Pub Date : 2003-12-01DOI: 10.1109/NSSMIC.2003.1352269
T. Peterson, Donald W. Wilson, H. Barrett
We have developed a prototype ultrahigh-resolution small-animal imaging system that utilizes a silicon detector with a multiple-pinhole aperture. This system is suitable for imaging low-energy photons such as those from I-125 decay (27.2-35.5 keV) or the X-rays from I-123 decay (27.2-31.8 keV). The silicon detector is a double-sided strip detector of 300-micrometer thickness and 50-micrometer strip pitch, with 560 strips on one side and 1260 strips on the other. The readout utilizes VaTaGP2.2 ASICs from IDEAS ASA, Norway. When the detector is coupled with a multiple-pinhole aperture and operated in a synthetic-collimator configuration it should be possible to do tomographic image reconstructions without rotation of either the object or imager.
{"title":"Ultrahigh-resolution small-animal imaging using a silicon detector","authors":"T. Peterson, Donald W. Wilson, H. Barrett","doi":"10.1109/NSSMIC.2003.1352269","DOIUrl":"https://doi.org/10.1109/NSSMIC.2003.1352269","url":null,"abstract":"We have developed a prototype ultrahigh-resolution small-animal imaging system that utilizes a silicon detector with a multiple-pinhole aperture. This system is suitable for imaging low-energy photons such as those from I-125 decay (27.2-35.5 keV) or the X-rays from I-123 decay (27.2-31.8 keV). The silicon detector is a double-sided strip detector of 300-micrometer thickness and 50-micrometer strip pitch, with 560 strips on one side and 1260 strips on the other. The readout utilizes VaTaGP2.2 ASICs from IDEAS ASA, Norway. When the detector is coupled with a multiple-pinhole aperture and operated in a synthetic-collimator configuration it should be possible to do tomographic image reconstructions without rotation of either the object or imager.","PeriodicalId":186175,"journal":{"name":"2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515)","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128764282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-12-01DOI: 10.1109/NSSMIC.2003.1352358
L. Meng, N. Clinthorne
This work presents a design study of using multiple pinhole apertures in small animal SPECT imaging applications. The SPECT system is based on the use of an existing ADAC gamma camera. For quantifying the performance of a detector design, we used the minimum achievable variance at several locations in the images, given some constraints on the resulting spatial resolution. This approach was formerly proposed as the Uniform Cramer-Rao Bound (UCRB). In this work, we propose to use a resolution constraint that is imposed on the mean gradient vector. This partially overcomes the limitations of the former UCRB approach based on the bias-gradient norm constraint. We applied this method for studying the effect of design parameters, such as number of pinholes and pinhole size, on the performance of the detector system.
{"title":"Multiple pinhole aperture design using a modified Uniform Cramer-Rao Bound","authors":"L. Meng, N. Clinthorne","doi":"10.1109/NSSMIC.2003.1352358","DOIUrl":"https://doi.org/10.1109/NSSMIC.2003.1352358","url":null,"abstract":"This work presents a design study of using multiple pinhole apertures in small animal SPECT imaging applications. The SPECT system is based on the use of an existing ADAC gamma camera. For quantifying the performance of a detector design, we used the minimum achievable variance at several locations in the images, given some constraints on the resulting spatial resolution. This approach was formerly proposed as the Uniform Cramer-Rao Bound (UCRB). In this work, we propose to use a resolution constraint that is imposed on the mean gradient vector. This partially overcomes the limitations of the former UCRB approach based on the bias-gradient norm constraint. We applied this method for studying the effect of design parameters, such as number of pinholes and pinhole size, on the performance of the detector system.","PeriodicalId":186175,"journal":{"name":"2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515)","volume":"806 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130474357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-12-01DOI: 10.1109/NSSMIC.2003.1352420
A. Rahmim, P. Bloomfield, S. Houle, M. Lenox, C. Michel, V. Sossi
With continuous improvements in spatial resolution of PET scanners, small patient movements during PET imaging become a significant source of resolution degradation. This work explores incorporation of motion information into EM reconstruction algorithms. Precorrection of the data for attenuation and normalization as well as weighted schemes, in which these correction factors are incorporated into the system matrix, are considered. An important issue addressed is the existence of LORs corresponding to no actual pairs of detectors and their motion-induced "interaction" with the detectable LORs. An example of this is a scanner design with gaps existing in-between the detector heads. It is shown that to properly account for such LORs in histogram-mode and list-mode EM reconstructions, in addition to motion-correction of the data, the algorithms themselves must be modified. This modification is implemented by including time-weighted sensitivity correction factors. A practically feasible method for calculation of sensitivity factors is derived based on image-space monitoring of voxel motion during the scan.
