Some novel reconstruction algorithms have recently been proposed to solve the problem of reconstruction from transverse truncated projections of fan-beam scans. This paper introduced and reformulated the exact backpro...Some novel reconstruction algorithms have recently been proposed to solve the problem of reconstruction from transverse truncated projections of fan-beam scans. This paper introduced and reformulated the exact backprojection-filtration （BPF）-type reconstruction algorithm for fan-beam scans based on Zou and Pan＇s work. Subsequently, a legible and implementary BPF algorithm for region-of-interest （ROI） reconstruction is presented using projection data truncated not only in angle-scanning but also in the transverse direction. The algorithm can be widely used for fan-beam full-scans, short-scans, or super-short-scans The algorithm uses less projection data than the preceding super-short-scan. The algorithm is implemented using the Shepp-Logan phantom and some primary results are presented. Some new discoveries and implications of ROI reconstruction from truncated data are discussed, which suggests that the BPF algorithm can be used in the ROI reconstruction from truncated projections.展开更多
In a dynamic CT, the acquired projections are corrupted due to strong dynamic nature of the object, for example: lungs, heart etc. In this paper, we present fan-beam reconstruction algorithm without position-dependent...In a dynamic CT, the acquired projections are corrupted due to strong dynamic nature of the object, for example: lungs, heart etc. In this paper, we present fan-beam reconstruction algorithm without position-dependent backprojection weight which compensates for the time-dependent translational, uniform scaling and rotational deformations occurring in the object of interest during the data acquisition process. We shall also compare the computational cost of the proposed reconstruction algorithm with the existing one which has position-dependent weight. To accomplish the objective listed above, we first formulate admissibility conditions on deformations that is required to exactly reconstruct the object from acquired sequential deformed projections and then derive the reconstruction algorithm to compensate the above listed deformations satisfying the admissibility conditions. For this, 2-D time-dependent deformation model is incorporated in the fan-beam FBP reconstruction algorithm with no backprojection weight, assuming the motion parameters being known. Finally the proposed reconstruction algorithm is evaluated with the motion corrupted projection data simulated on the computer.展开更多
The rotating fan-beam scatterometer （RFSCAT） is a new type of satellite scatterometer that is proposed approximately 10 a ago. However, similar to other rotating scatterometers, relatively larger wind retrieval erro...The rotating fan-beam scatterometer （RFSCAT） is a new type of satellite scatterometer that is proposed approximately 10 a ago. However, similar to other rotating scatterometers, relatively larger wind retrieval errors occur in the nadir and outer regions compared with the middle regions of the swath. For the RFSCAT with the given parameters, a wind direction retrieval accuracy decreases by approximately 9 in the outer regions compared with the middle region. To address this problem, an advanced wind vector retrieval algorithm for the RFSCAT is presented. The new algorithm features an adaptive extension of the range of wind direction for each wind vector cell position across the whole swath according to the distribution histogram of a retrieved wind direction bias. One hundred orbits of Level 2A data are simulated to validate and evaluate the new algorithm. Retrieval experiments demonstrate that the new advanced algorithm can effectively improve the wind direction retrieval accuracy in the nadir and outer regions of the RFSCAT swath. Approximately 1.6 and 9 improvements in the wind direction retrieval are achieved for the wind vector cells located at the nadir and the edge point of the swath, respectively.展开更多
The fan-beam optical sensor is made up of many semiconductor lasers and detectors fixed around the wall alternately at a cross section of pneumatically conveying pipe. When the sensor works, a scanning light source em...The fan-beam optical sensor is made up of many semiconductor lasers and detectors fixed around the wall alternately at a cross section of pneumatically conveying pipe. When the sensor works, a scanning light source emits a 50° lamellar fan-beam through the gas-solid two phase flow, and the projection data resulting extinction effect of solid particles are detected at the same time. With the projection data, the flow rate mass can be calculated, and then the flow image can be reconstructed. In this paper, the design of the sensor including spatial arrangement of the structural parts, basic principle and measurement sensitivity distribution are introduced. The mathematical measurement model of solid mass flow rate is presented together with the testing results.展开更多
