The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
R L Tanner - One of the best experts on this subject based on the ideXlab platform.
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Slit camera Focal Spot measurement errors in mammography.
Medical physics, 1995Co-Authors: S Tang, G T Barnes, R L TannerAbstract:Mammography x-ray tube Focal Spot sizes are routinely measured during acceptance testing and annual performance audits. The National Electrical Manufactures Association (NEMA) recommends the slit camera for this purpose. Investigated were the effect of slit rotational misalignment, tilt misalignment, image film density, film and screen-film image receptors, microscope magnification and reticule accuracy, and observer variation on slit camera Focal Spot measurements. Our results indicate that small rotational misalignment (< 5 degrees) and tilt misalignment (< 3 degrees) introduce insignificant error. Measured Focal Spot size increased slightly with image optical density, indicating that for consistent results the image optical density variations should be minimized. Also desirable for accurate field measurements is a high power microscope (25-50x) and a reticule with divisions of < or = 0.02 mm. Screen-film imaging consistently resulted in a slightly smaller measured Focal Spot size than direct film. The greatest source of error was due to observer variation. Of interest is that reader variability showed a consistent pattern and variation between two measurements by the same observer was much smaller than between observer variation, suggesting that standardized criteria should be established and a method of reader training developed. The length of the Focal Spot is defined at a reference axis angle specified by the mammography unit manufacturer. Presented is a tabulation of the Focal Spot geometry and reference axis angles for the majority of mammography units currently and recently marketed in North America.
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Slit camera Focal Spot measurement errors in mammography.
Medical Physics, 1995Co-Authors: S Tang, G T Barnes, R L TannerAbstract:Mammography x‐ray tube Focal Spot sizes are routinely measured during acceptance testing and annual performance audits. The National Electrical Manufacturers Association (NEMA) recommends the slit camera for this purpose. Investigated were the effect of slit rotational misalignment, tilt misalignment, image film density, film and screen‐film image receptors, microscope magnification and reticule accuracy, and observer variation on slit camera Focal Spot measurements. Our results indicate that small rotational misalignment (
S Tang - One of the best experts on this subject based on the ideXlab platform.
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Slit camera Focal Spot measurement errors in mammography.
Medical physics, 1995Co-Authors: S Tang, G T Barnes, R L TannerAbstract:Mammography x-ray tube Focal Spot sizes are routinely measured during acceptance testing and annual performance audits. The National Electrical Manufactures Association (NEMA) recommends the slit camera for this purpose. Investigated were the effect of slit rotational misalignment, tilt misalignment, image film density, film and screen-film image receptors, microscope magnification and reticule accuracy, and observer variation on slit camera Focal Spot measurements. Our results indicate that small rotational misalignment (< 5 degrees) and tilt misalignment (< 3 degrees) introduce insignificant error. Measured Focal Spot size increased slightly with image optical density, indicating that for consistent results the image optical density variations should be minimized. Also desirable for accurate field measurements is a high power microscope (25-50x) and a reticule with divisions of < or = 0.02 mm. Screen-film imaging consistently resulted in a slightly smaller measured Focal Spot size than direct film. The greatest source of error was due to observer variation. Of interest is that reader variability showed a consistent pattern and variation between two measurements by the same observer was much smaller than between observer variation, suggesting that standardized criteria should be established and a method of reader training developed. The length of the Focal Spot is defined at a reference axis angle specified by the mammography unit manufacturer. Presented is a tabulation of the Focal Spot geometry and reference axis angles for the majority of mammography units currently and recently marketed in North America.
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Slit camera Focal Spot measurement errors in mammography.
Medical Physics, 1995Co-Authors: S Tang, G T Barnes, R L TannerAbstract:Mammography x‐ray tube Focal Spot sizes are routinely measured during acceptance testing and annual performance audits. The National Electrical Manufacturers Association (NEMA) recommends the slit camera for this purpose. Investigated were the effect of slit rotational misalignment, tilt misalignment, image film density, film and screen‐film image receptors, microscope magnification and reticule accuracy, and observer variation on slit camera Focal Spot measurements. Our results indicate that small rotational misalignment (
Minh Huynh - One of the best experts on this subject based on the ideXlab platform.
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Efficacy of fine Focal Spot technique in CT angiography of neck.
The British journal of radiology, 2019Co-Authors: Kenneth K. Lau, Ashwini Devapalasundaram, Kevin Buchan, Ahilan Kuganesan, Minh HuynhAbstract:Objectives: Focal Spot size partially defines spatial resolution of a CT system. Many CT tubes have two Focal Spot sizes, with the finer one allowing more detailed imaging at the cost of photon int...