{"title":"Practically feasible histogram-mode and list-mode EM reconstructions with full motion compensation","authors":"A. Rahmim, P. Bloomfield, S. Houle, M. Lenox, C. Michel, V. Sossi","doi":"10.1109/NSSMIC.2003.1352420","DOIUrl":"https://doi.org/10.1109/NSSMIC.2003.1352420","url":null,"abstract":"With continuous improvements in spatial resolution of PET scanners, small patient movements during PET imaging become a significant source of resolution degradation. This work explores incorporation of motion information into EM reconstruction algorithms. Precorrection of the data for attenuation and normalization as well as weighted schemes, in which these correction factors are incorporated into the system matrix, are considered. An important issue addressed is the existence of LORs corresponding to no actual pairs of detectors and their motion-induced \"interaction\" with the detectable LORs. An example of this is a scanner design with gaps existing in-between the detector heads. It is shown that to properly account for such LORs in histogram-mode and list-mode EM reconstructions, in addition to motion-correction of the data, the algorithms themselves must be modified. This modification is implemented by including time-weighted sensitivity correction factors. A practically feasible method for calculation of sensitivity factors is derived based on image-space monitoring of voxel motion during the scan.","PeriodicalId":186175,"journal":{"name":"2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515)","volume":"128 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132545428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-12-01DOI: 10.1109/NSSMIC.2003.1352511
S.A. Sawyer, E. Frey, B. He, Yuchuan Wang, B. Tsui
Typical microCT systems for in vivo small animal imaging have a total acquisition time on the order of 10 minutes for a single scan, with the detector read-out time often a major contributor to acquisition length. Reduction of the portion of the scan time spent in read-out can be achieved through short-scan acquisition. Knowledge of and correction for geometric misalignments is another crucial factor in obtaining high quality microCT images. In this work, we have implemented a short-scan Feldkamp algorithm with correction geometric misalignment. Due to our system misalignments, severe ghosting artifacts are present in the reconstruction. We have implemented a reconstruction algorithm with correction for the misalignments which eliminates the ghosting artifacts. Comparisons of full-scan and short-scan reconstructions of both phantom and mouse data show similar image quality. We have also compared short-scan reconstructions to full-scan reconstructions from projection data with roughly the same total acquisition time. In this case, blurring is visible in sagittal slices of the full-scan reconstructions that is not present in the short-scan reconstructions. Short-scan acquisition provides reduction of the total acquisition time resulting in microCT images without the loss in image quality obtained by simply reducing the number of projections for a full-scan acquisition. Axis of rotation horizontal transversal off-center shift and the X-ray source horizontal transversal shift are the most sensitive parameters.
{"title":"Implementation of short-scan reconstruction with compensation for geometric alignment for a microCT system","authors":"S.A. Sawyer, E. Frey, B. He, Yuchuan Wang, B. Tsui","doi":"10.1109/NSSMIC.2003.1352511","DOIUrl":"https://doi.org/10.1109/NSSMIC.2003.1352511","url":null,"abstract":"Typical microCT systems for in vivo small animal imaging have a total acquisition time on the order of 10 minutes for a single scan, with the detector read-out time often a major contributor to acquisition length. Reduction of the portion of the scan time spent in read-out can be achieved through short-scan acquisition. Knowledge of and correction for geometric misalignments is another crucial factor in obtaining high quality microCT images. In this work, we have implemented a short-scan Feldkamp algorithm with correction geometric misalignment. Due to our system misalignments, severe ghosting artifacts are present in the reconstruction. We have implemented a reconstruction algorithm with correction for the misalignments which eliminates the ghosting artifacts. Comparisons of full-scan and short-scan reconstructions of both phantom and mouse data show similar image quality. We have also compared short-scan reconstructions to full-scan reconstructions from projection data with roughly the same total acquisition time. In this case, blurring is visible in sagittal slices of the full-scan reconstructions that is not present in the short-scan reconstructions. Short-scan acquisition provides reduction of the total acquisition time resulting in microCT images without the loss in image quality obtained by simply reducing the number of projections for a full-scan acquisition. Axis of rotation horizontal transversal off-center shift and the X-ray source horizontal transversal shift are the most sensitive parameters.","PeriodicalId":186175,"journal":{"name":"2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515)","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128143696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-12-01DOI: 10.1109/NSSMIC.2003.1352033
R. Hughes, M. Kasten, B. Kilminster, K. Lannon, S. Levine, K. Pitts, G. Veramendi, B. Winer
The CDF Detector at the Tevatron currently uses an online track trigger, known as the XFT, to identify charged tracks with P/sub T/ > 1.5 GeV/c which are then utilized in a number of ways to produce an event-by-event trigger decision. The tracks found by the XFT are utilized in approximately 80 percent of the physics triggers, including identification of high energy leptons (e, /spl mu/, /spl tau/), events containing heavy, flavor (c, b, t) and events with interesting topologies in for searches for new phenomena. The XFT is functioning well in the current system. As the Tevatron luminosity grows, occupancy in the tracking chamber increases from multiple proton-antiproton interactions. In the trigger, this additional occupancy will cause the tracking resolution to degrade and the rate of fake tracks to grow. We propose to upgrade the existing system to mitigate these effects and allow the CDF detector to operate at its fullest capacity at the highest possible luminosity.
