The Experts below are selected from a list of 849 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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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.
Michael H Baumann - One of the best experts on this subject based on the ideXlab platform.
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portal verification of high energy electron beams using their photon contamination by Film Cassette systems
Strahlentherapie Und Onkologie, 2006Co-Authors: Peter Geyer, Wolfgang W Baus, Michael H BaumannAbstract:Though electron beams are widely used in radiotherapy, their verification is not well established in clinical practice. The present study compares the suitability of several sensitive Film-Cassette systems for electron-portal verification by contaminating photons. The characteristics of the optical density curves of Film-Cassette combinations were determined by exposing them to the bremsstrahlung contamination of a variety of electron beams. Using a Las-Vegas Phantom the spatial low-contrast resolution of the combinations was investigated. The absorbed dose rates due to the contaminant photons were measured for different geometric conditions. Suitable Film-Cassette combinations were found for portal verification of all usual electron energies. The best image quality was obtained using the EC® Film and the EC-L® Cassettes (Eastman Kodak Comp., Rochester, NY, USA). For electron energies higher than 6 MeV some Film-Cassette combinations are suitable to verify abutted electron and photon portals using the same Film sheet. The verification of electron portals and of abutted electron-photon portals can be performed by sensitive Film-Cassette systems with an image quality comparable to photon-beam verification.
Wei Zhao - One of the best experts on this subject based on the ideXlab platform.
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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.
R. Lepková - One of the best experts on this subject based on the ideXlab platform.
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Personnel Exposure to Scattered Radiation During Radiography of the Distal Interphalangeal Joint in the Horse Using a Portable X-Ray Machine
University of Veterinary and Pharmaceutical Sciences Brno, 2007Co-Authors: J. Šterc, R. LepkováAbstract:Radiography of the distal interphalangeal joints of two limbs of a cadaver of a horse weighing 550 kg was conducted in the present study. The examination was performed on lateromedial, palmaroproximal-palmarodistal views and on dorsoproximal-palmarodistal, dorsolateral-palmaromedial, dorsomedial-palmarolateral views of a raised limb placed on a navicular block, and of weight-bearing limbs. During the examination, doses of scattered radiation were measured at the sites of radiographer, assistant holding a Film Cassette and assistant positioning the examined limb or the opposite one. The lowest radiation dose was received by the assistant holding the Cassette behind the examined region; a total equivalent dose of 183.6 - 201.7 nSv was received by his hands and genitals, and 110.8 - 113.3 nSv by his eye lens and neck during the examination of the distal interphalangeal joint. The radiographer was exposed to higher radiation; an equivalent dose of 846.6 - 854.1 nSv was received by his hands and genitals, and 271.8 - 328.2 nSv by the eye lens and the neck. The highest scattered radiation dose was received by the assistant positioning the examined limbs; equivalent doses were 7751 - 9354 nSv (hands), 1117.3 - 1119.5 nSv (genitals), and 880.6 - 1096.2 nSv (eye lens and neck). The equivalent dose values measured, received by the radiographer and the assistants during the examination of the distal interphalangeal joint seem to be very low relative to radiation exposure limits. However, it must be taken into account that the personnel involved in radiography is also exposed to scattered radiation during other examinations where radiation doses are often much higher. These results indicate the necessity to use protective lead aprons, gloves and collars during radiography of the distal interphalangeal joint
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Abstract ·terc J., R. Lepková: Personnel Exposure to Scattered Radiation during Radiography of the Distal Interphalangeal Joint in the Horse Using a Portable X-ray Machine. Acta Vet Brno 2007,
2006Co-Authors: R. LepkováAbstract:Radiography of the distal interphalangeal joints of two limbs of a cadaver of a horse weighing 550 kg was conducted in the present study. The examination was performed on lateromedial, palmaroproximal-palmarodistal views and on dorsoproximal-palmarodistal, dorsolateral-palmaromedial, dorsomedial-palmarolateral views of a raised limb placed on a navicular block, and of weight-bearing limbs. During the examination, doses of scattered radiation were measured at the sites of radiographer, assistant holding a Film Cassette and assistant positioning the examined limb or the opposite one. The lowest radiation dose was received by the assistant holding the Cassette behind the examined region; a total equivalent dose of 183.6- 201.7 nSv was received by his hands and genitals, and 110.8- 113.3 nSv by his eye lens and neck during the examination of the distal interphalangeal joint. The radiographer was exposed to higher radiation; an equivalent dose of 846.6- 854.1 nSv was received by his hands and genitals, and 271.8- 328.2 nSv by the eye lens and the neck. The highest scattered radiation dose was received by the assistant positioning the examined limbs; equivalent doses were 7751- 9354 nSv (hands), 1117.3- 1119.5 nSv (genitals), and 880.6- 1096.2 nSv (eye lens and neck). The equivalent dose values measured, received by the radiographer and the assistants during the examination of the distal interphalangea
Peter Geyer - One of the best experts on this subject based on the ideXlab platform.
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portal verification of high energy electron beams using their photon contamination by Film Cassette systems
Strahlentherapie Und Onkologie, 2006Co-Authors: Peter Geyer, Wolfgang W Baus, Michael H BaumannAbstract:Though electron beams are widely used in radiotherapy, their verification is not well established in clinical practice. The present study compares the suitability of several sensitive Film-Cassette systems for electron-portal verification by contaminating photons. The characteristics of the optical density curves of Film-Cassette combinations were determined by exposing them to the bremsstrahlung contamination of a variety of electron beams. Using a Las-Vegas Phantom the spatial low-contrast resolution of the combinations was investigated. The absorbed dose rates due to the contaminant photons were measured for different geometric conditions. Suitable Film-Cassette combinations were found for portal verification of all usual electron energies. The best image quality was obtained using the EC® Film and the EC-L® Cassettes (Eastman Kodak Comp., Rochester, NY, USA). For electron energies higher than 6 MeV some Film-Cassette combinations are suitable to verify abutted electron and photon portals using the same Film sheet. The verification of electron portals and of abutted electron-photon portals can be performed by sensitive Film-Cassette systems with an image quality comparable to photon-beam verification.