With the advancements in nuclear energy,methods that can accurately obtain the spatial information of radioactive sources have become essential for nuclear energy safety.Coded aperture imaging technology is widely use...With the advancements in nuclear energy,methods that can accurately obtain the spatial information of radioactive sources have become essential for nuclear energy safety.Coded aperture imaging technology is widely used because it provides two-dimensional distribution information of radioactive sources.The coded array is a major component of a coded aperture gamma camera,and it affects the key performance parameters of the camera.Currently,commonly used coded arrays such as uniformly redundant arrays(URAs)and modified uniformly redundant arrays(MURAs)have prime numbers of rows or columns and may lead to wastage of detector pixels.A 16×16 coded array was designed on the basis of an existing 16×16 multi-pixel position-sensitive cadmium zinc telluride detector.The digital signal-to-noise(SNR)ratio of the point spread function at the center of the array is 25.67.Furthermore,Monte Carlo camera models and experimental devices based on rank-13 MURA and rank-16 URA have been constructed.With the same angular resolution,the field size of view under rank-16 URA is 1.53 times that of under rank-13 MURA.Simulations(Am-241,Co-57,Ir-192,Cs-137)and experiments(Co-57)are conducted to compare the imaging performance between rank-16 URA and rank-13 MURA.The contrast-to-noise ratio of the reconstructed image of the rank-16 array is great and only slightly lower than that of rank-13 MURA.However,as the photon energy increases,the gap becomes almost negligible.展开更多
Needs in scintimammography applications,especially for small animal cardiac imaging,lead to develop a small field of view,high spatial resolution gamma camera with a pinhole collimator.However the ideal pinhole collim...Needs in scintimammography applications,especially for small animal cardiac imaging,lead to develop a small field of view,high spatial resolution gamma camera with a pinhole collimator.However the ideal pinhole collimator must keep a compromise between spatial resolution and sensitivity.In order to design a pinhole collimator with an optimized sensitivity and spatial resolution,the spatial resolution and the geometric sensitivity response as a function of the source to collimator distance has been obtained by means of Monte-Carlo simulation for a small field of view gamma camera with a pinhole collimator of various-hole diameters.The results show that the camera with pinhole of 1 mm,1.5 mm and 2 mm diameter has respectively spatial resolution of 1.5 mm,2.25 mm and 3 mm and geometric sensitivity of 0.016%,0.022%and 0.036%,while the source to collimator distance is 3 cm.We chose the pinhole collimator with hole diameter size of 1.2 mm for our the gamma camera designed based on the trade-off between sensitivity and resolution.展开更多
Quality control of Gamma Camera with SPECT System is highly valuable for assurance performance characteristic. We report the performance characteristic of gamma camera by intrinsic calibration and verification measure...Quality control of Gamma Camera with SPECT System is highly valuable for assurance performance characteristic. We report the performance characteristic of gamma camera by intrinsic calibration and verification measurement. The study has been done using the data from Siemens Symbia S Series gamma camera by using a point source 99mTc at the Institute of Nuclear Medicine & Allied Sciences (INMAS), Khulna, Bangladesh. From intrinsic calibration and verification flood series, the integral uniformity for the central field of view (CFOV) has been found in between 4.01% and 2.88% and for the useful field of view (UFOV) has been in between 4.77% and 4.30%. The differential uniformity for the CFOV has been in between 1.53% and 2.04% and for the UFOV has been in between 2.32% and 2.77%. According to Operating Instruction Symbia System S Series manual, uniformity can compensate for values exceeding 10%, however while integral uniformity exceed 7%, have to contract Siemens customer service representative. In conclusion, these results show that the intrinsic uniformity of the gamma camera under this condition is within an acceptable range;thus the gamma camera working in INMAS is performed well.展开更多
A set of point spread functions (PSF) has been obtained by means of Monte-Carlo simulation for asmall gamma camera with a pinhole collimator of various hole diameters. The FOV (field of view) of the camera isexpended ...A set of point spread functions (PSF) has been obtained by means of Monte-Carlo simulation for asmall gamma camera with a pinhole collimator of various hole diameters. The FOV (field of view) of the camera isexpended from 45 mm to 70 mm in diameter. The position dependence of the variances of PSF is presented, and theacceptance for the 140 kev gamma rays is explored. A phantom of 70 mm in diameter was experimentally imaged inthe camera with effective FOV of only 45 mm in diameter.展开更多
