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Calibration of EBT2 film using a red-channel pdd method in combination with a modified three-channel technique

MEDICAL PHYSICS 2015年第10期42卷 5838-5847页

作者： Chang, Liyun Ho, Sheng-Yow Lee, Tsair-Fwu Yeh, Shyh-An Ding, Hueisch-Jy Chen, Pang-Yu I Shou Univ Dept Med Imaging Kaohsiung 82445 Taiwan I Shou Univ Dept Radiol Sci Kaohsiung 82445 Taiwan Chang Jung Christian Univ Dept Nursing Tainan 73657 Taiwan Chi Mei Med Ctr Dept Radiat Oncol Tainan 73657 Taiwan Natl Kaohsiung Univ Appl Sci Med Phys & Informat Lab Dept Elect Engn Kaohsiung 80778 Taiwan I Shou Univ Dept Med Imaging & Radiol Sci Kaohsiung 82445 Taiwan E Da Hosp Dept Radiat Oncol Kaohsiung 82445 Taiwan Sinlau Christian Hosp Dept Radiat Oncol Tainan 70142 Taiwan

Purpose: Ashland Inc. EBT2 and EBT3 films are widely used in quality assurance for radiation therapy;however, there remains a relatively high degree of uncertainty [B. Hartmann, M. Martisikova, and O. Jakel, "Homogeneity of Gafchromic EBT2 film," Med. Phys. 37, 1753-1756 (2010)]. Micke et al. (2011) recently improved the spatial homogeneity using all color channels of a flatbed scanner;however, van Hoof et al. (2012) pointed out that the corrected nonuniformity still requires further investigation for larger fields. To reduce the calibration errors and the uncertainty, the authors propose a new red-channel percentage-depth-dose method in combination with a modified three-channel technique. methods: For the ease of comparison, the EBT2 film image used in the authors' previous study (2012) was reanalyzed using different approaches. Photon beams of 6-MV were delivered to two different films at two different beam on times, resulting in the absorption doses of ranging from approximately 30 to 300 cGy at the vertical midline of the film, which was set to be coincident with the central axis of the beam. The film was tightly sandwiched in a 30(3)-cm(3) polystyrene phantom, and the pixel values for red, green, and blue channels were extracted from 234 points on the central axis of the beam and compared with the corresponding depth doses. The film was first calibrated using the multichannel method proposed by Micke et al. (2010), accounting for nonuniformities in the scanner. After eliminating the scanner and dose-independent nonuniformities, the film was recalibrated via the dose-dependent optical density of the red channel and fitted to a power function. This calibration was verified via comparisons of the dose profiles extracted from the films, where three were exposed to a 60. physical wedge field and three were exposed to composite fields, and all of which were measured in a water phantom. A correction for optical attenuation was implemented, and treatment plans of inten

关键词： EBT2 film nonuniformity correction three-channel dosimetry pdd method

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The suitable dose range for the calibration of EBT2 film by the pdd method with a comparison of two curve fitting algorithms

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NUCLEAR INSTRUMENTS & methodS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 2015年 777卷 85-90页

作者： Chang, Liyun Ho, Sheng-Yow Lee, Tsair-Fwu Yeh, Shyh-An Ding, Hueisch-Jy Chen, Pang-Yu I Shou Univ Dept Med Imaging & Radiol Sci Kaohsiung Taiwan Chi Mei Med Ctr Dept Radiat Oncol Tainan Taiwan Natl Kaohsiung Univ Appl Sci Dept Elect Engn Med Phys & Informat Lab Kaohsiung 807 Taiwan E Da Hosp Dept Radiat Oncol Kaohsiung Taiwan Sinlau Christian Hosp Dept Radiat Oncol Tainan Taiwan

EBT2 Film is a convenient dosimetry quality assurance (QA) tool with high 2D dosimetry resolution and a self development property for use in verifications of radiation therapy treatment planning and special projects;however, the user will suffer from a relatively higher degree of uncertainty (more than +/- 6% by Hartmann el. al. [29]), and the trouble of cutting one piece of film into small pieces and then reintegrating them each Lime. To prevent this tedious cutting work, and save calibration time and budget, a dose range analysis is presented in this study for EBT2 film calibration using the Percentage-Depth-Dose (pdd) method. Different combinations of the three dose ranges, 9-26 cGy, 33-97 cGy and 109-320 cGy, with two types of curve fitting algorithms, film pixel values and net optical densities converting into doses, were tested and compared. With the lowest error and acceptable inaccuracy of less than 3 cGy for the clinical close range (9-320 cGy), a single film calibrated by the net optical density algorithm with the dose range 109-320 cGy was suggested for routine calibration. (C) 2014 Elsevier B.V. All rights reserved.

关键词： EBT2 film Film calibration pdd method Dose range Curve fitting algorithm

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The Applications of Order Reduction methods in Nonlinear Dynamic Systems

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Sound & Vibration 2020年第2期54卷 113-125页

作者： Nan Wu Kuan Lu Yulin Jin Haopeng Zhang Yushu Chen Institute of Vibration Engineering Northwestern Polytechnical UniversityXi’an710072China School of Astronautics Harbin Institute of TechnologyHarbin150001China School of Automation Engineering University of Electronic Science and Technology of ChinaChengdu611731China

Two different order reduction methods of the deterministic and stochastic systems are discussed in this ***,the transient proper orthogonal decomposition(T-POD)method is introduced based on the high-dimensional nonlinear dynamic *** optimal order reduction conditions of the T-POD method are provided by analyzing the rotor-bearing system with pedestal looseness fault at both *** efficiency of the T-POD method is verified via comparing with the results of the original ***,the polynomial dimensional decomposition(pdd)method is applied to the 2 DOFs spring system considering the uncertain stiffness to study the amplitude-frequency *** numerical results obtained by the pdd method agree well with the Monte Carlo simulation(MCS)*** results of the pdd method can approximate to MCS better with the increasing of the polynomial ***,the Uniform-Legendre polynomials can eliminate perturbation of the pdd method to a certain extent via comparing it with the Gaussian-Hermite polynomials.