{"title":"Upgrade of the XFT trigger for CDF","authors":"R. Hughes, M. Kasten, B. Kilminster, K. Lannon, S. Levine, K. Pitts, G. Veramendi, B. Winer","doi":"10.1109/NSSMIC.2003.1352033","DOIUrl":"https://doi.org/10.1109/NSSMIC.2003.1352033","url":null,"abstract":"The CDF Detector at the Tevatron currently uses an online track trigger, known as the XFT, to identify charged tracks with P/sub T/ > 1.5 GeV/c which are then utilized in a number of ways to produce an event-by-event trigger decision. The tracks found by the XFT are utilized in approximately 80 percent of the physics triggers, including identification of high energy leptons (e, /spl mu/, /spl tau/), events containing heavy, flavor (c, b, t) and events with interesting topologies in for searches for new phenomena. The XFT is functioning well in the current system. As the Tevatron luminosity grows, occupancy in the tracking chamber increases from multiple proton-antiproton interactions. In the trigger, this additional occupancy will cause the tracking resolution to degrade and the rate of fake tracks to grow. We propose to upgrade the existing system to mitigate these effects and allow the CDF detector to operate at its fullest capacity at the highest possible luminosity.","PeriodicalId":186175,"journal":{"name":"2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515)","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115086090","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-12-01DOI: 10.1109/NSSMIC.2003.1352589
Xiaochuan Pan, Lifeng Yu, C. Kao, C. Pelizzari
We propose a new strategy to improve sampling density and image resolution in micro-CT without changing hardware and without sacrificing the size of the allowable maximum field of view (FOV). Such a strategy is achieved by use of the asymmetric scanning configurations in which the center of rotation is moved to an off-center position and a reconstruction algorithm specifically developed for such configurations. We conducted numerical studies to validate and evaluate the proposed strategy, and quantitative results in these studies confirm that the proposed configurations and algorithm can significantly improve spatial resolution properties in micro-CT.
{"title":"Spatial-resolution enhancement in micro-CT","authors":"Xiaochuan Pan, Lifeng Yu, C. Kao, C. Pelizzari","doi":"10.1109/NSSMIC.2003.1352589","DOIUrl":"https://doi.org/10.1109/NSSMIC.2003.1352589","url":null,"abstract":"We propose a new strategy to improve sampling density and image resolution in micro-CT without changing hardware and without sacrificing the size of the allowable maximum field of view (FOV). Such a strategy is achieved by use of the asymmetric scanning configurations in which the center of rotation is moved to an off-center position and a reconstruction algorithm specifically developed for such configurations. We conducted numerical studies to validate and evaluate the proposed strategy, and quantitative results in these studies confirm that the proposed configurations and algorithm can significantly improve spatial resolution properties in micro-CT.","PeriodicalId":186175,"journal":{"name":"2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515)","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125951211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-12-01DOI: 10.1109/NSSMIC.2003.1352419
H. Baghaei, W. Wong, J. Uribe, H. Li, Y. Wang, Y. Liu, T. Xing, R. Ramirez, S. Xie, S. Kim
We compared two fully three-dimensional (3-D) image reconstruction algorithms and two 3-D rebinning algorithms followed by reconstruction with a two-dimensional (2-D) filtered backprojection algorithm. The two 3-D image reconstruction algorithms were ordered subsets expectation maximization (3D-OSEM) and 3-D reprojection (3DRP). The two rebinning algorithms were Fourier rebinning (FORE) and single slice rebinning (SSRB). The 3-D projection data used for this work were acquired with a high-resolution PET scanner (MDAPET) with an intrinsic transaxial resolution of 2.8 mm. The scanner has 14 detector rings covering an axial field-of-view of 38.5 mm. We scanned three phantoms: (1) a uniform cylindrical phantom with inner diameter of 20.5 cm, (2) a 11.5-cm cylindrical phantom with four embedded small lesions with diameters of 3, 4, 5, and 6 mm, and (3) the 3-D Hoffman brain phantom with three embedded small lesion phantoms with diameters of 3, 5, and 8.6 mm. We evaluated the different reconstruction methods by comparing the noise variance of images, contrast recovery and contrast-noise trade-off, lesion detectability, and by visually inspecting images. We found that overall the 3D-OSEM algorithm followed by post filtering produced the best results. Even though the MDAPET camera has a relatively small maximum axial acceptance (/spl plusmn/5 deg), the 3DRP algorithm produced slightly better images compared to the faster 2-D rebinning methods.
