A system matrix (SM) is the basic component of iterative image reconstruction algorithms. Calculation of the SM needs a considerable amount of time due to an enormous number of lines of response (LORs) being modeled. ...
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A system matrix (SM) is the basic component of iterative image reconstruction algorithms. Calculation of the SM needs a considerable amount of time due to an enormous number of lines of response (LORs) being modeled. In this study, we developed a technique based on a piece-wise calculation method in which symmetry and further division of the voxels are applied. The detector response function for all detectable pairs of photons along certain LORs originating from each voxel is calculated analytically. The total number of LORs in 300 x 300 x 120 voxels (with 2 x 2 x 2 mm(3)) is similar to 44 billion, and the SM was calculated by the use of three different computers independently;the calculation time was 5 h. The SM took 5 days when calculated by the use of the conventional method (where symmetry and the piece-wise method are not used). The sensitivity correction factor was stored;it had a size of 42 MB in a four-byte computer memory.
Many photoacoustic imaging systems use back projection-based image reconstruction algorithms to estimate photoacoustic source locations from the time-of-flight pressure information collected by either a scanned single...
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ISBN:
(纸本)9780819470317
Many photoacoustic imaging systems use back projection-based image reconstruction algorithms to estimate photoacoustic source locations from the time-of-flight pressure information collected by either a scanned single transducer or an array of stationary transducer elements. Accurate imagereconstruction requires that the transducer(s) locations relative to the imaged volume and the transducer(s) sensitivity distribution within the imaged volume be accurately known. The objective of this work was to develop a method for estimation of the sensitivity distribution of a transducer array. Our approach was to capture for each transducer element the response to a photoacoustic point source that was robotically scanned throughout the imaging volume. The temporally resolved photoacoustic signal was then processed to obtain the relative transducer sensitivity at the source location. We performed a scan over a transducer array fabricated in our laboratory that consisted of twelve 3 mm elements in a 30 mm annular ring arrangement. We measured both the sensitivity distribution of single elements, from which the spatial and angular sensitivity profiles were extracted, as well as the simultaneous response of all transducer elements, which allowed us to locate the effective position of each element, but also highlighted the non-uniformity between transducers' response of up to 20%. We present these and other measured parameters, and discuss their significance as well as their effect on our image reconstruction algorithm.
Novel geometrical designs of computed tomography (CT) scanners in combination with novel image reconstruction algorithms promise to reduce ionizing radiation exposure to the patient in CT scans. While the sampling den...
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ISBN:
(纸本)9780819480231
Novel geometrical designs of computed tomography (CT) scanners in combination with novel image reconstruction algorithms promise to reduce ionizing radiation exposure to the patient in CT scans. While the sampling density of the Field Of View (FOV) is retained, the image quality can even be increased in contrast to conventional CT scanners. In this study, we present first images obtained with a novel CT scanner that we developed in our working group. In this open CT system with irradiation within a fan beam, parallel Radon data are directly obtained for imagereconstruction using the OPED (Orthogonal Polynomial Expansion on the Disk) algorithm. This algorithm uses Radon data directly, i.e., without any further data processing such as rebinning and interpolation. We experimentally test theoretical predictions for this system by quantifying image quality parameters in comparison with corresponding parameters that are derived from the images of a conventional scanner of the 3(rd) generation. The modulation transfer function (MTF) and noise power spectrum (NPS) are determined using a test phantom. The novel CT system quantitatively shows the same noise property as the conventional scanner. The resolution that is reached in the center of a reconstructed image is nearly identical for both scanner types. But we found that the resolution that is achieved in the novel CT system does not depend on the image position while the MTF of the conventional scanner decreases for radially outer regions of the image.
In the Electrical Capacitance Tomography, the distribution of permittivity in the pipe can be estimated using the capacitance measurements with help of the reconstructionalgorithms. In this paper, the permittivity di...
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ISBN:
(纸本)9781467390989
In the Electrical Capacitance Tomography, the distribution of permittivity in the pipe can be estimated using the capacitance measurements with help of the reconstructionalgorithms. In this paper, the permittivity distribution was reconstructed with Kalman Filter and several simulations were carried out to evaluate the effect of different initial values of the grey values in the image and the estimate error covariance on reconstructed image. In addition, Landweber and Tikhonov were used to reconstruct the object to compare with the reconstructed effect of Kalman Filter with suitable initial values.
Accurate measurement of the concentration of pulverized-coal in various pipes as a guidance to proper control plays a key role in assuring safe and economic operation of a pulverized coal-fired boiler during the combu...
