Surface reconstructionfrom measurements of spatial gradient is an important computer vision problem with applications in photometric stereo and shape-from-shading. In the case of morphologically complex surfaces obse...
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Surface reconstructionfrom measurements of spatial gradient is an important computer vision problem with applications in photometric stereo and shape-from-shading. In the case of morphologically complex surfaces observed in the presence of shadowing and transparency artifacts, a relatively large number of gradient measurements may be required for accurate surface reconstruction. Consequently, due to hardware limitations of image acquisition devices, situations are possible in which the available sampling density might not be sufficiently high to allow for recovery of essential surface details. In this paper, the above problem is resolved by means of derivative compressed sensing (DCS). DCS can be viewed as a modification of the classical compressed sensing (CS), which is particularly suited for reconstructions involving image/surface gradients. We demonstrate that using DCS results in substantial data savings as compared to the standard (dense) sampling, while producing estimates of higher accuracy and smaller variability, as compared to CS-base estimates. The results of this study are further supported by a series of numerical experiments.
This paper presents the preliminary results of PET system simulation using Monte Carlo code. We also present the implementation of attenuation correction for MCNP-generated PET image. Using MCNP5 we constructed a data...
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ISBN:
(纸本)9781467316644
This paper presents the preliminary results of PET system simulation using Monte Carlo code. We also present the implementation of attenuation correction for MCNP-generated PET image. Using MCNP5 we constructed a data base for a uniform cylindrical source. The data obtained from the simulation were then used for PET imagereconstruction. During the imagereconstruction, calculated attenuation correction method was implemented to the PET raw data. This method was chosen due to the fact that our study involved homogeneous and simple geometry phantom.
image formation involves understanding sensor characteristics and object reflectance. In dentistry, an accurate 3-D representation of the human jaw may be used for diagnostic and treatment purposes. Photogrammetry can...
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image formation involves understanding sensor characteristics and object reflectance. In dentistry, an accurate 3-D representation of the human jaw may be used for diagnostic and treatment purposes. Photogrammetry can offer a flexible, cost effective solution for accurate 3-D representation of the human teeth, which can be used for diagnostic and treatment purposes. Nonetheless there are several challenges, such as the non-friendly image acquisition environment inside the human mouth, problems with lighting and errors due to the data acquisition sensors. In this paper, we focus on the 3D surface reconstruction aspect for human teeth based on a single image. We introduce a more realistic formulation of the shape-from-shading (SFS) problem by considering the image formation components;the camera, the light source, and the surface reflectance. We propose a non-Lambertian SFS algorithm under perspective projection which benefits from camera calibration parameters. We take into account the attenuation of illumination due to near-field imaging. The surface reflectance is modeled using Oren-Nayar-Wolff model which accounts for the retro-reflection case. Our experiments provide promising quantitative metric results for the proposed approach.
In statistical theory, the Huber function yields robust estimations reducing the effect of outliers. In this paper, we employ the Huber function as regularization in a challenging inverse problem: quantitative microwa...
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In statistical theory, the Huber function yields robust estimations reducing the effect of outliers. In this paper, we employ the Huber function as regularization in a challenging inverse problem: quantitative microwave imaging. Quantitative microwave tomography aims at estimating the permittivity profile of a scattering object based on measured scattered fields, which is a nonlinear, ill-posed inverse problem. The results on 3D data sets are encouraging: the reconstruction error is reduced and the permittivity profile can be estimated from fewer measurements compared to state-of-the art inversion procedures.
Most existing approaches to the non-rigid structure from motion problem use batch type algorithms with all the data collected before 3D shape reconstruction takes place. Such a methodology is not suitable for real-tim...
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Most existing approaches to the non-rigid structure from motion problem use batch type algorithms with all the data collected before 3D shape reconstruction takes place. Such a methodology is not suitable for real-time applications. Concurrent on-line estimation of the camera position and 3D structure, based only on the measurements up to that moment is much more a challenging problem. In this paper, a novel approach is proposed for recursive recovery of non-rigid structures fromimage sequences captured by an orthographic camera. The main novelty in the proposed method is an adaptive algorithm for construction of shape constraints imposing stability on the on-line reconstructed shapes. The proposed, adaptively learned constraints have two aspects, consisting of constraints imposed on the basic shapes, the basic "building blocks" from which shapes are reconstructed, as well as constraints imposed on the mixing coefficients in a form of their probability distribution. The constraints are updated when the current model inadequately represents new shapes. This is achieved by means of Incremental Principal Component Analysis (IPCA). Results of the proposed method are shown on synthetic and real data of articulated face.