A new compact gamma camera for small object imaging has been developed.It consists of a pixelized Nal(T1) scintillator array coupled to a position sensitive photomultiplier tube (Hamamatsu R2486) with a parallel-hole ...A new compact gamma camera for small object imaging has been developed.It consists of a pixelized Nal(T1) scintillator array coupled to a position sensitive photomultiplier tube (Hamamatsu R2486) with a parallel-hole lead collimator.The compact camera has better spatial resolution than Anger camera.The average value of intrinsic spatial resolutions is 2.3 mm (FWHM).The overall spatial resolution (FWHM) is 3,5 and 6 mm at 0,2.5 and 3 mm SCD (source-to-collimator distance),respectively.The phantom studies with the compact camera have demonstrated that parallel-hole collimator gamma camera is a practical technique for nuclear medicine application.展开更多
In gamma camera and single-photon emission computerized tomography, the collimator removes most photons. Here, a gamma camera without collimator utilizes a specific arrangement of detectors. Instead of bending beams(l...In gamma camera and single-photon emission computerized tomography, the collimator removes most photons. Here, a gamma camera without collimator utilizes a specific arrangement of detectors. Instead of bending beams(like a lens) or directing beams(by parallel hole collimator), changes are created in detectors' field of view(FOV), so that each detector's FOV looks different from others. Simulation proved this theory, with 98 detectors(2 cm 9 1.41 cm) arranged in a zigzag manner for Monte Carlo simulation. A radioactive source with energy of140 ke V was situated on the detectors' faces. Sixty projections, each 3(0 –179) apart, were simulated by Monte Carlo N-Particle(MCNP) 4C code, rotating detectors around a radioactive point. The band containing the radioactive source is clearly visible in each projection.Counts obtained after simulation in different projections were reconstructed, and point source location emerged correctly. Simulation of gamma camera with zigzag arrangement of detectors and MCNP-4C code demonstrated that one could string the space and determine radioactive source by image reconstruction without using collimators, solely through these special detectors' distribution.展开更多
The objective of this study is to investigate a high performance and lower cost compact gamma camera module for a multi-head small animal SPECT system. A compact camera module was developed using a thin Lutetium Oxyor...The objective of this study is to investigate a high performance and lower cost compact gamma camera module for a multi-head small animal SPECT system. A compact camera module was developed using a thin Lutetium Oxyorthosilicate （LSO） scintillation crystal slice coupled to a Hamamatsu H8500 position sensitive photomultiplier tube （PSPMT）. A two-stage charge division readout board based on a novel subtractive resistive readout with a truncated center-of-gravity （TCOG） positioning method was developed for the camera. The performance of the camera was evaluated using a flood 99roTe source with a four-quadrant bar-mask phantom. The preliminary experimental results show that the image shrinkage problem associated with the conventional resistive readout can be effectively overcome by the novel subtractive resistive readout with an appropriate fraction subtraction factor. The response output area （ROA） of the camera shown in the flood image was improved up to 34%, and an intrinsic spatial resolution better than 2 mm of detector was achieved. In conclusion, the utilization of a continuous scintillation crystal and a flat-panel PSPMT equipped with a novel subtractive resistive readout is a feasible approach for developing a high performance and lower cost compact gamma camera.展开更多
Purpose Coded-aperture gamma cameras play an important role for homeland security nowadays.They have limitedfield-of-view(FOV)which is a critical parameter for many applications.The FOV can be potentially increased by ...Purpose Coded-aperture gamma cameras play an important role for homeland security nowadays.They have limitedfield-of-view(FOV)which is a critical parameter for many applications.The FOV can be potentially increased by extending it to the penumbra area(partially coded FOV).Methods In this study,we analyzed this artifact phenomenon based on simulating a commercial coded-aperture gamma camera.The camera uses a modified uniformly redundant array(MURA)mask with a basic pattern of rank 11.Its opening angle of the basic pattern to the detector center is 26.36◦which is the commonly used non-artifact FOV(NAFOV).In some applications,the radiation source is a far-field single-point source.Thus,we extend its FOV to 40◦by including a part of the partially coded area,which is a trade-off between the FOV and image quality.Analytical calculations and simulation studies were carried out.The system matrix was calculated using the Sidden’s algorithm.The maximum likelihood expectation maximization(MLEM)reconstruction method was