational Resources Information Center
Schaufele, Christopher; Zumoff, Nancy
Earth Algebra is an entry level college algebra course that incorporates the spirit of the National Council of Teachers of Mathematics (NCTM) Curriculum and Evaluation Standards for School Mathematics at the college level. The context of the course places mathematics at the center of one of the major current concerns of the world. Through…
ERIC Educational Resources Information Center
Cavanagh, Sean
2009-01-01
As educators and policymakers search for ways to prepare students for the rigors of algebra, teachers in the Helena, Montana, school system are starting early by attempting to nurture students' algebraic-reasoning ability, as well as their basic number skills, in early elementary school, rather than waiting until middle or early high school.…
A technique for the reconstruction of a map of continuous curves from interference fringes
NASA Astrophysics Data System (ADS)
Palevicius, Paulius; Ragulskis, Minvydas; Janušas, Giedrius; Palevicius, Arvydas
2014-08-01
The well-known phase-shifting approach for three-dimensional surface measurement uses multiple fringe patterns along with the phase-shifting algorithm to obtain 3-D profiles with high accuracy though this approach is not applicable for dynamic object measurement techniques such as time-averaged holography and in cases when only a single interference fringe pattern is available. In this case the fringe tracing method can be used that is based on localization of centers of interference fringes. We propose a technique for the reconstruction of the contour map from fringe patterns which comprises standard image processing techniques and a scheme for reconstruction of the map of continuous curves from the binary matrix of pixels representing fringe centers. The approach of image division into grid cells is taken and such problems as derivation of approximate line equations in each cell using Hough transformation, grouping contacting cells into curves and interpolation between curves with fractures are solved. The functionality of this approach is demonstrated for a demanding optical image containing fractures and noise.
Ha, Tae-Yong; Hwang, Shin; Song, Gi-Won; Jung, Dong-Hwan; Kim, Myeong-Hwan; Lee, Sung-Goo; Kwon, Dong-Il; Ko, Gi-Young
2015-08-01
Secure reconstruction of multiple hepatic ducts severely damaged by tumor invasion or iatrogenic injury is very difficult. If percutaneous or endoscopic biliary stenting fails, one or more percutaneous transhepatic biliary drainage (PTBD) tubes must be maintained in place for the rest of the patient's life. To cope with such difficult situations, we present a surgical technique termed cluster hepaticojejunostomy (HJ), which can be coupled with palliative bile duct resection. The cluster HJ technique consisted of applying multiple internal biliary stents and a single wide porto-enterostomy to surrounding connective tissues. We present a preliminary study with six patients. Five perihilar cholangiocarcinoma patients undergoing palliative bile duct resection received this procedure. Follow-up PTBD tubogram and hepatobiliary scintigraphy were performed at 1-2 weeks after surgery, after which the PTBD tubes were removed. No patient showed surgical complications, and the 6-month patency rate of clustered HJ was 80%. Another patient with laparoscopic cholecystectomy-associated major bile duct injury showed no biliary complications in the 5-year period following this procedure. Based on the results of this study, the cluster HJ technique may be a useful surgical method enabling the secure reconstruction of severely damaged hilar bile ducts. PMID:25956723
Saft-reconstruction in ultrasonic immersion technique using phased array transducers
NASA Astrophysics Data System (ADS)
Kitze, J.; Prager, J.; Boehm, R.; Völz, U.; Montag, H.-J.
2012-05-01
The two main preconditions for the application of the Synthetic Aperture Focusing Technique (SAFT) are: (i) a large divergence of the sound beam of the transducer and (ii) an exact knowledge about the sound propagation path. These requirements are easily fulfilled for point sources directly mounted on the surface of the specimen. In many cases, however, the transducer is wedge mounted and/or coupled using a water delay line, e.g. in immersion technique. These delay lines change the beam index and the propagation path has to be evaluated for each pixel separately considering Fermat's principle. Using phased array transducers, a sector scan can improve the divergence of the sound beam. The introduced method combines the advantages of using a phased array transducer in immersion technique to improve SAFT reconstruction. An algorithm is presented accounting the influence of the delay line on the reconstruction method. The applicability of the algorithm is shown by validation with simulated echo responses and with experimental results collected from a specimen with artificial flaws.
Santos-Villalobos, Hector J; Bingham, Philip R; Gregor, Jens
2013-01-01
The limitations in neutron flux and resolution (L/D) of current neutron imaging systems can be addressed with a Coded Source Imaging system with magnification (xCSI). More precisely, the multiple sources in an xCSI system can exceed the flux of a single pinhole system for several orders of magnitude, while maintaining a higher L/D with the small sources. Moreover, designing for an xCSI system reduces noise from neutron scattering, because the object is placed away from the detector to achieve magnification. However, xCSI systems are adversely affected by correlated noise such as non-uniform illumination of the neutron source, incorrect sampling of the coded radiograph, misalignment of the coded masks, mask transparency, and the imperfection of the system Point Spread Function (PSF). We argue that a model-based reconstruction algorithm can overcome these problems and describe the implementation of a Simultaneous Iterative Reconstruction Technique algorithm for coded sources. Design pitfalls that preclude a satisfactory reconstruction are documented.
Class of backpropagation techniques for limited-angle reconstruction in microwave tomography
Paladhi, P. Roy; Tayebi, A.; Udpa, L.; Udpa, S.; Sinha, A.
2015-03-31
Filtered backpropagation (FBPP) is a well-known technique used in Diffraction Tomography (DT). For accurate reconstruction using FBPP, full 360° angular coverage is necessary. However, it has been shown that using some inherent redundancies in the projection data in a tomographic setup, accurate reconstruction is still possible with 270° coverage which is called the minimal-scan angle range. This can be done by applying weighing functions (or filters) on projection data of the object to eliminate the redundancies and accurately reconstruct the image from 270° coverage. This paper demonstrates procedures to generate many general classes of these weighing filters. These are all equivalent at 270° coverage but vary in performance at lower angular coverages and in presence of noise. This paper does a comparative analysis of different filters when angular coverage is lower than minimal-scan angle of 270°. Simulation studies have been done to find optimum weight filters for sub-minimal angular coverage (<270°)
Clinical low dose CT image reconstruction using high-order total variation techniques
NASA Astrophysics Data System (ADS)
Do, Synho; Karl, W. Clem; Kalra, Mannudeep K.; Brady, Thomas J.; Pien, Homer
2010-04-01
Total variation (TV) based iterative image reconstruction has been shown to possess desirable noise suppression and edge preservation characteristics. However, such approaches also produce "staircase effects" where intensity ramps are discretized into steps, resulting in images which appear blocky or patchy. In this paper, we present an improved regularization technique by incorporating higher-order derivatives to reduce staircase artifacts without sacrificing edge sharpness. In this preliminary investigation we demonstrate our approach using both phantom and clinical images acquired at 25% of conventional radiation dosage (i.e., 75% dose reduction).
CT reconstruction techniques for improved accuracy of lung CT airway measurement
Rodriguez, A.; Ranallo, F. N.; Judy, P. F.; Gierada, D. S.; Fain, S. B.
2014-11-01
Purpose: To determine the impact of constrained reconstruction techniques on quantitative CT (qCT) of the lung parenchyma and airways for low x-ray radiation dose. Methods: Measurement of small airways with qCT remains a challenge, especially for low x-ray dose protocols. Images of the COPDGene quality assurance phantom (CTP698, The Phantom Laboratory, Salem, NY) were obtained using a GE discovery CT750 HD scanner for helical scans at x-ray radiation dose-equivalents ranging from 1 to 4.12 mSv (12–100 mA s current–time product). Other parameters were 40 mm collimation, 0.984 pitch, 0.5 s rotation, and 0.625 mm thickness. The phantom was sandwiched between 7.5 cm thick water attenuating phantoms for a total length of 20 cm to better simulate the scatter conditions of patient scans. Image data sets were reconstructed using STANDARD (STD), DETAIL, BONE, and EDGE algorithms for filtered back projection (FBP), 100% adaptive statistical iterative reconstruction (ASIR), and Veo reconstructions. Reduced (half) display field of view (DFOV) was used to increase sampling across airway phantom structures. Inner diameter (ID), wall area percent (WA%), and wall thickness (WT) measurements of eight airway mimicking tubes in the phantom, including a 2.5 mm ID (42.6 WA%, 0.4 mm WT), 3 mm ID (49.0 WA%, 0.6 mm WT), and 6 mm ID (49.0 WA%, 1.2 mm WT) were performed with Airway Inspector (Surgical Planning Laboratory, Brigham and Women’s Hospital, Boston, MA) using the phase congruency edge detection method. The average of individual measures at five central slices of the phantom was taken to reduce measurement error. Results: WA% measures were greatly overestimated while IDs were underestimated for the smaller airways, especially for reconstructions at full DFOV (36 cm) using the STD kernel, due to poor sampling and spatial resolution (0.7 mm pixel size). Despite low radiation dose, the ID of the 6 mm ID airway was consistently measured accurately for all methods other than STD
NASA Astrophysics Data System (ADS)
Chang, Yuan-Jen
2015-06-01
This study proposed a speckle reduction technique (SRT) that employs a rotating diffuser in the parallel beam optical computed tomography (CT). Results showed that the mean and standard deviation of the gray level are 89.79±4.53 and 89.16±2.88 for reconstruction images without SRT and with SRT, respectively. The proposed SRT effectively removed ring artifacts. In addition, two image processing techniques, namely, the mean and Wiener filters, were also used to improve the reconstructed images. The image processing technique alone effectively reduced ring artifacts, but some fluctuations were still observed in the line profiles of the reconstructed images. Results proved that the proposed SRT is a simple method that is easily implemented to improve image quality for parallel beam optical CT. The combination of SRT and image filters was suggested to achieve the best image reconstruction quality through the full removal of ring artifacts.
NASA Astrophysics Data System (ADS)
Matson, Charles L.; Fox, Marsha; Hege, E. Keith; Hluck, Laura; Drummond, Jack; Harvey, David
1997-05-01
Speckle imaging techniques have been shown to mitigate atmospheric-resolution limits, allowing near-diffraction-limited images to be reconstructed. Few images of extended objects reconstructed by use of these techniques have been published, and most of these results are for relatively bright objects. We present image reconstructions of an orbiting Molniya 3 spacecraft from data collected by use of a 2.3-m ground-based telescope. The apparent brightness of the satellite was 15th visual magnitude. Power-spectrum and bispectrum speckle imaging techniques are used prior to image reconstruction to ameliorate atmospheric blurring. We discuss how these images, although poorly resolved, can be used to provide information on the satellite s functional status. It is shown that our previously published optimal algorithms produce a higher-quality image than do conventional speckle imaging methods.