In this paper we develop a general exact fan-beam reconstruction algorithm for free-form trajectories not only closed but also unclosed,based on the fan-beam reconstruction formula recently developed by Noo et al.. A ...In this paper we develop a general exact fan-beam reconstruction algorithm for free-form trajectories not only closed but also unclosed,based on the fan-beam reconstruction formula recently developed by Noo et al.. A mathematical proof is then provided with the geometrical explanation of equi-spatial detectors. With this algorithm we can obtain exact region of interest (ROI) reconstruction if and only if every projecting line passing through the ROI intersects the free-form source trajectory,when the projections are not truncated. Furthermore,under the condi- tion that the source-to-detectors distance changes slowly enough relative to the length itself,we obtain a very good approximate reconstruction algorithm,which is the same as the algorithm of the circular trajectory except that the source-to-detectors distance is a function of the rotation angle. Then the algorithms are tested using the Shepp-Logan phantom and the experiment shows that the algorithms can get perfect numerical results.展开更多
Purpose Compared to pixelated crystal detectors,monolithic crystal detectors present more advantages.Without reflective layer between crystal pixel,monolithic crystal detectors provide higher detection efficiency whil...Purpose Compared to pixelated crystal detectors,monolithic crystal detectors present more advantages.Without reflective layer between crystal pixel,monolithic crystal detectors provide higher detection efficiency while being cheaper.Another important feature is that monolithic crystal detectors can provide depth of interaction(DOI)information,which can improve image quality in nuclear imaging systems.In this article,we aim to study a new positioning scheme of this kind of detector in order to push its applications in nuclear imaging systems.Methods Fan-beam collimation and convolutional neural network are combined to reconstruct interaction points in crystal.Firstly,we built a monolithic detector model based on Geant4 and validated this positioning scheme with simulation data.Then,we constructed a monolithic GAGG(Ce)detector and evaluated its performance with experimental data.Results With proposed positioning scheme,in experiment,we obtained~1.7 mm FWHM resolution on average in x-/ydirection,while~2.5 mm FWHM resolution on average in DOI direction for a 33×33×10 mm3 monolithic GAGG(Ce)crystal coupled with 8×8 SiPM array.Conclusion Through simulations and experiments,we validated our positioning scheme,i.e.,fan-beam collimation and convolutional neural network.Convolutional neural network can reconstruct 3D positions of gamma-rays interaction points in a high resolution,and fan-beam collimation can provide high calibration efficiency;with combination of them,we established a high position resolution and high calibration efficiency positioning scheme for monolithic crystal detector.展开更多
基金the National Natural Science Foundation of China (No. 10575059)the Ph.D. Programs Foundation of Ministry of Education of China (No. 20030003074)
文摘Some novel reconstruction algorithms have recently been proposed to solve the problem of reconstruction from transverse truncated projections of fan-beam scans. This paper introduced and reformulated the exact backprojection-filtration （BPF）-type reconstruction algorithm for fan-beam scans based on Zou and Pan＇s work. Subsequently, a legible and implementary BPF algorithm for region-of-interest （ROI） reconstruction is presented using projection data truncated not only in angle-scanning but also in the transverse direction. The algorithm can be widely used for fan-beam full-scans, short-scans, or super-short-scans The algorithm uses less projection data than the preceding super-short-scan. The algorithm is implemented using the Shepp-Logan phantom and some primary results are presented. Some new discoveries and implications of ROI reconstruction from truncated data are discussed, which suggests that the BPF algorithm can be used in the ROI reconstruction from truncated projections.
文摘In a dynamic CT, the acquired projections are corrupted due to strong dynamic nature of the object, for example: lungs, heart etc. In this paper, we present fan-beam reconstruction algorithm without position-dependent backprojection weight which compensates for the time-dependent translational, uniform scaling and rotational deformations occurring in the object of interest during the data acquisition process. We shall also compare the computational cost of the proposed reconstruction algorithm with the existing one which has position-dependent weight. To accomplish the objective listed above, we first formulate admissibility conditions on deformations that is required to exactly reconstruct the object from acquired sequential deformed projections and then derive the reconstruction algorithm to compensate the above listed deformations satisfying the admissibility conditions. For this, 2-D time-dependent deformation model is incorporated in the fan-beam FBP reconstruction algorithm with no backprojection weight, assuming the motion parameters being known. Finally the proposed reconstruction algorithm is evaluated with the motion corrupted projection data simulated on the computer.