我们比较了两种全三维(3-D)图像重建算法和两种3-D重建算法，然后用二维(2-D)滤波后的反向投影算法进行重建。三维图像重建算法分别为有序子集期望最大化算法(3D-OSEM)和三维重投影算法(3DRP)。两种重构算法分别是傅里叶重构(FORE)和单片重构(SSRB)。这项工作使用的三维投影数据是通过高分辨率PET扫描仪(MDAPET)获得的，其固有的跨轴分辨率为2.8 mm。该扫描仪有14个探测器环，覆盖38.5毫米的轴向视野。我们扫描了三个幻象:(1)内径为20.5 cm的均匀圆柱形幻象，(2)直径为3、4、5和6 mm的直径为4个内嵌小病灶的11.5 cm圆柱形幻象，以及(3)直径为3、5和8.6 mm的3个内嵌小病灶的3- d Hoffman脑幻象。我们通过比较图像的噪声方差、对比度恢复和对比度-噪声权衡、损伤可检测性以及视觉检查图像来评估不同的重建方法。我们发现，总体而言，3D-OSEM算法之后的后滤波产生了最好的结果。尽管MDAPET相机具有相对较小的最大轴向接受度(/spl + /5度)，但与更快的二维重建方法相比，3DRP算法产生的图像略好一些。
{"title":"A comparison of four image reconstruction algorithms for detection of small lesions in brain phantom","authors":"H. Baghaei, W. Wong, J. Uribe, H. Li, Y. Wang, Y. Liu, T. Xing, R. Ramirez, S. Xie, S. Kim","doi":"10.1109/NSSMIC.2003.1352419","DOIUrl":"https://doi.org/10.1109/NSSMIC.2003.1352419","url":null,"abstract":"We compared two fully three-dimensional (3-D) image reconstruction algorithms and two 3-D rebinning algorithms followed by reconstruction with a two-dimensional (2-D) filtered backprojection algorithm. The two 3-D image reconstruction algorithms were ordered subsets expectation maximization (3D-OSEM) and 3-D reprojection (3DRP). The two rebinning algorithms were Fourier rebinning (FORE) and single slice rebinning (SSRB). The 3-D projection data used for this work were acquired with a high-resolution PET scanner (MDAPET) with an intrinsic transaxial resolution of 2.8 mm. The scanner has 14 detector rings covering an axial field-of-view of 38.5 mm. We scanned three phantoms: (1) a uniform cylindrical phantom with inner diameter of 20.5 cm, (2) a 11.5-cm cylindrical phantom with four embedded small lesions with diameters of 3, 4, 5, and 6 mm, and (3) the 3-D Hoffman brain phantom with three embedded small lesion phantoms with diameters of 3, 5, and 8.6 mm. We evaluated the different reconstruction methods by comparing the noise variance of images, contrast recovery and contrast-noise trade-off, lesion detectability, and by visually inspecting images. We found that overall the 3D-OSEM algorithm followed by post filtering produced the best results. Even though the MDAPET camera has a relatively small maximum axial acceptance (/spl plusmn/5 deg), the 3DRP algorithm produced slightly better images compared to the faster 2-D rebinning methods.","PeriodicalId":186175,"journal":{"name":"2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129227188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-12-01DOI: 10.1109/NSSMIC.2003.1352350
H. Li, Y. Liu, T. Xing, Wang Y, S. Xie, J. Uribe, H. Baghaei, R. Ramirez, S. Kim, W. Wong
We designed and implemented electronics for a low-cost high-sensitivity positron emission tomography camera for research involving rodents. To reduce cost and increase sensitivity, we used continuous full-ring photomultiplier tube (PMT) with quadrant sharing (PQS) detector design. In this prototype camera, 168 PMTs decode 144 scintillation detector blocks consisting of 9216 crystal elements. An Anger position matrix board weight sums the 144 detector blocks as eight individual gamma camera zones. The full-ring detector decoding is performed by eight fixed local zones. However, in the PMT-quadrant-sharing design, every two adjacent zones share seven axial PMTs. A boundary processing technique has been developed for the PMT-quadrant-sharing detector blocks so that the decoding of the full-ring detector can be performed by individual zones. A high-yield-pileup-event-recovery decoding board, a module-based coincidence processing system and a data acquisition computer, which were originally developed for a whole-body PET, can still be used by this rodent PET camera. The camera needs only eight decoding boards, and each board decodes 18 detector blocks of one detector zone. The entire decoding electronics need only 24 ADCs and can handle about six million events/second of single-rate. A motherboard decodes the control commands from the data acquisition computer, performs the real-time boundary processing and distributes DC power signals to all the eight decoding boards. To further reduce the cost and size of the camera, we have developed a new compact PMT voltage divider with adjustable PMT gain that can be controlled by programming the dynode high voltages directly. The very front-end preamplifier is also integrated into this divider board to increase the signal-to-noise ratio. A new instantaneous light-emitting diode automatic PMT gain calibration method is also used in this camera for better quality control; the gains of 168 PMTs can be equalized within 1 minute.