Dietrich, Olaf; Raya, José G; Reeder, Scott B; Ingrisch, Michael; Reiser, Maximilian F; Schoenberg, Stefan O
2008-07-01
The statistical properties of background noise such as its standard deviation and mean value are frequently used to estimate the original noise level of the acquired data. This requires the knowledge of the statistical intensity distribution of the background signal, that is, the probability density of the occurrence of a certain signal intensity. The influence of many new MRI techniques and, in particular, of various parallel-imaging methods on the noise statistics has neither been rigorously investigated nor experimentally demonstrated yet. In this study, the statistical distribution of background noise was analyzed for MR acquisitions with a single-channel and a 32-channel coil, with sum-of-squares (SoS) and spatial-matched-filter (SMF) data combination, with and without parallel imaging using k-space and image-domain algorithms, with real-part and conventional magnitude reconstruction and with several reconstruction filters. Depending on the imaging technique, the background noise could be described by a Rayleigh distribution, a noncentral chi-distribution or the positive half of a Gaussian distribution. In particular, the noise characteristics of SoS-reconstructed multichannel acquisitions (with k-space-based parallel imaging or without parallel imaging) differ substantially from those with image-domain parallel imaging or SMF combination. These effects must be taken into account if mean values or standard deviations of background noise are employed for data analysis such as determination of local noise levels. Assuming a Rayleigh distribution as in conventional MR images or a noncentral chi-distribution for all multichannel acquisitions is invalid in general and may lead to erroneous estimates of the signal-to-noise ratio or the contrast-to-noise ratio. PMID:18440746
Analysis of sea-level reconstruction techniques for the Arctic Ocean
NASA Astrophysics Data System (ADS)
Svendsen, P. L.; Andersen, O. B.; Nielsen, A. A.
2013-12-01
Sea-level reconstructions spanning several decades have been examined in numerous studies for most of the world's ocean areas, where satellite missions such as TOPEX/Poseidon and Jason-1 and -2 have provided much-improved knowledge of variability and long-term changes in sea level. However, these dedicated oceanographic missions are limited in coverage to between ×66° latitude, and satellite altimeter data at higher latitudes is of a substantially worse quality. Following the approach of Church et al. (2004), we apply a model based on empirical orthogonal functions (EOFs) to the Arctic Ocean, constrained by tide gauge records. A major challenge for this area is the sparsity of both satellite and tide gauge data beyond what can be covered with interpolation, necessitating a time-variable model and consideration to data preprocessing, including selection of appropriate tide gauges. In order to have a reasonable amount of tide gauge data available, we focus on a reconstruction timespan of the last five decades, and the implementation of the model is validated by applying it to global sea-level data. We examine the influence of the individual tide gauges on the resulting solution and the ability of the model to reconstruct known data, in addition to the effects of regularization techniques and the relationship with climatological indices such as the Arctic Oscillation (AO). EOFs are obtained in a preliminary analysis from existing ocean models such as DRAKKAR, and from satellite data (from the ERS-1 and -2 and Envisat missions). In addition to EOFs, we also implement an alternative decomposition technique known as minimum/maximum autocorrelation factors (MAF), based on the spatial or temporal autocorrelation within the calibration period, rather than explained variance.
Study Of Optimal Reconstruction Techniques In The Field Of X-Ray Tomodensitometry Of The Heart
NASA Astrophysics Data System (ADS)
Wetta, P.; Peyrin, F.; Goutte, R.; Amiel, M.
1983-08-01
The computerized-aided tomodensitometry by X-rays is a powerful, precise and non invasive tool to investigate the human body as well as different objects and structures. The relatively long examination time, from 2 to 10 sec., which the present state of the art necessitates, limits the field of applications of this tool here to the static on quasistatic organs or objects (e.g. the brain or abdomen in medical diagnosis). When one try to reconstruct images of a dynamic object some errors or artefacts appear. In the case of the heart, in particular, the examination time takes several cardiac periods; so, the reconstructed image is highly blurred and for all purposes unusable. One solution, which can be used with a conventional scanner is the "gating" technique. Taking into account of the repetitive property of the cardiac movement, this technique necessitates to catch the projections in synchronization with the electrocardiogram. Thus a sub-program, controlled by the ECG sianal, has to select a set of projections corresponding to a certain time of the cardiac period. The implementation of this sub-program into the reconstruction code allows to obtain more sharp images of the heart at any given instant of the cardiac period. In this paper we discuss the methodology used to acquire the projections, the problems caused by the small number of projections, some mathematical solutions (extensions of signals and data, interpolations, uses of the redundancy in the information aiven by a FAN-BEAM system). These different possibilities are illustrated by some results we have obtained in our experiments on animals with a FAN-BEAM machine.
Comparison of deconvolution techniques to measure directional MTF of FDK reconstruction
NASA Astrophysics Data System (ADS)
Lee, Changwoo; Park, Junhan; Ko, Youngjun; Baek, Jongduk
2014-03-01
To measure a spatial resolution of CT scanner, several methods have been developed using bar pattern, wires and thin plates. While these approaches are effective to measure two dimensional MTF, it is not easy to measure directional MTF using those phantoms. To overcome these limitations, Thornton et al. proposed a method to measure directional MTF using sphere phantoms, which is effective only when the cone angle is small. Recently, Baek et al. developed a method to estimate the directional MTF even with a larger cone angle, but the proposed method was analyzed using a noiseless data set. In this work, we present Wiener and Richardson-Lucy deconvolution techniques to estimate the directional MTF, and compare the estimation performance with that of the previous methods (i.e., Thornton's and Baek's methods). To estimate directional MTF, we reconstructed a sphere object centered at (0.01 cm, 0.01 cm, 10.01 cm) using FDK algorithm, and then calculated plane integrals of the reconstructed sphere object and the ideal sphere object. The plane integrals of sphere objects were used to estimate the directional MTF using Wiener and Richardson-Lucy deconvolution techniques. The estimated directional MTF was compared with the ideal MTF calculated from a point object, and showed an excellent agreement.
Rehabilitative techniques for athletes after reconstruction of the anterior cruciate ligament.
Lutz, G E; Stuart, M J; Sim, F H; Scott, S G
1990-10-01
A wide spectrum of protocols is available for rehabilitation after anterior cruciate ligament reconstruction, and little agreement exists on the specifics of strengthening exercises or the sequence of activities. In this article, we discuss the current rehabilitative techniques used at the Mayo Clinic for athletes who have undergone anterior cruciate ligament reconstruction. These techniques are based on established principles of rehabilitation, clinical experience, and new information about the related biomechanics of the knee. An illustrative case reflects the benefits of this rehabilitation program, which lasts up to 1 year and is divided into five stages. The early stages focus on protected mobilization and a strengthening program that emphasizes closed rather than open kinetic chain exercises. Later, neuromuscular-proprioceptive training and sport-specific agility training redevelop the reaction time and the "coordination engrams" necessary for athletic competition. High-quality surgical care and a closely supervised rehabilitation program, based on kinesiologic and biomechanical factors as they pertain to the anterior cruciate ligament, are necessary for a successful outcome. PMID:2214879
Eversion-Inversion Labral Repair and Reconstruction Technique for Optimal Suction Seal
Moreira, Brett; Pascual-Garrido, Cecilia; Chadayamurri, Vivek; Mei-Dan, Omer
2015-01-01
Labral tears are a significant cause of hip pain and are currently the most common indication for hip arthroscopy. Compared with labral debridement, labral repair has significantly better outcomes in terms of both daily activities and athletic pursuits in the setting of femoral acetabular impingement. The classic techniques described in the literature for labral repair all use loop or pass-through intrasubstance labral sutures to achieve a functional hip seal. This hip seal is important for hip stability and optimal joint biomechanics, as well as in the prevention of long-term osteoarthritis. We describe a novel eversion-inversion intrasubstance suturing technique for labral repair and reconstruction that can assist in restoration of the native labrum position by re-creating an optimal seal around the femoral head. PMID:26870648
NASA Astrophysics Data System (ADS)
Choi, Doo-Won; Jeon, Min-Gyu; Cho, Gyeong-Rae; Kamimoto, Takahiro; Deguchi, Yoshihiro; Doh, Deog-Hee
2016-02-01
Performance improvement was attained in data reconstructions of 2-dimensional tunable diode laser absorption spectroscopy (TDLAS). Multiplicative Algebraic Reconstruction Technique (MART) algorithm was adopted for data reconstruction. The data obtained in an experiment for the measurement of temperature and concentration fields of gas flows were used. The measurement theory is based upon the Beer-Lambert law, and the measurement system consists of a tunable laser, collimators, detectors, and an analyzer. Methane was used as a fuel for combustion with air in the Bunsen-type burner. The data used for the reconstruction are from the optical signals of 8-laser beams passed on a cross-section of the methane flame. The performances of MART algorithm in data reconstruction were validated and compared with those obtained by Algebraic Reconstruction Technique (ART) algorithm.
Adaptive noise suppression technique for dense 3D point cloud reconstructions from monocular vision
NASA Astrophysics Data System (ADS)
Diskin, Yakov; Asari, Vijayan K.
2012-10-01
Mobile vision-based autonomous vehicles use video frames from multiple angles to construct a 3D model of their environment. In this paper, we present a post-processing adaptive noise suppression technique to enhance the quality of the computed 3D model. Our near real-time reconstruction algorithm uses each pair of frames to compute the disparities of tracked feature points to translate the distance a feature has traveled within the frame in pixels into real world depth values. As a result these tracked feature points are plotted to form a dense and colorful point cloud. Due to the inevitable small vibrations in the camera and the mismatches within the feature tracking algorithm, the point cloud model contains a significant amount of misplaced points appearing as noise. The proposed noise suppression technique utilizes the spatial information of each point to unify points of similar texture and color into objects while simultaneously removing noise dissociated with any nearby objects. The noise filter combines all the points of similar depth into 2D layers throughout the point cloud model. By applying erosion and dilation techniques we are able to eliminate the unwanted floating points while retaining points of larger objects. To reverse the compression process, we transform the 2D layer back into the 3D model allowing points to return to their original position without the attached noise components. We evaluate the resulting noiseless point cloud by utilizing an unmanned ground vehicle to perform obstacle avoidance tasks. The contribution of the noise suppression technique is measured by evaluating the accuracy of the 3D reconstruction.
Characterization of high resolution MR images reconstructed by a GRAPPA based parallel technique
NASA Astrophysics Data System (ADS)
Banerjee, Suchandrima; Majumdar, Sharmila
2006-03-01
This work implemented an auto-calibrating parallel imaging technique and applied it to in vivo magnetic resonance imaging (MRI) of trabecular bone micro-architecture. A Generalized auto-calibrating partially parallel acquisition (GRAPPA) based reconstruction technique using modified robust data fitting was developed. The MR data was acquired with an eight channel phased array receiver on three normal volunteers on a General Electric 3 Tesla scanner. Microstructures comprising the trabecular bone architecture are of the order of 100 microns and hence their depiction requires very high imaging resolution. This work examined the effects of GRAPPA based parallel imaging on signal and noise characteristics and effective spatial resolution in high resolution (HR) images, for the range of undersampling or reduction factors 2-4. Additionally quantitative analysis was performed to obtain structural measures of trabecular bone from the images. Image quality in terms of contrast and depiction of structures was maintained in parallel images for reduction factors up to 3. Comparison between regular and parallel images suggested similar spatial resolution for both. However differences in noise characteristics in parallel images compared to regular images affected the threshholding based quantification. This suggested that GRAPPA based parallel images might require different analysis techniques. In conclusion, the study showed the feasibility of using parallel imaging techniques in HR-MRI of trabecular bone, although quantification strategies will have to be further investigated. Reduction of acquisition time using parallel techniques can improve the clinical feasibility of MRI of trabecular bone for prognosis and staging of the skeletal disorder osteoporosis.
