The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Bob Liu - One of the best experts on this subject based on the ideXlab platform.
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Scatter Radiation intensities around a clinical digital breast tomosynthesis unit and the impact on Radiation shielding considerations.
Medical physics, 2016Co-Authors: Kai Yang, Bob LiuAbstract:Purpose: To measure the Scattered Radiation intensity around a clinical digital breast tomosynthesis (DBT) unit and to provide updated data for Radiation shielding design for DBT systems with tungsten-anode x-ray tubes. Methods: The continuous distribution of Scattered x-rays from a clinical DBT system (Hologic Selenia Dimensions) was measured within an angular range of 0°–180° using a linear-array x-ray detector (X-Scan 0.8f3-512, Detection Technology, Inc., Finland), which was calibrated for the x-ray spectrum range of the DBT unit. The effects of x-ray field size, phantom size, and x-ray kVp/filter combination were investigated. Following a previously developed methodology by Simpkin, Scatter fraction was determined for the DBT system as a function of angle around the phantom center. Detailed calculations of the Scatter intensity from a DBT system were demonstrated using the measured Scatter fraction data. Results: For the 30 and 35 kVp acquisition, the Scatter-to-primary-ratio and Scatter fraction data closely matched with data previously measured by Simpkin. However, the measured data from this study demonstrated the nonisotropic distribution of the Scattered Radiation around a DBT system, with two strong peaks around 25° and 160°. The majority Scatter Radiation (>70%) originated from the imaging detector assembly, instead of the phantom. With a workload from a previous survey performed at MGH, the Scatter air kerma at 1 m from the phantom center for wall/door is 1.76 × 10−2 mGy patient−1, for floor is 1.64 × 10−1 mGy patient−1, and for ceiling is 3.66 × 10−2 mGy patient−1. Conclusions: Comparing to previously measured data for mammographic systems, the Scatter air kerma from Holgoic DBT is at least two times higher. The main reasons include the harder primary beam with higher workload (measured with total mAs/week), added tomosynthesis acquisition, and strong small angle forward Scattering. Due to the highly conservative initial assumptions, the shielding recommendation from NCRP Report 147 is still sufficient for the Hologic DBT system given the workload from a previous survey at MGH. With the data provided from this study, accurate shielding calculation can be performed for Hologic DBT systems with specific workload and barrier distance.
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Novel Lead-Free Drape Applied to the X-Ray Detector Protects against Scatter Radiation in the Angiography Suite
Journal of vascular and interventional radiology : JVIR, 2014Co-Authors: Zubin Irani, Bailin Alexander, Da Zhang, Bob Liu, Brian B. Ghoshhajra, Rahmi OkluAbstract:Abstract Purpose To evaluate a sterile, disposable lead-free drape for reducing Scatter Radiation exposure during fluoroscopy-guided procedures. Materials and Methods Computer-aided design software was used to model a procedure room with a thoracic anthropomorphic phantom on the angiography table. Using this model, measurements of Scatter Radiation were made from the phantom before and after the application of the drape using a collimated and full field of view in low-output conditions (70 kVp, 48 mA) and high-output conditions (125 kVp, 156 mA). Transmission of x-rays through the drape and entrance exposure rates were also measured. Statistical significance was measured using a Student t test. Results Scatter Radiation was attenuated throughout the procedure room when the drape was applied. The highest level of Scatter Radiation was detected in the expected position of the operator, adjacent to the phantom. Radioprotection by the drape was the greatest in this position: 71.5% attenuation at waist level and 89% at neck level ( P Conclusions The use of this drape significantly reduces Scatter Radiation in the procedure room; this effect is maximal in close proximity to the phantom.