employed.Projections and reconstruction results of the point source at different positions were compared.The second moment of inertia was used as thefigure of merit.Results Results show that projections have periodic similarity with a period of NAFOV,and reconstructions also have periodic artifacts,i.e.,fromθtoθ+NAFOV.Artifacts are the most serious at the edge of the NAFOV.The upper and lower artifacts are more serious than the left and right artifacts due to the difference between the horizontal centerline(tungsten)and vertical centerline(holes expect the center unit)of the mask.Conclusions For a point source with high activity,artifacts can be reduced by increasing the iteration number of the MLEM reconstruction.Even at the edge of NAFOV,the point source can be possibly reconstructed thanks to the large size of the position sensitive detector(PSD)used.The noise will significantly increase artifacts,which may lead to error locate the point source with low activity at some specific positions.展开更多
Background Accurate localization of a low-activity moving radiation source plays an important role in nuclear security and safety.The coded-aperture gamma camera is generally applied to detect a radiation source,but i...Background Accurate localization of a low-activity moving radiation source plays an important role in nuclear security and safety.The coded-aperture gamma camera is generally applied to detect a radiation source,but its reconstruction methods may have some limitations when the radiation source is motional and weak.Purpose The purpose of this paper is to improve the quality of the reconstruction images and the localization accuracy when detecting a low-activity moving radiation source with a gamma camera.Method The CLSTM-KF method consists of the CLSTM network and the Kalman filter.The CLSTM network is applied to improve the CNR of reconstruction images by making an adaptive superposition for sequential reconstruction images decoded by the correlation analysis method.After the CLSTM network,a series of sequential positions would be filtered by the Kalman filter.Results By comparing with the traditional methods of the gamma camera,the CLSTM-KF method performs well in improving both the CNR of reconstruction images and the localization accuracy.Moreover,the computation time of the CLSTM-KF method can also meet the application requirements.Conclusion In summary,the CLSTM-KF method provides a better choice than the traditional methods in locating and tracking a low-activity moving radiation source.展开更多
The pinhole gamma camera is the basis of the newly developed method of high-resolution pinhole single photon emission computed tomography (SPECT). In this paper, a pinhole gamma camera system was examined using the ch...The pinhole gamma camera is the basis of the newly developed method of high-resolution pinhole single photon emission computed tomography (SPECT). In this paper, a pinhole gamma camera system was examined using the channel model of information theory. The model pinhole gamma camera was simplified from a noisy, lossy channel to a noiseless, lossless channel by assuming a plane source. An approximate formula of average mutual information for the pinhole gamma camera was then derived from the model. Imaging experiments validated the applicability of the analytic formula. The findings demonstrated that the pinhole gamma camera can be adequately described using the channel model of information theory, and that average mutual information can be considered a figure of merit for the optimizing design of the pinhole gamma camera.展开更多
The spatial resolution of the gamma-rays camera was measured on a60Co gamma-rays source with edge method. The gamma-rays camera is consisting with rays-fluorescence convertor, optical imaging system, MCP image intensi...The spatial resolution of the gamma-rays camera was measured on a60Co gamma-rays source with edge method. The gamma-rays camera is consisting with rays-fluorescence convertor, optical imaging system, MCP image intensifier, CCD camera, electronic control system and other devices, and is mainly used in the image diagnostics of the intense pulse radiation sources [1]. Due to the relatively big quantum detective efficiency (DQE) and quantum gain of the gamma-rays, etc., the experimental data were processed by averaging multiple images and fitting curves. According to the experimental results, the spatial resolution MTF (modulation transfer function) at the 10% intensity was about 2lp/mm. Meanwhile, because of the relatively big dispersion effects of the fluorescence transmissions in the scintillator and the optical imaging system, the maximal single-noise ratio (SNR) of the camera was found to be about 5:1. In addition, the spatial resolution of the camera was measured with pulse X-rays with 0.3MeV in average energy and exclusion of the effects of secondary electrons from consideration. Accordingly, the spatial resolution MTF at the 10% intensity was about 5lp/mm. This could be an additional evidence to verify the effects of secondary electrons induced by the 1.25MeV gamma-rays in the scintillator upon the spatial resolution. Based on our analysis, the dispersion sizes of the secondary electrons in the scintillator are about 0.4mm-0.6mm. Comparatively, as indicated by the detailed analysis of the spatial resolutions of the MCP image intensifier and CCD devices, both of them have little effect on the spatial resolution of the gamma-rays camera that could be well neglected.展开更多
