The Experts below are selected from a list of 6261 Experts worldwide ranked by ideXlab platform
George Coutrakon - One of the best experts on this subject based on the ideXlab platform.
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dose error analysis for a scanned proton Beam Delivery System
Physics in Medicine and Biology, 2010Co-Authors: George Coutrakon, Daniel W Miller, N Wang, Y YangAbstract:All particle Beam scanning Systems are subject to dose Delivery errors due to errors in position, energy and intensity of the delivered Beam. In addition, finite scan speeds, Beam spill non-uniformities, and delays in detector, detector electronics and magnet responses will all contribute errors in Delivery. In this paper, we present dose errors for an 8 × 10 × 8 cm(3) target of uniform water equivalent density with 8 cm spread out Bragg peak and a prescribed dose of 2 Gy. Lower doses are also analyzed and presented later in the paper. Beam energy errors and errors due to limitations of scanning System hardware have been included in the analysis. By using Gaussian shaped pencil Beams derived from measurements in the research room of the James M Slater Proton Treatment and Research Center at Loma Linda, CA and executing treatment simulations multiple times, statistical dose errors have been calculated in each 2.5 mm cubic voxel in the target. These errors were calculated by delivering multiple treatments to the same volume and calculating the rms variation in delivered dose at each voxel in the target. The variations in dose were the result of random Beam Delivery errors such as proton energy, spot position and intensity fluctuations. The results show that with reasonable assumptions of random Beam Delivery errors, the spot scanning technique yielded an rms dose error in each voxel less than 2% or 3% of the 2 Gy prescribed dose. These calculated errors are within acceptable clinical limits for radiation therapy.
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a prototype Beam Delivery System for the proton medical accelerator at loma linda
Medical Physics, 1991Co-Authors: George Coutrakon, M Bauman, David A Lesyna, Daniel W Miller, J Nusbaum, Jon W Slater, J Johanning, J Miranda, P M Deluca, J SiebersAbstract:A variable energy proton accelerator was commissioned at Fermi National Accelerator Laboratory for use in cancer treatment at the Loma Linda University Medical Center. The advantages of precise dose localization by proton therapy, while sparing nearby healthy tissue, are well documented [R. R. Wilson, Radiology 47, 487 (1946); M. Wagner, Med. Phys. 9, 749 (1982); M. Goitein and F. Chen, Med. Phys. 10, 831 (1983)]. One of the components of the proton therapy facility is a Beam Delivery System capable of delivering precise dose distributions to the target volume in the patient. To this end, a prototype Beam Delivery System was tested during the accelerator's commissioning period. The Beam Delivery System consisted of a Beam spreading device to produce a large, uniform field, a range modulator to generate a spread out Bragg peak (SOBP), and various Beam detectors to measure intensity, Beam centering, and dose distributions. The Beam Delivery System provided a uniform proton dose distribution in a cylindrical volume of 20-cm-diam area and 9-cm depth. The dose variations throughout the target volume were found to be less than +/- 5%. Modifications in the range modulator should reduce this considerably. The central axis dose rate in the region of the SOBP was found to be 0.4 cGy/spill with an incident Beam intensity of 6.7 x 10(9) protons/spill. With an accelerator repetition rate of 30 spills/min and expected intensity of 2.5 x 10(10) protons/spill for patient treatment, this System can provide 50 cGy/min for a 20-cm-diam field and 9-cm range modulation.(ABSTRACT TRUNCATED AT 250 WORDS)
James M. Fraser - One of the best experts on this subject based on the ideXlab platform.
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Real-time depth monitoring and control of laser machining through scanning Beam Delivery System
Journal of Physics D: Applied Physics, 2015Co-Authors: Alexander W Grindal, Paul J. L. Webster, James M. FraserAbstract:Scanning optics enable many laser applications in manufacturing because their low inertia allows rapid movement of the process Beam across the sample. We describe our method of inline coherent imaging for real-time (up to 230 kHz) micron-scale (7–8 µm axial resolution) tracking and control of laser machining depth through a scanning galvo-telecentric Beam Delivery System. For 1 cm trench etching in stainless steel, we collect high speed intrapulse and interpulse morphology which is useful for further understanding underlying mechanisms or comparison with numerical models. We also collect overall sweep-to-sweep depth penetration which can be used for feedback depth control. For trench etching in silicon, we show the relationship of etch rate with average power and scan speed by computer processing of depth information without destructive sample post-processing. We also achieve three-dimensional infrared continuous wave (modulated) laser machining of a 3.96 × 3.96 × 0.5 mm3 (length × width × maximum depth) pattern on steel with depth feedback. To the best of our knowledge, this is the first successful demonstration of direct real-time depth monitoring and control of laser machining with scanning optics.
Y Yang - One of the best experts on this subject based on the ideXlab platform.