Ferrari, Silvano; Ferri, Andrea; Bianchi, Bernardo; Copelli, Chiara; Magri, Alice Sara; Sesenna, Enrico
2009-01-01
Reconstruction of cheek mucosa defects following tumor resections can be approached with several techniques, depending on size of the defect. Fasciocutaneous and perforators free flaps are widely employed today for such reconstructions. However, small defects or general health of the patient may limit their indications. Furthermore, approaching moderate size defects, some techniques, like temporalis muscle or fascia pedicled flaps, lead to contracture with limitation of mouth opening or trisma, and others, like intraoral local flaps, do not provide enough tissue for the reconstructions. In this work the authors propose, for reconstructing these kind of defects, the use of a buccinator myomucosal island flap and a buccal fat pad pedicled flap association. A case is reported and the surgical technique is explained. This new reconstructive technique can easily be used for reconstructing moderate-sized cheek defects, achieving optimal results: the internal mucosal lining is restored in few weeks without any retraction, contracture, of scars on the face limiting the aesthetic outcome and mouth opening. PMID:18620893
Computerized tomography technique for reconstruction of obstructed phase data in shearography.
Hung, Y Y; Huang, Y H; Liu, L; Ng, S P; Chen, Y S
2008-06-10
Shearography is an interferometric method that overcomes several limitations of holography by eliminating the reference beam. It greatly simplifies the optical setup and has much higher tolerance to environmental disturbances. Consequently, the technique has received considerable industrial acceptance, particularly for nondestructive testing. Shearography, however, is generally not applicable to the measurement of an obstructed area, as the area to be measured must be accessible to both illumination and imaging. We present an algorithm based on the principle of tomography that permits the reconstruction of the unavailable phase distribution in an obstructed area from the measured boundary phase distribution. In the process, a set of imaginary rays is projected from many different directions across the area. For each ray, integration of the phase directional derivative along the ray is equal to the phase difference between the boundary points intercepted by the ray. Therefore, a set of linear equations can be established by considering the multiple rays. Each equation expresses the unknown phase derivatives in the obstructed area in terms of the measured boundary phase. Solution of the set of simultaneous equations yields the unknown phase distribution in the blind area. While its applications to shearography are demonstrated, the technique is potentially applicable to all full-field optical measurement techniques such as holography, speckle interferometry, classical interferometry, thermography, moiré, photoelasticity, and speckle correlation techniques. PMID:18545289
Applications of the Medipix3-CT in combination with iterative reconstruction techniques
NASA Astrophysics Data System (ADS)
Fischer, F.; Procz, S.; Fauler, A.; Fiederle, M.
2016-02-01
The pixelated semiconductor detectors of the Medipix family with their photon-counting abilities offer the possibility of high quality X-ray radiography as well as computed tomography. The generated signal from each photon is amplified and shaped before it is compared to an energy threshold. For a photon with an energy above the threshold the counter is incremented by one count. Photons below the operator-defined threshold do not increment the counter and therefore do not participate in the image formation. Furthermore, compared to other detectors like scintillators, an additional conversion step is dispensed due to the direct converting nature of photon-counting detectors, leading to a higher signal-to-noise-ratio. Additionally, the photon processing capabilities of photon-counting detectors allow photons to be weighted equally and not proportional to their energy as it is the case for charge integrating devices, where high energy photons are weighted stronger than low energy photons. Compared to integrating devices, this leads to an increase in contrast for images of both high and low contrast objects, hence improve object information. The use of photon-counting detectors in combination with iterative reconstruction techniques based on OSEM (ordered subset expectation maximization) algorithms is the basis of our computed tomography scans for material analysis. Due to its ability to operate with highly undersampled data sets, iterative reconstruction offers the possibility to decrease dose in CT scans. In order to identify the limits of the data set reduction, a first series of scans was performed to test, under real conditions, the CT-image quality when a strongly reduced amount of projections is used for reconstruction. In addition, the effect of a total variation minimization tool on these undersampled data sets was evaluated. Furthermore, this paper includes a number of recent CT-results with scans performed at two different setups within our facility.
COMPLICATIONS OF THE SCREW/WASHER TIBIAL FIXATION TECHNIQUE FOR KNEE LIGAMENT RECONSTRUCTION
Almeida, Alexandre; Roveda, Gilberto; Valin, Márcio Rangel; Almeida, Nayvaldo Couto de; Sartor, Vanderlei; Alves, Soraya Melina
2015-01-01
To evaluate the presence of pain at the site of the surgical incision and the need to remove the tibial fixation screw in anterior cruciate ligament (ACL) reconstruction, in relation to sex and body mass index (BMI). Methods: A group of 265 patients who underwent ACL reconstruction with ipsilateral flexor tendon grafts from the thigh in which the tibial fixation technique consisted of using a cortical screw and metal washer, between July 2000 and November 2007, were evaluated. Results: 176 patients were evaluated for an average of 33.3 ± 19.5 months; median of 29.5 months; IIQ: 17-45 months; minimum of 8 and maximum of 87 months. There was no statistical difference regarding complaints of pain at the site of the screw (p = 0.272) and the need to remove the tibial screw (p = 0.633) between sexes. There was no statistical difference regarding complaints of pain at the site of the screw (p = 0.08) and the need to remove the tibial screw (p = 0.379) according to BMI. Conclusion: The pain complaint rate at the screw site from the screw and metal washer method used for tibial fixation in ACL reconstruction was of the order of 25%, and the screw had to be removed in 10.8% of the cases. There was no predominance of pain complaints at the surgical wound between the sexes. There was a greater tendency to complain about pain among patients with BMI < 25. There was no predominance of screw and washer removal between the sexes or between individuals with different BMIs. PMID:27022587
ERIC Educational Resources Information Center
Glick, David
1995-01-01
Presents a technique that helps students concentrate more on the science and less on the mechanics of algebra while dealing with introductory physics formulas. Allows the teacher to do complex problems at a lower level and not be too concerned about the mathematical abilities of the students. (JRH)
NASA Astrophysics Data System (ADS)
Perry, Abigail; Sugawa, Seiji; Salces-Carcoba, Francisco; Spielman, Ian
2014-05-01
We report on an experiment reconstructing the column-density of a Bose-Einstein condensate using differently defocused images from multiple cameras. Starting with defocused images taken off-resonance, a transfer function with a ``not-quite invertible'' relationship exists, going from the optical depth observed at the camera to the focused column density [L.D. Turner et al., Opt. Lett., 29(3) 232-234 (2004)]. Adding additional defocused detectors allows us to fully reconstruct the focused image, and more advanced techniques allow us to reconstruct both the amplitude and phase of the electromagnetic wave at the image planes.
Nestle-Krämling, Carolin; Bölke, Edwin; Budach, Wilfried; Andree, Christoph
2016-01-01
Neoadjuvant radio chemotherapy and immediate reconstruction for breast cancer are still under debate. But there are recent abstracts and articles which show that neoadjuvant radio chemotherapy is feasible and could improve the clinical outcome of breast cancer patients. The aim of this review is to present the authors' techniques and approaches with regard to neoadjuvant radiation of breast cancer patients. It seems that the concept of immediate implant delayed autologous breast reconstruction could be a safe procedure that is at least equivalent to primary autologous reconstruction. PMID:27287332
An optimal technique for constraint-based image restoration and reconstruction
NASA Astrophysics Data System (ADS)
Leahy, Richard M.; Goutis, Costas E.
1986-12-01
A new technique for finding an optimal feasible solution to the general image reconstruction and restoration problem is described. This method allows the use of prior knowledge of the properties of both the solution and any noise present on the data. The problem is formulated as the optimization of a cost function over the intersection of a number of convex constraint sets; each set being defined as containing those solutions consistent with a particular constraint. A duality theorem is then applied to yield a dual problem in which the unknown image is replaced by a model defined in terms of a finite dimensional parameter vector and the kernels of the inteegral equations relating the data and solution. The dual problem may then be solved for the model parameters using a gradient descent algorithm. This method serves as an alternative to the primal constrained optimization and projection onto convex sets (POCS) algorithms. Problems in which this new approach is appropriate are discussed. An example is given for image reconstruction from noisy projection data; applying the dual method results in a fast nonlinear algorithm. Simulation results demonstrate the superiority of the optimal feasible solution over one obtained using a suboptimal approach.
