Planarity certification of ATLAS Micromegas detector panels

Energy Technology Data Exchange (ETDEWEB)

Mueller, Ralph; Biebel, Otmar; Bortfeldt, Jonathan; Flierl, Bernhard; Hertenberger, Ralf; Loesel, Philipp; Herrmann, Maximilian [LMU Muenchen (Germany); Zibell, Andre [JMU Wuerzburg (Germany)

2016-07-01

During the second long LHC shutdown, 2019/20, the precision tracking detectors of the ATLAS muon spectrometer in the inner end caps will be replaced using Micromegas, a planar gas-detector technology. Modules of 2 m{sup 2} area are built in quadruplets from five precisely planar sandwich panels that define the anodes and the cathodes of the four active detector planes. A panel is composed of three consecutive layers FR4 - aluminum honeycomb - FR4. Single plane spatial particle resolution below 100 μm is achievable when the deviations from planarity of the strip-anodes do not exceed 80 μm RMS over the whole active area and the parallelism of the readout strips is within 30 μm. In order to measure the dimensional accuracy of each panel, laser distance sensors combined with a coordinate measurement system have been investigated. The sensor requirements to measure the planarity of the panels are a resolution of 0.3 μm and a beam spot diameter of ∼20 μm, well below 100 μ m the size of the smallest structures. We report on achieved planarities of the panels and the performance of the laser sensor system. A panel with an RMS better than 30 μm was build and the evolution of its planarity due to humidity and temperature effects is shown.

A combination-weighted Feldkamp-based reconstruction algorithm for cone-beam CT

International Nuclear Information System (INIS)

Mori, Shinichiro; Endo, Masahiro; Komatsu, Shuhei; Kandatsu, Susumu; Yashiro, Tomoyasu; Baba, Masayuki

2006-01-01

The combination-weighted Feldkamp algorithm (CW-FDK) was developed and tested in a phantom in order to reduce cone-beam artefacts and enhance cranio-caudal reconstruction coverage in an attempt to improve image quality when utilizing cone-beam computed tomography (CBCT). Using a 256-slice cone-beam CT (256CBCT), image quality (CT-number uniformity and geometrical accuracy) was quantitatively evaluated in phantom and clinical studies, and the results were compared to those obtained with the original Feldkamp algorithm. A clinical study was done in lung cancer patients under breath holding and free breathing. Image quality for the original Feldkamp algorithm is degraded at the edge of the scan region due to the missing volume, commensurate with the cranio-caudal distance between the reconstruction and central planes. The CW-FDK extended the reconstruction coverage to equal the scan coverage and improved reconstruction accuracy, unaffected by the cranio-caudal distance. The extended reconstruction coverage with good image quality provided by the CW-FDK will be clinically investigated for improving diagnostic and radiotherapy applications. In addition, this algorithm can also be adapted for use in relatively wide cone-angle CBCT such as with a flat-panel detector CBCT

A compact high resolution flat panel PET detector based on the new 4-side buttable MPPC for biomedical applications.

Science.gov (United States)

Wang, Qiang; Wen, Jie; Ravindranath, Bosky; O'Sullivan, Andrew W; Catherall, David; Li, Ke; Wei, Shouyi; Komarov, Sergey; Tai, Yuan-Chuan

2015-09-11

Compact high-resolution panel detectors using virtual pinhole (VP) PET geometry can be inserted into existing clinical or pre-clinical PET systems to improve regional spatial resolution and sensitivity. Here we describe a compact panel PET detector built using the new Though Silicon Via (TSV) multi-pixel photon counters (MPPC) detector. This insert provides high spatial resolution and good timing performance for multiple bio-medical applications. Because the TSV MPPC design eliminates wire bonding and has a package dimension which is very close to the MPPC's active area, it is 4-side buttable. The custom designed MPPC array (based on Hamamatsu S12641-PA-50(x)) used in the prototype is composed of 4 × 4 TSV-MPPC cells with a 4.46 mm pitch in both directions. The detector module has 16 × 16 lutetium yttrium oxyorthosilicate (LYSO) crystal array, with each crystal measuring 0.92 × 0.92 × 3 mm 3 with 1.0 mm pitch. The outer diameter of the detector block is 16.8 × 16.8 mm 2 . Thirty-two such blocks will be arranged in a 4 × 8 array with 1 mm gaps to form a panel detector with detection area around 7 cm × 14 cm in the full-size detector. The flood histogram acquired with Ge-68 source showed excellent crystal separation capability with all 256 crystals clearly resolved. The detector module's mean, standard deviation, minimum (best) and maximum (worst) energy resolution were 10.19%, +/-0.68%, 8.36% and 13.45% FWHM, respectively. The measured coincidence time resolution between the block detector and a fast reference detector (around 200 ps single photon timing resolution) was 0.95 ns. When tested with Siemens Cardinal electronics the performance of the detector blocks remain consistent. These results demonstrate that the TSV-MPPC is a promising photon sensor for use in a flat panel PET insert composed of many high resolution compact detector modules.

Present and future of flat panel detectors in the world

International Nuclear Information System (INIS)

Inamura, Kiyonari

2002-01-01

Present status of development of flat panel detectors and their clinical application in the world have been surveyed, and future trends are also explored especially in the field of material researches and methods of manufacturing. Also the importance of role of medical physicists on user side is described because characteristic physics measurement of a detector assembly is unavoidable and essential in quality assurance in clinical routine and acceptance test in hospitals. Even though physics measurements and clinical evaluations on flat panel detectors have shown remarkable progress and advances in these several years, future problems of cost down in manufacturing and quality assurance to prevent individual differences between detector assemblies must be resolved. Results of evaluation in mammography, chest radiography, fluoroscopy for cardiovascular examination, bone tumor examination and radiotherapy application indicate that flat panel detectors are future promising materials. Their systematic operation is contributing to heighten accuracy of image examinations and preciseness of radiation therapy. Encouragement to medical physicists relevant to flat panel detectors is also raised in this paper. (author)

A performance comparison of flat-panel imager-based MV and kV cone-beam CT

International Nuclear Information System (INIS)

Groh, B.A.; Siewerdsen, J.H.; Drake, D.G.; Wong, J.W.; Jaffray, D.A.

2002-01-01

The use of cone-beam computed tomography (CBCT) has been proposed for guiding the delivery of radiation therapy, and investigators have examined the use of both kilovoltage (kV) and megavoltage (MV) x-ray beams in the development of such CBCT systems. In this paper, the inherent contrast and signal-to-noise ratio (SNR) performance for a variety of existing and hypothetical detectors for CBCT are investigated analytically as a function of imaging dose and object size. Theoretical predictions are compared to the results of experimental investigations employing large-area flat-panel imagers (FPIs) at kV and MV energies. Measurements were performed on two different FPI-based CBCT systems: a bench-top prototype incorporating an FPI and kV x-ray source (100 kVp x rays), and a system incorporating an FPI mounted on the gantry of a medical linear accelerator (6 MV x rays). The SNR in volume reconstructions was measured as a function of dose and found to agree reasonably with theoretical predictions. These results confirm the theoretically predicted advantages of employing kV energy x rays in imaging soft-tissue structures found in the human body. While MV CBCT may provide a valuable means of correcting 3D setup errors and may offer an advantage in terms of simplicity of mechanical integration with a linear accelerator (e.g., implementation in place of a portal imager), kV CBCT offers significant performance advantages in terms of image contrast and SNR per unit dose for visualization of soft-tissue structures. The relatively poor SNR performance at MV energies is primarily a result of the low x-ray quantum efficiencies (∼a few percent or less) that are currently achieved with FPIs at high energies. Furthermore, kV CBCT with an FPI offers the potential of combined volumetric and radiographic/fluoroscopic imaging using the same device

Noise simulation in cone beam CT imaging with parallel computing

International Nuclear Information System (INIS)

Tu, S.-J.; Shaw, Chris C; Chen, Lingyun

2006-01-01

We developed a computer noise simulation model for cone beam computed tomography imaging using a general purpose PC cluster. This model uses a mono-energetic x-ray approximation and allows us to investigate three primary performance components, specifically quantum noise, detector blurring and additive system noise. A parallel random number generator based on the Weyl sequence was implemented in the noise simulation and a visualization technique was accordingly developed to validate the quality of the parallel random number generator. In our computer simulation model, three-dimensional (3D) phantoms were mathematically modelled and used to create 450 analytical projections, which were then sampled into digital image data. Quantum noise was simulated and added to the analytical projection image data, which were then filtered to incorporate flat panel detector blurring. Additive system noise was generated and added to form the final projection images. The Feldkamp algorithm was implemented and used to reconstruct the 3D images of the phantoms. A 24 dual-Xeon PC cluster was used to compute the projections and reconstructed images in parallel with each CPU processing 10 projection views for a total of 450 views. Based on this computer simulation system, simulated cone beam CT images were generated for various phantoms and technique settings. Noise power spectra for the flat panel x-ray detector and reconstructed images were then computed to characterize the noise properties. As an example among the potential applications of our noise simulation model, we showed that images of low contrast objects can be produced and used for image quality evaluation

Performance evaluation of flat panel detector in x-ray fluoroscopy

International Nuclear Information System (INIS)

Grewal, R.K.; Mclean, I.D.

2004-01-01

Full text: Flat panel detectors are currently replacing the conventional image intensifiers in R-F imaging. We evaluated the performance of a biplane cardiac imaging system (Siemens Axiom Artis dBC), the image acquisition was based on a 25 cm diagonal digital fiat panel detector. Performance characteristics included image quality, typical patient entrance dose and measurement of input to the surface of flat detector. The results were compared with conventional image intensifier systems (Siemens Hicor Unit and Toshiba DPF 2000 A Biplane Unit) used in cardiac imaging at Westmead. Image quality and dose measurements were performed following standard protocols using Westmead test object and 20 cm solid water as absorber in the beam. For measurement of input to the surface of flat detector, 2 mm copper was placed on the collimator. Radcal 3cc and 180 cc ion chambers were used for dose measurements. Image quality: Our measurements on flat panel system indicate that high contrast resolution and threshold contrast is not affected by changing field size. This is expected due to minimum loss of signal in the imaging chain of digital systems and the independence of detector pixel size with change in field of view. While low contrast resolution was found to be similar to conventional systems, high contrast resolution was significantly superior using flat detector system for large and intermediate field of view (25-28 1p/cm against 18-20). Typical patient dose as measured using flat detector system was similar to the conventional Toshiba pulsed fluoroscopy system( ∼ 3 - 8 mGy/min depending on the field size). This was 40-50 % lower than our old Siemens hicore unit. Input to the surface of flat detector was found to vary with field size as is the case with a conventional II system. As described elsewhere, although there is no necessity to increase exposure or video gain in a digital magnification, digital data interpolation process introduces noise. As a result system

Handling data redundancy in helical cone beam reconstruction with a cone-angle-based window function and its asymptotic approximation

International Nuclear Information System (INIS)

Tang Xiangyang; Hsieh Jiang

2007-01-01

A cone-angle-based window function is defined in this manuscript for image reconstruction using helical cone beam filtered backprojection (CB-FBP) algorithms. Rather than defining the window boundaries in a two-dimensional detector acquiring projection data for computed tomographic imaging, the cone-angle-based window function deals with data redundancy by selecting rays with the smallest cone angle relative to the reconstruction plane. To be computationally efficient, an asymptotic approximation of the cone-angle-based window function is also given and analyzed in this paper. The benefit of using such an asymptotic approximation also includes the avoidance of functional discontinuities that cause artifacts in reconstructed tomographic images. The cone-angle-based window function and its asymptotic approximation provide a way, equivalent to the Tam-Danielsson-window, for helical CB-FBP reconstruction algorithms to deal with data redundancy, regardless of where the helical pitch is constant or dynamically variable during a scan. By taking the cone-parallel geometry as an example, a computer simulation study is conducted to evaluate the proposed window function and its asymptotic approximation for helical CB-FBP reconstruction algorithm to handle data redundancy. The computer simulated Forbild head and thorax phantoms are utilized in the performance evaluation, showing that the proposed cone-angle-based window function and its asymptotic approximation can deal with data redundancy very well in cone beam image reconstruction from projection data acquired along helical source trajectories. Moreover, a numerical study carried out in this paper reveals that the proposed cone-angle-based window function is actually equivalent to the Tam-Danielsson-window, and rigorous mathematical proofs are being investigated

Plasma Panel Detectors for MIP Detection for the SLHC and a Test Chamber Design

CERN Document Server

Ball, Robert; Etzion, Erez; Friedman, Peter S; Levin, Daniel S; Moshe, Meny Ben; Weaverdyck, Curtis; Zhou, Bing

2010-01-01

Performance demands for high and super-high luminosity at the LHC (up to 10^35 cm^(-2) sec^(-1) after the 2017 shutdown) and at future colliders demand high resolution tracking detectors with very fast time response and excellent temporal and spatial resolution. We are investigating a new radiation detector technology based on Plasma Display Panels (PDP), the underlying engine of panel plasma television displays. The design and production of PDPs is supported by four decades of industrial development. Emerging from this television technology is the Plasma Panel Sensor (PPS), a novel variant of the micropattern radiation detector. The PPS is fundamentally an array of micro-Geiger plasma discharge cells operating in a non-ageing, hermetically sealed gas mixture . We report on the PPS development program, including design of a PPS Test Cell.

Cone calorimeter testing of foam core sandwich panels treated with intumescent paper underneath the veneer (FRV)

Science.gov (United States)

Mark A. Dietenberger; Ali Shalbafan; Johannes Welling

2017-01-01

Surfaces of novel foam core sandwich panels were adhered with intumescent fire‐retardant paper underneath the veneers (FRV) to improve their flammability properties. The panels were evaluated by means of cone calorimeter test (ASTM E 1354). Variables tested were different surface layer treatments, adhesives used for veneering, surface layer thicknesses, and processing...

Clinical introduction of image lag correction for a cone beam CT system

NARCIS (Netherlands)

Stankovic, Uros; Ploeger, Lennert S.; Sonke, Jan-Jakob; van Herk, Marcel

2016-01-01

Image lag in the flat-panel detector used for Linac integrated cone beam computed tomography (CBCT) has a degrading effect on CBCT image quality. The most prominent visible artifact is the presence of bright semicircular structure in the transverse view of the scans, known also as radar artifact.

Portable low-cost flat panel detectors for real-time digital radiography

International Nuclear Information System (INIS)

Iovea, Mihai; Neagu, Marian; Stefanescu, Bogdan; Mateiasi, Gabriela; Porosnicu, Ioana; Angheluta, Elena

2015-01-01

The X-ray inspection is one of the most common used non-destructive testing methods in industry applications, but for the portable X-ray digital solution are not so many accessible, low-cost and versatile detection devices. The efficiency of a non-destructive X-ray portable device is represented by the quality of digital images, by its low acquisition time combined with a high resolution, in condition of low noise and at an affordable cost. The paper presents two X-ray portable imaging systems developed by us, suitable also for aerospace NDT applications, which are also very versatile for being easily adapted for other fields that requires mobile solutions. The first device described in the paper represent a portable large-size (210 mm X 550 mm) and high-resolution (27/54 microns) flat panel detector based on linear translation of a X-Ray TDI detector, destined for various components/parts real-time transmission measurements. The second system it is also a flat panel detectors, with a size of 510 mm X 610 mm, with the detector size from 0.2 mm until 1.5 mm, which can operate by applying the dual-energy method, very useful for discriminating materials by evaluating their Atomic effective number. The high resolution and low-cost of this flat-panels widens their applicability by covering large requirements, from identifying unwanted materials within a structure until detection of very thin cracks in complex components.

Portable low-cost flat panel detectors for real-time digital radiography

Energy Technology Data Exchange (ETDEWEB)

Iovea, Mihai; Neagu, Marian; Stefanescu, Bogdan; Mateiasi, Gabriela; Porosnicu, Ioana; Angheluta, Elena [Accent Pro 2000 S.R.L., Bucharest (Romania)

2015-07-01

The X-ray inspection is one of the most common used non-destructive testing methods in industry applications, but for the portable X-ray digital solution are not so many accessible, low-cost and versatile detection devices. The efficiency of a non-destructive X-ray portable device is represented by the quality of digital images, by its low acquisition time combined with a high resolution, in condition of low noise and at an affordable cost. The paper presents two X-ray portable imaging systems developed by us, suitable also for aerospace NDT applications, which are also very versatile for being easily adapted for other fields that requires mobile solutions. The first device described in the paper represent a portable large-size (210 mm X 550 mm) and high-resolution (27/54 microns) flat panel detector based on linear translation of a X-Ray TDI detector, destined for various components/parts real-time transmission measurements. The second system it is also a flat panel detectors, with a size of 510 mm X 610 mm, with the detector size from 0.2 mm until 1.5 mm, which can operate by applying the dual-energy method, very useful for discriminating materials by evaluating their Atomic effective number. The high resolution and low-cost of this flat-panels widens their applicability by covering large requirements, from identifying unwanted materials within a structure until detection of very thin cracks in complex components.

Reconstruction of Spectra Using X-ray Flat Panel Detector; Reconstruccion de Espectros de Rayos X Utilizando un Detector Flat Panel

Energy Technology Data Exchange (ETDEWEB)

Gallardo, S.; Querol, A.; Pozuelo, F.; Juste, B.; Rodenas, J.; Verdu, G.

2013-07-01

In this work, we used a flat panel detector with a wedge of PMMA for absorbed dose curve for given working conditions of X-ray tube The relationship between absorbed dose curve recorded by the flat panel and primary X-ray spectrum is defined by a response function that can be obtained using the Monte Carlo method, namely the MCNP5 code. However there are some problems that affect the applicability of this method such as: flat panel characteristics and the characteristics of the physical process (ill-conditioned problem). Both aspects are discussed in this paper.

Gold-coated copper cone detector as a new standard detector for F2 laser radiation at 157 nm

International Nuclear Information System (INIS)

Kueck, Stefan; Brandt, Friedhelm; Taddeo, Mario

2005-01-01

A new standard detector for high-accuracy measurements of F2 laser radiation at 157 nm is presented. This gold-coated copper cone detector permits the measurement of average powers up to 2 W with an uncertainty of ∼1%. To the best of our knowledge, this is the first highly accurate standard detector for F2 laser radiation for this power level. It is fully characterized according to Guide to the Expression of Uncertainty in Measurement of the International Organization for Standardization and is connected to the calibration chain for laser radiation established by the German National Metrology Institute

A new cone-beam X-ray CT system with a reduced size planar detector

International Nuclear Information System (INIS)

Li Liang; Chen Zhiqiang; Zhang Li; Xing Yuxiang; Kang Kejun

2006-01-01

In a traditional cone-beam CT system, the cost of product and computation is very high. The authors propose a transversely truncated cone-beam X-ray CT system with a reduced size detector positioned off-center, in which X-ray beams only cover half of the object. The reduced detector size cuts the cost and the X-ray dose of the CT system. The existing CT reconstruction algorithms are not directly applicable in this new CT system. Hence, the authors develop a BPF-type direct backprojection algorithm. Different from the traditional rebinding methods, our algorithm directly backprojects the pretreated projection data without rebinding. This makes the algorithm compact and computationally more efficient. Finally, some numerical simulations and practical experiments are done to validate the proposed algorithm. (authors)

Development of a Two-Dimensional Tracker with Plasma Panel Detector

CERN Document Server

AUTHOR|(CDS)2233132

Plasma panel sensors are micropattern gaseous radiation detectors which are based on the technology of plasma display panels. This thesis summarizes the research that had been done on commercially available plasma display panels that were converted to plasma panel sensor prototypes and describes the construction of a two-dimensional tracker consisting of four of those prototypes, with one-dimensional readout on each, used to detect tracks of cosmic muons. A large amount of 2-point as well as 3 and 4-point tracks were detected. Qualitative analyses as well as Pearson’s χ2 tests are performed on the track angular distribution and on a histogram of the linearity measure of 3-point tracks to reject the hypothesis that these tracks result from completely random panel hits. Some RF noise effects contributing to false positives are ruled out, while it is shown that other effects can be ruled out only with a high-intensity minimum ionizing particle source. A significant part of the tracker construction was the dev...

Preliminary performance of image quality for a low-dose C-arm CT system with a flat-panel detector

Energy Technology Data Exchange (ETDEWEB)

Kyung Cha, Bo [Advanced Medical Device Research Center, Korea Electrotechnology Research Institute, Ansan (Korea, Republic of); Seo, Chang-Woo [Department of Radiation Convergence Engineering, College of Health Science, Yonsei University, Wonju (Korea, Republic of); Yang, Keedong [Advanced Medical Device Research Center, Korea Electrotechnology Research Institute, Ansan (Korea, Republic of); Jeon, Seongchae, E-mail: sarim@keri.re.kr [Advanced Medical Device Research Center, Korea Electrotechnology Research Institute, Ansan (Korea, Republic of); Huh, Young [Advanced Medical Device Research Center, Korea Electrotechnology Research Institute, Ansan (Korea, Republic of)

2015-06-01

Digital flat panel imager (FPI)-based cone-beam computed tomography (CBCT) has been widely used in C-arm imaging for spine surgery and interventional procedures. The system provides real-time fluoroscopy with high spatial resolution and three-dimensional (3D) visualization of anatomical structure without the need for patient transportation in interventional suite. In this work, a prototype CBCT imaging platform with continuous single rotation about the gantry was developed by using a large-area flat-panel detector with amorphous Si-based thin film transistor matrix. The different 2D projection images were acquired during constant gantry velocity for reconstructed images at a tube voltage of 80–120 kVp, and different current (10–50 mA) conditions. Various scan protocols were applied to a chest phantom human by changing the number of projection images and scanning angles. The projections were then reconstructed into a volumetric data of sections by using a 3D reconstruction algorithm (e.g., filtered back projection). The preliminary quantitative X-ray performance of our CBCT system was investigated by using the American Association of Physicists in Medicine CT phantom in terms of spatial resolution, contrast resolution, and CT number linearity for mobile or fixed C-arm based CBCT application with limited rotational geometry. The novel results of the projection data with different scanning angles and angular increments in the orbital gantry platform were acquired and evaluated experimentally.

Preliminary performance of image quality for a low-dose C-arm CT system with a flat-panel detector

International Nuclear Information System (INIS)

Kyung Cha, Bo; Seo, Chang-Woo; Yang, Keedong; Jeon, Seongchae; Huh, Young

2015-01-01

Digital flat panel imager (FPI)-based cone-beam computed tomography (CBCT) has been widely used in C-arm imaging for spine surgery and interventional procedures. The system provides real-time fluoroscopy with high spatial resolution and three-dimensional (3D) visualization of anatomical structure without the need for patient transportation in interventional suite. In this work, a prototype CBCT imaging platform with continuous single rotation about the gantry was developed by using a large-area flat-panel detector with amorphous Si-based thin film transistor matrix. The different 2D projection images were acquired during constant gantry velocity for reconstructed images at a tube voltage of 80–120 kVp, and different current (10–50 mA) conditions. Various scan protocols were applied to a chest phantom human by changing the number of projection images and scanning angles. The projections were then reconstructed into a volumetric data of sections by using a 3D reconstruction algorithm (e.g., filtered back projection). The preliminary quantitative X-ray performance of our CBCT system was investigated by using the American Association of Physicists in Medicine CT phantom in terms of spatial resolution, contrast resolution, and CT number linearity for mobile or fixed C-arm based CBCT application with limited rotational geometry. The novel results of the projection data with different scanning angles and angular increments in the orbital gantry platform were acquired and evaluated experimentally

Evaluation of patient dose using a virtual CT scanner: Applications to 4DCT simulation and Kilovoltage cone-beam imaging

International Nuclear Information System (INIS)

DeMarco, J J; Agazaryan, N; McNitt-Gray, M F; Cagnon, C H; Angel, E; Zankl, M

2008-01-01

This work evaluates the effects of patient size on radiation dose from simulation imaging studies such as four-dimensional computed tomography (4DCT) and kilovoltage cone-beam computed tomography (kV-CBCT). 4DCT studies are scans that include temporal information, frequently incorporating highly over-sampled imaging series necessary for retrospective sorting as a function of respiratory phase. This type of imaging study can result in a significant dose increase to the patient due to the slower table speed as compared with a conventional axial or helical scan protocol. Kilovoltage cone-beam imaging is a relatively new imaging technique that requires an on-board kilovoltage x-ray tube and a flat-panel detector. Instead of porting individual reference fields, the kV tube and flat-panel detector are rotated about the patient producing a cone-beam CT data set (kV-CBCT). To perform these investigations, we used Monte Carlo simulation methods with detailed models of adult patients and virtual source models of multidetector computed tomography (MDCT) scanners. The GSF family of three-dimensional, voxelized patient models, were implemented as input files using the Monte Carlo code MCNPX. The adult patient models represent a range of patient sizes and have all radiosensitive organs previously identified and segmented. Simulated 4DCT scans of each voxelized patient model were performed using a multi-detector CT source model that includes scanner specific spectra, bow-tie filtration, and helical source path. Standard MCNPX tally functions were applied to each model to estimate absolute organ dose based upon an air-kerma normalization measurement for nominal scanner operating parameters

Scatter measurement and correction method for cone-beam CT based on single grating scan

Science.gov (United States)

Huang, Kuidong; Shi, Wenlong; Wang, Xinyu; Dong, Yin; Chang, Taoqi; Zhang, Hua; Zhang, Dinghua

2017-06-01

In cone-beam computed tomography (CBCT) systems based on flat-panel detector imaging, the presence of scatter significantly reduces the quality of slices. Based on the concept of collimation, this paper presents a scatter measurement and correction method based on single grating scan. First, according to the characteristics of CBCT imaging, the scan method using single grating and the design requirements of the grating are analyzed and figured out. Second, by analyzing the composition of object projection images and object-and-grating projection images, the processing method for the scatter image at single projection angle is proposed. In addition, to avoid additional scan, this paper proposes an angle interpolation method of scatter images to reduce scan cost. Finally, the experimental results show that the scatter images obtained by this method are accurate and reliable, and the effect of scatter correction is obvious. When the additional object-and-grating projection images are collected and interpolated at intervals of 30 deg, the scatter correction error of slices can still be controlled within 3%.

Dosimetry of cone-defined stereotactic radiosurgery fields with a commercial synthetic diamond detector.

Science.gov (United States)

Morales, Johnny E; Crowe, Scott B; Hill, Robin; Freeman, Nigel; Trapp, J V

2014-11-01

Small field x-ray beam dosimetry is difficult due to lack of lateral electronic equilibrium, source occlusion, high dose gradients, and detector volume averaging. Currently, there is no single definitive detector recommended for small field dosimetry. The objective of this work was to evaluate the performance of a new commercial synthetic diamond detector, namely, the PTW 60019 microDiamond, for the dosimetry of small x-ray fields as used in stereotactic radiosurgery (SRS). Small field sizes were defined by BrainLAB circular cones (4-30 mm diameter) on a Novalis Trilogy linear accelerator and using the 6 MV SRS x-ray beam mode for all measurements. Percentage depth doses (PDDs) were measured and compared to an IBA SFD and a PTW 60012 E diode. Cross profiles were measured and compared to an IBA SFD diode. Field factors, ΩQclin,Qmsr (fclin,fmsr) , were calculated by Monte Carlo methods using BEAMnrc and correction factors, kQclin,Qmsr (fclin,fmsr) , were derived for the PTW 60019 microDiamond detector. For the small fields of 4-30 mm diameter, there were dose differences in the PDDs of up to 1.5% when compared to an IBA SFD and PTW 60012 E diode detector. For the cross profile measurements the penumbra values varied, depending upon the orientation of the detector. The field factors, ΩQclin,Qmsr (fclin,fmsr) , were calculated for these field diameters at a depth of 1.4 cm in water and they were within 2.7% of published values for a similar linear accelerator. The corrections factors, kQclin,Qmsr (fclin,fmsr) , were derived for the PTW 60019 microDiamond detector. The authors conclude that the new PTW 60019 microDiamond detector is generally suitable for relative dosimetry in small 6 MV SRS beams for a Novalis Trilogy linear equipped with circular cones.

Comparison of imaging properties of direct-type and indirect-type of flat-panel detector

International Nuclear Information System (INIS)

Matsumoto, Masao; Suekane, Koji; Ichimaru, Yasunobu; Ogata, Yuji; Inamura, Kiyonari; Kanai, Kouzou; Kanamori, Hitoshi

2002-01-01

A Flat-Panel Detector (FPD) has many advantages such as eliminating cassette handling and being able to display a preview image immediately in addition to the digital image processing and the networking. Thus, the FPD has ability to innovate the radiology department. We measured and evaluated the digital and over-all imaging properties (characteristic curves, modulation Transfer Functions, Wiener spectra and Noise Equivalent Quanta (NEQ) for the direct-type and indirect-type of FPD. The pre-sampling and overall NEQ of the indirect-type of FPD were better than the NEQ of the direct-type of FPD at lower spatial frequencies, but were worse at higher spatial frequencies. The FPD can take image data at real-time and be easy to digitalize. From these results, Screen/Film system and Computed Radiography system will be replaced by the FPD system, together with diffusion of CAD, cone beam Computed Tomography (CT) system and open-type Magnetic Resonance Imagining (MRI) system. (T. Tanaka)

Evaluation of a flat-panel detector system

International Nuclear Information System (INIS)

Sato, Masami; Eguchi, Yoichi; Yamada, Kinichi; Kaga, Yuji; Endo, Yutaka; Yamazaki, Tatsuya

2001-01-01

We evaluated the imaging performance of a flat-panel detector digital radiography system (CXDI-11 X-ray Digital Camera, Canon Inc.) and a computed radiography system (FCR9000C-HQ, Fuji Film). The characteristics of the two detectors and of the overall systems were compared. This included evaluation and comparison of the fundamental physical characteristics, including x-ray response curve, modulation transfer function (MTF), Wiener spectra, noise-equivalent quanta, and x-ray tube voltage-dependent detector response. Overall system performance was evaluated using receiver operating characteristic (ROC) analysis. The results of the study showed that the dynamic range of the CXDI-11 measured relative to the input x-ray flux was 10 3 , similar to that of the FCR9000C-HQ. Both systems showed similar final MTFs, although the pre-sampling MTF of the CXDI-11 was better than that of the FCR9000C-HQ. Noise analysis, based on noise-equivalent quanta and Wiener spectra, showed that for normal exposure conditions the CXDI-11 had superior performance. With both systems, x-ray response (system output/incident x-ray exposure) increased with increasing x-ray tube voltage. ROC analysis indicated that the CXDI-11 was superior in overall performance. (author)

Synchrotron applications of an amorphous silicon flat-panel detector

International Nuclear Information System (INIS)

Lee, J. H.; Can Aydiner, C.; Almer, J.; Bernier, J.; Chapman, K. W.; Chupas, P. J.; Haeffner, D.; Kump, K.; Lee, P. L.; Lienert, U.; Miceli, A.; Vera, G.; LANL; GE Healthcare

2008-01-01

A GE Revolution 41RT flat-panel detector (GE 41RT) from GE Healthcare (GE) has been in operation at the Advanced Photon Source for over two years. The detector has an active area of 41 cm x 41 cm with 200 (micro)m x 200 (micro)m pixel size. The nominal working photon energy is around 80 keV. The physical set-up and utility software of the detector system are discussed in this article. The linearity of the detector response was measured at 80.7 keV. The memory effect of the detector element, called lag, was also measured at different exposure times and gain settings. The modulation transfer function was measured in terms of the line-spread function using a 25 (micro)m x 1 cm tungsten slit. The background (dark) signal, the signal that the detector will carry without exposure to X-rays, was measured at three different gain settings and with exposure times of 1 ms to 15 s. The radial geometric flatness of the sensor panel was measured using the diffraction pattern from a CeO 2 powder standard. The large active area and fast data-capturing rate, i.e. 8 frames s -1 in radiography mode, 30 frames s -1 in fluoroscopy mode, make the GE 41RT one of a kind and very versatile in synchrotron diffraction. The loading behavior of a Cu/Nb multilayer material is used to demonstrate the use of the detector in a strain-stress experiment. Data from the measurement of various samples, amorphous SiO 2 in particular, are presented to show the detector effectiveness in pair distribution function measurements

Tracking brachytherapy sources using emission imaging with one flat panel detector

International Nuclear Information System (INIS)

Song Haijun; Bowsher, James; Das, Shiva; Yin Fangfang

2009-01-01

This work proposes to use the radiation from brachytherapy sources to track their dwell positions in three-dimensional (3D) space. The prototype device uses a single flat panel detector and a BB tray. The BBs are arranged in a defined pattern. The shadow of the BBs on the flat panel is analyzed to derive the 3D coordinates of the illumination source, i.e., the dwell position of the brachytherapy source. A kilovoltage x-ray source located 3.3 m away was used to align the center BB with the center pixel on the flat panel detector. For a test plan of 11 dwell positions, with an Ir-192 high dose rate unit, one projection was taken for each dwell point, and locations of the BB shadows were manually identified on the projection images. The 3D coordinates for the 11 dwell positions were reconstructed based on two BBs. The distances between dwell points were compared with the expected values. The average difference was 0.07 cm with a standard deviation of 0.15 cm. With automated BB shadow recognition in the future, this technique possesses the potential of tracking the 3D trajectory and the dwell times of a brachytherapy source in real time, enabling real time source position verification.

A semiempirical linear model of indirect, flat-panel x-ray detectors

Energy Technology Data Exchange (ETDEWEB)

Huang, Shih-Ying; Yang Kai; Abbey, Craig K.; Boone, John M. [Department of Biomedical Engineering, University of California, Davis, California, One Shields Avenue, Davis, California 95616 (United States) and Department of Radiology, University of California, Davis, Medical Center, 4860 Y Street, Ambulatory Care Center Suite 0505, Sacramento, California 95817 (United States); Department of Radiology, University of California, Davis, Medical Center, 4860 Y Street, Ambulatory Care Center Suite 0505, Sacramento, California 95817 (United States); Department of Psychological and Brain Sciences, University of California, Santa Barbara, California 92106 (United States); Department of Biomedical Engineering, University of California, Davis, California, One Shields Avenue, Davis, California 95616 (United States) and Department of Radiology, University of California, Davis, Medical Center, 4860 Y Street, Ambulatory Care Center Suite 3100, Sacramento, California 95817 (United States)

2012-04-15

Purpose: It is important to understand signal and noise transfer in the indirect, flat-panel x-ray detector when developing and optimizing imaging systems. For optimization where simulating images is necessary, this study introduces a semiempirical model to simulate projection images with user-defined x-ray fluence interaction. Methods: The signal and noise transfer in the indirect, flat-panel x-ray detectors is characterized by statistics consistent with energy-integration of x-ray photons. For an incident x-ray spectrum, x-ray photons are attenuated and absorbed in the x-ray scintillator to produce light photons, which are coupled to photodiodes for signal readout. The signal mean and variance are linearly related to the energy-integrated x-ray spectrum by empirically determined factors. With the known first- and second-order statistics, images can be simulated by incorporating multipixel signal statistics and the modulation transfer function of the imaging system. To estimate the semiempirical input to this model, 500 projection images (using an indirect, flat-panel x-ray detector in the breast CT system) were acquired with 50-100 kilovolt (kV) x-ray spectra filtered with 0.1-mm tin (Sn), 0.2-mm copper (Cu), 1.5-mm aluminum (Al), or 0.05-mm silver (Ag). The signal mean and variance of each detector element and the noise power spectra (NPS) were calculated and incorporated into this model for accuracy. Additionally, the modulation transfer function of the detector system was physically measured and incorporated in the image simulation steps. For validation purposes, simulated and measured projection images of air scans were compared using 40 kV/0.1-mm Sn, 65 kV/0.2-mm Cu, 85 kV/1.5-mm Al, and 95 kV/0.05-mm Ag. Results: The linear relationship between the measured signal statistics and the energy-integrated x-ray spectrum was confirmed and incorporated into the model. The signal mean and variance factors were linearly related to kV for each filter material (r

A semiempirical linear model of indirect, flat-panel x-ray detectors

International Nuclear Information System (INIS)

Huang, Shih-Ying; Yang Kai; Abbey, Craig K.; Boone, John M.

2012-01-01

Purpose: It is important to understand signal and noise transfer in the indirect, flat-panel x-ray detector when developing and optimizing imaging systems. For optimization where simulating images is necessary, this study introduces a semiempirical model to simulate projection images with user-defined x-ray fluence interaction. Methods: The signal and noise transfer in the indirect, flat-panel x-ray detectors is characterized by statistics consistent with energy-integration of x-ray photons. For an incident x-ray spectrum, x-ray photons are attenuated and absorbed in the x-ray scintillator to produce light photons, which are coupled to photodiodes for signal readout. The signal mean and variance are linearly related to the energy-integrated x-ray spectrum by empirically determined factors. With the known first- and second-order statistics, images can be simulated by incorporating multipixel signal statistics and the modulation transfer function of the imaging system. To estimate the semiempirical input to this model, 500 projection images (using an indirect, flat-panel x-ray detector in the breast CT system) were acquired with 50-100 kilovolt (kV) x-ray spectra filtered with 0.1-mm tin (Sn), 0.2-mm copper (Cu), 1.5-mm aluminum (Al), or 0.05-mm silver (Ag). The signal mean and variance of each detector element and the noise power spectra (NPS) were calculated and incorporated into this model for accuracy. Additionally, the modulation transfer function of the detector system was physically measured and incorporated in the image simulation steps. For validation purposes, simulated and measured projection images of air scans were compared using 40 kV/0.1-mm Sn, 65 kV/0.2-mm Cu, 85 kV/1.5-mm Al, and 95 kV/0.05-mm Ag. Results: The linear relationship between the measured signal statistics and the energy-integrated x-ray spectrum was confirmed and incorporated into the model. The signal mean and variance factors were linearly related to kV for each filter material (r 2 of

A semiempirical linear model of indirect, flat-panel x-ray detectors.

Science.gov (United States)

Huang, Shih-Ying; Yang, Kai; Abbey, Craig K; Boone, John M

2012-04-01

It is important to understand signal and noise transfer in the indirect, flat-panel x-ray detector when developing and optimizing imaging systems. For optimization where simulating images is necessary, this study introduces a semiempirical model to simulate projection images with user-defined x-ray fluence interaction. The signal and noise transfer in the indirect, flat-panel x-ray detectors is characterized by statistics consistent with energy-integration of x-ray photons. For an incident x-ray spectrum, x-ray photons are attenuated and absorbed in the x-ray scintillator to produce light photons, which are coupled to photodiodes for signal readout. The signal mean and variance are linearly related to the energy-integrated x-ray spectrum by empirically determined factors. With the known first- and second-order statistics, images can be simulated by incorporating multipixel signal statistics and the modulation transfer function of the imaging system. To estimate the semiempirical input to this model, 500 projection images (using an indirect, flat-panel x-ray detector in the breast CT system) were acquired with 50-100 kilovolt (kV) x-ray spectra filtered with 0.1-mm tin (Sn), 0.2-mm copper (Cu), 1.5-mm aluminum (Al), or 0.05-mm silver (Ag). The signal mean and variance of each detector element and the noise power spectra (NPS) were calculated and incorporated into this model for accuracy. Additionally, the modulation transfer function of the detector system was physically measured and incorporated in the image simulation steps. For validation purposes, simulated and measured projection images of air scans were compared using 40 kV∕0.1-mm Sn, 65 kV∕0.2-mm Cu, 85 kV∕1.5-mm Al, and 95 kV∕0.05-mm Ag. The linear relationship between the measured signal statistics and the energy-integrated x-ray spectrum was confirmed and incorporated into the model. The signal mean and variance factors were linearly related to kV for each filter material (r(2) of signal mean to k

A multi-panel direction-sensitive gamma-ray detector for low-altitude radiological searches

Energy Technology Data Exchange (ETDEWEB)

Becker, E.M.; Farsoni, A.T.

2016-11-11

A lightweight, low-cost multi-panel direction-sensitive radiation detector prototype has been developed at Oregon State University that is designed to be mounted on a small unmanned aerial system to autonomously search for radiation sources while flying close to the ground. The detection system comprises sixteen BGO-SiPM detector panels with an adjustable view angle, and signal outputs are processed in parallel in an FPGA. The minimum detectable activity was calculated to be 1.3 μCi of {sup 137}Cs at 1 m in under 60 s. The counting response of the detector panels were characterized and found to have 4.7% relative standard deviation, indicating good uniformity in overall design and assembly. The detector was also able to estimate the direction of a 12.3 μCi {sup 137}Cs source 100 cm from the device center with 2.3° accuracy in a 95% confidence width of 10.8° in 60 s.

Solid-state, flat-panel, digital radiography detectors and their physical imaging characteristics

Energy Technology Data Exchange (ETDEWEB)

Cowen, A.R. [LXi Research, Academic Unit of Medical Physics, University of Leeds, West Yorkshire (United Kingdom)], E-mail: a.r.cowen@leeds.ac.uk; Kengyelics, S.M.; Davies, A.G. [LXi Research, Academic Unit of Medical Physics, University of Leeds, West Yorkshire (United Kingdom)

2008-05-15

Solid-state, digital radiography (DR) detectors, designed specifically for standard projection radiography, emerged just before the turn of the millennium. This new generation of digital image detector comprises a thin layer of x-ray absorptive material combined with an electronic active matrix array fabricated in a thin film of hydrogenated amorphous silicon (a-Si:H). DR detectors can offer both efficient (low-dose) x-ray image acquisition plus on-line readout of the latent image as electronic data. To date, solid-state, flat-panel, DR detectors have come in two principal designs, the indirect-conversion (x-ray scintillator-based) and the direct-conversion (x-ray photoconductor-based) types. This review describes the underlying principles and enabling technologies exploited by these designs of detector, and evaluates their physical imaging characteristics, comparing performance both against each other and computed radiography (CR). In standard projection radiography indirect conversion DR detectors currently offer superior physical image quality and dose efficiency compared with direct conversion DR and modern point-scan CR. These conclusions have been confirmed in the findings of clinical evaluations of DR detectors. Future trends in solid-state DR detector technologies are also briefly considered. Salient innovations include WiFi-enabled, portable DR detectors, improvements in x-ray absorber layers and developments in alternative electronic media to a-Si:H.

Development of a cone-beam CT system for radiological technologist education

International Nuclear Information System (INIS)

Teramoto, Atsushi; Ohara, Ken; Ozaki, Kaho; Miyashita, Mariko; Ohno, Tomoyuki; Tsuzaka, Masatoshi; Fujita, Hiroshi

2011-01-01

For radiological technologists, it is very important to understand the principle of computed tomography (CT) and CT artifacts derived from mechanical and electrical failure. In this study, a CT system for educating radiological technologists was developed. The system consisted of a cone-beam CT scanner and educational software. The cone-beam CT scanner has a simple structure, using a micro-focus X-ray tube and an indirect-conversion flat panel detector. For the educational software, we developed various educational functions of image reconstruction and reconstruction parameters as well as CT artifacts. In the experiments, the capabilities of the system were evaluated using an acrylic phantom. We verified that the system produced the expected results. (author)

A preliminary study on cone beam CT image based treatment planning

International Nuclear Information System (INIS)

Padmanaban, Sriram; Jeevanandham, Prakash; Boopathy, Raghavendiran; Sukumar, Prabakar; Syam Kumar, S.A.; Kunjithapatham, Bhuvana; Nagarajan, Vivekanandan

2008-01-01

Kilovolt Cone beam computed tomography (CBCT) based on flat panel technology is primarily used for positioning verification. However it is required to evaluate the accuracy of dose calculation based on CBCT images for the purpose of re-planning in adaptive radiation therapy (ART). In this study, 3DCRT and IMRT plans were done using both the planning CT and CBCT images and the corresponding variations in dose and MUs were analyzed, hence evaluating the feasibility of using kilovolt CBCT for dose calculation and patient dose verification. (author)

Dual-energy cone-beam CT with a flat-panel detector: Effect of reconstruction algorithm on material classification

International Nuclear Information System (INIS)

Zbijewski, W.; Gang, G. J.; Xu, J.; Wang, A. S.; Stayman, J. W.; Taguchi, K.; Carrino, J. A.; Siewerdsen, J. H.

2014-01-01

Purpose: Cone-beam CT (CBCT) with a flat-panel detector (FPD) is finding application in areas such as breast and musculoskeletal imaging, where dual-energy (DE) capabilities offer potential benefit. The authors investigate the accuracy of material classification in DE CBCT using filtered backprojection (FBP) and penalized likelihood (PL) reconstruction and optimize contrast-enhanced DE CBCT of the joints as a function of dose, material concentration, and detail size. Methods: Phantoms consisting of a 15 cm diameter water cylinder with solid calcium inserts (50–200 mg/ml, 3–28.4 mm diameter) and solid iodine inserts (2–10 mg/ml, 3–28.4 mm diameter), as well as a cadaveric knee with intra-articular injection of iodine were imaged on a CBCT bench with a Varian 4343 FPD. The low energy (LE) beam was 70 kVp (+0.2 mm Cu), and the high energy (HE) beam was 120 kVp (+0.2 mm Cu, +0.5 mm Ag). Total dose (LE+HE) was varied from 3.1 to 15.6 mGy with equal dose allocation. Image-based DE classification involved a nearest distance classifier in the space of LE versus HE attenuation values. Recognizing the differences in noise between LE and HE beams, the LE and HE data were differentially filtered (in FBP) or regularized (in PL). Both a quadratic (PLQ) and a total-variation penalty (PLTV) were investigated for PL. The performance of DE CBCT material discrimination was quantified in terms of voxelwise specificity, sensitivity, and accuracy. Results: Noise in the HE image was primarily responsible for classification errors within the contrast inserts, whereas noise in the LE image mainly influenced classification in the surrounding water. For inserts of diameter 28.4 mm, DE CBCT reconstructions were optimized to maximize the total combined accuracy across the range of calcium and iodine concentrations, yielding values of ∼88% for FBP and PLQ, and ∼95% for PLTV at 3.1 mGy total dose, increasing to ∼95% for FBP and PLQ, and ∼98% for PLTV at 15.6 mGy total dose. For a

Cone-beam volume CT mammographic imaging: feasibility study

Science.gov (United States)

Chen, Biao; Ning, Ruola

2001-06-01

X-ray projection mammography, using a film/screen combination or digital techniques, has proven to be the most effective imaging modality for early detection of breast cancer currently available. However, the inherent superimposition of structures makes small carcinoma (a few millimeters in size) difficult to detect in the occultation case or in dense breasts, resulting in a high false positive biopsy rate. The cone-beam x-ray projection based volume imaging using flat panel detectors (FPDs) makes it possible to obtain three-dimensional breast images. This may benefit diagnosis of the structure and pattern of the lesion while eliminating hard compression of the breast. This paper presents a novel cone-beam volume CT mammographic imaging protocol based on the above techniques. Through computer simulation, the key issues of the system and imaging techniques, including the x-ray imaging geometry and corresponding reconstruction algorithms, x-ray characteristics of breast tissues, x-ray setting techniques, the absorbed dose estimation and the quantitative effect of x-ray scattering on image quality, are addressed. The preliminary simulation results support the proposed cone-beam volume CT mammographic imaging modality in respect to feasibility and practicability for mammography. The absorbed dose level is comparable to that of current two-view mammography and would not be a prominent problem for this imaging protocol. Compared to traditional mammography, the proposed imaging protocol with isotropic spatial resolution will potentially provide significantly better low contrast detectability of breast tumors and more accurate location of breast lesions.

Image quality analysis of vibration effects In C-arm-flat panel X-ray imaging

NARCIS (Netherlands)

Snoeren, R.M.; Kroon, J.N.; With, de P.H.N.

2011-01-01

The motion of C-arm scanning X-ray systems may result in vibrations of the imaging sub-system. In this paper, we connect C-arm system vibrations to Image Quality (IQ) deterioration for 2D angiography and 3D cone beam X-ray imaging, using large Flat Panel detectors. Vibrations will affect the

First results with a microcavity plasma panel detector

Energy Technology Data Exchange (ETDEWEB)

Ball, R. [University of Michigan, Department of Physics, Ann Arbor, MI 48109 (United States); Ben-Moshe, M.; Benhammou, Y.; Bensimon, R. [Tel Aviv University, School of Physics and Astronomy, Tel Aviv (Israel); Chapman, J.W. [University of Michigan, Department of Physics, Ann Arbor, MI 48109 (United States); Davies, M.; Etzion, E. [Tel Aviv University, School of Physics and Astronomy, Tel Aviv (Israel); Ferretti, C., E-mail: claudiof@umich.edu [University of Michigan, Department of Physics, Ann Arbor, MI 48109 (United States); Friedman, P.S. [Integrated Sensors, LLC, Ottawa Hills, OH 43606 (United States); Levin, D.S. [University of Michigan, Department of Physics, Ann Arbor, MI 48109 (United States); Silver, Y. [Tel Aviv University, School of Physics and Astronomy, Tel Aviv (Israel); Varner, R.L. [Oak Ridge National Laboratory, Physics Division, Oak Ridge, TN 737831 (United States); Weaverdyck, C.; Zhou, B. [University of Michigan, Department of Physics, Ann Arbor, MI 48109 (United States)

2015-06-01

A new type of gaseous micropattern particle detector based on a closed-cell microcavity plasma panel sensor is reported. The first device was fabricated with 1×1×2 mm cells. It has shown very clean signals of 0.6–2.5 V amplitude, fast rise time of approximately 2 ns and FWHM of about 2 ns with very uniform signal shapes across all pixels. From initial measurements with β particles from a radioactive source, a maximum pixel efficiency greater than 95% is calculated, for operation of the detector over a 100 V wide span of high voltages (HV). Over this same HV range, the background rate per pixel was measured to be 3–4 orders of magnitude lower than the rate with which the cell was illuminated by the β source. Pixel-to-pixel count rate uniformity is within 3% and stable within 3% for many days. The time resolution is 2.4 ns, and a very low cell-to-cell crosstalk has been measured between cells separated by 2 mm.

The effect of dose reduction on image quality in digital radiography using a flat-panel detector: experimental study in rabbits

International Nuclear Information System (INIS)

Jung, Sung Il; Goo, Jin Mo; Lee, Hyun Ju; Moon, Woo Kyung; Lim, Kun Young; Cho, Gyung Goo; Kim, Ji Hoon; Im, Jung Gi; Choi, Jang Yong; Nam, Sang Hee

2005-01-01

To evaluate the effect of dose reduction on image quality in digital radiography using a flat-panel detector. Digital radiographs of 30 rabbits were obtained at two different dose levels (33.23 μGY for the standard dose group and 20.09 μGY for the reduced dose group). The amorphous selenium-based flat-panel detector system had a panel size of 7 x 8.5 inches, a matrix of 1280 x 1536 (pixels?), and a pixel pitch of 138 μm. Four observers evaluated the soft-copy images on a high-resolution video monitor (2560 x 2048 x 8 bits) in random order. The observers rated the visibility of 13 different anatomic structures on a 5-point scale, viz, the retrocardiac lung, subdiaphragmatic lung, heart border, diaphragmatic border, proximal airway, unobscured lung, liver border, kidney border, bowel gas, flank stripe, ribs, and vertebrae in the mediastinal and abdominal regions. Statistical significance was determined using Wilcoxon's signed rank test. There was no statistically significant difference in the visibility of the anatomic structures on digital radiography between the standard and reduced dose groups. Digital radiography using an amorphous selenium-based flat-panel detector can preserve the image quality, though the dose is reduced to 40% of the standard level

The effect of dose reduction on image quality in digital radiography using a flat-panel detector: experimental study in rabbits

Energy Technology Data Exchange (ETDEWEB)

Jung, Sung Il; Goo, Jin Mo; Lee, Hyun Ju; Moon, Woo Kyung; Lim, Kun Young; Cho, Gyung Goo; Kim, Ji Hoon; Im, Jung Gi [Seoul National College of Medicine, Seoul (Korea, Republic of); Choi, Jang Yong; Nam, Sang Hee [Inje University, Seoul (Korea, Republic of)

2005-07-15

To evaluate the effect of dose reduction on image quality in digital radiography using a flat-panel detector. Digital radiographs of 30 rabbits were obtained at two different dose levels (33.23 {mu}GY for the standard dose group and 20.09 {mu}GY for the reduced dose group). The amorphous selenium-based flat-panel detector system had a panel size of 7 x 8.5 inches, a matrix of 1280 x 1536 (pixels?), and a pixel pitch of 138 {mu}m. Four observers evaluated the soft-copy images on a high-resolution video monitor (2560 x 2048 x 8 bits) in random order. The observers rated the visibility of 13 different anatomic structures on a 5-point scale, viz, the retrocardiac lung, subdiaphragmatic lung, heart border, diaphragmatic border, proximal airway, unobscured lung, liver border, kidney border, bowel gas, flank stripe, ribs, and vertebrae in the mediastinal and abdominal regions. Statistical significance was determined using Wilcoxon's signed rank test. There was no statistically significant difference in the visibility of the anatomic structures on digital radiography between the standard and reduced dose groups. Digital radiography using an amorphous selenium-based flat-panel detector can preserve the image quality, though the dose is reduced to 40% of the standard level.

Practical expressions describing detective quantum efficiency in flat-panel detectors

Science.gov (United States)

Kim, H. K.

2011-11-01

In radiology, image quality excellence is a balance between system performance and patient dose, hence x-ray systems must be designed to ensure the maximum image quality is obtained for the lowest consistent dose. The concept of detective quantum efficiency (DQE) is widely used to quantify, understand, measure, and predict the performance of x-ray detectors and imaging systems. Cascaded linear-systems theory can be used to estimate DQE based on the system design parameters and this theoretical DQE can be utilized for determining the impact of various physical processes, such as secondary quantum sinks, noise aliasing, reabsorption noise, and others. However, the prediction of DQE usually requires tremendous efforts to determine each parameter consisting of the cascaded linear-systems model. In this paper, practical DQE formalisms assessing both the photoconductor- and scintillator-based flat-panel detectors under quantum-noise-limited operation are described. The developed formalisms are experimentally validated and discussed for their limits. The formalisms described in this paper would be helpful for the rapid prediction of the DQE performances of developing systems as well as the optimal design of systems.

Panel on accelerators and detectors in the 1950s

International Nuclear Information System (INIS)

Jones, L.W.; Amaldi, U.; Hofstadter, R.; Kerst, D.W.; Wilson, R.R.

1989-01-01

The article takes the form of a panel of famous particle physics scientists discussing accelerator design and detectors used in the 1950s. The discussion ranges over accelerator energy capacities, the invention of alternating-gradient focusing, and colliding beam machines, beam stacking and the application of digital computers to accelerator calculations. The development of particle beams using strong-focusing lenses and electrostatic separators rounded off the decade. Detectors moved from bubble chambers, the use of plastic and inorganic scintillators, to hadron calorimeters, Cherenkov counters and finally spark chambers. Various discoveries made using sodium iodide scintillation counters are noted. (UK)

Dose optimisation for intraoperative cone-beam flat-detector CT in paediatric spinal surgery

International Nuclear Information System (INIS)

Petersen, Asger Greval; Eiskjaer, Soeren; Kaspersen, Jon

2012-01-01

During surgery for spinal deformities, accurate placement of pedicle screws may be guided by intraoperative cone-beam flat-detector CT. The purpose of this study was to identify appropriate paediatric imaging protocols aiming to reduce the radiation dose in line with the ALARA principle. Using O-arm registered (Medtronic, Inc.), three paediatric phantoms were employed to measure CTDI w doses with default and lowered exposure settings. Images from 126 scans were evaluated by two spinal surgeons and scores were compared (Kappa statistics). Effective doses were calculated. The recommended new low-dose 3-D spine protocols were then used in 15 children. The lowest acceptable exposure as judged by image quality for intraoperative use was 70 kVp/40 mAs, 70 kVp/80 mAs and 80 kVp/40 mAs for the 1-, 5- and 12-year-old-equivalent phantoms respectively (kappa = 0,70). Optimised dose settings reduced CTDI w doses 89-93%. The effective dose was 0.5 mSv (91-94,5% reduction). The optimised protocols were used clinically without problems. Radiation doses for intraoperative 3-D CT using a cone-beam flat-detector scanner could be reduced at least 89% compared to manufacturer settings and still be used to safely navigate pedicle screws. (orig.)

Flat panel detectors - closing the (digital) gap in chest and skeletal radiology

International Nuclear Information System (INIS)

Reiff, Kurt J.

1999-01-01

In the radiological department today the majority of all X-ray procedures on chest and skeletal radiography is performed with classical film-screen-systems. Using digital luminescence radiography (DLR or CR, which stands for Computed Radiography) as a technique has shown a way to replace this 100-year-old procedure of doing general radiography work by acquiring the X-rays digitally via phosphor screens, but this approach has faced criticism from lots of radiologists world wide and therefore has not been widely accepted except in the intensive care environment. A new technology is now rising based on the use of so called flat panel X-ray (FD) detectors. Semi-conducting material detects the X-rays in digital form directly and creates an instantaneous image for display, distribution and diagnosis. This ability combined with a large field of view and -- compared to existing methods -- excellent detective quantum efficiency represents a revolutionary step for chest and skeletal radiography and will put basic X-ray-work back into the focus of radiological solutions. This paper will explain the basic technology of flat panel detectors, possible system solutions based on this new technology, aspects of the user interface influencing the system utilization and versatility as well as the possibility to redefine the patient examination process for chest and skeletal radiography. Furthermore the author discusses limitations for the first released systems, upgrades for the installed base and possible scenarios for the future. e.g. fluoroscopy or angiography application

Digital radiography with a large-scale electronic flat-panel detector vs screen-film radiography: observer preference in clinical skeletal diagnostics

International Nuclear Information System (INIS)

Hamers, S.; Freyschmidt, J.; Neitzel, U.

2001-01-01

The imaging performance of a recently developed digital flat-panel detector system was compared with conventional screen-film imaging in an observer preference study. In total, 34 image pairs of various regions of the skeleton were obtained in 24 patients; 30 image pairs were included in the study. The conventional images were acquired with 250- and 400-speed screen-film combinations, using the standard technique of our department. Within hours, the digital images were obtained using identical exposure parameters. The digital system employed a large-area (43 x 43 cm) flat-panel detector based on amorphous silicon (Trixell Pixium 4600), integrated in a Bucky table. Six radiologists independently evaluated the image pairs with respect to image latitude, soft tissue rendition, rendition of the periosteal and enosteal border of cortical bone, rendition of cancellous bone and the visibility of potentially present pathological changes, using a subjective five-point scale. The digital images were rated significantly (p=0.001) better than the screen-film images with respect to soft tissue rendition and image latitude. Also the rendition of the cancellous bone and the periosteal and enosteal border of the cortical bone was rated significantly (p=0.05) better for the flat-panel detector. The visibility of pathological lesions was equivalent; only large-area sclerotic lesions (n=2) were seen superiorly on screen-film images. The new digital flat-panel detector based on amorphous silicon appears to be at least equivalent to conventional screen-film combinations for skeletal examinations, and in most respects even superior. (orig.)

Auto calibration of a cone-beam-CT

International Nuclear Information System (INIS)

Gross, Daniel; Heil, Ulrich; Schulze, Ralf; Schoemer, Elmar; Schwanecke, Ulrich

2012-01-01

Purpose: This paper introduces a novel autocalibration method for cone-beam-CTs (CBCT) or flat-panel CTs, assuming a perfect rotation. The method is based on ellipse-fitting. Autocalibration refers to accurate recovery of the geometric alignment of a CBCT device from projection images alone, without any manual measurements. Methods: The authors use test objects containing small arbitrarily positioned radio-opaque markers. No information regarding the relative positions of the markers is used. In practice, the authors use three to eight metal ball bearings (diameter of 1 mm), e.g., positioned roughly in a vertical line such that their projection image curves on the detector preferably form large ellipses over the circular orbit. From this ellipse-to-curve mapping and also from its inversion the authors derive an explicit formula. Nonlinear optimization based on this mapping enables them to determine the six relevant parameters of the system up to the device rotation angle, which is sufficient to define the geometry of a CBCT-machine assuming a perfect rotational movement. These parameters also include out-of-plane rotations. The authors evaluate their method by simulation based on data used in two similar approaches [L. Smekal, M. Kachelriess, S. E, and K. Wa, “Geometric misalignment and calibration in cone-beam tomography,” Med. Phys. 31(12), 3242–3266 (2004); K. Yang, A. L. C. Kwan, D. F. Miller, and J. M. Boone, “A geometric calibration method for cone beam CT systems,” Med. Phys. 33(6), 1695–1706 (2006)]. This allows a direct comparison of accuracy. Furthermore, the authors present real-world 3D reconstructions of a dry human spine segment and an electronic device. The reconstructions were computed from projections taken with a commercial dental CBCT device having two different focus-to-detector distances that were both calibrated with their method. The authors compare their reconstruction with a reconstruction computed by the manufacturer of the

Digital chest radiography: flat-panel detectors or conventional radiographs

International Nuclear Information System (INIS)

Schaefer-Prokop, C.; Uffmann, M.; Sailer, J.; Kabalan, N.; Herold, C.; Prokop, M.

2003-01-01

Flat panel detectors are characterized by improved handling and increased dose efficiency. This allows for increasing of work flow efficiency and for reducing the exposure dose by about 50% compared to current systems with a sensitivity of 400. Whether the increased dose efficiency should be used to reduce acquisition dose or to increase image quality in the chest, will be shown by further clinical experience and will be also determined by the subjective preference of the radiologists. The decreased level of image noise opens new perspectives for image processing that way that elaborated multifrequency processing allows for optimizing the display of very small and low contrast structures that was so far limited by overlying image noise. Specialized applications of dual energy subtraction and temporal subtraction will also profit by the new detector technology and will be further driven forward in context with applications such as computed assisted diagnosis even though this is currently not yet broadly applied. Storage phosphor radiography still represents an important alternative technique based on its larger flexibility with respect to equipment configuration, its broader application options in intensive care and emergency radiology and due to economic reasons. These facts are further underlined by the fact that image quality also in storage phosphor radiography could be constantly increased by improving detector technology and image processing and consequently has a high standard. (orig.) [de

Dynamic chest radiography: flat-panel detector (FPD) based functional X-ray imaging.

Science.gov (United States)

Tanaka, Rie

2016-07-01

Dynamic chest radiography is a flat-panel detector (FPD)-based functional X-ray imaging, which is performed as an additional examination in chest radiography. The large field of view (FOV) of FPDs permits real-time observation of the entire lungs and simultaneous right-and-left evaluation of diaphragm kinetics. Most importantly, dynamic chest radiography provides pulmonary ventilation and circulation findings as slight changes in pixel value even without the use of contrast media; the interpretation is challenging and crucial for a better understanding of pulmonary function. The basic concept was proposed in the 1980s; however, it was not realized until the 2010s because of technical limitations. Dynamic FPDs and advanced digital image processing played a key role for clinical application of dynamic chest radiography. Pulmonary ventilation and circulation can be quantified and visualized for the diagnosis of pulmonary diseases. Dynamic chest radiography can be deployed as a simple and rapid means of functional imaging in both routine and emergency medicine. Here, we focus on the evaluation of pulmonary ventilation and circulation. This review article describes the basic mechanism of imaging findings according to pulmonary/circulation physiology, followed by imaging procedures, analysis method, and diagnostic performance of dynamic chest radiography.

Nine-degrees-of-freedom flexmap for a cone-beam computed tomography imaging device with independently movable source and detector.

