The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
John A. Rowlands - One of the best experts on this subject based on the ideXlab platform.
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Digital Radiology using active matrix readout of amorphous selenium: Theoretical analysis of detective quantum efficiency
Medical physics, 1997Co-Authors: Wei Zhao, John A. RowlandsAbstract:A flat-panel x-ray imaging detector using a layer of amorphous selenium (a-Se) for direct conversion of x rays (to charge) and an active matrix for self-scanned readout is being investigated for Digital Radiology. A theoretical analysis of the spatial frequency dependent detective quantum efficiency (DQE(f)) of the self-scanned a-Se detector is performed based on a model of signal and noise propagation in a cascaded imaging system. Because of the high intrinsic resolution of a-Se and the pixelated active matrix readout method, such detectors are inherently undersampled and aliasing is present. The presampling modulation transfer function (MTF) and aliased noise power spectrum (NPS) of the detector were used in the analysis of DQE(f). It is proven that the aliased NPS for the self-scanned a-Se detectors is white. Since the shape of DQE(f) is determined by the ratio of MTF squared and the NPS, the shape of DQE(f) follows the square of the presampling MTF of the detector as a result of the white NPS. The analysis also shows that DQE(0) is proportional to the pixel fill factor, i.e., the fraction of each pixel area used for image charge collection. The DQE analysis is applied to detector parameters for three x-ray imaging applications: mammography, chest radiography, and fluoroscopy. The effects of pixel fill factor, imaging geometry (i.e., incident angle of x rays), and various sources of electronic noise on the detector DQE(f) are discussed. Strategies for maximizing detector DQE for each x-ray imaging application are proposed.
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Characteristics of dual-gate thin-film transistors for applications in Digital Radiology
Canadian Journal of Physics, 1996Co-Authors: David Waechter, Wei Zhao, Z. Huang, Ira M. Blevis, John A. RowlandsAbstract:A large-area flat-panel detector for Digital Radiology is being developed. The detector uses an array of dual-gate thin-film transistors (TFTs) to read out X-ray-generated charge produced in an amorphous selenium (a-Se) layer. The TFTs use CdSe as the semiconductor and use the bottom gate for row selection. The top gate can be divided into a "deliberate" gate, covering most of the channel length, and smaller "parasitic" gates that consist of (i) overlap of source or drain metal over the top-gate oxide, and (ii) gap regions in the metal that are covered only by the a-Se. In this paper we present the properties of dual-gate TFTs and examine the effect of both the deliberate and parasitic gates on the detector operation. Various options for controlling the top-gate potential are analyzed and discussed.
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X-ray imaging using amorphous selenium: Feasibility of a flat panel self-scanned detector for Digital Radiology
Medical physics, 1995Co-Authors: Wei Zhao, John A. RowlandsAbstract:We investigate a concept for making a large area, flat-panel detector for Digital Radiology. It employs an x-ray sensitive photoconductor to convert incident x-radiation to a charge image which is then electronically read out with a large area integrated circuit. The large area integrated circuit, also called an active matrix, consists of a two-dimensional array of thin film transistors (TFTs). The potential advantages of the flat-panel detector for Digital radiography include: instantaneous Digital radiographs without operator intervention; compact size approaching that of a screen-film cassette and thus compatibility with existing x-ray equipment; high quantum efficiency combined with high resolution. Its potential advantages over the x-ray image intensifier (XRII)/video systems for fluoroscopy include: compactness; geometric accuracy; high resolution, and absence of veiling glare. The feasibility of the detector for Digital Radiology was investigated using the properties of a particular photoconductor (amorphous selenium) and active matrix array (with cadmium selenide TFTs). The results showed that it can potentially satisfy the detector design requirements for radiography (e.g., chest radiography and mammography). For fluoroscopy, the images can be obtained in real-time but the detector is not quantum noise limited below the mean exposure rate typically used in fluoroscopy. Possible improvements in x-ray sensitivity and noise performance for the application in fluoroscopy are discussed.