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Effects of Scatter Radiation on reconstructed images in digital breast tomosynthesis
Medical Imaging 2009: Physics of Medical Imaging, 2009Co-Authors: Bob LiuAbstract:We evaluated the effects of Scatter Radiation on the reconstructed images in digital breast tomosynthesis. Projection images of a 6 cm anthropomorphic breast phantom were acquired using a Hologic prototype digital breast tomosynthesis system. Scatter intensities in projection images were sampled with a beam stop method. The Scatter intensity at any pixel was obtained by two dimensional fitting. Primary-only projection images were generated by subtracting the Scatter contributions from the original projection images. The 3-dimensional breast was reconstructed first based on original projection images which contained the contributions from both primary rays and Scattered Radiation using three different reconstruction algorithms. The same breast volume was reconstructed again using the same algorithms but based on primaryonly projection images. The image artifacts, pixel value difference to noise ratio (PDNR), and detected image features in these two sets of reconstructed slices were compared to evaluate the effects of Scatter Radiation. It was found that the Scatter Radiation caused inaccurate reconstruction of the x-ray attenuation property of the tissue. X-ray attenuation coefficients could be significantly underestimated in the region where Scatter intensity is high. This phenomenon is similar to the cupping artifacts found in computed tomography. The Scatter correction is important if accurate x-ray attenuation of the tissues is needed. No significant improvement in terms of numbers of detected image features was observed after Scatter correction. More sophisticated phantom dedicated to digital breast tomosynthesis may be needed for further evaluation.
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tu ee a3 05 Scatter Radiation in digital tomosynthesis
Medical Physics, 2005Co-Authors: Bob Liu, Stephen J. Glick, Xing GongAbstract:Purpose: To investigate the characteristics of Scattered Radiation and its effects on image quality in digital breast tomosynthesis. Method and Materials: A GEANT 4 based Monte Carlo package was used to simulate a rotating target/detector tomosynthesis system. The compressed breast was modeled as a cubic block imbedded with 24 small cylinders of different radii and heights in the central layer. An 11cm air gap between the breast and detector was modeled. The incident photon energy was set to 20 keV to avoid the complexity of beam hardening effects. A primary image and a Scatter image were generated for each projection. The gantry was rotated around the breast from −25 degree to 25 degree with a 5 degree increment. Reconstructions of the 3D breast were computed from the 11 projection images using primary x-rays only, and primary plus Scattered x-rays. Results: The magnitude of Scatter Radiation does not change very much from one projection to another because the Scatter volume does not change. However, the primary Radiation detected can be significantly different in different projections due to different path length. As a result, Scatter to primary ratio is very different for different projection. Even with the 11 cm air gap, Scatter to primary ratio was observed to be as high as 0.4 for a 5 cm thick breast. 3D breast images reconstructed from projections with only primary x-rays showed higher contrast than those reconstructed from projections with both primary and Scatter. Further evaluation is needed to determine if this reduced contrast can affect tumor detectability. Conclusion: Scatter to primary ratio changed significantly from one projection to another and was observed to be as high as 0.4 for a 5 cm thick breast. Tomosynthesis slices showed a moderate decrease in contrast due to Scatter.
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TU‐EE‐A3‐05: Scatter Radiation in Digital Tomosynthesis
Medical Physics, 2005Co-Authors: Bob Liu, Stephen J. Glick, Xing GongAbstract:Purpose: To investigate the characteristics of Scattered Radiation and its effects on image quality in digital breast tomosynthesis. Method and Materials: A GEANT 4 based Monte Carlo package was used to simulate a rotating target/detector tomosynthesis system. The compressed breast was modeled as a cubic block imbedded with 24 small cylinders of different radii and heights in the central layer. An 11cm air gap between the breast and detector was modeled. The incident photon energy was set to 20 keV to avoid the complexity of beam hardening effects. A primary image and a Scatter image were generated for each projection. The gantry was rotated around the breast from −25 degree to 25 degree with a 5 degree increment. Reconstructions of the 3D breast were computed from the 11 projection images using primary x-rays only, and primary plus Scattered x-rays. Results: The magnitude of Scatter Radiation does not change very much from one projection to another because the Scatter volume does not change. However, the primary Radiation detected can be significantly different in different projections due to different path length. As a result, Scatter to primary ratio is very different for different projection. Even with the 11 cm air gap, Scatter to primary ratio was observed to be as high as 0.4 for a 5 cm thick breast. 3D breast images reconstructed from projections with only primary x-rays showed higher contrast than those reconstructed from projections with both primary and Scatter. Further evaluation is needed to determine if this reduced contrast can affect tumor detectability. Conclusion: Scatter to primary ratio changed significantly from one projection to another and was observed to be as high as 0.4 for a 5 cm thick breast. Tomosynthesis slices showed a moderate decrease in contrast due to Scatter.