Science.gov (United States)

Keuschnigg, Peter; Kellner, Daniel; Fritscher, Karl; Zechner, Andrea; Mayer, Ulrich; Huber, Philipp; Sedlmayer, Felix; Deutschmann, Heinz; Steininger, Philipp

2017-01-01

Couch-mounted cone-beam computed tomography (CBCT) imaging devices with independently rotatable x-ray source and flat-panel detector arms for acquisitions of arbitrary regions of interest (ROI) have recently been introduced in image-guided radiotherapy (IGRT). This work analyzes mechanical limitations and gravity-induced effects influencing the geometric accuracy of images acquired with arbitrary angular constellations of source and detector in nonisocentric trajectories, which is considered essential for IGRT. In order to compensate for geometric inaccuracies of this modality, a 9-degrees-of-freedom (9-DOF) flexmap correction approach is presented, focusing especially on the separability of the flexmap parameters of the independently movable components of the device. The 9-DOF comprise a 3D translation of the x-ray source focal spot, a 3D translation of the flat-panel's active area center and three Euler-rotations of the detector's row and column vectors. The flexmap parameters are expressed with respect to the angular position of each of the devices arms. Estimation of the parameters is performed, using a CT-based structure set of a table-mounted, cylindrical ball-bearing phantom. Digitally reconstructed radiograph (DRR) patches are derived from the structure set followed by local 2D in-plane registration and subsequent 3D transform estimation by nonlinear regression with outlier detection. Flexmap parameter evaluations for the factory-calibrated system in clockwise and counter-clockwise rotation direction have shown only minor differences for the overall set of flexmap parameters. High short-term reproducibility of the flexmap parameters has been confirmed by experiments over 10 acquisitions for both directions, resulting in standard deviation values of ≤0.183 mm for translational components and ≤0.0219 deg for rotational components, respectively. A comparison of isocentric and nonisocentric flexmap evaluations showed that the mean differences of the

On site evaluation of three flat panel detectors for digital radiography

International Nuclear Information System (INIS)

Borasi, Giovanni; Nitrosi, Andrea; Ferrari, Paolo; Tassoni, Davide

2003-01-01

During a tender we evaluated the image performance of three commercially available active matrix flat panel imagers (AMFPI) for general radiography, one based on direct detection method (Se photoconductor) the other two on indirect detection method (CsI phosphor). Basic image quality parameters (MTF, NNPS, DQE) were evaluated with particular attention to dose and energy dependence. As it is known, presampling modulation transfer function (MTF) of selenium based detector is very high (at 70 kV, 2 cycles/mm, 2.5 μGy, about 0.80). Indirect detection panels exhibit a comparable (lower) resolution (at 70 kV, 2 cycles/mm, 2.5 μGy, MTF is about 0.34 for both the systems analyzed) and a more pronounced energy and dose dependence could also be noted in one of them. As a consequence of the very high resolution, the normalized noise power spectrum (NNPS) of the direct system is substantially flat, very similar to a white noise. Considering that the sensitive layer of all detectors is the same (0.5 mm), the relatively higher NNPS values are related to selenium absorption properties (lower Z respect to CsI:Tl) and detector inherent noise. NNPSs of the other systems, at low frequencies, are comparable but the frequency dependence is significantly different. At 70 kV, 2.5 μGy, 0.5 cycles/mm detective quantum efficiency (DQE) is about 0.35 for the direct detection system, and about the same (0.6) for the indirect ones. The combined effect of additive and multiplicative noise components makes DQE dependence on dose not monotonic. DQE present a maximum for an intermediate exposure. This complex behavior may be useful to characterize the systems in terms of the monodimensional integral over the frequency of DQE (IDQE). Both visual contrast-detail experiment and the direct evaluation of the signal-to-noise ratio confirmed, at least in a qualitative way, the system performances predicted by IDQE

Flat panel computed tomography of human ex vivo heart and bone specimens: initial experience

Energy Technology Data Exchange (ETDEWEB)

Nikolaou, Konstantin; Becker, Christoph R.; Reiser, Maximilian F. [Ludwig-Maximilians-University, Department of Clinical Radiology, Munich (Germany); Flohr, Thomas; Stierstorfer, Karl [CT Division, Siemens Medical Solutions, Forchheim (Germany)

2005-02-01

The aim of this technical investigation was the detailed description of a prototype flat panel detector computed tomography system (FPCT) and its initial evaluation in an ex vivo setting. The prototype FPCT scanner consists of a conventional radiographic flat panel detector, mounted on a multi-slice CT scanner gantry. Explanted human ex vivo heart and foot specimens were examined. Images were reformatted with various reconstruction algorithms and were evaluated for high-resolution anatomic information. For comparison purposes, the ex vivo specimens were also scanned with a conventional 16-detector-row CT scanner (Sensation 16, Siemens Medical Solutions, Forchheim, Germany). With the FPCT prototype used, a 1,024 x 768 resolution matrix can be obtained, resulting in an isotropic voxel size of 0.25 x 0.25 x 0.25 mm at the iso-center. Due to the high spatial resolution, very small structures such as trabecular bone or third-degree, distal branches of coronary arteries could be visualized. This first evaluation showed that flat panel detector systems can be used in a cone-beam computed tomography scanner and that very high spatial resolutions can be achieved. However, there are limitations for in vivo use due to constraints in low contrast resolution and slow scan speed. (orig.)

A cone-beam reconstruction algorithm using shift-variant filtering and cone-beam backprojection

International Nuclear Information System (INIS)

Defrise, M.; Clack, R.

1994-01-01

An exact inversion formula written in the form of shift-variant filtered-backprojection (FBP) is given for reconstruction from cone-beam data taken from any orbit satisfying Tuy's sufficiency conditions. The method is based on a result of Grangeat, involving the derivative of the three-dimensional (3-D) Radon transform, but unlike Grangeat's algorithm, no 3D rebinning step is required. Data redundancy, which occurs when several cone-beam projections supply the same values in the Radon domain, is handled using an elegant weighting function and without discarding data. The algorithm is expressed in a convenient cone-beam detector reference frame, and a specific example for the case of a dual orthogonal circular orbit is presented. When the method is applied to a single circular orbit, it is shown to be equivalent to the well-known algorithm of Feldkamp et al

A method to determine the detector locations of the cone-beam projection of the balls’ centers

International Nuclear Information System (INIS)

Deng, Lin; Xi, Xiaoqi; Li, Lei; Han, Yu; Yan, Bin

2015-01-01

In geometric calibration of cone-beam computed tomography (CBCT), sphere-like objects such as balls are widely imaged, the positioning information of which is obtained to determine the unknown geometric parameters. In this process, the accuracy of the detector location of CB projection of the center of the ball, which we call the center projection, is very important, since geometric calibration is sensitive to errors in the positioning information. Currently in almost all the geometric calibration using balls, the center projection is invariably estimated by the center of the support of the projection or the centroid of the intensity values inside the support approximately. Clackdoyle’s work indicates that the center projection is not always at the center of the support or the centroid of the intensity values inside, and has given a quantitative analysis of the maximum errors in evaluating the center projection by the centroid. In this paper, an exact method is proposed to calculate the center projection, utilizing both the detector location of the ellipse center and the two axis lengths of the ellipse. Numerical simulation results have demonstrated the precision and the robustness of the proposed method. Finally there are some comments on this work with non-uniform density balls, as well as the effect by the error occurred in the evaluation for the location of the orthogonal projection of the cone vertex onto the detector. (paper)

Exact cone beam CT with a spiral scan

International Nuclear Information System (INIS)

Tam, K.C.; Samarasekera, S.; Sauer, F.

1998-01-01

A method is developed which makes it possible to scan and reconstruct an object with cone beam x-rays in a spiral scan path with area detectors much shorter than the length of the object. The method is mathematically exact. If only a region of interest of the object is to be imaged, a top circle scan at the top level of the region of interest and a bottom circle scan at the bottom level of the region of interest are added. The height of the detector is required to cover only the distance between adjacent turns in the spiral projected at the detector. To reconstruct the object, the Radon transform for each plane intersecting the object is computed from the totality of the cone beam data. This is achieved by suitably combining the cone beam data taken at different source positions on the scan path; the angular range of the cone beam data required at each source position can be determined easily with a mask which is the spiral scan path projected on the detector from the current source position. The spiral scan algorithm has been successfully validated with simulated cone beam data. (author)

Using a Borated Panel to Form a Dual Neutron-Gamma Detector

Energy Technology Data Exchange (ETDEWEB)

Scott Wilde; Raymond Keegan

2008-06-20

A borated polyethylene plane placed between a neutron source and a gamma spectrometer is used to form a dual neutron-gamma detection system. The polyethylene thermalizes the source neutrons so that they are captured by {sup 10}B to produce a flux of 478 keV gamma-rays that radiate from the plane. This results in a buildup of count rate in the detector over that from a disk of the same diameter as the detector crystal (same thickness as the panel). Radiation portal systems are a potential application of this technique.

Cone-beam volume CT breast imaging: Feasibility study

International Nuclear Information System (INIS)

Chen Biao; Ning Ruola

2002-01-01

X-ray projection mammography, using a film/screen combination, or digital techniques, has proven to be the most effective imaging modality currently available for early detection of breast cancer. However, the inherent superimposition of structures makes a small carcinoma (a few millimeters in size) difficult to detect when it is occult or in dense breasts, leading to a high false-positive biopsy rate. Cone-beam x-ray-projection-based volume imaging using flat panel detectors (FPDs) may allow obtaining three-dimensional breast images, resulting in more accurate diagnosis of structures and patterns of lesions while eliminating the hard compression of breasts. This article presents a novel cone-beam volume computed tomographic breast imaging (CBVCTBI) technique based on the above techniques. Through a variety of computer simulations, the key issues of the system and imaging techniques were addressed, including the x-ray imaging geometry and corresponding reconstruction algorithms, x-ray characteristics of breast tissue and lesions, x-ray setting techniques, the absorbed dose estimation, and the quantitative effect of x-ray scattering on image quality. The preliminary simulation results support the proposed CVBCTBI modality for breast imaging in respect to its feasibility and practicability. The absorbed dose level is comparable to that of current mammography and will not be a prominent problem for this imaging technique. Compared to conventional mammography, the proposed imaging technique with isotropic spatial resolution will potentially provide significantly better low-contrast detectability of breast tumors and more accurate location of breast lesions

Performance Characteristic of a CsI(Tl) Flat Panel Detector Radiography System

International Nuclear Information System (INIS)

Jeong, Hoi Woun; Min, Jung Hwan; Kim, Jung Min; Park, Min Seok; Lee, Gaung Young

2012-01-01

The purpose of this work was to evaluate an amorphous silicon cesium iodide based indirect flat-panel detector (FPD) in terms of their modulation transfer function (MTF), Wiener spectrum (WS, or noise power spectrum, NPS), and detective quantum efficiency (DQE). Measurements were made on flat-panel detector using the International Electrotechnical Commission (IEC) defined RQA3, RQA5, RQA7, and RQA9 radiographic technique. The MTFs of the systems were measured using an edge method. The WS(NPS) of the systems were determined for a range of exposure levels by two-dimensional (2D). Fourier analysis of uniformly exposed radiographs. The DQEs were assessed from the measured MTF, WS(NPS), exposure, and estimated ideal signal-to-noise ratios. Characteristic curve in the RQA3 showed difference in the characteristic curve from RQA5, RQA7, RQA9. MTFs were not differences according to x-ray beam quality. WS(NPS) was reduced with increasing dose, and RQA 3, RQA5, RQA7, RQA9 as the order is reduced. DQE represented the best in the 1mR, RQA 3, RQA5, RQA7, RQA9 decrease in the order. The physical imaging characteristics of FPD may also differ from input beam quality. This study gives an initial motivation that the physical imaging characteristics of FPD is an important issue for the right use of digital radiography system.

Performance Characteristic of a CsI(Tl) Flat Panel Detector Radiography System

Energy Technology Data Exchange (ETDEWEB)

Jeong, Hoi Woun [Dept. of Radiological Science, Baekseok Culture University, Seoul (Korea, Republic of); Min, Jung Hwan [Dept. of Radiological Technology, Shingu University, Seongnam (Korea, Republic of); Kim, Jung Min [Dept. of Radiological Science, Korea University, Health Science College, Seoul (Korea, Republic of); Park, Min Seok [Korea Institue of Radiological and Medical Sicences, Research Institute of Radiologycal and Medical Sciences, Seoul (Korea, Republic of); Lee, Gaung Young [National Institute of Food and Drug Safety Evaluation, Seoul (Korea, Republic of)

2012-06-15

The purpose of this work was to evaluate an amorphous silicon cesium iodide based indirect flat-panel detector (FPD) in terms of their modulation transfer function (MTF), Wiener spectrum (WS, or noise power spectrum, NPS), and detective quantum efficiency (DQE). Measurements were made on flat-panel detector using the International Electrotechnical Commission (IEC) defined RQA3, RQA5, RQA7, and RQA9 radiographic technique. The MTFs of the systems were measured using an edge method. The WS(NPS) of the systems were determined for a range of exposure levels by two-dimensional (2D). Fourier analysis of uniformly exposed radiographs. The DQEs were assessed from the measured MTF, WS(NPS), exposure, and estimated ideal signal-to-noise ratios. Characteristic curve in the RQA3 showed difference in the characteristic curve from RQA5, RQA7, RQA9. MTFs were not differences according to x-ray beam quality. WS(NPS) was reduced with increasing dose, and RQA 3, RQA5, RQA7, RQA9 as the order is reduced. DQE represented the best in the 1mR, RQA 3, RQA5, RQA7, RQA9 decrease in the order. The physical imaging characteristics of FPD may also differ from input beam quality. This study gives an initial motivation that the physical imaging characteristics of FPD is an important issue for the right use of digital radiography system.

WE-AB-207A-01: BEST IN PHYSICS (IMAGING): High-Resolution Cone-Beam CT of the Extremities and Cancellous Bone Architecture with a CMOS Detector

Energy Technology Data Exchange (ETDEWEB)

Cao, Q; Brehler, M; Sisniega, A; Marinetto, E; Stayman, J; Siewerdsen, J; Zbijewski, W [Johns Hopkins University, Baltimore, MD (United States); Zyazin, A; Peters, I [Teledyne DALSA, Eindhoven (Netherlands); Yorkston, J [Carestream Health, Inc, Penfield, NY (United States)

2016-06-15

Purpose: Extremity cone-beam CT (CBCT) with an amorphous silicon (aSi) flat-panel detector (FPD) provides low-dose volumetric imaging with high spatial resolution. We investigate the performance of the newer complementary metal-oxide semiconductor (CMOS) detectors to enhance resolution of extremities CBCT to ∼0.1 mm, enabling morphological analysis of trabecular bone. Quantitative in-vivo imaging of bone microarchitecture could present an important advance for osteoporosis and osteoarthritis diagnosis and therapy assessment. Methods: Cascaded systems models of CMOS- and FPD-based extremities CBCT were implemented. Performance was compared for a range of pixel sizes (0.05–0.4 mm), focal spot sizes (0.3–0.6 FS), and x-ray techniques (0.05–0.8 mAs/projection) using detectability of high-, low-, and all-frequency tasks for a nonprewhitening observer. Test-bench implementation of CMOS-based extremity CBCT involved a Teledyne DALSA Xineos3030HR detector with 0.099 mm pixels and a compact rotating anode x-ray source with 0.3 FS (IMD RTM37). Metrics of bone morphology obtained using CMOS-based CBCT were compared in cadaveric specimens to FPD-based system using a Varian PaxScan4030 (0.194 mm pixels). Results: Finer pixel size and reduced electronic noise for CMOS (136 e compared to 2000 e for FPD) resulted in ∼1.9× increase in detectability for high-frequency tasks and ∼1.1× increase for all-frequency tasks. Incorporation of the new x-ray source with reduced focal spot size (0.3 FS vs. 0.5 FS used on current extremities CBCT) improved detectability for CMOS-based CBCT by ∼1.7× for high-frequency tasks. Compared to FPD CBCT, the CMOS detector yielded improved agreement with micro-CT in measurements of trabecular thickness (∼1.7× reduction in relative error), bone volume (∼1.5× reduction), and trabecular spacing (∼3.5× reduction). Conclusion: Imaging performance modelling and experimentation indicate substantial improvements for high

WE-AB-207A-01: BEST IN PHYSICS (IMAGING): High-Resolution Cone-Beam CT of the Extremities and Cancellous Bone Architecture with a CMOS Detector

International Nuclear Information System (INIS)

Cao, Q; Brehler, M; Sisniega, A; Marinetto, E; Stayman, J; Siewerdsen, J; Zbijewski, W; Zyazin, A; Peters, I; Yorkston, J

2016-01-01

Purpose: Extremity cone-beam CT (CBCT) with an amorphous silicon (aSi) flat-panel detector (FPD) provides low-dose volumetric imaging with high spatial resolution. We investigate the performance of the newer complementary metal-oxide semiconductor (CMOS) detectors to enhance resolution of extremities CBCT to ∼0.1 mm, enabling morphological analysis of trabecular bone. Quantitative in-vivo imaging of bone microarchitecture could present an important advance for osteoporosis and osteoarthritis diagnosis and therapy assessment. Methods: Cascaded systems models of CMOS- and FPD-based extremities CBCT were implemented. Performance was compared for a range of pixel sizes (0.05–0.4 mm), focal spot sizes (0.3–0.6 FS), and x-ray techniques (0.05–0.8 mAs/projection) using detectability of high-, low-, and all-frequency tasks for a nonprewhitening observer. Test-bench implementation of CMOS-based extremity CBCT involved a Teledyne DALSA Xineos3030HR detector with 0.099 mm pixels and a compact rotating anode x-ray source with 0.3 FS (IMD RTM37). Metrics of bone morphology obtained using CMOS-based CBCT were compared in cadaveric specimens to FPD-based system using a Varian PaxScan4030 (0.194 mm pixels). Results: Finer pixel size and reduced electronic noise for CMOS (136 e compared to 2000 e for FPD) resulted in ∼1.9× increase in detectability for high-frequency tasks and ∼1.1× increase for all-frequency tasks. Incorporation of the new x-ray source with reduced focal spot size (0.3 FS vs. 0.5 FS used on current extremities CBCT) improved detectability for CMOS-based CBCT by ∼1.7× for high-frequency tasks. Compared to FPD CBCT, the CMOS detector yielded improved agreement with micro-CT in measurements of trabecular thickness (∼1.7× reduction in relative error), bone volume (∼1.5× reduction), and trabecular spacing (∼3.5× reduction). Conclusion: Imaging performance modelling and experimentation indicate substantial improvements for high

Fast kilovoltage/megavoltage (kVMV) breathhold cone-beam CT for image-guided radiotherapy of lung cancer

International Nuclear Information System (INIS)

Wertz, Hansjoerg; Stsepankou, Dzmitry; Blessing, Manuel; Boda-Heggemann, Judit; Hesser, Juergen; Lohr, Frank; Wenz, Frederik; Rossi, Michael; Gros, Uwe; Knox, Chris; Brown, Kevin; Walter, Cornelia

2010-01-01

Long image acquisition times of 60-120 s for cone-beam CT (CBCT) limit the number of patients with lung cancer who can undergo volume image guidance under breathhold. We developed a low-dose dual-energy kilovoltage-megavoltage-cone-beam CT (kVMV-CBCT) based on a clinical treatment unit reducing imaging time to ≤15 s. Simultaneous kVMV-imaging was achieved by dedicated synchronization hardware controlling the output of the linear accelerator (linac) based on detector panel readout signals, preventing imaging artifacts from interference of the linac's MV-irradiation and panel readouts. Optimization was performed to minimize the imaging dose. Single MV-projections, reconstructed MV-CBCT images and images of simultaneous 90 0 kV- and 90 0 MV-CBCT (180 0 kVMV-CBCT) were acquired with different parameters. Image quality and imaging dose were evaluated and compared to kV-imaging. Hardware-based kVMV synchronization resulted in artifact-free projections. A combined 180 0 kVMV-CBCT scan with a total MV-dose of 5 monitor units was acquired in 15 s and with sufficient image quality. The resolution was 5-6 line pairs cm -1 (Catphan phantom). The combined kVMV-scan dose was equivalent to a kV-radiation scan dose of ∼33 mGy. kVMV-CBCT based on a standard linac is promising and can provide ultra-fast online volume image guidance with low imaging dose and sufficient image quality for fast and accurate patient positioning for patients with lung cancer under breathhold.

Clinical evaluation of digital radiography based on a large-area cesium iodide-amorphous silicon flat-panel detector compared with screen-film radiography for skeletal system and abdomen

International Nuclear Information System (INIS)

Okamura, Terue; Tanaka, Saori; Koyama, Koichi; Norihumi, Nishida; Daikokuya, Hideo; Matsuoka, Toshiyuki; Yamada, Ryusaku; Kishimoto, Kenji; Hatagawa, Masakatsu; Kudoh, Hiroaki

2002-01-01

The aim of this clinical study was to compare the image quality of digital radiography using the new digital Bucky system based on a flat-panel detector with that of a conventional screen-film system for the skeletal structure and the abdomen. Fifty patients were examined using digital radiography with a flat-panel detector and screen-film systems, 25 for the skeletal structures and 25 for the abdomen. Six radiologists judged each paired image acquired under the same exposure parameters concerning three observation items for the bone and six items for the abdomen. Digital radiographic images for the bone were evaluated to be similar to screen-film images at the mean of 42.2%, to be superior at 50.2%, and to be inferior at 7.6%. Digital radiographic images for the abdomen were judged to be similar to screen-film images at the mean of 43.4%, superior at 52.4%, and inferior at 4.2%; thus, digital radiographic images were estimated to be either similar as or superior to screen-film images at over 92% for the bone and abdomen. On the statistical analysis, digital radiographic images were also judged to be preferred significantly in the most items for the bone and abdomen. In conclusion, the image quality of digital radiography with a flat-panel detector was superior to that of a screen-film system under the same exposure parameters, suggesting that dose reduction is possible with digital radiography. (orig.)

Search for Physics beyond the Standard Model with the ATLAS detector and the development of radiation detectors

CERN Document Server

Silver, Yiftah

We are investigating a radiation detector based on plasma display panel technology, the principal component of plasma television displays. This Plasma Panel Sensor (PPS) technology is a variant of micro-pattern gas radiation detectors. Based on the properties of existing plasma display panels, we expect eventually to be able to build a sealed array of plasma discharge gas cells to detect ionizing radiation with fast rise time of less than 10ns and high spatial resolution using a pixel pitch of less than 100 micrometer. In this thesis I shall describe our program of testing plasma display panels as detectors, including simulations, design and the first laboratory and beam studies that demonstrate the detection of cosmic ray muons, beta rays and medium energy protons. The ATLAS detector is used to search for high-mass resonances, in particular heavy neutral gauge bosons (Z') and excited states of Kaluza-Klein γ/Z bosons decaying to an electron-positron pair or a muon-antimuon pair. Results are presented based ...

Reduction of ring artifacts in CBCT: Detection and correction of pixel gain variations in flat panel detectors

International Nuclear Information System (INIS)

Altunbas, Cem; Lai, Chao-Jen; Zhong, Yuncheng; Shaw, Chris C.

2014-01-01

Purpose: In using flat panel detectors (FPD) for cone beam computed tomography (CBCT), pixel gain variations may lead to structured nonuniformities in projections and ring artifacts in CBCT images. Such gain variations can be caused by change in detector entrance exposure levels or beam hardening, and they are not accounted by conventional flat field correction methods. In this work, the authors presented a method to identify isolated pixel clusters that exhibit gain variations and proposed a pixel gain correction (PGC) method to suppress both beam hardening and exposure level dependent gain variations. Methods: To modulate both beam spectrum and entrance exposure, flood field FPD projections were acquired using beam filters with varying thicknesses. “Ideal” pixel values were estimated by performing polynomial fits in both raw and flat field corrected projections. Residuals were calculated by taking the difference between measured and ideal pixel values to identify clustered image and FPD artifacts in flat field corrected and raw images, respectively. To correct clustered image artifacts, the ratio of ideal to measured pixel values in filtered images were utilized as pixel-specific gain correction factors, referred as PGC method, and they were tabulated as a function of pixel value in a look-up table. Results: 0.035% of detector pixels lead to clustered image artifacts in flat field corrected projections, where 80% of these pixels were traced back and linked to artifacts in the FPD. The performance of PGC method was tested in variety of imaging conditions and phantoms. The PGC method reduced clustered image artifacts and fixed pattern noise in projections, and ring artifacts in CBCT images. Conclusions: Clustered projection image artifacts that lead to ring artifacts in CBCT can be better identified with our artifact detection approach. When compared to the conventional flat field correction method, the proposed PGC method enables characterization of nonlinear

Resolution requirements for monitor viewing of digital flat-panel detector radiographs: a contrast detail analysis

International Nuclear Information System (INIS)

Peer, Siegfried; Giacomuzzi, Salvatore M.; Peer, Regina; Gassner, Eva; Steingruber, Iris; Jaschke, Werner

2003-01-01

With the introduction of digital flat-panel detector systems into clinical practice, the still unresolved question of resolution requirements for picture archiving communication system (PACS) workstation monitors has gained new momentum. This contrast detail analysis was thus performed to define the differences in observer performance in the detection of small low-contrast objects on clinical 1K and 2K monitor workstations. Images of the CDRAD 2.0 phantom were acquired at varying exposures on an indirect-type digital flat-panel detector. Three observers evaluated a total of 15 images each with respect to the threshold contrast for each detail size. The numbers of correctly identified objects were determined for all image subsets. No significant difference in the correct detection ratio was detected among the observers; however, the difference between the two types of workstations (1K vs 2K monitors) despite less than 3% was significant at a 95% confidence level. Slight but statistically significant differences exist in the detection of low-contrast nodular details visualized on 1K- and 2K-monitor workstations. Further work is needed to see if this result holds true also for comparison of clinical flat-panel detector images and may, for example, exert an influence on the diagnostic accuracy of chest X-ray readings. (orig.)

Development of CT and 3D-CT Using Flat Panel Detector Based Real-Time Digital Radiography System

International Nuclear Information System (INIS)

Ravindran, V. R.; Sreelakshmi, C.; Vibin

2008-01-01

The application of Digital Radiography in the Nondestructive Evaluation (NDE) of space vehicle components is a recent development in India. A Real-time DR system based on amorphous silicon Flat Panel Detector has been developed for the NDE of solid rocket motors at Rocket Propellant Plant of VSSC in a few years back. The technique has been successfully established for the nondestructive evaluation of solid rocket motors. The DR images recorded for a few solid rocket specimens are presented in the paper. The Real-time DR system is capable of generating sufficient digital X-ray image data with object rotation for the CT image reconstruction. In this paper the indigenous development of CT imaging based on the Realtime DR system for solid rocket motor is presented. Studies are also carried out to generate 3D-CT image from a set of adjacent CT images of the rocket motor. The capability of revealing the spatial location and characterisation of defect is demonstrated by the CT and 3D-CT images generated.

Development of X-ray detector based on phototransistor

International Nuclear Information System (INIS)

Ramacos Fardela; Kusminarto

2014-01-01

X-ray interaction with matter can produce phenomenon of fluorescence that emits visible light. This phenomenon has been exploited to design an X-ray detector based on photo transistor by attaching a screen ZnS(Ag) on the surface of the photo transistor which is arranged in a Darlington circuit. Response of detector was done by collimating of X-rays beam from the X-ray generator tube Philips 2000 watts, 60 kV type PW 2215/20 NR 780 026 and measure the detector output voltage (V out ). Varying the current by 5, 10, 15, 20, 25, 30, 35 and 40 mA in the X-ray panel. The experimental results showed that the Darlington circuit can be applied to design the detector of X-ray based on phototransistor. The results show that there is a linear relationship between the change in the intensity of X-ray detectors with voltage output phototransistor when it was closed with fluorescence materials ZnS(Ag), the linearity coefficient was R 2 = 0.99. Sensitivity of detector was obtained to be 3.7 x 10 -2 mV per cpm. (author)

Variation in X-ray dose quantity using an amorphous selenium based flat-panel detector - a study on the dose reduction rate up to the limit of diagnostical utilization

International Nuclear Information System (INIS)

Lehnert, T.; Wohlers, J.; Manegold, K.; Wetter, A.; Jacobi, V.; Mack, M.G.; Vogl, T.J.; Streng, W.

2006-01-01

Purpose: To evaluate the diagnostic quality and minimum required dose to obtain acceptable images for diagnostic purposes in the field of musculoskeletal radiology. Materials and methods: A critical comparison of the image quality produced by a novel flat panel detector and the conventional screen/film system using a contrast-detail phantom was performed in phase I. Images from both systems were obtained with the same dose and displayed with similar contrast and density. In phase II images of significant anatomical structures in cadaver extremities obtained using the digital detector system and the standard film/screen system were critically evaluated. After a successive reduction in the X-ray dose for 84 patients in phase III, eight independent radiologists compared the image quality of the screen/film system to that of the novel flat panel detector. Results: Phases I and II revealed a difference in the image quality achieved by the standard screen/film system and the digital detector system to the advantage of the digital detector system. In 77 of 84 patients (91.7%), phase III showed equal image quality after a 50% reduction in the X-ray dose. In 3 cases (3.6%) the image quality and the level of contrast were better. No unified statement could be made for 4 patients (4.7%). Conclusion: Digital imaging of skeletal disorders using the novel flat panel detector makes it possible to reduce the X-ray dose by 50% with equal or even better image quality. (orig.)

Clinical evaluation of digital angiographic system equipped with the Safire' flat-panel detector of a direct conversion type

International Nuclear Information System (INIS)

Miura, Yoshiaki; Miura, Yusuke; Goto, Keiichi

2003-01-01

This report presents a report on clinical evaluation of our newly developed flat-panel X-ray detector of a direct conversion type, designed to provide images of a resolution higher than, or at least equal to, that ensured by X-ray photographic films, in clinical digital X-ray cinematography. This new detector was named 'Safire' the acronym of 'Shimadzu advanced flat imaging receptor', emphasizing its high technological level, such as the capability to ensure high quality of images. The clinical evaluation of Shimadzu DIGITEX Premier digital angiography system, equipped with this new flat-panel X-ray detector of a direct conversion type, has been started in March, 2003, at the Kokura Memorial Hospital in Kyushu, Japan. (author)

Digital chest radiography with an amorphous silicon flat-panel-detector versus a storage-phosphor system: comparison of soft-copy images

International Nuclear Information System (INIS)

Lee, Hyun Ju; Im, Jung Gi; Goo, Jin Mo; Lee, Chang Hyun

2006-01-01

We compared the soft-copy images produced by an amorphous silicon flat-panel-detector system with the images produced by a storage-phosphor radiography system for their ability to visualize anatomic regions of the chest. Two chest radiologists independently analyzed 234 posteroanterior chest radiographs obtained from 78 patients on high-resolution liquid crystal display monitors (2560 x 2048 x 8 bits). In each patient, one radiograph was obtained with a storage-phosphor system, and two radiographs were obtained via amorphous silicon flat-panel-detector radiography with and without spatial frequency filtering. After randomizing the 234 images, the interpreters rated the visibility and radiographic quality of 11 different anatomic regions. Each image was ranked on a five-point scale (1 = not visualized, 2 = poor visualization, 3 = fair visualization, 4 = good visualization, and 5 = excellent visualization). The statistical difference between each system was determined using the Wilcoxon's signed rank test. The visibility of three anatomic regions (hilum, heart border and ribs), as determined by the chest radiologist with 14 years experience (ρ < 0.05) and the visibility of the thoracic spine, as determined by the chest radiologist with 8 years experience (ρ = 0.036), on the amorphous silicon flat-panel-detector radiography prior to spatial frequency filtering were significantly superior to that on the storage-phosphor radiography. The visibility of 11 anatomic regions, as determined by the chest radiologist with 14 years experience (ρ < 0.0001) and the visibility of five anatomic regions (unobscured lung, rib, proximal airway, thoracic spine and overall appearance), as determined by the chest radiologist with 8 years experience (ρ < 0.05), on the amorphous silicon flat-panel-detector radiography after spatial frequency filtering were significantly superior to that on the storage-phosphor radiography. The amorphous silicon flat-panel-detector system depicted the

A characteristic of angiographic cone-beam CT

International Nuclear Information System (INIS)

Takase, Tadashi; Take, Toshio; Nakazawa, Yasuo; Kinouchi, Katsunori

2009-01-01

Angiographic cone-beam CT, called DynaCT by SIEMENS, is a 3D imaging tool reconstructed from projection data by a rotational C-arm with a flat panel detector. It can visualize low-contrast objects such as soft tissue or small vessels as well as high-contrast structures such as enhanced vessels or bone. We need to understand its image characteristics and dose distribution during 200 degree rotation around a patient. In this research, we evaluated fundamental characteristics and dose effectiveness for optimized clinical images. DynaCT, including soft tissue information and isochronal voxel data along the z-axis, could provide enough CT-like image quality for interventional radiology (IVR) use. In addition, evaluation of accumulated dose distribution helped us to predict and avoid the occurrence of radiodermatitis. Thus, DynaCT is useful as a support and navigation tool for IVR. (author)

Cone-based Electrical Resistivity Tomography

Science.gov (United States)

Pidlisecky, A.; Knight, R.; Haber, E.

2005-05-01

Determining the 3D spatial distribution of subsurface properties is a critical part of managing the clean-up of contaminated sites. Most standard hydrologic methods sample small regions immediately adjacent to wells or testing devices. This provides data which are not representative of the entire region of interest. Furthermore, at many contaminated sites invasive methods are not acceptable, due to the risks associated with contacting and spreading the contaminants. To address these issues, we have developed a minimally invasive technology that provides information about the 3D distribution of electrical conductivity. This new technique, cone-based electrical resistivity tomography (C-bert), involves placing several permanent current electrodes in the subsurface and using electrodes mounted on a cone penetrometer to measure the resultant potential field while advancing the cone into the subsurface. In addition to potential field measurements, we obtain the standard suite of cone-penetration measurements, including high resolution resistivity logs; these data can then be used to constrain the inversion of the potential field data. A major challenge of working with these data is that the cone penetrometer is highly conductive, and thus presents a large local perturbation around the measurement location. As the cone is very small (approximately 30mm in diameter) with respect to the total model space, explicitly modeling the cone is computationally demanding. We developed a method for solving the forward model that reduces computational time by an order of magnitude. This solution method, iteratively determined boundary conditions, makes it possible to correct for the cone effect before inversion of the data. Results from synthetic experiments suggest that the C-bert method of data acquisition can result in high quality electrical conductivity images of the subsurface. We tested the practicality of this technique by performing a field test of the C-bert system to image

Evaluation of radiosurgery techniques–Cone-based linac radiosurgery vs tomotherapy-based radiosurgery

International Nuclear Information System (INIS)

Yip, Ho Yin; Mui, Wing Lun A.; Lee, Joseph W.Y.; Fung, Winky Wing Ki; Chan, Jocelyn M.T.; Chiu, G.; Law, Maria Y.Y.

2013-01-01

Performances of radiosurgery of intracranial lesions between cone-based Linac system and Tomotherapy-based system were compared in terms of dosimetry and time. Twelve patients with single intracranial lesion treated with cone-based Linac radiosurgery system from 2005 to 2009 were replanned for Tomotherapy-based radiosurgery treatment. The conformity index, homogeneity index (HI), and gradient score index (GSI) of each case was calculated. The Wilcoxon matched-pair test was used to compare the 3 indices between both systems. The cases with regular target (n = 6) and those with irregular target (n = 6) were further analyzed separately. The estimated treatment time between both systems was also compared. Significant differences were found in HI (p = 0.05) and in GSI (p = 0.03) for the whole group. Cone-based radiosurgery was better in GSI whereas Tomotherapy-based radiosurgery was better in HI. Cone-based radiosurgery was better in conformity index (p = 0.03) and GSI (p = 0.03) for regular targets, whereas Tomotherapy-based radiosurgery system performed significantly better in HI (p = 0.03) for irregular targets. The estimated total treatment time for Tomotherapy-based radiosurgery ranged from 24 minutes to 35 minutes, including 15 minutes of pretreatment megavoltage computed tomography (MVCT) and image registration, whereas that for cone-based radiosurgery ranged from 15 minutes for 1 isocenter to 75 minutes for 5 isocenters. As a rule of thumb, Tomotherapy-based radiosurgery system should be the first-line treatment for irregular lesions because of better dose homogeneity and shorter treatment time. Cone-based Linac radiosurgery system should be the treatment of choice for regular targets because of the better dose conformity, rapid dose fall-off, and reasonable treatment time

Evaluation of radiosurgery techniques–Cone-based linac radiosurgery vs tomotherapy-based radiosurgery

Energy Technology Data Exchange (ETDEWEB)

Yip, Ho Yin, E-mail: hoyinyip@yahoo.com.hk [Department of Radiotherapy, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong (China); Mui, Wing Lun A.; Lee, Joseph W.Y.; Fung, Winky Wing Ki; Chan, Jocelyn M.T.; Chiu, G. [Department of Radiotherapy, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong (China); Law, Maria Y.Y. [Medical Physics and Research Department, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong (China)

2013-07-01

Performances of radiosurgery of intracranial lesions between cone-based Linac system and Tomotherapy-based system were compared in terms of dosimetry and time. Twelve patients with single intracranial lesion treated with cone-based Linac radiosurgery system from 2005 to 2009 were replanned for Tomotherapy-based radiosurgery treatment. The conformity index, homogeneity index (HI), and gradient score index (GSI) of each case was calculated. The Wilcoxon matched-pair test was used to compare the 3 indices between both systems. The cases with regular target (n = 6) and those with irregular target (n = 6) were further analyzed separately. The estimated treatment time between both systems was also compared. Significant differences were found in HI (p = 0.05) and in GSI (p = 0.03) for the whole group. Cone-based radiosurgery was better in GSI whereas Tomotherapy-based radiosurgery was better in HI. Cone-based radiosurgery was better in conformity index (p = 0.03) and GSI (p = 0.03) for regular targets, whereas Tomotherapy-based radiosurgery system performed significantly better in HI (p = 0.03) for irregular targets. The estimated total treatment time for Tomotherapy-based radiosurgery ranged from 24 minutes to 35 minutes, including 15 minutes of pretreatment megavoltage computed tomography (MVCT) and image registration, whereas that for cone-based radiosurgery ranged from 15 minutes for 1 isocenter to 75 minutes for 5 isocenters. As a rule of thumb, Tomotherapy-based radiosurgery system should be the first-line treatment for irregular lesions because of better dose homogeneity and shorter treatment time. Cone-based Linac radiosurgery system should be the treatment of choice for regular targets because of the better dose conformity, rapid dose fall-off, and reasonable treatment time.

Internal Reflection Sensor for the Cone Penetrometer. Innovative Technology Summary Report

International Nuclear Information System (INIS)

None

2001-01-01

The Internal Reflection Sensor, developed by EIC Laboratories, Inc. as a cone penetrometer based technology, provides real-time detection of subsurface non-aqueous phase liquids (NAPLs). The internal reflection element is positioned against the wall of the cone penetrometer probe such that its sensing face is in contact with the soil or groundwater as the cone is pushed into the subsurface. When NAPL is present and in contact with the sensing face, the internally reflected light is diminished. This results in a decrease in the signal output by the detector - a positive indicator of NAPL presence

Evaluation the image obtained from X-ray flat-panel detectors utilizing a polycrystalline CdZnTe film as the conversion layer

International Nuclear Information System (INIS)

Tokuda, S.; Kishihara, H.; Kaino, M.; Sato, T.

2006-01-01

We can expect that fluoroscopic images with a high sensitivity and excellent detective efficiency can be obtained by using a semiconductor with a small W factor for the conversion layer of X-ray flat-panel detectors, which have experienced a rapid gain inpopularity for medical and non-destructive industrial inspection uses in recent years. We believe that polycrystalline CdZnTe film formed by the closed spaced sublimation (CSS) method is a promising conversion material for next-generation high efficiency X-ray flat-panel detectors, and have previously reported the results of feasibility studies. In this paper, we present an overview of X-ray flat-panel detectors and the features of CdZnTe film, then we describe the CSS method of deposition and evaluation of the physical characteristics of CdZnTe film, and finally we present the results of our fabrication and testing of proto-type detectors utilizing CdZnTe film. (author)

Bowtie filter and water calibration in the improvement of cone beam CT image quality

International Nuclear Information System (INIS)

Li Minghui; Dai Jianrong; Zhang Ke

2010-01-01

Objective: To evaluate the improvement of cone beam CT (CBCT) image quality by using bewtie filter (F 1 ) and water calibration. Methods: First the multi-level gain calibration of the detector panel with the method of Cal 2 calibration was performed, and the CT images of CATPHAN503 with F 0 and bowtie filter were collected, respectively. Then the detector panel using water calibration kit was calibrated, and images were acquired again. Finally, the change of image quality after using F 1 and (or) water calibration method was observed. The observed indexes included low contrast visibility, spatial uniformity, ring artifact, spatial resolution and geometric accuracy. Results: Comparing with the traditional combination of F 0 filter and Cal 2 calibration, the combination of bowtie filter F 1 and water calibration improves low contrast visibility by 13.71%, and spatial uniformity by 54. 42%. Water calibration removes ring artifacts effectively. However, none of them improves spatial resolution and geometric accuracy. Conclusions: The combination of F 1 and water calibration improves CBCT image quality effectively. This improvement is aid to the registration of CBCT images and localization images. (authors)

An optimization-based method for geometrical calibration in cone-beam CT without dedicated phantoms

International Nuclear Information System (INIS)

Panetta, D; Belcari, N; Guerra, A Del; Moehrs, S

2008-01-01

In this paper we present a new method for the determination of geometrical misalignments in cone-beam CT scanners, from the analysis of the projection data of a generic object. No a priori knowledge of the object shape and positioning is required. We show that a cost function, which depends on the misalignment parameters, can be defined using the projection data and that such a cost function has a local minimum in correspondence to the actual parameters of the system. Hence, the calibration of the scanner can be carried out by minimizing the cost function using standard optimization techniques. The method is developed for a particular class of 3D object functions, for which the redundancy of the fan beam sinogram in the transaxial midplane can be extended to cone-beam projection data, even at wide cone angles. The method has an approximated validity for objects which do not belong to that class; in that case, a suitable subset of the projection data can be selected in order to compute the cost function. We show by numerical simulations that our method is capable to determine with high accuracy the most critical misalignment parameters of the scanner, i.e., the transversal shift and the skew of the detector. Additionally, the detector slant can be determined. Other parameters such as the detector tilt, the longitudinal shift and the error in the source-detector distance cannot be determined with our method, as the proposed cost function has a very weak dependence on them. However, due to the negligible influence of these latter parameters in the reconstructed image quality, they can be kept fixed at estimated values in both calibration and reconstruction processes without compromising the final result. A trade-off between computational cost and calibration accuracy must be considered when choosing the data subset used for the computation of the cost function. Results on real data of a mouse femur as obtained with a small animal micro-CT are shown as well, proving

Calibration model of a dual gain flat panel detector for 2D and 3D x-ray imaging

International Nuclear Information System (INIS)

Schmidgunst, C.; Ritter, D.; Lang, E.

2007-01-01

The continuing research and further development in flat panel detector technology have led to its integration into more and more medical x-ray systems for two-dimensional (2D) and three-dimensional (3D) imaging, such as fixed or mobile C arms. Besides the obvious advantages of flat panel detectors, like the slim design and the resulting optimum accessibility to the patient, their success is primarily a product of the image quality that can be achieved. The benefits in the physical and performance-related features as opposed to conventional image intensifier systems (e.g., distortion-free reproduction of imaging information or almost linear signal response over a large dynamic range) can be fully exploited, however, only if the raw detector images are correctly calibrated and postprocessed. Previous procedures for processing raw data contain idealizations that, in the real world, lead to artifacts or losses in image quality. Thus, for example, temperature dependencies or changes in beam geometry, as can occur with mobile C arm systems, have not been taken into account up to this time. Additionally, adverse characteristics such as image lag or aging effects have to be compensated to attain the best possible image quality. In this article a procedure is presented that takes into account the important dependencies of the individual pixel sensitivity of flat panel detectors used in 2D or 3D imaging and simultaneously minimizes the work required for an extensive recalibration. It is suitable for conventional detectors with only one gain mode as well as for the detectors specially developed for 3D imaging with dual gain read-out technology

Accurate technique for complete geometric calibration of cone-beam computed tomography systems

International Nuclear Information System (INIS)

Cho Youngbin; Moseley, Douglas J.; Siewerdsen, Jeffrey H.; Jaffray, David A.

2005-01-01

Cone-beam computed tomography systems have been developed to provide in situ imaging for the purpose of guiding radiation therapy. Clinical systems have been constructed using this approach, a clinical linear accelerator (Elekta Synergy RP) and an iso-centric C-arm. Geometric calibration involves the estimation of a set of parameters that describes the geometry of such systems, and is essential for accurate image reconstruction. We have developed a general analytic algorithm and corresponding calibration phantom for estimating these geometric parameters in cone-beam computed tomography (CT) systems. The performance of the calibration algorithm is evaluated and its application is discussed. The algorithm makes use of a calibration phantom to estimate the geometric parameters of the system. The phantom consists of 24 steel ball bearings (BBs) in a known geometry. Twelve BBs are spaced evenly at 30 deg in two plane-parallel circles separated by a given distance along the tube axis. The detector (e.g., a flat panel detector) is assumed to have no spatial distortion. The method estimates geometric parameters including the position of the x-ray source, position, and rotation of the detector, and gantry angle, and can describe complex source-detector trajectories. The accuracy and sensitivity of the calibration algorithm was analyzed. The calibration algorithm estimates geometric parameters in a high level of accuracy such that the quality of CT reconstruction is not degraded by the error of estimation. Sensitivity analysis shows uncertainty of 0.01 deg. (around beam direction) to 0.3 deg. (normal to the beam direction) in rotation, and 0.2 mm (orthogonal to the beam direction) to 4.9 mm (beam direction) in position for the medical linear accelerator geometry. Experimental measurements using a laboratory bench Cone-beam CT system of known geometry demonstrate the sensitivity of the method in detecting small changes in the imaging geometry with an uncertainty of 0.1 mm in

Clinical evaluation of digital angiographic system equipped with the Safire' flat-panel detector of a direct conversion type

Energy Technology Data Exchange (ETDEWEB)

Miura, Yoshiaki; Miura, Yusuke; Goto, Keiichi [Shimadzu Corporation, Medical Systems Division, Research and Development, Kyoto (JP)] [and others

2003-06-01

This report presents a report on clinical evaluation of our newly developed flat-panel X-ray detector of a direct conversion type, designed to provide images of a resolution higher than, or at least equal to, that ensured by X-ray photographic films, in clinical digital X-ray cinematography. This new detector was named 'Safire' the acronym of 'Shimadzu advanced flat imaging receptor', emphasizing its high technological level, such as the capability to ensure high quality of images. The clinical evaluation of Shimadzu DIGITEX Premier digital angiography system, equipped with this new flat-panel X-ray detector of a direct conversion type, has been started in March, 2003, at the Kokura Memorial Hospital in Kyushu, Japan. (author)

Dual resolution cone beam breast CT: A feasibility study

International Nuclear Information System (INIS)

Chen Lingyun; Shen Youtao; Lai, Chao-Jen; Han Tao; Zhong Yuncheng; Ge Shuaiping; Liu Xinming; Wang Tianpeng; Yang, Wei T.; Whitman, Gary J.; Shaw, Chris C.

2009-01-01

Purpose: In this study, the authors investigated the feasibility of a dual resolution volume-of-interest (VOI) cone beam breast CT technique and compared two implementation approaches in terms of dose saving and scatter reduction. Methods: With this technique, a lead VOI mask with an opening is inserted between the x-ray source and the breast to deliver x-ray exposure to the VOI while blocking x rays outside the VOI. A CCD detector is used to collect the high resolution projection data of the VOI. Low resolution cone beam CT (CBCT) images of the entire breast, acquired with a flat panel (FP) detector, were used to calculate the projection data outside the VOI with the ray-tracing reprojection method. The Feldkamp-Davis-Kress filtered backprojection algorithm was used to reconstruct the dual resolution 3D images. Breast phantoms with 180 μm and smaller microcalcifications (MCs) were imaged with both FP and FP-CCD dual resolution CBCT systems, respectively. Two approaches of implementing the dual resolution technique, breast-centered approach and VOI-centered approach, were investigated and evaluated for dose saving and scatter reduction with Monte Carlo simulation using a GEANT4 package. Results: The results showed that the breast-centered approach saved more breast absorbed dose than did VOI-centered approach with similar scatter reduction. The MCs in fatty breast phantom, which were invisible with FP CBCT scan, became visible with the FP-CCD dual resolution CBCT scan. Conclusions: These results indicate potential improvement of the image quality inside the VOI with reduced breast dose both inside and outside the VOI.

The design and imaging characteristics of dynamic, solid-state, flat-panel x-ray image detectors for digital fluoroscopy and fluorography

International Nuclear Information System (INIS)

Cowen, A.R.; Davies, A.G.; Sivananthan, M.U.

2008-01-01

Dynamic, flat-panel, solid-state, x-ray image detectors for use in digital fluoroscopy and fluorography emerged at the turn of the millennium. This new generation of dynamic detectors utilize a thin layer of x-ray absorptive material superimposed upon an electronic active matrix array fabricated in a film of hydrogenated amorphous silicon (a-Si:H). Dynamic solid-state detectors come in two basic designs, the indirect-conversion (x-ray scintillator based) and the direct-conversion (x-ray photoconductor based). This review explains the underlying principles and enabling technologies associated with these detector designs, and evaluates their physical imaging characteristics, comparing their performance against the long established x-ray image intensifier television (TV) system. Solid-state detectors afford a number of physical imaging benefits compared with the latter. These include zero geometrical distortion and vignetting, immunity from blooming at exposure highlights and negligible contrast loss (due to internal scatter). They also exhibit a wider dynamic range and maintain higher spatial resolution when imaging over larger fields of view. The detective quantum efficiency of indirect-conversion, dynamic, solid-state detectors is superior to that of both x-ray image intensifier TV systems and direct-conversion detectors. Dynamic solid-state detectors are playing a burgeoning role in fluoroscopy-guided diagnosis and intervention, leading to the displacement of x-ray image intensifier TV-based systems. Future trends in dynamic, solid-state, digital fluoroscopy detectors are also briefly considered. These include the growth in associated three-dimensional (3D) visualization techniques and potential improvements in dynamic detector design

SimDoseCT: dose reporting software based on Monte Carlo simulation for a 320 detector-row cone-beam CT scanner and ICRP computational adult phantoms

Science.gov (United States)

Cros, Maria; Joemai, Raoul M. S.; Geleijns, Jacob; Molina, Diego; Salvadó, Marçal

2017-08-01

This study aims to develop and test software for assessing and reporting doses for standard patients undergoing computed tomography (CT) examinations in a 320 detector-row cone-beam scanner. The software, called SimDoseCT, is based on the Monte Carlo (MC) simulation code, which was developed to calculate organ doses and effective doses in ICRP anthropomorphic adult reference computational phantoms for acquisitions with the Aquilion ONE CT scanner (Toshiba). MC simulation was validated by comparing CTDI measurements within standard CT dose phantoms with results from simulation under the same conditions. SimDoseCT consists of a graphical user interface connected to a MySQL database, which contains the look-up-tables that were generated with MC simulations for volumetric acquisitions at different scan positions along the phantom using any tube voltage, bow tie filter, focal spot and nine different beam widths. Two different methods were developed to estimate organ doses and effective doses from acquisitions using other available beam widths in the scanner. A correction factor was used to estimate doses in helical acquisitions. Hence, the user can select any available protocol in the Aquilion ONE scanner for a standard adult male or female and obtain the dose results through the software interface. Agreement within 9% between CTDI measurements and simulations allowed the validation of the MC program. Additionally, the algorithm for dose reporting in SimDoseCT was validated by comparing dose results from this tool with those obtained from MC simulations for three volumetric acquisitions (head, thorax and abdomen). The comparison was repeated using eight different collimations and also for another collimation in a helical abdomen examination. The results showed differences of 0.1 mSv or less for absolute dose in most organs and also in the effective dose calculation. The software provides a suitable tool for dose assessment in standard adult patients undergoing CT

Flat-panel detectors: how much better are they?

International Nuclear Information System (INIS)

Seibert, J.A.

2006-01-01

Interventional and fluoroscopic imaging procedures for pediatric patients are becoming more prevalent because of the less-invasive nature of these procedures compared to alternatives such as surgery. Flat-panel X-ray detectors (FPD) for fluoroscopy are a new technology alternative to the image intensifier/TV (II/TV) digital system that has been in use for more than two decades. Two major FPD technologies have been implemented, based on indirect conversion of X-rays to light (using an X-ray scintillator) and then to proportional charge (using a photodiode), or direct conversion of X-rays into charge (using a semiconductor material) for signal acquisition and digitization. These detectors have proved very successful for high-exposure interventional procedures but lack the image quality of the II/TV system at the lowest exposure levels common in fluoroscopy. The benefits for FPD image quality include lack of geometric distortion, little or no veiling glare, a uniform response across the field-of-view, and improved ergonomics with better patient access. Better detective quantum efficiency indicates the possibility of reducing the patient dose in accordance with ALARA principles. However, first-generation FPD devices have been implemented with less than adequate acquisition flexibility (e.g., lack of tableside controls/information, inability to easily change protocols) and the presence of residual signals from previous exposures, and additional cost of equipment and long-term maintenance have been serious impediments to purchase and implementation. Technological advances of second generation and future hybrid FPD systems should solve many current issues. The answer to the question ''how much better are they?'' is ''significantly better'', and they are certainly worth consideration for replacement or new implementation of an imaging suite for pediatric fluoroscopy. (orig.)

Feasibility study of flexible flat-panel X-ray detectors for digital radiography

International Nuclear Information System (INIS)

Joe, Ok La; Yun, Seung Man; Kim, Ho Kyung

2010-01-01

Flexible flat-panel detectors (FPDs), which utilize both organic photodiode (OPD) and organic thin-film transistor (OTFT) technologies, are recently concerned in digital radiography. The flexible FPD has several potential advantages, such as high accessibility to patient, avoidance of geometrical burr due to the oblique angle incidence of X-ray, great reduction in manufacturing cost due to jet-printing. At once, The OPD/OTFT arrays were fabricated by jet-printing techniques, mechanical robustness due to plastic substrates, and so on. In this study, we have investigated the feasibility of flexible FPD by comparing theoretical detective quantum efficiency (DQE) with that of the conventional amorphous silicon-based FPD. We chose copper phthalocyanine-fullerene (CuPc-C60) organic materials for the construction of the flexible FPD. DQE was calculated by the linear-systems transfer theory

Development of high quantum efficiency, flat panel, thick detectors for megavoltage x-ray imaging: An experimental study of a single-pixel prototype

International Nuclear Information System (INIS)

Mei, X.; Pang, G.

2005-01-01

Our overall goal is to develop a new generation of electronic portal imaging devices (EPIDs) with a quantum efficiency (QE) more than an order of magnitude higher and a spatial resolution equivalent to that of EPIDs currently used for portal imaging. A novel design of such a high QE flat-panel based EPID was introduced recently and its feasibility was investigated theoretically [see Pang and Rowlands, Med. Phys. 31, 3004 (2004)]. In this work, we constructed a prototype single-pixel detector based on the novel design. Some fundamental imaging properties including the QE, spatial resolution, and sensitivity of the prototype detector were measured with a 6 MV beam. It has been shown that the experimental results agree well with theoretical predictions and further development based on the novel design including the construction of a prototype area detector is warranted

Modeling and evaluation of a high-resolution CMOS detector for cone-beam CT of the extremities.

Science.gov (United States)

Cao, Qian; Sisniega, Alejandro; Brehler, Michael; Stayman, J Webster; Yorkston, John; Siewerdsen, Jeffrey H; Zbijewski, Wojciech

2018-01-01

Quantitative assessment of trabecular bone microarchitecture in extremity cone-beam CT (CBCT) would benefit from the high spatial resolution, low electronic noise, and fast scan time provided by complementary metal-oxide semiconductor (CMOS) x-ray detectors. We investigate the performance of CMOS sensors in extremity CBCT, in particular with respect to potential advantages of thin (CMOS x-ray detector incorporating the effects of CsI:Tl scintillator thickness was developed. Simulation studies were performed using nominal extremity CBCT acquisition protocols (90 kVp, 0.126 mAs/projection). A range of scintillator thickness (0.35-0.75 mm), pixel size (0.05-0.4 mm), focal spot size (0.05-0.7 mm), magnification (1.1-2.1), and dose (15-40 mGy) was considered. The detectability index was evaluated for both CMOS and a-Si:H flat-panel detector (FPD) configurations for a range of imaging tasks emphasizing spatial frequencies associated with feature size aobj. Experimental validation was performed on a CBCT test bench in the geometry of a compact orthopedic CBCT system (SAD = 43.1 cm, SDD = 56.0 cm, matching that of the Carestream OnSight 3D system). The test-bench studies involved a 0.3 mm focal spot x-ray source and two CMOS detectors (Dalsa Xineos-3030HR, 0.099 mm pixel pitch) - one with the standard CsI:Tl thickness of 0.7 mm (C700) and one with a custom 0.4 mm thick scintillator (C400). Measurements of modulation transfer function (MTF), detective quantum efficiency (DQE), and CBCT scans of a cadaveric knee (15 mGy) were obtained for each detector. Optimal detectability for high-frequency tasks (feature size of ~0.06 mm, consistent with the size of trabeculae) was ~4× for the C700 CMOS detector compared to the a-Si:H FPD at nominal system geometry of extremity CBCT. This is due to ~5× lower electronic noise of a CMOS sensor, which enables input quantum-limited imaging at smaller pixel size. Optimal pixel size for high-frequency tasks was CMOS

Cardiac cone-beam CT

International Nuclear Information System (INIS)

Manzke, Robert

2005-01-01

This doctoral thesis addresses imaging of the heart with retrospectively gated helical cone-beam computed tomography (CT). A thorough review of the CT reconstruction literature is presented in combination with a historic overview of cardiac CT imaging and a brief introduction to other cardiac imaging modalities. The thesis includes a comprehensive chapter about the theory of CT reconstruction, familiarizing the reader with the problem of cone-beam reconstruction. The anatomic and dynamic properties of the heart are outlined and techniques to derive the gating information are reviewed. With the extended cardiac reconstruction (ECR) framework, a new approach is presented for the heart-rate-adaptive gated helical cardiac cone-beam CT reconstruction. Reconstruction assessment criteria such as the temporal resolution, the homogeneity in terms of the cardiac phase, and the smoothness at cycle-to-cycle transitions are developed. Several reconstruction optimization approaches are described: An approach for the heart-rate-adaptive optimization of the temporal resolution is presented. Streak artifacts at cycle-to-cycle transitions can be minimized by using an improved cardiac weighting scheme. The optimal quiescent cardiac phase for the reconstruction can be determined automatically with the motion map technique. Results for all optimization procedures applied to ECR are presented and discussed based on patient and phantom data. The ECR algorithm is analyzed for larger detector arrays of future cone-beam systems throughout an extensive simulation study based on a four-dimensional cardiac CT phantom. The results of the scientific work are summarized and an outlook proposing future directions is given. The presented thesis is available for public download at www.cardiac-ct.net

Comparison of dose and image quality of a Flat-panel detector and an image intensifier

International Nuclear Information System (INIS)

Lazzaro, M.; Friedrich, B.Q.; Luz, R.M. da; Silva, A.M.M. da

2016-01-01

With the development of new technologies, have emerged new conversion methods of X-ray image, such as flat panel detectors. The aim of this work is the comparison of entrance surface air kerma (ESAK) and image quality between an image intensifier type of detector (A) and a flat panel (B). The ESAK was obtained by placing a ionization chamber under PMMA simulators of 10, 20 and 30 cm and the image quality was obtained by using the TOR "1"8FG simulator. The ESAK to the equipment A is higher when compared to the equipment B. The high contrast resolution is better for the equipment A for all thicknesses of simulators. The equipment A has low contrast resolution with a better viewing threshold for thicknesses of 10 and 20 cm, and a worse performance for 30 cm. It is concluded that the equipment B has ESAK smaller and despite having lower resolution, in almost all cases, have appropriate image quality for diagnosis. (author)

Contrast-detail analysis of three flat panel detectors for digital radiography

International Nuclear Information System (INIS)

Borasi, Giovanni; Samei, Ehsan; Bertolini, Marco; Nitrosi, Andrea; Tassoni, Davide

2006-01-01

In this paper we performed a contrast detail analysis of three commercially available flat panel detectors, two based on the indirect detection mechanism (GE Revolution XQ/i, system A, and Trixell/Philips Pixium 4600, system B) and one based on the direct detection mechanism (Hologic DirectRay DR 1000, system C). The experiment was conducted using standard x-ray radiation quality and a widely used contrast-detail phantom. Images were evaluated using a four alternative forced choice paradigm on a diagnostic-quality softcopy monitor. At the low and intermediate exposures, systems A and B gave equivalent performances. At the high dose levels, system A performed better than system B in the entire range of target sizes, even though the pixel size of system A was about 40% larger than that of system B. At all the dose levels, the performances of the system C (direct system) were lower than those of system A and B (indirect systems). Theoretical analyses based on the Perception Statistical Model gave similar predicted SNR T values corresponding to an observer efficiency of about 0.08 for systems A and B and 0.05 for system C

SU-D-206-06: Task-Specific Optimization of Scintillator Thickness for CMOS-Detector Based Cone-Beam Breast CT

Energy Technology Data Exchange (ETDEWEB)

Vedantham, S; Shrestha, S; Shi, L; Vijayaraghavan, G; Karellas, A [University of Massachusetts Medical School, Worcester, MA (United States)

2016-06-15

Purpose: To optimize the cesium iodide (CsI:Tl) scintillator thickness in a complimentary metal-oxide semiconductor (CMOS)-based detector for use in dedicated cone-beam breast CT. Methods: The imaging task considered was the detection of a microcalcification cluster comprising six 220µm diameter calcium carbonate spheres, arranged in the form of a regular pentagon with 2 mm spacing on its sides and a central calcification, similar to that in ACR-recommended mammography accreditation phantom, at a mean glandular dose of 4.5 mGy. Generalized parallel-cascades based linear systems analysis was used to determine Fourier-domain image quality metrics in reconstructed object space, from which the detectability index inclusive of anatomical noise was determined for a non-prewhitening numerical observer. For 300 projections over 2π, magnification-associated focal-spot blur, Monte Carlo derived x-ray scatter, K-fluorescent emission and reabsorption within CsI:Tl, CsI:Tl quantum efficiency and optical blur, fiberoptic plate transmission efficiency and blur, CMOS quantum efficiency, pixel aperture function and additive noise, and filtered back-projection to isotropic 105µm voxel pitch with bilinear interpolation were modeled. Imaging geometry of a clinical prototype breast CT system, a 60 kV Cu/Al filtered x-ray spectrum from 0.3 mm focal spot incident on a 14 cm diameter semi-ellipsoidal breast were used to determine the detectability index for 300–600 µm thick (75µm increments) CsI:Tl. The CsI:Tl thickness that maximized the detectability index was considered optimal. Results: The limiting resolution (10% modulation transfer function, MTF) progressively decreased with increasing CsI:Tl thickness. The zero-frequency detective quantum efficiency, DQE(0), in projection space increased with increasing CsI:Tl thickness. The maximum detectability index was achieved with 525µm thick CsI:Tl scintillator. Reduced MTF at mid-to-high frequencies for 600µm thick CsI:Tl lowered

Radiation exposure to operating staff during rotational flat-panel angiography and C-arm cone beam computed tomography (CT) applications

Energy Technology Data Exchange (ETDEWEB)

Schulz, Boris, E-mail: boris.schell@googlemail.com [Goethe University Hospital, Department of Diagnostic and Interventional Radiology, Theodor-Stern-Kai 7, 60590 Frankfurt (Germany); Heidenreich, Ralf, E-mail: ralf.heidenreich@roentgen-consult.de [Röntgen-Consult Company, Schulhausstrasse 37, 79199 Kirchzarten (Germany); Heidenreich, Monika, E-mail: info@roentgen-consult.de [Röntgen-Consult Company, Schulhausstrasse 37, 79199 Kirchzarten (Germany); Eichler, Katrin, E-mail: k.eichler@em.uni-frankfurt.de [Goethe University Hospital, Department of Diagnostic and Interventional Radiology, Theodor-Stern-Kai 7, 60590 Frankfurt (Germany); Thalhammer, Axel, E-mail: axel.thalhammer@kgu.de [Goethe University Hospital, Department of Diagnostic and Interventional Radiology, Theodor-Stern-Kai 7, 60590 Frankfurt (Germany); Naeem, Naguib Nagy Naguib, E-mail: nagynnn@yahoo.com [Goethe University Hospital, Department of Diagnostic and Interventional Radiology, Theodor-Stern-Kai 7, 60590 Frankfurt (Germany); Vogl, Thomas Josef, E-mail: T.Vogl@em.uni-frankfurt.de [Goethe University Hospital, Department of Diagnostic and Interventional Radiology, Theodor-Stern-Kai 7, 60590 Frankfurt (Germany); Zangos, Stefan, E-mail: Zangos@em.uni-frankfurt.de [Goethe University Hospital, Department of Diagnostic and Interventional Radiology, Theodor-Stern-Kai 7, 60590 Frankfurt (Germany)

2012-12-15

Purpose: To evaluate the radiation exposure for operating personel associated with rotational flat-panel angiography and C-arm cone beam CT. Materials and methods: Using a dedicated angiography-suite, 2D and 3D examinations of the liver were performed on a phantom to generate scattered radiation. Exposure was measured with a dosimeter at predefined heights (eye, thyroid, breast, gonads and knee) at the physician's location. Analysis included 3D procedures with a field of view (FOV) of 24 cm × 18 cm (8 s/rotation, 20 s/rotation and 5 s/2 rotations), and 47 cm × 18 cm (16 s/2 rotations) and standard 2D angiography (10 s, FOV 24 cm × 18 cm). Results: Measurements showed the highest radiation dose at the eye and thyroid level. In comparison to 2D-DSA (3.9 μSv eye-exposure), the 3D procedures caused an increased radiation exposure both in standard FOV (8 s/rotation: 28.0 μSv, 20 s/rotation: 79.3 μSv, 5 s/2 rotations: 32.5 μSv) and large FOV (37.6 μSv). Proportional distributions were measured for the residual heights. With the use of lead glass, irradiation of the eye lens was reduced to 0.2 μSv (2D DSA) and 10.6 μSv (3D technique with 20 s/rotation). Conclusion: Rotational flat-panel angiography and C-arm cone beam applications significantly increase radiation exposure to the attending operator in comparison to 2D angiography. Our study indicates that the physician should wear protective devices and leave the examination room when performing 3D examinations.