BACKGROUND^(68)Ga(gallium)-PSMA PET-CT(prostate-specific membrane antigen-directed Positron emission tomography-computed tomography)has established its role in prostate cancer management as targeted molecular imaging....BACKGROUND^(68)Ga(gallium)-PSMA PET-CT(prostate-specific membrane antigen-directed Positron emission tomography-computed tomography)has established its role in prostate cancer management as targeted molecular imaging.However,limited studies are available on the diagnostic accuracy of^(99m)Tc(Technetium)-PSMASPECT/CT.Due to its cost effectiveness and better feasibility,it needs to be explored more extensively for its incorporation into routine clinical practice.AIM To analyse the diagnostic accuracy of^(99m)Tc-PSMA-SPECT/CT for detection of primary prostate carcinoma.METHODS As a prospective study in a tertiary hospital,^(99m)Tc-PSMA-SPECT/CT was performed in 29 outpatients with suspected prostate cancer,with a median age of 66(range:50-82)years.The findings were compared to histopathology as the gold standard.RESULTS Nineteen of twenty-nine patients were positive on^(99m)Tc-PSMA-SPECT/CT,of which 16(84.2%)had prostate cancer on histopathology,while the remaining ten were negative on imaging,of which three had prostate cancer,leading to an overall sensitivity,specificity,and accuracy of 84.2%,70%,and 79.3%,respectively,on visual analysis.Prostate:background and prostate:liver ratios were 37.18±48.85 and 5.35±7.35 in the malignant group,while 6.65±5.17 and 1.14±0.56 in the benign group,respectively.The area under the curve values for prostate:background and prostate:liver ratios were 0.833(95%confidence interval[CI]:0.677-0.990,P=0.005)and 0.767(95%CI:0.596-0.937,P=0.024),respectively,on receiver operator curve analysis.A cut-off value>10.45 for prostate:background ratio(sensitivity 85%and specificity 88.9%),and>1.15 for prostate:liver ratio(sensitivity 75%and specificity of 77.8%respectively)was found to be pertinent to differentiate between the malignant vs benign groups.CONCLUSION^(99m)Tc-PSMA-SPECT/CT shows a promising role in the diagnosis of primary prostate cancer.展开更多
Lanthanum bromide(LaBr_(3))crystal has a high energy resolution and time resolution and has been used in Compton cameras(CCs)over the past few decades.However,LaBr_(3) crystal arrays are difficult to process because L...Lanthanum bromide(LaBr_(3))crystal has a high energy resolution and time resolution and has been used in Compton cameras(CCs)over the past few decades.However,LaBr_(3) crystal arrays are difficult to process because LaBr_(3) is easy to crack and break;thus,few LaBr_(3)-based CC prototypes have been built.In this study,we designed and fabricated a large-pixel LaBr_(3) CC prototype and evaluated its performance with regard to position,energy,and angular resolution.We used two 10×10 LaBr_(3) crystal arrays with a pixel size of 5 mm×5 mm,silicon photomultipliers(SiPMs),and corresponding decoding circuits to construct our prototype.Additionally,a framework based on a Voronoi diagram and a lookup table was developed for list-mode projection data acquisition.Monte Carlo(MC)simulations based on Geant4 and experiments were conducted to evaluate the performance of our CC prototype.The lateral position resolution was 5 mm,and the maximum deviation in the depth direction was 2.5 and 5 mm for the scatterer and absorber,respectively.The corresponding measured energy resolu-tions were 7.65%and 8.44%,respectively,at 511 keV.The experimental results of ^(137)Cs point-like sources were consistent with the MC simulation results with regard to the spatial positions and full widths at half maximum(FWHMs).The angular resolution of the fabricated prototype was approximately 6°when a point-like ^(137)Cs source was centrally placed at a distance of 5 cm from the scatterer.We proposed and investigated a large-pixel LaBr_(3) CC for the first time and verified its feasibility for use in accurate spatial positioning of radiative sources with a high angular resolution.The proposed CC can satisfy the requirements of radiative source imaging and positioning in the nuclear industry and medical applications.展开更多
