Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 40 for “"iterative reconstruction"”.
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Iterative Reconstruction Algorithms for Polyenergetic X-ray Computerized Tomography
A reconstruction algorithm in computerized tomography is a procedure for reconstructing the attenuation coefficientscient, a real-valued function associated with the object of interest, from the measured projection data. Generally speaking, reconstruction algorithms in CT fall into two categories: …
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Implementation of Iterative Reconstruction of Images from Multiple Bases Representations
… MBR distorted images are reconstructed by the iterative method of Projection onto Convex Sets (POCS). Many constraints that form convex sets are reviewed and examined. Due to the high distortion at the block boundaries, some constraints are introduced particularly to reduce artifacts at the …
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Modeling and Development of Iterative Reconstruction Algorithms in Emerging X-ray Imaging Technologies
… radiation doses associated with use of analytic reconstruction methods in DPCT, we analyze the numerical and statistical properties of two classes of discrete imaging models that form the basis for iterative image reconstruction. Secondly, to improve image quality in grating-based phase-contrast …
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Advanced Statistical Modeling for Model-Based Iterative Reconstruction for Single-Energy and Dual-Energy X-Ray CT
Model-based iterative reconstruction (MBIR) has been increasingly broadly applied as an improvement over traditional, analytical image reconstruction methods in X-ray CT, primarily due to its significant advantage in drastic dose reduction without diagnostic loss. Early success of the method in …
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Iterative reconstruction as a novel method of radiation dose reduction at computed tomography in patients with Crohn's disease
… limitation with conventional CT raw data reconstruction was the inherent coupling of administered radiation dose with observed image noise – the lower the radiation dose, the noisier the image. The renaissance, rediscovery and refinement of iterative reconstruction removes this limitation …
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The Software and Hardware Acceleration for Interior Tomography
… and high-speed imaging characteristic. The iterative reconstruction algorithms are becoming more important since they can reconstruct better image qualities from incomplete projection data compared to analytical reconstruction algorithms. Iterative reconstruction algorithms also allow more …
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Development and Validation of Reconstruction Algorithms for 3D Tomography Diagnostics
This work reports three reconstruction algorithms developed to address the practical issues encountered in 3D tomography diagnostics, such as the limited view angles available in many practical applications, the large scale and nonlinearity of the problems when they are in 3D, and the measurement …
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Fast Backprojection Algorithms for Divergent Beam Tomography
… moving to higher resolution images or utilizing iterative reconstruction algorithms, which use multiple backprojection operations.
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Reconstruction of Functions From Non-uniformly Distributed Sampled Data in Shift-Invariant Frame Subspaces
… research is to study and implement efficient iterative reconstruction algorithms. Iterative reconstruction algorithms are used to reconstruct bandlimited signals in shift-invariant L2 subspaces from a set of non-uniformly distributed sampled data. The Shannon-Whittaker reconstruction formula …
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COMPARATIVE STUDIES OF DIFFERENT SYSTEM MODELS FOR ITERATIVE CT IMAGE RECONSTRUCTION
… DDM and IDDM, are compared in the content of iterative CT image reconstruction algorithms. One of the key factors that limit the clinical application of an iterative reconstruction algorithm is the high computational cost which mainly depends on the system model. This thesis can serve as the …
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Algebraic Reconstruction Methods for Complex Geometry Components
… cabinet systems are capable of acquisition and reconstruction of Cone Beam CT (CBCT) data utilising reconstruction algorithms such as the FDK, which are mathematically based on traditional FBP. While these algorithms are computationally efficient, limitations in the acquisition make inspection …
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Optimization of image quality and radiation dose in neuroradiological computed tomography
… with new post-processing image filters and iterative reconstruction (IR) algorithms that improve image quality and allow for reduced radiation doses. Implementation of new methods in clinical routine requires prior validation in phantoms and clinical feasibility studies including …
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IMPROVING RESOLUTION IN WRIST SPECT WITH CONVERGING COLLIMATORS AND CT ANATOMICAL PRIORS
… counts, which is a 10% improvement to current iterative reconstruction techniques. These results demonstrated that pinhole collimation or CT prior information, which is now possible with SPECT/CT canneras can improve spatial resolution, however, current count levels are a limiting factor.
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Development and implementation of efficient noise suppression methods for emission computed tomography
<p>In PET and SPECT imaging, iterative reconstruction is now widely used due to its capability of incorporating into the reconstruction process a physics model and Bayesian statistics involved in photon detection. Iterative reconstruction methods rely on regularization terms to suppress image noise …
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Tomographic reconstruction with adaptive sparsifying transforms
… have long been known to improve the quality of reconstructions from low-dose data. Recent work has shown the promise of adaptive, rather than fixed, sparse representations. In particular, the synthesis dictionary learning framework has been shown to outperform traditional regularization …
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Image Reconstruction for X-ray Computed Tomography in Security Screening Applications
… present a new set of challenges for the reconstruction problem. For example, the size and composition of the scan subjects, the throughput requirements, and the measure of image quality are</p> <p>all factors that lead to a different set of design considerations. This thesis investigates …
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A Phantom Study for Attenuation Change and Detection of Calcification in Lung Nodules According to Variation of Examination Techniques in Low Dose CT
… a standard and various low-dose settings with iterative reconstruction. Mean attenuation of nodules and image noise were compared between the standard-dose and low-dose images. Diagnostic accuracy of visual assessment by two readers for discrimination of hyperdense nodule was analyzed using CT …
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Signal compression and reconstruction using multiple bases representation
… data compression at the transmitter end, and the reconstruction using the received information and all the available a priori or side information at the receiver end. In this thesis, we propose an adaptive signal representation scheme, based on the use of multiple orthogonal basis sets, that …
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Estimation and calibration algorithms for distributed sampling systems
… uniform timing. Methods for bandlimited input reconstruction from nonuniform recurrent samples are presented for both the small-mismatch and the low-SNR domains. Alternate iterative reconstruction methods are developed to give insight into the geometry of the problem.From these reconstruction …
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Development and Implementation of Fully 3D Statistical Image Reconstruction Algorithms for Helical CT and Half-Ring PET Insert System
… high computational cost, statistical iterative reconstruction algorithms are known to reconstruct high-quality images from noisy tomographic datasets. The overall goal of this work is to design statistical reconstruction software for clinical x-ray CT scanners, and for a novel PET …
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