Radiation exposure to operating staff during rotational flat-panel angiography and C-arm cone beam computed tomography (CT) applications.

Science.gov (United States)

Schulz, Boris; Heidenreich, Ralf; Heidenreich, Monika; Eichler, Katrin; Thalhammer, Axel; Naeem, Naguib Nagy Naguib; Vogl, Thomas Josef; Zangos, Stefan

2012-12-01

To evaluate the radiation exposure for operating personnel associated with rotational flat-panel angiography and C-arm cone beam CT. Using a dedicated angiography-suite, 2D and 3D examinations of the liver were performed on a phantom to generate scattered radiation. Exposure was measured with a dosimeter at predefined heights (eye, thyroid, breast, gonads and knee) at the physician's location. Analysis included 3D procedures with a field of view (FOV) of 24 cm × 18 cm (8s/rotation, 20s/rotation and 5s/2 rotations), and 47 cm×18 cm (16s/2 rotations) and standard 2D angiography (10s, FOV 24 cm×18 cm). Measurements showed the highest radiation dose at the eye and thyroid level. In comparison to 2D-DSA (3.9 μSv eye-exposure), the 3D procedures caused an increased radiation exposure both in standard FOV (8s/rotation: 28.0 μSv, 20s/rotation: 79.3 μSv, 5s/2 rotations: 32.5 μSv) and large FOV (37.6 μSv). Proportional distributions were measured for the residual heights. With the use of lead glass, irradiation of the eye lens was reduced to 0.2 μSv (2D DSA) and 10.6 μSv (3D technique with 20s/rotation). Rotational flat-panel angiography and C-arm cone beam applications significantly increase radiation exposure to the attending operator in comparison to 2D angiography. Our study indicates that the physician should wear protective devices and leave the examination room when performing 3D examinations. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Radiation exposure to operating staff during rotational flat-panel angiography and C-arm cone beam computed tomography (CT) applications

International Nuclear Information System (INIS)

Schulz, Boris; Heidenreich, Ralf; Heidenreich, Monika; Eichler, Katrin; Thalhammer, Axel; Naeem, Naguib Nagy Naguib; Vogl, Thomas Josef; Zangos, Stefan

2012-01-01

Purpose: To evaluate the radiation exposure for operating personel associated with rotational flat-panel angiography and C-arm cone beam CT. Materials and methods: Using a dedicated angiography-suite, 2D and 3D examinations of the liver were performed on a phantom to generate scattered radiation. Exposure was measured with a dosimeter at predefined heights (eye, thyroid, breast, gonads and knee) at the physician's location. Analysis included 3D procedures with a field of view (FOV) of 24 cm × 18 cm (8 s/rotation, 20 s/rotation and 5 s/2 rotations), and 47 cm × 18 cm (16 s/2 rotations) and standard 2D angiography (10 s, FOV 24 cm × 18 cm). Results: Measurements showed the highest radiation dose at the eye and thyroid level. In comparison to 2D-DSA (3.9 μSv eye-exposure), the 3D procedures caused an increased radiation exposure both in standard FOV (8 s/rotation: 28.0 μSv, 20 s/rotation: 79.3 μSv, 5 s/2 rotations: 32.5 μSv) and large FOV (37.6 μSv). Proportional distributions were measured for the residual heights. With the use of lead glass, irradiation of the eye lens was reduced to 0.2 μSv (2D DSA) and 10.6 μSv (3D technique with 20 s/rotation). Conclusion: Rotational flat-panel angiography and C-arm cone beam applications significantly increase radiation exposure to the attending operator in comparison to 2D angiography. Our study indicates that the physician should wear protective devices and leave the examination room when performing 3D examinations.

Volume CT with a flat-panel detector on a mobile, isocentric C-arm: Pre-clinical investigation in guidance of minimally invasive surgery

International Nuclear Information System (INIS)

Siewerdsen, J.H.; Moseley, D.J.; Burch, S.; Bisland, S.K.; Bogaards, A.; Wilson, B.C.; Jaffray, D.A.

2005-01-01

A mobile isocentric C-arm (Siemens PowerMobil) has been modified in our laboratory to include a large area flat-panel detector (in place of the x-ray image intensifier), providing multi-mode fluoroscopy and cone-beam computed tomography (CT) imaging capability. This platform represents a promising technology for minimally invasive, image-guided surgical procedures where precision in the placement of interventional tools with respect to bony and soft-tissue structures is critical. The image quality and performance in surgical guidance was investigated in pre-clinical evaluation in image-guided spinal surgery. The control, acquisition, and reconstruction system are described. The reproducibility of geometric calibration, essential to achieving high three-dimensional (3D) image quality, is tested over extended time scales (7 months) and across a broad range in C-arm angulation (up to 45 deg.), quantifying the effect of improper calibration on spatial resolution, soft-tissue visibility, and image artifacts. Phantom studies were performed to investigate the precision of 3D localization (viz., fiber optic probes within a vertebral body) and effect of lateral projection truncation (limited field of view) on soft-tissue detectability in image reconstructions. Pre-clinical investigation was undertaken in a specific spinal procedure (photodynamic therapy of spinal metastases) in five animal subjects (pigs). In each procedure, placement of fiber optic catheters in two vertebrae (L1 and L2) was guided by fluoroscopy and cone-beam CT. Experience across five procedures is reported, focusing on 3D image quality, the effects of respiratory motion, limited field of view, reconstruction filter, and imaging dose. Overall, the intraoperative cone-beam CT images were sufficient for guidance of needles and catheters with respect to bony anatomy and improved surgical performance and confidence through 3D visualization and verification of transpedicular trajectories and tool placement

Cone-beam tomography with discrete data sets

International Nuclear Information System (INIS)

Barrett, H.H.

1994-01-01

Sufficiently conditions for cone-beam data are well known for the case of continuous data collection along a cone-vortex curve with continuous detectors. These continuous conditions are inadequate for real-world data where discrete vertex geometries and discrete detector arrays are used. In this paper we present a theoretical formulation of cone-beam tomography with arbitrary discrete arrays of detectors and vertices. The theory models the imaging system as a linear continuous-to-discrete mapping and represents the continuous object exactly as a Fourier series. The reconstruction problem is posed as the estimation of some subset of the Fourier coefficients. The main goal of the theory is to determine which Fourier coefficients can be reliably determined from the data delivered by a specific discrete design. A fourier component will be well determined by the data if it satisfies two conditions: it makes a strong contribution to the data, and this contribution is relatively independent of the contribution of other Fourier components. To make these considerations precise, we introduce a concept called the cross-talk matrix. A diagonal element of this matrix measures the strength of a Fourier component in the data, while an off-diagonal element quantifies the dependence or aliasing of two different components. (Author)

Evaluation of a cone beam computed tomography geometry for image guided small animal irradiation

International Nuclear Information System (INIS)

Yang, Yidong; Armour, Michael; Wang, Ken Kang-Hsin; Gandhi, Nishant; Wong, John; Iordachita, Iulian; Siewerdsen, Jeffrey

2015-01-01

The conventional imaging geometry for small animal cone beam computed tomography (CBCT) is that a detector panel rotates around the head-to-tail axis of an imaged animal (‘tubular’ geometry). Another unusual but possible imaging geometry is that the detector panel rotates around the anterior-to-posterior axis of the animal (‘pancake’ geometry). The small animal radiation research platform developed at Johns Hopkins University employs the pancake geometry where a prone-positioned animal is rotated horizontally between an x-ray source and detector panel. This study is to assess the CBCT image quality in the pancake geometry and investigate potential methods for improvement. We compared CBCT images acquired in the pancake geometry with those acquired in the tubular geometry when the phantom/animal was placed upright simulating the conventional CBCT geometry. Results showed signal-to-noise and contrast-to-noise ratios in the pancake geometry were reduced in comparison to the tubular geometry at the same dose level. But the overall spatial resolution within the transverse plane of the imaged cylinder/animal was better in the pancake geometry. A modest exposure increase to two folds in the pancake geometry can improve image quality to a level close to the tubular geometry. Image quality can also be improved by inclining the animal, which reduces streak artifacts caused by bony structures. The major factor resulting in the inferior image quality in the pancake geometry is the elevated beam attenuation along the long axis of the phantom/animal and consequently increased scatter-to-primary ratio in that orientation. Not withstanding, the image quality in the pancake-geometry CBCT is adequate to support image guided animal positioning, while providing unique advantages of non-coplanar and multiple mice irradiation. This study also provides useful knowledge about the image quality in the two very different imaging geometries, i.e. pancake and tubular geometry

Evaluation of a cone beam computed tomography geometry for image guided small animal irradiation.

Science.gov (United States)

Yang, Yidong; Armour, Michael; Wang, Ken Kang-Hsin; Gandhi, Nishant; Iordachita, Iulian; Siewerdsen, Jeffrey; Wong, John

2015-07-07

The conventional imaging geometry for small animal cone beam computed tomography (CBCT) is that a detector panel rotates around the head-to-tail axis of an imaged animal ('tubular' geometry). Another unusual but possible imaging geometry is that the detector panel rotates around the anterior-to-posterior axis of the animal ('pancake' geometry). The small animal radiation research platform developed at Johns Hopkins University employs the pancake geometry where a prone-positioned animal is rotated horizontally between an x-ray source and detector panel. This study is to assess the CBCT image quality in the pancake geometry and investigate potential methods for improvement. We compared CBCT images acquired in the pancake geometry with those acquired in the tubular geometry when the phantom/animal was placed upright simulating the conventional CBCT geometry. Results showed signal-to-noise and contrast-to-noise ratios in the pancake geometry were reduced in comparison to the tubular geometry at the same dose level. But the overall spatial resolution within the transverse plane of the imaged cylinder/animal was better in the pancake geometry. A modest exposure increase to two folds in the pancake geometry can improve image quality to a level close to the tubular geometry. Image quality can also be improved by inclining the animal, which reduces streak artifacts caused by bony structures. The major factor resulting in the inferior image quality in the pancake geometry is the elevated beam attenuation along the long axis of the phantom/animal and consequently increased scatter-to-primary ratio in that orientation. Not withstanding, the image quality in the pancake-geometry CBCT is adequate to support image guided animal positioning, while providing unique advantages of non-coplanar and multiple mice irradiation. This study also provides useful knowledge about the image quality in the two very different imaging geometries, i.e. pancake and tubular geometry, respectively.

Basic performance and stability of a CdTe solid-state detector panel.

Science.gov (United States)

Tsuchiya, Katsutoshi; Takahashi, Isao; Kawaguchi, Tsuneaki; Yokoi, Kazuma; Morimoto, Yuuichi; Ishitsu, Takafumi; Suzuki, Atsurou; Ueno, Yuuichirou; Kobashi, Keiji

2010-05-01

We have developed a prototype gamma camera system (R1-M) using a cadmium telluride (CdTe) detector panel and evaluated the basic performance and the spectral stability. The CdTe panel consists of 5-mm-thick crystals. The field of view is 134 x 268 mm comprising 18,432 pixels with a pixel pitch of 1.4 mm. Replaceable small CdTe modules are mounted on to the circuit board by dedicated zero insertion force connectors. To make the readout circuit compact, the matrix read out is processed by dedicated ASICs. The panel is equipped with a cold-air cooling system. The temperature and humidity in the panel were kept at 20 degrees C and below 70% relative humidity. CdTe polarization was suppressed by the bias refresh technique to stabilize the detector. We also produced three dedicated square pixel-matched collimators: LEGP (20 mm-thick), LEHR (27 mm-thick), and LEUHR (35 mm-thick). We evaluated their basic performance (energy resolution, system resolution, and sensitivity) and the spectral stability in terms of short-term (several hours of continuous acquisition) and long-term (infrequent measurements over more than a year) activity. The intrinsic energy resolution (FWHM) acquired with Tc-99m (140.5 keV) was 6.6%. The spatial resolutions (FWHM at a distance of 100 mm) with LEGP, LEHR, and LEUHR collimators were 5.7, 4.9, and 4.2 mm, and the sensitivities were 71, 39, and 23 cps/MBq, respectively. The energy peak position and the intrinsic energy resolution after several hours of operation were nearly the same as the values a few minutes after the system was powered on; the variation of the peak position was <0.2%, and that of the resolution was about 0.3%. Infrequent measurements conducted over a year showed that the variations of the energy peak position and the intrinsic energy resolution of the system were at a similar level to those described above. The basic performance of the CdTe-gamma camera system was evaluated, and its stability was verified. It was shown that the

Development of flat panel X-ray detector utilizing a CdZnTe film as conversion layer

International Nuclear Information System (INIS)

Tokuda, Satoshi; Kishihara, Hiroyuki; Kaino, Masatomo; Sato, Toshiyuki

2006-01-01

A polycrystalline CdZnTe film formed by the CSS (closed-spaced sublimation) method is one of the most promising materials as a conversion layer of next-generation highly efficient flat-panel X-ray detectors. Therefore, we have developed a prototype of a new flat-panel X-ray detector (a sensing region of 3 inches by 3 inches) with the film and evaluated its commercial feasibility. This paper describes evaluation of the physical and imaging properties of the prototype and explains the features of the CdZnTe film and the construction, specifications, and fabrication procedures of the prototype. Also included in this paper are formation of a semiconductor thin film barrier layer by the CBD (chemical bath deposition) method and conjunction of a sensor substrate and a TFT array substrate with the bump electrodes formed by screen printing, both of which we have developed during the course of the development of the prototype. (author)

A unified analysis of FBP-based algorithms in helical cone-beam and circular cone- and fan-beam scans

International Nuclear Information System (INIS)

Pan Xiaochuan; Xia Dan; Zou Yu; Yu Lifeng

2004-01-01

A circular scanning trajectory is and will likely remain a popular choice of trajectory in computed tomography (CT) imaging because it is easy to implement and control. Filtered-backprojection (FBP)-based algorithms have been developed previously for approximate and exact reconstruction of the entire image or a region of interest within the image in circular cone-beam and fan-beam cases. Recently, we have developed a 3D FBP-based algorithm for image reconstruction on PI-line segments in a helical cone-beam scan. In this work, we demonstrated that the 3D FBP-based algorithm indeed provided a rather general formulation for image reconstruction from divergent projections (such as cone-beam and fan-beam projections). On the basis of this formulation we derived new approximate or exact algorithms for image reconstruction in circular cone-beam or fan-beam scans, which can be interpreted as special cases of the helical scan. Existing algorithms corresponding to the derived algorithms were identified. We also performed a preliminary numerical study to verify our theoretical results in each of the cases. The results in the work can readily be generalized to other non-circular trajectories

Solar panels as air Cherenkov detectors for extremely high energy cosmic rays

International Nuclear Information System (INIS)

Cecchini, S.; D'Antone, I.; Degli Esposti, L.; Giacomelli, G.; Guerra, M.; Lax, I.; Mandrioli, G.; Parretta, A.; Sarno, A.; Schioppo, R.; Sorel, M.; Spurio, M.

2000-01-01

Increasing interest towards the observation of the highest energy cosmic rays has motivated the development of new detection techniques. The properties of the Cherenkov photon pulse emitted in the atmosphere by these very rare particles indicate low-cost semiconductor detectors as good candidates for their optical read-out. The aim of this paper is to evaluate the viability of solar panels for this purpose. The experimental framework resulting from measurements performed with suitably-designed solar cells and large conventional photovoltaic areas is presented. A discussion on the obtained and achievable sensitivities follows

An improved cone-beam filtered backprojection reconstruction algorithm based on x-ray angular correction and multiresolution analysis

International Nuclear Information System (INIS)

Sun, Y.; Hou, Y.; Yan, Y.

2004-01-01

With the extensive application of industrial computed tomography in the field of non-destructive testing, how to improve the quality of the reconstructed image is receiving more and more concern. It is well known that in the existing cone-beam filtered backprojection reconstruction algorithms the cone angle is controlled within a narrow range. The reason of this limitation is the incompleteness of projection data when the cone angle increases. Thus the size of the tested workpiece is limited. Considering the characteristic of X-ray cone angle, an improved cone-beam filtered back-projection reconstruction algorithm taking account of angular correction is proposed in this paper. The aim of our algorithm is to correct the cone-angle effect resulted from the incompleteness of projection data in the conventional algorithm. The basis of the correction is the angular relationship among X-ray source, tested workpiece and the detector. Thus the cone angle is not strictly limited and this algorithm may be used to detect larger workpiece. Further more, adaptive wavelet filter is used to make multiresolution analysis, which can modify the wavelet decomposition series adaptively according to the demand for resolution of local reconstructed area. Therefore the computation and the time of reconstruction can be reduced, and the quality of the reconstructed image can also be improved. (author)

TU-EF-207-02: Spectral Mammography Based on Photon Counting Detectors

Energy Technology Data Exchange (ETDEWEB)

Molloi, S. [University of California (United States)

2015-06-15

mode due to lower photon fluence per projection. This may require fast-frame acquisition and symmetric or asymmetric pixel binning in some systems. Recent studies investigated the performance of increased conversion layer thickness for contrast-enhanced imaging of the breast in dual-energy acquisition mode. In other direct conversion detectors operating in the avalanche mode, sensitivities close to the single photon response are also explored for mammography and breast tomosynthesis. The potential advantages and challenges of this approach are described. Dedicated breast CT brings x-ray imaging of the breast to true tomographic 3D imaging. It can eliminate the tissue superposition problem and does not require physical compression of the breast. Using cone beam geometry and a flat-panel detector, several hundred projections are acquired and reconstructed to near isotropic voxels. Multiplanar reconstruction facilitates viewing the breast volume in any desired orientation. Ongoing clinical studies, the current state-of-the art, and research to advance the technology are described. Learning Objectives: To understand the ongoing developments in x-ray imaging of the breast To understand the approaches and applications of spectral mammography To understand the potential advantages of distributed x-ray source arrays for digital breast tomosynthesis To understand the ongoing developments in detector technology for digital mammography and breast tomosynthesis To understand the current state-of-the-art for dedicated cone-beam breast CT and research to advance the technology. Research collaboration with Koning Corporation.

TU-EF-207-02: Spectral Mammography Based on Photon Counting Detectors

International Nuclear Information System (INIS)

Molloi, S.

2015-01-01

mode due to lower photon fluence per projection. This may require fast-frame acquisition and symmetric or asymmetric pixel binning in some systems. Recent studies investigated the performance of increased conversion layer thickness for contrast-enhanced imaging of the breast in dual-energy acquisition mode. In other direct conversion detectors operating in the avalanche mode, sensitivities close to the single photon response are also explored for mammography and breast tomosynthesis. The potential advantages and challenges of this approach are described. Dedicated breast CT brings x-ray imaging of the breast to true tomographic 3D imaging. It can eliminate the tissue superposition problem and does not require physical compression of the breast. Using cone beam geometry and a flat-panel detector, several hundred projections are acquired and reconstructed to near isotropic voxels. Multiplanar reconstruction facilitates viewing the breast volume in any desired orientation. Ongoing clinical studies, the current state-of-the art, and research to advance the technology are described. Learning Objectives: To understand the ongoing developments in x-ray imaging of the breast To understand the approaches and applications of spectral mammography To understand the potential advantages of distributed x-ray source arrays for digital breast tomosynthesis To understand the ongoing developments in detector technology for digital mammography and breast tomosynthesis To understand the current state-of-the-art for dedicated cone-beam breast CT and research to advance the technology. Research collaboration with Koning Corporation

High resolution X-ray imaging of bone-implant interface by large area flat-panel detector

International Nuclear Information System (INIS)

Kytyr, D; Jirousek, O; Dammer, J

2011-01-01

The aim of the research was to investigate the cemented bone-implant interface behavior (cement layer degradation and bone-cement interface debonding) with emphasis on imaging techniques suitable to detect the early defects in the cement layer. To simulate in vivo conditions a human pelvic bone was implanted with polyurethane acetabular cup using commercial acrylic bone cement. The implanted cup was then loaded in a custom hip simulator to initiate fatigue crack propagation in the bone cement. The pelvic bone was then repetitively scanned in a micro-tomography device. Reconstructed tomography images showed failure processes that occurred in the cement layer during the first 250,000 cycles. A failure in cemented acetabular implant - debonding, crumbling and smeared cracks - has been found to be at the bone-cement interface. Use of micro-focus source and high resolution flat panel detector of large physical dimensions allowed to reconstruct the micro-structural models suitable for investigation of migration, micro-motions and consecutive loosening of the implant. The large area flat panel detector with physical dimensions 120 x 120mm with 50μm pixel size provided a superior image quality compared to clinical CT systems with 300-150μm pixel size.

Attic Retrofits Using Nail-Base Insulated Panels

Energy Technology Data Exchange (ETDEWEB)

Mallay, David [Home Innovation Research Labs; Kochkin, Vladimir [Home Innovation Research Labs

2018-03-26

This project developed and demonstrated a roof/attic energy retrofit solution using nail-base insulated panels for existing homes where traditional attic insulation approaches are not effective or feasible. Nail-base insulated panels (retrofit panels) consist of rigid foam insulation laminated to one face of a wood structural panel. The prefabricated panels are installed above the existing roof deck during a reroofing effort.

Iterative image-domain ring artifact removal in cone-beam CT

Science.gov (United States)

Liang, Xiaokun; Zhang, Zhicheng; Niu, Tianye; Yu, Shaode; Wu, Shibin; Li, Zhicheng; Zhang, Huailing; Xie, Yaoqin

2017-07-01

Ring artifacts in cone beam computed tomography (CBCT) images are caused by pixel gain variations using flat-panel detectors, and may lead to structured non-uniformities and deterioration of image quality. The purpose of this study is to propose a method of general ring artifact removal in CBCT images. This method is based on the polar coordinate system, where the ring artifacts manifest as stripe artifacts. Using relative total variation, the CBCT images are first smoothed to generate template images with fewer image details and ring artifacts. By subtracting the template images from the CBCT images, residual images with image details and ring artifacts are generated. As the ring artifact manifests as a stripe artifact in a polar coordinate system, the artifact image can be extracted by mean value from the residual image; the image details are generated by subtracting the artifact image from the residual image. Finally, the image details are compensated to the template image to generate the corrected images. The proposed framework is iterated until the differences in the extracted ring artifacts are minimized. We use a 3D Shepp-Logan phantom, Catphan©504 phantom, uniform acrylic cylinder, and images from a head patient to evaluate the proposed method. In the experiments using simulated data, the spatial uniformity is increased by 1.68 times and the structural similarity index is increased from 87.12% to 95.50% using the proposed method. In the experiment using clinical data, our method shows high efficiency in ring artifact removal while preserving the image structure and detail. The iterative approach we propose for ring artifact removal in cone-beam CT is practical and attractive for CBCT guided radiation therapy.

Initial experiences in clinical application of the THORAX-FD: flat-panel detector radiography in thoracic diagnosis

International Nuclear Information System (INIS)

Herrmann, K.A.; Staebler, A.; Bonel, H.; Kulinna, C.; Holzknecht, N.; Reiser, M.F.; Geiger, B.; Boehm, S.; Maschke, M.

2000-01-01

The flat-panel detector closes the gap between radiography and the digital diagnostics equipment currently in use. In addition to the dose reduction that can be expected, the availability of diagnostic information in digital form enables the user to optimize the clinical workflow and to network radiography directly with a digital archiving and communication system. (orig.)

Design and characterization of a dedicated cone-beam CT scanner for detection of acute intracranial hemorrhage

Science.gov (United States)

Xu, J.; Sisniega, A.; Zbijewski, W.; Dang, H.; Stayman, J. W.; Wang, X.; Foos, D. H.; Aygun, N.; Koliatsos, V. E.; Siewerdsen, J. H.

2016-03-01

Purpose: Prompt and reliable detection of intracranial hemorrhage (ICH) has substantial clinical impact in diagnosis and treatment of stroke and traumatic brain injury. This paper describes the design, development, and preliminary performance characterization of a dedicated cone-beam CT (CBCT) head scanner prototype for imaging of acute ICH. Methods: A task-based image quality model was used to analyze the detectability index as a function of system configuration, and hardware design was guided by the results of this model-based optimization. A robust artifact correction pipeline was developed using GPU-accelerated Monte Carlo (MC) scatter simulation, beam hardening corrections, detector veiling glare, and lag deconvolution. An iterative penalized weighted least-squares (PWLS) reconstruction framework with weights adjusted for artifact-corrected projections was developed. Various bowtie filters were investigated for potential dose and image quality benefits, with a MC-based tool providing estimates of spatial dose distribution. Results: The initial prototype will feature a source-detector distance of 1000 mm and source-axis distance of 550 mm, a 43x43 cm2 flat panel detector, and a 15° rotating anode x-ray source with 15 kW power and 0.6 focal spot size. Artifact correction reduced image nonuniformity by ~250 HU, and PWLS reconstruction with modified weights improved the contrast to noise ratio by 20%. Inclusion of a bowtie filter can potentially reduce dose by 50% and improve CNR by 25%. Conclusions: A dedicated CBCT system capable of imaging millimeter-scale acute ICH was designed. Preliminary findings support feasibility of point-of-care applications in TBI and stroke imaging, with clinical studies beginning on a prototype.

Reliability and Repeatability of Cone Density Measurements in Patients With Stargardt Disease and RPGR-Associated Retinopathy.

Science.gov (United States)

Tanna, Preena; Kasilian, Melissa; Strauss, Rupert; Tee, James; Kalitzeos, Angelos; Tarima, Sergey; Visotcky, Alexis; Dubra, Alfredo; Carroll, Joseph; Michaelides, Michel

2017-07-01

To assess reliability and repeatability of cone density measurements by using confocal and (nonconfocal) split-detector adaptive optics scanning light ophthalmoscopy (AOSLO) imaging. It will be determined whether cone density values are significantly different between modalities in Stargardt disease (STGD) and retinitis pigmentosa GTPase regulator (RPGR)-associated retinopathy. Twelve patients with STGD (aged 9-52 years) and eight with RPGR-associated retinopathy (aged 11-31 years) were imaged using both confocal and split-detector AOSLO simultaneously. Four graders manually identified cone locations in each image that were used to calculate local densities. Each imaging modality was evaluated independently. The data set consisted of 1584 assessments of 99 STGD images (each image in two modalities and four graders who graded each image twice) and 928 RPGR assessments of 58 images (each image in two modalities and four graders who graded each image twice). For STGD assessments the reliability for confocal and split-detector AOSLO was 67.9% and 95.9%, respectively, and the repeatability was 71.2% and 97.3%, respectively. The differences in the measured cone density values between modalities were statistically significant for one grader. For RPGR assessments the reliability for confocal and split-detector AOSLO was 22.1% and 88.5%, respectively, and repeatability was 63.2% and 94.5%, respectively. The differences in cone density between modalities were statistically significant for all graders. Split-detector AOSLO greatly improved the reliability and repeatability of cone density measurements in both disorders and will be valuable for natural history studies and clinical trials using AOSLO. However, it appears that these indices may be disease dependent, implying the need for similar investigations in other conditions.

SU-F-I-06: Evaluation of Imaging Dose for Modulation Layer Based Dual Energy Cone-Beam CT

Energy Technology Data Exchange (ETDEWEB)

Ju, Eunbin [Department of Medical Science, Ewha Womans University, Seoul (Korea, Republic of); Ahn, SoHyun; Cho, Samju; Keum, Ki Chang [Department of Radiation Oncology, School of Medicine, Yonsei Univeristy, Seoul (Korea, Republic of); Lee, Rena [Department of Radiation Oncology, School of Medicine, Ewha Womans University, Seoul (Korea, Republic of)

2016-06-15

Purpose: Dual energy cone beam CT system is finding a variety of promising applications in diagnostic CT, both in imaging of endogenous materials and exogenous materials across a range of body sites. Dual energy cone beam CT system to suggest in this study acquire image by rotating 360 degree with half of the X-ray window covered using copper modulation layer. In the region that covered by modulation layer absorb the low energy X-ray by modulation layer. Relative high energy X-ray passes through the layer and contributes to image reconstruction. Dose evaluation should be carried out in order to utilize such an imaging acquirement technology for clinical use. Methods: For evaluating imaging dose of modulation layer based dual energy cone beam CT system, Prototype cone beam CT that configured X-ray tube (D054SB, Toshiba, Japan) and detector (PaxScan 2520V, Varian Medical Systems, Palo Alto, CA) is used. A range of 0.5–2.0 mm thickness of modulation layer is implemented in Monte Carlo simulation (MCNPX, ver. 2.6.0, Los Alamos National Laboratory, USA) with half of X-ray window covered. In-house phantom using in this study that has 3 cylindrical phantoms configured water, Teflon air with PMMA covered for verifying the comparability the various material in human body and is implemented in Monte Carlo simulation. The actual dose with 2.0 mm copper covered half of X-ray window is measured using Gafchromic EBT3 film with 5.0 mm bolus for compared with simulative dose. Results: Dose in phantom reduced 33% by copper modulation layer of 2.0 mm. Scattering dose occurred in modulation layer by Compton scattering effect is 0.04% of overall dose. Conclusion: Modulation layer of that based dual energy cone beam CT has not influence on unnecessary scatter dose. This study was supported by the Radiation Safety Research Programs (1305033) through the Nuclear Safety and Security Commission.

Reliability and Repeatability of Cone Density Measurements in Patients With Stargardt Disease and RPGR-Associated Retinopathy

Science.gov (United States)

Tanna, Preena; Kasilian, Melissa; Strauss, Rupert; Tee, James; Kalitzeos, Angelos; Tarima, Sergey; Visotcky, Alexis; Dubra, Alfredo; Carroll, Joseph; Michaelides, Michel

2017-01-01

Purpose To assess reliability and repeatability of cone density measurements by using confocal and (nonconfocal) split-detector adaptive optics scanning light ophthalmoscopy (AOSLO) imaging. It will be determined whether cone density values are significantly different between modalities in Stargardt disease (STGD) and retinitis pigmentosa GTPase regulator (RPGR)–associated retinopathy. Methods Twelve patients with STGD (aged 9–52 years) and eight with RPGR-associated retinopathy (aged 11–31 years) were imaged using both confocal and split-detector AOSLO simultaneously. Four graders manually identified cone locations in each image that were used to calculate local densities. Each imaging modality was evaluated independently. The data set consisted of 1584 assessments of 99 STGD images (each image in two modalities and four graders who graded each image twice) and 928 RPGR assessments of 58 images (each image in two modalities and four graders who graded each image twice). Results For STGD assessments the reliability for confocal and split-detector AOSLO was 67.9% and 95.9%, respectively, and the repeatability was 71.2% and 97.3%, respectively. The differences in the measured cone density values between modalities were statistically significant for one grader. For RPGR assessments the reliability for confocal and split-detector AOSLO was 22.1% and 88.5%, respectively, and repeatability was 63.2% and 94.5%, respectively. The differences in cone density between modalities were statistically significant for all graders. Conclusions Split-detector AOSLO greatly improved the reliability and repeatability of cone density measurements in both disorders and will be valuable for natural history studies and clinical trials using AOSLO. However, it appears that these indices may be disease dependent, implying the need for similar investigations in other conditions. PMID:28738413

A cone-beam tomography system with a reduced size planar detector: A backprojection-filtration reconstruction algorithm as well as numerical and practical experiments

International Nuclear Information System (INIS)

Li Liang; Chen Zhiqiang; Zhang Li; Xing Yuxiang; Kang Kejun

2007-01-01

In a traditional cone-beam computed tomography (CT) system, the cost of product and computation is very high. In this paper, we develop a transversely truncated cone-beam X-ray CT system with a reduced-size detector positioned off-center, in which X-ray beams only cover half of the object. The existing filtered backprojection (FBP) or backprojection-filtration (BPF) algorithms are not directly applicable in this new system. Hence, we develop a BPF-type direct backprojection algorithm. Different from the traditional rebinning methods, our algorithm directly backprojects the pretreated projection data without rebinning. This makes the algorithm compact and computationally more efficient. Because of avoiding interpolation errors of rebinning process, higher spatial resolution is obtained. Finally, some numerical simulations and practical experiments are done to validate the proposed algorithm and compare with rebinning algorithm

Cone Algorithm of Spinning Vehicles under Dynamic Coning Environment

Directory of Open Access Journals (Sweden)

Shuang-biao Zhang

2015-01-01

Full Text Available Due to the fact that attitude error of vehicles has an intense trend of divergence when vehicles undergo worsening coning environment, in this paper, the model of dynamic coning environment is derived firstly. Then, through investigation of the effect on Euler attitude algorithm for the equivalency of traditional attitude algorithm, it is found that attitude error is actually the roll angle error including drifting error and oscillating error, which is induced directly by dynamic coning environment and further affects the pitch angle and yaw angle through transferring. Based on definition of the cone frame and cone attitude, a cone algorithm is proposed by rotation relationship to calculate cone attitude, and the relationship between cone attitude and Euler attitude of spinning vehicle is established. Through numerical simulations with different conditions of dynamic coning environment, it is shown that the induced error of Euler attitude fluctuates by the variation of precession and nutation, especially by that of nutation, and the oscillating frequency of roll angle error is twice that of pitch angle error and yaw angle error. In addition, the rotation angle is more competent to describe the spinning process of vehicles under coning environment than Euler angle gamma, and the real pitch angle and yaw angle are calculated finally.

Measurement of breast tissue composition with dual energy cone-beam computed tomography: A postmortem study

Energy Technology Data Exchange (ETDEWEB)

Ding Huanjun; Ducote, Justin L.; Molloi, Sabee [Department of Radiological Sciences, University of California, Irvine, California 92697 (United States)

2013-06-15

Purpose: To investigate the feasibility of a three-material compositional measurement of water, lipid, and protein content of breast tissue with dual kVp cone-beam computed tomography (CT) for diagnostic purposes. Methods: Simulations were performed on a flat panel-based computed tomography system with a dual kVp technique in order to guide the selection of experimental acquisition parameters. The expected errors induced by using the proposed calibration materials were also estimated by simulation. Twenty pairs of postmortem breast samples were imaged with a flat-panel based dual kVp cone-beam CT system, followed by image-based material decomposition using calibration data obtained from a three-material phantom consisting of water, vegetable oil, and polyoxymethylene plastic. The tissue samples were then chemically decomposed into their respective water, lipid, and protein contents after imaging to allow direct comparison with data from dual energy decomposition. Results: Guided by results from simulation, the beam energies for the dual kVp cone-beam CT system were selected to be 50 and 120 kVp with the mean glandular dose divided equally between each exposure. The simulation also suggested that the use of polyoxymethylene as the calibration material for the measurement of pure protein may introduce an error of -11.0%. However, the tissue decomposition experiments, which employed a calibration phantom made out of water, oil, and polyoxymethylene, exhibited strong correlation with data from the chemical analysis. The average root-mean-square percentage error for water, lipid, and protein contents was 3.58% as compared with chemical analysis. Conclusions: The results of this study suggest that the water, lipid, and protein contents can be accurately measured using dual kVp cone-beam CT. The tissue compositional information may improve the sensitivity and specificity for breast cancer diagnosis.

Response of CR39 detector to 5 A GeV Si14+ ions and measurement of total charge changing cross-section

International Nuclear Information System (INIS)

Gupta, Renu; Kumar, Ashavani

2013-01-01

In the present work, response of CR39 track etch detector was obtained by cone-height measurement technique. CR39 track etch detector was used to identify the incident charged particles and their fragments by the measurements of cone-height of tracks using an optical microscope DM6000 M and automated image analyzer system installed with Leica QWin Plus software. The CR39 detector was calibrated and the response points were fitted with a linear relation and all the points are within the limits of the experimental errors. The charge resolution of the detector was calculated to be 0.2e. The response function is obtained and fitted with a linear relation which is good throughout Z/β=6.1–14.1. The experimental value of the total charge changing cross-section of 5 A GeV Si 14+ ion beam in polyethylene and CR39 combined target is σ tot =(734±128) mb. The total charge changing cross-section is compared with the experimental results of others based on cone base-area measurement technique and also fitted by the Bradt–Peters geometrical cross-section. - Highlights: • Charge resolution of 0.2e was obtained by cone-height measurement. • Consistency in manual measurements of cone-heights is presented. • Response of CR39 detector was obtained and fitted with first degree polynomial. • Total charge changing cross-section of 5 A GeV Si 14+ ions in CH 2 and CR39 as a combined target was calculated

Geomorphometric variability of "monogenetic" volcanic cones: Evidence from Mauna Kea, Lanzarote and experimental cones

Science.gov (United States)

Kervyn, M.; Ernst, G. G. J.; Carracedo, J.-C.; Jacobs, P.

2012-01-01

Volcanic cones are the most common volcanic constructs on Earth. Their shape can be quantified using two morphometric ratios: the crater/cone base ratio (W cr/W co) and the cone height/width ratio (H co/W co). The average values for these ratios obtained over entire cone fields have been explained by the repose angle of loose granular material (i.e. scoria) controlling cone slopes. The observed variability in these ratios between individual cones has been attributed to the effect of erosional processes or contrasting eruptive conditions on cone morphometry. Using a GIS-based approach, high spatial resolution Digital Elevation Models and airphotos, two new geomorphometry datasets for cone fields at Mauna Kea (Hawaii, USA) and Lanzarote (Canary Islands, Spain) are extracted and analyzed here. The key observation in these datasets is the great variability in morphometric ratios, even for simple-shape and well-preserved cones. Simple analog experiments are presented to analyze factors influencing the morphometric ratios. The formation of a crater is simulated within an analog cone (i.e. a sand pile) by opening a drainage conduit at the cone base. Results from experiments show that variability in the morphometric ratios can be attributed to variations in the width, height and horizontal offset of the drainage point relative to the cone symmetry axis, to the dip of the underlying slope or to the influence of a small proportion of fine cohesive material. GIS analysis and analog experiments, together with specific examples of cones documented in the field, suggest that the morphometric ratios for well-preserved volcanic cones are controlled by a combination of 1) the intrinsic cone material properties, 2) time-dependent eruption conditions, 3) the local setting, and 4) the method used to estimate the cone height. Implications for interpreting cone morphometry solely as either an age or as an eruption condition indicator are highlighted.

Visible and Near-Infrared Spectroscopy of Hephaestus Fossae Cratered Cones, Mars

Science.gov (United States)

Dapremont, A.; Wray, J. J.

2017-12-01

Hephaestus Fossae are a system of sub-parallel fractures on Mars (> 500 km long) interpreted as near-surface tensional cracks [1]. Images of the Martian surface from the High Resolution Imaging Science Experiment have revealed cratered cones within the Hephaestus Fossae region. A volcanic origin (cinder/tuff cones) has been proposed for these features based on morphometric measurements and fine-scale surface characteristics [2]. In an effort to further constrain the origin of these cones as the products of igneous or sedimentary volcanism, we use data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). We take advantage of CRISM's S (0.4 - 1.0 microns) and L (1.0 - 3.9 microns) detector wavelength ranges to investigate the presence or absence of spectral signatures consistent with previous identifications of igneous and mud volcanism products on Mars [3,4]. Hephaestus Fossae cratered cone rims exhibit a consistent nanophase ferric oxide signature. We also identify ferrous phases and 3-micron absorptions (attributed to fundamental vibrational stretch frequencies in H2O) on the crater rims of several cones. Mafic signatures on cratered cone rims support an igneous provenance for these features. The 3-micron absorptions are consistent with the presence of structurally bound or adsorbed water. Our CRISM observations are similar to those of small edifice features in Chryse Planitia, which were interpreted as mud volcanism products based on their enrichment of nanophase ferric minerals and 3-micron absorptions on summit crater rims [3]. Hydrothermal activity was invoked for a Coprates Chasma pitted cone (scoria/tuff cone) based on CRISM identification of partially dehydrated opaline silica, which we do not observe in Hephaestus Fossae [4]. Our spectral observations are more consistent with mud volcanism, but we do not definitively rule out an igneous volcanic origin for the cones in our study region. We demonstrate that VNIR spectroscopy is a valuable

Source strength verification and quality assurance of preloaded brachytherapy needles using a CMOS flat panel detector

Energy Technology Data Exchange (ETDEWEB)

Golshan, Maryam, E-mail: maryam.golshan@bccancer.bc.ca [Department of Physics, University of British Columbia, Vancouver, British Columbia V6T1Z1, Canada and Department of Medical Physics, Vancouver Center, British Columbia Cancer Agency, Vancouver, British Columbia V5Z 4E6 (Canada); Spadinger, Ingrid [Department of Medical Physics, Vancouver Center, British Columbia Cancer Agency, Vancouver, British Columbia V5Z 4E6 (Canada); Chng, Nick [Department of Medical Physics, Center for the North, British Columbia Cancer Agency, Prince George, British Columbia V2M 7E9 (Canada)

2016-06-15

Purpose: Current methods of low dose rate brachytherapy source strength verification for sources preloaded into needles consist of either assaying a small number of seeds from a separate sample belonging to the same lot used to load the needles or performing batch assays of a subset of the preloaded seed trains. Both of these methods are cumbersome and have the limitations inherent to sampling. The purpose of this work was to investigate an alternative approach that uses an image-based, autoradiographic system capable of the rapid and complete assay of all sources without compromising sterility. Methods: The system consists of a flat panel image detector, an autoclavable needle holder, and software to analyze the detected signals. The needle holder was designed to maintain a fixed vertical spacing between the needles and the image detector, and to collimate the emissions from each seed. It also provides a sterile barrier between the needles and the imager. The image detector has a sufficiently large image capture area to allow several needles to be analyzed simultaneously.Several tests were performed to assess the accuracy and reproducibility of source strengths obtained using this system. Three different seed models (Oncura 6711 and 9011 {sup 125}I seeds, and IsoAid Advantage {sup 103}Pd seeds) were used in the evaluations. Seeds were loaded into trains with at least 1 cm spacing. Results: Using our system, it was possible to obtain linear calibration curves with coverage factor k = 1 prediction intervals of less than ±2% near the centre of their range for the three source models. The uncertainty budget calculated from a combination of type A and type B estimates of potential sources of error was somewhat larger, yielding (k = 1) combined uncertainties for individual seed readings of 6.2% for {sup 125}I 6711 seeds, 4.7% for {sup 125}I 9011 seeds, and 11.0% for Advantage {sup 103}Pd seeds. Conclusions: This study showed that a flat panel detector dosimetry system

Cone Beam Computed Tomography (CBCT) in the Field of Interventional Oncology of the Liver

Energy Technology Data Exchange (ETDEWEB)

Bapst, Blanche, E-mail: blanchebapst@hotmail.com; Lagadec, Matthieu, E-mail: matthieu.lagadec@bjn.aphp.fr [Beaujon Hospital, University Hospitals Paris Nord Val de Seine, Beaujon, Department of Radiology (France); Breguet, Romain, E-mail: romain.breguet@hcuge.ch [University Hospital of Geneva (Switzerland); Vilgrain, Valérie, E-mail: Valerie.vilgrain@bjn.aphp.fr; Ronot, Maxime, E-mail: maxime.ronot@bjn.aphp.fr [Beaujon Hospital, University Hospitals Paris Nord Val de Seine, Beaujon, Department of Radiology (France)

2016-01-15

Cone beam computed tomography (CBCT) is an imaging modality that provides computed tomographic images using a rotational C-arm equipped with a flat panel detector as part of the Angiography suite. The aim of this technique is to provide additional information to conventional 2D imaging to improve the performance of interventional liver oncology procedures (intraarterial treatments such as chemoembolization or selective internal radiation therapy, and percutaneous tumor ablation). CBCT provides accurate tumor detection and targeting, periprocedural guidance, and post-procedural evaluation of treatment success. This technique can be performed during intraarterial or intravenous contrast agent administration with various acquisition protocols to highlight liver tumors, liver vessels, or the liver parenchyma. The purpose of this review is to present an extensive overview of published data on CBCT in interventional oncology of the liver, for both percutaneous ablation and intraarterial procedures.

PV panel model based on datasheet values

DEFF Research Database (Denmark)

Sera, Dezso; Teodorescu, Remus; Rodriguez, Pedro

2007-01-01

This work presents the construction of a model for a PV panel using the single-diode five-parameters model, based exclusively on data-sheet parameters. The model takes into account the series and parallel (shunt) resistance of the panel. The equivalent circuit and the basic equations of the PV cell....... Based on these equations, a PV panel model, which is able to predict the panel behavior in different temperature and irradiance conditions, is built and tested....

Whole body dual X-ray absorptiometry for bone mineral density and body composition using a flat panel detector

International Nuclear Information System (INIS)

Dinten, J.M.; Robert-Coutant, C.; Gonon, G.; Bordy, T.

2003-01-01

Whole-body dual-energy X-ray absorptiometry (DXA) systems are used for the determination of bone mineral density (BMD) but also for body composition estimates (lean mass and fat mass). The calculation is based on the difference in attenuation of body tissues for a low-energy of about 50 KeV and a high-energy of about 80-100 KeV. The measurement of dual-energy projections allows first to compute to the body composition in the non-bone area, and then to extrapolate the fat / lean ratio of soft tissue into the bone area in order to compute the BMD. Since detectors have limited area, a whole body examination requires a scan of the patient and a reconstruction process in order to build up a large field image from smaller radiographs. This reconstruction process must keep the quantitative value of the radiographs, and avoid any distortion which could be a consequence of the conic acquisition geometry. The cone angle is low (6 at maximum) and the large overlap between radiographs helps to reconstruct an image equivalent with a parallel-beam geometry. Scatter is corrected from the radiographs before reconstruction, as described in a previous paper ('Dual-energy X-rays absorptiometry using a 2D digital radiography detector. Application to bone densitometry', SPIE Medical Imaging 2001, Medical Physics). We have developed an original reconstruction method dedicated to whole-body examinations which will be described. Thanks to the quasi-radiologic quality of the detector, reconstructed images are of very good quality and this makes the measurement of BMD and fat / lean masses easier. (author)

High-fidelity artifact correction for cone-beam CT imaging of the brain

Science.gov (United States)

Sisniega, A.; Zbijewski, W.; Xu, J.; Dang, H.; Stayman, J. W.; Yorkston, J.; Aygun, N.; Koliatsos, V.; Siewerdsen, J. H.

2015-02-01

CT is the frontline imaging modality for diagnosis of acute traumatic brain injury (TBI), involving the detection of fresh blood in the brain (contrast of 30-50 HU, detail size down to 1 mm) in a non-contrast-enhanced exam. A dedicated point-of-care imaging system based on cone-beam CT (CBCT) could benefit early detection of TBI and improve direction to appropriate therapy. However, flat-panel detector (FPD) CBCT is challenged by artifacts that degrade contrast resolution and limit application in soft-tissue imaging. We present and evaluate a fairly comprehensive framework for artifact correction to enable soft-tissue brain imaging with FPD CBCT. The framework includes a fast Monte Carlo (MC)-based scatter estimation method complemented by corrections for detector lag, veiling glare, and beam hardening. The fast MC scatter estimation combines GPU acceleration, variance reduction, and simulation with a low number of photon histories and reduced number of projection angles (sparse MC) augmented by kernel de-noising to yield a runtime of ~4 min per scan. Scatter correction is combined with two-pass beam hardening correction. Detector lag correction is based on temporal deconvolution of the measured lag response function. The effects of detector veiling glare are reduced by deconvolution of the glare response function representing the long range tails of the detector point-spread function. The performance of the correction framework is quantified in experiments using a realistic head phantom on a testbench for FPD CBCT. Uncorrected reconstructions were non-diagnostic for soft-tissue imaging tasks in the brain. After processing with the artifact correction framework, image uniformity was substantially improved, and artifacts were reduced to a level that enabled visualization of ~3 mm simulated bleeds throughout the brain. Non-uniformity (cupping) was reduced by a factor of 5, and contrast of simulated bleeds was improved from ~7 to 49.7 HU, in good agreement

Solar Panel based Milk Pasteurization

DEFF Research Database (Denmark)

Nielsen, Kirsten Mølgaard; Pedersen, Tom Søndergaard

This paper treats the subject of analysis, design and development of the control system for a solar panel based milk pasteurization system to be used in small villages in Tanzania. The analysis deals with the demands for an acceptable pasteurization, the varying energy supply and the low cost, low...... complexity, simple user interface and high reliability demands. Based on these demands a concept for the pasteurization system is established and a control system is developed. A solar panel has been constructed and the energy absorption has been tested in Tanzania. Based on the test, the pasteurization...... system is dimensioned. A functional prototype of the pasteurization facility with a capacity of 200 l milk/hour has been developed and tested. The system is prepared for solar panels as the main energy source and is ready for a test in Tanzania....

Solar Panel based Milk Pasteurization

DEFF Research Database (Denmark)

Nielsen, Kirsten Mølgaard; Pedersen, Tom Søndergaard

2002-01-01

This paper treats the subject of analysis, design and development of the control system for a solar panel based milk pasteurization system to be used in small villages in Tanzania. The analysis deals with the demands for an acceptable pasteurization, the varying energy supply and the low cost, low...... complexity, simple user interface and high reliability demands. Based on these demands a concept for the pasteurization system is established and a control system is developed. A solar panel has been constructed and the energy absorption has been tested in Tanzania. Based on the test, the pasteurization...... system is dimensioned. A functional prototype of the pasteurization facility with a capacity of 200 l milk/hour has been developed and tested. The system is prepared for solar panels as the main energy source and is ready for a test in Tanzania....

3D reconstruction based on compressed-sensing (CS)-based framework by using a dental panoramic detector.

Science.gov (United States)

Je, U K; Cho, H M; Hong, D K; Cho, H S; Park, Y O; Park, C K; Kim, K S; Lim, H W; Kim, G A; Park, S Y; Woo, T H; Cho, S I

2016-01-01

In this work, we propose a practical method that can combine the two functionalities of dental panoramic and cone-beam CT (CBCT) features in one by using a single panoramic detector. We implemented a CS-based reconstruction algorithm for the proposed method and performed a systematic simulation to demonstrate its viability for 3D dental X-ray imaging. We successfully reconstructed volumetric images of considerably high accuracy by using a panoramic detector having an active area of 198.4 mm × 6.4 mm and evaluated the reconstruction quality as a function of the pitch (p) and the angle step (Δθ). Our simulation results indicate that the CS-based reconstruction almost completely recovered the phantom structures, as in CBCT, for p≤2.0 and θ≤6°, indicating that it seems very promising for accurate image reconstruction even for large-pitch and few-view data. We expect the proposed method to be applicable to developing a cost-effective, volumetric dental X-ray imaging system. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

SU-F-18C-15: Model-Based Multiscale Noise Reduction On Low Dose Cone Beam Projection

International Nuclear Information System (INIS)

Yao, W; Farr, J

2014-01-01

Purpose: To improve image quality of low dose cone beam CT for patient positioning in radiation therapy. Methods: In low dose cone beam CT (CBCT) imaging systems, Poisson process governs the randomness of photon fluence at x-ray source and the detector because of the independent binomial process of photon absorption in medium. On a CBCT projection, the variance of fluence consists of the variance of noiseless imaging structure and that of Poisson noise, which is proportional to the mean (noiseless) of the fluence at the detector. This requires multiscale filters to smoothen noise while keeping the structure information of the imaged object. We used a mathematical model of Poisson process to design multiscale filters and established the balance of noise correction and structure blurring. The algorithm was checked with low dose kilo-voltage CBCT projections acquired from a Varian OBI system. Results: From the investigation of low dose CBCT of a Catphan phantom and patients, it showed that our model-based multiscale technique could efficiently reduce noise and meanwhile keep the fine structure of the imaged object. After the image processing, the number of visible line pairs in Catphan phantom scanned with 4 ms pulse time was similar to that scanned with 32 ms, and soft tissue structure from simulated 4 ms patient head-and-neck images was also comparable with scanned 20 ms ones. Compared with fixed-scale technique, the image quality from multiscale one was improved. Conclusion: Use of projection-specific multiscale filters can reach better balance on noise reduction and structure information loss. The image quality of low dose CBCT can be improved by using multiscale filters

Cone beam computed tomography image guidance system for a dedicated intracranial radiosurgery treatment unit.

Science.gov (United States)

Ruschin, Mark; Komljenovic, Philip T; Ansell, Steve; Ménard, Cynthia; Bootsma, Gregory; Cho, Young-Bin; Chung, Caroline; Jaffray, David

2013-01-01

Image guidance has improved the precision of fractionated radiation treatment delivery on linear accelerators. Precise radiation delivery is particularly critical when high doses are delivered to complex shapes with steep dose gradients near critical structures, as is the case for intracranial radiosurgery. To reduce potential geometric uncertainties, a cone beam computed tomography (CT) image guidance system was developed in-house to generate high-resolution images of the head at the time of treatment, using a dedicated radiosurgery unit. The performance and initial clinical use of this imaging system are described. A kilovoltage cone beam CT system was integrated with a Leksell Gamma Knife Perfexion radiosurgery unit. The X-ray tube and flat-panel detector are mounted on a translational arm, which is parked above the treatment unit when not in use. Upon descent, a rotational axis provides 210° of rotation for cone beam CT scans. Mechanical integrity of the system was evaluated over a 6-month period. Subsequent clinical commissioning included end-to-end testing of targeting performance and subjective image quality performance in phantoms. The system has been used to image 2 patients, 1 of whom received single-fraction radiosurgery and 1 who received 3 fractions, using a relocatable head frame. Images of phantoms demonstrated soft tissue contrast visibility and submillimeter spatial resolution. A contrast difference of 35 HU was easily detected at a calibration dose of 1.2 cGy (center of head phantom). The shape of the mechanical flex vs scan angle was highly reproducible and exhibited cone beam CT image guidance system was successfully adapted to a radiosurgery unit. The system is capable of producing high-resolution images of bone and soft tissue. The system is in clinical use and provides excellent image guidance without invasive frames. Copyright © 2013 Elsevier Inc. All rights reserved.

Direct cone beam SPECT reconstruction with camera tilt

International Nuclear Information System (INIS)

Jianying Li; Jaszczak, R.J.; Greer, K.L.; Coleman, R.E.; Zongjian Cao; Tsui, B.M.W.

1993-01-01

A filtered backprojection (FBP) algorithm is derived to perform cone beam (CB) single-photon emission computed tomography (SPECT) reconstruction with camera tilt using circular orbits. This algorithm reconstructs the tilted angle CB projection data directly by incorporating the tilt angle into it. When the tilt angle becomes zero, this algorithm reduces to that of Feldkamp. Experimentally acquired phantom studies using both a two-point source and the three-dimensional Hoffman brain phantom have been performed. The transaxial tilted cone beam brain images and profiles obtained using the new algorithm are compared with those without camera tilt. For those slices which have approximately the same distance from the detector in both tilt and non-tilt set-ups, the two transaxial reconstructions have similar profiles. The two-point source images reconstructed from this new algorithm and the tilted cone beam brain images are also compared with those reconstructed from the existing tilted cone beam algorithm. (author)

Quantitative comparison using Generalized Relative Object Detectability (G-ROD) metrics of an amorphous selenium detector with high resolution Microangiographic Fluoroscopes (MAF) and standard flat panel detectors (FPD).

Science.gov (United States)

Russ, M; Shankar, A; Jain, A; Setlur Nagesh, S V; Ionita, C N; Scott, C; Karim, K S; Bednarek, D R; Rudin, S

2016-02-27

A novel amorphous selenium (a-Se) direct detector with CMOS readout has been designed, and relative detector performance investigated. The detector features include a 25 μ m pixel pitch, and 1000 μ m thick a-Se layer operating at 10V/ μ m bias field. A simulated detector DQE was determined, and used in comparative calculations of the Relative Object Detectability (ROD) family of prewhitening matched-filter (PWMF) observer and non-prewhitening matched filter (NPWMF) observer model metrics to gauge a-Se detector performance against existing high resolution micro-angiographic fluoroscopic (MAF) detectors and a standard flat panel detector (FPD). The PWMF-ROD or ROD metric compares two x-ray imaging detectors in their relative abilities in imaging a given object by taking the integral over spatial frequencies of the Fourier transform of the detector DQE weighted by an object function, divided by the comparable integral for a different detector. The generalized-ROD (G-ROD) metric incorporates clinically relevant parameters (focal-spot size, magnification, and scatter) to show the degradation in imaging performance for detectors that are part of an imaging chain. Preliminary ROD calculations using simulated spheres as the object predicted superior imaging performance by the a-Se detector as compared to existing detectors. New PWMF-G-ROD and NPWMF-G-ROD results still indicate better performance by the a-Se detector in an imaging chain over all sphere sizes for various focal spot sizes and magnifications, although a-Se performance advantages were degraded by focal spot blurring. Nevertheless, the a-Se technology has great potential to provide breakthrough abilities such as visualization of fine details including of neuro-vascular perforator vessels and of small vascular devices.

C-arm Cone Beam Computed Tomographic Needle Path Overlay for Fluoroscopic-Guided Placement of Translumbar Central Venous Catheters

International Nuclear Information System (INIS)

Tam, Alda; Mohamed, Ashraf; Pfister, Marcus; Rohm, Esther; Wallace, Michael J.

2009-01-01

C-arm cone beam computed tomography is an advanced 3D imaging technology that is currently available on state-of-the-art flat-panel-based angiography systems. The overlay of cross-sectional imaging information can now be integrated with real-time fluoroscopy. This overlay technology was used to guide the placement of three percutaneous translumbar inferior vena cava catheters.

Determination of CME 3D parameters based on a new full ice-cream cone model

Science.gov (United States)

Na, Hyeonock; Moon, Yong-Jae

2017-08-01

In space weather forecast, it is important to determine three-dimensional properties of CMEs. Using 29 limb CMEs, we examine which cone type is close to a CME three-dimensional structure. We find that most CMEs have near full ice-cream cone structure which is a symmetrical circular cone combined with a hemisphere. We develop a full ice-cream cone model based on a new methodology that the full ice-cream cone consists of many flat cones with different heights and angular widths. By applying this model to 12 SOHO/LASCO halo CMEs, we find that 3D parameters from our method are similar to those from other stereoscopic methods (i.e., a triangulation method and a Graduated Cylindrical Shell model). In addition, we derive CME mean density (ρmean=Mtotal/Vcone) based on the full ice-cream cone structure. For several limb events, we determine CME mass by applying the Solarsoft procedure (e.g., cme_mass.pro) to SOHO/LASCO C3 images. CME volumes are estimated from the full ice-cream cone structure. From the power-law relationship between CME mean density and its height, we estimate CME mean densities at 20 solar radii (Rs). We will compare the CME densities at 20 Rs with their corresponding ICME densities.

Metallic artifacts from internal scaphoid fracture fixation screws: comparison between C-arm flat-panel, cone-beam, and multidetector computed tomography.

Science.gov (United States)

Finkenstaedt, Tim; Morsbach, Fabian; Calcagni, Maurizio; Vich, Magdalena; Pfirrmann, Christian W A; Alkadhi, Hatem; Runge, Val M; Andreisek, Gustav; Guggenberger, Roman

2014-08-01

The aim of this study was to compare image quality and extent of artifacts from scaphoid fracture fixation screws using different computed tomography (CT) modalities and radiation dose protocols. Imaging of 6 cadaveric wrists with artificial scaphoid fractures and different fixation screws was performed in 2 screw positions (45° and 90° orientation in relation to the x/y-axis) using multidetector CT (MDCT) and 2 flat-panel CT modalities, C-arm flat-panel CT (FPCT) and cone-beam CT (CBCT), the latter 2 with low and standard radiation dose protocols. Mean cartilage attenuation and metal artifact-induced absolute Hounsfield unit changes (= artifact extent) were measured. Two independent radiologists evaluated different image quality criteria using a 5-point Likert-scale. Interreader agreements (Cohen κ) were calculated. Mean absolute Hounsfield unit changes and quality ratings were compared using Friedman and Wilcoxon signed-rank tests. Artifact extent was significantly smaller for MDCT and standard-dose FPCT compared with CBCT low- and standard-dose acquisitions (all P 0.05). Both MDCT and FPCT standard-dose protocols showed equal ratings for screw bone interface, fracture line, and trabecular bone evaluation (P = 0.06, 0.2, and 0.2, respectively) and performed significantly better than FPCT low- and CBCT low- and standard-dose acquisitions (all P < 0.05). Good interreader agreement was found for image quality comparisons (Cohen κ = 0.76-0.78). Both MDCT and FPCT standard-dose acquisition showed comparatively less metal-induced artifacts and better overall image quality compared with FPCT low-dose and both CBCT acquisitions. Flat-panel CT may provide sufficient image quality to serve as a versatile CT alternative for postoperative imaging of internally fixated wrist fractures.