Xing Gong - One of the best experts on this subject based on the ideXlab platform.
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tu ee a3 05 Scatter Radiation in digital tomosynthesis
Medical Physics, 2005Co-Authors: Bob Liu, Stephen J. Glick, Xing GongAbstract:Purpose: To investigate the characteristics of Scattered Radiation and its effects on image quality in digital breast tomosynthesis. Method and Materials: A GEANT 4 based Monte Carlo package was used to simulate a rotating target/detector tomosynthesis system. The compressed breast was modeled as a cubic block imbedded with 24 small cylinders of different radii and heights in the central layer. An 11cm air gap between the breast and detector was modeled. The incident photon energy was set to 20 keV to avoid the complexity of beam hardening effects. A primary image and a Scatter image were generated for each projection. The gantry was rotated around the breast from −25 degree to 25 degree with a 5 degree increment. Reconstructions of the 3D breast were computed from the 11 projection images using primary x-rays only, and primary plus Scattered x-rays. Results: The magnitude of Scatter Radiation does not change very much from one projection to another because the Scatter volume does not change. However, the primary Radiation detected can be significantly different in different projections due to different path length. As a result, Scatter to primary ratio is very different for different projection. Even with the 11 cm air gap, Scatter to primary ratio was observed to be as high as 0.4 for a 5 cm thick breast. 3D breast images reconstructed from projections with only primary x-rays showed higher contrast than those reconstructed from projections with both primary and Scatter. Further evaluation is needed to determine if this reduced contrast can affect tumor detectability. Conclusion: Scatter to primary ratio changed significantly from one projection to another and was observed to be as high as 0.4 for a 5 cm thick breast. Tomosynthesis slices showed a moderate decrease in contrast due to Scatter.
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TU‐EE‐A3‐05: Scatter Radiation in Digital Tomosynthesis
Medical Physics, 2005Co-Authors: Bob Liu, Stephen J. Glick, Xing GongAbstract:Purpose: To investigate the characteristics of Scattered Radiation and its effects on image quality in digital breast tomosynthesis. Method and Materials: A GEANT 4 based Monte Carlo package was used to simulate a rotating target/detector tomosynthesis system. The compressed breast was modeled as a cubic block imbedded with 24 small cylinders of different radii and heights in the central layer. An 11cm air gap between the breast and detector was modeled. The incident photon energy was set to 20 keV to avoid the complexity of beam hardening effects. A primary image and a Scatter image were generated for each projection. The gantry was rotated around the breast from −25 degree to 25 degree with a 5 degree increment. Reconstructions of the 3D breast were computed from the 11 projection images using primary x-rays only, and primary plus Scattered x-rays. Results: The magnitude of Scatter Radiation does not change very much from one projection to another because the Scatter volume does not change. However, the primary Radiation detected can be significantly different in different projections due to different path length. As a result, Scatter to primary ratio is very different for different projection. Even with the 11 cm air gap, Scatter to primary ratio was observed to be as high as 0.4 for a 5 cm thick breast. 3D breast images reconstructed from projections with only primary x-rays showed higher contrast than those reconstructed from projections with both primary and Scatter. Further evaluation is needed to determine if this reduced contrast can affect tumor detectability. Conclusion: Scatter to primary ratio changed significantly from one projection to another and was observed to be as high as 0.4 for a 5 cm thick breast. Tomosynthesis slices showed a moderate decrease in contrast due to Scatter.