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Digital Radiology using self-scanned readout of amorphous selenium
Medical Imaging 1993: Physics of Medical Imaging, 1993Co-Authors: Wei Zhao, John A. RowlandsAbstract:A large area, flat panel detector is being investigated for Digital radiological imaging (radiography and fluoroscopy). The detector consists of an x-ray sensitive photoconductor to interact with x-rays and convert the absorbed energy to electron-hole pairs. The released charge is collected and stored on pixel electrodes and subsequently is read out electronically with an active matrix, i.e. a two dimensional array of thin films transistors (TFTs). The basic properties of the detector based on the characteristics of the photoconductor, the active matrix and the external charge amplifiers are analyzed.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Oleg S Pianykh - One of the best experts on this subject based on the ideXlab platform.
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how secure is your Radiology department mapping Digital Radiology adoption and security worldwide
American Journal of Roentgenology, 2016Co-Authors: Mark Stites, Oleg S PianykhAbstract:OBJECTIVE. Despite the long history of Digital Radiology, one of its most critical aspects—information security—still remains extremely underdeveloped and poorly standardized. To study the current state of Radiology security, we explored the worldwide security of medical image archives. MATERIALS AND METHODS. Using the DICOM data-transmitting standard, we implemented a highly parallel application to scan the entire World Wide Web of networked computers and devices, locating open and unprotected Radiology servers. We used only legal and Radiology-compliant tools. Our security-probing application initiated a standard DICOM handshake to remote computer or device addresses, and then assessed their security posture on the basis of handshake replies. RESULTS. The scan discovered a total of 2774 unprotected Radiology or DICOM servers worldwide. Of those, 719 were fully open to patient data communications. Geolocation was used to analyze and rank our findings according to country utilization. As a result, we buil...
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losing images in Digital Radiology more than you think
Journal of Digital Imaging, 2015Co-Authors: Catherine Oglevee, Oleg S PianykhAbstract:It is a common belief that the shift to Digital imaging some 20 years ago helped medical image exchange and got rid of any potential image loss that was happening with printed image films. Unfortunately, this is not the case: despite the most recent advances in Digital imaging, most hospitals still keep losing their imaging data, with these losses going completely unnoticed. As a result, not only does image loss affect the faith in Digital imaging but it also affects patient diagnosis and daily quality of clinical work. This paper identifies the origins of invisible image losses, provides methods and procedures to detect image loss, and demonstrates modes of action that can be taken to stop the problem from happening.
Wei Zhao - One of the best experts on this subject based on the ideXlab platform.
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Digital Radiology using active matrix readout of amorphous selenium: Theoretical analysis of detective quantum efficiency
Medical physics, 1997Co-Authors: Wei Zhao, John A. RowlandsAbstract:A flat-panel x-ray imaging detector using a layer of amorphous selenium (a-Se) for direct conversion of x rays (to charge) and an active matrix for self-scanned readout is being investigated for Digital Radiology. A theoretical analysis of the spatial frequency dependent detective quantum efficiency (DQE(f)) of the self-scanned a-Se detector is performed based on a model of signal and noise propagation in a cascaded imaging system. Because of the high intrinsic resolution of a-Se and the pixelated active matrix readout method, such detectors are inherently undersampled and aliasing is present. The presampling modulation transfer function (MTF) and aliased noise power spectrum (NPS) of the detector were used in the analysis of DQE(f). It is proven that the aliased NPS for the self-scanned a-Se detectors is white. Since the shape of DQE(f) is determined by the ratio of MTF squared and the NPS, the shape of DQE(f) follows the square of the presampling MTF of the detector as a result of the white NPS. The analysis also shows that DQE(0) is proportional to the pixel fill factor, i.e., the fraction of each pixel area used for image charge collection. The DQE analysis is applied to detector parameters for three x-ray imaging applications: mammography, chest radiography, and fluoroscopy. The effects of pixel fill factor, imaging geometry (i.e., incident angle of x rays), and various sources of electronic noise on the detector DQE(f) are discussed. Strategies for maximizing detector DQE for each x-ray imaging application are proposed.