SU-E-T-370: Measurement of Conical Cone Output Factors for the Varian Edge Linear Accelerator

International Nuclear Information System (INIS)

Li, H; Kim, J; Gordon, J; Chetty, I; Wang, S; Zhong, H; Wen, N

2014-01-01

Purpose: To quantify the impact of detector type, SSD/depth, and intermediate reference on conical cone output factor (OF) measurements for the Varian Edge linac. Methods: OF's for 4, 5, 7.5, 10, 12.5, 15, and 17.5 mm diameter cones relative to 10cmx10cm field were measured for the 6X FFF and 10X FFF energies, with jaws set to 5cmx5cm. Measurements were performed with an Edge diode (0.8mmx0.8mmx0.03mm WxLxT), stereotatic diode SFD, photon diode, CC01 and pinpoint chambers (2mm diameter for both). 95cm SSD/5cm depth were used in a water tank. For the measurement with diodes, OF's were cross-referred to CC13 ion chamber measurements with 3cmx3cm field, as recommended, to help mitigate the energy variation in diode response with field size. Results were compared to the representative data from Varian measured with Edge detector. With SFD, OF's at 98.5cm SSD/1.5cm depth and 90cm SSD/10cm depth were also measured. Results: OF's measured with the Edge detector matched within 1.3% (max diff) with the representative data from Varian. For the SFD, OF's matched within 1.3% for the 4, 5 and 17.5 mm cones and within 3.7% for the other cones. OF's with photon diode were within 1.3% except for the 4 and 5 mm cones where they were 8.1% and 3.7%, respectively. OF's for the CC01 and pinpoint chamber deviated up to 36% and 44%, respectively for the 4 mm cone. OF's after intermediate reference with 3cmx3cm field changed by 3.7% for SFD, 0.8% for photon diode, and 0.6% for Edge detector. OF's at 98.5cm SSD/1.5cm depth were 10.8% higher than that at 95cm SSD/5cm depth, and OF's at 90cm SSD/1.5cm depth were 7.5% lower. Conclusion: OF's measured with the Edge detector appear to be reliable. CC01 and pinpoint chambers do not appear suitable for measuring the small cone OF's. SSD/depth affects OF measurements significantly

Comparison of dose and image quality of a Flat-panel detector and an image intensifier; Comparacao da dose e qualidade da imagem de um detector Flatpanel e um intensificador de imagem

Energy Technology Data Exchange (ETDEWEB)

Lazzaro, M.; Friedrich, B.Q.; Luz, R.M. da; Silva, A.M.M. da, E-mail: marcos.lazzaro@acad.pucrs.br [Pontificia Universidade Catolica do Rio Grande do Sul (PUC-RS), Porto Alegre, RS (Brazil)

2016-07-01

With the development of new technologies, have emerged new conversion methods of X-ray image, such as flat panel detectors. The aim of this work is the comparison of entrance surface air kerma (ESAK) and image quality between an image intensifier type of detector (A) and a flat panel (B). The ESAK was obtained by placing a ionization chamber under PMMA simulators of 10, 20 and 30 cm and the image quality was obtained by using the TOR {sup 18}FG simulator. The ESAK to the equipment A is higher when compared to the equipment B. The high contrast resolution is better for the equipment A for all thicknesses of simulators. The equipment A has low contrast resolution with a better viewing threshold for thicknesses of 10 and 20 cm, and a worse performance for 30 cm. It is concluded that the equipment B has ESAK smaller and despite having lower resolution, in almost all cases, have appropriate image quality for diagnosis. (author)

Pile Design Based on Cone Penetration Test Results

OpenAIRE

Salgado, Rodrigo; Lee, Junhwan

1999-01-01

The bearing capacity of piles consists of both base resistance and side resistance. The side resistance of piles is in most cases fully mobilized well before the maximum base resistance is reached. As the side resistance is mobilized early in the loading process, the determination of pile base resistance is a key element of pile design. Static cone penetration is well related to the pile loading process, since it is performed quasi-statically and resembles a scaled-down pile load test. In ord...

Extra-oral dental radiography for disaster victims using a flat panel X-ray detector and a hand-held X-ray generator.

Science.gov (United States)

Ohtani, M; Oshima, T; Mimasaka, S

2017-12-01

Forensic odontologists commonly incise the skin for post-mortem dental examinations when it is difficult to open the victim's mouth. However, it is prohibited by law to incise dead bodies without permission in Japan. Therefore, we attempted using extra-oral dental radiography, using a digital X-ray equipment with rechargeable batteries, to overcome this restriction. A phantom was placed in the prone position on a table, and three plain dental radiographs were used per case: "lateral oblique radiographs" for left and right posterior teeth and a "contact radiograph" for anterior teeth were taken using a flat panel X-ray detector and a hand-held X-ray generator. The resolving power of the images was measured by a resolution test chart, and the scattered X-ray dose was measured using an ionization chamber-type survey meter. The resolving power of the flat panel X-ray detector was 3.0 lp/mm, which was less than that of intra-oral dental methods, but the three extra-oral plain dental radiographs provided the overall dental information from outside of the mouth, and this approach was less time-consuming. In addition, the higher dose of scattered X-rays was laterally distributed, but the dose per case was much less than that of intra-oral dental radiographs. Extra-oral plain dental radiography can be used for disaster victim identification by dental methods even when it is difficult to open the mouth. Portable and rechargeable devices, such as a flat panel X-ray detector and a hand-held X-ray generator, are convenient to bring and use anywhere, even at a disaster scene lacking electricity and water.

Interesting detector shapes for 3rd generation CT

Energy Technology Data Exchange (ETDEWEB)

Kachelriess, Marc [Erlangen-Nuernberg Univ., Erlangen (Germany). Inst. of Medical Physics (IMP)

2011-07-01

Third generation CT scanners typically comprise detectors which are flat or whose shape is the segment of a cylinder or a sphere that is focussed onto the focal spot of the X-ray source. There appear to be two design criteria that favor this choice of detector shape. One is the possibility of performing fan-beam and cone-beam filtered backprojection in the native geometry (without rebinning) and the other criterium is to enable the use of focussed anti scatter grids. It is less known, however, that other detector shapes may also have these properties. While these designs have been evaluated for 2D CT from a rather theoretical standpoint more than one decade ago we revisit and generalize these considerations, extend them to 3D circular, sequential and spiral cone-beam CT and propose an optimal design in terms of detector costs. (orig.)

CSC large panel R ampersand D summary for the SSC GEM muon subsystem

International Nuclear Information System (INIS)

Pratuch, S.M.; Clements, J.W.; Spellman, G.P.

1994-05-01

The GEM Detector uses 1,128 Cathode Strip Chamber (CSC) muon detectors requiring a total of approximately 10,000 precision panels in the CSC assemblies. These panels must be fabricated to extreme tolerances in order to meet the physics requirement. A fabrication technique used to produce two large panels, nominally 1 by 3 meters, is described and the resulting panel precision is reported

A Micromegas-based low-background x-ray detector coupled to a slumped-glass telescope for axion research

DEFF Research Database (Denmark)

Aznar, F.; Castel, J.; Christensen, F. E.

2015-01-01

We report on the design, construction and operation of a low background x-ray detection line composed of a shielded Micromegas detector of the microbulk technology. The detector is made from radiopure materials and is placed at the focal point of a ~ 5 cm diameter, 1.5 m focal-length, cone......-approximation Wolter I x-ray telescope (XRT) assembled from thermally-formed (or "slumped") glass substrates deposited with multilayer coatings. The system has been conceived as a technological pathfinder for the future International Axion Observatory (IAXO), as it combines two of the techniques (optic and detector...

X-ray light valve (XLV): a novel detectors' technology for digital mammography

Science.gov (United States)

Marcovici, Sorin; Sukhovatkin, Vlad; Oakham, Peter

2014-03-01

A novel method, based on X-ray Light Valve (XLV) technology, is proposed for making good image quality yet inexpensive flat panel detectors for digital mammography. The digital mammography markets, particularly in the developing countries, demand quality machines at substantially lower prices than the ones available today. Continuous pressure is applied on x-ray detectors' manufacturers to reduce the flat panel detectors' prices. XLV presents a unique opportunity to achieve the needed price - performance characteristics for direct conversion, x-ray detectors. The XLV based detectors combine the proven, superior, spatial resolution of a-Se with the simplicity and low cost of liquid crystals and optical scanning. The x-ray quanta absorbed by a 200 μm a-Se produce electron - hole pairs that move under an electric field to the top and bottom of a-Se layer. This 2D charge distribution creates at the interface with the liquid crystals a continuous (analog) charge image corresponding to the impinging radiation's information. Under the influence of local electrical charges next to them, the liquid crystals twist proportionally to the charges and vary their light reflectivity. A scanning light source illuminates the liquid crystals while an associated, pixilated photo-detector, having a 42 μm pixel size, captures the light reflected by the liquid crystals and converts it in16 bit words that are transmitted to the machine for image processing and display. The paper will describe a novel XLV, 25 cm x 30 cm, flat panel detector structure and its underlying physics as well as its preliminary performance measured on several engineering prototypes. In particular, the paper will present the results of measuring XLV detectors' DQE, MTF, dynamic range, low contrast resolution and dynamic behavior. Finally, the paper will introduce the new, low cost, XLV detector based, digital mammography machine under development at XLV Diagnostics Inc.

Quantitative image quality evaluation of pixel-binning in a flat-panel detector for x-ray fluoroscopy

International Nuclear Information System (INIS)

Srinivas, Yogesh; Wilson, David L.

2004-01-01

X-ray fluoroscopy places stringent design requirements on new flat-panel (FP) detectors, requiring both low-noise electronics and high data transfer rates. Pixel-binning, wherein data from more that one detector pixel are collected simultaneously, not only lowers the data transfer rate but also increases x-ray counts and pixel signal-to-noise ratio (SNR). In this study, we quantitatively assessed image quality of image sequences from four acquisition methods; no-binning and three types of binning; in synthetic images using a clinically relevant task of detecting an extended guidewire in a four-alternative forced-choice paradigm. Binning methods were conventional data-line (D) and gate-line (G) binning, and a novel method in which alternate frames in an image sequence used D and G binning. Two detector orientations placed the data lines either parallel or perpendicular to the guide wire. At a low exposure of 0.6 μR (1.548x10 -10 C/kg) per frame, irrespective of detector orientation, D binning with its reduced electronic noise was significantly (p -10 C/kg) per frame, with data lines parallel to the guidewire, detection with D binning was significantly (p<0.1) better than G binning. However, with data lines perpendicular to the guidewire, G binning was significantly (p<0.1) better than D binning because the partial area effect was reduced. Alternate binning was the best binning method when results were averaged over both orientations, and it was as good as the best binning method at either orientation. In addition, at low and high exposures, alternate binning gave a temporally fused image with a smooth guidewire, an important image quality feature not assessed in a detection experiment. While at high exposure, detection with no binning was as good, or better, than the best binning method, it might be impractical at fluoroscopy imaging rates. A computational observer model based on signal detection theory successfully fit data and was used to predict effects of

TU-EF-207-05: Dedicated Cone-beam Breast CT

International Nuclear Information System (INIS)

Vedantham, S.

2015-01-01

mode due to lower photon fluence per projection. This may require fast-frame acquisition and symmetric or asymmetric pixel binning in some systems. Recent studies investigated the performance of increased conversion layer thickness for contrast-enhanced imaging of the breast in dual-energy acquisition mode. In other direct conversion detectors operating in the avalanche mode, sensitivities close to the single photon response are also explored for mammography and breast tomosynthesis. The potential advantages and challenges of this approach are described. Dedicated breast CT brings x-ray imaging of the breast to true tomographic 3D imaging. It can eliminate the tissue superposition problem and does not require physical compression of the breast. Using cone beam geometry and a flat-panel detector, several hundred projections are acquired and reconstructed to near isotropic voxels. Multiplanar reconstruction facilitates viewing the breast volume in any desired orientation. Ongoing clinical studies, the current state-of-the art, and research to advance the technology are described. Learning Objectives: To understand the ongoing developments in x-ray imaging of the breast To understand the approaches and applications of spectral mammography To understand the potential advantages of distributed x-ray source arrays for digital breast tomosynthesis To understand the ongoing developments in detector technology for digital mammography and breast tomosynthesis To understand the current state-of-the-art for dedicated cone-beam breast CT and research to advance the technology. Research collaboration with Koning Corporation

TU-EF-207-05: Dedicated Cone-beam Breast CT

Energy Technology Data Exchange (ETDEWEB)

Vedantham, S. [Univ. of Massachusetts Medical School (United States)

2015-06-15

mode due to lower photon fluence per projection. This may require fast-frame acquisition and symmetric or asymmetric pixel binning in some systems. Recent studies investigated the performance of increased conversion layer thickness for contrast-enhanced imaging of the breast in dual-energy acquisition mode. In other direct conversion detectors operating in the avalanche mode, sensitivities close to the single photon response are also explored for mammography and breast tomosynthesis. The potential advantages and challenges of this approach are described. Dedicated breast CT brings x-ray imaging of the breast to true tomographic 3D imaging. It can eliminate the tissue superposition problem and does not require physical compression of the breast. Using cone beam geometry and a flat-panel detector, several hundred projections are acquired and reconstructed to near isotropic voxels. Multiplanar reconstruction facilitates viewing the breast volume in any desired orientation. Ongoing clinical studies, the current state-of-the art, and research to advance the technology are described. Learning Objectives: To understand the ongoing developments in x-ray imaging of the breast To understand the approaches and applications of spectral mammography To understand the potential advantages of distributed x-ray source arrays for digital breast tomosynthesis To understand the ongoing developments in detector technology for digital mammography and breast tomosynthesis To understand the current state-of-the-art for dedicated cone-beam breast CT and research to advance the technology. Research collaboration with Koning Corporation.

Integrated radiotherapy imaging system (IRIS): design considerations of tumour tracking with linac gantry-mounted diagnostic x-ray systems with flat-panel detectors.

Science.gov (United States)

Berbeco, Ross I; Jiang, Steve B; Sharp, Gregory C; Chen, George T; Mostafavi, Hassan; Shirato, Hiroki

2004-01-21

The design of an integrated radiotherapy imaging system (IRIS), consisting of gantry mounted diagnostic (kV) x-ray tubes and fast read-out flat-panel amorphous-silicon detectors, has been studied. The system is meant to be capable of three main functions: radiographs for three-dimensional (3D) patient set-up, cone-beam CT and real-time tumour/marker tracking. The goal of the current study is to determine whether one source/panel pair is sufficient for real-time tumour/marker tracking and, if two are needed, the optimal position of each relative to other components and the isocentre. A single gantry-mounted source/imager pair is certainly capable of the first two of the three functions listed above and may also be useful for the third, if combined with prior knowledge of the target's trajectory. This would be necessary because only motion in two dimensions is visible with a single imager/source system. However, with previously collected information about the trajectory, the third coordinate may be derived from the other two with sufficient accuracy to facilitate tracking. This deduction of the third coordinate can only be made if the 3D tumour/marker trajectory is consistent from fraction to fraction. The feasibility of tumour tracking with one source/imager pair has been theoretically examined here using measured lung marker trajectory data for seven patients from multiple treatment fractions. The patients' selection criteria include minimum mean amplitudes of the tumour motions greater than 1 cm peak-to-peak. The marker trajectory for each patient was modelled using the first fraction data. Then for the rest of the data, marker positions were derived from the imager projections at various gantry angles and compared with the measured tumour positions. Our results show that, due to the three dimensionality and irregular trajectory characteristics of tumour motion, on a fraction-to-fraction basis, a 'monoscopic' system (single source/imager) is inadequate for

Critical condition for the transformation from Taylor cone to cone-jet

International Nuclear Information System (INIS)

Wei Cheng; Zhao Yang; Gang Tie-Qiang; Chen Li-Jie

2014-01-01

An energy method is proposed to investigate the critical transformation condition from a Taylor cone to a cone-jet. Based on the kinetic theorem, the system power allocation and the electrohydrodynamics stability are discussed. The numerical results indicate that the energy of the liquid cone tip experiences a maximum value during the transformation. With the proposed jetting energy, we give the critical transformation condition under which the derivative of jetting energy with respect to the surface area is greater than or equal to the energy required to form a unit of new liquid surface

Study on cosmic ray iron isotopes in an emulsion-plastic detector

International Nuclear Information System (INIS)

Scherzer, R.; Enge, W.; Beaujean, R.; Hertzman, S.; Kristiansson, K.; Soederstroem, K.

1976-01-01

Combining cellulose nitrate plastics and nuclear emulsions a detector system for mass measurement in the iron group has been designed. The detector operates in an energy interval of 500-700 MeV/Nuc and has been flown in two balloon flights. In the emulsion range and track width are measured. Cone lengths and range are measured in the plastics. The charge of a particle can be determined both in emulsion and in plastics. The mass is determined by relating cone lengths to residual range. One advantage of this detector system is the high rejection of interacting particles. The present status is reported. (orig.) [de

Performance evaluation of a retrofit digital detector-based mammography system.

Science.gov (United States)

Marshall, Nicholas W; van Ongeval, Chantal; Bosmans, Hilde

2016-02-01

A retrofit flat panel detector was integrated with a GE DMR+ analog mammography system and characterized using detective quantum efficiency (DQE). Technical system performance was evaluated using the European Guidelines protocol, followed by a limited evaluation of clinical image quality for 20 cases using image quality criteria in the European Guidelines. Optimal anode/filter selections were established using signal difference-to-noise ratio measurements. Only small differences in peak DQE were seen between the three anode/filter settings, with an average value of 0.53. For poly(methyl methacrylate) (PMMA) thicknesses above 60 mm, the Rh/Rh setting was the optimal anode/filter setting. The system required a mean glandular dose of 0.54 mGy at 30 kV Rh/Rh to reach the Acceptable gold thickness limit for 0.1 mm details. Imaging performance of the retrofit unit with the GE DMR+ is notably better than of powder based computed radiography systems and is comparable to current flat panel FFDM systems. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Characterization of Air-Based Photovoltaic Thermal Panels with Bifacial Solar Cells

Directory of Open Access Journals (Sweden)

P. Ooshaksaraei

2013-01-01

Full Text Available Photovoltaic (PV panels account for a majority of the cost of photovoltaic thermal (PVT panels. Bifacial silicon solar panels are attractive for PVT panels because of their potential to enhance electrical power generation from the same silicon wafer compared with conventional monofacial solar panels. This paper examines the performance of air-based bifacial PVT panels with regard to the first and second laws of thermodynamics. Four air-based bifacial PVT panels were designed. The maximum efficiencies of 45% to 63% were observed for the double-path-parallel bifacial PVT panel based on the first law of thermodynamics. Single-path bifacial PVT panel represents the highest exergy efficiency (10%. Double-path-parallel bifacial PVT panel is the second preferred design as it generates up to 20% additional total energy compared with the single-path panel. However, the daily average exergy efficiency of a double-path-parallel panel is 0.35% lower than that of a single-path panel.

CCD-based vertex detectors

CERN Document Server

Damerell, C J S

2005-01-01

Over the past 20 years, CCD-based vertex detectors have been used to construct some of the most precise 'tracking microscopes' in particle physics. They were initially used by the ACCMOR collaboration for fixed target experiments in CERN, where they enabled the lifetimes of some of the shortest-lived charm particles to be measured precisely. The migration to collider experiments was accomplished in the SLD experiment, where the original 120 Mpixel detector was later upgraded to one with 307 Mpixels. This detector was used in a range of physics studies which exceeded the capability of the LEP detectors, including the most precise limit to date on the Bs mixing parameter. This success, and the high background hit densities that will inevitably be encountered at the future TeV-scale linear collider, have established the need for a silicon pixel-based vertex detector at this machine. The technical options have now been broadened to include a wide range of possible silicon imaging technologies as well as CCDs (mon...

An FDK-like cone-beam SPECT reconstruction algorithm for non-uniform attenuated projections acquired using a circular trajectory

International Nuclear Information System (INIS)

Huang, Q; Zeng, G L; You, J; Gullberg, G T

2005-01-01

In this paper, Novikov's inversion formula of the attenuated two-dimensional (2D) Radon transform is applied to the reconstruction of attenuated fan-beam projections acquired with equal detector spacing and of attenuated cone-beam projections acquired with a flat planar detector and circular trajectory. The derivation of the fan-beam algorithm is obtained by transformation from parallel-beam coordinates to fan-beam coordinates. The cone-beam reconstruction algorithm is an extension of the fan-beam reconstruction algorithm using Feldkamp-Davis-Kress's (FDK) method. Computer simulations indicate that the algorithm is efficient and is accurate in reconstructing slices close to the central slice of the cone-beam orbit plane. When the attenuation map is set to zero the implementation is equivalent to the FDK method. Reconstructed images are also shown for noise corrupted projections

Clinical Course, Genetic Etiology, and Visual Outcome in Cone and Cone-Rod Dystrophy

NARCIS (Netherlands)

Thiadens, Alberta A. H. J.; Phan, T. My Lan; Zekveld-Vroon, Renate C.; Leroy, Bart P.; van den Born, L. Ingeborgh; Hoyng, Carel B.; Klaver, Caroline C. W.; Roosing, Susanne; Pott, Jan-Willem R.; van Schooneveld, Mary J.; van Moll-Ramirez, Norka; van Genderen, Maria M.; Boon, Camiel J. F.; den Hollander, Anneke I.; Bergen, Arthur A. B.; De Baere, Elfride; Cremers, Frans P. M.; Lotery, Andrew J.

Objective: To evaluate the clinical course, genetic etiology, and visual prognosis in patients with cone dystrophy (CD) and cone-rod dystrophy (CRD). Design: Clinic-based, longitudinal, multicenter study. Participants: Consecutive probands with CD (N = 98), CRD (N = 83), and affected relatives (N =

The measurement of proton stopping power using proton-cone-beam computed tomography

International Nuclear Information System (INIS)

Zygmanski, P.; Rabin, M.S.Z.; Gall, K.P.; Rosenthal, S.J.

2000-01-01

A cone-beam computed tomography (CT) system utilizing a proton beam has been developed and tested. The cone beam is produced by scattering a 160 MeV proton beam with a modifier that results in a signal in the detector system, which decreases monotonically with depth in the medium. The detector system consists of a Gd 2 O 2 S:Tb intensifying screen viewed by a cooled CCD camera. The Feldkamp-Davis-Kress cone-beam reconstruction algorithm is applied to the projection data to obtain the CT voxel data representing proton stopping power. The system described is capable of reconstructing data over a 16x16x16cm 3 volume into 512x512x512 voxels. A spatial and contrast resolution phantom was scanned to determine the performance of the system. Spatial resolution is significantly degraded by multiple Coulomb scattering effects. Comparison of the reconstructed proton CT values with x-ray CT derived proton stopping powers shows that there may be some advantage to obtaining stopping powers directly with proton CT. The system described suggests a possible practical method of obtaining this measurement in vivo. (author)

Large area x-ray detectors for cargo radiography

Science.gov (United States)

Bueno, C.; Albagli, D.; Bendahan, J.; Castleberry, D.; Gordon, C.; Hopkins, F.; Ross, W.

2007-04-01

Large area x-ray detectors based on phosphors coupled to flat panel amorphous silicon diode technology offer significant advances for cargo radiologic imaging. Flat panel area detectors provide large object coverage offering high throughput inspections to meet the high flow rate of container commerce. These detectors provide excellent spatial resolution when needed, and enhanced SNR through low noise electronics. If the resolution is reduced through pixel binning, further advances in SNR are achievable. Extended exposure imaging and frame averaging enables improved x-ray penetration of ultra-thick objects, or "select-your-own" contrast sensitivity at a rate many times faster than LDAs. The areal coverage of flat panel technology provides inherent volumetric imaging with the appropriate scanning methods. Flat panel area detectors have flexible designs in terms of electronic control, scintillator selection, pixel pitch, and frame rates. Their cost is becoming more competitive as production ramps up for the healthcare, nondestructive testing (NDT), and homeland protection industries. Typically used medical and industrial polycrystalline phosphor materials such as Gd2O2S:Tb (GOS) can be applied to megavolt applications if the phosphor layer is sufficiently thick to enhance x-ray absorption, and if a metal radiator is used to augment the quantum detection efficiency and reduce x-ray scatter. Phosphor layers ranging from 0.2-mm to 1-mm can be "sandwiched" between amorphous silicon flat panel diode arrays and metal radiators. Metal plates consisting of W, Pb or Cu, with thicknesses ranging from 0.25-mm to well over 1-mm can be used by covering the entire area of the phosphor plate. In some combinations of high density metal and phosphor layers, the metal plate provides an intensification of 25% in signal due to electron emission from the plate and subsequent excitation within the phosphor material. This further improves the SNR of the system.

Cone Beam X-ray Luminescence Computed Tomography Based on Bayesian Method.

Science.gov (United States)

Zhang, Guanglei; Liu, Fei; Liu, Jie; Luo, Jianwen; Xie, Yaoqin; Bai, Jing; Xing, Lei

2017-01-01

X-ray luminescence computed tomography (XLCT), which aims to achieve molecular and functional imaging by X-rays, has recently been proposed as a new imaging modality. Combining the principles of X-ray excitation of luminescence-based probes and optical signal detection, XLCT naturally fuses functional and anatomical images and provides complementary information for a wide range of applications in biomedical research. In order to improve the data acquisition efficiency of previously developed narrow-beam XLCT, a cone beam XLCT (CB-XLCT) mode is adopted here to take advantage of the useful geometric features of cone beam excitation. Practically, a major hurdle in using cone beam X-ray for XLCT is that the inverse problem here is seriously ill-conditioned, hindering us to achieve good image quality. In this paper, we propose a novel Bayesian method to tackle the bottleneck in CB-XLCT reconstruction. The method utilizes a local regularization strategy based on Gaussian Markov random field to mitigate the ill-conditioness of CB-XLCT. An alternating optimization scheme is then used to automatically calculate all the unknown hyperparameters while an iterative coordinate descent algorithm is adopted to reconstruct the image with a voxel-based closed-form solution. Results of numerical simulations and mouse experiments show that the self-adaptive Bayesian method significantly improves the CB-XLCT image quality as compared with conventional methods.

Ballistic study of Tensylon®–based panels

Directory of Open Access Journals (Sweden)

L-C. Alil

2018-06-01

Full Text Available Ballistic protection is a matter of interest requested by civilian as well as military needs. The last decade has witnessed an increase in the use of light weight and efficient armour systems. These panels may be used for body protection as well as light vehicle protection against small calibres or to enhance the protection level of heavier vehicles with decreasing or maintaining their weight penalty. Ultra high molecular weight polyethylene is a material of interest for light weight armour applications. The authors designed panels made of hot–pressed Tensylon® in different configurations with thin steel sheets as a backing and shield protection. Comparison of their ballistic performance to the theory predictions reveals the improved ballistic response of the panels. In addition, a non–pressed Tensylon® panel has been tested in order to facilitate the observations of the failure mechanisms inside the panels. Even if not suitable for practical use, such non–pressed panels clearly reveal the dynamic processes at micro–scale that occur during the impact. The failure mechanisms of the material under bullet penetration are discussed based on photography, optical microscopy and scanning electron microscopy. The supposed effects of the panel pressing are discussed based on the observed difference between pressed and non–pressed structures ballistic response.

Dirac cones beyond the honeycomb lattice : a symmetry based approach

NARCIS (Netherlands)

Miert, G. van; de Morais Smith, Cristiane

2016-01-01

Recently, several new materials exhibiting massless Dirac fermions have been proposed. However, many of these do not have the typical graphene honeycomb lattice, which is often associated with Dirac cones. Here, we present a classification of these different two-dimensional Dirac systems based on

Syndromic Panel-Based Testing in Clinical Microbiology.

Science.gov (United States)

Ramanan, Poornima; Bryson, Alexandra L; Binnicker, Matthew J; Pritt, Bobbi S; Patel, Robin

2018-01-01

The recent development of commercial panel-based molecular diagnostics for the rapid detection of pathogens in positive blood culture bottles, respiratory specimens, stool, and cerebrospinal fluid has resulted in a paradigm shift in clinical microbiology and clinical practice. This review focuses on U.S. Food and Drug Administration (FDA)-approved/cleared multiplex molecular panels with more than five targets designed to assist in the diagnosis of bloodstream, respiratory tract, gastrointestinal, or central nervous system infections. While these panel-based assays have the clear advantages of a rapid turnaround time and the detection of a large number of microorganisms and promise to improve health care, they present certain challenges, including cost and the definition of ideal test utilization strategies (i.e., optimal ordering) and test interpretation. Copyright © 2017 American Society for Microbiology.

Registration-based Reconstruction of Four-dimensional Cone Beam Computed Tomography

DEFF Research Database (Denmark)

Christoffersen, Christian; Hansen, David Christoffer; Poulsen, Per Rugaard

2013-01-01

We present a new method for reconstruction of four-dimensional (4D) cone beam computed tomography from an undersampled set of X-ray projections. The novelty of the proposed method lies in utilizing optical flow based registration to facilitate that each temporal phase is reconstructed from the full...

Design and image-quality performance of high resolution CMOS-based X-ray imaging detectors for digital mammography

Science.gov (United States)

Cha, B. K.; Kim, J. Y.; Kim, Y. J.; Yun, S.; Cho, G.; Kim, H. K.; Seo, C.-W.; Jeon, S.; Huh, Y.

2012-04-01

In digital X-ray imaging systems, X-ray imaging detectors based on scintillating screens with electronic devices such as charge-coupled devices (CCDs), thin-film transistors (TFT), complementary metal oxide semiconductor (CMOS) flat panel imagers have been introduced for general radiography, dental, mammography and non-destructive testing (NDT) applications. Recently, a large-area CMOS active-pixel sensor (APS) in combination with scintillation films has been widely used in a variety of digital X-ray imaging applications. We employed a scintillator-based CMOS APS image sensor for high-resolution mammography. In this work, both powder-type Gd2O2S:Tb and a columnar structured CsI:Tl scintillation screens with various thicknesses were fabricated and used as materials to convert X-ray into visible light. These scintillating screens were directly coupled to a CMOS flat panel imager with a 25 × 50 mm2 active area and a 48 μm pixel pitch for high spatial resolution acquisition. We used a W/Al mammographic X-ray source with a 30 kVp energy condition. The imaging characterization of the X-ray detector was measured and analyzed in terms of linearity in incident X-ray dose, modulation transfer function (MTF), noise-power spectrum (NPS) and detective quantum efficiency (DQE).

Recent Developments in GEM-Based Neutron Detectors

International Nuclear Information System (INIS)

Saenboonruang, K.

2014-01-01

The gas electron multiplier (GEM) detector is a relatively new gaseous detector that has been used for less than 20 years. Since the discovery in 1997 by F. Sauli, the GEM detector has shown excellent properties including high rate capability, excellent resolutions, low discharge probability, and excellent radiation hardness. These promising properties have led the GEM detector to gain popularity and attention amongst physicists and researchers. In particular, the GEM detector can also be modified to be used as a neutron detector by adding appropriate neutron converters. With properties stated above and the need to replace the expensive 3 He-based neutron detectors, the GEM-based neutron detector will be one of the most powerful and affordable neutron detectors. Applications of the GEM-based neutron detectors vary from researches in nuclear and particle physics, neutron imaging, and national security. Although several promising progresses and results have been shown and published in the past few years, further improvement is still needed in order to improve the low neutron detection efficiency (only a few percent) and to widen the possibilities for other uses.

Particle Identification in Cherenkov Detectors using Convolutional Neural Networks

CERN Document Server

Theodore, Tomalty

2016-01-01

Cherenkov detectors are used for charged particle identification. When a charged particle moves through a medium faster than light can propagate in that medium, Cherenkov radiation is released in the shape of a cone in the direction of movement. The interior of the Cherenkov detector is instrumented with PMTs to detect this Cherenkov light. Particles, then, can be identified by the shapes of the images on the detector walls.

Iterative reconstruction with attenuation compensation from cone-beam projections acquired via nonplanar orbits

International Nuclear Information System (INIS)

Zeng, G.L.; Weng, Y.; Gullberg, G.T.

1997-01-01

Single photon emission computed tomography (SPECT) imaging with cone-beam collimators provides improved sensitivity and spatial resolution for imaging small objects with large field-of-view detectors. It is known that Tuy's cone-beam data sufficiency condition must be met to obtain artifact-free reconstructions. Even though Tuy's condition was derived for an attenuation-free situation, the authors hypothesize that an artifact-free reconstruction can be obtained even if the cone-beam data are attenuated, provided the imaging orbit satisfies Tuy's condition and the exact attenuation map is known. In the authors' studies, emission data are acquired using nonplanar circle-and-line orbits to acquire cone-beam data for tomographic reconstructions. An extended iterative ML-EM (maximum likelihood-expectation maximization) reconstruction algorithm is derived and used to reconstruct projection data with either a pre-acquired or assumed attenuation map. Quantitative accuracy of the attenuation corrected emission reconstruction is significantly improved

Use and imaging performance of CMOS flat panel imager with LiF/ZnS(Ag) and Gadox scintillation screens for neutron radiography

Science.gov (United States)

Cha, B. K.; kim, J. Y.; Kim, T. J.; Sim, C.; Cho, G.; Lee, D. H.; Seo, C.-W.; Jeon, S.; Huh, Y.

2011-01-01

In digital neutron radiography system, a thermal neutron imaging detector based on neutron-sensitive scintillating screens with CMOS(complementary metal oxide semiconductor) flat panel imager is introduced for non-destructive testing (NDT) application. Recently, large area CMOS APS (active-pixel sensor) in conjunction with scintillation films has been widely used in many digital X-ray imaging applications. Instead of typical imaging detectors such as image plates, cooled-CCD cameras and amorphous silicon flat panel detectors in combination with scintillation screens, we tried to apply a scintillator-based CMOS APS to neutron imaging detection systems for high resolution neutron radiography. In this work, two major Gd2O2S:Tb and 6LiF/ZnS:Ag scintillation screens with various thickness were fabricated by a screen printing method. These neutron converter screens consist of a dispersion of Gd2O2S:Tb and 6LiF/ZnS:Ag scintillating particles in acrylic binder. These scintillating screens coupled-CMOS flat panel imager with 25x50mm2 active area and 48μm pixel pitch was used for neutron radiography. Thermal neutron flux with 6x106n/cm2/s was utilized at the NRF facility of HANARO in KAERI. The neutron imaging characterization of the used detector was investigated in terms of relative light output, linearity and spatial resolution in detail. The experimental results of scintillating screen-based CMOS flat panel detectors demonstrate possibility of high sensitive and high spatial resolution imaging in neutron radiography system.

Cone beam tomography of the heart using single-photon emission-computed tomography

International Nuclear Information System (INIS)

Gullberg, G.T.; Christian, P.E.; Zeng, G.L.; Datz, F.L.; Morgan, H.T.

1991-01-01

The authors evaluated cone beam single-photon emission-computed tomography (SPECT) of the heart. A new cone beam reconstruction algorithm was used to reconstruct data collected from short scan acquisitions (of slightly more than 180 degrees) of a detector anteriorally traversing a noncircular orbit. The less than 360 degrees acquisition was used to minimize the attenuation artifacts that result from reconstructing posterior projections of 201T1 emissions from the heart. The algorithm includes a new method for reconstructing truncated projections of background tissue activity that eliminates reconstruction ring artifacts. Phantom and patient results are presented which compare a high-resolution cone beam collimator (50-cm focal length; 6.0-mm full width at half maximum [FWHM] at 10 cm) to a low-energy general purpose (LEGP) parallel hole collimator (8.2-mm FWHM at 10 cm) which is 1.33 times more sensitive. The cone beam tomographic results are free of reconstruction artifacts and show improved spatial and contrast resolution over that obtained with the LEGP parallel hole collimator. The limited angular sampling restrictions and truncation problems associated with cone beam tomography do not deter from obtaining diagnostic information. However, even though these preliminary results are encouraging, a thorough clinical study is still needed to investigate the specificity and sensitivity of cone beam tomography

Risk-based decisionmaking (Panel)

Energy Technology Data Exchange (ETDEWEB)

Smith, T.H.

1995-12-31

By means of a panel discussion and extensive audience interaction, explore the current challenges and progress to date in applying risk considerations to decisionmaking related to low-level waste. This topic is especially timely because of the proposed legislation pertaining to risk-based decisionmaking and because of the increased emphasis placed on radiological performance assessments of low-level waste disposal.

Cardiac single-photon emission-computed tomography using combined cone-beam/fan-beam collimation

International Nuclear Information System (INIS)

Gullberg, Grant T.; Zeng, Gengsheng L.

2004-01-01

The objective of this work is to increase system sensitivity in cardiac single-photon emission-computed tomography (SPECT) studies without increasing patient imaging time. For imaging the heart, convergent collimation offers the potential of increased sensitivity over that of parallel-hole collimation. However, if a cone-beam collimated gamma camera is rotated in a planar orbit, the projection data obtained are not complete. Two cone-beam collimators and one fan-beam collimator are used with a three-detector SPECT system. The combined cone-beam/fan-beam collimation provides a complete set of data for image reconstruction. The imaging geometry is evaluated using data acquired from phantom and patient studies. For the Jaszazck cardiac torso phantom experiment, the combined cone-beam/fan-beam collimation provided 1.7 times greater sensitivity than standard parallel-hole collimation (low-energy high-resolution collimators). Also, phantom and patient comparison studies showed improved image quality. The combined cone-beam/fan-beam imaging geometry with appropriate weighting of the two data sets provides improved system sensitivity while measuring sufficient data for artifact free cardiac images

Micro-motion Recognition of Spatial Cone Target Based on ISAR Image Sequences

Directory of Open Access Journals (Sweden)

Changyong Shu

2016-04-01

Full Text Available The accurate micro-motions recognition of spatial cone target is the foundation of the characteristic parameter acquisition. For this reason, a micro-motion recognition method based on the distinguishing characteristics extracted from the Inverse Synthetic Aperture Radar (ISAR sequences is proposed in this paper. The projection trajectory formula of cone node strong scattering source and cone bottom slip-type strong scattering sources, which are located on the spatial cone target, are deduced under three micro-motion types including nutation, precession, and spinning, and the correctness is verified by the electromagnetic simulation. By comparison, differences are found among the projection of the scattering sources with different micro-motions, the coordinate information of the scattering sources in the Inverse Synthetic Aperture Radar sequences is extracted by the CLEAN algorithm, and the spinning is recognized by setting the threshold value of Doppler. The double observation points Interacting Multiple Model Kalman Filter is used to separate the scattering sources projection of the nutation target or precession target, and the cross point number of each scattering source’s projection track is used to classify the nutation or precession. Finally, the electromagnetic simulation data are used to verify the effectiveness of the micro-motion recognition method.

Task-driven image acquisition and reconstruction in cone-beam CT

International Nuclear Information System (INIS)

Gang, Grace J; Stayman, J Webster; Siewerdsen, Jeffrey H; Ehtiati, Tina

2015-01-01

This work introduces a task-driven imaging framework that incorporates a mathematical definition of the imaging task, a model of the imaging system, and a patient-specific anatomical model to prospectively design image acquisition and reconstruction techniques to optimize task performance. The framework is applied to joint optimization of tube current modulation, view-dependent reconstruction kernel, and orbital tilt in cone-beam CT. The system model considers a cone-beam CT system incorporating a flat-panel detector and 3D filtered backprojection and accurately describes the spatially varying noise and resolution over a wide range of imaging parameters in the presence of a realistic anatomical model. Task-based detectability index (d′) is incorporated as the objective function in a task-driven optimization of image acquisition and reconstruction techniques. The orbital tilt was optimized through an exhaustive search across tilt angles ranging ±30°. For each tilt angle, the view-dependent tube current and reconstruction kernel (i.e. the modulation profiles) that maximized detectability were identified via an alternating optimization. The task-driven approach was compared with conventional unmodulated and automatic exposure control (AEC) strategies for a variety of imaging tasks and anthropomorphic phantoms. The task-driven strategy outperformed the unmodulated and AEC cases for all tasks. For example, d′ for a sphere detection task in a head phantom was improved by 30% compared to the unmodulated case by using smoother kernels for noisy views and distributing mAs across less noisy views (at fixed total mAs) in a manner that was beneficial to task performance. Similarly for detection of a line-pair pattern, the task-driven approach increased d′ by 80% compared to no modulation by means of view-dependent mA and kernel selection that yields modulation transfer function and noise-power spectrum optimal to the task. Optimization of orbital tilt identified the

Analytically derived weighting factors for transmission tomography cone beam projections

International Nuclear Information System (INIS)

Yao Weiguang; Leszczynski, Konrad

2009-01-01

Weighting factors, which define the contributions of individual voxels of a 3D object to individual projection elements (pixels) on the detector, are the basic elements required in iterative tomographic reconstructions from transmission projections. Exact or as accurate as possible values for weighting factors are required in high-resolution reconstructions. Geometric complexity of the problem, however, makes it difficult to obtain exact weighting factor values. In this work, we derive an analytical expression for the weighting factors in cone beam projection geometry. The resulting formula is validated and applied to reconstruction from mega and kilovoltage x-ray cone beam projections. The reconstruction speed and accuracy are significantly improved by using the weighting factor values.

Cold knife cone biopsy

Science.gov (United States)

... biopsy; Pap smear - cone biopsy; HPV - cone biopsy; Human papilloma virus - cone biopsy; Cervix - cone biopsy; Colposcopy - cone biopsy Images Female reproductive anatomy Cold cone biopsy Cold cone removal References Baggish ...

Fundamentals of cone beam computed tomography for a prosthodontist

Directory of Open Access Journals (Sweden)

George Puthenpurayil John

2015-01-01

Full Text Available Cone beam computed tomography (CBCT, also referred to as C-arm computed tomography [CT], cone beam volume CT, or flat panel CT is a medical imaging technique of X-ray CT where the X-rays are divergent, forming a cone. [1] CBCT systems have been designed for imaging hard tissues of the maxillofacial region. CBCT is capable of providing sub-millimeter resolution in images of high diagnostic quality, with short scanning times (10-70 s and radiation dosages reportedly up to 15-100 times lower than those of conventional CT scans. Increasing availability of this technology provides the dental clinician with an imaging modality capable of providing a three-dimensional representation of the maxillofacial skeleton with minimal distortion. The aim of this article is to sensitize the Prosthodontist to CBCT technology, provide an overview of currently available maxillofacial CBCT systems and review the specific application of various CBCT display modes to clinical Prosthodontic practice. A MEDLINE search for relevant articles in this specific area of interest was conducted. The selected articles were critically reviewed and the data acquired were systematically compiled.

Fundamentals of cone beam computed tomography for a prosthodontist

Science.gov (United States)

John, George Puthenpurayil; Joy, Tatu Elenjickal; Mathew, Justin; Kumar, Vinod R. B.

2015-01-01

Cone beam computed tomography (CBCT, also referred to as C-arm computed tomography [CT], cone beam volume CT, or flat panel CT) is a medical imaging technique of X-ray CT where the X-rays are divergent, forming a cone.[1] CBCT systems have been designed for imaging hard tissues of the maxillofacial region. CBCT is capable of providing sub-millimeter resolution in images of high diagnostic quality, with short scanning times (10–70 s) and radiation dosages reportedly up to 15–100 times lower than those of conventional CT scans. Increasing availability of this technology provides the dental clinician with an imaging modality capable of providing a three-dimensional representation of the maxillofacial skeleton with minimal distortion. The aim of this article is to sensitize the Prosthodontist to CBCT technology, provide an overview of currently available maxillofacial CBCT systems and review the specific application of various CBCT display modes to clinical Prosthodontic practice. A MEDLINE search for relevant articles in this specific area of interest was conducted. The selected articles were critically reviewed and the data acquired were systematically compiled. PMID:26929479

The ZEUS central tracking detector. Der zentrale Spuren-Detektor von ZEUS

Energy Technology Data Exchange (ETDEWEB)

Saxon, D H

1989-12-01

The Central Tracking Detector (CTD) of ZEUS covers a wide angular range, whilst the Forward Detector - comprising the Forward Tracking Detector (FTD) and electron identification by transition radiation - concentrates on the important forward cone. The RTD (Rear Tracking Detector) provides accurate angle measurement of the recoil electron and the vertex detector (VXD) aims to find particles from heavy flavour decay. To measure momentum accurately the CTD sits in a high magnetic field (B=1,8 T) within the ZEUS calorimeter. (orig./HSI).

Characteristics of kilovoltage x-ray beams used for cone-beam computed tomography in radiation therapy

International Nuclear Information System (INIS)

Ding, George X; Duggan, Dennis M; Coffey, Charles W

2007-01-01

The purpose of this investigation is to characterize the beams produced by a kilovoltage (kV) imager integrated into a linear accelerator (Varian on-board imager integrated into the Trilogy accelerator) for acquiring high resolution volumetric cone-beam computed tomography (CBCT) images of the patient on the treatment table. The x-ray tube is capable of generating photon spectra with kVp values between 40 and 125 kV. The Monte Carlo simulations were used to study the characteristics of kV beams and the properties of imaged target scatters. The Monte Carlo results were benchmarked against measurements, and excellent agreements were obtained. We also studied the effect of including the electron impact ionization (EII), and the simulation showed that the characteristic radiation is increased significantly in the energy spectra when EII is included. Although only slight beam hardening is observed in the spectra of all photons after passing through the phantom target, there is a significant difference in the spectra and angular distributions between scattered and primary photons. The results also show that the photon fluence distributions are significantly altered by adding bow tie filters. The results indicate that a combination of large cone-beam field size and large imaged target significantly increases scatter-to-primary ratios for photons that reach the detector panel. For phantoms 10 cm, 20 cm and 30 cm thick of water placed at the isocentre, the scatter-to-primary ratios are 0.94, 3.0 and 7.6 respectively for an open 125 kVp CBCT beam. The Monte Carlo simulations show that the increase of the scatter is proportional to the increase of the imaged volume, and this also applies to scatter-to-primary ratios. This study shows both the magnitude and the characteristics of scattered x-rays. The knowledge obtained from this investigation may be useful in the future design of the image detector to improve the image quality

Vertical microbial community variability of carbonate-based cones may provide insight into ancient conical stromatolite formation

Science.gov (United States)

Bradley, James; Daille, Leslie; Trivedi, Christopher; Bojanowski, Caitlin; Nunn, Heather; Stamps, Blake; Johnson, Hope; Stevenson, Bradley; Berelson, Will; Corsetti, Frank; Spear, John

2016-04-01

Stromatolite morphogenesis is poorly understood, and the process by which microbial mats become mineralized is a primary question in microbialite formation. Ancient conical stromatolites are primarily carbonate-based whereas the few modern analogues in hot springs are either non-mineralized or mineralized by silica. A team from the 2015 International GeoBiology Course investigated carbonate-rich microbial cones from near Little Hot Creek (LHC), Long Valley Caldera, California, to investigate how conical stromatolites might form in a hot spring carbonate system. The cones rise up from a layered microbial mat on the east side of a 45° C pool with very low flow that is super-saturated with respect to CaCO3. Cone structures are 8-30 mm in height, are rigid and do not deform when removed from the pool. Morphological characterization through environmental scanning electronic microscopy revealed that the cone structure is maintained by a matrix of intertwining microbial filaments around carbonate grains. This matrix gives rise to cone-filaments that are arranged vertically or horizontally, and provides further stability to the cone. Preliminary 16S rRNA gene analysis indicated variability of community composition between different vertical levels of the cone. The cone tip had comparatively greater abundance of filamentous cyanobacteria including Leptolingbya, Phormidium and Isosphaera and fewer heterotrophs (e.g. Chloroflexi) compared to the cone bottom. This supports the hypothesis that cone formation may depend on the differential abundance of the microbial community and their potential functional roles. Metagenomic analyses of the cones revealed potential genes related to chemotaxis and motility. Specifically, a genomic bin identified as a member of the genus Isosphaera contained an hmp chemotaxis operon implicated in gliding motility in the cyanobacterium Nostoc punctiforme. Isosphaera is a Planctomycete shown to have phototactic capabilities, and may play a role in

New detectors technology for radiology imaging

International Nuclear Information System (INIS)

Cuzin, M.; Peyret, O.

1998-01-01

We summarize the main parameters which describes the radiological image at first and the advantages of pixel detectors. All detectors converts X-rays in charges either with an intermediate step with light or directly in a semi-conductor media. That is true for tomography which is the first domain where digital processing have been taken in account and for radiology where flat panel are now proposed to radiologists. Nevertheless, luminescent stimulated screens are a good way to prepare users with digital radiography. As such technique is not valuable for dynamic acquisition, we describe systems which used standard luminescent screens with CCD cameras or with IIR. Some description and comparison of flat panel independent pixel detectors are given. (authors)

Imaging responses of on-site CsI and Gd2O2S flat-panel detectors: Dependence on the tube voltage

Science.gov (United States)

Jeon, Hosang; Chung, Myung Jin; Youn, Seungman; Nam, Jiho; Lee, Jayoung; Park, Dahl; Kim, Wontaek; Ki, Yongkan; Kim, Ho Kyung

2015-07-01

One of the emerging issues in radiography is low-dose imaging to minimize patient's exposure. The scintillating materials employed in most indirect flat-panel detectors show a drastic change of X-ray photon absorption efficiency around their K-edge energies that consequently affects image quality. Using various tube voltages, we investigated the imaging performance of most popular scintillators: cesium iodide (CsI) and gadolinium oxysulfide (Gd2O2S). The integrated detective quantum efficiencies (iDQE) of four detectors installed in the same hospital were evaluated according to the standardized procedure IEC 62220-1 at tube voltages of 40 - 120 kVp. The iDQE values of the Gd2O2S detectors were normalized by those of CsI detectors to exclude the effects of image postprocessing. The contrast-to-noise ratios (CNR) were also evaluated by using an anthropomorphic chest phantom. The iDQE of the CsI detector outperformed that of the Gd2O2S detector over all tube voltages. Moreover, we noted that the iDQE of the Gd2O2S detectors quickly rolled off with decreasing tube voltage under 70 kVp. The CNRs of the two scintillators were similar at 120 kVp. At 60 kVp, however, the CNR of Gd2O2S was about half that of CsI. Compared to the Gd2O2S detectors, variations in the DQE performance of the CsI detectors were relatively immune to variations in the applied tube voltages. Therefore, we claim that Gd2O2S detectors are inappropriate for use in low-tube-voltage imaging (e.g., extremities and pediatrics) with low patient exposure.

Comparison between radiation exposure levels using an image intensifier and a flat-panel detector-based system in image-guided central venous catheter placement in children weighing less than 10 kg

Energy Technology Data Exchange (ETDEWEB)

Miraglia, Roberto; Maruzzelli, Luigi; Cortis, Kelvin; Gerasia, Roberta; Maggio, Simona; Luca, Angelo [Diagnostic and Therapeutic Services, Mediterranean Institute for Transplantation and Advanced Specialized Therapies (ISMETT), Palermo (Italy); Piazza, Marcello [Department of Anesthesia, Mediterranean Institute for Transplantation and Advanced Specialized Therapies (ISMETT), Palermo (Italy); Tuzzolino, Fabio [Department of Information Technology, Mediterranean Institute for Transplantation and Advanced Specialized Therapies (ISMETT), Palermo (Italy)

2014-09-10

Ultrasound-guided central venous puncture and fluoroscopic guidance during central venous catheter (CVC) positioning optimizes technical success and lowers the complication rates in children, and is therefore considered standard practice. The purpose of this study was to compare the radiation exposure levels recorded during CVC placement in children weighing less than 10 kg in procedures performed using an image intensifier-based angiographic system (IIDS) to those performed in a flat-panel detector-based interventional suite (FPDS). A retrospective review of 96 image-guided CVC placements, between January 2008 and October 2013, in 49 children weighing less than 10 kg was performed. Mean age was 8.2 ± 4.4 months (range: 1-22 months). Mean weight was 7.1 ± 2.7 kg (range: 2.5-9.8 kg). The procedures were classified into two categories: non-tunneled and tunneled CVC placement. Thirty-five procedures were performed with the IIDS (21 non-tunneled CVC, 14 tunneled CVC); 61 procedures were performed with the FPDS (47 non-tunneled CVC, 14 tunneled CVC). For non-tunneled CVC, mean DAP was 113.5 ± 126.7 cGy cm{sup 2} with the IIDS and 15.9 ± 44.6 cGy . cm{sup 2} with the FPDS (P < 0.001). For tunneled CVC, mean DAP was 84.6 ± 81.2 cGy . cm{sup 2} with the IIDS and 37.1 ± 33.5 cGy cm{sup 2} with the FPDS (P = 0.02). The use of flat-panel angiographic equipment reduces radiation exposure in small children undergoing image-guided CVC placement. (orig.)

Gain and offset calibration reduces variation in exposure-dependent SNR among systems with identical digital flat-panel detectors.

Science.gov (United States)

Willis, Charles E; Vinogradskiy, Yevgeniy Y; Lofton, Brad K; White, R Allen

2011-07-01

The conditions under which vendor performance criteria for digital radiography systems are obtained do not adequately simulate the conditions of actual clinical imaging with respect to radiographic technique factors, scatter production, and scatter control. Therefore, the relationship between performance under ideal conditions and performance in clinical practice remains unclear. Using data from a large complement of systems in clinical use, the authors sought to develop a method to establish expected performance criteria for digital flat-panel radiography systems with respect to signal-to-noise ratio (SNR) versus detector exposure under clinical conditions for thoracic imaging. The authors made radiographic exposures of a patient-equivalent chest phantom at 125 kVp and 180 cm source-to-image distance. The mAs value was modified to produce exposures above and below the mAs delivered by automatic exposure control. Exposures measured free-in-air were corrected to the imaging plane by the inverse square law, by the attenuation factor of the phantom, and by the Bucky factor of the grid for the phantom, geometry, and kilovolt peak. SNR was evaluated as the ratio of the mean to the standard deviation (SD) of a region of interest automatically selected in the center of each unprocessed image. Data were acquired from 18 systems, 14 of which were tested both before and after gain and offset calibration. SNR as a function of detector exposure was interpolated using a double logarithmic function to stratify the data into groups of 0.2, 0.5, 1.0, 2.0, and 5.0 mR exposure (1.8, 4.5, 9.0, 18, and 45 microGy air KERMA) to the detector. The mean SNR at each exposure interval after calibration exhibited linear dependence on the mean SNR before calibration (r2=0.9999). The dependence was greater than unity (m = 1.101 +/- 0.006), and the difference from unity was statistically significant (p grid replacement. The nonconformant behavior of the other system was corrected by replacing

Musculoskeletal imaging with a prototype photon-counting detector.

Science.gov (United States)

Gruber, M; Homolka, P; Chmeissani, M; Uffmann, M; Pretterklieber, M; Kainberger, F

2012-01-01

To test a digital imaging X-ray device based on the direct capture of X-ray photons with pixel detectors, which are coupled with photon-counting readout electronics. The chip consists of a matrix of 256 × 256 pixels with a pixel pitch of 55 μm. A monolithic image of 11.2 cm × 7 cm was obtained by the consecutive displacement approach. Images of embalmed anatomical specimens of eight human hands were obtained at four different dose levels (skin dose 2.4, 6, 12, 25 μGy) with the new detector, as well as with a flat-panel detector. The overall rating scores for the evaluated anatomical regions ranged from 5.23 at the lowest dose level, 6.32 at approximately 6 μGy, 6.70 at 12 μGy, to 6.99 at the highest dose level with the photon-counting system. The corresponding rating scores for the flat-panel detector were 3.84, 5.39, 6.64, and 7.34. When images obtained at the same dose were compared, the new system outperformed the conventional DR system at the two lowest dose levels. At the higher dose levels, there were no significant differences between the two systems. The photon-counting detector has great potential to obtain musculoskeletal images of excellent quality at very low dose levels.

Derivation and implementation of a cone-beam reconstruction algorithm for nonplanar orbits

International Nuclear Information System (INIS)

Kudo, Hiroyuki; Saito, Tsuneo

1994-01-01

Smith and Grangeat derived a cone-beam inversion formula that can be applied when a nonplanar orbit satisfying the completeness condition is used. Although Grangeat's inversion formula is mathematically different from Smith's, they have similar overall structures to each other. The contribution of this paper is two-fold. First, based on the derivation of Smith, the authors point out that Grangeat's inversion formula and Smith's can be conveniently described using a single formula (the Smith-Grangeat inversion formula) that is in the form of space-variant filtering followed by cone-beam backprojection. Furthermore, the resulting formula is reformulated for data acquisition systems with a planar detector to obtain a new reconstruction algorithm. Second, the authors make two significant modifications to the new algorithm to reduce artifacts and numerical errors encountered in direct implementation of the new algorithm. As for exactness of the new algorithm, the following fact can be stated. The algorithm based on Grangeat's intermediate function is exact for any complete orbit, whereas that based on Smith's intermediate function should be considered as an approximate inverse excepting the special case where almost every plane in 3-D space meets the orbit. The validity of the new algorithm is demonstrated by simulation studies

Comparison of CT numbers between cone-beam CT and multi-detector CT

International Nuclear Information System (INIS)

Kim, Dong Soo; Han, Won Jeong; Kim, Eun Kyung

2010-01-01

To compare the CT numbers on 3 cone-beam CT (CBCT) images with those on multi-detector CT (MDCT) image using CT phantom and to develop linear regressive equations using CT numbers to material density for all the CT scanner each. Mini CT phantom comprised of five 1 inch thick cylindrical models with 1.125 inches diameter of materials with different densities (polyethylene, polystyrene, plastic water, nylon and acrylic) was used. It was scanned in 3 CBCTs (i-CAT, Alphard VEGA, Implagraphy SC) and 1 MDCT (Somatom Emotion). The images were saved as DICOM format and CT numbers were measured using OnDemand 3D. CT numbers obtained from CBCTs and MDCT images were compared and linear regression analysis was performed for the density, ρ(g/cm 3 ), as the dependent variable in terms of the CT numbers obtained from CBCTs and MDCT images. CT numbers on i-CAT and Implagraphy CBCT images were smaller than those on Somatom Emotion MDCT image (p<0.05). Linear relationship on a range of materials used for this study were ρ=0.001 H+1.07 with R2 value of 0.999 for Somatom Emotion, ρ=0.002 H+1.09 with R2 value of 0.991 for Alphard VEGA, ρ=0.001 H+1.43 with R2 value of 0.980 for i-CAT and ρ=0.001 H+1.30 with R2 value of 0.975 for Implagraphy. CT numbers on i-CAT and Implagraphy CBCT images were not same as those on Somatom Emotion MDCT image. The linear regressive equations to determine the density from the CT numbers with very high correlation coefficient were obtained on three CBCT and MDCT scan.

Comparison of CT numbers between cone-beam CT and multi-detector CT

Energy Technology Data Exchange (ETDEWEB)

Kim, Dong Soo; Han, Won Jeong; Kim, Eun Kyung [Department of Oral and Maxillofacial Radiology, School of Dentistry, Dankook University, Cheonan (Korea, Republic of)

2010-06-15

To compare the CT numbers on 3 cone-beam CT (CBCT) images with those on multi-detector CT (MDCT) image using CT phantom and to develop linear regressive equations using CT numbers to material density for all the CT scanner each. Mini CT phantom comprised of five 1 inch thick cylindrical models with 1.125 inches diameter of materials with different densities (polyethylene, polystyrene, plastic water, nylon and acrylic) was used. It was scanned in 3 CBCTs (i-CAT, Alphard VEGA, Implagraphy SC) and 1 MDCT (Somatom Emotion). The images were saved as DICOM format and CT numbers were measured using OnDemand 3D. CT numbers obtained from CBCTs and MDCT images were compared and linear regression analysis was performed for the density, {rho}(g/cm{sup 3}), as the dependent variable in terms of the CT numbers obtained from CBCTs and MDCT images. CT numbers on i-CAT and Implagraphy CBCT images were smaller than those on Somatom Emotion MDCT image (p<0.05). Linear relationship on a range of materials used for this study were {rho}=0.001 H+1.07 with R2 value of 0.999 for Somatom Emotion, {rho}=0.002 H+1.09 with R2 value of 0.991 for Alphard VEGA, {rho}=0.001 H+1.43 with R2 value of 0.980 for i-CAT and {rho}=0.001 H+1.30 with R2 value of 0.975 for Implagraphy. CT numbers on i-CAT and Implagraphy CBCT images were not same as those on Somatom Emotion MDCT image. The linear regressive equations to determine the density from the CT numbers with very high correlation coefficient were obtained on three CBCT and MDCT scan.

WE-EF-207-06: Dedicated Cone-Beam Breast CT with Laterally-Shifted Detector: Monte Carlo Evaluation of X-Ray Scatter Distribution and Scatter-To-Primary Ratio

International Nuclear Information System (INIS)

Shi, L; Vedantham, S; Karellas, A

2015-01-01

Purpose: To determine the spatial distribution of x-ray scatter and scatter-to-primary ratio (SPR) in projections during cone-beam breast CT (CBBCT) with laterally-shifted detector that results in coronal (fan-angle) truncation. Methods: We hypothesized that CBBCT with coronal truncation would lower SPR due to reduction in irradiated breast volume, and that the location of maximum x-ray scatter fluence (scatter-peak) in the detector plane can be determined from the ratio of irradiated-to-total breast volume, breast dimensions and system geometry. Monte Carlo simulations (GEANT4) reflecting a prototype CBBCT system were used to record the position-dependent primary and scatter x-ray photon fluence incident on the detector without coronal truncation (full fan-angle, 2f=24-degrees) and with coronal truncation (fan-angle, f+ f=12+2.7-degrees). Semi-ellipsoidal breasts (10/14/18-cm diameter, chest-wall to nipple length: 0.75xdiameter, 2%/14%/100% fibroglandular content) aligned with the axis-of-rotation (AOR) were modeled. Mono-energy photons were simulated and weighted for 2 spectra (49kVp, 1.4-mm Al HVL; 60kVp, 3.76-mm Al HVL). In addition to SPR, the scatter maps were analyzed to identify the location of the scatter-peak. Results: For CBBCT without fan-angle truncation, the scatter-peaks were aligned with the projection of the AOR onto the detector for all breasts. With truncated fan-beam, the scatter-peaks were laterally-shifted from the projection of the AOR along the fan-angle direction by 14/38/70-pixels for 10/14/18-cm diameter breasts. The corresponding theoretical shifts were 14.8/39.7/68-pixels (p=0.47, 2-tailed paired-ratio t-test). Along the cone-angle, the shift in scatter-peaks between truncated and full-fan angle CBBCT were 2/2/4 -pixels for 10/14/18-cm diameter breasts. CBBCT with fan-angle truncation reduced SPR by 14/22/28% for 10/14/18-cm diameter breasts. 60kVp reduced SPR by 21–25% compared to 49kVp. Peak SPR for CBBCT with fan-angle truncation

Use of RI-cone penetrometer in clay foundations

International Nuclear Information System (INIS)

Mimura, Mamoru; Shibata, Toru; Shrivastava, A.K.