Walter Heindel - One of the best experts on this subject based on the ideXlab platform.
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detection of subtle undisplaced rib fractures in a porcine model Radiation dose requirement digital flat panel versus screen film and storage phosphor systems
Radiology, 2003Co-Authors: Karl F. Ludwig, Dag Wormanns, Thomas M. Bernhardt, Stefan Diederich, H Lenzen, Christoph Schulke, Paul Brinckmann, Walter HeindelAbstract:PURPOSE: To compare a large-area direct read-out flat-panel detector radiography system with screen-film and storage-phosphor systems with regard to detection of subtle undisplaced rib fractures and to assess the diagnostic performance of the flat-panel system with decreasing exposure level. MATERIALS AND METHODS: Subtle fractures were created artificially in 100 of 200 porcine rib specimens. Specimens were enclosed in containers of water to generate absorption and Scatter Radiation conditions similar to those of a human chest wall. Imaging was performed with flat-panel, screen-film, and storage-phosphor systems with conditions that were exactly matched. Different exposure levels equivalent to speed classes (S) of 400, 800, 1,600, and 6,400 were used. All images were independently assessed for the presence of fracture by three radiologists with a five-level confidence scale. Receiver operating characteristic (ROC) analysis was performed for a total of 4,200 observations (600 for each imaging system and ex...
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performance of a flat panel detector in detecting artificial bone lesions comparison with conventional screen film and storage phosphor radiography
Radiology, 2002Co-Authors: Karl F. Ludwig, Dag Wormanns, Stefan Diederich, H Lenzen, Karlfriedrich Kamm, Thomas M Link, Walter HeindelAbstract:PURPOSE: To compare a large-area direct-readout flat-panel detector system with a conventional screen-film system and a storage-phosphor system in detecting small artificial osseous lesions simulating osteolytic disease and to assess diagnostic performance with decreasing exposure dose. MATERIALS AND METHODS: Artificial lesions (0.5–3.0 mm) were created in 100 of 200 predefined regions in 20 porcine femoral specimens. Specimens were enclosed in containers filled with water to create absorption and Scatter Radiation conditions comparable with those in a human extremity. Imaging was performed with a flat-panel detector system, a conventional screen-film system, and a storage-phosphor system. Levels of exposure equivalent to speed classes 400, 800, 1600, and 3200 were used. In all images, the presence or absence of a lesion was assessed by three radiologists using a five-point confidence scale. Receiver operating characteristic (ROC) analysis was performed for 4,800 observations (600 for each imaging modalit...
Karl F. Ludwig - One of the best experts on this subject based on the ideXlab platform.
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detection of subtle undisplaced rib fractures in a porcine model Radiation dose requirement digital flat panel versus screen film and storage phosphor systems
Radiology, 2003Co-Authors: Karl F. Ludwig, Dag Wormanns, Thomas M. Bernhardt, Stefan Diederich, H Lenzen, Christoph Schulke, Paul Brinckmann, Walter HeindelAbstract:PURPOSE: To compare a large-area direct read-out flat-panel detector radiography system with screen-film and storage-phosphor systems with regard to detection of subtle undisplaced rib fractures and to assess the diagnostic performance of the flat-panel system with decreasing exposure level. MATERIALS AND METHODS: Subtle fractures were created artificially in 100 of 200 porcine rib specimens. Specimens were enclosed in containers of water to generate absorption and Scatter Radiation conditions similar to those of a human chest wall. Imaging was performed with flat-panel, screen-film, and storage-phosphor systems with conditions that were exactly matched. Different exposure levels equivalent to speed classes (S) of 400, 800, 1,600, and 6,400 were used. All images were independently assessed for the presence of fracture by three radiologists with a five-level confidence scale. Receiver operating characteristic (ROC) analysis was performed for a total of 4,200 observations (600 for each imaging system and ex...