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Characteristics of dual-gate thin-film transistors for applications in Digital Radiology
Canadian Journal of Physics, 1996Co-Authors: David Waechter, Wei Zhao, Z. Huang, Ira M. Blevis, John A. RowlandsAbstract:A large-area flat-panel detector for Digital Radiology is being developed. The detector uses an array of dual-gate thin-film transistors (TFTs) to read out X-ray-generated charge produced in an amorphous selenium (a-Se) layer. The TFTs use CdSe as the semiconductor and use the bottom gate for row selection. The top gate can be divided into a "deliberate" gate, covering most of the channel length, and smaller "parasitic" gates that consist of (i) overlap of source or drain metal over the top-gate oxide, and (ii) gap regions in the metal that are covered only by the a-Se. In this paper we present the properties of dual-gate TFTs and examine the effect of both the deliberate and parasitic gates on the detector operation. Various options for controlling the top-gate potential are analyzed and discussed.
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Digital Radiology using self scanned readout of amorphous selenium design considerations for mammography
Medical Imaging 1995: Physics of Medical Imaging, 1995Co-Authors: Wei Zhao, J A Rowlands, Stephen Germann, David Waechter, Zhong HuangAbstract:We are developing a large area, flat panel solid-state detector for general application to Digital Radiology. The proposed detector employs a continuous photoconductive layer of amorphous selenium ((alpha) -Se) to convert incident x rays to electron-hole pairs, which are then separated and drawn to the surface of the (alpha) -Se by an applied electric field. The resulting charge image is Digitally read out in situ using a large area active matrix array made with cadmium selenide (CdSe) thin film transistors (TFTs). The relationship between the potential imaging properties and the design parameters of this detector concept for Digital mammography were analyzed theoretically using measured characteristics of (alpha) -Se layers and CdSe active matrices.
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X-ray imaging using amorphous selenium: Feasibility of a flat panel self-scanned detector for Digital Radiology
Medical physics, 1995Co-Authors: Wei Zhao, John A. RowlandsAbstract:We investigate a concept for making a large area, flat-panel detector for Digital Radiology. It employs an x-ray sensitive photoconductor to convert incident x-radiation to a charge image which is then electronically read out with a large area integrated circuit. The large area integrated circuit, also called an active matrix, consists of a two-dimensional array of thin film transistors (TFTs). The potential advantages of the flat-panel detector for Digital radiography include: instantaneous Digital radiographs without operator intervention; compact size approaching that of a screen-film cassette and thus compatibility with existing x-ray equipment; high quantum efficiency combined with high resolution. Its potential advantages over the x-ray image intensifier (XRII)/video systems for fluoroscopy include: compactness; geometric accuracy; high resolution, and absence of veiling glare. The feasibility of the detector for Digital Radiology was investigated using the properties of a particular photoconductor (amorphous selenium) and active matrix array (with cadmium selenide TFTs). The results showed that it can potentially satisfy the detector design requirements for radiography (e.g., chest radiography and mammography). For fluoroscopy, the images can be obtained in real-time but the detector is not quantum noise limited below the mean exposure rate typically used in fluoroscopy. Possible improvements in x-ray sensitivity and noise performance for the application in fluoroscopy are discussed.
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Digital Radiology using self-scanned readout of amorphous selenium
Medical Imaging 1993: Physics of Medical Imaging, 1993Co-Authors: Wei Zhao, John A. RowlandsAbstract:A large area, flat panel detector is being investigated for Digital radiological imaging (radiography and fluoroscopy). The detector consists of an x-ray sensitive photoconductor to interact with x-rays and convert the absorbed energy to electron-hole pairs. The released charge is collected and stored on pixel electrodes and subsequently is read out electronically with an active matrix, i.e. a two dimensional array of thin films transistors (TFTs). The basic properties of the detector based on the characteristics of the photoconductor, the active matrix and the external charge amplifiers are analyzed.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Walter Hruby - One of the best experts on this subject based on the ideXlab platform.