1993-01-01

RI cone penetrometer tests are carried out at four different sites. The foundation grounds discussed here mainly consist of clayey materials. The measured results by RI cone penetrometers are shown for Kyobashi, Hachirougata, Kurihama and Kinkai Bay site. According to comparison of water content and density profiles by RI cone measurement with the conventional testing results, RI cone penetrometers are proved to be versatile tools for site investigation. Settlement assessment by RI cone penetrometer is also discussed by exemplifying the embankment at Kinkai Bay site. Elasto-vis-coplastic finite element analysis correspondingly performed strongly supports the RI cone based assessment. Repeated use of RI cone penetrometer with the advance of construction enables us to assess the consolidation process of the clay foundation. (author)

Efficacy and safety of balloon pulmonary angioplasty for chronic thromboembolic pulmonary hypertension guided by cone-beam computed tomography and electrocardiogram-gated area detector computed tomography

Energy Technology Data Exchange (ETDEWEB)

Ogo, Takeshi, E-mail: ogo.takeshi.hp@mail.ncvc.go.jp [Division of Pulmonary Circulation, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Centre, Osaka (Japan); Department of Advanced Mediccal Research for Pulmonary Hypertension, National Cerebral and Cardiovascular Centre, Osaka (Japan); Fukuda, Tetsuya [Department of Radiology, National Cerebral and Cardiovascular Centre, Osaka (Japan); Tsuji, Akihiro; Fukui, Shigefumi; Ueda, Jin [Division of Pulmonary Circulation, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Centre, Osaka (Japan); Sanda, Yoshihiro [Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Centre, Osaka (Japan); Morita, Yoshiaki [Department of Radiology, National Cerebral and Cardiovascular Centre, Osaka (Japan); Asano, Ryotaro; Konagai, Nao [Division of Pulmonary Circulation, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Centre, Osaka (Japan); Yasuda, Satoshi [Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Centre, Osaka (Japan)

2017-04-15

Highlights: • Recent advancement in CT enables distal CTEpH lesions to be visualized. • We investigated the efficacy and safety of BPA guided by CBCT or ECG-gated area detector CT. • BPA guided by CBCT or ECG-gated area detector CT is effective and safe in patients with CTEpH . • These new advanced CT techniques may be useful in pre-BPA target lesion assessment. - Abstract: Background: Chronic thromboembolic pulmonary hypertension (CTEPH) is a disease characterized by chronic obstructive thrombus and pulmonary hypertension. Balloon pulmonary angioplasty (BPA), an emerging alternative catheter-based treatment for inoperable patients with CTEPH, has not yet been standardised, especially for lesion assessment in distal pulmonary arteries. Recent advancement in computed tomography enables distal CTEPH lesions to be visualized. Methods: We retrospectively studied 80 consecutive patients with inoperable CTEPH who received BPA guided by cone-beam computed tomography (CT) (CBCT) or electrocardiogram (ECG)-gated area detector CT (ADCT) for target lesion assessment. We collected clinical and hemodynamic data, including procedural complications, before BPA and at 3 months and 1 year after BPA. Results: Three hundred eight-five BPA sessions (4.8 sessions/patient) were performed for the lesions of subsegmental arteries (1155 lesions), segmental arteries (738 lesions), and lobar arteries (4 lesions) identified by CBCT or ECG-gated ADCT. Significant improvements in the symptoms, 6-min walk distance, brain natriuretic peptide level, exercise capacity, and haemodynamics were observed 3 months and 1 year after BPA. No cases of death or cardiogenic shock with a low rate of severe wire perforation (0.3%) and severe reperfusion oedema (0.3%) were observed. Conclusions: BPA guided by CBCT or ECG-gated ADCT is effective and remarkably safe in patients with CTEPH . These new advanced CT techniques may be useful in pre-BPA target lesion assessment.

Efficacy and safety of balloon pulmonary angioplasty for chronic thromboembolic pulmonary hypertension guided by cone-beam computed tomography and electrocardiogram-gated area detector computed tomography

International Nuclear Information System (INIS)

Ogo, Takeshi; Fukuda, Tetsuya; Tsuji, Akihiro; Fukui, Shigefumi; Ueda, Jin; Sanda, Yoshihiro; Morita, Yoshiaki; Asano, Ryotaro; Konagai, Nao; Yasuda, Satoshi

2017-01-01

Highlights: • Recent advancement in CT enables distal CTEpH lesions to be visualized. • We investigated the efficacy and safety of BPA guided by CBCT or ECG-gated area detector CT. • BPA guided by CBCT or ECG-gated area detector CT is effective and safe in patients with CTEpH . • These new advanced CT techniques may be useful in pre-BPA target lesion assessment. - Abstract: Background: Chronic thromboembolic pulmonary hypertension (CTEPH) is a disease characterized by chronic obstructive thrombus and pulmonary hypertension. Balloon pulmonary angioplasty (BPA), an emerging alternative catheter-based treatment for inoperable patients with CTEPH, has not yet been standardised, especially for lesion assessment in distal pulmonary arteries. Recent advancement in computed tomography enables distal CTEPH lesions to be visualized. Methods: We retrospectively studied 80 consecutive patients with inoperable CTEPH who received BPA guided by cone-beam computed tomography (CT) (CBCT) or electrocardiogram (ECG)-gated area detector CT (ADCT) for target lesion assessment. We collected clinical and hemodynamic data, including procedural complications, before BPA and at 3 months and 1 year after BPA. Results: Three hundred eight-five BPA sessions (4.8 sessions/patient) were performed for the lesions of subsegmental arteries (1155 lesions), segmental arteries (738 lesions), and lobar arteries (4 lesions) identified by CBCT or ECG-gated ADCT. Significant improvements in the symptoms, 6-min walk distance, brain natriuretic peptide level, exercise capacity, and haemodynamics were observed 3 months and 1 year after BPA. No cases of death or cardiogenic shock with a low rate of severe wire perforation (0.3%) and severe reperfusion oedema (0.3%) were observed. Conclusions: BPA guided by CBCT or ECG-gated ADCT is effective and remarkably safe in patients with CTEPH . These new advanced CT techniques may be useful in pre-BPA target lesion assessment.

Comparison of effective dose for imaging of mandible between multi-detector CT and cone-beam CT

International Nuclear Information System (INIS)

Jeong, Dae Kyo; Lee, Sang Chul; Huh, Kyung Hoe; Yi, Won Jin; Lee, Sam Sun; Choi, Soon Chul

2012-01-01

The aim of this study was to compare the effective dose for imaging of mandible between multi-detector computed tomography (MDCT) and cone-beam computed tomography (CBCT). An MDCT with low dose technique was also compared with them. Thermoluminescent dosimeter (TLD) chips were placed at 25 organ sites of an anthropomorphic phantom. The mandible of the phantom was exposed using 2 different types of MDCT units (Somatom Sensation 10 for standard-dose MDCT, Somatom Emotion 6 for low-dose MDCT) and 3 different CBCT units (AZ3000CT, Implagraphy, and Kavo 3D eXaM). The radiation absorbed dose was measured and the effective dose was calculated according to the ICRP 2007 report. The effective dose was the highest for Somatom Sensation 10 (425.84 μSv), followed by AZ3000CT (332.4 μSv), Somatom Emotion 6 (199.38 μSv), and 3D eXaM (111.6 μSv); it was the lowest for Implagraphy (83.09 μSv). The CBCT showed significant variation in dose level with different device. The effective doses of MDCTs were not significantly different from those of CBCTs for imaging of mandible. The effective dose of MDCT could be markedly decreased by using the low-dose technique.

Comparison of effective dose for imaging of mandible between multi-detector CT and cone-beam CT

Energy Technology Data Exchange (ETDEWEB)

Jeong, Dae Kyo; Lee, Sang Chul; Huh, Kyung Hoe; Yi, Won Jin; Lee, Sam Sun; Choi, Soon Chul [School of Dentistry, Seoul National University, Seoul (Korea, Republic of)

2012-06-15

The aim of this study was to compare the effective dose for imaging of mandible between multi-detector computed tomography (MDCT) and cone-beam computed tomography (CBCT). An MDCT with low dose technique was also compared with them. Thermoluminescent dosimeter (TLD) chips were placed at 25 organ sites of an anthropomorphic phantom. The mandible of the phantom was exposed using 2 different types of MDCT units (Somatom Sensation 10 for standard-dose MDCT, Somatom Emotion 6 for low-dose MDCT) and 3 different CBCT units (AZ3000CT, Implagraphy, and Kavo 3D eXaM). The radiation absorbed dose was measured and the effective dose was calculated according to the ICRP 2007 report. The effective dose was the highest for Somatom Sensation 10 (425.84 {mu}Sv), followed by AZ3000CT (332.4 {mu}Sv), Somatom Emotion 6 (199.38 {mu}Sv), and 3D eXaM (111.6 {mu}Sv); it was the lowest for Implagraphy (83.09 {mu}Sv). The CBCT showed significant variation in dose level with different device. The effective doses of MDCTs were not significantly different from those of CBCTs for imaging of mandible. The effective dose of MDCT could be markedly decreased by using the low-dose technique.

Performance Study of an aSi Flat Panel Detector for Fast Neutron Imaging of Nuclear Waste

Energy Technology Data Exchange (ETDEWEB)

Schumann, M.; Mauerhofer, E. [Institute of Energy and Climate Research - Nuclear Waste Management and Reactor Safety, Forschungszentrum Juelich GmbH, 52425 Juelich (Germany); Engels, R.; Kemmerling, G. [Central Institute for Engineering, Electronics and Analytics - Electronic Systems, Forschungszentrum Juelich GmbH, 52425 Juelich (Germany); Frank, M. [MATHCCES - Department of Mathematics, RWTH Aachen University, 52062 Aachen (Germany); Havenith, A.; Kettler, J.; Klapdor-Kleingrothaus, T. [Institute of Nuclear Engineering and Technology Transfer, RWTH Aachen University, 52062 Aachen (Germany); Schitthelm, O. [Corporate Technology, Siemens AG, 91058 Erlangen (Germany)

2015-07-01

Radioactive waste must be characterized to check its conformance for intermediate storage and final disposal according to national regulations. For the determination of radio-toxic and chemo-toxic contents of radioactive waste packages non-destructive analytical techniques are preferentially used. Fast neutron imaging is a promising technique to assay large and dense items providing, in complementarity to photon imaging, additional information on the presence of structures in radioactive waste packages. Therefore the feasibility of a compact Neutron Imaging System for Radioactive waste Analysis (NISRA) using 14 MeV neutrons is studied in a cooperation framework of Forschungszentrum Juelich GmbH, RWTH Aachen University and Siemens AG. However due to the low neutron emission of neutron generators in comparison to research reactors the challenging task resides in the development of an imaging detector with a high efficiency, a low sensitivity to gamma radiation and a resolution sufficient for the purpose. The setup is composed of a commercial D-T neutron generator (Genie16GT, Sodern) with a surrounding shielding made of polyethylene, which acts as a collimator and an amorphous silicon flat panel detector (aSi, 40 x 40 cm{sup 2}, XRD-1642, Perkin Elmer). Neutron detection is achieved using a general propose plastic scintillator (EJ-260, Eljen Technology) linked to the detector. The thermal noise of the photodiodes is reduced by employing an entrance window made of aluminium. Optimal gain and integration time for data acquisition are set by measuring the response of the detector to the radiation of a 500 MBq {sup 241}Am-source. Detector performance was studied by recording neutron radiography images of materials with various, but well known, chemical compositions, densities and dimensions (Al, C, Fe, Pb, W, concrete, polyethylene, 5 x 8 x 10 cm{sup 3}). To simulate gamma-ray emitting waste radiographs in presence of a gamma-ray sources ({sup 60}Co, {sup 137}Cs, {sup 241

CHERENCUBE: Concept definition and implementation challenges of a Cherenkov-based detector block for PET

Energy Technology Data Exchange (ETDEWEB)

Somlai-Schweiger, I., E-mail: ian.somlai@tum.de; Ziegler, S. I. [Nuklearmedizinische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, Ismaninger Strasse 22, München 81675 (Germany)

2015-04-15

8.2% (1 × 1 × 1 mm{sup 3}) to 58.6% (10 × 10 × 10 mm{sup 3}) and decreases applying a photon detection threshold of 5/10/20 photons to 6.3%/4.3%/0.7% and 49.3%/30.4%/2.8%, respectively. The detection rate in the six photodetectors is uniform due to the nearly isotropic cone emission. Most cones originated after a photoelectric effect interaction, with two dominating peaks for the kinetic energy of the electron at 422.99 and 441.47 keV. The detection distance between same-event photons defines the spatial resolution of the detector required for individual photon recognition, with 20% of the detected photons having their closest neighbor within a distance of 5% of the length of the cube. Same-event photons are detected within a time window whose width is determined by the crystal size, with values of 30 and 150 ps for a 1 × 1 × 1 mm{sup 3} and a 10 × 10 × 10 mm{sup 3} cube, respectively. The DOI reconstruction has an accuracy of approximately 23% of the length of the cube, with an average value of 2.2 mm for a 10 × 10 × 10 mm{sup 3} CHERENCUBE. Conclusions: The proposed concept requires a detector with high photodetection efficiency. The structure of the sensitive surface of the detector should be a two dimensional array of microcells, able to provide individual detection coordinates and time stamps. The microcell size determines the ability to recognize individual photons, influencing detection efficiency. The 3D DOI recognition relies on the accuracy of the time stamps and detection coordinates, without the need for a recognition of the projected patterns of photons. The refractive index of the material defines a detector intrinsic energy-based rejection of scattered PET events at the cost of reduced sensitivity.

CHERENCUBE: Concept definition and implementation challenges of a Cherenkov-based detector block for PET

International Nuclear Information System (INIS)

Somlai-Schweiger, I.; Ziegler, S. I.

2015-01-01

× 1 mm 3 ) to 58.6% (10 × 10 × 10 mm 3 ) and decreases applying a photon detection threshold of 5/10/20 photons to 6.3%/4.3%/0.7% and 49.3%/30.4%/2.8%, respectively. The detection rate in the six photodetectors is uniform due to the nearly isotropic cone emission. Most cones originated after a photoelectric effect interaction, with two dominating peaks for the kinetic energy of the electron at 422.99 and 441.47 keV. The detection distance between same-event photons defines the spatial resolution of the detector required for individual photon recognition, with 20% of the detected photons having their closest neighbor within a distance of 5% of the length of the cube. Same-event photons are detected within a time window whose width is determined by the crystal size, with values of 30 and 150 ps for a 1 × 1 × 1 mm 3 and a 10 × 10 × 10 mm 3 cube, respectively. The DOI reconstruction has an accuracy of approximately 23% of the length of the cube, with an average value of 2.2 mm for a 10 × 10 × 10 mm 3 CHERENCUBE. Conclusions: The proposed concept requires a detector with high photodetection efficiency. The structure of the sensitive surface of the detector should be a two dimensional array of microcells, able to provide individual detection coordinates and time stamps. The microcell size determines the ability to recognize individual photons, influencing detection efficiency. The 3D DOI recognition relies on the accuracy of the time stamps and detection coordinates, without the need for a recognition of the projected patterns of photons. The refractive index of the material defines a detector intrinsic energy-based rejection of scattered PET events at the cost of reduced sensitivity

X-ray detectors based on image sensors

International Nuclear Information System (INIS)

Costa, A.P.R.

1983-01-01

X-ray detectors based on image sensors are described and a comparison is made between the advantages and the disadvantages of such a kind of detectors with the position sensitive detectors. (L.C.) [pt

Indirect flat-panel detector with avalanche gain: Fundamental feasibility investigation for SHARP-AMFPI (scintillator HARP active matrix flat panel imager)

International Nuclear Information System (INIS)

Zhao Wei; Li Dan; Reznik, Alla; Lui, B.J.M.; Hunt, D.C.; Rowlands, J.A.; Ohkawa, Yuji; Tanioka, Kenkichi

2005-01-01

An indirect flat-panel imager (FPI) with avalanche gain is being investigated for low-dose x-ray imaging. It is made by optically coupling a structured x-ray scintillator CsI(Tl) to an amorphous selenium (a-Se) avalanche photoconductor called HARP (high-gain avalanche rushing photoconductor). The final electronic image is read out using an active matrix array of thin film transistors (TFT). We call the proposed detector SHARP-AMFPI (scintillator HARP active matrix flat panel imager). The advantage of the SHARP-AMFPI is its programmable gain, which can be turned on during low dose fluoroscopy to overcome electronic noise, and turned off during high dose radiography to avoid pixel saturation. The purpose of this paper is to investigate the important design considerations for SHARP-AMFPI such as avalanche gain, which depends on both the thickness d Se and the applied electric field E Se of the HARP layer. To determine the optimal design parameter and operational conditions for HARP, we measured the E Se dependence of both avalanche gain and optical quantum efficiency of an 8 μm HARP layer. The results were used in a physical model of HARP as well as a linear cascaded model of the FPI to determine the following x-ray imaging properties in both the avalanche and nonavalanche modes as a function of E Se : (1) total gain (which is the product of avalanche gain and optical quantum efficiency); (2) linearity; (3) dynamic range; (4) gain nonuniformity resulting from thickness nonuniformity; and (5) effects of direct x-ray interaction in HARP. Our results showed that a HARP layer thickness of 8 μm can provide adequate avalanche gain and sufficient dynamic range for x-ray imaging applications to permit quantum limited operation over the range of exposures needed for radiography and fluoroscopy

A rotating and warping projector/backprojector for fan-beam and cone-beam iterative algorithm

International Nuclear Information System (INIS)

Zeng, G.L.; Hsieh, Y.L.; Gullberg, G.T.

1994-01-01

A rotating-and-warping projector/backprojector is proposed for iterative algorithms used to reconstruct fan-beam and cone-beam single photon emission computed tomography (SPECT) data. The development of a new projector/backprojector for implementing attenuation, geometric point response, and scatter models is motivated by the need to reduce the computation time yet to preserve the fidelity of the corrected reconstruction. At each projection angle, the projector/backprojector first rotates the image volume so that the pixelized cube remains parallel to the detector, and then warps the image volume so that the fan-beam and cone-beam rays are converted into parallel rays. In the authors implementation, these two steps are combined so that the interpolation of voxel values are performed only once. The projection operation is achieved by a simple weighted summation, and the backprojection operation is achieved by copying weighted projection array values to the image volume. An advantage of this projector/backprojector is that the system point response function can be deconvolved via the Fast Fourier Transform using the shift-invariant property of the point response when the voxel-to-detector distance is constant. The fan-beam and cone-beam rotating-and-warping projector/backprojector is applied to SPECT data showing improved resolution

SU-E-T-757: TMRs Calculated From PDDs Versus the Direct Measurements for Small Field SRS Cones

International Nuclear Information System (INIS)

Li, H; Zhong, H; Song, K; Qin, Y; Snyder, K; Gordon, J; Chetty, I; Wen, N

2015-01-01

Purpose: To investigate the variation of TMR for SRS cones obtained by TMR scanning, calculation from PDDs, and point measurements. The obtained TMRs were also compared to the representative data from the vendor. Methods: TMRs for conical cones of 4, 5, 7.5, 10, 12.5, 15, and 17.5 mm diameter (jaws set to 5×5 cm) were obtained for 6X FFF and 10X FFF energies on a Varian Edge linac. TMR scanning was performed with a Sun Nuclear 3D scanner and Edge detector at 100 cm SDD. TMR point measurements were measured with a Wellhofer tank and Edge detector, at multiple depths from 0.5 to 20 cm and 100 cm SDD. PDDs for converting to TMR were scanned with a Wellhofer system and SFD detector. The formalism of converting PDD to TMR, given in Khan’s book (4th Edition, p.161) was applied. Sp values at dmax were obtained by measuring Scp and Sc of the cones (jaws set to 5×5 cm) using the Edge detector, and normalized to the 10×10 cm field. Results: Along the central axis beyond dmax, the RMS and maximum percent difference of TMRs obtained with different methods were as follows: (a) 1.3% (max=3.5%) for the calculated TMRs from PDDs versus direct scanning; (b) 1.2% (max=3.3%) for direct scanning versus point measurement; (c) 1.8% (max=5.1%) for the calculated versus point measurements; (d) 1.0% (max=3.6%) for direct scanning versus vendor data; (e) 1.6% (max=7.2%) for the calculated versus vendor data. Conclusion: The overall accuracy of TMRs calculated from PDDs was comparable with that of direct scanning. However, the uncertainty at depths greater than 20 cm, increased up to 5% when compared to point measurements. This issue must be considered when developing a beam model for small field SRS planning using cones

Two-sheet surface rebinning algorithm for real time cone beam tomography

Energy Technology Data Exchange (ETDEWEB)

Betcke, Marta M. [University College London (United Kingdom). Dept. of Computer Science; Lionheart, William R.B. [Manchester Univ. (United Kingdom). School of Mathematics

2011-07-01

The Rapiscan RTT80 is an example of a fast cone beam CT scanner in which the X-ray sources are fixed on a circle while the detector rows are offset axially on one side of the sources. Reconstruction for this offset truncation presents a new challenge and we propose a method using rebinning to an optimal two-sheet surface. (orig.)

Development of a large area thermal neutron detector based on a scintillator

International Nuclear Information System (INIS)

Engels, Ralf

2012-01-01

In the present work, the development and construction of a detector prototype based on wavelength shifting fiber in combination with a scintillator has been investigated and optimized. This development aims at an alternative for large area neutron detectors based on "3He detectors, which was the main construction in the past. After the study of the components and assemblies, such as: the scintillator, the wavelength-shifting-fibers and available photomultiplier tubes, the construction of the first prototype module begun. The neutron converter was selected as a "6LiF/ZnS scintillator, which produces a big light yield per absorbed neutron. The prototype itself is square and has an edge length of 30 cm in combination with two orthogonal layers of crossed wavelength-shifting-fibers. The top fiber layer, which is closer to the "6LiF/ZnS top scintillator produces the x-coordinates and the lower layer produces the y-coordinates for each event. In the prototype, MSJ-fibers from the company Kuraray were used with 1 mm diameter and spacing in the top layer of 1.5 mm and 1 mm in the lower layer. Due to the orthogonal arrangement of the wires in the two layers, one may identify where the neutron was absorbed in the scintillator and produced the light yield. In order to reduce the light loss of the absorbed photons inside the fibers, a bending radius of greater than 20 mm was used and achieved by warming up the fibers to 80 C during the bending process. The increased temperature reduces the crack formation in the fibers which increases the light loss. At this time it is expected that a photomultiplier from Hamamatsu with 256 individual pixels for readout will be used. This H9500 flat panel photomultiplier has the advantage of readout of all fibers of the prototype in one photomultiplier housing. In combination with integrated readout electronics one can minimize the homogeneity/gain differences of the photocathode pixels, the different light loss in each fiber, and the gain

Full data consistency conditions for cone-beam projections with sources on a plane

International Nuclear Information System (INIS)

Clackdoyle, Rolf; Desbat, Laurent

2013-01-01

Cone-beam consistency conditions (also known as range conditions) are mathematical relationships between different cone-beam projections, and they therefore describe the redundancy or overlap of information between projections. These redundancies have often been exploited for applications in image reconstruction. In this work we describe new consistency conditions for cone-beam projections whose source positions lie on a plane. A further restriction is that the target object must not intersect this plane. The conditions require that moments of the cone-beam projections be polynomial functions of the source positions, with some additional constraints on the coefficients of the polynomials. A precise description of the consistency conditions is that the four parameters of the cone-beam projections (two for the detector, two for the source position) can be expressed with just three variables, using a certain formulation involving homogeneous polynomials. The main contribution of this work is our demonstration that these conditions are not only necessary, but also sufficient. Thus the consistency conditions completely characterize all redundancies, so no other independent conditions are possible and in this sense the conditions are full. The idea of the proof is to use the known consistency conditions for 3D parallel projections, and to then apply a 1996 theorem of Edholm and Danielsson that links parallel to cone-beam projections. The consistency conditions are illustrated with a simulation example. (paper)

The MU-RAY project: detector technology and first data from Mt. Vesuvius

International Nuclear Information System (INIS)

Ambrosino, F; Cimmino, L; Garufi, F; Lauria, A; Masone, V; Anastasio, A; Basta, D; Energico, S; Bonechi, L; Brianzi, M; Ciaranfi, R; Bross, A; Callier, S; Taille, C de La; Caputo, A; D'Auria, L; Giudicepietro, F; Macedonio, G; Martini, M; D'Alessandro, R

2014-01-01

Muon Radiography allows to map the density of a volcanic cone. It is based on the measurement of the attenuation of the flux of muons present in the cosmic radiation on the ground. The MU-RAY project has developed an innovative detector designed for the muon radiography. The main features are the low electric power consumption, robustness and transportability, good spatial resolution and muon time of flight measurement. A 1 m 2 detector prototype has been constructed. and collected data at Mt. Vesuvius for approximately 1 month in spring 2013. A second campaign of measurement has been performed at the Puy de Dôme, France, in the last four months of 2013. In this article the principles of muon radiography, the MU-RAY detector and the first results from the collected data will be described

Evaluation of web-based instruction for anatomical interpretation in maxillofacial cone beam computed tomography

NARCIS (Netherlands)

Al-Rawi, W.T.; Jacobs, R.; Hassan, B.A.; Sanderink, G.; Scarfe, W.C.

2007-01-01

Objectives: To evaluate the effectiveness of a web-based instruction in the interpretation of anatomy in images acquired with maxillofacial cone beam CT (CBCT). Methods: An interactive web-based education course for the interpretation of craniofacial CBCT images was recently developed at our

Development of a composite large-size SiPM (assembled matrix) based modular detector cluster for MAGIC

Energy Technology Data Exchange (ETDEWEB)

Hahn, A., E-mail: ahahn@mpp.mpg.de [Max Planck Institute for Physics (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Mazin, D., E-mail: mazin@mpp.mpg.de [Max Planck Institute for Physics (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa City, Chiba 277–8582 (Japan); Bangale, P., E-mail: priya@mpp.mpg.de [Max Planck Institute for Physics (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Dettlaff, A., E-mail: todettl@mpp.mpg.de [Max Planck Institute for Physics (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Fink, D., E-mail: fink@mpp.mpg.de [Max Planck Institute for Physics (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Grundner, F., E-mail: grundner@mpp.mpg.de [Max Planck Institute for Physics (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Haberer, W., E-mail: haberer@mpp.mpg.de [Max Planck Institute for Physics (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); Maier, R., E-mail: rma@mpp.mpg.de [Max Planck Institute for Physics (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany); and others

2017-02-11

The MAGIC collaboration operates two 17 m diameter Imaging Atmospheric Cherenkov Telescopes (IACTs) on the Canary Island of La Palma. Each of the two telescopes is currently equipped with a photomultiplier tube (PMT) based imaging camera. Due to the advances in the development of Silicon Photomultipliers (SiPMs), they are becoming a widely used alternative to PMTs in many research fields including gamma-ray astronomy. Within the Otto-Hahn group at the Max Planck Institute for Physics, Munich, we are developing a SiPM based detector module for a possible upgrade of the MAGIC cameras and also for future experiments as, e.g., the Large Size Telescopes (LST) of the Cherenkov Telescope Array (CTA). Because of the small size of individual SiPM sensors (6 mm×6 mm) with respect to the 1-inch diameter PMTs currently used in MAGIC, we use a custom-made matrix of SiPMs to cover the same detection area. We developed an electronic circuit to actively sum up and amplify the SiPM signals. Existing non-imaging hexagonal light concentrators (Winston cones) used in MAGIC have been modified for the angular acceptance of the SiPMs by using C++ based ray tracing simulations. The first prototype based detector module includes seven channels and was installed into the MAGIC camera in May 2015. We present the results of the first prototype and its performance as well as the status of the project and discuss its challenges. - Highlights: • The design of the first SiPM large-size IACT pixel is described. • The simulation of the light concentrators is presented. • The temperature stability of the detector module is demonstrated. • The calibration procedure of SiPM device in the field is described.

Development of a composite large-size SiPM (assembled matrix) based modular detector cluster for MAGIC

Science.gov (United States)

Hahn, A.; Mazin, D.; Bangale, P.; Dettlaff, A.; Fink, D.; Grundner, F.; Haberer, W.; Maier, R.; Mirzoyan, R.; Podkladkin, S.; Teshima, M.; Wetteskind, H.

2017-02-01

The MAGIC collaboration operates two 17 m diameter Imaging Atmospheric Cherenkov Telescopes (IACTs) on the Canary Island of La Palma. Each of the two telescopes is currently equipped with a photomultiplier tube (PMT) based imaging camera. Due to the advances in the development of Silicon Photomultipliers (SiPMs), they are becoming a widely used alternative to PMTs in many research fields including gamma-ray astronomy. Within the Otto-Hahn group at the Max Planck Institute for Physics, Munich, we are developing a SiPM based detector module for a possible upgrade of the MAGIC cameras and also for future experiments as, e.g., the Large Size Telescopes (LST) of the Cherenkov Telescope Array (CTA). Because of the small size of individual SiPM sensors (6 mm×6 mm) with respect to the 1-inch diameter PMTs currently used in MAGIC, we use a custom-made matrix of SiPMs to cover the same detection area. We developed an electronic circuit to actively sum up and amplify the SiPM signals. Existing non-imaging hexagonal light concentrators (Winston cones) used in MAGIC have been modified for the angular acceptance of the SiPMs by using C++ based ray tracing simulations. The first prototype based detector module includes seven channels and was installed into the MAGIC camera in May 2015. We present the results of the first prototype and its performance as well as the status of the project and discuss its challenges.

Development of compact DOI-measurable PET detectors for simultaneous PET/MR Imaging

Energy Technology Data Exchange (ETDEWEB)

Shao, Yiping; Sun, Xishan [University of Texas MD Anderson Cancer Center (United States); Lou, Kai [Rice University (United States)

2015-05-18

It is critically needed yet challenging to develop compact PET detectors with high sensitivity and uniform, high imaging resolution for improving the performance of simultaneous PET/MR imaging, particularly for an integrated/inserted small-bore system. Using the latest “edge-less” SiPM arrays for DOI measurement using the design of dual-ended-scintillator readout, we developed several compact PET detectors suited for PET/MR imaging. Each detector consists of one LYSO array with each end coupled to a SiPM array. Multiple detectors can be seamlessly tiled together along all sides to form a large detector panel. Detectors with 1.5x1.5 and 2.0x2.0 mm crystals at 20 or 30 mm lengths were studied. Readout of individual SiPM or capacitor-based signal multiplexing was used to transfer 3D interaction position-coded analog signals through flexible-print-circuit cables to dedicated ASIC frontend electronics to output digital timing pulses that encode interaction information. These digital pulses can be transferred to, through standard LVDS cables, and decoded by a FPGA-based data acquisition positioned outside the MRI scanner for coincidence event selection. Initial detector performance measurement shows excellent crystal identification even with 30 mm long crystals, ~18% and 2.8 ns energy and timing resolutions, and around 2-3 mm DOI resolution. A large size detector panel can be scaled up with these modular detectors and different PET systems can be flexibly configured with the scalable readout electronics and data acquisition, providing an important design advantage for different system and application requirements. It is expected that standard shielding of detectors, electronics and signal transfer lines can be applied for simultaneous PET/MR imaging applications, with desired DOI measurement capability to enhance the PET performance and image quality.

Development of compact DOI-measurable PET detectors for simultaneous PET/MR Imaging

International Nuclear Information System (INIS)

Shao, Yiping; Sun, Xishan; Lou, Kai

2015-01-01

It is critically needed yet challenging to develop compact PET detectors with high sensitivity and uniform, high imaging resolution for improving the performance of simultaneous PET/MR imaging, particularly for an integrated/inserted small-bore system. Using the latest “edge-less” SiPM arrays for DOI measurement using the design of dual-ended-scintillator readout, we developed several compact PET detectors suited for PET/MR imaging. Each detector consists of one LYSO array with each end coupled to a SiPM array. Multiple detectors can be seamlessly tiled together along all sides to form a large detector panel. Detectors with 1.5x1.5 and 2.0x2.0 mm crystals at 20 or 30 mm lengths were studied. Readout of individual SiPM or capacitor-based signal multiplexing was used to transfer 3D interaction position-coded analog signals through flexible-print-circuit cables to dedicated ASIC frontend electronics to output digital timing pulses that encode interaction information. These digital pulses can be transferred to, through standard LVDS cables, and decoded by a FPGA-based data acquisition positioned outside the MRI scanner for coincidence event selection. Initial detector performance measurement shows excellent crystal identification even with 30 mm long crystals, ~18% and 2.8 ns energy and timing resolutions, and around 2-3 mm DOI resolution. A large size detector panel can be scaled up with these modular detectors and different PET systems can be flexibly configured with the scalable readout electronics and data acquisition, providing an important design advantage for different system and application requirements. It is expected that standard shielding of detectors, electronics and signal transfer lines can be applied for simultaneous PET/MR imaging applications, with desired DOI measurement capability to enhance the PET performance and image quality.

Variability of silver fir (Abies alba Mill. cones – variability of cone parameters

Directory of Open Access Journals (Sweden)

Aniszewska Monika

2016-09-01

Full Text Available This study aimed at determining the shape of closed silver fir cones from the Jawor Forest District (Wroclaw, based purely on measurements of their length and thickness. Using these two parameters, the most accurate estimations were achieved with a fourth-degree polynomial fitting function. We then calculated the cones’ surface area and volume in three different ways: 1 Using the fourth-degree polynomial shape estimation, 2 Introducing indicators of compliance (k1, k2, k3 to calculate the volume and then comparing it to its actual value as measured in a pitcher filled with water, 3 Comparing the surface area of the cones as calculated with the polynomial function to the value obtained from ratios of indicators of compliance (ratios k4 and k5. We found that the calculated surface area and volume were substantially higher than the corresponding measured values. Test values of cone volume and surface area as calculated by our model were 8% and 5% lower, respectively, compared to direct measurements. We also determined the fir cones apparent density to be 0.8 g·cm-3on average. The gathered data on cone surface area, volume and bulk density is a valuable tool for optimizing the thermal peeling process in mill cabinets to acquire high quality seeds.

A Micromegas-based low-background x-ray detector coupled to a slumped-glass telescope for axion research

CERN Document Server

Aznar, F; Christensen, F E; Dafni, T; Decker, T A; Ferrer-Ribas, E; Garcia, J A; Giomataris, I; Gracia, J G; Hailey, C J; Hill, R M; Iguaz, F J; Irastorza, I G; Jakobsen, A C; Luzon, G; Mirallas, H; Papaevangelou, T; Pivovaroff, M J; Ruz, J; Vafeiadis, T; Vogel, J K

2015-01-01

We report on the design, construction and operation of a low background x-ray detection line composed of a shielded Micromegas (micromesh gaseous structure) detector of the microbulk technique. The detector is made from radiopure materials and is placed at the focal point of a $\\sim$~5 cm diameter, 1.3 m focal-length, cone-approximation Wolter I x-ray telescope (XRT) comprised of thermally-formed (or "slumped") glass substrates deposited with multilayer coatings. The system has been conceived as a technological pathfinder for the future International Axion Observatory (IAXO), as it combines two of the techniques (optic and detector) proposed in the conceptual design of the project. It is innovative for two reasons: it is the first time an x-ray optic has been designed and fabricated specifically for axion research, and the first time a Micromegas detector has been operated with an x-ray optic. The line has been installed at one end of the CERN Axion Solar Telescope (CAST) magnet and is currently looking for s...

Metal artifact reduction for flat panel detector intravenous CT angiography in patients with intracranial metallic implants after endovascular and surgical treatment.

Science.gov (United States)

Pjontek, Rastislav; Önenköprülü, Belgin; Scholz, Bernhard; Kyriakou, Yiannis; Schubert, Gerrit A; Nikoubashman, Omid; Othman, Ahmed; Wiesmann, Martin; Brockmann, Marc A

2016-08-01

Flat panel detector CT angiography with intravenous contrast agent injection (IV CTA) allows high-resolution imaging of cerebrovascular structures. Artifacts caused by metallic implants like platinum coils or clips lead to degradation of image quality and are a significant problem. To evaluate the influence of a prototype metal artifact reduction (MAR) algorithm on image quality in patients with intracranial metallic implants. Flat panel detector CT after intravenous application of 80 mL contrast agent was performed with an angiography system (Artis zee; Siemens, Forchheim, Germany) using a 20 s rotation protocol (200° rotation angle, 20 s acquisition time, 496 projections). The data before and after MAR of 26 patients with a total of 34 implants (coils, clips, stents) were independently evaluated by two blinded neuroradiologists. MAR improved the assessability of the brain parenchyma and small vessels (diameter metallic implants and at a distance of 6 cm (p<0.001 each, Wilcoxon test). Furthermore, MAR significantly improved the assessability of parent vessel patency and potential aneurysm remnants (p<0.005 each, McNemar test). MAR, however, did not improve assessability of stented vessels. When an intravenous contrast protocol is used, MAR significantly ameliorates the assessability of brain parenchyma, vessels, and treated aneurysms in patients with intracranial coils or clips. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Radiation detectors based by polymer materials

International Nuclear Information System (INIS)

Cherestes, Margareta; Cherestes, Codrut; Constantinescu, Livia

2004-01-01

Scintillation counters make use of the property of certain chemical compounds to emit short light pulses after excitation produced by the passage of charged particles or photons of high energy. These flashes of light are detected by a photomultiplier tube that converts the photons into a voltage pulse. The light emitted from the detector also can be collected, focussed and dispersed by a CCD detector. The study of the evolution of the light emission and of the radiation damage under irradiation is a primary topic in the development of radiation hard polymer based scintillator. Polymer scintillator thin films are used in monitoring radiation beam intensities and simultaneous counting of different radiations. Radiation detectors have characteristics which depend on: the type of radiation, the energy of radiation, and the material of the detector. Three types of polymer thin films were studied: a polyvinyltoluene based scintillator, fluorinated polyimide and PMMA. (authors)

Performance Evaluation of Large Aperture 'Polished Panel' Optical Receivers Based on Experimental Data

Science.gov (United States)

Vilnrotter, Victor

2013-01-01

Recent interest in hybrid RF/Optical communications has led to the development and installation of a "polished-panel" optical receiver evaluation assembly on the 34-meter research antenna at Deep-Space Station 13 (DSS-13) at NASA's Goldstone Communications Complex. The test setup consists of a custom aluminum panel polished to optical smoothness, and a large-sensor CCD camera designed to image the point-spread function (PSF) generated by the polished aluminum panel. Extensive data has been obtained via realtime tracking and imaging of planets and stars at DSS-13. Both "on-source" and "off-source" data were recorded at various elevations, enabling the development of realistic simulations and analytic models to help determine the performance of future deep-space communications systems operating with on-off keying (OOK) or pulse-position-modulated (PPM) signaling formats with photon-counting detection, and compared with the ultimate quantum bound on detection performance for these modulations. Experimentally determined PSFs were scaled to provide realistic signal-distributions across a photon-counting detector array when a pulse is received, and uncoded as well as block-coded performance analyzed and evaluated for a well-known class of block codes.

Mode system effects in an online panel study : Comparing a probability-based online panel with two face-to-face reference surveys

NARCIS (Netherlands)

Struminskaya, Bella; de Leeuw, E.D.; Kaczmirek, Lars

2015-01-01

One of the methods for evaluating online panels in terms of data quality is comparing the estimates that the panels provide with benchmark sources. For probability-based online panels, high-quality surveys or government statistics can be used as references. If differences among the benchmark and the

Foveal cone spacing and cone photopigment density difference: objective measurements in the same subjects.

Science.gov (United States)

Marcos, S; Tornow, R P; Elsner, A E; Navarro, R

1997-07-01

Foveal cone spacing was measured in vivo using an objective technique: ocular speckle interferometry. Cone packing density was computed from cone spacing data. Foveal cone photopigment density difference was measured in the same subjects using retinal densitometry with a scanning laser ophthalmoscope. Both the cone packing density and cone photopigment density difference decreased sharply with increasing retinal eccentricity. From the comparison of both sets of measurements, the computed amounts of photopigment per cone increased slightly with increasing retinal eccentricity. Consistent with previous results, decreases in cone outer segment length are over-compensated by an increase in the outer segment area, at least in retinal eccentricities up to 1 deg.

Advanced radiation detector development: Advanced semiconductor detector development: Development of a oom-temperature, gamma ray detector using gallium arsenide to develop an electrode detector

International Nuclear Information System (INIS)

Knoll, G.F.

1995-11-01

The advanced detector development project at the University of Michigan has completed the first full year of its current funding. Our general goals are the development of radiation detectors and spectrometers that are capable of portable room temperature operation. Over the past 12 months, we have worked primarily in the development of semiconductor spectrometers with open-quotes single carrierclose quotes response that offer the promise of room temperature operation and good energy resolution in gamma ray spectroscopy. We have also begun a small scale effort at investigating the properties of a small non-spectroscopic detector system with directional characteristics that will allow identification of the approximate direction in which gamma rays are incident. These activities have made use of the extensive clean room facilities at the University of Michigan for semiconductor device fabrication, and also the radiation measurement capabilities provided in our laboratory in the Phoenix Building on the North Campus. In addition to our laboratory based activities, Professor Knoll has also been a participant in several Department of Energy review activities held in the Forrestal Building and at the Germantown site. The most recent of these has been service on a DOE review panel chaired by Dr. Hap Lamonds that is reviewing the detector development programs supported through the Office of Arms Control and International Security

A new configuration of the Moxon-Rae detector based on Si detector

International Nuclear Information System (INIS)

Niu, H.; Hsu, J.Y.; Liang, J.H.; Yuan, L.G.

2002-01-01

A new Moxon-Rae detector configuration based on Si semiconductor detector was proposed in this paper. Three γ-ray sources, 137 Cs, 60 Co, and 24 Na, were employed to make actual measurements using the new Moxon-Rae detector. The measured pulse height spectra and detection efficiencies were compared with the EGS4 simulated values. The results revealed that the proposed new configuration is indeed a successful method and specially a useful technique for higher energy γ-ray measurement

Digital radiography of the skeleton using a large-area detector based on amorphous silicon technology: Image quality and potential for dose reduction in comparison with screen-film radiography

International Nuclear Information System (INIS)

Volk, M.; Strotzer, M.; Holzkneckt, N.; Manke, C.; Lenhart, M.; Gmeinwieser, J.; Link, J.; Reiser, M.; Feuerback, S.

2000-01-01

AIM: The purpose of this study was to evaluate a large-area, flat-panel X-ray detector (FD), based on caesium-iodide (CsI) and amorphous silicon (a-Si) with respect to skeletal radiography. Conventional images were compared with digital radiographs using identical and reduced radiation doses. MATERIALS AND METHODS: Thirty consecutive patients were studied prospectively using conventional screen-film radiography (SFR; detector dose 2.5 μGy). Digital images were taken from the same patients with detector doses of 2.5, 1.25 and 0.625 μGy, respectively. The active-matrix detector had a panel size of 43 x 43 cm, a matrix of 3 x 3K, and a pixel size of 143 μm. All hard copies were presented in a random order to eight independent observers, who rated image quality according to subjective quality criteria. Results were assessed for significance using the Student's t -test (confidence level 95%). RESULTS: A statistically significant preference for digital over conventional images was revealed for all quality criteria, except for over-exposure (detector dose 2.5 μGy). Digital images with a 50% dose showed a small, statistically not significant, inferiority compared with SFR. The FD-technique was significantly inferior to SFR at 75% dose reduction regarding bone cortex and trabecula, contrast and overall impression. No statistically significant differences were found with regard to over- and under-exposure and soft tissue presentation. CONCLUSION: Amorphous silicon-based digital radiography yields good image quality. The potential for dose reduction depends on the clinical query. Volk, M. (2000)

Comparison of a dental cone beam CT with a multi-detector row CT on effective doses and physical image quality

International Nuclear Information System (INIS)

Yoshida, Yutaka; Tokumori, Kenji; Okamura, Kazutoshi; Yoshiura, Kazunori

2011-01-01

The purpose of this study was to compare a dental cone beam computed tomography (dental CBCT) and a multi-detector row CT (MDCT) using effective doses and physical image quality. A dental mode (D-mode) and an implant mode (I-mode) were employed for calculating effective doses. Field of view (FOV) size of the MDCT was 150 mm. Three types of images were obtained using 3 different reconstruction functions: FC1 (for abdomen images), FC30 (for internal ear and bone images) and FC81 (for high resolution images). Effective doses obtained with the D-mode and with the I-mode were about 20% and 50% of those obtained with the MDCT, respectively. Resolution properties obtained with the D-mode and I-mode were superior to that of the MDCT in a high frequency range. Noise properties of the D-mode and the I-mode were better than those with FC81. It was found that the dental CBCT has better potential as compared with MDCT in both dental and implant modes. (author)

Evaluation of imaging reformation with cone beam computed tomography for the assessment of bone density and shape in mandible

International Nuclear Information System (INIS)

Hong, Sang Woo; Kim, Gyu Tae; Choi, Yong Suk; Hwan, Eui Hwan

2008-01-01

Diagnostic estimation of destruction and formation of bone has the typical limit according to capacity of x-ray generator and image detector. So the aim of this study was to find out how much it can reproduce the shape and the density of bone in the case of using recently developed dental type of cone beam computed tomography, and which image is applied by new detector and mathematic calculation. Cone beam computed tomography (PSR 9000N, Asahi Roentgen Ind. Co., Ltd., Japan) and soft x-ray radiography were executed on dry mandible that was already decalcified during 5 hours, 10 hours, 15 hours, 20 hours, and 25 hours. Estimating and comparing of those came to the following results. The change of inferior border of mandible and anterior border of ramous in the region of cortical bone was observed between first 5 and 10 hours of decalcification. The reproduction of shape and density in the region of cortical bone and cancellous bone can be hardly observed at cone beam computed tomography compared with soft x-ray radiography. The difference of decrease of bone density according to hours of decalcification increase was not reproduced at cone beam computed tomography compared with soft x-ray radiography. CBCT images revealed higher spatial resolution. However, contrast resolution in region of low contrast sensitivity is the inferiority of images' property.

Finite Element Analysis of the SciFi-Nomex-Sandwich Panels

CERN Document Server

Schultz von Dratzig, Arndt

2015-01-01

A finite element analysis of the SciFi-Nomex-sandwich panels has been carried out in order to investigate their thermo-mechanical properties. This does not include the cooling of the silicon photomultipliers but is restricted to the panels themselves. Two kinds of panels have been considered: panels with 40 mm thickness and panels with 50 mm thickness. Both versions are equipped with mats of six layers of scintillating fibers. The analyses were carried out for a series of mechanical and thermal loads which might occur during the production or installation of the detector. For both versions the stiffnesses prove to be sufficient and no critical stresses or strains are found.

Quotient normed cones

Indian Academy of Sciences (India)

general setting of the space CL(X, Y ) of all continuous linear mappings from a normed cone (X, p) to a normed cone (Y, q), extending several well-known results related to open continuous linear mappings between normed linear spaces. Keywords. Normed cone; extended quasi-metric; continuous linear mapping; bicom-.

Active sound transmission control of an experimental double-panel partition using decoupled, dual-channel, analog feedback control

OpenAIRE

Sagers, Jason; Blotter, Jonathan

2008-01-01

This paper addresses the construction, measurement, and analysis of a double panel active partition (DPAP) and its accompanying analog feedback controllers. The DPAP was constructed by attaching an aluminum cone loudspeaker at each end of a short segment of a circular duct. Two analog feedback controllers were designed and built using the measured frequency response function of each panel. Two independent (decoupled) feedback controllers were then used to minimize the vibration amplitude of e...

Prototype heel effect compensation filter for cone-beam CT

International Nuclear Information System (INIS)

Mori, Shinichiro; Endo, Masahiro; Nishizawa, Kanae; Ohno, Mari; Miyazaki, Hiroaki; Tsujita, Kazuhiko; Saito, Yasuo

2005-01-01

The prototype cone-beam CT (CBCT) has a larger beam width than the conventional multi-detector row CT (MDCT). This causes a non-uniform angular distribution of the x-ray beam intensity known as the heel effect. Scan conditions for CBCT tube current are adjusted on the anode side to obtain an acceptable clinical image quality. However, as the dose is greater on the cathode side than on the anode side, the signal-to-noise ratio on the cathode side is excessively high, resulting in an unnecessary dose amount. To compensate for the heel effect, we developed a heel effect compensation (HEC) filter. The HEC filter rendered the dose distribution uniform and reduced the dose by an average of 25% for free air and by 20% for CTDI phantoms compared to doses with the conventional filter. In addition, its effect in rendering the effective energy uniform resulted in an improvement in image quality. This new HEC filter may be useful in cone-beam CT studies. (note)

Non-destructive characterisation of polymers and Al-alloys by polychromatic cone-beam phase contrast tomography

International Nuclear Information System (INIS)

Kastner, Johann; Plank, Bernhard; Requena, Guillermo

2012-01-01

X-ray computed tomography (XCT) has become a very important tool for the non-destructive characterisation of materials. Continuous improvements in the quality and performance of X-ray tubes and detectors have led to cone-beam XCT systems that can now achieve spatial resolutions down to 1 μm and even below. Since not only the amplitude but also the phase of an X-ray beam is altered while passing through an object, phase contrast effects can occur even for polychromatic sources when the spatial coherence due to a small focal spot size is high enough. This can lead to significant improvements over conventional attenuation-based X-ray computed tomography. Phase contrast can increase by edge enhancement the visibility of small structures and of features which are only slightly different in attenuation. We report on the possibilities of polychromatic cone-beam phase contrast tomography for non-destructive characterisation of materials. A carbon fibre-reinforced polymer and the Al-alloys AlMg5Si7 and AlSi18 were investigated with high resolution cone-beam X-ray computed tomography with a polychromatic tube source. Under certain conditions strong phase contrast resulting in an upward and downward overshooting of the grey values across edges was observed. The phase effects are much stronger for the polymer than for the Al-alloys. The influence on the phase contrast of the parameters, including source-detector distance, focal spot size and tube acceleration voltage is presented. Maximum phase contrast was observed for a maximum distance between the source and the detector, for a low voltage and a minimum focal spot size at the X-ray source. The detectability of the different phases is improved by the edge enhancement and the resulting improvement of sharpness. Thus, a better segmentation of the carbon fibres in the fibre-reinforced polymer and of the Mg 2 Si-phase in the AlMg5Si7-alloy is achieved. Primary and eutectic Si cannot be detected by attenuation-based X

A novel method for contrast-to-noise ratio (CNR) evaluation of digital mammography detectors

International Nuclear Information System (INIS)

Baldelli, P.; Phelan, N.; Egan, G.

2009-01-01

The purpose of this study was to test a new, simple method of evaluating the contrast-to-noise ratio (CNR) over the entire image field of a digital detector and to compare different mammography systems. Images were taken under clinical exposure conditions for a range of simulated breast thicknesses using poly(methyl methacrylate) (PMMA). At each PMMA thickness, a second image which included an additional 0.2-mm Al sheet was also acquired. Image processing software was used to calculate the CNR in multiple regions of interest (ROI) covering the entire area of the detector in order to obtain a 'CNR image'. Five detector types were evaluated, two CsI-αSi (GE Healthcare) flat panel systems, one αSe (Hologic) flat panel system and a two generations of scanning photon counting digital detectors (Sectra). Flat panel detectors exhibit better CNR uniformity compared with the first-generation scanning photon counting detector in terms of mean pixel value variation. However, significant improvement in CNR uniformity was observed for the next-generation scanning detector. The method proposed produces a map of the CNR and a measurement of uniformity throughout the entire image field of the detector. The application of this method enables quality control measurement of individual detectors and a comparison of detectors using different technologies. (orig.)

ECFA Detector R&D Panel, Review Report

CERN Document Server

Abramowicz, H.; Afanaciev, K.; Aguilar, J.; Alvarez, E.; Bambade, P.; Bortko, L.; Bozovic-Jelisavcic, I.; Castro, E.; Chelkov, G.; Coca, C.; Daniluk, W.; Dragone, A.; Dumitru, L.; Elsener, K.; Emeliantchik, I.; Firu, E.; Fischer, J.; Fiutowski, T.; Ghenescu, V.; Gostkin, M.; Grzelak, G.; Haller, G.; Henschel, H.; Ignatenko, A.; Idzik, M.; Ito, K.; Kananov, S.; Kielar, E.; Kollowa, S.; Kotula, J.; Krumstein, Z.; Krupa, B.; Kulis, S.; Lange, W.; Levy, A.; Levy, I.; Linssen, L.; Lohmann, W.; Lukic, S.; Moron, J.; Moszczynski, A.; Nauenberg, U.; Neagu, A.; Novgorodova, O.; Nuiry, F.X.; Ohlerich, M.; Orlandea, M.; Oleinik, G.; Oliwa, K.; Olshevski, A.; Pandurovic, M.; Pawlik, B.; Preda, T.; Przyborowski, D.; Sato, Y.; Sadeh, I.; Sailer, A.; Schumm, B.; Schuwalow, S.; Schwartz, R.; Smiljanic, I.; Swientek, K.; Takubo, Y.; Teodorescu, E.; Wierba, W.; Yamamoto, H.; Zawiejski, L.; Zgura, T.S.; Zhang, J.

2014-01-01

Two special calorimeters are foreseen for the instrumentation of the very forward region of an ILC or CLIC detector; a luminometer (LumiCal) designed to measure the rate of low angle Bhabha scattering events with a precision better than 10−3 at the ILC and 10−2 at CLIC, and a low polar-angle calorimeter (BeamCal). The latter will be hit by a large amount of beamstrahlung remnants. The intensity and the spatial shape of these depositions will provide a fast luminosity estimate, as well as determination of beam parameters. The sensors of this calorimeter must be radiation-hard. Both devices will improve the e.m. hermeticity of the detector in the search for new particles. Finely segmented and very compact electromagnetic calorimeters will match these requirements. Due to the high occupancy, fast front-end electronics will be needed. Monte Carlo studies were performed to investigate the impact of beam-beam interactions and physics background processes on the luminosity measurement, and of beamstrahlung on th...

Adaptive radiotherapy based on contrast enhanced cone beam CT imaging

International Nuclear Information System (INIS)

Soevik, Aaste; Skogmo, Hege K.; Roedal, Jan; Lervaag, Christoffer; Eilertsen, Karsten; Malinen, Eirik

2010-01-01

Cone beam CT (CBCT) imaging has become an integral part of radiation therapy, with images typically used for offline or online patient setup corrections based on bony anatomy co-registration. Ideally, the co-registration should be based on tumor localization. However, soft tissue contrast in CBCT images may be limited. In the present work, contrast enhanced CBCT (CECBCT) images were used for tumor visualization and treatment adaptation. Material and methods. A spontaneous canine maxillary tumor was subjected to repeated cone beam CT imaging during fractionated radiotherapy (10 fractions in total). At five of the treatment fractions, CECBCT images, employing an iodinated contrast agent, were acquired, as well as pre-contrast CBCT images. The tumor was clearly visible in post-contrast minus pre-contrast subtraction images, and these contrast images were used to delineate gross tumor volumes. IMRT dose plans were subsequently generated. Four different strategies were explored: 1) fully adapted planning based on each CECBCT image series, 2) planning based on images acquired at the first treatment fraction and patient repositioning following bony anatomy co-registration, 3) as for 2), but with patient repositioning based on co-registering contrast images, and 4) a strategy with no patient repositioning or treatment adaptation. The equivalent uniform dose (EUD) and tumor control probability (TCP) calculations to estimate treatment outcome for each strategy. Results. Similar translation vectors were found when bony anatomy and contrast enhancement co-registration were compared. Strategy 1 gave EUDs closest to the prescription dose and the highest TCP. Strategies 2 and 3 gave EUDs and TCPs close to that of strategy 1, with strategy 3 being slightly better than strategy 2. Even greater benefits from strategies 1 and 3 are expected with increasing tumor movement or deformation during treatment. The non-adaptive strategy 4 was clearly inferior to all three adaptive strategies

Noise variance analysis using a flat panel x-ray detector: A method for additive noise assessment with application to breast CT applications

Energy Technology Data Exchange (ETDEWEB)

Yang Kai; Huang, Shih-Ying; Packard, Nathan J.; Boone, John M. [Department of Radiology, University of California, Davis Medical Center, 4860 Y Street, Suite 3100 Ellison Building, Sacramento, California 95817 (United States); Department of Radiology, University of California, Davis Medical Center, 4860 Y Street, Suite 3100 Ellison Building, Sacramento, California 95817 (United States) and Department of Biomedical Engineering, University of California, Davis, Davis, California, 95616 (United States)

2010-07-15

Purpose: A simplified linear model approach was proposed to accurately model the response of a flat panel detector used for breast CT (bCT). Methods: Individual detector pixel mean and variance were measured from bCT projection images acquired both in air and with a polyethylene cylinder, with the detector operating in both fixed low gain and dynamic gain mode. Once the coefficients of the linear model are determined, the fractional additive noise can be used as a quantitative metric to evaluate the system's efficiency in utilizing x-ray photons, including the performance of different gain modes of the detector. Results: Fractional additive noise increases as the object thickness increases or as the radiation dose to the detector decreases. For bCT scan techniques on the UC Davis prototype scanner (80 kVp, 500 views total, 30 frames/s), in the low gain mode, additive noise contributes 21% of the total pixel noise variance for a 10 cm object and 44% for a 17 cm object. With the dynamic gain mode, additive noise only represents approximately 2.6% of the total pixel noise variance for a 10 cm object and 7.3% for a 17 cm object. Conclusions: The existence of the signal-independent additive noise is the primary cause for a quadratic relationship between bCT noise variance and the inverse of radiation dose at the detector. With the knowledge of the additive noise contribution to experimentally acquired images, system modifications can be made to reduce the impact of additive noise and improve the quantum noise efficiency of the bCT system.

A new system for fully automatic inspection of digital flat-panel detector radiographs of aluminium castings

International Nuclear Information System (INIS)

Fuchs, T.; Hassler, U.; Huetten, U.; Wenzel, T.

2006-01-01

The aim of our work was the integration of various newly-developed methods into a system for fully automatic radioscopic inspection of arbitrary casting parts. Using a 16-bit flat-panel detector, projections in arbitrary directions through the part are acquired and analysed. The software tool for inspection can be separated into five stages: registration, calibration, image processing, fault segmentation, and quality assessment. Thereby, each step is realized with full 16-bit data processing. Within the first processing stage, information about the physical length and density of the aluminium structures is extracted from the primary projections. Next, the primary image is registered with a reference image, which was acquired previously. Afterwards, the third stage combines both reference image-based and reference-less testing. A filter is applied, which adapts automatically to the local object structure by referring to the properties of the reference. Thereby, the self-adapting filter selects its size, direction and filter method optimally according to the local situation. Similar to the reference-less procedure, a subtraction is followed by a threshold operation, resulting in a map of regions that are suspected to be faulty. The fourth step aims at an elimination of false-positive detections. Again, two methods are applied successively: evaluation of local image features at suspicious positions and a classification based on teachings independent of position and orientation of the faults. Within the last step the quality criteria are applied. These criteria may concern fault size and depth, the density of faults in critical regions and a minimum distance between two or more faults. (orig.)

Flat-screen detector systems in skeletal radiology

International Nuclear Information System (INIS)

Grampp, S.; Czerny, C.; Krestan, C.; Henk, C.; Heiner, L.; Imhof, H.

2003-01-01

Implementation of flat-panel detectors and digital integration of the technique instead of the use of conventional radiographs leads to a shortening of the work process. With flat-panel technology the image production process is shortened by more than 30%. Major advantages in the implementation of integrated RIS, PACS and flat-panel detector system are increases in quality because most mistakes in picture labeling can be avoided, easier handling without the need for cassettes, and the possibility of image post-processing. The diagnostic quality of the images in the field of musculoskeletal radiology is, in comparison to conventional radiographs, at least adequate and in most cases markedly improved with a marked reduction in radiation exposure of around 30-50%. With respect to the numerous advantages of the digital techniques and especially flat-panel technology there is a very high likelihood that conventional radiographs will be substituted in the coming years, even though the cost of the new technology is currently significantly higher compared to conventional systems. (orig.) [de

3D dictionary learning based iterative cone beam CT reconstruction

Directory of Open Access Journals (Sweden)

Ti Bai

2014-03-01

Full Text Available Purpose: This work is to develop a 3D dictionary learning based cone beam CT (CBCT reconstruction algorithm on graphic processing units (GPU to improve the quality of sparse-view CBCT reconstruction with high efficiency. Methods: A 3D dictionary containing 256 small volumes (atoms of 3 × 3 × 3 was trained from a large number of blocks extracted from a high quality volume image. On the basis, we utilized cholesky decomposition based orthogonal matching pursuit algorithm to find the sparse representation of each block. To accelerate the time-consuming sparse coding in the 3D case, we implemented the sparse coding in a parallel fashion by taking advantage of the tremendous computational power of GPU. Conjugate gradient least square algorithm was adopted to minimize the data fidelity term. Evaluations are performed based on a head-neck patient case. FDK reconstruction with full dataset of 364 projections is used as the reference. We compared the proposed 3D dictionary learning based method with tight frame (TF by performing reconstructions on a subset data of 121 projections. Results: Compared to TF based CBCT reconstruction that shows good overall performance, our experiments indicated that 3D dictionary learning based CBCT reconstruction is able to recover finer structures, remove more streaking artifacts and also induce less blocky artifacts. Conclusion: 3D dictionary learning based CBCT reconstruction algorithm is able to sense the structural information while suppress the noise, and hence to achieve high quality reconstruction under the case of sparse view. The GPU realization of the whole algorithm offers a significant efficiency enhancement, making this algorithm more feasible for potential clinical application.-------------------------------Cite this article as: Bai T, Yan H, Shi F, Jia X, Lou Y, Xu Q, Jiang S, Mou X. 3D dictionary learning based iterative cone beam CT reconstruction. Int J Cancer Ther Oncol 2014; 2(2:020240. DOI: 10

Jet energy resolution of the SDC detector

International Nuclear Information System (INIS)

Para, A.; Beretvas, A.; Denisenko, K.; Denisenko, N.; Green, D.; Yeh, G.P.; Wu, W.; Iso, H.

1990-01-01

We have answered the PAC question (''Demonstrate the jet energy resolution of your proposed detector by studying decays Z → jet + jet and Z' → jet + jet, M Z' = 1 TeV.'') using a general program called SSCSIM. This program is a tool for investigating simple questions involving the relations between detector parameters and physics capabilities of a detector. A different package called ANLSIM developed by our colleagues at Argonne has also been used to answer this question. The results as expected are very similar. In this note we will try to document our procedures. Our tentative conclusion from this study is that physics induced effects, out-of-cone fluctuations and underlying event fluctuations, dominate the resolution. Pushing the detector performance to the limits of technology improves the effective resolution by at most 20%. 20 refs., 6 figs., 5 tabs

A DBN based anomaly targets detector for HSI

Science.gov (United States)

Ma, Ning; Wang, Shaojun; Yu, Jinxiang; Peng, Yu

2017-10-01

Due to the assumption that Hyperspectral image (HSI) should conform to Gaussian distribution, traditional Mahalanobis distance-based anomaly targets detectors perform poor because the assumption may not always hold. In order to solve those problems, a deep learning based detector, Deep Belief Network(DBN) anomaly detector(DBN-AD), was proposed to fit the unknown distribution of HSI by energy modeling, the reconstruction errors of this encode-decode processing are used for discriminating the anomaly targets. Experiments are implemented on real and synthesized HSI dataset which collection by Airborne Visible Infra-Red Imaging Spectrometer (AVIRIS). Comparing to classic anomaly detector, the proposed method shows better performance, it performs about 0.17 higher in Area Under ROC Curve (AUC) than that of Reed-Xiaoli detector(RXD) and Kernel-RXD (K-RXD).

Experiences with radiation portal detectors for international rail transport

International Nuclear Information System (INIS)

Stromswold, David C.; McCormick, Kathleen R.; Todd, Lindsay C.; Ashbaker, Eric D.; Evans, J.C.