Millett, Peter J; Braun, Sepp; Gobezie, Reuben; Pacheco, Iván H
2009-01-01
Background Symptomatic Acromioclavicular (AC) dislocations have historically been surgically treated with Coracoclavicular (CC) ligament reconstruction with transfer of the Coracoacromial (CA) ligament. Tensioning the CA ligament is the key to success. Methods Seventeen patients with chronic, symptomatic Type III AC joint or acute Type IV and V injuries were treated surgically. The distal clavicle was resected and stabilized with CC ligament reconstruction using the CA ligament. The CA ligament was passed into the medullary canal and tensioned, using a modified 'docking' technique. Average follow-up was 29 months (range 12–57). Results Postoperative ASES and pain significantly improved in all patients (p = 0.001). Radiographically, 16 (94%) maintained reduction, and only 1 (6%) had a recurrent dislocation when he returned to karate 3 months postoperatively. His ultimate clinical outcome was excellent. Conclusion The docking procedure allows for tensioning of the transferred CA ligament and healing of the ligament in an intramedullary bone tunnel. Excellent clinical results were achieved, decreasing the risk of recurrent distal clavicle instability. PMID:19144190
Reconstruction of the elbow and forearm for Ewing sarcoma of ulna: A new biological technique
Puri, Ajay; Gulia, Ashish; Byregowda, Suman; Ramanujan, Vishnu
2016-01-01
Primary bone tumors around the elbow represent <1% of all the skeletal tumors. Surgery with or without adjuvant therapy (radiotherapy, chemotherapy) is the treatment of choice for malignant tumors. Reconstruction of the elbow and forearm in malignant tumors is challenging as it involves a complex interplay between multiple joints which need to be stabilized for the optimal functional outcome. We describe a new technique for the reconstruction of the elbow after resection of a proximal ulna tumor with articular radio-ulnar synostosis with the creation of a single bone forearm. We attempted to achieve a mobile elbow and stable wrist joint with the radio-ulnar union at the proximal articular surface of the ulna resulting in a single bone forearm. The procedure involves an oblique osteotomy preserving the olecranon process (after taking adequate margins based on oncological principles) and its articular cartilage along with the attachment of the triceps tendon. Then the radial head was partially denuded of its cartilage using a burr, leaving cartilage only on the volar side, and then fused to the remnant olecranon. Osteosynthesis was done using compression screw and tension band wiring. The advantages of this procedure are that the mobility at wrist and elbow are retained, it requires minimal hardware and allows for primary closure of the wound. PMID:27186061
NASA Astrophysics Data System (ADS)
Gómez-Gutiérrez, Álvaro; Susanne, Schnabel; Conoscenti, Christian; Caraballo-Arias, Nathalie A.; Ferro, Vito; di Stefano, Constanza; Juan de Sanjosé, José; Berenguer-Sempere, Fernando; de Matías, Javier
2014-05-01
Recent developments made in tri-dimensional photo-reconstruction techniques (3D-PR), such as the use of Structure from Motion (SfM) and MultiView Stereo (MVS) techniques together, have allowed obtaining high resolution 3D point clouds. In order to achieve final point clouds with these techniques, only oblique images from consumer un-calibrated and non-metric cameras are needed. Here, these techniques are used in order to measure, monitor and quantify geomorphological features and processes. Three different applications through a range of scales and landforms are presented here. Firstly, five small gully headcuts located in a small catchment in SW Spain were monitored with the aim of estimating headcut retreat rates. During this field work, 3D models obtained by means of a Terrestrial Laser Scanner (TLS) were captured and used as benchmarks to analyze 3D-PR method accuracy. Results of this analysis showed centimeter-level accuracies with average distances between the 3D-PR model and the TLS model ranging from 0.009 to 0.025 m. Estimated soil loss ranged from -0.246 m3 to 0.114 m3 for a wet period (289 mm) of 54 days in 2013. Secondly, a calanchi type badland in Sicily (Italy) was photo-reconstructed and the quality of the 3D-PR model was analyzed using a Digital Elevation Model produced by classic digital photogrammetry with photos captured by an Unmanned Aerial Vehicle (UAV). In this case, sub-meter calculated accuracies (0.30) showed that it is possible to describe badland morphology using 3D-PR models but it is not feasible to use these models to quantify annual rates of soil erosion in badlands (10 mm eroded per year). Finally, a high-resolution model of the Veleta rock glacier (in SE Spain) was elaborated with 3D-PR techniques and compared with a 3D model obtained by means of a TLS. Results indicated that 3D-PR method can be applied to the micro-scale study of glacier morphologies and processes with average distances to the TLS point cloud of 0.21 m.
Rozen, Warren Matthew; Spychal, Robert T.; Hunter-Smith, David J.
2016-01-01
Background Accurate volumetric analysis is an essential component of preoperative planning in both reconstructive and aesthetic breast procedures towards achieving symmetrization and patient-satisfactory outcome. Numerous comparative studies and reviews of individual techniques have been reported. However, a unifying review of all techniques comparing their accuracy, reliability, and practicality has been lacking. Methods A review of the published English literature dating from 1950 to 2015 using databases, such as PubMed, Medline, Web of Science, and EMBASE, was undertaken. Results Since Bouman’s first description of water displacement method, a range of volumetric assessment techniques have been described: thermoplastic casting, direct anthropomorphic measurement, two-dimensional (2D) imaging, and computed tomography (CT)/magnetic resonance imaging (MRI) scans. However, most have been unreliable, difficult to execute and demonstrate limited practicability. Introduction of 3D surface imaging has revolutionized the field due to its ease of use, fast speed, accuracy, and reliability. However, its widespread use has been limited by its high cost and lack of high level of evidence. Recent developments have unveiled the first web-based 3D surface imaging program, 4D imaging, and 3D printing. Conclusions Despite its importance, an accurate, reliable, and simple breast volumetric analysis tool has been elusive until the introduction of 3D surface imaging technology. However, its high cost has limited its wide usage. Novel adjunct technologies, such as web-based 3D surface imaging program, 4D imaging, and 3D printing, appear promising. PMID:27047788
Matros, Evan; Albornoz, Claudia R; Rensberger, Michael; Weimer, Katherine; Garfein, Evan S
2014-06-01
There is increased clinical use of computer-assisted design (CAD) and computer-assisted modeling (CAM) for osseous flap reconstruction, particularly in the head and neck region. Limited information exists about methods to optimize the application of this new technology and for cases in which it may be advantageous over existing methods of osseous flap shaping. A consecutive series of osseous reconstructions planned with CAD/CAM over the past 5 years was analyzed. Conceptual considerations and refinements in the CAD/CAM process were evaluated. A total of 48 reconstructions were performed using CAD/CAM. The majority of cases were performed for head and neck tumor reconstruction or related complications whereas the remainder (4%) were performed for penetrating trauma. Defect location was the mandible (85%), maxilla (12.5%), and pelvis (2%). Reconstruction was performed immediately in 73% of the cases and delayed in 27% of the cases. The mean number of osseous flap bone segments used in reconstruction was 2.41. Areas of optimization include the following: mandible cutting guide placement, osteotomy creation, alternative planning, and saw blade optimization. Identified benefits of CAD/CAM over current techniques include the following: delayed timing, anterior mandible defects, specimen distortion, osteotomy creation in three dimensions, osteotomy junction overlap, plate adaptation, and maxillary reconstruction. Experience with CAD/CAM for osseous reconstruction has identified tools for technique optimization and cases where this technology may prove beneficial over existing methods. Knowledge of these facts may contribute to improved use and main-stream adoption of CAD/CAM virtual surgical planning by reconstructive surgeons. PMID:24323480
Single-Particle Reconstruction Using L2-Gradient Flow
Li, Ming; Xu, Guoliang; Sorzano, Carlos O. S.; Sun, Fei; Bajaj, Chandrajit L.
2011-01-01
In this paper, we present an iterative algorithm for reconstructing a three-dimensional density function from a set of two dimensional electron microscopy images. By minimizing an energy functional consisting of a fidelity term and a regularization term, an L2-gradient flow is derived. The flow is integrated by a finite element method in the spatial direction and an explicit Euler scheme in the temporal direction. Our method compares favourably with those of the weighted back projection, Fourier method, algebraic reconstruction technique and simultaneous iterative reconstruction technique. PMID:21864687
WE-G-18C-08: Real Time Tumor Imaging Using a Novel Dynamic Keyhole MRI Reconstruction Technique
Lee, D; Pollock, S; Whelan, B; Keall, P; Greer, P; Kim, T
2014-06-15
Purpose: To test the hypothesis that the novel Dynamic Keyhole MRI reconstruction technique can accelerate image acquisition whilst maintaining high image quality for lung cancer patients. Methods: 18 MRI datasets from 5 lung cancer patients were acquired using a 3T MRI scanner. These datasets were retrospectively reconstructed using (A) The novel Dynamic Keyhole technique, (B) The conventional keyhole technique and (C) the conventional zero filling technique. The dynamic keyhole technique in MRI refers to techniques in which previously acquired k-space data is used to supplement under sampled data obtained in real time. The novel Dynamic Keyhole technique utilizes a previously acquired a library of kspace datasets in conjunction with central k-space datasets acquired in realtime. A simultaneously acquired respiratory signal is utilized to sort, match and combine the two k-space streams with respect to respiratory displacement. Reconstruction performance was quantified by (1) comparing the keyhole size (which corresponds to imaging speed) required to achieve the same image quality, and (2) maintaining a constant keyhole size across the three reconstruction methods to compare the resulting image quality to the ground truth image. Results: (1) The dynamic keyhole method required a mean keyhole size which was 48% smaller than the conventional keyhole technique and 60% smaller than the zero filling technique to achieve the same image quality. This directly corresponds to faster imaging. (2) When a constant keyhole size was utilized, the Dynamic Keyhole technique resulted in the smallest difference of the tumor region compared to the ground truth. Conclusion: The dynamic keyhole is a simple and adaptable technique for clinical applications requiring real-time imaging and tumor monitoring such as MRI guided radiotherapy. Based on the results from this study, the dynamic keyhole method could increase the imaging frequency by a factor of five compared with full k
Petit, J; Rietjens, M; Garusi, C
2001-06-01
Breast reconstruction is considered as part of the breast cancer treatment when a mastectomy is required. The techniques available today, allow reconstruction of the breast even in almost all the cases even in poor local conditions. In 60-70% of the cases, the reconstruction can be performed with an implant inserted behind the pectoralis muscle. Special implants called expanders, are inflatable progressively in the postoperative course thanks to a reservoir located subcutaneously. They provide a progressive distention of the teguments and a more natural shape after substitution of the expander with a definitive implant. The symmetry is usually obtained thanks to a contralateral plastic surgery, which allows at the same time histological check up of the glandular tissue of the opposite breast. The nipple areolar complex is usually reconstructed in a second stage under local anesthesia, using local flaps for the nipple and a tattoo for the colour of the areola. In 30% of the cases, especially after radiotherapy when a salvage mastectomy is required, a flap reconstruction is preferred. The autologous tissue reconstruction with the rectus myocutaneous flap gives excellent cosmetic results and the most natural shape for the breast. But it is a more demanding technique requiring a good experience. In some occasions, the reconstruction with the latissimus flap can also be autologous but usually requires the addition of prosthesis. In most cases, the reconstruction can be performed immediately. The delayed reconstruction is usually preferred when the adjuvant chemotherapy should be delivered as soon as possible after the mastectomy. Complications of the reconstruction such as local necrosis or infections, leading to implant removal or revision of the flap could be detrimental to the patient in delaying the start of the chemotherapy. It is not recommended to reconstruct the breast immediately in case of locally advanced breast cancer. Partial breast reconstruction using
Jordan, D.R.; Tse, D.T.; Anderson, R.L.; Hansen, S.O. )
1990-01-01
Reconstruction of full thickness eyelid defects requires the correction of both posterior lamella (tarsus, conjunctiva) and anterior lamella (skin, muscle). Tarsal substitutes including banked sclera, nasal cartilage, ear cartilage, and periosteum can be beneficial for posterior lamellar repair, while anterior lamellar replacement, including skin grafts, pedicle flaps, advancement flaps, etc., is important to cover the posterior reconstructed portion. At times, due to extensive tissue loss, the eyelid reconstruction can be particularly challenging. We have found an alternative posterior lamellar reconstructive technique utilizing irradiated homologous tarsal plate that can be particularly useful in selected cases of severe tissue loss. The experimental surgical procedure in monkeys and the histological fate of the implanted tarsus is described in Part I, and followed in Part II by our experience with this tissue in six human patients.