基金The National Natural Science Foundation of China under contract Nos 41476152 and 41506206the National High Technology Research and Development Program(863 Program) of China under contract No.2013AA09A505the Major Project on the Integration of Industry,Education,and Research of Guangzhou City of China under contract No.201508020109
文摘The rotating fan-beam scatterometer （RFSCAT） is a new type of satellite scatterometer that is proposed approximately 10 a ago. However, similar to other rotating scatterometers, relatively larger wind retrieval errors occur in the nadir and outer regions compared with the middle regions of the swath. For the RFSCAT with the given parameters, a wind direction retrieval accuracy decreases by approximately 9 in the outer regions compared with the middle region. To address this problem, an advanced wind vector retrieval algorithm for the RFSCAT is presented. The new algorithm features an adaptive extension of the range of wind direction for each wind vector cell position across the whole swath according to the distribution histogram of a retrieved wind direction bias. One hundred orbits of Level 2A data are simulated to validate and evaluate the new algorithm. Retrieval experiments demonstrate that the new advanced algorithm can effectively improve the wind direction retrieval accuracy in the nadir and outer regions of the RFSCAT swath. Approximately 1.6 and 9 improvements in the wind direction retrieval are achieved for the wind vector cells located at the nadir and the edge point of the swath, respectively.
基金Project (No. 04009469) supported by the Natural Science Foundationof Guangdong, China
文摘The fan-beam optical sensor is made up of many semiconductor lasers and detectors fixed around the wall alternately at a cross section of pneumatically conveying pipe. When the sensor works, a scanning light source emits a 50° lamellar fan-beam through the gas-solid two phase flow, and the projection data resulting extinction effect of solid particles are detected at the same time. With the projection data, the flow rate mass can be calculated, and then the flow image can be reconstructed. In this paper, the design of the sensor including spatial arrangement of the structural parts, basic principle and measurement sensitivity distribution are introduced. The mathematical measurement model of solid mass flow rate is presented together with the testing results.
基金Supported by a grant from the Ph.D. Programs Foundation of Ministry of Education of China (No.20030003074) and the National Natural Science Foundation of China (No.10135040).
文摘In this paper we develop a general exact fan-beam reconstruction algorithm for free-form trajectories not only closed but also unclosed,based on the fan-beam reconstruction formula recently developed by Noo et al.. A mathematical proof is then provided with the geometrical explanation of equi-spatial detectors. With this algorithm we can obtain exact region of interest (ROI) reconstruction if and only if every projecting line passing through the ROI intersects the free-form source trajectory,when the projections are not truncated. Furthermore,under the condi- tion that the source-to-detectors distance changes slowly enough relative to the length itself,we obtain a very good approximate reconstruction algorithm,which is the same as the algorithm of the circular trajectory except that the source-to-detectors distance is a function of the rotation angle. Then the algorithms are tested using the Shepp-Logan phantom and the experiment shows that the algorithms can get perfect numerical results.
文摘Purpose Compared to pixelated crystal detectors,monolithic crystal detectors present more advantages.Without reflective layer between crystal pixel,monolithic crystal detectors provide higher detection efficiency while being cheaper.Another important feature is that monolithic crystal detectors can provide depth of interaction(DOI)information,which can improve image quality in nuclear imaging systems.In this article,we aim to study a new positioning scheme of this kind of detector in order to push its applications in nuclear imaging systems.Methods Fan-beam collimation and convolutional neural network are combined to reconstruct interaction points in crystal.Firstly,we built a monolithic detector model based on Geant4 and validated this positioning scheme with simulation data.Then,we constructed a monolithic GAGG(Ce)detector and evaluated its performance with experimental data.Results With proposed positioning scheme,in experiment,we obtained~1.7 mm FWHM resolution on average in x-/ydirection,while~2.5 mm FWHM resolution on average in DOI direction for a 33×33×10 mm3 monolithic GAGG(Ce)crystal coupled with 8×8 SiPM array.Conclusion Through simulations and experiments,we validated our positioning scheme,i.e.,fan-beam collimation and convolutional neural network.Convolutional neural network can reconstruct 3D positions of gamma-rays interaction points in a high resolution,and fan-beam collimation can provide high calibration efficiency;with combination of them,we established a high position resolution and high calibration efficiency positioning scheme for monolithic crystal detector.