The diagnostic methods for the profile of the radiation source were estab-lished at first based on the pinhole imaging principle. In this paper, the relationships among various parameters of the gamma-rays crammer suc...The diagnostic methods for the profile of the radiation source were estab-lished at first based on the pinhole imaging principle. In this paper, the relationships among various parameters of the gamma-rays crammer such as the modulation transfer function (MTF), the noise power spectrum (NPS), the signal-noise ratio (SNR) and the detective quantum efficiency (DQE) are developed and studied experimentally on the cobalt radiation source. The image diagnostic system is consisting with rays-fluorescence convertor (YAG crystal), optical imaging system, MCP image intensifier, CCD camera and other devices. The spatial resolution of the modulation transfer function (MTF) at 10% intensity was measured as 1 lp/mm by knife-edge method. The quantum of the measurement system is about 150 under weak radiation condition due to the single particle detection efficiency of the system. The dynamic range was inferred preliminarily as about 437. The required radiation intensity was calculated using the experiment result for the (SNR) = 1, 5, 10, respectively. The theoretical investigation results show that the radiation image with (SNR) = 1 can be only obtained when the pinhole diameter is 0.7 mm, object distance and image distance are both 200 cm, and the radiation intensity is about 1.0 × 1012 Sr-1·cm-2.展开更多
基金supported by the National Natural Science Foundation of China(No.11675078)the Primary Research and Development Plan of Jiangsu Province(No.BE2017729)the Foundation of Graduate Innovation Center in NUAA(No.kfjj20190614)。
文摘With the advancements in nuclear energy,methods that can accurately obtain the spatial information of radioactive sources have become essential for nuclear energy safety.Coded aperture imaging technology is widely used because it provides two-dimensional distribution information of radioactive sources.The coded array is a major component of a coded aperture gamma camera,and it affects the key performance parameters of the camera.Currently,commonly used coded arrays such as uniformly redundant arrays(URAs)and modified uniformly redundant arrays(MURAs)have prime numbers of rows or columns and may lead to wastage of detector pixels.A 16×16 coded array was designed on the basis of an existing 16×16 multi-pixel position-sensitive cadmium zinc telluride detector.The digital signal-to-noise(SNR)ratio of the point spread function at the center of the array is 25.67.Furthermore,Monte Carlo camera models and experimental devices based on rank-13 MURA and rank-16 URA have been constructed.With the same angular resolution,the field size of view under rank-16 URA is 1.53 times that of under rank-13 MURA.Simulations(Am-241,Co-57,Ir-192,Cs-137)and experiments(Co-57)are conducted to compare the imaging performance between rank-16 URA and rank-13 MURA.The contrast-to-noise ratio of the reconstructed image of the rank-16 array is great and only slightly lower than that of rank-13 MURA.However,as the photon energy increases,the gap becomes almost negligible.
基金Supported by National Foundation of Nature Science of China(No.10275063)
文摘Needs in scintimammography applications,especially for small animal cardiac imaging,lead to develop a small field of view,high spatial resolution gamma camera with a pinhole collimator.However the ideal pinhole collimator must keep a compromise between spatial resolution and sensitivity.In order to design a pinhole collimator with an optimized sensitivity and spatial resolution,the spatial resolution and the geometric sensitivity response as a function of the source to collimator distance has been obtained by means of Monte-Carlo simulation for a small field of view gamma camera with a pinhole collimator of various-hole diameters.The results show that the camera with pinhole of 1 mm,1.5 mm and 2 mm diameter has respectively spatial resolution of 1.5 mm,2.25 mm and 3 mm and geometric sensitivity of 0.016%,0.022%and 0.036%,while the source to collimator distance is 3 cm.We chose the pinhole collimator with hole diameter size of 1.2 mm for our the gamma camera designed based on the trade-off between sensitivity and resolution.
文摘Quality control of Gamma Camera with SPECT System is highly valuable for assurance performance characteristic. We report the performance characteristic of gamma camera by intrinsic calibration and verification measurement. The study has been done using the data from Siemens Symbia S Series gamma camera by using a point source 99mTc at the Institute of Nuclear Medicine & Allied Sciences (INMAS), Khulna, Bangladesh. From intrinsic calibration and verification flood series, the integral uniformity for the central field of view (CFOV) has been found in between 4.01% and 2.88% and for the useful field of view (UFOV) has been in between 4.77% and 4.30%. The differential uniformity for the CFOV has been in between 1.53% and 2.04% and for the UFOV has been in between 2.32% and 2.77%. According to Operating Instruction Symbia System S Series manual, uniformity can compensate for values exceeding 10%, however while integral uniformity exceed 7%, have to contract Siemens customer service representative. In conclusion, these results show that the intrinsic uniformity of the gamma camera under this condition is within an acceptable range;thus the gamma camera working in INMAS is performed well.