Pellegrini, Manuel J; Adams, Samuel B; Parekh, Selene G
2014-06-24
Chronic peroneal tendinopathy and tears represent a challenging clinical situation. Traditionally, tenodesis of the torn tendon to the remaining healthy tendon has been advocated if more than half of the tendon is compromised. Allograft reconstructions have been reserved for patients with functional muscles and both peroneal tendons extensively compromised. We report a unique case of a peroneal tenodesis takedown and reconstruction of both peroneal tendons using semitendinosus allograft. A description of the surgical technique and tips are provided. Peroneal tendon function is crucial to maintain a balanced hindfoot. To the best of our knowledge, reconstruction of both peroneal tendons after a tenodesis has not been previously reported. Allograft reconstruction of the peroneal tendons arises as a feasible alternative in patients with residual pain and weakness after a failed tenodesis surgery LEVELS OF EVIDENCE: Therapeutic Level IV, case study. PMID:24962697
Mathes, David W; Neligan, Peter C
2010-01-01
Perforator-based microsurgical reconstruction of the breast has steadily increased since the introduction of the technique in the 1990s. The procedure appears to offer less postoperative pain, lower abdominal morbidity, and better preservation of the rectus muscles than the more conventional flaps. However, the major disadvantage of these flaps that they can be difficult to harvest, resulting in a longer operative times. The challenges in flap dissection are a result of the variability in the vascular anatomy of the deep inferior epigastric artery (DIEA) and its perforating branches through the rectus muscle. The location, number, and caliber of the perforators and the intramuscular trajectory of the DIEA branches vary greatly not only from individual to individual, but from one hemiabdomen to the other. The establishment of a presurgical map of the vessels on the abdomen facilitates surgical planning and may decrease operating room time, reduce intraoperative complications, and possibly improve outcomes. This article reviews the available techniques for preoperative planning with the currently available imaging modalities of handheld Doppler, color Doppler (duplex) ultrasound, computed tomography angiography, and magnetic resonance angiography. PMID:20024888
Enhancement of multi-pass 3D circular SAR images using sparse reconstruction techniques
NASA Astrophysics Data System (ADS)
Ferrara, Matthew; Jackson, Julie A.; Austin, Christian
2009-05-01
This paper demonstrates image enhancement for wide-angle, multi-pass three-dimensional SAR applications. Without sufficient regularization, three-dimensional sparse-aperture imaging from realistic data-collection scenarios results in poor quality, low-resolution images. Sparsity-based image enhancement techniques may be used to resolve high-amplitude features in limited aspects of multi-pass imagery. Fusion of the enhanced images across multiple aspects in an approximate GLRT scheme results in a more informative view of the target. In this paper, we apply two sparse reconstruction techniques to measured data of a calibration top-hat and of a civilian vehicle observed in the AFRL publicly-released 2006 Circular SAR data set. First, we employ prominent-point autofocus in order to compensate for unknown platform motion and phase errors across multiple radar passes. Each sub-aperture of the autofocused phase history is digitally-spotlighted (spatially low-pass filtered) to eliminate contributions to the data due to features outside the region of interest, and then imaged with l1-regularized least squares and CoSaMP. The resulting sparse sub-aperture images are non-coherently combined to obtain a wide-angle, enhanced view of the target.
El Omari, Mounia; El Mazouz, Samir; Gharib, Noureddine; EL Abbassi, Abdallah
2015-01-01
Les sourcils jouent un rôle important dans l’équilibre esthétique du visage. Leur reconstruction ou ophriopoïése, après séquelle de brûlure fait partie intégrante du programme de réhabilitation de la face brûlée. Plusieurs techniques ont été décrites. Nous insistons ici sur l'intérêt d'une technique simple, à la portée de tous les chirurgiens, et dont la méthode et les résultats peuvent être améliorés par un dessin bien planifié des zones donneuse et receveuse: la greffe composite prélevée au niveau du cuir chevelu dessinée à l'aide d'un calque du sourcil controlatéral. PMID:26401195
NASA Astrophysics Data System (ADS)
Chang, Jenghwa; Graber, Harry L.; Barbour, Randall L.
1995-05-01
This study reports on results of our efforts to improve the efficiency and stability of previously developed reconstruction algorithms for optical diffusion tomography. The previous studies, which applied regularization and a priori contraints to iterative methods--POCS, CGD, and SART algorithms--showed that in most cases, good quality reconstructions of simply structured media were achievalbe using a perturbation model. The CGD method, which is the most efficient of the three algorithms, was, however, in some instances not able to produce good quality images because of the difficulty in applying range constraints, which can cause divergence. In this study, a scheme is proposed to detect this gradient vector is reset and the CGD reconstruction is restarted using the previous reconstruction as the initial value. In gradient vector is reset and the CGD reconstruction is restarted using the previous reconstruction as the initial value. In addition, a rescaling technique, which rescaled the weight matrix to make it more uniform and less ill-conditioned, is also used to suppress numerical errors and accelerate convergence. Two criteria, rescaling the maximum of each column to 1 and rescaling the average of each column to 1, were applied and compared to results without rescaling. The results show that, with properly imposed constraints, good quality images can be obtained using the CGD method. The convergence speed is much slower when constraints are imposed, but still comparable to the POCS and SART algorithms, The rescaling technique produces more stable and more accurate reconstructions, and speeds up the reconstruction significantly for all three algorithms.
Nasirudin, Radin A.; Mei, Kai; Panchev, Petar; Fehringer, Andreas; Pfeiffer, Franz; Rummeny, Ernst J.; Fiebich, Martin; Noël, Peter B.
2015-01-01
Purpose The exciting prospect of Spectral CT (SCT) using photon-counting detectors (PCD) will lead to new techniques in computed tomography (CT) that take advantage of the additional spectral information provided. We introduce a method to reduce metal artifact in X-ray tomography by incorporating knowledge obtained from SCT into a statistical iterative reconstruction scheme. We call our method Spectral-driven Iterative Reconstruction (SPIR). Method The proposed algorithm consists of two main components: material decomposition and penalized maximum likelihood iterative reconstruction. In this study, the spectral data acquisitions with an energy-resolving PCD were simulated using a Monte-Carlo simulator based on EGSnrc C++ class library. A jaw phantom with a dental implant made of gold was used as an object in this study. A total of three dental implant shapes were simulated separately to test the influence of prior knowledge on the overall performance of the algorithm. The generated projection data was first decomposed into three basis functions: photoelectric absorption, Compton scattering and attenuation of gold. A pseudo-monochromatic sinogram was calculated and used as input in the reconstruction, while the spatial information of the gold implant was used as a prior. The results from the algorithm were assessed and benchmarked with state-of-the-art reconstruction methods. Results Decomposition results illustrate that gold implant of any shape can be distinguished from other components of the phantom. Additionally, the result from the penalized maximum likelihood iterative reconstruction shows that artifacts are significantly reduced in SPIR reconstructed slices in comparison to other known techniques, while at the same time details around the implant are preserved. Quantitatively, the SPIR algorithm best reflects the true attenuation value in comparison to other algorithms. Conclusion It is demonstrated that the combination of the additional information from
Reduction in radiation dose with reconstruction technique in the brain perfusion CT
NASA Astrophysics Data System (ADS)
Kim, H. J.; Lee, H. K.; Song, H.; Ju, M. S.; Dong, K. R.; Chung, W. K.; Cho, M. S.; Cho, J. H.
2011-12-01
The principal objective of this study was to verify the utility of the reconstruction imaging technique in the brain perfusion computed tomography (PCT) scan by assessing reductions in the radiation dose and analyzing the generated images. The setting used for image acquisition had a detector coverage of 40 mm, a helical thickness of 0.625 mm, a helical shuttle mode scan type and a rotation time of 0.5 s as the image parameters used for the brain PCT scan. Additionally, a phantom experiment and an animal experiment were carried out. In the phantom and animal experiments, noise was measured in the scanning with the tube voltage fixed at 80 kVp (kilovolt peak) and the level of the adaptive statistical iterative reconstruction (ASIR) was changed from 0% to 100% at 10% intervals. The standard deviation of the CT coefficient was measured three times to calculate the mean value. In the phantom and animal experiments, the absorbed dose was measured 10 times under the same conditions as the ones for noise measurement before the mean value was calculated. In the animal experiment, pencil-type and CT-dedicated ionization chambers were inserted into the central portion of pig heads for measurement. In the phantom study, as the level of the ASIR changed from 0% to 100% under identical scanning conditions, the noise value and dose were proportionally reduced. In our animal experiment, the noise value was lowest when the ASIR level was 50%, unlike in the phantom study. The dose was reduced as in the phantom study.
Volpi, Piero; Cervellin, Matteo; Denti, Matteo; Bait, Corrado; Melegati, Gianluca; Quaglia, Alessandro; de Girolamo, Laura
2010-11-01
The single-bundle ACL reconstruction ensures good outcomes and it is a well-established and widespread technique. Nevertheless, some patients still present residual pain and instability. Recent studies have showed that the double-bundle technique restores better natural ACL-fitting kinematics. Long-term clinical studies comparing the two surgical techniques are not frequent and there is no instrument to evaluate function and kinematics during the knee rotation in vivo. In this randomised prospective study performed on sportive people, we compare the BPTB single-bundle ACL reconstruction technique, which is the most common surgical technique performed on these patients' category, with the ACL double-bundle reconstruction technique (DB), in order to evaluate possible differences between the groups. Comparing the two groups, no statistically significant difference regarding the post-operative Lysholm score (p=0.368) the Tegner activity scale (p=0.519) and the arthrometric evaluation with KT-1000 (p=0.74) have been observed. On the contrary, the IKDC evaluation showed a statistically significant difference (p=0.004) better results of the DB group. Moreover, as assessed by the Tegner activity scale, only patients of the DB group were able to return to sports at a pre-injury level. Our data suggest that the double bundle ST/G ACL reconstruction technique results into slightly better outcome than the traditional technique of single-bundle BPTB. The verification and quantification of the advantages of this technique is anticipated with future studies focusing to the accurate measurement of knee rotation during different activities. PMID:20934698
Lee, H.-R.; DaSilva, L.; Haddad, L.; Trebes, J.; Yeh, Y.; Ford, G.
1995-06-14
The Iterative Optimizing Quantization Technique (IOQT) is a novel method in reconstructing three-dimensional images from a limited number of two-dimensional projections. IOQT reduces the artifacts and image distortion due to a limited number of projections and limited range of viewing angles. IOQT, which reduces the number of projections required for reconstruction, can simplify the complexity of an experimental set-up and support the development of techniques to nondestructively image microstructures of materials without the problems of chemical changes or damage. In this paper, we will demonstrate the capability of IOQT in reconstruction of an image from four projections. The advantage of IOQT in using a limited number of arbitrary-angled projections and the possibility of modification of IOQT are also mentioned.
Nanomaterial characterization through image treatment, 3D reconstruction and AI techniques
NASA Astrophysics Data System (ADS)
Lopez de Uralde Huarte, Juan Jose
Nanotechnology is not only the science of the future, but it is indeed the science of today. It is used in all sectors, from health to energy, including information technologies and transport. For the present investigation, we have taken carbon black as a use case. This nanomaterial is mixed with a wide variety of materials to improve their properties, like abrasion resistance, tire and plastic wear or tinting strength in pigments. Nowadays, indirect methods of analysis, like oil absorption or nitrogen adsorption are the most common techniques of the nanomaterial industry. These procedures measure the change in the physical state while adding oil and nitrogen. In this way, the superficial area is estimated and related with the properties of the material. Nevertheless, we have chosen to improve the existent direct methods, which consist in analysing microscopy images of nanomaterials. We have made progress in the image processing treatments and in the extracted features. In fact, some of them have overcome the existing features in the literature. In addition, we have applied, for the first time in the literature, machine learning to aggregate categorization. In this way, we identify automatically their morphology, which will determine the final properties of the material that is mixed with. Finally, we have presented an aggregate reconstruction genetic algorithm that, with only two orthogonal images, provides more information than a tomography, which needs a lot of images. To summarize, we have improved the state of the art in direct analysing techniques, allowing in the near future the replacement of the current indirect techniques.