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Efficacy of ‘fine’ Focal Spot imaging in CT abdominal angiography
European Radiology, 2014Co-Authors: Kenneth K. Lau, Ashwini Devapalasundaram, Kevin Buchan, Nicholas Ardley, Minh HuynhAbstract:Objectives To assess the efficacy of fine Focal Spot imaging in calcification beam-hardening artefact reduction and vessel clarity on CT abdominal angiography (CTAA). Methods Adult patients of any age and gender who presented for CTAA were included. Thirty-nine patients were examined with a standard Focal Spot size (SFSS) of 1 × 1 mm in the first 3 months while 31 consecutive patients were examined with a fine Focal Spot size (FFSS) of 1 × 0.5 mm in the following 3 months. Vessel clarity and calcification beam-hardening artefacts of the abdominal aorta, celiac axis, superior mesenteric artery, inferior mesenteric artery, renal arteries, and iliac arteries were assessed using a 5-point grading scale by two blinded radiologists randomly. Results Cohen’s Kappa test indicated that on average, there was substantial agreement among reviewers for vessel wall clarity and calcification artefact grading. Mann-Whitney test showed that there was a significant difference between the two groups, with FFSS performing significantly better for vessel clarity ( U, 6481.50; p
Frank Verhaegen - One of the best experts on this subject based on the ideXlab platform.
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Modelling of the Focal Spot intensity distribution and the off-Focal Spot radiation in kilovoltage x-ray tubes for imaging.
Physics in medicine and biology, 2020Co-Authors: Brent Van Der Heyden, Gabriel P. Fonseca, Mark Podesta, Ivan Messner, Niklas Reisz, Ana Vaniqui, Heinz Deutschmann, Phil Steininger, Frank VerhaegenAbstract:X-ray tubes for medical applications typically generate x-rays by accelerating electrons, emitted from a cathode, with an interelectrode electric field, towards an anode target. X-rays are not emitted from one point, but from an irregularly shaped area on the anode, the Focal Spot. Focal Spot intensity distributions and off-Focal radiation negatively affect the imaging spatial resolution and broadens the beam penumbra. In this study, a Monte Carlo simulation model of an x-ray tube was developed to evaluate the spectral and spatial characteristics of off-Focal radiation for multiple photon energies. Slit camera measurements were used to determine the horizontal and vertical intensity profiles of the small and the large Focal Spot of a diagnostic x-ray tube. First, electron beamlet weighting factors were obtained via an iterative optimization method to represent both Focal Spot sizes. These weighting factors were then used to extract off-Focal Spot radiation characteristics for the small and large Focal Spot sizes at 80, 100, and 120 kV. Finally, 120 kV simulations of a steel sphere (d = 4 mm) were performed to investigate image blurring with a point source, the small Focal Spot, and the large Focal Spot. The magnitude of off-Focal radiation strongly depends on the anode size and the electric field coverage, and only minimally on the tube potential and the primary Focal Spot size. In conclusion, an x-ray tube Monte Carlo simulation model was developed to simulate Focal Spot intensity distributions and to evaluate off-Focal radiation characteristics at several energies. This model can be further employed to investigate Focal Spot correction methods and to improve cone-beam CT image quality.
G T Barnes - One of the best experts on this subject based on the ideXlab platform.
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Slit camera Focal Spot measurement errors in mammography.
Medical physics, 1995Co-Authors: S Tang, G T Barnes, R L TannerAbstract:Mammography x-ray tube Focal Spot sizes are routinely measured during acceptance testing and annual performance audits. The National Electrical Manufactures Association (NEMA) recommends the slit camera for this purpose. Investigated were the effect of slit rotational misalignment, tilt misalignment, image film density, film and screen-film image receptors, microscope magnification and reticule accuracy, and observer variation on slit camera Focal Spot measurements. Our results indicate that small rotational misalignment (< 5 degrees) and tilt misalignment (< 3 degrees) introduce insignificant error. Measured Focal Spot size increased slightly with image optical density, indicating that for consistent results the image optical density variations should be minimized. Also desirable for accurate field measurements is a high power microscope (25-50x) and a reticule with divisions of < or = 0.02 mm. Screen-film imaging consistently resulted in a slightly smaller measured Focal Spot size than direct film. The greatest source of error was due to observer variation. Of interest is that reader variability showed a consistent pattern and variation between two measurements by the same observer was much smaller than between observer variation, suggesting that standardized criteria should be established and a method of reader training developed. The length of the Focal Spot is defined at a reference axis angle specified by the mammography unit manufacturer. Presented is a tabulation of the Focal Spot geometry and reference axis angles for the majority of mammography units currently and recently marketed in North America.
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Slit camera Focal Spot measurement errors in mammography.
Medical Physics, 1995Co-Authors: S Tang, G T Barnes, R L TannerAbstract:Mammography x‐ray tube Focal Spot sizes are routinely measured during acceptance testing and annual performance audits. The National Electrical Manufacturers Association (NEMA) recommends the slit camera for this purpose. Investigated were the effect of slit rotational misalignment, tilt misalignment, image film density, film and screen‐film image receptors, microscope magnification and reticule accuracy, and observer variation on slit camera Focal Spot measurements. Our results indicate that small rotational misalignment (