2006-01-01

Radiation detectors monitored trains at two international borders to evaluate the performance of NaI(Tl) and plastic (polyvinyltoluene: PVT) gamma-ray detectors to characterize rail cargo. The detectors included a prototype NaI(Tl) radiation-portal-monitor panel having four large detectors (10-cm x 10-cm x 41-cm) and a PVT panel with a 41 cm x 173 cm x 3.8-cm detector. Spectral data from the NaI(Tl) and PVT detectors were recorded. Of particular emphasis was the identification of naturally occurring radioactive material (NORM) and the resultant frequency of nuisance alarms. For rail monitoring, the difficulty in stopping trains to perform secondary inspection on alarming cars creates a need for reliable identification of NORM during initial screening. Approximately 30 trains were monitored, and the commodities in individual railcars were ascertained from manifest information. At one test site the trains carried inter-modal containers that had been unloaded from ships, and at the other site the trains contained bulk cargo or individual items in boxcars or flatbeds. NORM encountered included potash, liquefied petroleum gas, fireworks, televisions, and clay-based products (e.g., pottery). Analysis of the spectral data included the use of the template-fitting program GADRAS/FitToDB from Sandia National Laboratories. For much of the NORM the NaI(Tl) data produced a correct identification of the radionuclides present in the railcars. The same analysis was also used for PVT data in which the spectral information (no peaks but only gradual spectral changes including Compton edges) was limited. However, the PVT analysis provided correct identification of 40K and 226Ra in many cases

Workshop on detectors for third-generation synchrotron sources: Proceedings

International Nuclear Information System (INIS)

1994-12-01

The aims of the workshop were (1) to acquaint APS users with current R and D being carried out on detectors, (2) to identify new detector systems possible during the next five years, (3) to identify new detectors theoretically possible in the future, (4) to stimulate interactions between user groups and detector developers, and (5) to obtain recommendations from expert panels on technical issues needing resolution. Development of detectors at ESRF, Spring-8, BNL, CERN and LBL are included

Workshop on detectors for third-generation synchrotron sources: Proceedings

Energy Technology Data Exchange (ETDEWEB)

NONE

1994-12-01

The aims of the workshop were (1) to acquaint APS users with current R and D being carried out on detectors, (2) to identify new detector systems possible during the next five years, (3) to identify new detectors theoretically possible in the future, (4) to stimulate interactions between user groups and detector developers, and (5) to obtain recommendations from expert panels on technical issues needing resolution. Development of detectors at ESRF, Spring-8, BNL, CERN and LBL are included.

Regularization design for high-quality cone-beam CT of intracranial hemorrhage using statistical reconstruction

Science.gov (United States)

Dang, H.; Stayman, J. W.; Xu, J.; Sisniega, A.; Zbijewski, W.; Wang, X.; Foos, D. H.; Aygun, N.; Koliatsos, V. E.; Siewerdsen, J. H.

2016-03-01

Intracranial hemorrhage (ICH) is associated with pathologies such as hemorrhagic stroke and traumatic brain injury. Multi-detector CT is the current front-line imaging modality for detecting ICH (fresh blood contrast 40-80 HU, down to 1 mm). Flat-panel detector (FPD) cone-beam CT (CBCT) offers a potential alternative with a smaller scanner footprint, greater portability, and lower cost potentially well suited to deployment at the point of care outside standard diagnostic radiology and emergency room settings. Previous studies have suggested reliable detection of ICH down to 3 mm in CBCT using high-fidelity artifact correction and penalized weighted least-squared (PWLS) image reconstruction with a post-artifact-correction noise model. However, ICH reconstructed by traditional image regularization exhibits nonuniform spatial resolution and noise due to interaction between the statistical weights and regularization, which potentially degrades the detectability of ICH. In this work, we propose three regularization methods designed to overcome these challenges. The first two compute spatially varying certainty for uniform spatial resolution and noise, respectively. The third computes spatially varying regularization strength to achieve uniform "detectability," combining both spatial resolution and noise in a manner analogous to a delta-function detection task. Experiments were conducted on a CBCT test-bench, and image quality was evaluated for simulated ICH in different regions of an anthropomorphic head. The first two methods improved the uniformity in spatial resolution and noise compared to traditional regularization. The third exhibited the highest uniformity in detectability among all methods and best overall image quality. The proposed regularization provides a valuable means to achieve uniform image quality in CBCT of ICH and is being incorporated in a CBCT prototype for ICH imaging.

Edge-Spread Functions Expected for Several Changes in a Commercial Flat-Panel System

International Nuclear Information System (INIS)

Schach von Wittenau, A E

2002-01-01

The Bldg. 239 radiography facility uses a 9 MeV bremsstrahlung linac and a commercially available fiat-panel detector system. Ref. [1] discusses the facility in detail. Ref. [1] furthermore discusses the imaging quality of the fiat-panel system, and identifies several sources of image blur for the system in question. The maim'' contributors to the imaging blur are radiation scattered from the front cover of the detector housing, radiation scattered from the back cover of the detector housing, and radiation scattered from the aluminum plate that supports the amorphous-Si detector within the detector housing. The manufacturer of one such fiat-panel system seems willing to modify one of their products as requested, if such modifications may be made easily. Easy modifications would include making the detector housing thinner, decreasing the sizes of air gaps inside tile detector system, etc. Removing the aluminum support plate is considered to be a difficult modification. This memo reports the results of a set of Monte Carlo simulations that were performed to predict the changes in imaging quality, compared to that of the current system, if the detector is modified as suggested above. In particular, the edge-spread function (ESF) was calculated for each modification. ESFs were calculated for three photon energies: 100 keV, 450 keV, and 3 MeV. The results suggest that thinning and moving tile front and back covers of the detector housing should result in improved image quality for all of the photon energies considered. Interestingly, the results also suggest that removing the aluminum support plate would improve tim imaging performance at 100 keV and 450 keV, but that removing the plate has no additional benefit for imaging with 3 MeV photons

SU-F-T-555: Accurate Stereotactic Cone TMRs Converted from PDDs Scanned with Ray Trace

International Nuclear Information System (INIS)

Li, H; Zhong, H; Qin, Y; Snyder, K; Chetty, I; Wen, N

2016-01-01

Purpose: To investigate whether the accuracy of TMRs for stereotactic cones converted from PDDs scanned with Ray Trace can be improved, when compared against the TMRs converted from the traditional PDDs. Methods: Ray Trace measurement in Sun Nuclear 3D Scanner is for accurate scan of small field PDDs. The system detects the center of field at two depths, for example, at 3 and 20 cm in our study, and then performs scan along the line passing the two centers. With both Ray Trace and the traditional method, PDDs for conical cones of 4, 5, 7.5, 10, 12.5, 15, and 17.5 mm diameter (jaws set to 5×5 cm) were obtained for 6X FFF and 10X FFF energies on a Varian Edge linac, using Edge detectors. The formalism of converting PDD to TMR given in Khan’s book (4th Edition, p.161) was applied. Sp values at dmax were obtained by measuring cone Scp and Sc. Continuous direct measurement of TMR by filling/draining water to/from the tank and spot measurement by moving the tank and detector were also performed with the same equipment, using 100 cm SDD. Results: For 6XFFF energy and all the cones, TMRs converted from Ray Trace were very close to the continuous and spot measurement, while TMRs converted from traditional PDDs had larger deviation. Along the central axis beyond dmax, 1.7% of TMR data points calculated from Ray Trace had more 3% deviation from measurement, with maximal deviation of 5.2%. Whereas, 34% of TMR points calculated from traditional PDDs had more than 3% deviation, with maximum of 5.7%. In this initial study, Ray Trace scans for 10XFFF beam were noisy, further measurement is warranted. Conclusion: The Ray Trace could improve the accuracy of PDDs measurement and the calculated TMRs for stereotactic cones, which was within 3% of the measured TMRs.

SU-F-T-555: Accurate Stereotactic Cone TMRs Converted from PDDs Scanned with Ray Trace

Energy Technology Data Exchange (ETDEWEB)

Li, H; Zhong, H; Qin, Y; Snyder, K; Chetty, I; Wen, N [Henry Ford Health System, Detroit, MI (United States)

2016-06-15

Purpose: To investigate whether the accuracy of TMRs for stereotactic cones converted from PDDs scanned with Ray Trace can be improved, when compared against the TMRs converted from the traditional PDDs. Methods: Ray Trace measurement in Sun Nuclear 3D Scanner is for accurate scan of small field PDDs. The system detects the center of field at two depths, for example, at 3 and 20 cm in our study, and then performs scan along the line passing the two centers. With both Ray Trace and the traditional method, PDDs for conical cones of 4, 5, 7.5, 10, 12.5, 15, and 17.5 mm diameter (jaws set to 5×5 cm) were obtained for 6X FFF and 10X FFF energies on a Varian Edge linac, using Edge detectors. The formalism of converting PDD to TMR given in Khan’s book (4th Edition, p.161) was applied. Sp values at dmax were obtained by measuring cone Scp and Sc. Continuous direct measurement of TMR by filling/draining water to/from the tank and spot measurement by moving the tank and detector were also performed with the same equipment, using 100 cm SDD. Results: For 6XFFF energy and all the cones, TMRs converted from Ray Trace were very close to the continuous and spot measurement, while TMRs converted from traditional PDDs had larger deviation. Along the central axis beyond dmax, 1.7% of TMR data points calculated from Ray Trace had more 3% deviation from measurement, with maximal deviation of 5.2%. Whereas, 34% of TMR points calculated from traditional PDDs had more than 3% deviation, with maximum of 5.7%. In this initial study, Ray Trace scans for 10XFFF beam were noisy, further measurement is warranted. Conclusion: The Ray Trace could improve the accuracy of PDDs measurement and the calculated TMRs for stereotactic cones, which was within 3% of the measured TMRs.

A LabVIEWTM-based detector testing system

International Nuclear Information System (INIS)

Yang Haori; Li Yuanjing; Wang Yi; Li Yulan; Li Jin

2003-01-01

The construction of a LabVIEW-based detector testing system is described in this paper. In this system, the signal of detector is magnified and digitized, so amplitude or time spectrum can be obtained. The Analog-to-Digital Converter is a peak-sensitive ADC based on VME bus. The virtual instrument constructed by LabVIEW can be used to acquire data, draw spectrum and save testing results

Berkeley Lighting Cone

Energy Technology Data Exchange (ETDEWEB)

Lask, Kathleen [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Gadgil, Ashok [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2016-10-24

A lighting cone is a simple metal cone placed on the fuel bed of a stove during ignition to act as a chimney, increasing the draft through the fuel bed. Many stoves tend to be difficult to light due to poor draft through the fuel bed, so lighting cones are used in various parts of the world as an inexpensive accessory to help with ignition.

Hemichannel-mediated and pH-based feedback from horizontal cells to cones in the vertebrate retina.

Directory of Open Access Journals (Sweden)

Iris Fahrenfort

2009-06-01

Full Text Available Recent studies designed to identify the mechanism by which retinal horizontal cells communicate with cones have implicated two processes. According to one account, horizontal cell hyperpolarization induces an increase in pH within the synaptic cleft that activates the calcium current (Ca(2+-current in cones, enhancing transmitter release. An alternative account suggests that horizontal cell hyperpolarization increases the Ca(2+-current to promote transmitter release through a hemichannel-mediated ephaptic mechanism.To distinguish between these mechanisms, we interfered with the pH regulating systems in the retina and studied the effects on the feedback responses of cones and horizontal cells. We found that the pH buffers HEPES and Tris partially inhibit feedback responses in cones and horizontal cells and lead to intracellular acidification of neurons. Application of 25 mM acetate, which does not change the extracellular pH buffer capacity, does lead to both intracellular acidification and inhibition of feedback. Because intracellular acidification is known to inhibit hemichannels, the key experiment used to test the pH hypothesis, i.e. increasing the extracellular pH buffer capacity, does not discriminate between a pH-based feedback system and a hemichannel-mediated feedback system. To test the pH hypothesis in a manner independent of artificial pH-buffer systems, we studied the effect of interfering with the endogenous pH buffer, the bicarbonate/carbonic anhydrase system. Inhibition of carbonic anhydrase allowed for large changes in pH in the synaptic cleft of bipolar cell terminals and cone terminals, but the predicted enhancement of the cone feedback responses, according to the pH-hypothesis, was not observed. These experiments thus failed to support a proton mediated feedback mechanism. The alternative hypothesis, the hemichannel-mediated ephaptic feedback mechanism, was therefore studied experimentally, and its feasibility was buttressed

Consistency questions in the light cone gauge based on equal time commutation rules

International Nuclear Information System (INIS)

Haller, K.

1989-01-01

We investigate whether time displacement invariant propagators are compatible canonical formulations in the light cone gauge based on equal time commutation rules. We conclude that, in the light cone gauge, time displacement invariant propagators are not consistent with the requirement that, in canonical formulations of gauge theories, only transversely polarized, massless gauge field excitations (photons, or gluons in perturbative QCD), can contribute to the transverse part of a time displacement invariant propagator. When the time displacement invariant light cone gauge propagator is represented as a four-dimensional momentum space Fourier integral the following is observed: Transverse parts of the propagator obtain time displacement invariant contributions from the (k 3 -k 0 ) pole, as well as from the (vertical strokekvertical stroke 2 -k 0 2 ) pole. But since, in the Schroedinger picture (i.e. at t=0), the divergence-free part of the gauge field consists of transversely polarized gauge field excitations only, the transverse part of the propagator either can have time displacement invariant time dependence determined by the (vertical strokekvertical stroke 2 -k 0 2 ) pole; or, if any part of the transverse propagator has time dependence determined by the (k 3 -k 0 ) pole, it cannot be time displacement invariant. (orig.)

Method of plastic track detector electrochemical etching

International Nuclear Information System (INIS)

D'yakov, A.A.

1984-01-01

The review of studies dealing with the development of the method for the electro-chemical etching (ECE) of the plastic track detectors on the base of polyethy-leneterephthalate (PET) and polycarbonate (PC) is given. Physical essence of the method, basic parameters of the processes, applied equipment and methods of measurement automation are considered. The advantages of the method over the traditional chemical etching are pointed out. Recommendations on the detector operation modes when detecting fission fragments, α-particles and fast neutrons are given. The ECE method is based on the condition that during chemical etching the high-voltage sound frequency alternating electric field is applied to the detector. In this case the detector serves as an isolating layer betWeen two vessels with etching solution in which high-voltage electrode are submerged. At a fixed electric field potential higher (over than the threshold value) at the end of the etching track cone atree-like discharge spot arises. It is shown that when PET is used for fast neutron detection it is advisable to apply for ECE the PEW solution (15g KOH+40 g C 2 H 2 OH + 45g H 2 O) the field potential should constitute 30 kVxcm -1 at the freqUency of 9 kHz. In the case of fission fragment detection Using ECE and PC the following ECE conditions are recommended: 30% KOH etcher, field potential of 10 kVxcm -1 , 2-4 kHz frequency. It is concluded that the ECE method permits considerably eXtend the sphere of plastic track detector application for detecting ionizing particles,

Correlation analysis of heat flux and fire behaviour and hazards of polycrystalline silicon photovoltaic panels

Science.gov (United States)

Ju, Xiaoyu; Zhou, Xiaodong; Peng, Fei; Wu, Zhibo; Lai, Dimeng; Hu, Yue; Yang, Lizhong

2017-05-01

This work aims to gain a better understanding of fire behaviour and hazards of PV panels under different radiation heat fluxes. The cone calorimeter tests were applied to simulate the situations when the front and back surfaces are exposed to heat flux in a fire, respectively. Through comparison of ignition time, mass loss rate and heat release rate, it is found that the back-up condition is more hazardous than face-up condition. Meanwhile, three key parameters: flashover propensity, total heat release and FED, were introduced to quantitatively illustrate fire hazards of a PV panel.

Scan equalization digital radiography (SEDR) implemented with an amorphous selenium flat-panel detector: initial experience

Energy Technology Data Exchange (ETDEWEB)

Liu Xinming; Lai Chaojen; Chen Lingyun; Han Tao; Zhong Yuncheng; Shen Youtao; Wang Tianpeng; Shaw, Chris C [Department of Imaging Physics, Digital Imaging Research Laboratory, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030-4009 (United States)], E-mail: xliu@di.mdacc.tmc.edu

2009-11-21

It is well recognized in projection radiography that low-contrast detectability suffers in heavily attenuating regions due to excessively low x-ray fluence to the image receptor and higher noise levels. Exposure equalization can improve image quality by increasing the x-ray exposure to heavily attenuating regions, resulting in a more uniform distribution of exposure to the detector. Image quality is also expected to be improved by using the slot-scan geometry to reject scattered radiation effectively without degrading primary x-rays. This paper describes the design of a prototype scan equalization digital radiography (SEDR) system implemented with an amorphous silicon (a-Si) thin-film transistor (TFT) array-based flat-panel detector. With this system, slot-scan geometry with alternate line erasure and readout (ALER) technique was used to achieve scatter rejection. A seven-segment beam height modulator assembly was mounted onto the fore collimator to regulate exposure regionally for chest radiography. The beam modulator assembly, consisting of micro linear motors, lead screw cartridge with lead (Pb) beam blockers attached, position feedback sensors and motor driver circuitry, has been tested and found to have an acceptable response for exposure equalization in chest radiography. An anthropomorphic chest phantom was imaged in the posterior-anterior (PA) view under clinical conditions. Scatter component, primary x-rays, scatter-to-primary ratios (SPRs) and primary signal-to-noise ratios (PSNRs) were measured in the SEDR images to evaluate the rejection and redistribution of scattered radiation, and compared with those for conventional full-field imaging with and without anti-scatter grid methods. SPR reduction ratios (SPRRRs, defined as the differences between the non-grid full-field SPRs and the reduced SPRs divided by the former) yielded approximately 59% for the full-field imaging with grid and 82% for the SEDR technique in the lungs, and 77% for the full

A New Fuzzy-Based Maximum Power Point Tracker for a Solar Panel Based on Datasheet Values

Directory of Open Access Journals (Sweden)

Ali Kargarnejad

2013-01-01

Full Text Available Tracking maximum power point of a solar panel is of interest in most of photovoltaic applications. Solar panel modeling is also very interesting exclusively based on manufacturers data. Knowing that the manufacturers generally give the electrical specifications of their products at one operating condition, there are so many cases in which the specifications in other conditions are of interest. In this research, a comprehensive one-diode model for a solar panel with maximum obtainable accuracy is fully developed only based on datasheet values. The model parameters dependencies on environmental conditions are taken into consideration as much as possible. Comparison between real data and simulations results shows that the proposed model has maximum obtainable accuracy. Then a new fuzzy-based controller to track the maximum power point of the solar panel is also proposed which has better response from speed, accuracy and stability point of view respect to the previous common developed one.

Conical Refraction: new observations and a dual cone model.

Science.gov (United States)

Sokolovskii, G S; Carnegie, D J; Kalkandjiev, T K; Rafailov, E U

2013-05-06

We propose a paraxial dual-cone model of conical refraction involving the interference of two cones of light behind the exit face of the crystal. The supporting experiment is based on beam selecting elements breaking down the conically refracted beam into two separate hollow cones which are symmetrical with one another. The shape of these cones of light is a product of a 'competition' between the divergence caused by the conical refraction and the convergence due to the focusing by the lens. The developed mathematical description of the conical refraction demonstrates an excellent agreement with experiment.

Determination of the scattered radiation at the Neutron Calibration Laboratory of IPEN using the shadow cone method

Energy Technology Data Exchange (ETDEWEB)

Alvarenga, Tallyson S.; Caldas, Linda V.E. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), São Paulo, SP (Brazil); Freitas, Bruno M. [Coordenacao de Pos-Graduacao e Pesquisa de Engenharia (PEN/COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear; Fonseca, Evaldo S.; Pereira, Walsan W., E-mail: talvarenga@ipen.br, E-mail: lcaldas@ipen.br, E-mail: bfreitas@con.ufrj.br, E-mail: walsan@ird.gov.br, E-mail: evaldo@ird.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

2017-07-01

Because of the increase in the demand for the calibration of neutron detectors, there is a need for new calibration services. In this context, the Calibration Laboratory of Instituto de Pesquisas Energéticas e Nucleares (IPEN), São Paulo, which already offers calibration services of radiation detectors with standard X, gamma, beta and alpha beams, has recently projected a new test laboratory for neutron detectors. This work evaluated the contribution of dispersed neutron radiation in this laboratory, using the cone shadow method and a Bonner sphere spectrometer to take the measurements at a distance of 100 cm from the neutron source. The dosimetric quantities H⁎(10) and H⁎(10) were obtained at the laboratory, allowing the calibration of detectors. (author)

Determination of the scattered radiation at the Neutron Calibration Laboratory of IPEN using the shadow cone method

International Nuclear Information System (INIS)

Alvarenga, Tallyson S.; Caldas, Linda V.E.; Freitas, Bruno M.

2017-01-01

Because of the increase in the demand for the calibration of neutron detectors, there is a need for new calibration services. In this context, the Calibration Laboratory of Instituto de Pesquisas Energéticas e Nucleares (IPEN), São Paulo, which already offers calibration services of radiation detectors with standard X, gamma, beta and alpha beams, has recently projected a new test laboratory for neutron detectors. This work evaluated the contribution of dispersed neutron radiation in this laboratory, using the cone shadow method and a Bonner sphere spectrometer to take the measurements at a distance of 100 cm from the neutron source. The dosimetric quantities H⁎(10) and H⁎(10) were obtained at the laboratory, allowing the calibration of detectors. (author)

Progress in light cone physics

International Nuclear Information System (INIS)

Preparata, G.

1973-01-01

A very brief review is given of the progress made in the physics of the light cone in the past year. Included are the light cone expansion, gauge invariance and the consequences of precocious scaling near threshold, the light cone description of the muon pair experiment, light cone expansions, and the assessment and exploitation of analyticity properties in both mass and energy of light cone amplitudes. (U.S.)

Ejecta evolution during cone impact

KAUST Repository

Marston, Jeremy

2014-07-07

We present findings from an experimental investigation into the impact of solid cone-shaped bodies onto liquid pools. Using a variety of cone angles and liquid physical properties, we show that the ejecta formed during the impact exhibits self-similarity for all impact speeds for very low surface tension liquids, whilst for high-surface tension liquids similarity is only achieved at high impact speeds. We find that the ejecta tip can detach from the cone and that this phenomenon can be attributed to the air entrainment phenomenon. We analyse of a range of cone angles, including some ogive cones, and impact speeds in terms of the spatiotemporal evolution of the ejecta tip. Using superhydrophobic cones, we also examine the entry of cones which entrain an air layer.

Cellular automaton-based position sensitive detector equalization

Energy Technology Data Exchange (ETDEWEB)

Ferrando, Nestor [Grupo de Diseno de Sistemas Digitales, Instituto de Aplicaciones de las Tecnologias de la Informacion y de las Comunicaciones Avanzadas, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain)], E-mail: nesferjo@upvnet.upv.es; Herrero, V.; Cerda, J.; Lerche, C.W.; Colom, R.J.; Gadea, R.; Martinez, J.D.; Monzo, J.M.; Mateo, F.; Sebastia, A.; Benlloch, J.M. [Grupo de Diseno de Sistemas Digitales, Instituto de Aplicaciones de las Tecnologias de la Informacion y de las Comunicaciones Avanzadas, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain)

2009-06-01

Indirect position detectors based on scintillator crystals lack of spacial uniformity in their response. This happens due to crystal inhomogeneities and gain differences among the photomultiplier anodes. In order to solve this, PESIC, an integrated front-end for multianode photomultiplier based nuclear imaging devices was created. One of its main features is the digitally programmable gain adjustment for every photomultiplier output. On another front, cellular automata have been proved to be a useful method for dynamic system modeling. In this paper, a cellular automaton which emulates the behavior of the scintillator crystal, the photomultiplier and the front-end is introduced. Thanks to this model, an automatic energy-based calibration of the detector can be done by configuring the cellular automaton with experimental data and making it evolve up to an stable state. This can be useful as a precalibration method of the detector.

Cellular automaton-based position sensitive detector equalization

International Nuclear Information System (INIS)

Ferrando, Nestor; Herrero, V.; Cerda, J.; Lerche, C.W.; Colom, R.J.; Gadea, R.; Martinez, J.D.; Monzo, J.M.; Mateo, F.; Sebastia, A.; Benlloch, J.M.

2009-01-01

Indirect position detectors based on scintillator crystals lack of spacial uniformity in their response. This happens due to crystal inhomogeneities and gain differences among the photomultiplier anodes. In order to solve this, PESIC, an integrated front-end for multianode photomultiplier based nuclear imaging devices was created. One of its main features is the digitally programmable gain adjustment for every photomultiplier output. On another front, cellular automata have been proved to be a useful method for dynamic system modeling. In this paper, a cellular automaton which emulates the behavior of the scintillator crystal, the photomultiplier and the front-end is introduced. Thanks to this model, an automatic energy-based calibration of the detector can be done by configuring the cellular automaton with experimental data and making it evolve up to an stable state. This can be useful as a precalibration method of the detector.

High resolution micro-CT of low attenuating organic materials using large area photon-counting detector

International Nuclear Information System (INIS)

Kumpová, I.; Jandejsek, I.; Jakůbek, J.; Vopálenský, M.; Vavřík, D.; Fíla, T.; Koudelka, P.; Kytýř, D.; Zlámal, P.; Gantar, A.

2016-01-01

To overcome certain limitations of contemporary materials used for bone tissue engineering, such as inflammatory response after implantation, a whole new class of materials based on polysaccharide compounds is being developed. Here, nanoparticulate bioactive glass reinforced gelan-gum (GG-BAG) has recently been proposed for the production of bone scaffolds. This material offers promising biocompatibility properties, including bioactivity and biodegradability, with the possibility of producing scaffolds with directly controlled microgeometry. However, to utilize such a scaffold with application-optimized properties, large sets of complex numerical simulations using the real microgeometry of the material have to be carried out during the development process. Because the GG-BAG is a material with intrinsically very low attenuation to X-rays, its radiographical imaging, including tomographical scanning and reconstructions, with resolution required by numerical simulations might be a very challenging task. In this paper, we present a study on X-ray imaging of GG-BAG samples. High-resolution volumetric images of investigated specimens were generated on the basis of micro-CT measurements using a large area flat-panel detector and a large area photon-counting detector. The photon-counting detector was composed of a 010× 1 matrix of Timepix edgeless silicon pixelated detectors with tiling based on overlaying rows (i.e. assembled so that no gap is present between individual rows of detectors). We compare the results from both detectors with the scanning electron microscopy on selected slices in transversal plane. It has been shown that the photon counting detector can provide approx. 3× better resolution of the details in low-attenuating materials than the integrating flat panel detectors. We demonstrate that employment of a large area photon counting detector is a good choice for imaging of low attenuating materials with the resolution sufficient for numerical

High resolution micro-CT of low attenuating organic materials using large area photon-counting detector

Science.gov (United States)

Kumpová, I.; Vavřík, D.; Fíla, T.; Koudelka, P.; Jandejsek, I.; Jakůbek, J.; Kytýř, D.; Zlámal, P.; Vopálenský, M.; Gantar, A.

2016-02-01

To overcome certain limitations of contemporary materials used for bone tissue engineering, such as inflammatory response after implantation, a whole new class of materials based on polysaccharide compounds is being developed. Here, nanoparticulate bioactive glass reinforced gelan-gum (GG-BAG) has recently been proposed for the production of bone scaffolds. This material offers promising biocompatibility properties, including bioactivity and biodegradability, with the possibility of producing scaffolds with directly controlled microgeometry. However, to utilize such a scaffold with application-optimized properties, large sets of complex numerical simulations using the real microgeometry of the material have to be carried out during the development process. Because the GG-BAG is a material with intrinsically very low attenuation to X-rays, its radiographical imaging, including tomographical scanning and reconstructions, with resolution required by numerical simulations might be a very challenging task. In this paper, we present a study on X-ray imaging of GG-BAG samples. High-resolution volumetric images of investigated specimens were generated on the basis of micro-CT measurements using a large area flat-panel detector and a large area photon-counting detector. The photon-counting detector was composed of a 010× 1 matrix of Timepix edgeless silicon pixelated detectors with tiling based on overlaying rows (i.e. assembled so that no gap is present between individual rows of detectors). We compare the results from both detectors with the scanning electron microscopy on selected slices in transversal plane. It has been shown that the photon counting detector can provide approx. 3× better resolution of the details in low-attenuating materials than the integrating flat panel detectors. We demonstrate that employment of a large area photon counting detector is a good choice for imaging of low attenuating materials with the resolution sufficient for numerical simulations.

Ablation and cone formation mechanism on CR-39 by ArF laser irradiation

Energy Technology Data Exchange (ETDEWEB)

Shakeri Jooybari, B., E-mail: baninshakery@gmail.com, E-mail: hafarideh@aut.ac.ir [Department of Energy Engineering and Physics, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran, Islamic Republic of Iran (Iran, Islamic Republic of); Nuclear Science and Technology Research Institute NSRT, Tehran (Iran, Islamic Republic of); Afarideh, H., E-mail: baninshakery@gmail.com, E-mail: hafarideh@aut.ac.ir [Department of Energy Engineering and Physics, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran, Islamic Republic of Iran (Iran, Islamic Republic of); Lamehi-Rachti, M. [Nuclear Science and Technology Research Institute NSRT, Tehran (Iran, Islamic Republic of); Ghergherehchi, M. [Department of Energy Engineering and Physics, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran, Islamic Republic of Iran (Iran, Islamic Republic of); College of Information and Communication Engineering, Sungkyunkwan University, Suwon (Korea, Republic of)

2015-03-07

In this work, chemical properties, surface modification, and micro structures formation on ablated polyallyl di-glycol carbonate (CR-39) polymer by ArF laser irradiation (λ = 193 nm) at various fluences and pulse number were investigated. CR-39 samples have been irradiated with an ArF laser (193 nm) at a repetition rate of 1 Hz. Threshold fluence of ablation and effective absorption coefficient of CR-39 were determined. Conical microstructures (Taylor cone) formed on laser-ablated CR-39 exhibit: smooth, Taylor cone shape walls and sharp tips together with interference and well defined fringe-structure with a period of 230 nm, around cone base. Mechanism of cone formation and cone evolution of CR-39 ablated surface were investigated by change of fluences (at a given pulse number) and pulse number (at a given fluence). Cone height, cone base, and region of interface were increased in micrometer steps by increasing the total fluence. Depression on the base of the cone and the circular fringe were simulated. FTIR spectra were measured and energy dispersive x-ray analysis of irradiated and un-irradiated samples was performed.

A three-dimensional-weighted cone beam filtered backprojection (CB-FBP) algorithm for image reconstruction in volumetric CT-helical scanning

International Nuclear Information System (INIS)

Tang Xiangyang; Hsieh Jiang; Nilsen, Roy A; Dutta, Sandeep; Samsonov, Dmitry; Hagiwara, Akira

2006-01-01

Based on the structure of the original helical FDK algorithm, a three-dimensional (3D)-weighted cone beam filtered backprojection (CB-FBP) algorithm is proposed for image reconstruction in volumetric CT under helical source trajectory. In addition to its dependence on view and fan angles, the 3D weighting utilizes the cone angle dependency of a ray to improve reconstruction accuracy. The 3D weighting is ray-dependent and the underlying mechanism is to give a favourable weight to the ray with the smaller cone angle out of a pair of conjugate rays but an unfavourable weight to the ray with the larger cone angle out of the conjugate ray pair. The proposed 3D-weighted helical CB-FBP reconstruction algorithm is implemented in the cone-parallel geometry that can improve noise uniformity and image generation speed significantly. Under the cone-parallel geometry, the filtering is naturally carried out along the tangential direction of the helical source trajectory. By exploring the 3D weighting's dependence on cone angle, the proposed helical 3D-weighted CB-FBP reconstruction algorithm can provide significantly improved reconstruction accuracy at moderate cone angle and high helical pitches. The 3D-weighted CB-FBP algorithm is experimentally evaluated by computer-simulated phantoms and phantoms scanned by a diagnostic volumetric CT system with a detector dimension of 64 x 0.625 mm over various helical pitches. The computer simulation study shows that the 3D weighting enables the proposed algorithm to reach reconstruction accuracy comparable to that of exact CB reconstruction algorithms, such as the Katsevich algorithm, under a moderate cone angle (4 deg.) and various helical pitches. Meanwhile, the experimental evaluation using the phantoms scanned by a volumetric CT system shows that the spatial resolution along the z-direction and noise characteristics of the proposed 3D-weighted helical CB-FBP reconstruction algorithm are maintained very well in comparison to the FDK

SU-D-204-05: Quantitative Comparison of a High Resolution Micro-Angiographic Fluoroscopic (MAF) Detector with a Standard Flat Panel Detector (FPD) Using the New Metric of Generalized Measured Relative Object Detectability (GM-ROD)

Energy Technology Data Exchange (ETDEWEB)

Russ, M; Ionita, C; Bednarek, D; Rudin, S [Toshiba Stroke and Vascular Research Center, University at Buffalo (SUNY), Buffalo, NY (United States)

2015-06-15

Purpose: In endovascular image-guided neuro-interventions, visualization of fine detail is paramount. For example, the ability of the interventionist to visualize the stent struts depends heavily on the x-ray imaging detector performance. Methods: A study to examine the relative performance of the high resolution MAF-CMOS (pixel size 75µm, Nyquist frequency 6.6 cycles/mm) and a standard Flat Panel Detector (pixel size 194µm, Nyquist frequency 2.5 cycles/mm) detectors in imaging a neuro stent was done using the Generalized Measured Relative Object Detectability (GM-ROD) metric. Low quantum noise images of a deployed stent were obtained by averaging 95 frames obtained by both detectors without changing other exposure or geometric parameters. The square of the Fourier transform of each image is taken and divided by the generalized normalized noise power spectrum to give an effective measured task-specific signal-to-noise ratio. This expression is then integrated from 0 to each of the detector’s Nyquist frequencies, and the GM-ROD value is determined by taking a ratio of the integrals for the MAF-CMOS to that of the FPD. The lower bound of integration can be varied to emphasize high frequencies in the detector comparisons. Results: The MAF-CMOS detector exhibits vastly superior performance over the FPD when integrating over all frequencies, yielding a GM-ROD value of 63.1. The lower bound of integration was stepped up in increments of 0.5 cycles/mm for higher frequency comparisons. As the lower bound increased, the GM-ROD value was augmented, reflecting the superior performance of the MAF-CMOS in the high frequency regime. Conclusion: GM-ROD is a versatile metric that can provide quantitative detector and task dependent comparisons that can be used as a basis for detector selection. Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation.

Correlation Between Cone Penetration Rate And Measured Cone Penetration Parameters In Silty Soils

DEFF Research Database (Denmark)

Poulsen, Rikke; Nielsen, Benjaminn Nordahl; Ibsen, Lars Bo

2013-01-01

This paper shows, how a change in cone penetration rate affects the cone penetration measurements, hence the cone resistance, pore pressure, and sleeve friction in silty soil. The standard rate of penetration is 20 mm/s, and it is generally accepted that undrained penetration occurs in clay while...... drained penetration occurs in sand. When lowering the penetration rate, the soil pore water starts to dissipate and a change in the drainage condition is seen. In intermediate soils such as silty soils, the standard cone penetration rate may result in a drainage condition that could be undrained......, partially or fully drained. However, lowering the penetration rate in silty soils has a great significance because of the soil permeability, and only a small change in penetration rate will result in changed cone penetration measurements. In this paper, analyses will be done on data from 15 field cone...

Light-cone averaging in cosmology: formalism and applications

International Nuclear Information System (INIS)

Gasperini, M.; Marozzi, G.; Veneziano, G.; Nugier, F.

2011-01-01

We present a general gauge invariant formalism for defining cosmological averages that are relevant for observations based on light-like signals. Such averages involve either null hypersurfaces corresponding to a family of past light-cones or compact surfaces given by their intersection with timelike hypersurfaces. Generalized Buchert-Ehlers commutation rules for derivatives of these light-cone averages are given. After introducing some adapted ''geodesic light-cone'' coordinates, we give explicit expressions for averaging the redshift to luminosity-distance relation and the so-called ''redshift drift'' in a generic inhomogeneous Universe

Evaluation of tilted cone-beam CT orbits in the development of a dedicated hybrid mammotomograph

International Nuclear Information System (INIS)

Madhav, P; Crotty, D J; Tornai, M P; McKinley, R L

2009-01-01

A compact dedicated 3D breast SPECT-CT (mammotomography) system is currently under development. In its initial prototype, the cone-beam CT sub-system is restricted to a fixed-tilt circular rotation around the patient's pendant breast. This study evaluated stationary-tilt angles for the CT sub-system that will enable maximal volumetric sampling and viewing of the breast and chest wall. Images of geometric/anthropomorphic phantoms were acquired using various fixed-tilt circular and 3D sinusoidal trajectories. The iteratively reconstructed images showed more distortion and attenuation coefficient inaccuracy from tilted cone-beam orbits than from the complex trajectory. Additionally, line profiles illustrated cupping artifacts in planes distal to the central plane of the tilted cone-beam, otherwise not apparent for images acquired with complex trajectories. This indicates that undersampled cone-beam data may be an additional cause of cupping artifacts. High-frequency objects could be distinguished for all trajectories, but their shapes and locations were corrupted by out-of-plane frequency information. Although more acrylic balls were visualized with a fixed-tilt and nearly flat cone-beam at the posterior of the breast, 3D complex trajectories have less distortion and more complete sampling throughout the reconstruction volume. While complex trajectories would ideally be preferred, negatively fixed-tilt source-detector configuration demonstrates minimally distorted patient images.

Experiences with radiation portal detectors for international rail transport

Science.gov (United States)

Stromswold, D. C.; McCormick, K.; Todd, L.; Ashbaker, E. D.; Evans, J. C.

2006-08-01

Radiation detectors monitored trains at two international borders to evaluate the performance of NaI(Tl) and plastic (polyvinyltoluene: PVT) gamma-ray detectors to characterize rail cargo. The detectors included a prototype NaI(Tl) radiation-portal-monitor panel having four large detectors (10-cm × 10-cm × 41-cm) and a PVT panel with a 41 cm × 173 cm × 3.8-cm detector. Spectral data from the NaI(Tl) and PVT detectors were recorded. Of particular emphasis was the identification of naturally occurring radioactive material (NORM) and the resultant frequency of nuisance alarms. For rail monitoring, the difficulty in stopping trains to perform secondary inspection on alarming cars creates a need for reliable identification of NORM during initial screening. Approximately 30 trains were monitored, and the commodities in individual railcars were ascertained from manifest information. At one test site, the trains carried inter-modal containers that had been unloaded from ships, and at the other site, the trains contained bulk cargo in tanker cars and hopper cars or individual items in boxcars or flatbeds. NORM encountered included potash, liquefied petroleum gas, fireworks, televisions, and clay-based products (e.g., pottery). Analysis of the spectral data included the use of the template-fitting portion of the program GADRAS developed at Sandia National Laboratories. For most of the NORM, the NaI(Tl) data produced a correct identification of the radionuclides present in the railcars. The same analysis was also used for PVT data in which the spectral information (no peaks but only gradual spectral changes including Compton edges) was limited. However, the PVT analysis provided correct identification of 40K and 226Ra in many cases.

Alpha-particle detection based on the BJT detector and simple, IC-based readout electronics

Energy Technology Data Exchange (ETDEWEB)

Rovati, L; Bonaiuti, M [Dipartimento di Ingegneria dell' Informazione, Universita di Modena e Reggio Emilia, Modena (Italy); Bettarini, S [Dipartimento di Fisica, Universita di Pisa and INFN Pisa, Pisa (Italy); Bosisio, L [Dipartimento di Fisica, Universita di Trieste and INFN Trieste, Trieste (Italy); Dalla Betta, G-F; Tyzhnevyi, V [Dipartimento di Ingegneria e Scienza dell' Informazione, Universita di Trento e INFN Trento, Trento (Italy); Verzellesi, G [Dipartimento di Scienze e Metodi dell' Ingegneria, Universita di Modena e Reggio Emilia and INFN Trento, Reggio Emilia (Italy); Zorzi, N, E-mail: giovanni.verzellesi@unimore.i [Fondazione Bruno Kessler (FBK), Trento (Italy)

2009-11-15

In this paper we propose a portable instrument for alpha-particle detection based on a previously-developed BJT detector and a simple, IC-based readout electronics. Experimental tests of the BJT detector and readout electronics are reported. Numerical simulations are adopted to predict the performance enhancement achievable with optimized BJT detectors.

Alpha-particle detection based on the BJT detector and simple, IC-based readout electronics

International Nuclear Information System (INIS)

Rovati, L; Bonaiuti, M; Bettarini, S; Bosisio, L; Dalla Betta, G-F; Tyzhnevyi, V; Verzellesi, G; Zorzi, N

2009-01-01

In this paper we propose a portable instrument for alpha-particle detection based on a previously-developed BJT detector and a simple, IC-based readout electronics. Experimental tests of the BJT detector and readout electronics are reported. Numerical simulations are adopted to predict the performance enhancement achievable with optimized BJT detectors.

Comparison of interplanetary CME arrival times and solar wind parameters based on the WSA-ENLIL model with three cone types and observations

Science.gov (United States)

Jang, Soojeong; Moon, Y.-J.; Lee, Jae-Ok; Na, Hyeonock

2014-09-01

We have made a comparison between coronal mass ejection (CME)-associated shock propagations based on the Wang-Sheeley-Arge (WSA)-ENLIL model using three cone types and in situ observations. For this we use 28 full-halo CMEs, whose cone parameters are determined and their corresponding interplanetary shocks were observed at the Earth, from 2001 to 2002. We consider three different cone types (an asymmetric cone model, an ice cream cone model, and an elliptical cone model) to determine 3-D CME cone parameters (radial velocity, angular width, and source location), which are the input values of the WSA-ENLIL model. The mean absolute error of the CME-associated shock travel times for the WSA-ENLIL model using the ice-cream cone model is 9.9 h, which is about 1 h smaller than those of the other models. We compare the peak values and profiles of solar wind parameters (speed and density) with in situ observations. We find that the root-mean-square errors of solar wind peak speed and density for the ice cream and asymmetric cone model are about 190 km/s and 24/cm3, respectively. We estimate the cross correlations between the models and observations within the time lag of ± 2 days from the shock travel time. The correlation coefficients between the solar wind speeds from the WSA-ENLIL model using three cone types and in situ observations are approximately 0.7, which is larger than those of solar wind density (cc ˜0.6). Our preliminary investigations show that the ice cream cone model seems to be better than the other cone models in terms of the input parameters of the WSA-ENLIL model.

Exact Reconstruction From Uniformly Attenuated Helical Cone-Beam Projections in SPECT

International Nuclear Information System (INIS)

Gullberg, Grant T.; Huang, Qiu; You, Jiangsheng; Zeng, Gengsheng L.

2008-01-01

In recent years the development of cone-beam reconstruction algorithms has been an active research area in x-ray computed tomography (CT), and significant progress has been made in the advancement of algorithms. Theoretically exact and computationally efficient analytical algorithms can be found in the literature. However, in single photon emission computed tomography (SPECT), published cone-beam reconstruction algorithms are either approximate or involve iterative methods. The SPECT reconstruction problem is more complicated due to degradations in the imaging detection process, one of which is the effect of attenuation of gamma ray photons. Attenuation should be compensated for to obtain quantitative results. In this paper, an analytical reconstruction algorithm for uniformly attenuated cone-beam projection data is presented for SPECT imaging. The algorithm adopts the DBH method, a procedure consisting of differentiation and backprojection followed by a finite inverse cosh-weighted Hilbert transform. The significance of the proposed approach is that a selected region of interest can be reconstructed even with a detector with a reduced field of view. The algorithm is designed for a general trajectory. However, to validate the algorithm, a numerical study was performed using a helical trajectory. The implementation is efficient and the simulation result is promising

Benign Prostatic Hyperplasia: Cone-Beam CT in Conjunction with DSA for Identifying Prostatic Arterial Anatomy.

Science.gov (United States)

Wang, Mao Qiang; Duan, Feng; Yuan, Kai; Zhang, Guo Dong; Yan, Jieyu; Wang, Yan

2017-01-01

Purpose To describe findings in prostatic arteries (PAs) at digital subtraction angiography (DSA) and cone-beam computed tomography (CT) that allow identification of benign prostatic hyperplasia and to determine the value added with the use of cone-beam CT. Materials and Methods This retrospective single-institution study was approved by the institutional review board, and the requirement for written informed consent was waived. From February 2009 to December 2014, a total of 148 patients (mean age ± standard deviation, 70.5 years ± 14.5) underwent DSA of the internal iliac arteries and cone-beam CT with a flat-detector angiographic system before they underwent prostate artery embolization. Both the DSA and cone-beam CT images were evaluated by two interventional radiologists to determine the number of independent PAs and their origins and anastomoses with adjacent arteries. The exact McNemar test was used to compare the detection rate of the PAs and the anastomoses with DSA and with cone-beam CT. Results The PA anatomy was evaluated successfully by means of cone-beam CT in conjunction with DSA in all patients. Of the 296 pelvic sides, 274 (92.6%) had only one PA. The most frequent PA origin was the common gluteal-pudendal trunk with the superior vesicular artery in 118 (37.1%), followed by the anterior division of the internal iliac artery in 99 (31.1%), and the internal pudendal artery in 77 (24.2%) pelvic sides. In 67 (22.6%) pelvic sides, anastomoses to adjacent arteries were documented. The numbers of PA origins and anastomoses, respectively, that could be identified were significantly higher with cone-beam CT (301 of 318 [94.7%] and 65 of 67 [97.0%]) than with DSA (237 [74.5%] and 39 [58.2%], P < .05). Cone-beam CT provided essential information that was not available with DSA in 90 of 148 (60.8%) patients. Conclusion Cone-beam CT is a useful adjunctive technique to DSA for identification of the PA anatomy and provides information to help treatment planning

Fabrication of 1m x 1m readout strips panel and quality verification of new set of SFS dielectric material

International Nuclear Information System (INIS)

Kumar, A.; Pandey, A.; Sogarwal, Hariom; Marimuthu, N.; Singh, V.; Subrahmanyam, V.S.

2016-01-01

India based Neutrino Observatory (INO) is going to use ∼ 30,000 Resistive Plate Chamber (RPC) as an active detector. Resistive Plate chambers are parallel plate fast gaseous detector made up of high resistivity (10"1"2 ohm) of glass or bakelite. Glass plates work as electrodes of positive and negative potential. When a charged particle passes through chamber it ionizes the gas and charge move towards opposite electrodes. The pick-up panels pick these signals. Signals are sent to front end electronics. The characteristic impedance of the strips of the panels should be matched with front end electronics which helps in minimizing the reflected signal. Since INO is an underground laboratory, all material used in it must be fireproof. Since ∼ 60,000 pick-up panels are going to be used in INO hence it should be cheaper also. We recently received a new set of Silicon Fiber Sheets - a dielectric material, of 25 pieces of 1m x 0.5m having thickness 05 mm. We fabricated a set of readout strips panel of dimension 1m x 1m. We will present this work in detail

Silicon-Based Detectors at the HL-LHC

CERN Document Server

Hartmann, Frank

2018-01-01

This document discusses the silicon-based detectors planned for the High Luminosity LHC. The special aspects to cope with the new environment and its challenges, e.g. very high radiation levels and very high instantaneous luminosity thus high pile-up, high occupancy and high data rates, are addressed. The different design choices of the detectors are put into perspective. Exciting topics like trackers, high granularity silicon-based calorimetry with novel 8~inch processing, fast timing and new triggers are described.

Fatigue behavior of wood-fiber-based tri-axial engineered sandwich composite panels (ESCP)

Science.gov (United States)

Jinghao Li; John F. Hunt; Shaoqin Gong; Zhiyong Cai

2015-01-01

The static and fatigue bending behavior of wood-fiber-based tri-axial engineered sandwich composite panels (ESCP) has been investigated by four-point bending tests. Fatigue panels and weakened panels (wESCP) with an initial interface defect were manufactured for the fatigue tests. Stress σ vs. number of cycles curves (S-N) were recorded under the different stress...

The utility of breast cone-beam computed tomography, ultrasound, and digital mammography for detecting malignant breast tumors: A prospective study with 212 patients.

Science.gov (United States)

He, Ni; Wu, Yao-Pan; Kong, Yanan; Lv, Ning; Huang, Zhi-Mei; Li, Sheng; Wang, Yue; Geng, Zhi-Jun; Wu, Pei-Hong; Wei, Wei-Dong

2016-02-01

Breast cone-beam computed tomography (BCBCT) is a flat-panel detector (FPD)-based X-ray imaging system that provides high-quality images of the breast. The purpose of this study was to investigate the ability to detect breast abnormalities using non-contrast BCBCT and contrast-enhanced BCBCT (BCBCT and CE-BCBCT) compared to ultrasound (US) and digital mammography (MG). A prospective study was performed from May 2012 to August 2014. Ninety-two patients (172 lesions) underwent BCBCT alone, and 120 patients (270 lesions) underwent BCBCT and CE-BCBCT, all the patients underwent US and MG. Cancer diagnosis was confirmed pathologically in 102 patients (110 lesions). BCBCT identified 97 of 110 malignant lesions, whereas 93 malignant lesions were identified using MG and US. The areas under the receiver operating curves (AUCs) for breast cancer diagnosis were 0.861 (BCBCT), 0.856 (US), and 0.829 (MG). CE-BCBCT improved cancer diagnostic sensitivity by 20.3% (78.4-98.7%). The AUC values were 0.869 (CE-BCBCT), 0.846 (BCBCT), 0.834 (US), and 0.782 (MG). In this preliminary study, BCBCT was found to accurately identify malignant breast lesions in a diagnostic setting. CE-BCBCT provided additional information and improved cancer diagnosis in style c or d breasts compared to the use of BCBCT, US, or MG alone. Copyright © 2015. Published by Elsevier Ireland Ltd.

Cone rod dystrophies

Science.gov (United States)

Hamel, Christian P

2007-01-01

Cone rod dystrophies (CRDs) (prevalence 1/40,000) are inherited retinal dystrophies that belong to the group of pigmentary retinopathies. CRDs are characterized by retinal pigment deposits visible on fundus examination, predominantly localized to the macular region. In contrast to typical retinitis pigmentosa (RP), also called the rod cone dystrophies (RCDs) resulting from the primary loss in rod photoreceptors and later followed by the secondary loss in cone photoreceptors, CRDs reflect the opposite sequence of events. CRD is characterized by primary cone involvement, or, sometimes, by concomitant loss of both cones and rods that explains the predominant symptoms of CRDs: decreased visual acuity, color vision defects, photoaversion and decreased sensitivity in the central visual field, later followed by progressive loss in peripheral vision and night blindness. The clinical course of CRDs is generally more severe and rapid than that of RCDs, leading to earlier legal blindness and disability. At end stage, however, CRDs do not differ from RCDs. CRDs are most frequently non syndromic, but they may also be part of several syndromes, such as Bardet Biedl syndrome and Spinocerebellar Ataxia Type 7 (SCA7). Non syndromic CRDs are genetically heterogeneous (ten cloned genes and three loci have been identified so far). The four major causative genes involved in the pathogenesis of CRDs are ABCA4 (which causes Stargardt disease and also 30 to 60% of autosomal recessive CRDs), CRX and GUCY2D (which are responsible for many reported cases of autosomal dominant CRDs), and RPGR (which causes about 2/3 of X-linked RP and also an undetermined percentage of X-linked CRDs). It is likely that highly deleterious mutations in genes that otherwise cause RP or macular dystrophy may also lead to CRDs. The diagnosis of CRDs is based on clinical history, fundus examination and electroretinogram. Molecular diagnosis can be made for some genes, genetic counseling is always advised. Currently

Cone rod dystrophies

Directory of Open Access Journals (Sweden)

Hamel Christian P

2007-02-01

Full Text Available Abstract Cone rod dystrophies (CRDs (prevalence 1/40,000 are inherited retinal dystrophies that belong to the group of pigmentary retinopathies. CRDs are characterized by retinal pigment deposits visible on fundus examination, predominantly localized to the macular region. In contrast to typical retinitis pigmentosa (RP, also called the rod cone dystrophies (RCDs resulting from the primary loss in rod photoreceptors and later followed by the secondary loss in cone photoreceptors, CRDs reflect the opposite sequence of events. CRD is characterized by primary cone involvement, or, sometimes, by concomitant loss of both cones and rods that explains the predominant symptoms of CRDs: decreased visual acuity, color vision defects, photoaversion and decreased sensitivity in the central visual field, later followed by progressive loss in peripheral vision and night blindness. The clinical course of CRDs is generally more severe and rapid than that of RCDs, leading to earlier legal blindness and disability. At end stage, however, CRDs do not differ from RCDs. CRDs are most frequently non syndromic, but they may also be part of several syndromes, such as Bardet Biedl syndrome and Spinocerebellar Ataxia Type 7 (SCA7. Non syndromic CRDs are genetically heterogeneous (ten cloned genes and three loci have been identified so far. The four major causative genes involved in the pathogenesis of CRDs are ABCA4 (which causes Stargardt disease and also 30 to 60% of autosomal recessive CRDs, CRX and GUCY2D (which are responsible for many reported cases of autosomal dominant CRDs, and RPGR (which causes about 2/3 of X-linked RP and also an undetermined percentage of X-linked CRDs. It is likely that highly deleterious mutations in genes that otherwise cause RP or macular dystrophy may also lead to CRDs. The diagnosis of CRDs is based on clinical history, fundus examination and electroretinogram. Molecular diagnosis can be made for some genes, genetic counseling is

Norm based design of fault detectors

DEFF Research Database (Denmark)

Rank, Mike Lind; Niemann, Hans Henrik

1999-01-01

The design of fault detectors for fault detection and isolation (FDI) in dynamic systems is considered in this paper from a norm based point of view. An analysis of norm based threshold selection is given based on different formulations of FDI problems. Both the nominal FDI problem as well...

Chloride currents in cones modify feedback from horizontal cells to cones in goldfish retina

Science.gov (United States)

Endeman, Duco; Fahrenfort, Iris; Sjoerdsma, Trijntje; Steijaert, Marvin; ten Eikelder, Huub; Kamermans, Maarten

2012-01-01

In neuronal systems, excitation and inhibition must be well balanced to ensure reliable information transfer. The cone/horizontal cell (HC) interaction in the retina is an example of this. Because natural scenes encompass an enormous intensity range both in temporal and spatial domains, the balance between excitation and inhibition in the outer retina needs to be adaptable. How this is achieved is unknown. Using electrophysiological techniques in the isolated retina of the goldfish, it was found that opening Ca2+-dependent Cl− channels in recorded cones reduced the size of feedback responses measured in both cones and HCs. Furthermore, we show that cones express Cl− channels that are gated by GABA released from HCs. Similar to activation of ICl(Ca), opening of these GABA-gated Cl− channels reduced the size of light-induced feedback responses both in cones and HCs. Conversely, application of picrotoxin, a blocker of GABAA and GABAC receptors, had the opposite effect. In addition, reducing GABA release from HCs by blocking GABA transporters also led to an increase in the size of feedback. Because the independent manipulation of Ca2+-dependent Cl− currents in individual cones yielded results comparable to bath-applied GABA, it was concluded that activation of either Cl− current by itself is sufficient to reduce the size of HC feedback. However, additional effects of GABA on outer retinal processing cannot be excluded. These results can be accounted for by an ephaptic feedback model in which a cone Cl− current shunts the current flow in the synaptic cleft. The Ca2+-dependent Cl− current might be essential to set the initial balance between the feedforward and the feedback signals active in the cone HC synapse. It prevents that strong feedback from HCs to cones flood the cone with Ca2+. Modulation of the feedback strength by GABA might play a role during light/dark adaptation, adjusting the amount of negative feedback to the signal to noise ratio of the

Optimization of shadow cone length and mass for determination the amount of scattered radiation dose in the calibration laboratory of Am/Be neutron source

International Nuclear Information System (INIS)

Raisali, G.; Hamidi, S.; Hallajfard, E.; Shahvar, A.; Hajiloo, N.

2007-01-01

The shadow cone technique is one of the methods which is used for determining the contribution of scattered particles on the response of neutron detectors. This technique is used for neutron field calibration in Agriculture, Medicine and Industry Research School. In this investigation, we have designed and constructed an optimized shadow cone. According to the calculated neutron dose equivalent attenuation factors, a cone with 20 cm of iron and 30 cm of polyethylene has been found as optimum. For this cone, the neutron dose equivalent attenuation factor for 241 Am/Be neutron source, is 0.00035 for which the contribution of scattered neutrons in Agriculture, Medicine and Industry Research School neutron calibration laboratory according to the calculation and measurement results, can be evaluated with less than 0.5% of error

Comparison of the WSA-ENLIL model with three CME cone types

Science.gov (United States)

Jang, Soojeong; Moon, Y.; Na, H.

2013-07-01

We have made a comparison of the CME-associated shock propagation based on the WSA-ENLIL model with three cone types using 29 halo CMEs from 2001 to 2002. These halo CMEs have cone model parameters as well as their associated interplanetary (IP) shocks. For this study we consider three different cone types (an asymmetric cone model, an ice-cream cone model and an elliptical cone model) to determine 3-D CME parameters (radial velocity, angular width and source location), which are the input values of the WSA-ENLIL model. The mean absolute error (MAE) of the arrival times for the asymmetric cone model is 10.6 hours, which is about 1 hour smaller than those of the other models. Their ensemble average of MAE is 9.5 hours. However, this value is still larger than that (8.7 hours) of the empirical model of Kim et al. (2007). We will compare their IP shock velocities and densities with those from ACE in-situ measurements and discuss them in terms of the prediction of geomagnetic storms.Abstract (2,250 Maximum Characters): We have made a comparison of the CME-associated shock propagation based on the WSA-ENLIL model with three cone types using 29 halo CMEs from 2001 to 2002. These halo CMEs have cone model parameters as well as their associated interplanetary (IP) shocks. For this study we consider three different cone types (an asymmetric cone model, an ice-cream cone model and an elliptical cone model) to determine 3-D CME parameters (radial velocity, angular width and source location), which are the input values of the WSA-ENLIL model. The mean absolute error (MAE) of the arrival times for the asymmetric cone model is 10.6 hours, which is about 1 hour smaller than those of the other models. Their ensemble average of MAE is 9.5 hours. However, this value is still larger than that (8.7 hours) of the empirical model of Kim et al. (2007). We will compare their IP shock velocities and densities with those from ACE in-situ measurements and discuss them in terms of the

CT Scans of NASA BSTRA Balls 5f5, f2, f3, sr2c, nb2a, hb2b

International Nuclear Information System (INIS)

Gross, J; Thompson, R; Perry, R; Schneberk, D

2004-01-01

At the request of Jose Hernandez we performed some feasibility DR/CT scanning of BSTRA Balls of different sizes. To this point we have scanned all the specimens on a single system, HECAT. This particular system employs a 9 meV LINAC as the x-ray source and a THALES 12 x 16 inch 14-bit Amorphous Silicon panel as the detector. In this report we describe the system, detail some of its properties, describe the scans performed and present the data. Figure 1 contains a couple of images of the system as fielded in the 9 MeV bay. The LINAC is in the right portion of the picture. The black panels in the blue frame constitute the High Energy collimator developed specifically for High Energy DR/CT scanning (known here as Stonehenge II). The holes in the collimator panels are beveled to match the distribution of the x-rays from the LINAC, and are sized to just subtend the active area of the THALES Amorphous Silicon panel. Consequently the source to detector distance is restricted to a few positions. Nominally our source to detector distance is 6 meters. The part manipulator, part holder fixturing consists of a translate-rotate assembly on a NEWPORT air bearing table. The stages are NEWPORT RV160PP for rotation and NEWPORT IMS400CC for translation. Both are interfaced through an ESP7000 controller, which is connected to our data acquisition computer over USB. The detector holder also resides on this table and includes pitch, roll and yaw adjustments for aligning the panel to the plane of the rotational table and the x-ray beam. The relatively large source to detector distance and LINAC properties (1 mm spot size) conspire to recommend rotation-only scanning. We use a VARIAN LINATRON 3000 with the small spot retrofit implemented. We have measured the source spot size at about 1 mm. Pixel size on the THALES panel is 0.127 um. Consequently we are in a low-cone angle scanning regime which enables rotation-only 3D CT scanning of objects and assemblies with little ''cone

Data quality in probability-based online panels: Nonresponse, attrition, and panel conditioning

NARCIS (Netherlands)

Struminskaya, B.; Methodology and statistics for the behavioural and social sciences

2014-01-01

Online panels – surveys administered over the Internet in which persons are asked to complete surveys regularly – offer cost reductions compared to surveys that use more traditional modes of data collection (face-to-face, telephone, and mail). However, some characteristics of online panels may cause

Ageing tests study on wood-based sandwich panels

Directory of Open Access Journals (Sweden)

Mateo, Raquel

2011-12-01

Full Text Available Composite lightweight wood panels are being increasingly used in construction in Spain. Their growing use should be accompanied by necessary guarantees based on studies of their properties. As it is prescriptive and in addition to others tests, in the present work is examinated the durability of these panels when exposed to the climatic conditions, a characteristic of great importance for wood products, according to Guide ETAG 016, the current standard defining the ageing tests to be used. However, due to the use class of this material, there are indications that the testing outlined in this Guide is inappropriate for assessing the ageing of wood-based sandwich panels. Alternative tests are here proposed that recreate rather better the real conditions under which these products are used. Covering the samples in a waterproof sheeting permeable to the outward movement of water vapour, which is in fact used in the installation, provided the best procedure for testing these panels.

Los paneles sándwich de madera son un producto de creciente aplicación en la edificación de nuestro país. Este ascendente uso del material debe estar acompañado de las garantías necesarias avaladas por un estudio previo de sus prestaciones. Como es preceptivo y entre otros, se evalúa su durabilidad frente a las condiciones climatológicas, clave en los productos derivados de la madera, acorde a la normativa actual definida con tal fin, la Guía ETAG 016. Sin embargo, debido a la clase de uso del material, se ha detectado que dicha normativa tal y como está concebida no es capaz de valorar su envejecimiento adecuadamente. En este trabajo se proponen ensayos alternativos al establecido tras exhaustivos análisis que recrean las condiciones reales de uso y más acordes a los productos de madera. Se concluye que la incorporación de una lámina impermeable pero permeable al vapor de agua hacia el exterior, como las utilizadas en el montaje, aportan el mejor

Effective lifetime of minority carriers in black silicon nano-textured by cones and pyramids

DEFF Research Database (Denmark)

Onyshchenko, V.F.; Karachevtseva, L.A.; Lytvynenko, O.O.

2017-01-01

We calculated the dependence of effective lifetime of minority carriers in black silicon nano-textured by cones and pyramids on the diameter of the cone base, the side of the pyramid base, the height of cone and pyramid. The numerical calculation shows that n-type polished plate of single crystal...

Noise masking of S-cone increments and decrements.

Science.gov (United States)

Wang, Quanhong; Richters, David P; Eskew, Rhea T

2014-11-12

S-cone increment and decrement detection thresholds were measured in the presence of bipolar, dynamic noise masks. Noise chromaticities were the L-, M-, and S-cone directions, as well as L-M, L+M, and achromatic (L+M+S) directions. Noise contrast power was varied to measure threshold Energy versus Noise (EvN) functions. S+ and S- thresholds were similarly, and weakly, raised by achromatic noise. However, S+ thresholds were much more elevated by S, L+M, L-M, L- and M-cone noises than were S- thresholds, even though the noises consisted of two symmetric chromatic polarities of equal contrast power. A linear cone combination model accounts for the overall pattern of masking of a single test polarity well. L and M cones have opposite signs in their effects upon raising S+ and S- thresholds. The results strongly indicate that the psychophysical mechanisms responsible for S+ and S- detection, presumably based on S-ON and S-OFF pathways, are distinct, unipolar mechanisms, and that they have different spatiotemporal sampling characteristics, or contrast gains, or both. © 2014 ARVO.