The Selective Image Reconstruction (SIR) Imaging Technique: Applications to Planetary Science
NASA Astrophysics Data System (ADS)
Hale, A. S.; Dantowitz, R.; Kozubel, M.; Teare, S.; Gillam, S. G.
2001-11-01
Adaptive optics systems have greatly increased the spatial resolutions achievable from the ground, but require extensive initial engineering and expense to be made workable. Other techniques focused on correcting only the major components of the seeing, such as shift-and-add (SAA) have had great success in increasing the resolution achievable from the ground without such initial effort. An improvement of the traditional shift and add technique is selective image reconstruction (SIR) (Dantowitz, 1998; Dantowitz et al., 2000; Baldwin et al. 2001) in which only those images taken at moments of perfect or near perfect seeing are added together to produce the final image. SIR can yield diffraction limited images when applied on a telescope with good optics and good natural seeing (Dantowitz et al. 2000), and is especially well suited to smaller aperture telescopes (Dantowitz 1998). Though this technique is more complicated to apply to extended objects than to point sources, it has been successfully applied to Mercury (Dantowitz et al., 2000) as well as other solar system, and has great potential for high spatial resolution studies of solar system objects. We present results from a September observing run at Mount Wilson Observatory's 60 inch telescope, and discuss planned improvements in instrumentation and future possibilities for solar system science. This work is supported by the Mount Wilson Institute and the National Research Council. Baldwin, J. E.; Tubbs, R. N.; Cox, G. C.; Mackay, C. D.; Wilson, R. W.; Andersen, M. I., 2001, A&A 368, L1. Dantowitz, R. 1998 Sky and Tel. 96, 48. Dantowitz, R.; Teare, S.; Kozubal, M. 2000. AJ, 119, 2455.
White, Brian J.; Herzog, Mackenzie M.
2016-01-01
Labral repair has been shown to be an effective treatment option with excellent early outcomes; however, in cases of severe labral damage or when the labral tissue is too large or diminutive, labral repair may be less effective. The purpose of this article is to present a modified technique for hip labral reconstruction using iliotibial band allograft tissue and a front-to-back fixation technique. The described technique is modified from the original report of a technique for arthroscopic labral reconstruction. The front-to-back technique allows the surgeon to make a graft that is longer than necessary and cut excess graft after front-to-back fixation, resulting in the correct graft size and a reproducible procedure. Allograft tissue offers several advantages, including the ability to control graft thickness and length, as well as the ability to eliminate donor-site morbidity. This procedure adds to the available techniques for treatment of labral pathology by providing a labral reconstruction technique using allograft tissue. PMID:27073784
Semiclassical states on Lie algebras
Tsobanjan, Artur
2015-03-15
The effective technique for analyzing representation-independent features of quantum systems based on the semiclassical approximation (developed elsewhere) has been successfully used in the context of the canonical (Weyl) algebra of the basic quantum observables. Here, we perform the important step of extending this effective technique to the quantization of a more general class of finite-dimensional Lie algebras. The case of a Lie algebra with a single central element (the Casimir element) is treated in detail by considering semiclassical states on the corresponding universal enveloping algebra. Restriction to an irreducible representation is performed by “effectively” fixing the Casimir condition, following the methods previously used for constrained quantum systems. We explicitly determine the conditions under which this restriction can be consistently performed alongside the semiclassical truncation.
An Image-Based Technique for 3d Building Reconstruction Using Multi-View Uav Images
NASA Astrophysics Data System (ADS)
Alidoost, F.; Arefi, H.
2015-12-01
Nowadays, with the development of the urban areas, the automatic reconstruction of the buildings, as an important objects of the city complex structures, became a challenging topic in computer vision and photogrammetric researches. In this paper, the capability of multi-view Unmanned Aerial Vehicles (UAVs) images is examined to provide a 3D model of complex building façades using an efficient image-based modelling workflow. The main steps of this work include: pose estimation, point cloud generation, and 3D modelling. After improving the initial values of interior and exterior parameters at first step, an efficient image matching technique such as Semi Global Matching (SGM) is applied on UAV images and a dense point cloud is generated. Then, a mesh model of points is calculated using Delaunay 2.5D triangulation and refined to obtain an accurate model of building. Finally, a texture is assigned to mesh in order to create a realistic 3D model. The resulting model has provided enough details of building based on visual assessment.
de Chalain, Tristan; Black, Paul
2004-06-01
The reconstructive surgeon, dealing with both congenital anomalies such as clefts, and post-surgical or post-traumatic defects, may, on occasion be faced with a situation where there is either a unilateral deficit or excess of lip volume, or an asymmetry with bilateral volume inequalities. The classic examples of this are the characteristic whistle notch deformities sometimes seen after cleft-lip repairs. This paper presents another useful solution to such problems. The method involves the transposition of a transversely-oriented flap of mucosa, elevated on a connective tissue/muscle pedicle, and twisted or rotated 180 degrees from the contralateral side of the lip, to help fill the defect. The flap is asymmetrical, thus enabling transposition of more tissue into the primary defect than is lost from the donor site. The principal advantage is that in a lip in which there is already an overall paucity of tissue, nothing further is discarded, while at the same time, tissue is replaced where it is most needed. A secondary benefit is that with proper design, the lip can be shortened from side to side and therefore filled out in the antero-posterior dimension. Technical details of the method are explained and the versatility of the technique is illustrated. PMID:15145736
Mainwaring, Richard D; Ibrahimiye, Ali N; Hanley, Frank L
2016-08-01
Surgical reconstruction of peripheral pulmonary artery stenosis is a technically challenging procedure due to the need to access all lobar and segmental branches. This paper describes our surgical approach that entails division of the main pulmonary and separation of the branch pulmonary arteries. This surgical approach can also be utilized for other complex peripheral pulmonary artery reconstructions. PMID:27449462
NASA Astrophysics Data System (ADS)
Beasley, D. G.; Alves, L. C.; Barberet, Ph.; Bourret, S.; Devès, G.; Gordillo, N.; Michelet, C.; Le Trequesser, Q.; Marques, A. C.; Seznec, H.; da Silva, R. C.
2014-07-01
The tomographic reconstruction of biological specimens requires robust algorithms, able to deal with low density contrast and low element concentrations. At the IST/ITN microprobe facility new GPU-accelerated reconstruction software, JPIXET, has been developed, which can significantly increase the speed of quantitative reconstruction of Proton Induced X-ray Emission Tomography (PIXE-T) data. It has a user-friendly graphical user interface for pre-processing, data analysis and reconstruction of PIXE-T and Scanning Transmission Ion Microscopy Tomography (STIM-T). The reconstruction of PIXE-T data is performed using either an algorithm based on a GPU-accelerated version of the Maximum Likelihood Expectation Maximisation (MLEM) method or a GPU-accelerated version of the Discrete Image Space Reconstruction Algorithm (DISRA) (Sakellariou (2001) [2]). The original DISRA, its accelerated version, and the MLEM algorithm, were compared for the reconstruction of a biological sample of Caenorhabditis elegans - a small worm. This sample was analysed at the microbeam line of the AIFIRA facility of CENBG, Bordeaux. A qualitative PIXE-T reconstruction was obtained using the CENBG software package TomoRebuild (Habchi et al. (2013) [6]). The effects of pre-processing and experimental conditions on the elemental concentrations are discussed.
Padole, Atul; Sainani, Nisha; Lira, Diego; Khawaja, Ranish Deedar Ali; Pourjabbar, Sarvenaz; Lo Gullo, Roberto; Otrakji, Alexi; Kalra, Mannudeep K
2016-01-01
AIM: To assess diagnostic image quality of reduced dose (RD) abdominal computed tomography (CT) with 9 iterative reconstruction techniques (IRTs) from 4 different vendors to the standard of care (SD) CT. METHODS: In an Institutional Review Board approved study, 66 patients (mean age 60 ± 13 years, 44 men, and 22 women) undergoing routine abdomen CT on multi-detector CT (MDCT) scanners from vendors A, B, and C (≥ 64 row CT scanners) (22 patients each) gave written informed consent for acquisition of an additional RD CT series. Sinogram data of RD CT was reconstructed with two vendor-specific and a vendor-neutral IRTs (A-1, A-2, A-3; B-1, B-2, B-3; and C-1, C-2, C-3) and SD CT series with filtered back projection. Subjective image evaluation was performed by two radiologists for each SD and RD CT series blinded and independently. All RD CT series (198) were assessed first followed by SD CT series (66). Objective image noise was measured for SD and RD CT series. Data were analyzed by Wilcoxon signed rank, kappa, and analysis of variance tests. RESULTS: There were 13/50, 18/57 and 9/40 missed lesions (size 2-7 mm) on RD CT for vendor A, B, and C, respectively. Missed lesions includes liver cysts, kidney cysts and stone, gall stone, fatty liver, and pancreatitis. There were also 5, 4, and 4 pseudo lesions (size 2-3 mm) on RD CT for vendor A, B, and C, respectively. Lesions conspicuity was sufficient for clinical diagnostic performance for 6/24 (RD-A-1), 10/24 (RD-A-2), and 7/24 (RD-A-3) lesions for vendor A; 5/26 (RD-B-1), 6/26 (RD-B-2), and 7/26 (RD-B-3) lesions for vendor B; and 4/20 (RD-C-1) 6/20 (RD-C-2), and 10/20 (RD-C-3) lesions for vendor C (P = 0.9). Mean objective image noise in liver was significantly lower for RD A-1 compared to both RD A-2 and RD A-3 images (P < 0.001). Similarly, mean objective image noise lower for RD B-2 (compared to RD B-1, RD B-3) and RD C-3 (compared to RD C-1 and C-2) (P = 0.016). CONCLUSION: Regardless of IRTs and MDCT vendors
Sub-milliSievert ultralow-dose CT colonography with iterative model reconstruction technique
Ourednicek, Petr; Briza, Jan; Giepmans, Walter; Jahoda, Jiri; Hruska, Lukas; Danes, Jan
2016-01-01
Purpose. The purpose of this study was to evaluate the technical and diagnostic performance of sub-milliSievert ultralow-dose (ULD) CT colonograpy (CTC) in the detection of colonic and extracolonic lesions. Materials and Methods. CTC with standard dose (SD) and ULD acquisitions of 64 matched patients, half of them with colonic findings, were reconstructed with filtered back projection (FBP), hybrid (HIR) and iterative model reconstruction techniques (IMR). Image noise in six colonic segments, in the left psoas muscle and aorta were measured. Image quality of the left adrenal gland and of the colon in the endoscopic and 2D view was rated on a five point Likert scale by two observers, who also completed the reading of CTC for colonic and extracolonic findings. Results. The mean radiation dose estimate was 4.1 ± 1.4 mSv for SD and 0.86 ± 0.17 mSv for ULD for both positions (p < 0.0001). In ULD-IMR, SD-IMR and SD-HIR, the endoluminal noise was decreased in all colonic segments compared to SD-FBP (p < 0.001). There were 27 small (6–9 mm) and 17 large (≥10 mm) colonic lesions that were classified as sessile polyps (n = 38), flat lesions (n = 3), or as a mass (n = 3). Per patient sensitivity and specificity were 0.82 and 0.93 for ULD-FBP, 0.97 and 0.97 for ULD-HIR, 0.97 and 1.0 for ULD-IMR. Per polyp sensitivity was 0.84 for ULD-FBP, 0.98 for ULD-HIR, 0.98 for ULD-IMR. Significantly less extracolonic findings were detected in ULD-FBP and ULD-HIR, but in the E4 category by C-RADS (potentially important findings), the detection was similar. Conclusion. Both HIR and IMR are suitable for sub-milliSievert ULD CTC without sacrificing diagnostic performance of the study. PMID:27069813
NASA Astrophysics Data System (ADS)
Moreno-Chamarro, Eduardo; Ortega, Pablo; González-Rouco, Fidel; Montoya, Marisa
2016-04-01
We assess the use of the meridional thermal-wind transport estimated from zonal density gradients to reconstruct the oceanic circulation variability during the last millennium in a forced simulation with the ECHO-G coupled climate model. Following a perfect-model approach, model-based pseudo-reconstructions of the Atlantic meridional overturning circulation (AMOC) and the Florida Current volume transport (FCT) are evaluated against their true simulated variability. The pseudo-FCT is additionally verified as proxy for AMOC strength and compared with the available proxy-based reconstruction. The thermal-wind component reproduces most of the simulated AMOC variability, which is mostly driven by internal climate dynamics during the preindustrial period and by increasing greenhouse gases afterwards. The pseudo-reconstructed FCT reproduces well the simulated FCT and reasonably well the variability of the AMOC strength, including the response to external forcing. The pseudo-reconstructed FCT, however, underestimates/overestimates the simulated variability at deep/shallow levels. Density changes responsible for the pseudo-reconstructed FCT are mainly driven by zonal temperature differences; salinity differences oppose but play a minor role. These results thus support the use of the thermal-wind relationship to reconstruct the oceanic circulation past variability, in particular at multidecadal timescales. Yet model-data comparison highlights important differences between the simulated and the proxy-based FCT variability. ECHO-G simulates a prominent weakening in the North Atlantic circulation that contrasts with the reconstructed enhancement. Our model results thus do not support the reconstructed FC minimum during the Little Ice Age. This points to a failure in the reconstruction, misrepresented processes in the model, or an important role of internal ocean dynamics.
