The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
S Mutic - One of the best experts on this subject based on the ideXlab platform.
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first clinical implementation of real time real anatomy tracking and Radiation Beam control
Medical Physics, 2018Co-Authors: O L Green, L Rankine, Bin Cai, A Curcuru, R Kashani, V Rodriguez, P Parikh, Clifford G Robinson, J R Olsen, S MuticAbstract:Purpose We describe the acceptance testing, commissioning, periodic quality assurance, and workflow procedures developed for the first clinically implemented magnetic resonance imaging-guided Radiation therapy (MR-IGRT) system for real-time tracking and Beam control. Methods The system utilizes real-time cine imaging capabilities at 4 frames per second for real-time tracking and Beam control. Testing of the system was performed using an in-house developed motion platform and a commercially available motion phantom. Anatomical tracking is performed by first identifying a target (a region of interest that is either tissue to be treated or a critical structure) and generating a contour around it. A boundary contour is also created to identify tracking margins. The tracking algorithm deforms the anatomical contour (target or a normal organ) on every subsequent cine frame and compares it to the static boundary contour. If the anatomy of interest moves outside the boundary, the Radiation delivery is halted until the tracked anatomy returns to treatment portal. The following were performed to validate and clinically implement the system: (a) spatial integrity evaluation; (b) tracking accuracy; (c) latency; (d) relative point dose and spatial dosimetry; (e) development of clinical workflow for gating; and (f) independent verification by an outside credentialing service. Results The spatial integrity of the MR system was found to be within 2 mm over a 45-cm diameter field-of-view. The tracking accuracy for geometric targets was within 1.2 mm. The average system latency was measured to be within 394 ms. The dosimetric accuracy using ionization chambers was within 1.3% ± 1.7%, and the dosimetric spatial accuracy was within 2 mm. The phantom irRadiation for the outside credentialing service had satisfactory results, as well. Conclusions The first clinical MR-IGRT system was validated for real-time tracking and gating capabilities and shown to be reliable and accurate. Patient workflow methods were developed for efficient treatment. Periodic quality assurance tests can be efficiently performed with commercially available equipment to ensure accurate system performance.
Ching-chang Tsai - One of the best experts on this subject based on the ideXlab platform.
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SU‐E‐I‐40: Survey of Radiation Beam Width in CT According to ACR 2012 CT QC Manual
Medical Physics, 2013Co-Authors: Yu-tsun Lin, Yih-shiou Hwang, H.-p. Liu, Y Wang, Ching-chang TsaiAbstract:Purpose: To survey CT Radiation Beam width using in clinical protocols according to America College of Radiology (ACR) 2012 CT Quality Control Manual. We assessed the relationship between nominal collimated and Radiation Beam width. Methods: Radiation Beam width was measured using a self‐developed film (GAFCHROMIC XR CT2) for 346 CT scanners. The film was placed at the isocenter of CT scanner. Nominal collimated Beam widths (N×T) using for clinical examinations of routine adult head, adult abdomen, and 5‐years pediatric abdomen were measured. Results: The performance criteria set by ACR 2012 CT Quality Control Manual are that the measured Radiation Beam width should be accurate to within 3 mm or 30% of the nominal collimated Beam width (NxT), whichever is less. According to our survey, the fail rates were 18.8% for adult head examinations, 15.0% for adult abdomen examinations 20.1% for 5‐years pediatric abdomen examinations. If the criteria were set to within 3 mm or 30% whichever is greater, the fail rates dropped to 8.2%, 0.6%, and 2.0%, respectively. Toshiba CT scanners have to pay more attention to meet ACR criteria because the fail rate was from 39% to 75%. Conclusion: This survey gave a view of relationship of nominal and Radiation Beam width in different protocols and manufacturers. About twenty percent of CT scanners cannot pass the ACR criteria of Radiation Beam width.
R Tosh - One of the best experts on this subject based on the ideXlab platform.
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Time-resolved Radiation Beam profiles in water obtained by ultrasonic tomography
Metrologia, 2010Co-Authors: Eugene V. Malyarenko, Joseph S. Heyman, H. Heather Chen-mayer, R ToshAbstract:This paper presents a practical ultrasonic system for near real-time imaging of spatial temperature distributions in water caused by absorption of Radiation. Initial testing with Radiation from a highly attenuated infrared lamp demonstrates that the system is able to map sub-millikelvin temperature changes, thus making it suitable for characterizing dose profiles of therapy-level ionizing Radiation Beams. The system uses a fan-Beam tomographic reconstruction algorithm to invert time-of-flight data derived from ultrasonic pulses produced and detected by a circular array of transducers immersed in water. Temperature dependence of the speed of sound in water permits the conversion of these measured two-dimensional velocity distributions into temperature distributions that indicate the absorbed Radiation dose. The laboratory prototype, based on a 128-element transducer array, is used to acquire temperature maps of a 230 mm × 230 mm area every 4 s with sub-millikelvin resolution in temperature and about 5 mm resolution in space. Earlier measurements with a single-channel version of this prototype suggest refinements in signal-conditioning electronics and signal-processing algorithms that would allow the present instrument to resolve temperature changes as low as a few microkelvin. Possible applications include real-time intensity profiling of Radiation Beams and three-dimensional characterization of the absorbed dose.
Housei Akazawa - One of the best experts on this subject based on the ideXlab platform.
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Threshold behavior in synchrotron-Radiation-stimulated recrystallization during Si homoepitaxy on Si(100)
Applied Physics Letters, 1997Co-Authors: Housei AkazawaAbstract:A brilliant synchrotron-Radiation Beam with a large irRadiation area has made it possible to use spectroscopic phase-modulated ellipsometry to monitor vacuum-ultraviolet-excited Si homoepitaxy. We find the crystallinity of Si films grown at 250 °C from Si2H6 depends strongly on the photon intensity. When the photon intensity is higher than a critical value, electronically excited crystallization yields epitaxial Si. At lower intensities, however, the initial epitaxy is terminated halfway by island-shaped regions of polycrystalline Si, which are eventually covered by a uniform nanocrystalline Si overlayer.
Alexander V. Vinogradov - One of the best experts on this subject based on the ideXlab platform.
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Whispering gallery mirrors for soft x-ray region: properties and applications
X-Ray Optics and Surface Science, 1995Co-Authors: Inna Bukreeva, Igor V. Kozhevnikov, Alexander V. VinogradovAbstract:Basic properties of whispering gallery mirrors in soft X-ray region are considered. The following applications of whispering gallery optics are discussed: increasing of utilization efficiency of point source Radiation, deflection of synchrotron Radiation Beam to vertical plane and its transportation to another horizontal level, resonators for soft X-ray lasers and the use of whispering gallery effect for investigation of roughness of concave surfaces.
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Whispering gallery mirrors for the soft x-ray region: properties and applications.
Journal of X-ray science and technology, 1995Co-Authors: Inna Bukreeva, Igor V. Kozhevnikov, Alexander V. VinogradovAbstract:Basic properties of whispering gallery mirrors in the soft x-ray region are considered. The following applications of whispering gallery optics are discussed: increasing the utilization efficiency of point source Radiation, deflecting a synchrotron Radiation Beam to the vertical plane and transporting it to another horizontal level, resonators for soft x-ray lasers, and using the whispering gallery effect to investigate the roughness of concave surfaces.