{"title":"Electronics design for a low-cost high-sensitivity rodent-research PET (RRPET)","authors":"H. Li, Y. Liu, T. Xing, Wang Y, S. Xie, J. Uribe, H. Baghaei, R. Ramirez, S. Kim, W. Wong","doi":"10.1109/NSSMIC.2003.1352350","DOIUrl":"https://doi.org/10.1109/NSSMIC.2003.1352350","url":null,"abstract":"We designed and implemented electronics for a low-cost high-sensitivity positron emission tomography camera for research involving rodents. To reduce cost and increase sensitivity, we used continuous full-ring photomultiplier tube (PMT) with quadrant sharing (PQS) detector design. In this prototype camera, 168 PMTs decode 144 scintillation detector blocks consisting of 9216 crystal elements. An Anger position matrix board weight sums the 144 detector blocks as eight individual gamma camera zones. The full-ring detector decoding is performed by eight fixed local zones. However, in the PMT-quadrant-sharing design, every two adjacent zones share seven axial PMTs. A boundary processing technique has been developed for the PMT-quadrant-sharing detector blocks so that the decoding of the full-ring detector can be performed by individual zones. A high-yield-pileup-event-recovery decoding board, a module-based coincidence processing system and a data acquisition computer, which were originally developed for a whole-body PET, can still be used by this rodent PET camera. The camera needs only eight decoding boards, and each board decodes 18 detector blocks of one detector zone. The entire decoding electronics need only 24 ADCs and can handle about six million events/second of single-rate. A motherboard decodes the control commands from the data acquisition computer, performs the real-time boundary processing and distributes DC power signals to all the eight decoding boards. To further reduce the cost and size of the camera, we have developed a new compact PMT voltage divider with adjustable PMT gain that can be controlled by programming the dynode high voltages directly. The very front-end preamplifier is also integrated into this divider board to increase the signal-to-noise ratio. A new instantaneous light-emitting diode automatic PMT gain calibration method is also used in this camera for better quality control; the gains of 168 PMTs can be equalized within 1 minute.","PeriodicalId":186175,"journal":{"name":"2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131350444","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-12-01DOI: 10.1109/NSSMIC.2003.1352017
Y. Asaoka
We propose a new air fluorescence and Cerenkov detector Ashra. The Ashra phase-1 detector consists of 1+1/3 observational stations installed at the distance of 30-40 km in a mountain site. It ensures the large target mass for neutrinos and low-energy threshold for TeV gamma rays. The observational station is composed of 12 wide-angle high-precision telescope, which can cover completely all-sky view. Each telescope has a field-of-view of 50 deg. x 50 deg. and spot size resolution of 1 arcmin. To realize the Ashra telescope concept, we newly apply the following techniques matured in the other fields: i) Baker-Nunn optics optimized to keep better than 1 arcmin resolution in 50 deg. field of view, ii) electrostatic lens image intensifier tube with the resolution matched with that of the above optics, iii) photoelectric image pipeline with self triggering capability using light splitting after sufficient amplification, and iv) CMOS image sensor which read triggered images out of the above IIT. These novel techniques allow us an excellent opportunity for simultaneous observation of air fluorescence and Cerenkov lights with 1 arcmin resolution in entirely all sky. This will open a new field, "Observational Particle Astrophysics" by continuously observing TeV gamma-rays, VHE-neutrinos. Knee-CRs, and UHECRs.