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performance of a flat panel detector in detecting artificial bone lesions comparison with conventional screen film and storage phosphor radiography
Radiology, 2002Co-Authors: Karl F. Ludwig, Dag Wormanns, Stefan Diederich, H Lenzen, Karlfriedrich Kamm, Thomas M Link, Walter HeindelAbstract:PURPOSE: To compare a large-area direct-readout flat-panel detector system with a conventional screen-film system and a storage-phosphor system in detecting small artificial osseous lesions simulating osteolytic disease and to assess diagnostic performance with decreasing exposure dose. MATERIALS AND METHODS: Artificial lesions (0.5–3.0 mm) were created in 100 of 200 predefined regions in 20 porcine femoral specimens. Specimens were enclosed in containers filled with water to create absorption and Scatter Radiation conditions comparable with those in a human extremity. Imaging was performed with a flat-panel detector system, a conventional screen-film system, and a storage-phosphor system. Levels of exposure equivalent to speed classes 400, 800, 1600, and 3200 were used. In all images, the presence or absence of a lesion was assessed by three radiologists using a five-point confidence scale. Receiver operating characteristic (ROC) analysis was performed for 4,800 observations (600 for each imaging modalit...
Ya M Amusia - One of the best experts on this subject based on the ideXlab platform.
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viscous motion of spherical nanoparticles that Scatter laser Radiation in the rayleigh regime
Jetp Letters, 2020Co-Authors: Ya M Amusia, A S BaltenkovAbstract:The mechanism of transverse Radiation viscosity for nanospheres moving in a laser field is analyzed. It is demonstrated that in the process of light Scattering by these particles besides the force Fs accelerating them in the direction of Radiation propagation and the gradient force Fg that is due to the spatial inhomogeneity of the light field, there are forces Fvisc that slow down the motion of particles in the transverse directions. These light viscosity forces are due to the Doppler shift in frequency of Scattered Radiation. The general expressions for these forces acting on particles that Scatter Radiation in the Rayleigh regime are derived and applied to estimate their effect on levitated nanospheres and on slow electrons moving in the laser and magnetic fields. The possible experiments for observation of the effects of light viscosity are discussed.
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viscous motion of spherical nanoparticles that Scatter laser Radiation in the rayleigh regime
arXiv: Atomic and Molecular Clusters, 2020Co-Authors: Ya M Amusia, A S BaltenkovAbstract:The mechanism of transverse Radiation viscosity for nanospheres moving in laser field is analyzed. It is demonstrated that in the process of light Scattering by these particles besides the force Fs accelerating them in the direction of Radiation propagation and the gradient force Fg that is due to the spatial inhomogeneity of the light field, there are forces Fvisc that slow down the movement of particles in the transverse directions. These light viscosity forces are due to the Doppler shift in frequency of Scattered Radiation. The general expressions for these forces acting on particles that Scatter Radiation in the Rayleigh regime are derived and applied to estimate their effect on levitated nanospheres and also on slow electrons moving in the laser and magnetic fields. The possible experiments for observation the effects of light viscosity is discussed.
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Viscous motion of spherical nanoparticles that Scatter laser Radiation in the Rayleigh regime
'Pleiades Publishing Ltd', 2020Co-Authors: Ya M Amusia, Baltenkov A. S.Abstract:The mechanism of transverse Radiation viscosity for nanospheres moving in laser field is analyzed. It is demonstrated that in the process of light Scattering by these particles besides the force Fs accelerating them in the direction of Radiation propagation and the gradient force Fg that is due to the spatial inhomogeneity of the light field, there are forces Fvisc that slow down the movement of particles in the transverse directions. These light viscosity forces are due to the Doppler shift in frequency of Scattered Radiation. The general expressions for these forces acting on particles that Scatter Radiation in the Rayleigh regime are derived and applied to estimate their effect on levitated nanospheres and also on slow electrons moving in the laser and magnetic fields. The possible experiments for observation the effects of light viscosity is discussed.Comment: 7 pages, 1 figur