Desai, G S; Thabet, A; Elias, A Y A; Sahani, D V
2013-01-01
Objective To compare image quality and radiation dose of abdominal CT examinations reconstructed with three image reconstruction techniques. Methods In this Institutional Review Board-approved study, contrast-enhanced (CE) abdominopelvic CT scans from 23 patients were reconstructed using filtered back projection (FBP), adaptive statistical iterative reconstruction (ASiR) and iterative reconstruction in image space (IRIS) and were reviewed by two blinded readers. Subjective (acceptability, sharpness, noise and artefacts) and objective (noise) measures of image quality were recorded for each image data set. Radiation doses in CT dose index (CTDI) dose–length product were also calculated for each examination type and compared. Imaging parameters were compared using the Wilcoxon signed rank test and a paired t-test. Results All 69 CECT examinations were of diagnostic quality and similar for overall acceptability (mean grade for ASiR, 3.9±0.3; p=0.2 for Readers 1 and 2; IRIS, 3.9±0.4, p=0.2; FBP, 3.8±0.9). Objective noise was considerably lower with both iterative techniques (p<0.0001 and 0.0016 for ASiR and IRIS). Recorded mean radiation dose, i.e. CTDIvol, was 24% and 10% less with ASiR (11.4±3.4 mGy; p<0.001) and IRIS (13.5±3.7 mGy; p=0.06), respectively, than with FBP: 15.0±3.5 mGy. Conclusion At the system parameters used in this study, abdominal CT scans reconstructed with ASiR and IRIS provide diagnostic images with reduced image noise and 10–24% lower radiation dose than FBP. Advances in knowledge CT images reconstructed with FBP are frequently noisy on lowering the radiation dose. Newer iterative reconstruction techniques have different approaches to produce images with less noise; ASiR and IRIS provide diagnostic abdominal CT images with reduced image noise and radiation dose compared with FBP. This has been documented in this study. PMID:23255538
Gravvanis, Andreas; Kakagia, Despoina; Samouris, George; Galani, Eleni; Tsoutsos, Dimosthenis
2016-06-01
Purpose The dual-plane deep inferior epigastric perforator (DIEP) flap inset technique is herein presented with tips for optimizing the aesthetic outcome in delayed autologous breast reconstruction after radiation therapy. Patients and Methods A total of 42 women who underwent microsurgical reconstruction with a free DIEP flap participated in this prospective study. The flap was inset in a dual plane lying behind the pectoralis major at the upper pole and in front of the muscle at the lower pole of the reconstructed breast. Results The dual-plane flap inset resulted in natural transition from native and reconstructed tissues, excellent scar quality, optimal outline of the breast, and overall breast appearance. Moreover, dual-plane reconstruction was associated with constantly high patient satisfaction without wearing brassiere due to fullness of the upper pole and minimal ptosis with time. Conclusion The dual-plane DIEP flap inset results in optimal scar quality, breast shape, and fullness of the upper pole, resulting in high patient satisfaction. PMID:27077210
Mascarenhas, Randy; Raleigh, Eden; McRae, Sheila; Leiter, Jeff; Saltzman, Bryan; MacDonald, Peter B.
2014-01-01
Performing a labral repair alone in patients with recurrent anterior instability and a large glenoid defect has led to poor outcomes. We present a technique involving the use of the iliac crest allograft inserted into the glenoid defect in athletes with recurrent anterior shoulder instability and large bony defects of the glenoid (>25% of glenoid diameter). All athletes with recurrent anterior shoulder instability and a large glenoid defect that underwent open anterior shoulder stabilization and glenoid reconstruction with the iliac crest allograft were followed over a 4-year period. Preoperatively, a detailed history and physical exam were obtained along with standard radiographs and magnetic resonance imaging of the affected shoulder. All patients also completed the Simple Shoulder Test (SST) and American Shoulder and Elbow Surgeons (ASES) evaluation forms preoperatively. A computed tomography scan was obtained postoperatively to assess osseous union of the graft and the patient again went through a physical exam in addition to completing the SST, ASES, and Western Ontario Shoulder Instability Index (WOSI) forms. 10 patients (9 males, 1 female) were followed for an average of 16 months (4–36 months) and had a mean age of 24.4 years. All patients exhibited a negative apprehension/relocation test and full shoulder strength at final follow-up. Eight of 10 patients had achieved osseous union at 6 months (80.0%). ASES scores improved from 64.3 to 97.8, and SST scores improved from 66.7 to 100. Average postoperative WOSI scores were 93.8%. The use of the iliac crest allograft provides a safe and clinically useful alternative compared to previously described procedures for recurrent shoulder instability in the face of glenoid deficiency. PMID:25538432
Three-dimensional reconstruction techniques to study ditches eco-hydrology
NASA Astrophysics Data System (ADS)
Vinatier, Fabrice; Bailly, Jean-Stéphane; Combemale, David
2015-04-01
Agricultural ditches are common linear features of cultivated landscapes assuming several primary functions: soil water drainage, retention of pollutants, soil erosion prevention. In Mediterranean hilly areas, ditches shape a network over a catchment in order to convey surface runoff out of the plots during short but intense storms. Furthermore, these man made ditches provide valuable habitat for fauna and flora. Our study aims at exploring how the hydraulic functioning of ditches is affected by biotic activities occurring at ditch scale, such as plant development (canopy height, vegetation covering and blockage factor which is the fraction of the channel cross-section blocked by vegetation, which all determines the flow resistance due to vegetation) and soil disturbance by burrowing herbivores. To this end, we applied a stereophotogrammetric study to monitor vegetation and ditch geometry on a 100 meters long ditch segment. The study was conducted from April to December 2014 on an agricultural ditch in South of France. Plant species were collected for referencing and manifestation of soil disturbance by Mediterranean Pine Vole were noticed. The data collected gathered a chronosequence of twenty point clouds at 1 mm resolution. Clouds coherence and precision were confronted to Terrestrial Lidar Scans acquired in April and September 2014 for validation. Clouds were classified to disentangle the ground from the canopy vegetation . The Pine Vole excavations and the plant species were classified inside the ground and vegetation clouds, respectively. Different vegetation metrics related to ditch hydraulics were estimated and map from the chronosequence : the canopy height dynamics, the vegetation cover dynamics and the blockage factors dynamic.. Vegetation metrics appears to be highly variable temporally and spatially, mainly due to plant development and species traits. Thanks to these three-dimensional reconstruction techniques, data clouds at high resolution linked to
Rustemeyer, Jan; Melenberg, Alex; Sari-Rieger, Aynur
2014-12-01
This study aims to evaluate the additional costs incurred by using a computer-aided design/computer-aided manufacturing (CAD/CAM) technique for reconstructing maxillofacial defects by analyzing typical cases. The medical charts of 11 consecutive patients who were subjected to the CAD/CAM technique were considered, and invoices from the companies providing the CAD/CAM devices were reviewed for every case. The number of devices used was significantly correlated with cost (r = 0.880; p < 0.001). Significant differences in mean costs were found between cases in which prebent reconstruction plates were used (€3346.00 ± €29.00) and cases in which they were not (€2534.22 ± €264.48; p < 0.001). Significant differences were also obtained between the costs of two, three and four devices, even when ignoring the cost of reconstruction plates. Additional fees provided by statutory health insurance covered a mean of 171.5% ± 25.6% of the cost of the CAD/CAM devices. Since the additional fees provide financial compensation, we believe that the CAD/CAM technique is suited for wide application and not restricted to complex cases. Where additional fees/funds are not available, the CAD/CAM technique might be unprofitable, so the decision whether or not to use it remains a case-to-case decision with respect to cost versus benefit. PMID:25459375
Twisted Quantum Toroidal Algebras
NASA Astrophysics Data System (ADS)
Jing, Naihuan; Liu, Rongjia
2014-09-01
We construct a principally graded quantum loop algebra for the Kac-Moody algebra. As a special case a twisted analog of the quantum toroidal algebra is obtained together with the quantum Serre relations.
