The notion of a linogram is introduced. It corresponds to the notion of a sinogram in the conventional representation of projection data in imagereconstruction. In the sinogram the points corresponding to rays that g...
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ISBN:
(纸本)0818608447
The notion of a linogram is introduced. It corresponds to the notion of a sinogram in the conventional representation of projection data in imagereconstruction. In the sinogram the points corresponding to rays that go through a fixed point in the cross section to be reconstructed all fall on a sinusoidal curve. In the linogram, however, these points fall on a straight line, so backprojection corresponds to integration along straight lines in the linogram. A theorem is described which expresses the backprojection operator in terms of the Radon transform and simple changes of variables. A novel image-reconstruction method based on the theorem is introduced.
Examines the implications of reconstruction based on measurements of echoed waves from an object. The Helmholtz wave equation model is used for the inversion (diffraction imaging). It is shown that the resultant inver...
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Examines the implications of reconstruction based on measurements of echoed waves from an object. The Helmholtz wave equation model is used for the inversion (diffraction imaging). It is shown that the resultant inverted data provides coverage in a one-quadrant of the spatial frequency domain. This coverage yields accurate information regarding the surface structure of the object under study.< >
The notion of linogram is introduced. It corresponds to the notion of a sinogram in the conventional representation of projection data in imagereconstruction. In the sinogram the points corresponding to rays that go ...
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The notion of linogram is introduced. It corresponds to the notion of a sinogram in the conventional representation of projection data in imagereconstruction. In the sinogram the points corresponding to rays that go through a fixed point in the cross section to be reconstructed all fall on a sinusoidal curve. In the linogram, however, these points fall on a straight line, so back projection corresponds to integration along straight lines in the linogram. A theorem is described which expresses the back projection operator in terms of the Radon transform and simple changes of variables. A novel imagereconstruction method based on the theorem is introduced.< >
The author treats the problem of calculating the 3-D structure of a biological specimen from its images obtained in a transmission electron microscope. In general, this process is accomplished by tilting the specimen ...
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The author treats the problem of calculating the 3-D structure of a biological specimen from its images obtained in a transmission electron microscope. In general, this process is accomplished by tilting the specimen inside the microscope, collecting the tilted images, and using these data as input to a 3-D reconstruction algorithm. However there is an unavoidable limit for the maximum tilt angle that can be achieved. Methods to recover the missing information are thus fundamentally needed. The author presents an approach based on projections onto convex sets (POCS) as it has been applied to a subviral particle, and comments on the obtained results.< >
The problem on tomographic imagereconstructionfrom limited-view-angle projection data is dealt with. Based on the Helgason-Ludwig consistency condition, a procedure for completion of incomplete projection data is in...
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The problem on tomographic imagereconstructionfrom limited-view-angle projection data is dealt with. Based on the Helgason-Ludwig consistency condition, a procedure for completion of incomplete projection data is introduced to improve the reconstructed image quality. Using a regularization method, an algorithm robust to the presence of noise is presented. The performance of the algorithm was confirmed in the numerical simulation. The reconstructed images were quantitatively improved by this procedure with a realistic amount of computation.
In some imaging techniques, such as X-ray computerized tomography (CT) and magnetic resonance imaging (MRI), analytical formulas exist for reconstructing an imagefrom a continuum of data which can only be approximate...
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In some imaging techniques, such as X-ray computerized tomography (CT) and magnetic resonance imaging (MRI), analytical formulas exist for reconstructing an imagefrom a continuum of data which can only be approximated by measured data. A method of analytical imagereconstruction using a special set of functions made up of combinations of cubic spline functions and trigonometric functions is described. The significance and advantages of this approach are presented. It is shown how the approach can easily accommodate imagereconstruction problems with irregularly sampled data and incompletedata. Examples of applications of this approach to X-ray CT and MRI are given.
Ill-conditioned problems arise frequently in computer vision because the image information contains noise and ambiguities such that the true identity of the scene is not uniquely specified. It is nonetheless possible ...
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ISBN:
(纸本)081860777X
Ill-conditioned problems arise frequently in computer vision because the image information contains noise and ambiguities such that the true identity of the scene is not uniquely specified. It is nonetheless possible for humans to infer the structure of objects fromincompletedata, presumably through the use of assumptions and computations consistent with natural images. A method in numerical analysis is considered for solving 'inverse problems' when the degraded scene has undergone a sequence of steps modeled by a known equation. reconstruction can then be attempted by finding a solution that minimizes the deviation from that equation. The method is exemplified by its application to the deblurring problem. In this problem, deblurring is achieved by computing a succession of images, each slightly deblurred from the previous, such that the complete set satisfies the equations specifying the diffusion process of blurring. The method can be viewed as an approach to regularization for problems where a scale-space parameter can be used to separate the information extracted from the image.
In this paper, we deal with the problem on tomographic imagereconstructionfrom limited view angle projection data. Based on the Helgason-Ludwig consistency condition, a new procedure for completion of incomplete pro...
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In this paper, we deal with the problem on tomographic imagereconstructionfrom limited view angle projection data. Based on the Helgason-Ludwig consistency condition, a new procedure for completion of incomplete projection data is introduced to improve the reconstructed image quality. Using regularization method the robust algorithm to the presence of noise is presented. The performance of new algorithm was confirmed in the numerical simulation. The reconstructed images were quantitatively improved by this procedure with realistic amount of computation.
The author addresses the problems of imagereconstruction in fan beam straight-path tomography from complete and incompletedata. A method for restoring the parallel beam projections of an object from its fan beam pro...
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The author addresses the problems of imagereconstruction in fan beam straight-path tomography from complete and incompletedata. A method for restoring the parallel beam projections of an object from its fan beam projections is introduced. The scheme uses FFT routines. This approach reduces the required amount of the collected fan beam by half. Also, a noniterative method of imagereconstruction, when arbitrary segments of the object projections cannot be detected, is presented. The technique exploits the functional properties of the object projections, in conjunction with a priori information available about the test object, to restore the unknown data.
A study of the direct Fourier method for the three-dimensional reconstruction of objects from their two-dimensional projection images has been carried out using computer-generated images. The existence of missing info...
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ISBN:
(纸本)0444878475
A study of the direct Fourier method for the three-dimensional reconstruction of objects from their two-dimensional projection images has been carried out using computer-generated images. The existence of missing information in the real input data is discussed, and point spread functions corresponding to some experimental data acquisition procedures are calculated. Several three-dimensional reconstructions of the model object are obtained and compared to real datareconstructions. Useful criteria for assessing the quality and the correct interpretation of the experimentally reconstructed images are deduced.
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