An Analysis Model for Water Cone Subsidence in Bottom Water Drive Reservoirs

Science.gov (United States)

Wang, Jianjun; Xu, Hui; Wu, Shucheng; Yang, Chao; Kong, lingxiao; Zeng, Baoquan; Xu, Haixia; Qu, Tailai

2017-12-01

Water coning in bottom water drive reservoirs, which will result in earlier water breakthrough, rapid increase in water cut and low recovery level, has drawn tremendous attention in petroleum engineering field. As one simple and effective method to inhibit bottom water coning, shut-in coning control is usually preferred in oilfield to control the water cone and furthermore to enhance economic performance. However, most of the water coning researchers just have been done on investigation of the coning behavior as it grows up, the reported studies for water cone subsidence are very scarce. The goal of this work is to present an analytical model for water cone subsidence to analyze the subsidence of water cone when the well shut in. Based on Dupuit critical oil production rate formula, an analytical model is developed to estimate the initial water cone shape at the point of critical drawdown. Then, with the initial water cone shape equation, we propose an analysis model for water cone subsidence in bottom water reservoir reservoirs. Model analysis and several sensitivity studies are conducted. This work presents accurate and fast analytical model to perform the water cone subsidence in bottom water drive reservoirs. To consider the recent interests in development of bottom drive reservoirs, our approach provides a promising technique for better understanding the subsidence of water cone.

3D Modeling of Electric Fields in the LUX Detector

OpenAIRE

LUX Collaboration; Akerib, D. S.; Alsum, S.; Araújo, H. M.; Bai, X.; Bailey, A. J.; Balajthy, J.; Beltrame, P.; Bernard, E. P.; Bernstein, A.; Biesiadzinski, T. P.; Boulton, E. M.; Brás, P.; Byram, D.; Cahn, S. B.

2017-01-01

This work details the development of a three-dimensional (3D) electric field model for the LUX detector. The detector took data during two periods of searching for weakly interacting massive particle (WIMP) searches. After the first period completed, a time-varying non-uniform negative charge developed in the polytetrafluoroethylene (PTFE) panels that define the radial boundary of the detector's active volume. This caused electric field variations in the detector in time, depth and azimuth, g...

The Usefulness of Three-Dimensional Angiography with a Flat Panel Detector of Direct Conversion Type in a Transcatheter Arterial Chemoembolization Procedure for Hepatocellular Carcinoma: Initial Experience

International Nuclear Information System (INIS)

Kakeda, Shingo; Korogi, Yukunori; Hatakeyama, Yoshihisa; Ohnari, Norihiro; Oda, Nobuhiro; Nishino, Kazuyoshi; Miyamoto, Wataru

2008-01-01

The purpose of this study was to assess the usefulness of a three-dimensional (3D) angiography system using a flat panel detector of direct conversion type in treatments with subsegmental transcatheter arterial chemoembolization (TACE) for hepatocellular carcinomas (HCCs). Thirty-six consecutive patients who underwent hepatic angiography were prospectively examined. First, two radiologists evaluated the degree of visualization of the peripheral branches of the hepatic arteries on 3D digital subtraction angiography (DSA). Then the radiologists evaluated the visualization of tumor staining and feeding arteries in 25 patients (30 HCCs) who underwent subsegmental TACE. The two radiologists who performed the TACE assessed whether the additional information provided by 3D DSA was useful for treatments. In 34 (94.4%) of 36 patients, the subsegmental branches of the hepatic arteries were sufficiently visualized. The feeding arteries of HCCs were sufficiently visualized in 28 (93%) of 30 HCCs, whereas tumor stains were sufficiently visualized in 18 (60%). Maximum intensity projection images were significantly superior to volume recording images for visualization of the tumor staining and feeding arteries of HCCs. In 27 (90%) of 30 HCCs, 3D DSA provided additional useful information for subsegmental TACE. The high-quality 3D DSA with flat panel detector angiography system provided a precise vascular road map, which was useful for performing subsegmental TACE .of HCCs

Chemical profile of Taxodium distichum winter cones

Directory of Open Access Journals (Sweden)

Đapić Nina M.

2017-01-01

Full Text Available This work is concerned with the chemical profile of Taxodium distichum winter cones. The extract obtained after maceration in absolute ethanol was subjected to qualitative analysis by gas chromatography/mass spectrometry and quantification was done by gas chromatography/ flame ionization detector. The chromatogram revealed the presence of 53 compounds, of which 33 compounds were identified. The extract contained oxygenated monoterpenes (12.42%, sesquiterpenes (5.18%, oxygenated sesquiterpenes (17.41%, diterpenes (1.15%, and oxygenated diterpenes (30.87%, while the amount of retinoic acid was 0.32%. Monoacylglycerols were detected in the amount of 4.32%. The most abundant compounds were: caryophyllene oxide (14.27%, 6,7-dehydro-ferruginol (12.49%, bornyl acetate (10.96%, 6- deoxy-taxodione (9.50% and trans-caryophyllene (4.20%.

Review on resonance cone fields

International Nuclear Information System (INIS)

Ohnuma, Toshiro.

1980-02-01

Resonance cone fields and lower hybrid heating are reviewed in this report. The resonance cone fields were reported by Fisher and Gould, and they proposed the use of the measurement of resonance cones and structure as a diagnostic tool to determine the plasma density and electron temperature in magnetoplasma. After the resonance cone, a wave-like disturbance persists. Ohnuma et al. have measured bending, reflection and ducting of resonance cones in detail. The thermal modes in inhomogeneous magnetoplasma were seen. The reflection of thermal mode near an electron plasma frequency layer and an insulating plate has been observed. The non-linear effects of resonance cones is reported. Monochromatic electron beam produces the noise of broad band whistler mode. Lower hybrid waves have been the subject of propagation from the edge of plasma to the lower hybrid layer. Linear lower hybrid waves were studied. The lower hybrid and ion acoustic waves radiated from a point source were observed. The parametric decay of finite-extent, cold electron plasma waves was studied. The lower hybrid cone radiated from a point source going along magnetic field lines was observed. Several experimental data on the lower hybrid heating in tokamak devices have been reported. The theories on resonance cones and lower hybrid waves are introduced in this report. (Kato, T.)

Feasibility of using cone penetrometer truck (CPT) to install time domain reflectometry (TDR) and fiber optic slope failure detectors in pavement structures.

Science.gov (United States)

2011-02-01

A new method of cable installation using a heavy-duty Cone Penetration Test : (CPT) truck was developed and practiced successfully in this study. The coaxial and fiber : optic cables were pushed along with the cone rods by the hydraulic system integr...

Understanding the cone scale in Cupressaceae: insights from seed-cone teratology in Glyptostrobus pensilis.

Science.gov (United States)

Dörken, Veit Martin; Rudall, Paula J

2018-01-01

Both wild-type and teratological seed cones are described in the monoecious conifer Glyptostrobus pensilis and compared with those of other Cupressaceae sensu lato and other conifers. Some Cupressaceae apparently possess a proliferation of axillary structures in their cone scales. In our interpretation, in Glyptostrobus each bract of both typical and atypical seed cones bears two descending accessory shoots, interpreted here as seed scales (ovuliferous scales). The primary seed scale is fertile and forms the ovules, the second is sterile and forms characteristic tooth-like structures. The bract and the two axillary seed scales are each supplied with a single distinct vascular bundle that enters the cone axis as a separate strand; this vasculature also characterises the descending accessory short shoots in the vegetative parts of the crown. In wild-type seed cones, the fertile seed scale is reduced to its ovules, and the ovules are always axillary. In contrast, the ovules of some of the teratological seed cones examined were located at the centre of the cone scale. An additional tissue found on the upper surface of the sterile lower seed scale is here interpreted as the axis of the fertile seed scale. Thus, the central position of the ovules can be explained by recaulescent fusion of the upper fertile and lower sterile seed scales. In several teratological cone scales, the ovules were enveloped by an additional sterile tissue that is uniseriate and represents an epidermal outgrowth of the fertile seed scale. Close to the ovules, the epidermis was detached from lower tissue and surrounded the ovule completely, except at the micropyle. These teratological features are potentially significant in understanding seed-cone homologies among extant conifers.

Use of informatics in radiation control panels

International Nuclear Information System (INIS)

Cochinal, R.; Grimont, B.; Mai, V.

1980-03-01

Radiation control panels with programmed systems have developed at the CEA over the last few years. Each monitored location is provided with an monitoring station containing: - a radiation detector and associated electronics (the output signal is normalised calibrated pulses), - an alarm unit to warn personnal of any danger inside the detection zone covered [fr

Photoacoustic-based detector for infrared laser spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Scholz, L.; Palzer, S., E-mail: stefan.palzer@imtek.uni-freiburg.de [Department of Microsystems Engineering-IMTEK, Laboratory for Gas Sensors, University of Freiburg, Georges-Köhler-Allee 102, Freiburg 79110 (Germany)

2016-07-25

In this contribution, we present an alternative detector technology for use in direct absorption spectroscopy setups. Instead of a semiconductor based detector, we use the photoacoustic effect to gauge the light intensity. To this end, the target gas species is hermetically sealed under excess pressure inside a miniature cell along with a MEMS microphone. Optical access to the cell is provided by a quartz window. The approach is particularly suitable for tunable diode laser spectroscopy in the mid-infrared range, where numerous molecules exhibit large absorption cross sections. Moreover, a frequency standard is integrated into the method since the number density and pressure inside the cell are constant. We demonstrate that the information extracted by our method is at least equivalent to that achieved using a semiconductor-based photon detector. As exemplary and highly relevant target gas, we have performed direct spectroscopy of methane at the R3-line of the 2v{sub 3} band at 6046.95 cm{sup −1} using both detector technologies in parallel. The results may be transferred to other infrared-active transitions without loss of generality.

Thermoelectrically induced nonlinear free vibration analysis of piezo laminated composite conical shell panel with random fiber orientation

Directory of Open Access Journals (Sweden)

Lal Achchhe

2017-09-01

Full Text Available This paper presents the free vibration response of piezo laminated composite geometrically nonlinear conical shell panel subjected to a thermo-electrical loading. The temperature field is assumed to be a uniform distribution over the shell surface and through the shell thickness and the electric field is assumed to be the transverse component E2 only. The material properties are assumed to be independent of the temperature and the electric field. The basic formulation is based on higher order shear deformation plate theory (HSDT with von-Karman nonlinearity. A C0 nonlinear finite element method based on direct iterative approach is outlined and applied to solve nonlinear generalized eigenvalue problem. Parametric studies are carried out to examine the effect of amplitude ratios, stacking sequences, cone angles, piezoelectric layers, applied voltages, circumferential length to thickness ratios, change in temperatures and support boundary conditions on the nonlinear natural frequency of laminated conical shell panels. The present outlined approach has been validated with those available results in the literature.

TU-EF-207-04: Advances in Detector Technology for Breast Tomosynthesis

Energy Technology Data Exchange (ETDEWEB)

Zhao, W. [SUNY Stony Brook (United States)

2015-06-15

mode due to lower photon fluence per projection. This may require fast-frame acquisition and symmetric or asymmetric pixel binning in some systems. Recent studies investigated the performance of increased conversion layer thickness for contrast-enhanced imaging of the breast in dual-energy acquisition mode. In other direct conversion detectors operating in the avalanche mode, sensitivities close to the single photon response are also explored for mammography and breast tomosynthesis. The potential advantages and challenges of this approach are described. Dedicated breast CT brings x-ray imaging of the breast to true tomographic 3D imaging. It can eliminate the tissue superposition problem and does not require physical compression of the breast. Using cone beam geometry and a flat-panel detector, several hundred projections are acquired and reconstructed to near isotropic voxels. Multiplanar reconstruction facilitates viewing the breast volume in any desired orientation. Ongoing clinical studies, the current state-of-the art, and research to advance the technology are described. Learning Objectives: To understand the ongoing developments in x-ray imaging of the breast To understand the approaches and applications of spectral mammography To understand the potential advantages of distributed x-ray source arrays for digital breast tomosynthesis To understand the ongoing developments in detector technology for digital mammography and breast tomosynthesis To understand the current state-of-the-art for dedicated cone-beam breast CT and research to advance the technology. Research collaboration with Koning Corporation.

TU-EF-207-04: Advances in Detector Technology for Breast Tomosynthesis

International Nuclear Information System (INIS)

Zhao, W.

2015-01-01

mode due to lower photon fluence per projection. This may require fast-frame acquisition and symmetric or asymmetric pixel binning in some systems. Recent studies investigated the performance of increased conversion layer thickness for contrast-enhanced imaging of the breast in dual-energy acquisition mode. In other direct conversion detectors operating in the avalanche mode, sensitivities close to the single photon response are also explored for mammography and breast tomosynthesis. The potential advantages and challenges of this approach are described. Dedicated breast CT brings x-ray imaging of the breast to true tomographic 3D imaging. It can eliminate the tissue superposition problem and does not require physical compression of the breast. Using cone beam geometry and a flat-panel detector, several hundred projections are acquired and reconstructed to near isotropic voxels. Multiplanar reconstruction facilitates viewing the breast volume in any desired orientation. Ongoing clinical studies, the current state-of-the art, and research to advance the technology are described. Learning Objectives: To understand the ongoing developments in x-ray imaging of the breast To understand the approaches and applications of spectral mammography To understand the potential advantages of distributed x-ray source arrays for digital breast tomosynthesis To understand the ongoing developments in detector technology for digital mammography and breast tomosynthesis To understand the current state-of-the-art for dedicated cone-beam breast CT and research to advance the technology. Research collaboration with Koning Corporation

Radiation detector system having heat pipe based cooling

Science.gov (United States)

Iwanczyk, Jan S.; Saveliev, Valeri D.; Barkan, Shaul

2006-10-31

A radiation detector system having a heat pipe based cooling. The radiation detector system includes a radiation detector thermally coupled to a thermo electric cooler (TEC). The TEC cools down the radiation detector, whereby heat is generated by the TEC. A heat removal device dissipates the heat generated by the TEC to surrounding environment. A heat pipe has a first end thermally coupled to the TEC to receive the heat generated by the TEC, and a second end thermally coupled to the heat removal device. The heat pipe transfers the heat generated by the TEC from the first end to the second end to be removed by the heat removal device.

Four channel Cosmic Ray detector based on polymaq

Science.gov (United States)

Herrera-Guzman, K. N.; Gutierrez-Sanchez, R. A.; Felix, J.

2017-01-01

The Cherenkov radiation has been widely studied in transparent materials, and applied to detect and identify elementary particles. But it has not been widely studied in opaque materials. A four channels radiation detector has been designed, built, characterized, and operated; based on four polymaq (UHMW-PE) bars of 2.54 cm X 5.08 cm X 25.4 cm, which is an opaque material to visible radiation to the human eye. Silicon photo detectors, Hamamatsu, avalanche type (APD) are used to detect the radiation produced by the passage of particles in the detector blocks. The design, construction, characterization, operation, and preliminary results of this cosmic ray detector details are presented.

Panel Analysis

DEFF Research Database (Denmark)

Brænder, Morten; Andersen, Lotte Bøgh

2014-01-01

Based on our 2013-article, ”Does Deployment to War Affect Soldiers' Public Service Motivation – A Panel Study of Soldiers Before and After their Service in Afghanistan”, we present Panel Analysis as a methodological discipline. Panels consist of multiple units of analysis, observed at two or more...... in research settings where it is not possible to distribute units of analysis randomly or where the independent variables cannot be manipulated. The greatest disadvantage in regard to using panel studies is that data may be difficult to obtain. This is most clearly vivid in regard to the use of panel surveys...... points in time. In comparison with traditional cross-sectional studies, the advantage of using panel studies is that the time dimension enables us to study effects. Whereas experimental designs may have a clear advantage in regard to causal inference, the strength of panel studies is difficult to match...

Cones for dental radiography

Energy Technology Data Exchange (ETDEWEB)

Butler, M J [National Radiological Protection Board, Harwell (UK)

1977-04-01

Dental radiographic techniques are summarized. The advantages and disadvantages of the use of both the conventional plastic pointer cone and the open-ended cylinders or divergent cones favoured both by the ICRP (Protection against Ionizing Radiation from External Sources, Oxford, Pergamon Press, 1973, ICRP Publication 15), and in the Code of Practice for the Protection of Persons against Ionizing Radiation arising from Medical and Dental Use (1972, 3rd edition, London, HMSO) are discussed. The use of the word 'should' in these recommendations to signify a desirable requirement, not an essential one, is noted. This wording is currently of interest both nationally and internationally in relation to regulations, standards and notes for guidance. The National Radiological Protection Board (NRPB) has been reviewing the position, and has concluded that open-ended cones have disadvantages which may sometimes outweigh their advantages. Although open-ended cones are preferable under some circumstances, the recommendation that they should be used ought not to be followed without an understanding of the issues involved. The hazards associated with the use of interchangeable cones are considered. The NRPB now proposes that the requirement for the replacement of pointer cones (for both new and existing equipment) should be withdrawn.

Design of FPGA-based radiation tolerant quench detectors for LHC

Science.gov (United States)

Steckert, J.; Skoczen, A.

2017-04-01

The Large Hadron Collider (LHC) comprises many superconducting circuits. Most elements of these circuits require active protection. The functionality of the quench detectors was initially implemented as microcontroller based equipment. After the initial stage of the LHC operation with beams the introduction of a new type of quench detector began. This article presents briefly the main ideas and architectures applied to the design and the validation of FPGA-based quench detectors.

Design of FPGA-based radiation tolerant quench detectors for LHC

International Nuclear Information System (INIS)

Steckert, J.; Skoczen, A.

2017-01-01

The Large Hadron Collider (LHC) comprises many superconducting circuits. Most elements of these circuits require active protection. The functionality of the quench detectors was initially implemented as microcontroller based equipment. After the initial stage of the LHC operation with beams the introduction of a new type of quench detector began. This article presents briefly the main ideas and architectures applied to the design and the validation of FPGA-based quench detectors.

Understanding the cone scale in Cupressaceae: insights from seed-cone teratology in Glyptostrobus pensilis

Directory of Open Access Journals (Sweden)

Veit Martin Dörken

2018-06-01

Full Text Available Both wild-type and teratological seed cones are described in the monoecious conifer Glyptostrobus pensilis and compared with those of other Cupressaceae sensu lato and other conifers. Some Cupressaceae apparently possess a proliferation of axillary structures in their cone scales. In our interpretation, in Glyptostrobus each bract of both typical and atypical seed cones bears two descending accessory shoots, interpreted here as seed scales (ovuliferous scales. The primary seed scale is fertile and forms the ovules, the second is sterile and forms characteristic tooth-like structures. The bract and the two axillary seed scales are each supplied with a single distinct vascular bundle that enters the cone axis as a separate strand; this vasculature also characterises the descending accessory short shoots in the vegetative parts of the crown. In wild-type seed cones, the fertile seed scale is reduced to its ovules, and the ovules are always axillary. In contrast, the ovules of some of the teratological seed cones examined were located at the centre of the cone scale. An additional tissue found on the upper surface of the sterile lower seed scale is here interpreted as the axis of the fertile seed scale. Thus, the central position of the ovules can be explained by recaulescent fusion of the upper fertile and lower sterile seed scales. In several teratological cone scales, the ovules were enveloped by an additional sterile tissue that is uniseriate and represents an epidermal outgrowth of the fertile seed scale. Close to the ovules, the epidermis was detached from lower tissue and surrounded the ovule completely, except at the micropyle. These teratological features are potentially significant in understanding seed-cone homologies among extant conifers.

Occulting Light Concentrators in Liquid Scintillator Neutrino Detectors

Science.gov (United States)

Buizza Avanzini, Margherita; Cabrera, Anatael; Dusini, Stefano; Grassi, Marco; He, Miao; Wu, Wenjie

2017-09-01

The experimental efforts characterizing the era of precision neutrino physics revolve around collecting high-statistics neutrino samples and attaining an excellent energy and position resolution. Next generation liquid-based neutrino detectors, such as JUNO, HyperKamiokande, etc, share the use of a large target mass, and the need of pushing light collection to the edge for maximal calorimetric information. Achieving high light collection implies considerable costs, especially when considering detector masses of several kt. A traditional strategy to maximize the effective photo-coverage with the minimum number of PMTs relies on Light Concentrators (LC), such as Winston Cones. In this paper, the authors introduce a novel concept called Occulting Light Concentrators (OLC), whereby a traditional LC gets tailored to a conventional PMT, by taking into account its single-photoelectron collection efficiency profile and thus occulting the worst performing portion of the photocathode. Thus, the OLC shape optimization takes into account not only the optical interface of the PMT, but also the maximization of the PMT detection performances. The light collection uniformity across the detector is another advantage of the OLC system. By considering the case of JUNO, we will show OLC capabilities in terms of light collection and energy resolution.

CSBB-ConeExclusion, adapting structure based solution virtual screening to libraries on solid support.

Science.gov (United States)

Shave, Steven; Auer, Manfred

2013-12-23

Combinatorial chemical libraries produced on solid support offer fast and cost-effective access to a large number of unique compounds. If such libraries are screened directly on-bead, the speed at which chemical space can be explored by chemists is much greater than that addressable using solution based synthesis and screening methods. Solution based screening has a large supporting body of software such as structure-based virtual screening tools which enable the prediction of protein-ligand complexes. Use of these techniques to predict the protein bound complexes of compounds synthesized on solid support neglects to take into account the conjugation site on the small molecule ligand. This may invalidate predicted binding modes, the linker may be clashing with protein atoms. We present CSBB-ConeExclusion, a methodology and computer program which provides a measure of the applicability of solution dockings to solid support. Output is given in the form of statistics for each docking pose, a unique 2D visualization method which can be used to determine applicability at a glance, and automatically generated PyMol scripts allowing visualization of protein atom incursion into a defined exclusion volume. CSBB-ConeExclusion is then exemplarically used to determine the optimum attachment point for a purine library targeting cyclin-dependent kinase 2 CDK2.

THE ATLAS INNER DETECTOR TRACK BASED ALIGNMENT

CERN Document Server

Marti i Garcia, Salvador; The ATLAS collaboration

2018-01-01

The alignment of the ATLAS Inner Detector is performed with a track-based alignment algorithm. Its goal is to provide an accurate description of the detector geometry such that track parameters are accurately determined and free from biases. Its software implementation is modular and configurable, with a clear separation of the alignment algorithm from the detector system specifics and the database handling. The alignment must cope with the rapid movements of the detector as well as with the slow drift of the different mechanical units. Prompt alignment constants are derived for every run at the calibration stage. These sets of constants are then dynamically split from the beginning of the run in many chunks, allowing to describe the tracker geometry as it evolves with time. The alignment of the Inner Detector is validated and improved by studying resonance decays (Z and J/psi to mu+mu-), as well as using information from the calorimeter system with the E/p method with electrons. A detailed study of these res...

Light-cone quantization of quantum chromodynamics

International Nuclear Information System (INIS)

Brodsky, S.J.; Pauli, H.C.

1991-06-01

We discuss the light-cone quantization of gauge theories from two perspectives: as a calculational tool for representing hadrons as QCD bound-states of relativistic quarks and gluons, and also as a novel method for simulating quantum field theory on a computer. The light-cone Fock state expansion of wavefunctions at fixed light cone time provides a precise definition of the parton model and a general calculus for hadronic matrix elements. We present several new applications of light-cone Fock methods, including calculations of exclusive weak decays of heavy hadrons, and intrinsic heavy-quark contributions to structure functions. A general nonperturbative method for numerically solving quantum field theories, ''discretized light-cone quantization,'' is outlined and applied to several gauge theories, including QCD in one space and one time dimension, and quantum electrodynamics in physical space-time at large coupling strength. The DLCQ method is invariant under the large class of light-cone Lorentz transformations, and it can be formulated such at ultraviolet regularization is independent of the momentum space discretization. Both the bound-state spectrum and the corresponding relativistic light-cone wavefunctions can be obtained by matrix diagonalization and related techniques. We also discuss the construction of the light-cone Fock basis, the structure of the light-cone vacuum, and outline the renormalization techniques required for solving gauge theories within the light-cone Hamiltonian formalism

Light-cone quantization of quantum chromodynamics

Energy Technology Data Exchange (ETDEWEB)

Brodsky, S.J. (Stanford Linear Accelerator Center, Menlo Park, CA (USA)); Pauli, H.C. (Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany, F.R.))

1991-06-01

We discuss the light-cone quantization of gauge theories from two perspectives: as a calculational tool for representing hadrons as QCD bound-states of relativistic quarks and gluons, and also as a novel method for simulating quantum field theory on a computer. The light-cone Fock state expansion of wavefunctions at fixed light cone time provides a precise definition of the parton model and a general calculus for hadronic matrix elements. We present several new applications of light-cone Fock methods, including calculations of exclusive weak decays of heavy hadrons, and intrinsic heavy-quark contributions to structure functions. A general nonperturbative method for numerically solving quantum field theories, discretized light-cone quantization,'' is outlined and applied to several gauge theories, including QCD in one space and one time dimension, and quantum electrodynamics in physical space-time at large coupling strength. The DLCQ method is invariant under the large class of light-cone Lorentz transformations, and it can be formulated such at ultraviolet regularization is independent of the momentum space discretization. Both the bound-state spectrum and the corresponding relativistic light-cone wavefunctions can be obtained by matrix diagonalization and related techniques. We also discuss the construction of the light-cone Fock basis, the structure of the light-cone vacuum, and outline the renormalization techniques required for solving gauge theories within the light-cone Hamiltonian formalism.

Cadmium Removal from Aqueous Solutions by Ground Pine Cone

Directory of Open Access Journals (Sweden)

H Izanloo, S Nasseri

2005-01-01

Full Text Available A study on the removal of cadmium ions from aqueous solutions by pine cone was conducted in batch conditions. Kinetic data and equilibrium removal isotherms were obtained. The influence of different experimental parameters such as contact time, initial concentration of cadmium, pine cone mass and particle size, and temperature on the kinetics of cadmium removal was studied. Results showed that the main parameters that played an important role in removal phenomenon were initial cadmium concentration, particle size and pine cone mass. The necessary time to reach equilibrium was between 4 and 7 hours based on the initial concentration of cadmium. The capacity of cadmium adsorption at equilibrium increased with the decrease of pine cone particle size. The capacity of cadmium adsorption at equilibrium by pine cone increased with the quantity of pine cone introduced (1–4 g/L. Temperature in the range of 20-30°C showed a restricted effect on the removal kinetics (13.56 mg/g at 20°C and a low capacity of adsorption about 11.48 mg/g at 30°C. The process followed pseudo second-order kinetics. The cadmium uptake of pine cone was quantitatively evaluated using adsorption isotherms. Results indicated that the Langmuir model gave a better fit to the experimental data in comparison with the Freundlich equation.

The Global Muon Detector Network -GMDN and the space situational awareness

Science.gov (United States)

Schuch, Nelson Jorge; Munakata, Kazuoki; Dal Lago, Alisson; Marcos Denardini, Clezio; Echer, Ezequiel; Demítrio Gonzalez Alarcon, Walter; da Silva, Marlos; Rigozo, Nivaor R.; Petry, Adriano; Kirsch Pinheiro, Damaris; Braga, Carlos Roberto; Vinicius Dias Silveira, Marcos; Ronan Coelho Stekel, Tardelli; Espindola Antunes, Cassio; Ramos Vieira, Lucas; Kemmerich, Níkolas; Kato, Chihiro; Fushishita, Akira; Fujii, Zenjirou; Bieber, John W.; Evenson, Paul; Kuwabara, Takao; Duldig, Marcus L.; Humble, John E.; Chilingarian, Ashot; Sabbah, Ismail; Jansen, Frank

Space weather forecasting is a very important tool for the space situational awareness to the space objects, the space environment and related threats and risks for manned and non-manned spacecrafts. The global network of ground based multi-directional detectors (GMDN) can be considered as one example of an important emerging Space Situational Awareness program around the world, since its requirements needs global technical, scientific and logistic collab-oration between several countries in different continents. ICMEs accompanied by a strong shock often forms a high-energy galactic cosmic rays (GCRs) depleted region behind the shock known as a Forbush decrease. The ICME arrival also causes a systematic variation in the GCR streaming (i.e. the directional anisotropy of intensity). The magnitude of the streaming is small (about 1 % or less), but its variation is relevant. Some particles from this suppressed density region traveling with about the speed of light leak into the upstream region, much faster than the approaching shock, creating the possibility of being observed at the earth, by a global net-work of ground based multi-directional detectors (GMDN), as precursory loss-cone anisotropy. Loss-cones are typically visible 4-8 hours ahead of shock arrival for shocks associated with ma-jor geomagnetic storms. A multi-directional muon detector for detection of GCR was installed in 2001, through an international cooperation between Brazil, Japan and USA, and has been in operation since then at the Southern Space Observatory -SSO/CRS/INPE -MCT, (29.4° S, 53.8° W, 480m a.s.l), Sao Martinho da Serra, RS, in southern Brazil. The detector's capability and sensitivity were upgraded in 2005. The observations conducted by this detector are used for forecasting the arrival of the geomagnetic storm and their interplanetary coronal mass ejec-tion (ICME) drivers in the near-earth geospace. The detector measures high-energy GCRs by detecting secondary muons produced from the

Determining the Interstellar Wind Longitudinal Inflow Evolution Using Pickup Ions in the Helium Focusing Cone

Science.gov (United States)

Spitzer, S. A.; Gilbert, J. A.; Lepri, S. T.

2017-12-01

We propose to determine the longitudinal inflow direction of the local interstellar medium through the Heliosphere. This longitudinal inflow direction directly correlates to the longitudinal direction of the helium focusing cone with respect to the Sun. We can calculate this direction by finding the He+ pickup ion density peak as mass spectrometers such as ACE/SWICS, Wind/STICS, and Helios/Micrometeoroid Detector and Analyzer pass through the focusing cone. Mapping from the location of this density peak to the Sun, around which the helium is focused, will directly yield the desired longitudinal direction. We will find this direction for each year since the first measurements in the 1970s through the present and thereby analyze its evolution over time. This poster outlines our proposed method and initial results.

An Analysis of Delay-based and Integrator-based Sequence Detectors for Grid-Connected Converters

DEFF Research Database (Denmark)

Khazraj, Hesam; Silva, Filipe Miguel Faria da; Bak, Claus Leth

2017-01-01

-signal cancellation operators are the main members of the delay-based sequence detectors. The aim of this paper is to provide a theoretical and experimental comparative study between integrator and delay based sequence detectors. The theoretical analysis is conducted based on the small-signal modelling......Detecting and separating positive and negative sequence components of the grid voltage or current is of vital importance in the control of grid-connected power converters, HVDC systems, etc. To this end, several techniques have been proposed in recent years. These techniques can be broadly...... classified into two main classes: The integrator-based techniques and Delay-based techniques. The complex-coefficient filter-based technique, dual second-order generalized integrator-based method, multiple reference frame approach are the main members of the integrator-based sequence detector and the delay...

Evaluation of LSF based SOFC Cathodes using Cone-shaped Electrodes

DEFF Research Database (Denmark)

Kammer Hansen, Kent; Mogensen, Mogens Bjerg

2008-01-01

Seven La1-xSrxFeO3-delta (x = 0, 0.05, 0.15, 0.25, 0.35, 0.50, 0.70) based perovskites were synthesized using the glycine-nitrate method. The La1-xSrxFeO3-delta compounds were characterized with powder X-ray diffraction and electrochemical impedance spectroscopy on cone-shaped electrodes using a Ce......(III) is the catalytic active specie towards the electrochemical reduction of oxygen in a solid oxide fuel cell on La1-xSrxFeO3-delta compounds. The results also show that oxide ion vacancies in the perovskite structure are important for the electrochemical reduction of oxygen. However, the effect of ordering of oxide...

Development of a neutron imager based on superconducting detectors

Energy Technology Data Exchange (ETDEWEB)

Miyajima, Shigeyuki, E-mail: miyajima@nict.go.jp [Department of Physics and Engineering, Osaka Prefecture University (Japan); Institute for Nanofabrication Research, Osaka Prefecture University (Japan); Yamaguchi, Hiroyuki; Nakayama, Hirotaka; Shishido, Hiroaki [Department of Physics and Engineering, Osaka Prefecture University (Japan); Institute for Nanofabrication Research, Osaka Prefecture University (Japan); Fujimaki, Akira [Department of Quantum Engineering, Nagoya University (Japan); Hidaka, Mutsuo [National Institute of Advanced Industrial Science and Technology (Japan); Harada, Masahide; Oikawa, Kenichi; Oku, Takayuki; Arai, Masatoshi [J-PARC Center, Japan Atomic Energy Agency (Japan); Ishida, Takekazu [Department of Physics and Engineering, Osaka Prefecture University (Japan); Institute for Nanofabrication Research, Osaka Prefecture University (Japan)

2016-11-15

Highlights: • A neutron detector based on superconducting meander line is demonstrated. • Fast response time of a few tens ns is obtained. • Spatial resolution is 1 μm and can be improved to sub-μm scale. • The proposed neutron detector can operate under the γ-ray fields. - Abstract: We succeeded in demonstrating a neutron detector based on a Nb superconducting meander line with a {sup 10}B conversion layer for a neutron imager based on superconductor devices. We use a current-biased kinetic inductance detector (CB-KID), which is composed of a meander line, for detection of a neutron with high spatial resolution and fast response time. The thickness of Nb meander lines is 40 nm and the line width is narrower than 3 mu m. The area of 8 mm × 8 mm is covered by CB-KIDs, which are assembled at the center of the Si chip of the size 22 mm × 22 mm. The Nb CB-KIDs with a {sup 10}B conversion layer output the voltage by irradiating pulsed neutrons. We have investigated γ/n discrimination of a Nb-based CB-KID with {sup 10}B conversion layer using a Cd plate, which indicates that a CB-KID can operate as a neutron detector under the strong γ-ray fields.

Development of a neutron imager based on superconducting detectors

International Nuclear Information System (INIS)

Miyajima, Shigeyuki; Yamaguchi, Hiroyuki; Nakayama, Hirotaka; Shishido, Hiroaki; Fujimaki, Akira; Hidaka, Mutsuo; Harada, Masahide; Oikawa, Kenichi; Oku, Takayuki; Arai, Masatoshi; Ishida, Takekazu

2016-01-01

Highlights: • A neutron detector based on superconducting meander line is demonstrated. • Fast response time of a few tens ns is obtained. • Spatial resolution is 1 μm and can be improved to sub-μm scale. • The proposed neutron detector can operate under the γ-ray fields. - Abstract: We succeeded in demonstrating a neutron detector based on a Nb superconducting meander line with a "1"0B conversion layer for a neutron imager based on superconductor devices. We use a current-biased kinetic inductance detector (CB-KID), which is composed of a meander line, for detection of a neutron with high spatial resolution and fast response time. The thickness of Nb meander lines is 40 nm and the line width is narrower than 3 mu m. The area of 8 mm × 8 mm is covered by CB-KIDs, which are assembled at the center of the Si chip of the size 22 mm × 22 mm. The Nb CB-KIDs with a "1"0B conversion layer output the voltage by irradiating pulsed neutrons. We have investigated γ/n discrimination of a Nb-based CB-KID with "1"0B conversion layer using a Cd plate, which indicates that a CB-KID can operate as a neutron detector under the strong γ-ray fields.

Development of a fast multi-line x-ray CT detector for NDT

International Nuclear Information System (INIS)

Hofmann, T.; Nachtrab, F.; Schlechter, T.; Mühlbauer, J.; Schröpfer, S.; Firsching, M.; Uhlmann, N.; Neubauer, H.; Ernst, J.; Schweiger, T.; Oberst, M.; Meyer, A.

2015-01-01

Typical X-ray detectors for non-destructive testing (NDT) are line detectors or area detectors, like e.g. flat panel detectors. Multi-line detectors are currently only available in medical Computed Tomography (CT) scanners. Compared to flat panel detectors, line and multi-line detectors can achieve much higher frame rates. This allows time-resolved 3D CT scans of an object under investigation. Also, an improved image quality can be achieved due to reduced scattered radiation from object and detector themselves. Another benefit of line and multi-line detectors is that very wide detectors can be assembled easily, while flat panel detectors are usually limited to an imaging field with a size of approx. 40 × 40 cm 2 at maximum. The big disadvantage of line detectors is the limited number of object slices that can be scanned simultaneously. This leads to long scan times for large objects. Volume scans with a multi-line detector are much faster, but with almost similar image quality. Due to the promising properties of multi-line detectors their application outside of medical CT would also be very interesting for NDT. However, medical CT multi-line detectors are optimized for the scanning of human bodies. Many non-medical applications require higher spatial resolutions and/or higher X-ray energies. For those non-medical applications we are developing a fast multi-line X-ray detector.In the scope of this work, we present the current state of the development of the novel detector, which includes several outstanding properties like an adjustable curved design for variable focus-detector-distances, conserving nearly uniform perpendicular irradiation over the entire detector width. Basis of the detector is a specifically designed, radiation hard CMOS imaging sensor with a pixel pitch of 200 μ m. Each pixel has an automatic in-pixel gain adjustment, which allows for both: a very high sensitivity and a wide dynamic range. The final detector is planned to have 256 lines of

Cone-beam and fan-beam image reconstruction algorithms based on spherical and circular harmonics

International Nuclear Information System (INIS)

Zeng, Gengsheng L; Gullberg, Grant T

2004-01-01

A cone-beam image reconstruction algorithm using spherical harmonic expansions is proposed. The reconstruction algorithm is in the form of a summation of inner products of two discrete arrays of spherical harmonic expansion coefficients at each cone-beam point of acquisition. This form is different from the common filtered backprojection algorithm and the direct Fourier reconstruction algorithm. There is no re-sampling of the data, and spherical harmonic expansions are used instead of Fourier expansions. As a special case, a new fan-beam image reconstruction algorithm is also derived in terms of a circular harmonic expansion. Computer simulation results for both cone-beam and fan-beam algorithms are presented for circular planar orbit acquisitions. The algorithms give accurate reconstructions; however, the implementation of the cone-beam reconstruction algorithm is computationally intensive. A relatively efficient algorithm is proposed for reconstructing the central slice of the image when a circular scanning orbit is used

Performance of low-cost X-ray area detectors with consumer digital cameras

International Nuclear Information System (INIS)

Panna, A.; Gomella, A.A.; Harmon, K.J.; Chen, P.; Miao, H.; Bennett, E.E.; Wen, H.

2015-01-01

We constructed X-ray detectors using consumer-grade digital cameras coupled to commercial X-ray phosphors. Several detector configurations were tested against the Varian PaxScan 3024M (Varian 3024M) digital flat panel detector. These include consumer cameras (Nikon D800, Nikon D700, and Nikon D3X) coupled to a green emission phosphor in a back-lit, normal incidence geometry, and in a front-lit, oblique incidence geometry. We used the photon transfer method to evaluate detector sensitivity and dark noise, and the edge test method to evaluate their spatial resolution. The essential specifications provided by our evaluation include discrete charge events captured per mm 2 per unit exposure surface dose, dark noise in equivalents of charge events per pixel, and spatial resolution in terms of the full width at half maximum (FWHM) of the detector's line spread function (LSF). Measurements were performed using a tungsten anode X-ray tube at 50 kVp. The results show that the home-built detectors provide better sensitivity and lower noise than the commercial flat panel detector, and some have better spatial resolution. The trade-off is substantially smaller imaging areas. Given their much lower costs, these home-built detectors are attractive options for prototype development of low-dose imaging applications

SPECT detector system design based on embedded system

International Nuclear Information System (INIS)

Zhang Weizheng; Zhao Shujun; Zhang Lei; Sun Yuanling

2007-01-01

A single-photon emission computed tomography detector system based on embedded Linux designed. This system is composed of detector module, data acquisition module, ARM MPU module, network interface communication module and human machine interface module. Its software uses multithreading technology based on embedded Linux. It can achieve high speed data acquisition, real-time data correction and network data communication. It can accelerate the data acquisition and decrease the dead time. The accuracy and the stability of the system can be improved. (authors)

Light-cone sum rules: A SCET-based formulation

CERN Document Server

De Fazio, F; Hurth, Tobias; Feldmann, Th.

2007-01-01

We describe the construction of light-cone sum rules (LCSRs) for exclusive $B$-meson decays into light energetic hadrons from correlation functions within soft-collinear effective theory (SCET). As an example, we consider the SCET sum rule for the $B \\to \\pi$ transition form factor at large recoil, including radiative corrections from hard-collinear loop diagrams at first order in the strong coupling constant.

Development of a full ice-cream cone model for halo CME structures

Science.gov (United States)

Na, Hyeonock; Moon, Yong-Jae

2015-04-01

The determination of three dimensional parameters (e.g., radial speed, angular width, source location) of Coronal Mass Ejections (CMEs) is very important for space weather forecast. To estimate these parameters, several cone models based on a flat cone or a shallow ice-cream cone with spherical front have been suggested. In this study, we investigate which cone model is proper for halo CME morphology using 33 CMEs which are identified as halo CMEs by one spacecraft (SOHO or STEREO-A or B) and as limb CMEs by the other ones. From geometrical parameters of these CMEs such as their front curvature, we find that near full ice-cream cone CMEs (28 events) are dominant over shallow ice-cream cone CMEs (5 events). So we develop a new full ice-cream cone model by assuming that a full ice-cream cone consists of many flat cones with different heights and angular widths. This model is carried out by the following steps: (1) construct a cone for given height and angular width, (2) project the cone onto the sky plane, (3) select points comprising the outer boundary, (4) minimize the difference between the estimated projection points with the observed ones. We apply this model to several halo CMEs and compare the results with those from other methods such as a Graduated Cylindrical Shell model and a geometrical triangulation method.

Eruptive and Geomorphic Processes at the Lathrop Wells Scoria Cone

International Nuclear Information System (INIS)

G. Valentine; D.J. Krier; F.V. Perry; G. Heiken

2006-01-01

The ∼80 ka Lathrop Wells volcano (southern Nevada, U.S.A.) preserves evidence for a range of explosive processes and emplacement mechanisms of pyroclastic deposits and lava fields in a small-volume basaltic center. Early cone building by Strombolian bursts was accompanied by development of a fan-like lava field reaching ∼800 m distance from the cone, built upon a gently sloping surface. Lava flows carried rafts of cone deposits, which provide indirect evidence for cone facies in lieu of direct exposures in the active quarry. Subsequent activity was of a violent Strombolian nature, with many episodes of sustained eruption columns up to a few km in height. These deposited layers of scoria lapilli and ash in different directions depending upon wind direction at the time of a given episode, reaching up to ∼20 km from the vent, and also produced the bulk of the scoria cone. Lava effusion migrated from south to north around the eastern base of the cone as accumulation of lavas successively reversed the topography at the base of the cone. Late lavas were emplaced during violent Strombolian activity and continued for some time after explosive eruptions had waned. Volumes of the eruptive products are: fallout--0.07 km 3 , scoria cone--0.02 km 3 , and lavas--0.03 km 3 . Shallow-derived xenolith concentrations suggest an upper bound on average conduit diameter of ∼21 m in the uppermost 335 m beneath the volcano. The volcano was constructed over a period of at least seven months with cone building occurring only during part of that time, based upon analogy with historical eruptions. Post-eruptive geomorphic evolution varied for the three main surface types that were produced by volcanic activity: (1) scoria cone, (2) low relief surfaces (including lavas) with abundant pyroclastic material, and (3) lavas with little pyroclastic material. The role of these different initial textures must be accounted for in estimating relative ages of volcanic surfaces, and failure to

Eruptive and Geomorphic Processes at the Lathrop Wells Scoria Cone

Energy Technology Data Exchange (ETDEWEB)

G. Valentine; D.J. Krier; F.V. Perry; G. Heiken

2006-08-03

The {approx}80 ka Lathrop Wells volcano (southern Nevada, U.S.A.) preserves evidence for a range of explosive processes and emplacement mechanisms of pyroclastic deposits and lava fields in a small-volume basaltic center. Early cone building by Strombolian bursts was accompanied by development of a fan-like lava field reaching {approx}800 m distance from the cone, built upon a gently sloping surface. Lava flows carried rafts of cone deposits, which provide indirect evidence for cone facies in lieu of direct exposures in the active quarry. Subsequent activity was of a violent Strombolian nature, with many episodes of sustained eruption columns up to a few km in height. These deposited layers of scoria lapilli and ash in different directions depending upon wind direction at the time of a given episode, reaching up to {approx}20 km from the vent, and also produced the bulk of the scoria cone. Lava effusion migrated from south to north around the eastern base of the cone as accumulation of lavas successively reversed the topography at the base of the cone. Late lavas were emplaced during violent Strombolian activity and continued for some time after explosive eruptions had waned. Volumes of the eruptive products are: fallout--0.07 km{sup 3}, scoria cone--0.02 km{sup 3}, and lavas--0.03 km{sup 3}. Shallow-derived xenolith concentrations suggest an upper bound on average conduit diameter of {approx}21 m in the uppermost 335 m beneath the volcano. The volcano was constructed over a period of at least seven months with cone building occurring only during part of that time, based upon analogy with historical eruptions. Post-eruptive geomorphic evolution varied for the three main surface types that were produced by volcanic activity: (1) scoria cone, (2) low relief surfaces (including lavas) with abundant pyroclastic material, and (3) lavas with little pyroclastic material. The role of these different initial textures must be accounted for in estimating relative ages of

Dynamic flat panel detector versus image intensifier in cardiac imaging: dose and image quality

Science.gov (United States)

Vano, E.; Geiger, B.; Schreiner, A.; Back, C.; Beissel, J.

2005-12-01

The practical aspects of the dosimetric and imaging performance of a digital x-ray system for cardiology procedures were evaluated. The system was configured with an image intensifier (II) and later upgraded to a dynamic flat panel detector (FD). Entrance surface air kerma (ESAK) to phantoms of 16, 20, 24 and 28 cm of polymethyl methacrylate (PMMA) and the image quality of a test object were measured. Images were evaluated directly on the monitor and with numerical methods (noise and signal-to-noise ratio). Information contained in the DICOM header for dosimetry audit purposes was also tested. ESAK values per frame (or kerma rate) for the most commonly used cine and fluoroscopy modes for different PMMA thicknesses and for field sizes of 17 and 23 cm for II, and 20 and 25 cm for FD, produced similar results in the evaluated system with both technologies, ranging between 19 and 589 µGy/frame (cine) and 5 and 95 mGy min-1 (fluoroscopy). Image quality for these dose settings was better for the FD version. The 'study dosimetric report' is comprehensive, and its numerical content is sufficiently accurate. There is potential in the future to set those systems with dynamic FD to lower doses than are possible in the current II versions, especially for digital cine runs, or to benefit from improved image quality.

A highly accurate wireless digital sun sensor based on profile detecting and detector multiplexing technologies

Science.gov (United States)

Wei, Minsong; Xing, Fei; You, Zheng

2017-01-01

The advancing growth of micro- and nano-satellites requires miniaturized sun sensors which could be conveniently applied in the attitude determination subsystem. In this work, a profile detecting technology based high accurate wireless digital sun sensor was proposed, which could transform a two-dimensional image into two-linear profile output so that it can realize a high update rate under a very low power consumption. A multiple spots recovery approach with an asymmetric mask pattern design principle was introduced to fit the multiplexing image detector method for accuracy improvement of the sun sensor within a large Field of View (FOV). A FOV determination principle based on the concept of FOV region was also proposed to facilitate both sub-FOV analysis and the whole FOV determination. A RF MCU, together with solar cells, was utilized to achieve the wireless and self-powered functionality. The prototype of the sun sensor is approximately 10 times lower in size and weight compared with the conventional digital sun sensor (DSS). Test results indicated that the accuracy of the prototype was 0.01° within a cone FOV of 100°. Such an autonomous DSS could be equipped flexibly on a micro- or nano-satellite, especially for highly accurate remote sensing applications.

Nontraumatic tibial polyethylene insert cone fracture in mobile-bearing posterior-stabilized total knee arthroplasty

Directory of Open Access Journals (Sweden)

Yohei Tanikake

2016-12-01

Full Text Available A 72-year-old male patient underwent mobile-bearing posterior-stabilized total knee arthroplasty for osteoarthritis. He experienced a nontraumatic polyethylene tibial insert cone fracture 27 months after surgery. Scanning electron microscopy of the fracture surface of the tibial insert cone suggested progress of ductile breaking from the posterior toward the anterior of the cone due to repeated longitudinal bending stress, leading to fatigue breaking at the anterior side of the cone, followed by the tibial insert cone fracture at the anterior side of the cone, resulting in fracture at the base of the cone. This analysis shows the risk of tibial insert cone fracture due to longitudinal stress in mobile-bearing posterior-stabilized total knee arthroplasty in which an insert is designed to highly conform to the femoral component.

Gamma flaw detectors for radiographic control of welded joint quality under mounting conditions

International Nuclear Information System (INIS)

Khoroshev, V.N.; Galash, T.F.; Andreev, V.L.; Grigor'ev, V.M.; Medvedev, N.E.

1978-01-01

Main characteristics are presented of gamma flaw detector models used for radiographic control of the quality of welded steel and pipeline joints during assembly. Specially developed experimental models, operating with 75 Se, 90 Sr, 170 Tm, 137 Cs and 192 Ir sources are considered. The new instruments have been made on a single structural base, which creates a foundation for standardizing individual units of radiation heads, manual control panels, containers, exterior packings, devices and accessories, maintenance techniques, and repair techniques. They are distinguished by small sizes and weight, possibility of using a set of radiation sources ensuring control of 3-40 mm thick joints, and reliable protection. Special devices permit to reduce 2-3-folds the time needed for installing and orienting the flaw detectors. The expected economic effect from implementation of the new gamma flaw detectors into industry will amount to 1.5-10.0 thousand roubles per annum for one detector at approximate cost of each detector equal to 3.5-6.0 thousand roubles

Characterizing X-ray detectors for prototype digital breast tomosynthesis systems

International Nuclear Information System (INIS)

Kim, Y.-S.; Park, H.-S.; Park, S.-J.; Choi, S.; Lee, H.; Kim, H.-J.; Lee, D.; Choi, Y.-W.

2016-01-01

The digital breast tomosynthesis (DBT) system is a newly developed 3-D imaging technique that overcomes the tissue superposition problems of conventional mammography. Therefore, it produces fewer false positives. In DBT system, several parameters are involved in image acquisition, including geometric components. A series of projections should be acquired at low exposure. This makes the system strongly dependent on the detector's characteristic performance. This study compares two types of x-ray detectors developed by the Korea Electrotechnology Research Institute (KERI). The first prototype DBT system has a CsI (Tl) scintillator/CMOS based flat panel digital detector (2923 MAM, Dexela Ltd.), with a pixel size of 0.0748 mm. The second uses a-Se based direct conversion full field detector (AXS 2430, analogic) with a pixel size of 0.085 mm. The geometry of both systems is same, with a focal spot 665.8 mm from the detector, and a center of rotation 33 mm above the detector surface. The systems were compared with regard to modulation transfer function (MTF), normalized noise power spectrum (NNPS), detective quantum efficiency (DQE) and a new metric, the relative object detectability (ROD). The ROD quantifies the relative performance of each detector at detecting specified objects. The system response function demonstrated excellent linearity (R 2 >0.99). The CMOS-based detector had a high sensitivity, while the Anrad detector had a large dynamic range. The higher MTF and noise power spectrum (NPS) values were measured using an Anrad detector. The maximum DQE value of the Dexela detector was higher than that of the Anrad detector with a low exposure level, considering one projection exposure for tomosynthesis. Overall, the Dexela detector performed better than did the Anrad detector with regard to the simulated Al wires, spheres, test objects of ROD with low exposure level. In this study, we compared the newly developed prototype DBT system with two different types

Cone photoreceptor structure in patients with x-linked cone dysfunction and red-green color vision deficiency

DEFF Research Database (Denmark)

Patterson, Emily J.; Wilk, Melissa; Langlo, Christopher S.

2016-01-01

encoded by exon 4, and two with a novel insertion in exon 2. Foveal cone structure and retinal thickness was disrupted to a variable degree, even among related individuals with the same L/M array. CONCLUSIONS. Our findings provide a direct link between disruption of the cone mosaic and L/ M opsin variants......PURPOSE. Mutations in the coding sequence of the L and M opsin genes are often associated with X-linked cone dysfunction (such as Bornholm Eye Disease, BED), though the exact color vision phenotype associated with these disorders is variable. We examined individuals with L/ M opsin gene mutations...... to clarify the link between color vision deficiency and cone dysfunction.  METHODS. We recruited 17 males for imaging. The thickness and integrity of the photoreceptor layers were evaluated using spectral-domain optical coherence tomography. Cone density was measured using high-resolution images of the cone...

The NLO jet vertex in the small-cone approximation for kt and cone algorithms

International Nuclear Information System (INIS)

Colferai, D.; Niccoli, A.

2015-01-01

We determine the jet vertex for Mueller-Navelet jets and forward jets in the small-cone approximation for two particular choices of jet algoritms: the kt algorithm and the cone algorithm. These choices are motivated by the extensive use of such algorithms in the phenomenology of jets. The differences with the original calculations of the small-cone jet vertex by Ivanov and Papa, which is found to be equivalent to a formerly algorithm proposed by Furman, are shown at both analytic and numerical level, and turn out to be sizeable. A detailed numerical study of the error introduced by the small-cone approximation is also presented, for various observables of phenomenological interest. For values of the jet “radius” R=0.5, the use of the small-cone approximation amounts to an error of about 5% at the level of cross section, while it reduces to less than 2% for ratios of distributions such as those involved in the measure of the azimuthal decorrelation of dijets.

The NLO jet vertex in the small-cone approximation for kt and cone algorithms

Energy Technology Data Exchange (ETDEWEB)

Colferai, D.; Niccoli, A. [Dipartimento di Fisica e Astronomia, Università di Firenze and INFN, Sezione di Firenze, 50019 Sesto Fiorentino (Italy)

2015-04-15

We determine the jet vertex for Mueller-Navelet jets and forward jets in the small-cone approximation for two particular choices of jet algoritms: the kt algorithm and the cone algorithm. These choices are motivated by the extensive use of such algorithms in the phenomenology of jets. The differences with the original calculations of the small-cone jet vertex by Ivanov and Papa, which is found to be equivalent to a formerly algorithm proposed by Furman, are shown at both analytic and numerical level, and turn out to be sizeable. A detailed numerical study of the error introduced by the small-cone approximation is also presented, for various observables of phenomenological interest. For values of the jet “radius” R=0.5, the use of the small-cone approximation amounts to an error of about 5% at the level of cross section, while it reduces to less than 2% for ratios of distributions such as those involved in the measure of the azimuthal decorrelation of dijets.

QCD on the light cone

International Nuclear Information System (INIS)

Brodsky, S.J.

1992-09-01

The quantization of gauge theory at fixed light-cone time τ = t - z/c provides new perspectives for solving non-perturbative problems in quantum chromodynamics. The light-cone Fock state expansion provides both a precise definition of the relativistic wavefunctions of hadrons as bound-states of quarks and gluons and a general calculus for predicting QCD processes at the amplitude level. Applications to exclusive processes and weak decay amplitudes are discussed. The problem of computing the hadronic spectrum and the corresponding light-cone wavefunctions of QCD in one space and one time dimension has been successfully reduced to the diagonalization of a discrete representation of the light-cone Hamiltonian. The problems confronting the solution of gauge theories in 3 + 1 dimensions in the light-cone quantization formalism,, including zero modes and non-perturbative renormalization, are reviewed

Determination of the Resistance of Cone-Shaped Solid Electrodes

DEFF Research Database (Denmark)

Frandsen, Henrik Lund; Hendriksen, Peter Vang; Koch, Søren

2017-01-01

during processing can be avoided. Newman's formula for current constriction in the electrolyte is then used to deduce the active contact area based on the ohmic resistance of the cell, and from this the surface specific electro-catalytic activity. However, for electrode materials with low electrical......A cone-shaped electrode pressed into an electrolyte can with advantage be utilized to characterize the electro-catalytic properties of the electrode, because it is less dependent on the electrode microstructure than e.g. thin porous composite electrodes, and reactions with the electrolyte occurring...... conductivity (like Ce1-xPrxO2-δ), the resistance of the cell is significantly influenced by the ohmic resistance of the cone electrode, wherefore it must be included. In this work the ohmic resistance of a cone is modelled analytically based on simplified geometries. The two analytical models only differ...

NMNAT1 variants cause cone and cone-rod dystrophy.

Science.gov (United States)

Nash, Benjamin M; Symes, Richard; Goel, Himanshu; Dinger, Marcel E; Bennetts, Bruce; Grigg, John R; Jamieson, Robyn V

2018-03-01

Cone and cone-rod dystrophies (CD and CRD, respectively) are degenerative retinal diseases that predominantly affect the cone photoreceptors. The underlying disease gene is not known in approximately 75% of autosomal recessive cases. Variants in NMNAT1 cause a severe, early-onset retinal dystrophy called Leber congenital amaurosis (LCA). We report two patients where clinical phenotyping indicated diagnoses of CD and CRD, respectively. NMNAT1 variants were identified, with Case 1 showing an extremely rare homozygous variant c.[271G > A] p.(Glu91Lys) and Case 2 compound heterozygous variants c.[53 A > G];[769G > A] p.(Asn18Ser);(Glu257Lys). The detailed variant analysis, in combination with the observation of an associated macular atrophy phenotype, indicated that these variants were disease-causing. This report demonstrates that the variants in NMNAT1 may cause CD or CRD associated with macular atrophy. Genetic investigations of the patients with CD or CRD should include NMNAT1 in the genes examined.

Scoria cones on Mars: detailed investigation of morphometry based on high - resolution Digital Elevation Models

Czech Academy of Sciences Publication Activity Database

Brož, Petr; Čadek, O.; Hauber, E.; Rossi, A. P.

2015-01-01

Roč. 120, č. 9 (2015), s. 1512-1527 ISSN 2169-9097 Institutional support: RVO:67985530 Keywords : Mars surface * volcanism * pyroclastic cone * scoria cone Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 3.440, year: 2013

Quality assessment and enhancement for cone-beam computed tomography in dental imaging

International Nuclear Information System (INIS)

Jeon, Sung Chae

2006-02-01

Cone-beam CT will become increasingly important in diagnostic imaging modality in the dental practice over the next decade. For dental diagnostic imaging, cone-beam computed tomography (CBCT) system based on large area flat panel imager has been designed and developed for three-dimensional volumetric image. The new CBCT system can provide a 3-D volumetric image during only one circular scanning with relatively short times (20-30 seconds) and requires less radiation dose than that of conventional CT. To reconstruct volumetric image from 2-D projection images, FDK algorithm was employed. The prototype of our CBCT system gives the promising results that can be efficiently diagnosed. This dissertation deals with assessment, enhancement, and optimization for dental cone-beam computed tomography with high performance. A new blur estimation method was proposed, namely model based estimation algorithm. Based on the empirical model of the PSF, an image restoration is applied to radiological images. The accuracy of the PSF estimation under Poisson noise and readout electronic noise is significantly better for the R-L estimator than the Wiener estimator. In the image restoration experiment, the result showed much better improvement in the low and middle range of spatial frequency. Our proposed algorithm is more simple and effective method to determine 2-D PSF of the x-ray imaging system than traditional methods. Image based scatter correction scheme to reduce the scatter effects was proposed. This algorithm corrects scatter on projection images based on convolution, scatter fraction, and angular interpolation. The scatter signal was estimated by convolving a projection image with scatter point spread function (SPSF) followed by multiplication with scatter fraction. Scatter fraction was estimated using collimator which is similar to SPECS method. This method does not require extra x-ray dose and any additional phantom. Maximum estimated error for interpolation was less than 7

Méthode analytique généralisée pour le calcul du coning. Nouvelle solution pour calculer le coning de gaz, d'eau et double coning dans les puits verticaux et horizontaux Generalized Analytical Method for Coning Calculation. New Solution to Calculation Both the Gas Coning, Water Coning and Dual Coning for Vertical and Horizontal Wells

Directory of Open Access Journals (Sweden)

Pietraru V.

2006-11-01

reservoirs [1]. This article gives a generalized description of this method for confined reservoirs. The case corresponding to a horizontal top is considered (bottom water drive and gas-cap drive. The generalization proposed is based on the solving of differential equations for diffusivity, while taking gravity drainage effects and boundary conditions into consideration for a confined reservoir. The method can be applied to isotropic or anisotropic reservoirs. The principal contributions of this article are :- Introduction of the concept of coning radius, differing from the well radius. The coning height and critical flow rate depend on the coning radius, whereas they are independent of the well radius. - A new correlation for calculating the critical flow rate in an adimensional from as a function of three parameters :. time,. length of the horizontal drain hole (zero for a vertical well, . and drainage radius. - Correlations for calculating the gas/oil ratios (GOR or the water fraction (fw during critical and postcritical periods, which take capillary pressure and relative permeabilities into consideration. - Correlations for calculating the gas/oil and water/oil ratios during the pre, post and supercritical periods of dual coning. - Criteria for calculating the breakthrough time at the well for simple gas or water coning, or for dual gas or water coning. The critical flow rate varies with time. It depends on the geometric and physical parameters of the reservoir, such as the thickness of the layer or the drainage area of the well, and on an important parameter, the coning radius, which will be defined hereunder. On the contrary, the critical flow rate does not depend on the parameters characterizing the well or the near-well vicinity, i. e. the radius and damage (skin.N.B. No confusion must be made between the critical flow rate due to coning and other flow rates associated with the way the well operates, such as the potential flow rate of the well defined by the

Psychophysical evaluation of the image quality of a dynamic flat-panel digital x-ray image detector using the threshold contrast detail detectability (TCDD) technique

Science.gov (United States)

Davies, Andrew G.; Cowen, Arnold R.; Bruijns, Tom J. C.