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dose error analysis for a scanned proton Beam Delivery System
Physics in Medicine and Biology, 2010Co-Authors: George Coutrakon, Daniel W Miller, N Wang, Y YangAbstract:All particle Beam scanning Systems are subject to dose Delivery errors due to errors in position, energy and intensity of the delivered Beam. In addition, finite scan speeds, Beam spill non-uniformities, and delays in detector, detector electronics and magnet responses will all contribute errors in Delivery. In this paper, we present dose errors for an 8 × 10 × 8 cm(3) target of uniform water equivalent density with 8 cm spread out Bragg peak and a prescribed dose of 2 Gy. Lower doses are also analyzed and presented later in the paper. Beam energy errors and errors due to limitations of scanning System hardware have been included in the analysis. By using Gaussian shaped pencil Beams derived from measurements in the research room of the James M Slater Proton Treatment and Research Center at Loma Linda, CA and executing treatment simulations multiple times, statistical dose errors have been calculated in each 2.5 mm cubic voxel in the target. These errors were calculated by delivering multiple treatments to the same volume and calculating the rms variation in delivered dose at each voxel in the target. The variations in dose were the result of random Beam Delivery errors such as proton energy, spot position and intensity fluctuations. The results show that with reasonable assumptions of random Beam Delivery errors, the spot scanning technique yielded an rms dose error in each voxel less than 2% or 3% of the 2 Gy prescribed dose. These calculated errors are within acceptable clinical limits for radiation therapy.
S Agosteo - One of the best experts on this subject based on the ideXlab platform.
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secondary neutron and photon dose in proton therapy
Radiotherapy and Oncology, 1998Co-Authors: S Agosteo, C Birattari, Marcello Caravaggio, M Silari, Giampiero TosiAbstract:Abstract Background and purpose : The dose due to secondary neutrons and photons in proton therapy was estimated with Monte Carlo simulations. Three existing facilities treating eye and deep-seated tumours were taken into account. The results of the calculations related to eye proton therapy were verified with measurements. Materials and methods : The simulations were performed with the FLUKA code. Neutron fluence was measured inside an Alderson phantom (type ART) with activation techniques. Results : The maximum dose due to secondaries produced in a passive Beam Delivery System was estimated to be of the order of 10 −4 and 10 −2 Gy per therapy Gy for eye and deep tumour treatments, respectively. In the case of irradiations of deep-seated tumours carried out with an active System, the dose was of the order of 10 −3 Gy per therapy Gy. Conclusions : The dose due to secondaries depends on the geometry of the Beam Delivery System and on the energy of the primary Beam and is lower in the healthy tissues distant from the target volume.
Daniel W Miller - One of the best experts on this subject based on the ideXlab platform.
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dose error analysis for a scanned proton Beam Delivery System
Physics in Medicine and Biology, 2010Co-Authors: George Coutrakon, Daniel W Miller, N Wang, Y YangAbstract:All particle Beam scanning Systems are subject to dose Delivery errors due to errors in position, energy and intensity of the delivered Beam. In addition, finite scan speeds, Beam spill non-uniformities, and delays in detector, detector electronics and magnet responses will all contribute errors in Delivery. In this paper, we present dose errors for an 8 × 10 × 8 cm(3) target of uniform water equivalent density with 8 cm spread out Bragg peak and a prescribed dose of 2 Gy. Lower doses are also analyzed and presented later in the paper. Beam energy errors and errors due to limitations of scanning System hardware have been included in the analysis. By using Gaussian shaped pencil Beams derived from measurements in the research room of the James M Slater Proton Treatment and Research Center at Loma Linda, CA and executing treatment simulations multiple times, statistical dose errors have been calculated in each 2.5 mm cubic voxel in the target. These errors were calculated by delivering multiple treatments to the same volume and calculating the rms variation in delivered dose at each voxel in the target. The variations in dose were the result of random Beam Delivery errors such as proton energy, spot position and intensity fluctuations. The results show that with reasonable assumptions of random Beam Delivery errors, the spot scanning technique yielded an rms dose error in each voxel less than 2% or 3% of the 2 Gy prescribed dose. These calculated errors are within acceptable clinical limits for radiation therapy.
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a prototype Beam Delivery System for the proton medical accelerator at loma linda
Medical Physics, 1991Co-Authors: George Coutrakon, M Bauman, David A Lesyna, Daniel W Miller, J Nusbaum, Jon W Slater, J Johanning, J Miranda, P M Deluca, J SiebersAbstract:A variable energy proton accelerator was commissioned at Fermi National Accelerator Laboratory for use in cancer treatment at the Loma Linda University Medical Center. The advantages of precise dose localization by proton therapy, while sparing nearby healthy tissue, are well documented [R. R. Wilson, Radiology 47, 487 (1946); M. Wagner, Med. Phys. 9, 749 (1982); M. Goitein and F. Chen, Med. Phys. 10, 831 (1983)]. One of the components of the proton therapy facility is a Beam Delivery System capable of delivering precise dose distributions to the target volume in the patient. To this end, a prototype Beam Delivery System was tested during the accelerator's commissioning period. The Beam Delivery System consisted of a Beam spreading device to produce a large, uniform field, a range modulator to generate a spread out Bragg peak (SOBP), and various Beam detectors to measure intensity, Beam centering, and dose distributions. The Beam Delivery System provided a uniform proton dose distribution in a cylindrical volume of 20-cm-diam area and 9-cm depth. The dose variations throughout the target volume were found to be less than +/- 5%. Modifications in the range modulator should reduce this considerably. The central axis dose rate in the region of the SOBP was found to be 0.4 cGy/spill with an incident Beam intensity of 6.7 x 10(9) protons/spill. With an accelerator repetition rate of 30 spills/min and expected intensity of 2.5 x 10(10) protons/spill for patient treatment, this System can provide 50 cGy/min for a 20-cm-diam field and 9-cm range modulation.(ABSTRACT TRUNCATED AT 250 WORDS)