{"title":"All-sky survey high resolution air-shower detector (Ashra)","authors":"Y. Asaoka","doi":"10.1109/NSSMIC.2003.1352017","DOIUrl":"https://doi.org/10.1109/NSSMIC.2003.1352017","url":null,"abstract":"We propose a new air fluorescence and Cerenkov detector Ashra. The Ashra phase-1 detector consists of 1+1/3 observational stations installed at the distance of 30-40 km in a mountain site. It ensures the large target mass for neutrinos and low-energy threshold for TeV gamma rays. The observational station is composed of 12 wide-angle high-precision telescope, which can cover completely all-sky view. Each telescope has a field-of-view of 50 deg. x 50 deg. and spot size resolution of 1 arcmin. To realize the Ashra telescope concept, we newly apply the following techniques matured in the other fields: i) Baker-Nunn optics optimized to keep better than 1 arcmin resolution in 50 deg. field of view, ii) electrostatic lens image intensifier tube with the resolution matched with that of the above optics, iii) photoelectric image pipeline with self triggering capability using light splitting after sufficient amplification, and iv) CMOS image sensor which read triggered images out of the above IIT. These novel techniques allow us an excellent opportunity for simultaneous observation of air fluorescence and Cerenkov lights with 1 arcmin resolution in entirely all sky. This will open a new field, \"Observational Particle Astrophysics\" by continuously observing TeV gamma-rays, VHE-neutrinos. Knee-CRs, and UHECRs.","PeriodicalId":186175,"journal":{"name":"2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515)","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116504778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-12-01DOI: 10.1109/NSSMIC.2003.1352208
R. BIanford, P. Chen, T. Kamae, G. Madejski, J. Ng, T. Mizuno, H. Tajima, T. Thurston, L. Barbier, P. Bloser, T. Cline, S. Hunter, A. Harding, J. Krizmanic, J. Mitchell, R. Streitmatter, J. Tueller, E. Groth, R. Fernholz, D. Marlow, G. Bogaert, S. Gunji, H. Sakurai, Y. Saito, T. Takahashi, J. Kataoka, N. Kawai, Y. Fukazawa, P. Carlson, W. Klamra, M. Pearce, C. Bjornsson, C. Fransson, S. Larsson, F. Ryde
We are developing a new balloon-borne instrument (PoGO), to measure polarization of soft gamma rays (25-200 keV) using asymmetry in azimuth angle distribution of Compton scattering. PoGO will detect 10% polarization in 100mCrab sources in a 6-8 hour observation and bring a new dimension to studies on gamma ray emission/transportation mechanism in pulsars, AGNs, black hole binaries, and neutron star surface. The concept is an adaptation to polarization measurements of well-type phoswich counter technology used in balloon-borne experiments (Welcome-1) and AstroE2 Hard X-ray Detector. PoGO consists of close-packed array of 397 hexagonal well-type phoswich counters. Each unit is composed of a long thin tube (well) of slow plastic scintillator, a solid rod of fast plastic scintillator, and a short BGO at the base. A photomultiplier coupled to the end of the BGO detects light from all 3 scintillators. The rods with decay times < 10 ns, are used as the active elements; while the wells and BGOs, with decay times /spl sim/ 250 ns are used as active anti-coincidence. The fast and slow signals are separated out electronically. When gamma rays entering the field-of-view (fwhm /spl sim/3deg/sup 2/) strike a fast scintillator, some are Compton scattered. A fraction of the scattered photons are absorbed in another rod (or undergo a second scatter). A valid event requires one clean fast signal of pulse-height compatible with photo-absorption (> 20 keV) and one or more compatible with Compton scattering (< 10 keV). Studies based on EGS4 (with polarization features) and Geant4 predict excellent background rejection and high sensitivity.
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