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Digital (R)Evolution in Radiology - Digital (R)Evolution in Radiology
2001Co-Authors: Walter HrubyAbstract:Introduction Basics of Digital Radiology Planning Digital Radiology - Practical approaches Applications using new Digital technologies - Workflow Practical Applications of Digital Radiology Current developments and economic issues Epilogue.
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Digital r evolution in Radiology
2001Co-Authors: Walter HrubyAbstract:Introduction Basics of Digital Radiology Planning Digital Radiology - Practical approaches Applications using new Digital technologies - Workflow Practical Applications of Digital Radiology Current developments and economic issues Epilogue.
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Integration of ultrasound in a fully Digital Radiology department.
Investigative radiology, 1994Co-Authors: W. Krampla, Hans Mosser, Walter HrubyAbstract:The authors' experiences concerning the use of video-framegrabbers for the integration of ultrasound devices into a fully Digital imaging environment are presented. Video acquisition workstations (VAW) (Siemens, Gammasonics Inc., Hoffman Estates, IL) are used in our department to link ultrasound devices to the picture archiving and communication system (PACS). A study was carried out concerning the impact of this integration on throughput by comparing the average times for image acquisition and storage in this Digital system with the times found in a conventional archive, which is still used for some ultrasound units. The annual costs for the two kinds of archives were compared. Video acquisition is a feasible way of integrating ultrasound in a Digital environment. No impact on throughput has been found for the radiologist carrying out the examination, but for the assisting technologist, the times for image retrieval and archiving could be reduced from 3 minutes and 8 seconds to 24 seconds per patient. The instant availability of previous studies could be increased from 93.5% to almost 100%. Archive costs could be reduced by 28%, with further reductions to be expected using different archive configurations.
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The Vienna SMZO Project
Picture Archiving and Communication Systems (PACS) in Medicine, 1991Co-Authors: Hans Mosser, Alfred Mandl, Michael Urban, Helmut Hradil, Walter HrubyAbstract:This paper presents the project of the Integrated Digital Radiology System (IDRS), i.e. the integration of PACS, HIS and RIS into a totally Digital environment as planned at the SMZO hospital in Vienna, Austria. The hospital -a 1400-bed teaching institution- will start its operation in March 1992. Since 1988 a team consisting of computer engineers and radiologists has been planning the design and the operational structure of this integrated Digital Radiology service. The goal of this project is to optimize the Radiology service by improving communication within the Radiology department and with other departments and to increase the accessability of radiologic images, the basis of our daily work. The improvements in these areas certainly will result in better patient care.
Mark Stites - One of the best experts on this subject based on the ideXlab platform.
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how secure is your Radiology department mapping Digital Radiology adoption and security worldwide
American Journal of Roentgenology, 2016Co-Authors: Mark Stites, Oleg S PianykhAbstract:OBJECTIVE. Despite the long history of Digital Radiology, one of its most critical aspects—information security—still remains extremely underdeveloped and poorly standardized. To study the current state of Radiology security, we explored the worldwide security of medical image archives. MATERIALS AND METHODS. Using the DICOM data-transmitting standard, we implemented a highly parallel application to scan the entire World Wide Web of networked computers and devices, locating open and unprotected Radiology servers. We used only legal and Radiology-compliant tools. Our security-probing application initiated a standard DICOM handshake to remote computer or device addresses, and then assessed their security posture on the basis of handshake replies. RESULTS. The scan discovered a total of 2774 unprotected Radiology or DICOM servers worldwide. Of those, 719 were fully open to patient data communications. Geolocation was used to analyze and rank our findings according to country utilization. As a result, we buil...