基金Supported by the National Natural Science Foundation of China(10275063)
文摘A set of point spread functions (PSF) has been obtained by means of Monte-Carlo simulation for asmall gamma camera with a pinhole collimator of various hole diameters. The FOV (field of view) of the camera isexpended from 45 mm to 70 mm in diameter. The position dependence of the variances of PSF is presented, and theacceptance for the 140 kev gamma rays is explored. A phantom of 70 mm in diameter was experimentally imaged inthe camera with effective FOV of only 45 mm in diameter.
基金Supported by National Natural Science Foundation of China (No.10275063)
文摘A new compact gamma camera for small object imaging has been developed.It consists of a pixelized Nal(T1) scintillator array coupled to a position sensitive photomultiplier tube (Hamamatsu R2486) with a parallel-hole lead collimator.The compact camera has better spatial resolution than Anger camera.The average value of intrinsic spatial resolutions is 2.3 mm (FWHM).The overall spatial resolution (FWHM) is 3,5 and 6 mm at 0,2.5 and 3 mm SCD (source-to-collimator distance),respectively.The phantom studies with the compact camera have demonstrated that parallel-hole collimator gamma camera is a practical technique for nuclear medicine application.
基金supported by grants from Rafsanjan University of Medical Sciences,Rafsanjan,Iran
文摘In gamma camera and single-photon emission computerized tomography, the collimator removes most photons. Here, a gamma camera without collimator utilizes a specific arrangement of detectors. Instead of bending beams(like a lens) or directing beams(by parallel hole collimator), changes are created in detectors' field of view(FOV), so that each detector's FOV looks different from others. Simulation proved this theory, with 98 detectors(2 cm 9 1.41 cm) arranged in a zigzag manner for Monte Carlo simulation. A radioactive source with energy of140 ke V was situated on the detectors' faces. Sixty projections, each 3(0 –179) apart, were simulated by Monte Carlo N-Particle(MCNP) 4C code, rotating detectors around a radioactive point. The band containing the radioactive source is clearly visible in each projection.Counts obtained after simulation in different projections were reconstructed, and point source location emerged correctly. Simulation of gamma camera with zigzag arrangement of detectors and MCNP-4C code demonstrated that one could string the space and determine radioactive source by image reconstruction without using collimators, solely through these special detectors' distribution.
基金Supported by National Natural Science Foundation of China (30570520, 10875162)
文摘The objective of this study is to investigate a high performance and lower cost compact gamma camera module for a multi-head small animal SPECT system. A compact camera module was developed using a thin Lutetium Oxyorthosilicate （LSO） scintillation crystal slice coupled to a Hamamatsu H8500 position sensitive photomultiplier tube （PSPMT）. A two-stage charge division readout board based on a novel subtractive resistive readout with a truncated center-of-gravity （TCOG） positioning method was developed for the camera. The performance of the camera was evaluated using a flood 99roTe source with a four-quadrant bar-mask phantom. The preliminary experimental results show that the image shrinkage problem associated with the conventional resistive readout can be effectively overcome by the novel subtractive resistive readout with an appropriate fraction subtraction factor. The response output area （ROA） of the camera shown in the flood image was improved up to 34%, and an intrinsic spatial resolution better than 2 mm of detector was achieved. In conclusion, the utilization of a continuous scintillation crystal and a flat-panel PSPMT equipped with a novel subtractive resistive readout is a feasible approach for developing a high performance and lower cost compact gamma camera.
基金supported in part by National Natural Science Foundation of China(No.11975044&No.81727807)Fundamental Research Funds for the Central Universities(No.FRFTP-19-019A3)+1 种基金Science&Technology on Reliability&Environmental Engineering Laboratory(No.6142004180205)Beijing Nova Program of Science and Technology(No.Z191199991119119).