Many real world data mining applications involve analyzing geo-referenced data. Frequently, this type of data sets are incomplete in the sense that not all geographical coordinates have measured values of the variable...
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ISBN:
(纸本)9781467346498
Many real world data mining applications involve analyzing geo-referenced data. Frequently, this type of data sets are incomplete in the sense that not all geographical coordinates have measured values of the variable(s) of interest. This incompleteness may be caused by poor data collection, measurement errors, costs management and many other factors. These missing values may cause several difficulties in many applications. Spatial imputation/interpolation methods try to fill in these unknown values in geo-referenced data sets. In this paper we propose a new spatial imputation method based on machine learning algorithms and a series of data preprocessing steps. The key distinguishing factor of this method is allowing the use of datafrom faraway regions, contrary to the state of the art on spatial data mining. images (e.g. from a satellite or video surveillance cameras) may also suffer from this incompleteness where some pixels are missing, which again may be caused by many factors. An image can be seen as a spatial data set in a Cartesian coordinates system, where each pixel (location) registers some value (e.g. degree of gray on a black and white image). Being able to recover the original imagefrom a partial or incompleteversion of the reality is a key application in many domains (e.g. surveillance, security, etc.). In this paper we evaluate our general methodology for spatial interpolation on this type of problems. Namely, we check the ability of our method to fill in unknown pixels on several images. We compare it to state of the art methods and provide strong experimental evidence of the advantages of our proposal.
Joint demosaicking and denoising consists in reconstructing a color imagefrom the noisy raw data output by the sensor of a digital camera. We adopt a variational formulation in which the reconstructed image has minim...
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Joint demosaicking and denoising consists in reconstructing a color imagefrom the noisy raw data output by the sensor of a digital camera. We adopt a variational formulation in which the reconstructed image has minimal total variation under the constraint of consistency with the available measurements. This way, the recovered color image has smooth chrominance but the sharp edges are maintained and the noise is transferred to the luminance channel. This channel is de-noised subsequently.
Partial volume effects affect the quantitative accuracy of PET images. Many approaches to partial volume correction (PvC) have been proposed, however most rely on additional, patient-specific anatomical information fr...
ISBN:
(纸本)9781467320283
Partial volume effects affect the quantitative accuracy of PET images. Many approaches to partial volume correction (PvC) have been proposed, however most rely on additional, patient-specific anatomical information from structural imaging modalities such as MRI. In order to utilize anatomical data, image registration is required. With the recent advent of simultaneous PET/MRI scanners comes the ability to acquire accurately registered data. In this study, applied eight different PvC techniques to Monte Carlo simulated data, derived from a clinical brain FDG PET/MRI study. reconstruction-based and post-reconstruction PvC methods were evaluated. Their performance was investigated in terms of bias vs. noise, lesion contrast and when faced with registration errors. Excellent quantification, with reduced noise, can be achieved by applying PvC when accurately aligned data are available. reconstruction-based methods produced images with low bias and reduced noise. Post-reconstruction techniques appeared to be more sensitive to registration and segmentation errors. All PvC techniques improved recovery compared to the uncorrected data.
In this work, we propose an adaptive M-estimation scheme for robust image super-resolution. The proposed algorithm relies on a maximum a posteriori (MAP) framework and addresses the presence of outliers in the low res...
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In this work, we propose an adaptive M-estimation scheme for robust image super-resolution. The proposed algorithm relies on a maximum a posteriori (MAP) framework and addresses the presence of outliers in the low resolution images. Moreover, apart from the robust estimation of the high resolution image, the contribution of the method is twofold: (i) the robust computation of the regularization parameters controlling the relative strength of the prior with respect to the data fidelity term and (ii) the robust estimation of the optimal step size in the update of the high resolution image. Experimental results demonstrate that integrating these estimations into a robust framework leads to significant improvement in the accuracy of the high resolution image.
This study is a part of an ongoing effort to develop means to monitor the temperature field during minimally invasive cryosurgery - the destruction of undesired tissues by freezing. In particular, this study focuses o...
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This study is a part of an ongoing effort to develop means to monitor the temperature field during minimally invasive cryosurgery - the destruction of undesired tissues by freezing. In particular, this study focuses on developing a method for temperature-field reconstruction based on data obtained from an array of wireless implantable temperature sensors. Results of this study indicate that the implantable sensors can potentially improve cryosurgery monitoring. Results of this study further demonstrate that the location of the lethal temperature can be identified, which represents an unmet need in current cryosurgery practice.
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