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ISBN:
(纸本)9783037858042
Accurate measurement of the concentration of pulverized-coal in various pipes as a guidance to proper control plays a key role in assuring safe and economic operation of a pulverized coal-fired boiler during the combustion process. Experimental studies are carried out on the measurement of a lean mass flow in a pneumatic conveying pipeline using electrical capacitance tomography(ECT). A cyclone separator is employed in this system where the sensors are placed in order to compensate the inhomogeneity of the sensor sensitivity. The distribution of void fraction in radial direction, the average void fraction and the wavy characteristics are analyzed. The feasibility and reliability of the method are verified by the experimental results.
On the basis of analyzing ray and electronical tomographic system fundamental and its advantage and disadvantage, an electrical impedance tomography system used in flow pattern recognition of multiphase flow is introd...
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ISBN:
(纸本)9781424425020
On the basis of analyzing ray and electronical tomographic system fundamental and its advantage and disadvantage, an electrical impedance tomography system used in flow pattern recognition of multiphase flow is introduced, and a new algorithm used in EIT imagereconstruction is proposed. This algorithm will improve the convergence speed and the quality of the imagereconstruction by using the method of mixed genetic algorithm and landweber iteration algorithm. The experimental results show that the EIT system is an effective system for multiphase flow measurement, the algorithm has the advantage of good convergence stability and rapid convergence rate.
imagereconstruction of Electrical Resistance Tomography (ERT) is an ill-posed inverse problem. In this work, a new image reconstruction algorithm of ERT for the measurement of two-phase flow is studied. The new algor...
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ISBN:
(纸本)9787302139225
imagereconstruction of Electrical Resistance Tomography (ERT) is an ill-posed inverse problem. In this work, a new image reconstruction algorithm of ERT for the measurement of two-phase flow is studied. The new algorithm is a hybrid of Tikhonov regularization principle and Algebraic reconstruction Technique (ART) algorithm. Tikhonov regularization principle is introduced to overcome the instability problem of initial imagereconstruction. And, ART algorithm is used to improve the image quality of the original reconstructed image. Experimental results show that the hybrid image reconstruction algorithm can efficiently overcome the ill-posed problem of imagereconstruction of ERT and is superior to the sensitivity coefficient algorithm. It is respected to be used in industry.
Ultrasonic tomography (UT) has been widely applied in industrial process imaging. image reconstruction algorithm is one of the most popular research interests in UT field. In this paper, a novel method for constructio...
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ISBN:
(纸本)9781538616208
Ultrasonic tomography (UT) has been widely applied in industrial process imaging. image reconstruction algorithm is one of the most popular research interests in UT field. In this paper, a novel method for construction of sensitivity matrix was proposed. The method can be used to improve linear back projection (LBP) algorithm for detection of the gas bubble distribution in a gas/liquid two-phase bubbly flow. Hybrid reconstruction (HR) algorithm was introduced to improve imagereconstruction performance based on the presented method. Furthermore, a series of models have been established to evaluate the performance of the above algorithms. Three quantitative evaluation criteria were selected to evaluate the quality of reconstructed images. The results indicate that the fan-shaped sensitivity matrix is feasible and valid for the LBP algorithm in improving image quality.
It is important to improve quality and rate of reconstructionimage, which also is a hot spot for ECT researchers, in order to realize measurement on-line for multi-phase flow parameters of high-speed industry process...
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ISBN:
(纸本)9780819489913
It is important to improve quality and rate of reconstructionimage, which also is a hot spot for ECT researchers, in order to realize measurement on-line for multi-phase flow parameters of high-speed industry processes by using electrical capacitance tomography (ECT). In this paper, key issues in designing high-speed ECT system including algorithms and circuits (small capacitance measurement module, data acquisition control module and communication module) are analyzed and discussed. To a great extent, the speed of hardware circuit depends on the performance of small capacitance measurement circuit. This paper presented ac-based and active differential capacitance measuring circuits, which are suitable for rapidly ECT imaging. The real time performances and imagereconstruction process of ECT system are discussed. Key technology and methods for high-speed ECT system are given in this paper.
We propose a 3D scheme for time-domain fluorescence molecular tomography within the normalized Born-ratio formulation. A finite element method solution to the Laplace transformed time-domain coupled diffusion equation...
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ISBN:
(纸本)9780819474209
We propose a 3D scheme for time-domain fluorescence molecular tomography within the normalized Born-ratio formulation. A finite element method solution to the Laplace transformed time-domain coupled diffusion equations is employed as the forward model, and the resultant linear inversions at two distinct transform-factors are solved with an algebraic reconstruction technique to separate fluorescent yield and lifetime images. By use of a multichannel time-correlation single photon counting system, we experimentally validate that the proposed scheme can achieve simultaneous reconstruction of the fluorescent yield and lifetime distributions with a reasonable accuracy.
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