文摘Purpose Coded-aperture gamma cameras play an important role for homeland security nowadays.They have limitedfield-of-view(FOV)which is a critical parameter for many applications.The FOV can be potentially increased by extending it to the penumbra area(partially coded FOV).Methods In this study,we analyzed this artifact phenomenon based on simulating a commercial coded-aperture gamma camera.The camera uses a modified uniformly redundant array(MURA)mask with a basic pattern of rank 11.Its opening angle of the basic pattern to the detector center is 26.36◦which is the commonly used non-artifact FOV(NAFOV).In some applications,the radiation source is a far-field single-point source.Thus,we extend its FOV to 40◦by including a part of the partially coded area,which is a trade-off between the FOV and image quality.Analytical calculations and simulation studies were carried out.The system matrix was calculated using the Sidden’s algorithm.The maximum likelihood expectation maximization(MLEM)reconstruction method was employed.Projections and reconstruction results of the point source at different positions were compared.The second moment of inertia was used as thefigure of merit.Results Results show that projections have periodic similarity with a period of NAFOV,and reconstructions also have periodic artifacts,i.e.,fromθtoθ+NAFOV.Artifacts are the most serious at the edge of the NAFOV.The upper and lower artifacts are more serious than the left and right artifacts due to the difference between the horizontal centerline(tungsten)and vertical centerline(holes expect the center unit)of the mask.Conclusions For a point source with high activity,artifacts can be reduced by increasing the iteration number of the MLEM reconstruction.Even at the edge of NAFOV,the point source can be possibly reconstructed thanks to the large size of the position sensitive detector(PSD)used.The noise will significantly increase artifacts,which may lead to error locate the point source with low activity at some specific positions.
基金the National Natural Science Foundation of China(No.11905229).
文摘Background Accurate localization of a low-activity moving radiation source plays an important role in nuclear security and safety.The coded-aperture gamma camera is generally applied to detect a radiation source,but its reconstruction methods may have some limitations when the radiation source is motional and weak.Purpose The purpose of this paper is to improve the quality of the reconstruction images and the localization accuracy when detecting a low-activity moving radiation source with a gamma camera.Method The CLSTM-KF method consists of the CLSTM network and the Kalman filter.The CLSTM network is applied to improve the CNR of reconstruction images by making an adaptive superposition for sequential reconstruction images decoded by the correlation analysis method.After the CLSTM network,a series of sequential positions would be filtered by the Kalman filter.Results By comparing with the traditional methods of the gamma camera,the CLSTM-KF method performs well in improving both the CNR of reconstruction images and the localization accuracy.Moreover,the computation time of the CLSTM-KF method can also meet the application requirements.Conclusion In summary,the CLSTM-KF method provides a better choice than the traditional methods in locating and tracking a low-activity moving radiation source.
文摘The pinhole gamma camera is the basis of the newly developed method of high-resolution pinhole single photon emission computed tomography (SPECT). In this paper, a pinhole gamma camera system was examined using the channel model of information theory. The model pinhole gamma camera was simplified from a noisy, lossy channel to a noiseless, lossless channel by assuming a plane source. An approximate formula of average mutual information for the pinhole gamma camera was then derived from the model. Imaging experiments validated the applicability of the analytic formula. The findings demonstrated that the pinhole gamma camera can be adequately described using the channel model of information theory, and that average mutual information can be considered a figure of merit for the optimizing design of the pinhole gamma camera.
文摘The spatial resolution of the gamma-rays camera was measured on a60Co gamma-rays source with edge method. The gamma-rays camera is consisting with rays-fluorescence convertor, optical imaging system, MCP image intensifier, CCD camera, electronic control system and other devices, and is mainly used in the image diagnostics of the intense pulse radiation sources [1]. Due to the relatively big quantum detective efficiency (DQE) and quantum gain of the gamma-rays, etc., the experimental data were processed by averaging multiple images and fitting curves. According to the experimental results, the spatial resolution MTF (modulation transfer function) at the 10% intensity was about 2lp/mm. Meanwhile, because of the relatively big dispersion effects of the fluorescence transmissions in the scintillator and the optical imaging system, the maximal single-noise ratio (SNR) of the camera was found to be about 5:1. In addition, the spatial resolution of the camera was measured with pulse X-rays with 0.3MeV in average energy and exclusion of the effects of secondary electrons from consideration. Accordingly, the spatial resolution MTF at the 10% intensity was about 5lp/mm. This could be an additional evidence to verify the effects of secondary electrons induced by the 1.25MeV gamma-rays in the scintillator upon the spatial resolution. Based on our analysis, the dispersion sizes of the secondary electrons in the scintillator are about 0.4mm-0.6mm. Comparatively, as indicated by the detailed analysis of the spatial resolutions of the MCP image intensifier and CCD devices, both of them have little effect on the spatial resolution of the gamma-rays camera that could be well neglected.