1999-05-01

We are currently in an era of active development of the digital X-ray imaging detectors that will serve the radiological communities in the new millennium. The rigorous comparative physical evaluations of such devices are therefore becoming increasingly important from both the technical and clinical perspectives. The authors have been actively involved in the evaluation of a clinical demonstration version of a flat-panel dynamic digital X-ray image detector (or FDXD). Results of objective physical evaluation of this device have been presented elsewhere at this conference. The imaging performance of FDXD under radiographic exposure conditions have been previously reported, and in this paper a psychophysical evaluation of the FDXD detector operating under continuous fluoroscopic conditions is presented. The evaluation technique employed was the threshold contrast detail detectability (TCDD) technique, which enables image quality to be measured on devices operating in the clinical environment. This approach addresses image quality in the context of both the image acquisition and display processes, and uses human observers to measure performance. The Leeds test objects TO[10] and TO[10+] were used to obtain comparative measurements of performance on the FDXD and two digital spot fluorography (DSF) systems, one utilizing a Plumbicon camera and the other a state of the art CCD camera. Measurements were taken at a range of detector entrance exposure rates, namely 6, 12, 25 and 50 (mu) R/s. In order to facilitate comparisons between the systems, all fluoroscopic image processing such as noise reduction algorithms, were disabled during the experiments. At the highest dose rate FDXD significantly outperformed the DSF comparison systems in the TCDD comparisons. At 25 and 12 (mu) R/s all three-systems performed in an equivalent manner and at the lowest exposure rate FDXD was inferior to the two DSF systems. At standard fluoroscopic exposures, FDXD performed in an equivalent

Performance of B-10 based detectors

Energy Technology Data Exchange (ETDEWEB)

Boucher, Mathieu; Anderson, Tom; Johnson, Nathan; Mckinny, Kevin; Mcpheeters, Matthew [GE Measurement and Control - Reuter-Stokes, Twinsburg, Ohio (United States)

2015-07-01

Helium-3 gas-filled detectors have been used in nuclear safeguards applications, in homeland security neutron detection modules and in research for over 30 years. With the current shortage of {sup 3}He gas, GE's Reuter-Stokes business developed a {sup 10}B lined proportional counter and a {sup 10}B hybrid detector, in which a small amount of {sup 3}He is added to a 10B detector to enhance the neutron sensitivity. In 2010, GE's Reuter-Stokes successfully developed a commercial alternative to 3He gas-filled detectors for homeland security neutron detection modules based on 10B lined proportional counters. We will present the concept behind the {sup 10}B neutron detection modules, as drop-in replacement to existing 3He neutron detection modules deployed, and the timeline and development needed to get a fully commercial application. To ensure the highest quality, each {sup 10}B neutron detection unit is put through a series of tests: temperature cycles from -40 deg. C to +55 deg. C, vibration testing at levels up to 2.5 g from 10 Hz to 50 Hz in every direction, neutron sensitivity reaching up to 4.5 cps/(ng {sup 252}CF at 2 m), and gamma insensitivity with field reaching 1 Sv/hr. In 2013, GE's Reuter-Stokes developed the B10Plus+{sup R} detector, in which a small amount of {sup 3}He is added to a {sup 10}B lined proportional counter. Depending on the amount of {sup 3}He added, the B10Plus+{sup R} can more than double the neutron sensitivity compared to a {sup 10}B lined proportional counter. {sup 10}B lined proportional counters and B10Plus+{sup R} have excellent gamma rejection and excellent performance even at very high neutron flux. The gamma rejection and high neutron flux performance of these detectors are comparable, if not better, than traditional {sup 3}He proportional counters. GE's Reuter-Stokes business modelled, designed, built and tested prototype coincidence counters using the {sup 10}B lined detectors and the {sup 10}B hybrid

Analysis of the effect of cone-beam geometry and test object configuration on the measurement accuracy of a computed tomography scanner used for dimensional measurement

International Nuclear Information System (INIS)

Kumar, Jagadeesha; Attridge, Alex; Williams, Mark A; Wood, P K C

2011-01-01

Industrial x-ray computed tomography (CT) scanners are used for non-contact dimensional measurement of small, fragile components and difficult-to-access internal features of castings and mouldings. However, the accuracy and repeatability of measurements are influenced by factors such as cone-beam system geometry, test object configuration, x-ray power, material and size of test object, detector characteristics and data analysis methods. An attempt is made in this work to understand the measurement errors of a CT scanner over the complete scan volume, taking into account only the errors in system geometry and the object configuration within the scanner. A cone-beam simulation model is developed with the radiographic image projection and reconstruction steps. A known amount of errors in geometrical parameters were introduced in the model to understand the effect of geometry of the cone-beam CT system on measurement accuracy for different positions, orientations and sizes of the test object. Simulation analysis shows that the geometrical parameters have a significant influence on the dimensional measurement at specific configurations of the test object. Finally, the importance of system alignment and estimation of correct parameters for accurate CT measurements is outlined based on the analysis

A reconstruction method for cone-beam differential x-ray phase-contrast computed tomography.

Science.gov (United States)

Fu, Jian; Velroyen, Astrid; Tan, Renbo; Zhang, Junwei; Chen, Liyuan; Tapfer, Arne; Bech, Martin; Pfeiffer, Franz

2012-09-10

Most existing differential phase-contrast computed tomography (DPC-CT) approaches are based on three kinds of scanning geometries, described by parallel-beam, fan-beam and cone-beam. Due to the potential of compact imaging systems with magnified spatial resolution, cone-beam DPC-CT has attracted significant interest. In this paper, we report a reconstruction method based on a back-projection filtration (BPF) algorithm for cone-beam DPC-CT. Due to the differential nature of phase contrast projections, the algorithm restrains from differentiation of the projection data prior to back-projection, unlike BPF algorithms commonly used for absorption-based CT data. This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured with a three-grating interferometer and a micro-focus x-ray tube source. Moreover, the numerical simulation and experimental results demonstrate that the proposed method can deal with several classes of truncated cone-beam datasets. We believe that this feature is of particular interest for future medical cone-beam phase-contrast CT imaging applications.

Accuracy and reproducibility of voxel based superimposition of cone beam computed tomography models on the anterior cranial base and the zygomatic arches

NARCIS (Netherlands)

Nada, R.M.; Maal, T.J.J.; Breuning, K.H.; Berge, S.J.; Mostafa, Y.A.; Kuijpers-Jagtman, A.M.

2011-01-01

Superimposition of serial Cone Beam Computed Tomography (CBCT) scans has become a valuable tool for three dimensional (3D) assessment of treatment effects and stability. Voxel based image registration is a newly developed semi-automated technique for superimposition and comparison of two CBCT scans.

Confocal non-line-of-sight imaging based on the light-cone transform

Science.gov (United States)

O’Toole, Matthew; Lindell, David B.; Wetzstein, Gordon

2018-03-01

How to image objects that are hidden from a camera’s view is a problem of fundamental importance to many fields of research, with applications in robotic vision, defence, remote sensing, medical imaging and autonomous vehicles. Non-line-of-sight (NLOS) imaging at macroscopic scales has been demonstrated by scanning a visible surface with a pulsed laser and a time-resolved detector. Whereas light detection and ranging (LIDAR) systems use such measurements to recover the shape of visible objects from direct reflections, NLOS imaging reconstructs the shape and albedo of hidden objects from multiply scattered light. Despite recent advances, NLOS imaging has remained impractical owing to the prohibitive memory and processing requirements of existing reconstruction algorithms, and the extremely weak signal of multiply scattered light. Here we show that a confocal scanning procedure can address these challenges by facilitating the derivation of the light-cone transform to solve the NLOS reconstruction problem. This method requires much smaller computational and memory resources than previous reconstruction methods do and images hidden objects at unprecedented resolution. Confocal scanning also provides a sizeable increase in signal and range when imaging retroreflective objects. We quantify the resolution bounds of NLOS imaging, demonstrate its potential for real-time tracking and derive efficient algorithms that incorporate image priors and a physically accurate noise model. Additionally, we describe successful outdoor experiments of NLOS imaging under indirect sunlight.

3D modeling of electric fields in the LUX detector

OpenAIRE

Akerib, DS; Alsum, S; Araújo, HM; Bai, X; Bailey, AJ; Balajthy, J; Beltrame, P; Bernard, EP; Bernstein, A; Biesiadzinski, TP; Boulton, EM; Brás, P; Byram, D; Cahn, SB; Carmona-Benitez, MC

2017-01-01

© 2017 IOP Publishing Ltd and Sissa Medialab. This work details the development of a three-dimensional (3D) electric field model for the LUX detector. The detector took data to search for weakly interacting massive particles (WIMPs) during two periods. After the first period completed, a time-varying non-uniform negative charge developed in the polytetrafluoroethylene (PTFE) panels that define the radial boundary of the detector's active volume. This caused electric field variations in the de...

Production facility for ATLAS new small wheel drift panels at JGU Mainz

Energy Technology Data Exchange (ETDEWEB)

Duedder, Andreas; Lin, Tai-Hua; Schott, Matthias [Johannes Gutenberg-Universitaet Mainz (Germany)

2016-07-01

The ATLAS Phase-I Upgrade in 2018 includes the replacement of the ATLAS Muon Small Wheel by the so-called New Small Wheel (NSW). Large-scale Micromegas detectors will serve as tracking detectors in the NSW. Parts of these detectors will be constructed at the Johannes Gutenberg University Mainz (JGU). In order to fulfill the requirements of the envisioned detector performance, a high precision detector construction is crucial. Especially the surface planarity of the produced detector panels has to better than 30 μm over an area of 2 m{sup 2}. Methods for the quality control of the raw material and the constructed parts have been developed and implemented. This talk gives an overview of the production facility at JGU Mainz which is used during the mass production of NSW components in coming years.

Percutaneous sacroplasty with the use of C-arm flat-panel detector CT: technical feasibility and clinical outcome

International Nuclear Information System (INIS)

Kang, Sung Eun; Lee, Joon Woo; Kim, Joo Hyung; Kang, Heung Sik; Park, Kun Woo; Yeom, Jin S.

2011-01-01

Sacroplasty for sacral insufficiency fractures (SIFs) has been performed mostly under computed tomography (CT) or fluoroscopy guidance. The purposes of this study are to describe technical tips and clinical outcomes of sacroplasty under C-arm flat panel detector CT (C-arm CT) guidance, and to compare the cement distributions shown on C-arm CT with those on multi-detector CT (MDCT). This study consisted of patients who underwent sacroplasty for SIF using C-arm CT from May 2006 to May 2009. Technical success was assessed in terms of cement filling and leakage. Clinical outcome was assessed at short-term (less than 1 month) and long-term (more than 1 month) follow-up using a four-grade patient satisfaction scale: poor, fair, good, and excellent. After sacroplasty, all patients underwent MDCT and three radiologists compared MDCT images with C-arm CT images in consensus, focusing on the cement distribution and cement leakage. Sacroplasties were performed on both sacral alae in all 8 patients (male:female = 2:6, mean age = 76.9, range = 63-82). The technical success rate was 100%. At short-term follow up, 6 patients (87.5%) reported significant improvement. Five patients (62.5%) were available for long-term follow-up and all 5 patients reported a reduced pain and an improved ability to ambulate. Using MDCT as the standard of reference, the cement distribution was visualized equally well by C-arm CT. Sacroplasty under C-arm CT showed excellent technical success and good clinical outcome. There was an excellent correlation between C-arm CT and MDCT in evaluating cement distribution and cement leakage. (orig.)

Percutaneous sacroplasty with the use of C-arm flat-panel detector CT: technical feasibility and clinical outcome

Energy Technology Data Exchange (ETDEWEB)

Kang, Sung Eun; Lee, Joon Woo; Kim, Joo Hyung; Kang, Heung Sik [Seoul National University Bundang Hospital, Department of Radiology, Gyeonggi-do (Korea, Republic of); Park, Kun Woo; Yeom, Jin S. [Seoul National University Bundang Hospital, Department of Orthopaedic Surgery, Gyeonggi-do (Korea, Republic of)

2011-04-15

Sacroplasty for sacral insufficiency fractures (SIFs) has been performed mostly under computed tomography (CT) or fluoroscopy guidance. The purposes of this study are to describe technical tips and clinical outcomes of sacroplasty under C-arm flat panel detector CT (C-arm CT) guidance, and to compare the cement distributions shown on C-arm CT with those on multi-detector CT (MDCT). This study consisted of patients who underwent sacroplasty for SIF using C-arm CT from May 2006 to May 2009. Technical success was assessed in terms of cement filling and leakage. Clinical outcome was assessed at short-term (less than 1 month) and long-term (more than 1 month) follow-up using a four-grade patient satisfaction scale: poor, fair, good, and excellent. After sacroplasty, all patients underwent MDCT and three radiologists compared MDCT images with C-arm CT images in consensus, focusing on the cement distribution and cement leakage. Sacroplasties were performed on both sacral alae in all 8 patients (male:female = 2:6, mean age = 76.9, range = 63-82). The technical success rate was 100%. At short-term follow up, 6 patients (87.5%) reported significant improvement. Five patients (62.5%) were available for long-term follow-up and all 5 patients reported a reduced pain and an improved ability to ambulate. Using MDCT as the standard of reference, the cement distribution was visualized equally well by C-arm CT. Sacroplasty under C-arm CT showed excellent technical success and good clinical outcome. There was an excellent correlation between C-arm CT and MDCT in evaluating cement distribution and cement leakage. (orig.)

Cone pigments in a North American marsupial, the opossum (Didelphis virginiana).

Science.gov (United States)

Jacobs, Gerald H; Williams, Gary A

2010-05-01

Only two of the four cone opsin gene families found in vertebrates are represented in contemporary eutherian and marsupial species. Recent genetic studies of two species of South American marsupial detected the presence of representatives from two of the classes of cone opsin genes and the structures of these genes predicted cone pigments with respective peaks in the ultraviolet and long-wavelength portions of the spectrum. The Virginia opossum (Didelphis virginiana), a profoundly nocturnal animal, is the only marsupial species found in North America. The prospects for cone-based vision in this species were examined through recordings of the electroretinogram (ERG), a commonly examined retinal response to photic stimulation. Recorded under flickering-light conditions that elicit signals from cone photoreceptors, the spectral sensitivity of the opossum eye is well accounted for by contributions from the presence of a single cone pigment having peak absorption at 561-562 nm. A series of additional experiments that employed various chromatic adaptation paradigms were conducted in a search for possible contributions from a second (short-wavelength sensitive) cone pigment. We found no evidence that such a mechanism contributes to the ERG in this marsupial.

Flexible X-ray detector based on sliced lead iodide crystal

Energy Technology Data Exchange (ETDEWEB)

Sun, Hui; Gao, Xiuying [College of Optoelectronic Technology, Chengdu University of Information Technology, Chengdu (China); Department of Materials Science, Sichuan University, Chengdu (China); Zhao, Beijun [Department of Materials Science, Sichuan University, Chengdu (China); Yang, Dingyu; Wangyang, Peihua; Zhu, Xinghua [College of Optoelectronic Technology, Chengdu University of Information Technology, Chengdu (China)

2017-02-15

A promising flexible X-ray detector based on inorganic semiconductor PbI{sub 2} crystal is reported. The sliced crystals mechanically cleaved from an as-grown PbI{sub 2} crystal act as the absorber directly converting the impinging X-ray photons to electron hole pairs. Due to the ductile feature of the PbI{sub 2} crystal, the detector can be operated under a highly curved state with the strain on the top surface up to 1.03% and still maintaining effective detection performance. The stable photocurrent and fast response were obtained with the detector repeated bending to a strain of 1.03% for 100 cycles. This work presents an approach for developing efficient and cost-effective PbI{sub 2}-based flexible X-ray detector. Photocurrent responses of the flexible PbI{sub 2} X-ray detector with the strain on the top surface up to 1.03% proposed in this work with the cross sectional structure and curved detector photograph as insets. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Precise mass detector based on carbon nanooscillator

Energy Technology Data Exchange (ETDEWEB)

Lukashenko, S., E-mail: lukashenko13@mail.ru; Golubok, A. [Department of Nanotechnology and Material Science, ITMO University, Kronverskiy av. 49, 192000, St. Petersburg (Russian Federation); Institute for Analytical Instrumentation of RAS, Rizhsky pr 26, St. Petersburg, 190103 (Russian Federation); Komissarenko, F. [Department of Nanotechnology and Material Science, ITMO University, Kronverskiy av. 49, 192000, St. Petersburg (Russian Federation); Academic University, Russian Academy of Sciences, ul. Khlopina 8/3, 194021, St. Petersburg (Russian Federation); Mukhin, I. [Academic University, Russian Academy of Sciences, ul. Khlopina 8/3, 194021, St. Petersburg (Russian Federation); Sapozhnikov, I. [Institute for Analytical Instrumentation of RAS, Rizhsky pr 26, St. Petersburg, 190103 (Russian Federation); Veniaminov, A. [Centre for Information Optical Technologies, ITMO University, Birzhevaya ln. 14-16, 199034, St. Petersburg (Russian Federation); Lysak, V. [Department of Nanotechnology and Material Science, ITMO University, Kronverskiy av. 49, 192000, St. Petersburg (Russian Federation)

2016-06-17

Precise mass detectors based on an amorphous carbon nanowires, which localized on the top of a tungsten tip were fabricated and investigated. The nanowires were grown in the scanning electron microscope (SEM) chamber using focused electron beam technique. The movement trajectories and amplitude-frequency characteristics of the carbon nanowire oscillators were visualized at low and ambient pressure using SEM and confocal laser scanning microscope (CLSM), respectevely. The SiO{sub 2} and TiO{sub 2} nanospheres were clamped on the top of the carbon nanowires. The manipulations of nanospheres were provided by means of dielectrophoretic force in SEM. The sensitivity of the mass detector based on the carbon nanowire oscillator was estimated.

A Bootstrap Neural Network Based Heterogeneous Panel Unit Root Test: Application to Exchange Rates

OpenAIRE

Christian de Peretti; Carole Siani; Mario Cerrato

2010-01-01

This paper proposes a bootstrap artificial neural network based panel unit root test in a dynamic heterogeneous panel context. An application to a panel of bilateral real exchange rate series with the US Dollar from the 20 major OECD countries is provided to investigate the Purchase Power Parity (PPP). The combination of neural network and bootstrapping significantly changes the findings of the economic study in favour of PPP.

Determination of HCME 3-D parameters using a full ice-cream cone model

Science.gov (United States)

Na, Hyeonock; Moon, Yong-Jae; Lee, Harim

2016-05-01

It is very essential to determine three dimensional parameters (e.g., radial speed, angular width, source location) of Coronal Mass Ejections (CMEs) for space weather forecast. Several cone models (e.g., an elliptical cone model, an ice-cream cone model, an asymmetric cone model) have been examined to estimate these parameters. In this study, we investigate which cone type is close to a halo CME morphology using 26 CMEs: halo CMEs by one spacecraft (SOHO or STEREO-A or B) and as limb CMEs by the other ones. From cone shape parameters of these CMEs such as their front curvature, we find that near full ice-cream cone type CMEs are much closer to observations than shallow ice-cream cone type CMEs. Thus we develop a new cone model in which a full ice-cream cone consists of many flat cones with different heights and angular widths. This model is carried out by the following steps: (1) construct a cone for given height and angular width, (2) project the cone onto the sky plane, (3) select points comprising the outer boundary, and (4) minimize the difference between the estimated projection speeds with the observed ones. By applying this model to 12 SOHO/LASCO halo CMEs, we find that 3-D parameters from our method are similar to those from other stereoscopic methods (a geometrical triangulation method and a Graduated Cylindrical Shell model) based on multi-spacecraft data. We are developing a general ice-cream cone model whose front shape is a free parameter determined by observations.

Silicon Based Mid Infrared SiGeSn Heterostructure Emitters and Detectors

Science.gov (United States)

2016-05-16

AFRL-AFOSR-JP-TR-2016-0054 Silicon based mid infrared SiGeSn heterostrcture emitters and detectors Greg Sun UNIVERSITY OF MASSACHUSETTS Final Report... Silicon Based Mid Infrared SiGeSn Heterostructure Emitters and Detectors ” February 10, 2016 Principal Investigator: Greg Sun Engineering...diodes are incompatible with the CMOS process and therefore cannot be easily integrated with Si electronics . The GeSn mid IR detectors developed in

Operational Experience with the ATLAS Pixel Detector

CERN Document Server

Lantzsch, Kerstin; The ATLAS collaboration

2016-01-01

Run 2 of the LHC is providing new challenges to track and vertex reconstruction with higher energies, denser jets and higher rates. Therefore the ATLAS experiment has constructed the first 4-layer Pixel detector in HEP, installing a new Pixel layer, also called Insertable B-Layer (IBL). In addition the Pixel detector was refurbished with new service quarter panels to recover about 3% of defective modules lost during run 1 and a new optical readout system to readout the data at higher speed while reducing the occupancy when running with increased luminosity. The commissioning, operation and performance of the 4-layer Pixel Detector will be presented.

System architecture of Detector Control and safety for the ATLAS Inner Detector Upgrade

International Nuclear Information System (INIS)

Ferrere, D.; Kersten, S.

2011-01-01

In the current ATLAS Upgrade plan a new Inner Detector (ID) based upon silicon sensor technology is being considered. The operational monitoring and control of the ID will be very demanding. The Detector Control System (DCS) is a common tool that is essential for the operational safety of a system. Even at this early stage the DCS system architecture has to be defined such that it is well integrated and optimized for its later implementation and use. For example the DCS diagnostics for the front-end (FE) chips is a serious option being considered that needs an early requirement and specification definition. In addition one of the main constraints is the service reuse between the service patch panels of the ATLAS ID and the counting room that limits the number of electrical lines to be reused. Conceptual differences in terms of readout architecture and layout have been identified between the strip and the pixel detector that lead to two distinct architectures. Nevertheless, the limitation of available electrical lines going to the counting room as well as the low material budget requirements inside the ID volume are two major constraints that lead the ID to consider an on-detector radiation hard integrated circuitry for the slow control. At this stage of the project, the definitions of the logical actions and protocol for the ADCs of such a chip are still being specified. In addition the experience gained from the current ID will be essential for the guidance of tuning the future DCS architecture in the coming years.

Cinder cones of Mount Slamet, Central Java, Indonesia

Directory of Open Access Journals (Sweden)

Igan S. SutawIdjaja

2014-06-01

Full Text Available http://dx.doi.org/10.17014/ijog.vol4no1.20096The Mount Slamet volcanic field in Central Java, Indonesia, contains thirty five cinder cones within an area of 90 sq. km in the east flank of the volcano. The cinder cones occur singly or in small groups, with diameter of the base ranges from 130 - 750 m and the height is around 250 m. Within the volcanic field, the cinder cones are spread over the volcanic area at the distance of 4 to 14 km from the eruption center of the Slamet Volcano. They are concentrated within latitudes 7°11’00” - 7°16’00” S,, and longitudes 109°15’00” - 109°18’00” E. The density of the cinder cones is about 1.5 cones/km2. Most of the cinder cones lie on the Tertiary sedimentary rocks along the NW-trending fault system and on radial fractures. The structural pattern may be related to the radial faults in this region. The cone surfaces are commonly blanketed by Slamet air-falls and lava flows. The deposits consist of poorly bedded, very coarse-grained, occasionally overlain by oxidized scoria, and large-sized of ballistic bombs and blocks. There are various kind of volcanic bombs originating from scoriae ballistic rock fragments. The other kind of volcanic bombs are breadcrust bomb, almond seed or contorted shape. All of the cinder cones have undergone degradation, which can be observed from the characters of gully density and surface morphology. By using Porter parameters, Hco is equal to 0.25 Wco, whilst Wcr is equal to 0.40 Wco. The Hco/Wco ratio is higher than Hco = 0.2 Wco reference line. A radiometric dating using K-Ar method carried out on a scoria bomb yields the age of 0.042 + 0.020 Ma.  

Solar panel truss mounting systems and methods

Energy Technology Data Exchange (ETDEWEB)

Al-Haddad, Tristan Farris; Cavieres, Andres; Gentry, Russell; Goodman, Joseph; Nolan, Wade; Pitelka, Taylor; Rahimzadeh, Keyan; Brooks, Bradley; Lohr, Joshua; Crooks, Ryan; Porges, Jamie; Rubin, Daniel

2016-06-28

An exemplary embodiment of the present invention provides a solar panel truss mounting system comprising a base and a truss assembly coupled to the base. The truss assembly comprises a first panel rail mount, second panel rail mount parallel to the first panel rail mount, base rail mount parallel to the first and second panel rail mounts, and a plurality of support members. A first portion of the plurality of support members extends between the first and second panel rail mounts. A second portion of the plurality of support members extends between the first panel rail mount and the base rail mount. A third portion of the plurality of support members extends between the second panel rail mount and the base rail mount. The system can further comprise a plurality of connectors for coupling a plurality of photovoltaic solar panels to the truss assembly.

Solar panel truss mounting systems and methods

Energy Technology Data Exchange (ETDEWEB)

Al-Haddad, Tristan Farris; Cavieres, Andres; Gentry, Russell; Goodman, Joseph; Nolan, Wade; Pitelka, Taylor; Rahimzadeh, Keyan; Brooks, Bradley; Lohr, Joshua; Crooks, Ryan; Porges, Jamie; Rubin, Daniel

2018-01-30

An exemplary embodiment of the present invention provides a solar panel truss mounting system comprising a base and a truss assembly coupled to the base. The truss assembly comprises a first panel rail mount, second panel rail mount parallel to the first panel rail mount, base rail mount parallel to the first and second panel rail mounts, and a plurality of support members. A first portion of the plurality of support members extends between the first and second panel rail mounts. A second portion of the plurality of support members extends between the first panel rail mount and the base rail mount. A third portion of the plurality of support members extends between the second panel rail mount and the base rail mount. The system can further comprise a plurality of connectors for coupling a plurality of photovoltaic solar panels to the truss assembly.

Solar panel truss mounting systems and methods

Science.gov (United States)

Al-Haddad, Tristan Farris; Cavieres, Andres; Gentry, Russell; Goodman, Joseph; Nolan, Wade; Pitelka, Taylor; Rahimzadeh, Keyan; Brooks, Bradley; Lohr, Joshua; Crooks, Ryan; Porges, Jamie; Rubin, Daniel

2015-10-20

An exemplary embodiment of the present invention provides a solar panel truss mounting system comprising a base and a truss assembly coupled to the base. The truss assembly comprises a first panel rail mount, second panel rail mount parallel to the first panel rail mount, base rail mount parallel to the first and second panel rail mounts, and a plurality of support members. A first portion of the plurality of support members extends between the first and second panel rail mounts. A second portion of the plurality of support members extends between the first panel rail mount and the base rail mount. A third portion of the plurality of support members extends between the second panel rail mount and the base rail mount. The system can further comprise a plurality of connectors for coupling a plurality of photovoltaic solar panels to the truss assembly.

Panel data analysis using EViews

CERN Document Server

Agung, I Gusti Ngurah

2013-01-01

A comprehensive and accessible guide to panel data analysis using EViews software This book explores the use of EViews software in creating panel data analysis using appropriate empirical models and real datasets. Guidance is given on developing alternative descriptive statistical summaries for evaluation and providing policy analysis based on pool panel data. Various alternative models based on panel data are explored, including univariate general linear models, fixed effect models and causal models, and guidance on the advantages and disadvantages of each one is given. Panel Data Analysis

Point spread function modeling and image restoration for cone-beam CT

International Nuclear Information System (INIS)

Zhang Hua; Shi Yikai; Huang Kuidong; Xu Zhe

2015-01-01

X-ray cone-beam computed tomography (CT) has such notable features as high efficiency and precision, and is widely used in the fields of medical imaging and industrial non-destructive testing, but the inherent imaging degradation reduces the quality of CT images. Aimed at the problems of projection image degradation and restoration in cone-beam CT, a point spread function (PSF) modeling method is proposed first. The general PSF model of cone-beam CT is established, and based on it, the PSF under arbitrary scanning conditions can be calculated directly for projection image restoration without the additional measurement, which greatly improved the application convenience of cone-beam CT. Secondly, a projection image restoration algorithm based on pre-filtering and pre-segmentation is proposed, which can make the edge contours in projection images and slice images clearer after restoration, and control the noise in the equivalent level to the original images. Finally, the experiments verified the feasibility and effectiveness of the proposed methods. (authors)

An X-Ray computed tomography/positron emission tomography system designed specifically for breast imaging.

Science.gov (United States)

Boone, John M; Yang, Kai; Burkett, George W; Packard, Nathan J; Huang, Shih-ying; Bowen, Spencer; Badawi, Ramsey D; Lindfors, Karen K

2010-02-01

Mammography has served the population of women who are at-risk for breast cancer well over the past 30 years. While mammography has undergone a number of changes as digital detector technology has advanced, other modalities such as computed tomography have experienced technological sophistication over this same time frame as well. The advent of large field of view flat panel detector systems enable the development of breast CT and several other niche CT applications, which rely on cone beam geometry. The breast, it turns out, is well suited to cone beam CT imaging because the lack of bones reduces artifacts, and the natural tapering of the breast anteriorly reduces the x-ray path lengths through the breast at large cone angle, reducing cone beam artifacts as well. We are in the process of designing a third prototype system which will enable the use of breast CT for image guided interventional procedures. This system will have several copies fabricated so that several breast CT scanners can be used in a multi-institutional clinical trial to better understand the role that this technology can bring to breast imaging.

Electronic readout for THGEM detectors based on FPGA TDCs

Energy Technology Data Exchange (ETDEWEB)

Baumann, Tobias; Buechele, Maximilian; Fischer, Horst; Gorzellik, Matthias; Grussenmeyer, Tobias; Herrmann, Florian; Joerg, Philipp; Koenigsmann, Kay; Kremser, Paul; Kunz, Tobias; Michalski, Christoph; Schopferer, Sebastian; Szameitat, Tobias [Physikalisches Institut, Freiburg Univ. (Germany); Collaboration: COMPASS-II RICH upgrade Group

2013-07-01

In the framework of the RD51 programme the characteristics of a new detector design, called THGEM, which is based on multi-layer arrangements of printed circuit board material, is investigated. The THGEMs combine the advantages for covering gains up to 10{sup 6} in electron multiplication at large detector areas and low material budget. Studies are performed by extending the design to a hybrid gas detector by adding a Micromega layer, which significantly improves the ion back flow ratio of the chamber. With the upgrade of the COMPASS experiment at CERN a MWPC plane of the RICH-1 detector will be replaced by installing THGEM chambers. This summarizes to 40k channels of electronic readout, including amplification, discrimination and time-to-digital conversion of the anode signals. Due to the expected hit rate of the detector we design a cost-efficient TDC, based on Artix7 FPGA technology, with time resolution below 100 ps and sufficient hit buffer depth. To cover the large readout area the data is transferred via optical fibres to a central readout system which is part of the GANDALF framework.

An InGrid based Low Energy X-ray Detector

CERN Document Server

Krieger, Christoph; Kaminski, Jochen; Lupberger, Michael; Vafeiadis, Theodoros

2014-01-01

An X-ray detector based on the combination of an integrated Micromegas stage with a pixel chip has been built in order to be installed at the CERN Axion Solar Telescope. Due to its high granularity and spatial resolution this detector allows for a topological background suppression along with a detection threshold below $1\\,\\text{keV}$. Tests at the CAST Detector Lab show the detector's ability to detect X-ray photons down to an energy as low as $277\\,\\text{eV}$. The first background data taken after the installation at the CAST experiment underline the detector's performance with an average background rate of $5\\times10^{-5}\\,/\\text{keV}/\\text{cm}^2/\\text{s}$ between 2 and $10\\,\\text{keV}$ when using a lead shielding.

Mach cones in space and laboratory dusty magnetoplasmas

International Nuclear Information System (INIS)

Mamun, A.A.; Shukla, P.K

2004-07-01

We present a rigorous theoretical investigation on the possibility for the formation of Mach cones in both space and laboratory dusty magnetoplasmas. We find the parametric regimes for which different types of Mach cones, such as dust acoustic Mach cones, dust magneto-acoustic Mach cones, oscillonic Mach cones, etc. are formed in space and laboratory dusty magnetoplasmas. We also identify the basic features of such different classes of Mach cones (viz. dust- acoustic, dust magneto-acoustic, oscillonic Mach cones, etc.), and clearly explain how they are relevant to space and laboratory dusty manetoplasmas. (author)

Review on the characteristics of radiation detectors for dosimetry and imaging

International Nuclear Information System (INIS)

Seco, Joao; Clasie, Ben; Partridge, Mike

2014-01-01

The enormous advances in the understanding of human anatomy, physiology and pathology in recent decades have led to ever-improving methods of disease prevention, diagnosis and treatment. Many of these achievements have been enabled, at least in part, by advances in ionizing radiation detectors. Radiology has been transformed by the implementation of multi-slice CT and digital x-ray imaging systems, with silver halide films now largely obsolete for many applications. Nuclear medicine has benefited from more sensitive, faster and higher-resolution detectors delivering ever-higher SPECT and PET image quality. PET/MR systems have been enabled by the development of gamma ray detectors that can operate in high magnetic fields. These huge advances in imaging have enabled equally impressive steps forward in radiotherapy delivery accuracy, with 4DCT, PET and MRI routinely used in treatment planning and online image guidance provided by cone-beam CT. The challenge of ensuring safe, accurate and precise delivery of highly complex radiation fields has also both driven and benefited from advances in radiation detectors. Detector systems have been developed for the measurement of electron, intensity-modulated and modulated arc x-ray, proton and ion beams, and around brachytherapy sources based on a very wide range of technologies. The types of measurement performed are equally wide, encompassing commissioning and quality assurance, reference dosimetry, in vivo dosimetry and personal and environmental monitoring. In this article, we briefly introduce the general physical characteristics and properties that are commonly used to describe the behaviour and performance of both discrete and imaging detectors. The physical principles of operation of calorimeters; ionization and charge detectors; semiconductor, luminescent, scintillating and chemical detectors; and radiochromic and radiographic films are then reviewed and their principle applications discussed. Finally, a general

Panel 5: Microbiology and Immunology Panel

Science.gov (United States)

Murphy, Timothy F.; Chonmaitree, Tasnee; Barenkamp, Stephen; Kyd, Jennelle; Nokso-Koivisto, Johanna; Patel, Janak A.; Heikkinen, Terho; Yamanaka, Noboru; Ogra, Pearay; Swords, W. Edward; Sih, Tania; Pettigrew, Melinda M.

2014-01-01

Objective The objective is to perform a comprehensive review of the literature from January 2007 through June 2011 on the virology, bacteriology, and immunology related to otitis media. Data Sources PubMed database of the National Library of Medicine. Review Methods Three subpanels with co-chairs comprising experts in the virology, bacteriology, and immunology of otitis media were formed. Each of the panels reviewed the literature in their respective fields and wrote draft reviews. The reviews were shared with all panel members, and a second draft was created. The entire panel met at the 10th International Symposium on Recent Advances in Otitis Media in June 2011 and discussed the review and refined the content further. A final draft was created, circulated, and approved by the panel. Conclusion Excellent progress has been made in the past 4 years in advancing an understanding of the microbiology and immunology of otitis media. Advances include laboratory-based basic studies, cell-based assays, work in animal models, and clinical studies. Implications for Practice The advances of the past 4 years formed the basis of a series of short-term and long-term research goals in an effort to guide the field. Accomplishing these goals will provide opportunities for the development of novel interventions, including new ways to better treat and prevent otitis media. PMID:23536533

FastSim: A Fast Simulation for the SuperB Detector

International Nuclear Information System (INIS)

Andreassen, R; Sokoloff, M; Arnaud, N; Burmistrov, L; Brown, D N; Carlson, J; Gaponenko, I; Suzuki, A; Cheng, C-h; Simone, A Di; Manoni, E; Perez, A; Walsh, J; Rama, M; Roberts, D; Rotondo, M; Simi, G

2011-01-01

We have developed a parameterized (fast) simulation for detector optimization and physics reach studies of the proposed SuperB Flavor Factory in Italy. Detector components are modeled as thin sections of planes, cylinders, disks or cones. Particle-material interactions are modeled using simplified cross-sections and formulas. Active detectors are modeled using parameterized response functions. Geometry and response parameters are configured using xml files with a custom-designed schema. Reconstruction algorithms adapted from BaBar are used to build tracks and clusters. Multiple sources of background signals can be merged with primary signals. Pattern recognition errors are modeled statistically by randomly misassigning nearby tracking hits. Standard BaBar analysis tuples are used as an event output. Hadronic B meson pair events can be simulated at roughly 10Hz.

FastSim: A Fast Simulation for the SuperB Detector

Science.gov (United States)

Andreassen, R.; Arnaud, N.; Brown, D. N.; Burmistrov, L.; Carlson, J.; Cheng, C.-h.; Di Simone, A.; Gaponenko, I.; Manoni, E.; Perez, A.; Rama, M.; Roberts, D.; Rotondo, M.; Simi, G.; Sokoloff, M.; Suzuki, A.; Walsh, J.

2011-12-01

We have developed a parameterized (fast) simulation for detector optimization and physics reach studies of the proposed SuperB Flavor Factory in Italy. Detector components are modeled as thin sections of planes, cylinders, disks or cones. Particle-material interactions are modeled using simplified cross-sections and formulas. Active detectors are modeled using parameterized response functions. Geometry and response parameters are configured using xml files with a custom-designed schema. Reconstruction algorithms adapted from BaBar are used to build tracks and clusters. Multiple sources of background signals can be merged with primary signals. Pattern recognition errors are modeled statistically by randomly misassigning nearby tracking hits. Standard BaBar analysis tuples are used as an event output. Hadronic B meson pair events can be simulated at roughly 10Hz.

Efficacy and safety of balloon pulmonary angioplasty for chronic thromboembolic pulmonary hypertension guided by cone-beam computed tomography and electrocardiogram-gated area detector computed tomography.

Science.gov (United States)

Ogo, Takeshi; Fukuda, Tetsuya; Tsuji, Akihiro; Fukui, Shigefumi; Ueda, Jin; Sanda, Yoshihiro; Morita, Yoshiaki; Asano, Ryotaro; Konagai, Nao; Yasuda, Satoshi

2017-04-01

Chronic thromboembolic pulmonary hypertension (CTEPH) is a disease characterized by chronic obstructive thrombus and pulmonary hypertension. Balloon pulmonary angioplasty (BPA), an emerging alternative catheter-based treatment for inoperable patients with CTEPH, has not yet been standardised, especially for lesion assessment in distal pulmonary arteries. Recent advancement in computed tomography enables distal CTEPH lesions to be visualized. We retrospectively studied 80 consecutive patients with inoperable CTEPH who received BPA guided by cone-beam computed tomography (CT) (CBCT) or electrocardiogram (ECG)-gated area detector CT (ADCT) for target lesion assessment. We collected clinical and hemodynamic data, including procedural complications, before BPA and at 3 months and 1year after BPA. Three hundred eight-five BPA sessions (4.8 sessions/patient) were performed for the lesions of subsegmental arteries (1155 lesions), segmental arteries (738 lesions), and lobar arteries (4 lesions) identified by CBCT or ECG-gated ADCT. Significant improvements in the symptoms, 6-min walk distance, brain natriuretic peptide level, exercise capacity, and haemodynamics were observed 3 months and 1year after BPA. No cases of death or cardiogenic shock with a low rate of severe wire perforation (0.3%) and severe reperfusion oedema (0.3%) were observed. BPA guided by CBCT or ECG-gated ADCT is effective and remarkably safe in patients with CTEPH . These new advanced CT techniques may be useful in pre-BPA target lesion assessment. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

RID-41 gamma flaw detector

International Nuclear Information System (INIS)

Glebov, V.N.; Zubkov, V.S.; Majorov, A.N.; Murashev, A.I.; Firstov, V.G.; Yampol'skij, V.V.; Goncharov, V.I.; Sakhanov, A.S.

1978-01-01

The design is described and the main characteristics are given of a universal stationary hose-type gamma flow detector with a 60 Co source from 3O to 4g0 Ci for high-productive control of thick-walled products from steel and other materials. The principal units of the instrument are a radiation head, a control panel, and a charge-exchange container. The flaw detector may be used both in shield chambers and in shop or mounting conditions on complying with due requirements of radiation protection. The high activity of the source at relatively small dimensions of its active part ensures good detection of defects. The high radioscopy rate permits to use the flaw detector in conditions of increased background radiation, e.g. during routine repairs and inspections at nuclear power plants. The instrument may also be used in radiometric complexes, and produces a considerable economic effect. This flaw-detector corresponds to ISO and IAEA requirements and may be delivered for export

Tokay gecko photoreceptors achieve rod-like physiology with cone-like proteins.

Science.gov (United States)

Zhang, Xue; Wensel, Theodore G; Yuan, Ching

2006-01-01

The retinal photoreceptors of the nocturnal Tokay gecko (Gekko gekko) consist exclusively of rods by the criteria of morphology and key features of their light responses. Unlike cones, they display robust photoresponses and have relatively slow recovery times. Nonetheless, the major and minor visual pigments identified in gecko rods are of the cone type by sequence and spectroscopic behavior. In the ongoing search for the molecular bases for the physiological differences between cones and rods, we have characterized the molecular biology and biochemistry of the gecko rod phototransduction cascade. We have cloned cDNAs encoding all or part of major protein components of the phototransduction cascade by RT-PCR with degenerate oligonucleotides designed to amplify cone- or rod-like sequences. For all proteins examined we obtained only cone-like and never rod-like sequences. The proteins identified include transducin alpha (Galphat), phosphodiesterase (PDE6) catalytic and inhibitory subunits, cyclic nucleotide-gated channel (CNGalpha) and arrestin. We also cloned cDNA encoding gecko RGS9-1 (Regulator of G Protein Signaling 9, splice variant 1), which is expressed in both rods and cones of all species studied but is typically found at 10-fold higher concentrations in cones, and found that gecko rods contain slightly lower RGS9-1 levels than mammalian rods. Furthermore, we found that the levels of GTPase accelerating protein (GAP) activity and cyclic GMP (cGMP) phosphodiesterase activity were similar in gecko and mammalian rods. These results place substantial constraints on the critical changes needed to convert a cone into a rod in the course of evolution: The many features of phototransduction molecules conserved between those expressed in gecko rods and those expressed in cones cannot explain the physiological differences, whereas the higher levels of RGS9-1 and GAP activity in cones are likely among the essential requirements for the rapid photoresponses of cones.

Development and degeneration of cone bipolar cells are independent of cone photoreceptors in a mouse model of retinitis pigmentosa.

Directory of Open Access Journals (Sweden)

Miao Chen

Full Text Available Retinal photoreceptors die during retinal synaptogenesis in a portion of retinal degeneration. Whether cone bipolar cells establish regular retinal mosaics and mature morphologies, and resist degeneration are not completely understood. To explore these issues, we backcrossed a transgenic mouse expressing enhanced green fluorescent protein (EGFP in one subset of cone bipolar cells (type 7 into rd1 mice, a classic mouse model of retinal degeneration, to examine the development and survival of cone bipolar cells in a background of retinal degeneration. Our data revealed that both the development and degeneration of cone bipolar cells are independent of the normal activity of cone photoreceptors. We found that type 7 cone bipolar cells achieved a uniform tiling of the retinal surface and developed normal dendritic and axonal arbors without the influence of cone photoreceptor innervation. On the other hand, degeneration of type 7 cone bipolar cells, contrary to our belief of central-to-peripheral progression, was spatially uniform across the retina independent of the spatiotemporal pattern of cone degeneration. The results have important implications for the design of more effective therapies to restore vision in retinal degeneration.

Improved image quality for asymmetric double-focal cone-beam SPECT

International Nuclear Information System (INIS)

Cao, Z.J.; Tsui, B.M.W.

1993-01-01

To optimize both spatial resolution and detection efficiency in brain SPECT imaging using a rectangular camera, an asymmetric double-focal cone-beam collimator is proposed with the focal points located near the base plane of the patient's head. To fit the entire head into the field-of-view of the collimator with dimensions of 50cmx40cm and at a radius-of-rotation of 15 cm, the focal lengths of the collimator are 55 and 70 cm, respectively, in the transverse and axial directions. With this geometry, the artifacts in the reconstructed image produced by the Feldkamp algorithm are more severe compared to those in a symmetric cone-beam geometry, due to the larger vertex angle between the top of the head and the base plane. To improve the reconstructed image quality, a fully three-dimensional (3D) reconstruction algorithm developed previously for single-focal cone-beam SPECT was extended to the asymmetric double-focal cone-beam geometry. The algorithm involves nonstationary 2D filtering and a reprojection technique for estimation of the missing data caused by a single-orbit cone-beam geometry. The results from simulation studies with the 3D Defrise slab phantom demonstrated that the fully 3D algorithm provided a much improved image quality in terms of reduced slice-to-slice cross talks and shape elongation compared to that produced by the conventional Feldkamp algorithm

Is energy consumption per capita broken stationary? New evidence from regional-based panels

International Nuclear Information System (INIS)

Chen, P.-F.; Lee, C.-C.

2007-01-01

For the first time, a new panel unit root testing procedure, developed by [51]Carrion-i-Silvestre et al. [2005. Breaking the panels: an application to GDP per capita. Econometrics Journal 8, 159-175], is applied to re-investigate the stationarity of energy consumption per capita for 7 regional panel sets covering the 1971-2002 period. With structural breaks and cross-sectional correlations introduced into the model, it becomes clear that all regional-based panels of energy consumption per capita are stationary. The structural breakpoints identify the likely causes of major changes in energy consumption in the past. The findings underscore the importance of accounting for exogenous shocks to a series and offer several important implications for policy makers and energy economists

Design of a trichromatic cone array.

Directory of Open Access Journals (Sweden)

Patrick Garrigan

2010-02-01

Full Text Available Cones with peak sensitivity to light at long (L, medium (M and short (S wavelengths are unequal in number on the human retina: S cones are rare (<10% while increasing in fraction from center to periphery, and the L/M cone proportions are highly variable between individuals. What optical properties of the eye, and statistical properties of natural scenes, might drive this organization? We found that the spatial-chromatic structure of natural scenes was largely symmetric between the L, M and S sensitivity bands. Given this symmetry, short wavelength attenuation by ocular media gave L/M cones a modest signal-to-noise advantage, which was amplified, especially in the denser central retina, by long-wavelength accommodation of the lens. Meanwhile, total information represented by the cone mosaic remained relatively insensitive to L/M proportions. Thus, the observed cone array design along with a long-wavelength accommodated lens provides a selective advantage: it is maximally informative.

Shape measurement and vibration analysis of moving speaker cone

Science.gov (United States)

Zhang, Qican; Liu, Yuankun; Lehtonen, Petri

2014-06-01

Surface three-dimensional (3-D) shape information is needed for many fast processes such as structural testing of material, standing waves on loudspeaker cone, etc. Usually measurement is done from limited number of points using electrical sensors or laser distance meters. Fourier Transform Profilometry (FTP) enables fast shape measurement of the whole surface. Method is based on angled sinusoidal fringe pattern projection and image capturing. FTP requires only one image of the deformed fringe pattern to restore the 3-D shape of the measured object, which makes real-time or dynamic data processing possible. In our experiment the method was used for loudspeaker cone distortion measurement in dynamic conditions. For sound quality issues it is important that the whole cone moves in same phase and there are no partial waves. Our imaging resolution was 1280x1024 pixels and frame rate was 200 fps. Using our setup we found unwanted spatial waves in our sample cone.

THGEM based photon detector for Cherenkov imaging applications

CERN Document Server

Alexeev, M; Bradamante, F; Bressan, A; Chiosso, M; Ciliberti, P; Croci, G; Colantoni, M L; Dalla Torre, S; Duarte Pinto, S; Denisov, O; Diaz, V; Ferrero, A; Finger, M; Finger, M Jr; Fischer, H; Giacomini, G; Giorgi, M; Gobbo, B; Heinsius, F H; Herrmann, F; Jahodova, V; Königsmann, K; Lauser, L; Levorato, S; Maggiora, A; Martin, A; Menon, G; Nerling, F; Panzieri, D; Pesaro, G; Polak, J; Rocco, E; Ropelewski, L; Sauli, F; Sbrizzai, G; Schiavon, P; Schill, C; Schopferer, S; Slunecka, M; Sozzi, F; Steiger, L; Sulc, M; Takekawa, S; Tessarotto, F; Wollny, H

2010-01-01

We are developing a single photon detector for Cherenkov imaging counters. This detector is based on the use of THGEM electron multipliers in a multilayer design. The major goals of our project are ion feedback suppression down to a few per cent, large gain, fast response, insensitivity to magnetic fields, and a large detector size. We report about the project status and perspectives. In particular, we present a systematic study of the THGEM response as a function of geometrical parameters, production techniques and the gas mixture composition. The first figures obtained from measuring the response of a CsI coated THGEM to single photons are presented.

Micro controller based system for characterizing gas detector operating parameters

International Nuclear Information System (INIS)

Thakur, Vaishali M.; Verma, Amit K.; Anilkumar, S.; Babu, D.A.R.; Sharma, D.N.; Harikumar, M.

2011-01-01

The estimation and analysis of radioactivity levels in samples from environment and from various stages of nuclear fuel cycle operations has become a matter of concern for the implementation of radiological safety procedures. Gas filled/ flow detectors play crucial role in achieving this objective. Since these detectors need high voltage for their operation, the operating characteristics of each detector for optimum performance has to be determined before incorporating into the systems. The operating voltages of these detectors are ranging from few hundred volts to few kilo volts. Present paper describes the design of microcontroller based system to control two HV modules (Electron tubes make: PS2001/12P) independently and acquire data from different gas filled radiation detectors simultaneously. The system uses Philips 80C552 microcontroller based Single Board Computer (SBC). The inbuilt DAC and ADC of microcontroller were used to control HV from 0-2000 with less than ± 1 %, error 1000V. The starting HV, HV step size, decision making intelligence to terminate HV increment (for preset plateau slope) and data acquisition (for preset time), data acquisition time etc., can be programmed. Nearly 200 detectors data (20 data points per detector) can be stored and transferred to PC on request. Data collected by the system for LND 719 GM detectors with starting voltage from 500 V, HV step size of 24 V and 100 seconds counting time to find out the plateau length. The plateau slope and length obtained with this system for LND 719 GM detectors are 3-5%/100V and ∼ 150V respectively. (author)

Cone and Seed Maturation of Southern Pines

Science.gov (United States)

James P. Barnett

1976-01-01

If slightly reduced yields and viability are acceptable, loblolly and slash cone collections can begin 2 to 3 weeks before maturity if the cones are stored before processing. Longleaf(P. palestris Mill.) pine cones should be collected only when mature, as storage decreased germination of seeds from immature cones. Biochemical analyses to determine reducing sugar...

A moving blocker-based strategy for simultaneous megavoltage and kilovoltage scatter correction in cone-beam computed tomography image acquired during volumetric modulated arc therapy

International Nuclear Information System (INIS)

Ouyang, Luo; Lee, Huichen Pam; Wang, Jing

2015-01-01

Purpose: To evaluate a moving blocker-based approach in estimating and correcting megavoltage (MV) and kilovoltage (kV) scatter contamination in kV cone-beam computed tomography (CBCT) acquired during volumetric modulated arc therapy (VMAT). Methods and materials: During the concurrent CBCT/VMAT acquisition, a physical attenuator (i.e., “blocker”) consisting of equally spaced lead strips was mounted and moved constantly between the CBCT source and patient. Both kV and MV scatter signals were estimated from the blocked region of the imaging panel, and interpolated into the unblocked region. A scatter corrected CBCT was then reconstructed from the unblocked projections after scatter subtraction using an iterative image reconstruction algorithm based on constraint optimization. Experimental studies were performed on a Catphan® phantom and an anthropomorphic pelvis phantom to demonstrate the feasibility of using a moving blocker for kV–MV scatter correction. Results: Scatter induced cupping artifacts were substantially reduced in the moving blocker corrected CBCT images. Quantitatively, the root mean square error of Hounsfield units (HU) in seven density inserts of the Catphan phantom was reduced from 395 to 40. Conclusions: The proposed moving blocker strategy greatly improves the image quality of CBCT acquired with concurrent VMAT by reducing the kV–MV scatter induced HU inaccuracy and cupping artifacts

Buckling behaviour of imperfect ring-stiffened cone-cylinder intersections under internal pressure

International Nuclear Information System (INIS)

Zhao, Y.

2005-01-01

Cone-cylinder intersections are used commonly in pressure vessels and piping. In the case of a cone large end-to-cylinder intersection under internal pressure, the intersection is subject to a large circumferential compressive force. While both the cone and the cylinder may be locally thickened to strengthen the intersection, it is often desirable and convenient to provide an annular plate ring at the cone-to-cylinder joint to supplement local thickening or as an alternative strengthening measure, leading to a ring-stiffened cone-cylinder intersection. Only limited work has been carried out specifically on ring-stiffened cone-cylinder intersections under internal pressure. This paper presents the first experimental study on such intersections. In addition to the presentation of test results including geometric imperfections, failure behaviour and the determination of buckling mode and load based on displacement measurements, results from nonlinear bifurcation analysis using the perfect shape and nonlinear analysis using the measured imperfect shape are presented and compared with the experimental results

Statistical reconstruction for cone-beam CT with a post-artifact-correction noise model: application to high-quality head imaging

International Nuclear Information System (INIS)

Dang, H; Stayman, J W; Sisniega, A; Xu, J; Zbijewski, W; Siewerdsen, J H; Wang, X; Foos, D H; Aygun, N; Koliatsos, V E

2015-01-01

Non-contrast CT reliably detects fresh blood in the brain and is the current front-line imaging modality for intracranial hemorrhage such as that occurring in acute traumatic brain injury (contrast ∼40–80 HU, size  >  1 mm). We are developing flat-panel detector (FPD) cone-beam CT (CBCT) to facilitate such diagnosis in a low-cost, mobile platform suitable for point-of-care deployment. Such a system may offer benefits in the ICU, urgent care/concussion clinic, ambulance, and sports and military theatres. However, current FPD-CBCT systems face significant challenges that confound low-contrast, soft-tissue imaging. Artifact correction can overcome major sources of bias in FPD-CBCT but imparts noise amplification in filtered backprojection (FBP). Model-based reconstruction improves soft-tissue image quality compared to FBP by leveraging a high-fidelity forward model and image regularization. In this work, we develop a novel penalized weighted least-squares (PWLS) image reconstruction method with a noise model that includes accurate modeling of the noise characteristics associated with the two dominant artifact corrections (scatter and beam-hardening) in CBCT and utilizes modified weights to compensate for noise amplification imparted by each correction. Experiments included real data acquired on a FPD-CBCT test-bench and an anthropomorphic head phantom emulating intra-parenchymal hemorrhage. The proposed PWLS method demonstrated superior noise-resolution tradeoffs in comparison to FBP and PWLS with conventional weights (viz. at matched 0.50 mm spatial resolution, CNR = 11.9 compared to CNR = 5.6 and CNR = 9.9, respectively) and substantially reduced image noise especially in challenging regions such as skull base. The results support the hypothesis that with high-fidelity artifact correction and statistical reconstruction using an accurate post-artifact-correction noise model, FPD-CBCT can achieve image quality allowing reliable detection of

A novel image-domain-based cone-beam computed tomography enhancement algorithm

Energy Technology Data Exchange (ETDEWEB)

Li Xiang; Li Tianfang; Yang Yong; Heron, Dwight E; Huq, M Saiful, E-mail: lix@upmc.edu [Department of Radiation Oncology, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15232 (United States)

2011-05-07

Kilo-voltage (kV) cone-beam computed tomography (CBCT) plays an important role in image-guided radiotherapy. However, due to a large cone-beam angle, scatter effects significantly degrade the CBCT image quality and limit its clinical application. The goal of this study is to develop an image enhancement algorithm to reduce the low-frequency CBCT image artifacts, which are also called the bias field. The proposed algorithm is based on the hypothesis that image intensities of different types of materials in CBCT images are approximately globally uniform (in other words, a piecewise property). A maximum a posteriori probability framework was developed to estimate the bias field contribution from a given CBCT image. The performance of the proposed CBCT image enhancement method was tested using phantoms and clinical CBCT images. Compared to the original CBCT images, the corrected images using the proposed method achieved a more uniform intensity distribution within each tissue type and significantly reduced cupping and shading artifacts. In a head and a pelvic case, the proposed method reduced the Hounsfield unit (HU) errors within the region of interest from 300 HU to less than 60 HU. In a chest case, the HU errors were reduced from 460 HU to less than 110 HU. The proposed CBCT image enhancement algorithm demonstrated a promising result by the reduction of the scatter-induced low-frequency image artifacts commonly encountered in kV CBCT imaging.

Cones fabricated by 3D nanoimprint lithography for highly sensitive surface enhanced Raman spectroscopy

International Nuclear Information System (INIS)

Wu Wei; Hu Min; Ou Fungsuong; Li Zhiyong; Williams, R Stanley

2010-01-01

We demonstrated a cost-effective and deterministic method of patterning 3D cone arrays over a large area by using nanoimprint lithography (NIL). Cones with tip radius of less than 10 nm were successfully duplicated onto the UV-curable imprint resist materials from the silicon cone templates. Such cone structures were shown to be a versatile platform for developing reliable, highly sensitive surface enhanced Raman spectroscopy (SERS) substrates. In contrast to the silicon nanocones, the SERS substrates based on the Au coated cones made by the NIL offered significant improvement of the SERS signal. A further improvement of the SERS signal was observed when the polymer cones were imprinted onto a reflective metallic mirror surface. A sub-zeptomole detection sensitivity for a model molecule, trans-1,2-bis(4-pyridyl)-ethylene (BPE), on the Au coated NIL cone surfaces was achieved.

A fast and efficient method for sequential cone-beam tomography

International Nuclear Information System (INIS)

Koehler, Th.; Proksa, R.; Grass, M.

2001-01-01

Sequential cone-beam tomography is a method that uses data of two or more parallel circular trajectories of a cone-beam scanner to reconstruct the object function. We propose a condition for the data acquisition that ensures that all object points between two successive circles are irradiated over an angular span of the x-ray source position of exactly 360 deg. in total as seen along the rotation axis. A fast and efficient approximative reconstruction method for the proposed acquisition is presented which uses data from exactly 360 deg. for every object point. It is based on the Tent-FDK method which was recently developed for single circular cone-beam CT. The measurement geometry does not provide sufficient data for exact reconstruction but it is shown that the proposed reconstruction method provides satisfying image quality for small cone angles

Status of COMPASS RICH-1 Upgrade with MPGD-based Photon Detectors

Directory of Open Access Journals (Sweden)

Alexeev M.

2018-01-01

Full Text Available A Set of new MPGD-based Photon Detectors is being built for the upgrade of COMPASS RICH-1. The detectors cover a total active area of 1.4 m2 and are based on a hybrid architecture consisting of two THGEM layers and a Micromegas. A CsI film on one THGEM acts as a reflective photocathode. The characteristics of the detector, the production of the components and their validation tests are described in detail.

OPTICALLY BASED CHARGE INJECTION SYSTEM FOR IONIZATION DETECTORS

International Nuclear Information System (INIS)

CHEN, H.; CITTERIO, M.; LANNI, F.; LEITE, M.A.L.; RADEKA, V.; RESCIA, S.; TAKAI, H.

2001-01-01

An optically coupled charge injection system for ionization based radiation detectors which allows a test charge to be injected without the creation of ground loops has been developed. An ionization like signal from an external source is brought into the detector through an optical fiber and injected into the electrodes by means of a photodiode. As an application example, crosstalk measurements on a liquid Argon electromagnetic calorimeter readout electrodes were performed

Evaluation of mechanical and thermal properties of Pine cone fibers reinforced compatibilized polypropylene

International Nuclear Information System (INIS)

Arrakhiz, F.Z.; El Achaby, M.; Benmoussa, K.; Bouhfid, R.; Essassi, E.M.; Qaiss, A.

2012-01-01

Highlights: ► Pine cone fibers are used as reinforcement in thermoplastic matrix. ► Pine cone fiber was alkali treated to remove waxes and non cellulosic component. ► Fiber–matrix adhesion was assured by the use of a SEBS-g-MA as a compatibilizer. -- Abstract: Pine cone fibers are a cellulosic material readily available and can be used as reinforcement in a thermoplastic-based composite. A solid knowledge of their fibrillar morphology and structure is required to evaluate their usefulness as a substitute to other abundant natural fibers. Pine cone fibers were alkali treated prior usage to remove waxes and non cellulosic surface component. Fiber–matrix adhesion was assured by both a styrene–(ethylene–butene)–styrene triblock copolymer grafted with maleic anhydride (SEBS-g-MA) and a linear block copolymer based on styrene and butadiene compatibilizer. Scanning Electron Microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction, Thermogravimetric analysis (TGA), tensile and torsional tests were employed for Pine cone polypropylene composite and compatibilized composite at different fiber content. Results show a clear improvement in mechanical properties from the use of both alkali treated Pine cone and Pine cone compatibilized with maleic anhydride, a gain of 43% and 49% respectively in the Young’s modulus, as a results of improved adhesion between fibers and matrix at the interface.

A new approximate algorithm for image reconstruction in cone-beam spiral CT at small cone-angles

International Nuclear Information System (INIS)

Schaller, S.; Flohr, T.; Steffen, P.

1996-01-01

This paper presents a new approximate algorithm for image reconstruction with cone-beam spiral CT data at relatively small cone-angles. Based on the algorithm of Wang et al., our method combines a special complementary interpolation with filtered backprojection. The presented algorithm has three main advantages over Wang's algorithm: (1) It overcomes the pitch limitation of Wang's algorithm. (2) It significantly improves z-resolution when suitable sampling schemes are applied. (3) It avoids the waste of applied radiation dose inherent to Wang's algorithm. Usage of the total applied dose is an important requirement in medical imaging. Our method has been implemented on a standard workstation. Reconstructions of computer-simulated data of different phantoms, assuming sampling conditions and image quality requirements typical to medical CT, show encouraging results

A novel strategy to increase separated electron-hole dipoles in commercial Si based solar panel to assist photovoltaic effect

Science.gov (United States)

Feng, Yefeng; He, Cheng-En; Xu, Zhichao; Hu, Jianbing; Peng, Cheng

2018-01-01

Interface induced polarization has been found to have a significant impact on dielectric properties of 2-2 type polymer composites bearing Si based semi-conducting ceramic sheets. Inherent overall polarity of polymer layers in 2-2 composites has been verified to be closely connected with interface effect and achieved permittivity in composites. In present work, conducting performances of monocrystalline Si sheets coated by varied high polarity material layers were deeply researched. The positive results inspired us to propose a novel strategy to improve separated electron-hole dipoles in commercial Si based solar cell panel for assisting photovoltaic effect, based on strong interface induced polarization. Conducting features of solar panels coated by two different high polarity polymer layers were detected to be greatly elevated compared with solar panel standalone, thanks to interface induced polarization between panel and polymer. Polymer coating with higher polarity would lead to more separated electron-hole dipole pairs in solar panel contributing to higher conductivity of panel. Valid synergy of interface effect and photovoltaic effect was based on their unidirectional traits of electron transfer. Dielectric properties of solar panels in composites further confirmed that strategy. This work might provide a facile route to prepare promising Si based solar panels with higher photoelectric conversion efficiency by enhancing interface induced polarization between panel and polymer coating.

Spectral characteristics of light sources for S-cone stimulation.

Science.gov (United States)

Schlegelmilch, F; Nolte, R; Schellhorn, K; Husar, P; Henning, G; Tornow, R P

2002-11-01

Electrophysiological investigations of the short-wavelength sensitive pathway of the human eye require the use of a suitable light source as a S-cone stimulator. Different light sources with their spectral distribution properties were investigated and compared with the ideal S-cone stimulator. First, the theoretical background of the calculation of relative cone energy absorption from the spectral distribution function of the light source is summarized. From the results of the calculation, the photometric properties of the ideal S-cone stimulator will be derived. The calculation procedure was applied to virtual light sources (computer generated spectral distribution functions with different medium wavelengths and spectrum widths) and to real light sources (blue and green light emitting diodes, blue phosphor of CRT-monitor, multimedia projector, LCD monitor and notebook display). The calculated relative cone absorbencies are compared to the conditions of an ideal S-cone stimulator. Monochromatic light sources with wavelengths of less than 456 nm are close to the conditions of an ideal S-cone stimulator. Spectrum widths up to 21 nm do not affect the S-cone activation significantly (S-cone activation change < 0.2%). Blue light emitting diodes with peak wavelength at 448 nm and spectrum bandwidth of 25 nm are very useful for S-cone stimulation (S-cone activation approximately 95%). A suitable display for S-cone stimulation is the Trinitron computer monitor (S-cone activation approximately 87%). The multimedia projector has a S-cone activation up to 91%, but their spectral distribution properties depends on the selected intensity. LCD monitor and notebook displays have a lower S-cone activation (< or = 74%). Carefully selecting the blue light source for S-cone stimulation can reduce the unwanted L-and M-cone activation down to 4% for M-cones and 1.5% for L-cones.