NASA Astrophysics Data System (ADS)
Majeed, Abdul; Piah, Abd Rahni Mt
2015-10-01
Spline has been used extensively in engineering design and modelling for representation, analysis and manufacturing purposes. This paper presents an application of spline methods in bio-medical modelling. We reconstruct craniofacial fractured skull bone images using rational cubic Ball interpolant with two free parameters. The free parameters are optimized with the help of genetic algorithm. Our emphasis is placed on the accuracy and smoothness of the reconstructed images.
Localization of Free Field Realizations of Affine Lie Algebras
NASA Astrophysics Data System (ADS)
Futorny, Vyacheslav; Grantcharov, Dimitar; Martins, Renato A.
2015-04-01
We use localization technique to construct new families of irreducible modules of affine Kac-Moody algebras. In particular, localization is applied to the first free field realization of the affine Lie algebra or, equivalently, to imaginary Verma modules.
Lorbach, Olaf; Herbort, Mirco; Engelhardt, Martin; Kieb, Matthias
2013-01-01
Objectives: Biomechanical evaluation of knee laxity after single- and double-bundle ACL reconstruction with additional medial meniscus suture. Methods: Kinematics of the intact knee were determined in 12 human cadaver specimens in response to a 134-N anterior tibial load (aTT) and a combined rotatory load of 10 Nm valgus and 4 Nm internal tibial rotation using a robotic/universal force moment sensor testing system. Subsequently, the ACL was resected following the creation of a bucket-handle tear of the medial meniscus. A standard repair of the medial meniscus was performed using 3 inside-out horizontal sutures. Finally, The ACL was reconstructed using an anatomic single-bundle (6) or double-bundle technique (6). Knee kinematics were determined following every sub-step. Results: Significant increase of aTT in the ACL-deficient knee was found with significant increase in the ACL-deficient knee with additional medial meniscal injury (p=.003; p=.009). ACL reconstructions significantly decreased aTT compared to the ACL-deficient knee. No significant differences were found between the intact knee and the ACL reconstructed knee with additional meniscal repair. In response to a simulated pivot shift, aTT in the intact knee significantly increased in the ACL-deficient knee as well as in the meniscus injured/meniscus-sutured knee (p=.003;p=.007). No significant differences were found between the ACL-deficient and ACL reconstructed knee with additional meniscal repair. SB as well as DB ACL reconstruction with additional medial meniscal repair restored knee kinematics compared to the intact knee. Comparison of SB versus DB ACL reconstruction did not reveal any significant differences neither in a simulated Lachman test nor in response to a simulated pivot shift (p=.05). Conclusion: aTT as well as aTT in response to a combined rotatory load significantly increased with ACL deficiency compared to the intact knee, additional medial meniscal injury further increased aTT. Anatomic
Frank, Rachel M.; Trenhaile, Scott W.
2015-01-01
Surgical management of acromioclavicular (AC) joint separations remains challenging, especially in the revision setting. Most commonly, Rockwood type I and II injuries are managed nonoperatively whereas type IV, V, and VI injuries are managed with surgery. Type III separations are more controversial, with evidence supporting both nonoperative and operative treatment options. Multiple different arthroscopic techniques have been described; however, there is no current gold standard. AC joint reconstruction with the TightRope device (Arthrex, Naples, FL) with the patient in the lateral decubitus position is a method of restoring joint stability that allows for a minimally invasive, low-profile fixation construct using a single drill hole through the clavicle. Allograft augmentation of this fixation construct helps to eliminate the stress risers potentially created by this device while increasing overall repair construct stability. The purpose of this article is to describe the surgical technique for arthroscopic AC joint reconstruction using a TightRope device with allograft augmentation. PMID:26759765
A CT reconstruction algorithm based on non-aliasing Contourlet transform and compressive sensing.
Deng, Lu-zhen; Feng, Peng; Chen, Mian-yi; He, Peng; Vo, Quang-sang; Wei, Biao
2014-01-01
Compressive sensing (CS) theory has great potential for reconstructing CT images from sparse-views projection data. Currently, total variation (TV-) based CT reconstruction method is a hot research point in medical CT field, which uses the gradient operator as the sparse representation approach during the iteration process. However, the images reconstructed by this method often suffer the smoothing problem; to improve the quality of reconstructed images, this paper proposed a hybrid reconstruction method combining TV and non-aliasing Contourlet transform (NACT) and using the Split-Bregman method to solve the optimization problem. Finally, the simulation results show that the proposed algorithm can reconstruct high-quality CT images from few-views projection using less iteration numbers, which is more effective in suppressing noise and artefacts than algebraic reconstruction technique (ART) and TV-based reconstruction method. PMID:25101142
Xiong, Jiang; Guo, Wei; Liu, Xiaoping; Jia, Xin; Ma, Xiaohui; Wang, Lijun
2015-07-01
Thoracic endovascular aortic repair (TEVAR) of arch pathology presents special challenges for revascularization. To obtain an anatomic reconstruction of the arch arteries, in situ fenestration with extra-anatomic bypass has been increasingly used in TEVAR. We report a case involving TEVAR for a pseudoaneurysm at zone 2 of the thoracic aorta in a 37-year-old man with the use of in situ fenestration assisted by a temporary endovascular shunt technique. PMID:24560242
Beam hardening correction for sparse-view CT reconstruction
NASA Astrophysics Data System (ADS)
Liu, Wenlei; Rong, Junyan; Gao, Peng; Liao, Qimei; Lu, HongBing
2015-03-01
Beam hardening, which is caused by spectrum polychromatism of the X-ray beam, may result in various artifacts in the reconstructed image and degrade image quality. The artifacts would be further aggravated for the sparse-view reconstruction due to insufficient sampling data. Considering the advantages of the total-variation (TV) minimization in CT reconstruction with sparse-view data, in this paper, we propose a beam hardening correction method for sparse-view CT reconstruction based on Brabant's modeling. In this correction model for beam hardening, the attenuation coefficient of each voxel at the effective energy is modeled and estimated linearly, and can be applied in an iterative framework, such as simultaneous algebraic reconstruction technique (SART). By integrating the correction model into the forward projector of the algebraic reconstruction technique (ART), the TV minimization can recover images when only a limited number of projections are available. The proposed method does not need prior information about the beam spectrum. Preliminary validation using Monte Carlo simulations indicates that the proposed method can provide better reconstructed images from sparse-view projection data, with effective suppression of artifacts caused by beam hardening. With appropriate modeling of other degrading effects such as photon scattering, the proposed framework may provide a new way for low-dose CT imaging.
Algebraic vs physical N = 6 3-algebras
Cantarini, Nicoletta; Kac, Victor G.
2014-01-15
In our previous paper, we classified linearly compact algebraic simple N = 6 3-algebras. In the present paper, we classify their “physical” counterparts, which actually appear in the N = 6 supersymmetric 3-dimensional Chern-Simons theories.
SU-D-12A-05: Iterative Reconstruction Techniques to Enable Intrinsic Respiratory Gated CT in Mice
Sun, T; Sun, N; Tan, S; Liu, Y; Mistry, N
2014-06-01
Purpose: Longitudinal studies of lung function in mice need the ability to image different phases of ventilation in free-breathing mice using retrospective gating. However, retrospective gating often produces under-sampled and uneven angular samples, resulting in severe reconstruction artifacts when using traditional FDK based reconstruction algorithms. We wanted to demonstrate the utility of iterative reconstruction method to enable intrinsic respiratory gating in small-animal CT. Methods: Free-breathing mice were imaged using a Siemens Inveon PET/micro-CT system. Evenly distributed projection images were acquired at 360 angles. Retrospective respiratory gating was performed using an intrinsic marker based on the average intensity in a region covering the diaphragm. Projections were classified into 4 and 6 phases (finer temporal resolution) resulting in 138 and 67 projections respectively. Reconstruction was carried out using 3 Methods: conventional FDK, iterative penalized least-square (PWLS) with total variation (TV), and PWLS with edge-preserving penalty. The performance of the methods was compared using contrast-to-noise (CNR) in a region of interest (ROI). Line profile through a specific region was plotted to evaluate the preserving of edges. Results: In both the cases with 4 and 6 phases, inadequate and non-uniform angular sampling results in artifacts using conventional FDK. However, such artifacts are minimized using both the iterative methods. Using both 4 and 6 phases, the iterative techniques outperformed FDK in terms of CNR and maintaining sharp edges. This is further evidenced especially with increased artifacts using FDK for 6 phases. Conclusion: This work indicates fewer artifacts and better image details can be achieved with iterative reconstruction methods in non-uniform under-sampled reconstruction. Using iterative methods can enable free-breathing intrinsic respiratory gating in small-animal CT. Further studies are needed to compare the
Chang Liyun; Ho, Sheng-Yow; Chui, Chen-Shou; Du, Yi-Chun; Chen Tainsong
2009-09-15
A method was presented that employs standard linac QA tools to verify the accuracy of film reconstruction algorithms used in the brachytherapy planning system. Verification of reconstruction techniques is important as suggested in the ESTRO booklet 8: ''The institution should verify the full process of any reconstruction technique employed clinically.'' Error modeling was also performed to analyze seed-position errors. The ''isocentric beam checker'' device was used in this work. It has a two-dimensional array of steel balls embedded on its surface. The checker was placed on the simulator couch with its center ball coincident with the simulator isocenter, and one axis of its cross marks parallel to the axis of gantry rotation. The gantry of the simulator was rotated to make the checker behave like a three-dimensional array of balls. Three algorithms used in the ABACUS treatment planning system: orthogonal film, 2-films-with-variable-angle, and 3-films-with-variable-angle were tested. After exposing and digitizing the films, the position of each steel ball on the checker was reconstructed and compared to its true position, which can be accurately calculated. The results showed that the error is dependent on the object-isocenter distance, but not the magnification of the object. The averaged errors were less than 1 mm within the tolerance level defined by Roueet al. [''The EQUAL-ESTRO audit on geometric reconstruction techniques in brachytherapy,'' Radiother. Oncol. 78, 78-83 (2006)]. However, according to the error modeling, the theoretical error would be greater than 2 mm if the objects were located more than 20 cm away from the isocenter with a 0.5 deg. reading error of the gantry and collimator angles. Thus, in addition to carefully performing the QA of the gantry and collimator angle indicators, it is suggested that the patient, together with the applicators or seeds inside, should be placed close to the isocenter as much as possible. This method could be used
Fatigue loading history reconstruction based on the rain-flow technique
NASA Technical Reports Server (NTRS)
Khosrovaneh, A. K.; Dowling, N. E.
1989-01-01
Methods are considered for reducing a non-random fatigue loading history to a concise description and then for reconstructing a time history similar to the original. In particular, three methods of reconstruction based on a rain-flow cycle counting matrix are presented. A rain-flow matrix consists of the numbers of cycles at various peak and valley combinations. Two methods are based on a two dimensional rain-flow matrix, and the third on a three dimensional rain-flow matrix. Histories reconstructed by any of these methods produce a rain-flow matrix identical to that of the original history, and as a result the resulting time history is expected to produce a fatigue life similar to that for the original. The procedures described allow lengthy loading histories to be stored in compact form.