文摘BACKGROUND^(68)Ga(gallium)-PSMA PET-CT(prostate-specific membrane antigen-directed Positron emission tomography-computed tomography)has established its role in prostate cancer management as targeted molecular imaging.However,limited studies are available on the diagnostic accuracy of^(99m)Tc(Technetium)-PSMASPECT/CT.Due to its cost effectiveness and better feasibility,it needs to be explored more extensively for its incorporation into routine clinical practice.AIM To analyse the diagnostic accuracy of^(99m)Tc-PSMA-SPECT/CT for detection of primary prostate carcinoma.METHODS As a prospective study in a tertiary hospital,^(99m)Tc-PSMA-SPECT/CT was performed in 29 outpatients with suspected prostate cancer,with a median age of 66(range:50-82)years.The findings were compared to histopathology as the gold standard.RESULTS Nineteen of twenty-nine patients were positive on^(99m)Tc-PSMA-SPECT/CT,of which 16(84.2%)had prostate cancer on histopathology,while the remaining ten were negative on imaging,of which three had prostate cancer,leading to an overall sensitivity,specificity,and accuracy of 84.2%,70%,and 79.3%,respectively,on visual analysis.Prostate:background and prostate:liver ratios were 37.18±48.85 and 5.35±7.35 in the malignant group,while 6.65±5.17 and 1.14±0.56 in the benign group,respectively.The area under the curve values for prostate:background and prostate:liver ratios were 0.833(95%confidence interval[CI]:0.677-0.990,P=0.005)and 0.767(95%CI:0.596-0.937,P=0.024),respectively,on receiver operator curve analysis.A cut-off value>10.45 for prostate:background ratio(sensitivity 85%and specificity 88.9%),and>1.15 for prostate:liver ratio(sensitivity 75%and specificity of 77.8%respectively)was found to be pertinent to differentiate between the malignant vs benign groups.CONCLUSION^(99m)Tc-PSMA-SPECT/CT shows a promising role in the diagnosis of primary prostate cancer.
文摘Lanthanum bromide(LaBr_(3))crystal has a high energy resolution and time resolution and has been used in Compton cameras(CCs)over the past few decades.However,LaBr_(3) crystal arrays are difficult to process because LaBr_(3) is easy to crack and break;thus,few LaBr_(3)-based CC prototypes have been built.In this study,we designed and fabricated a large-pixel LaBr_(3) CC prototype and evaluated its performance with regard to position,energy,and angular resolution.We used two 10×10 LaBr_(3) crystal arrays with a pixel size of 5 mm×5 mm,silicon photomultipliers(SiPMs),and corresponding decoding circuits to construct our prototype.Additionally,a framework based on a Voronoi diagram and a lookup table was developed for list-mode projection data acquisition.Monte Carlo(MC)simulations based on Geant4 and experiments were conducted to evaluate the performance of our CC prototype.The lateral position resolution was 5 mm,and the maximum deviation in the depth direction was 2.5 and 5 mm for the scatterer and absorber,respectively.The corresponding measured energy resolu-tions were 7.65%and 8.44%,respectively,at 511 keV.The experimental results of ^(137)Cs point-like sources were consistent with the MC simulation results with regard to the spatial positions and full widths at half maximum(FWHMs).The angular resolution of the fabricated prototype was approximately 6°when a point-like ^(137)Cs source was centrally placed at a distance of 5 cm from the scatterer.We proposed and investigated a large-pixel LaBr_(3) CC for the first time and verified its feasibility for use in accurate spatial positioning of radiative sources with a high angular resolution.The proposed CC can satisfy the requirements of radiative source imaging and positioning in the nuclear industry and medical applications.
文摘The diagnostic methods for the profile of the radiation source were estab-lished at first based on the pinhole imaging principle. In this paper, the relationships among various parameters of the gamma-rays crammer such as the modulation transfer function (MTF), the noise power spectrum (NPS), the signal-noise ratio (SNR) and the detective quantum efficiency (DQE) are developed and studied experimentally on the cobalt radiation source. The image diagnostic system is consisting with rays-fluorescence convertor (YAG crystal), optical imaging system, MCP image intensifier, CCD camera and other devices. The spatial resolution of the modulation transfer function (MTF) at 10% intensity was measured as 1 lp/mm by knife-edge method. The quantum of the measurement system is about 150 under weak radiation condition due to the single particle detection efficiency of the system. The dynamic range was inferred preliminarily as about 437. The required radiation intensity was calculated using the experiment result for the (SNR) = 1, 5, 10, respectively. The theoretical investigation results show that the radiation image with (SNR) = 1 can be only obtained when the pinhole diameter is 0.7 mm, object distance and image distance are both 200 cm, and the radiation intensity is about 1.0 × 1012 Sr-1·cm-2.