关键词： Uncertainty T-POD method pdd method rotor spring

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Mathematical parameterization of dosimetry quality index checking of the photon beam based on IAEA TRS-398 protocol

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JOURNAL OF KING SAUD UNIVERSITY SCIENCE 2019年第4期31卷 1543-1546页

作者： Bencheikh, Mohamed Maghnouj, Abdelmajid Tajmouati, Jaouad Hassan II Univ Casablanca Fac Sci & Tech Mohammedia Phys Dept Mohammadia Morocco Univ Sidi Mohamed Ben Abdellah Fac Sci Dhar El Mahraz Phys Dept LISTA Lab Fes Morocco

The quality is essential for radiation use in medicine and the beam quality index is the basic parameter to periodically check the normal functioning of Linac head in radiotherapy treatment. It is recommended by IAEA protocols TRS-398 based on absorbed dose in water. The pdd method is used as a basis of the parameterization of the photon beam quality for predicting its variation with beam energy and field size. The objective of this work is to establish a mathematical law for predicting and checking the beam dosimetry quality index according to field size and beam energy based on IAEA TRS-398 protocol. For an easier and more reliable procedure determination of the beam quality based on TRS 398, two empirical laws were therefore established with an accuracy better than 2%. They can serve the basic floor to medical physicist to verify and to control the dosimetry output quality at arbitrary field size. Our findings aim to facilitate the dosimetry quality control that set in use according to current conditions for checking out the radiotherapy efficiency and the safety inside the treatment room. (C) 2019 Production and hosting by Elsevier B.V. on behalf of King Saud University.

关键词： Photon beam Quality index pdd method Empirical law Dosimetry

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Joint Design of Beam Selection and Precoding for mmWave MU-MIMO Systems with Lens Antenna Array 28

Joint Design of Beam Selection and Precoding for mmWave MU-M...

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28th Annual IEEE International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC)

作者： Guo, Rongbin Cai, Yunlong Shi, Qingjiang Zhao, Minjian Champagne, Benoit Zhejiang Univ Coll ISEE Hangzhou 310027 Zhejiang Peoples R China Zhejiang Sci Tech Univ Sch Info Sci & Tech Hangzhou 310018 Zhejiang Peoples R China McGill Univ Dept Elect & Comp Engn Montreal PQ H3A 0E9 Canada

ISBN: (纸本)9781538635315

Wireless transmission with lens antenna arrays is becoming more and more attractive for millimeter wave (mmWave) multiple-input multiple-output (MIMO) systems with limited radio frequency (RF) chains due to their energy-focusing capability. In this paper, we consider the joint design of beam selection and precoding to maximize the sum rate of a downlink single-sided lens MU-MIMO mmWave system under transmit power constraints. We first formulate the optimization problem into a tractable form using the popular weighted minimum mean squared error (WMMSE) approach. To solve this problem, we then propose an efficient joint beam selection and precoding algorithm based on the innovative penalty dual decomposition (pdd) method. Simulation results demonstrate that our proposed algorithm can achieve near-optimal performance when compared to the fully digital precoding scheme and thus outperform the competing methods.(1)

关键词： mmWave MU-MIMO lens antenna array beam selection WMMSE pdd method

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Evaluation of Multiple-Sampling Function used with a Microtek flatbed scanner for Radiation Dosimetry Calibration of EBT2 Film

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NUCLEAR INSTRUMENTS & methodS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 2016年 832卷 179-183页

作者： Chang, Liyun Ho, Sheng-Yow Ding, Hueisch-Jy Hwang, Ing-Ming Chen, Pang-Yu Lee, Tsair-Fwu I Shou Univ Dept Med Imaging & Radiol Sci Kaohsiung 82445 Taiwan Chang Jung Christian Univ Dept Nursing Tainan 71101 Taiwan Chi Mei Med Ctr Dept Radiat Oncol Tainan 73657 Taiwan Shu Zen Coll Med & Management Dept Med Imaging & Radiol Kaohsiung 82144 Taiwan Sinlau Christian Hosp Dept Radiat Oncol Tainan 70142 Taiwan Natl Kaohsiung Univ Appl Sci Dept Elect Engn Med Phys & Informat Lab Kaohsiung 80778 Taiwan

The radiochromic EBT2 film is a widely used quality assurance device for radiation therapy. This study evaluated the film calibration performance of the multiple-sampling function, a function of the Scan Wizard Pro scanning software provided by the manufacturer, when used with Microtek 9800XL plus (9800XL(+)) flatbed scanner. By using the pdd method, each one of the eight EBT2 films, four delivered by 290 monitor unit (MU) and four by 88 MU via 6-MV photon beams, was tightly sandwiched in a 30(3)-cm(3) water equivalent polystyrene phantom prior to irradiation. Before and after irradiation, all films were scanned using the Microtek 9800XL(+) scanner with five different modes of the multiple-sampling function, which could generate the image with the averaged result of multiple-sampling. The net optical densities (netOD) on the beam central axis of film were assigned to corresponding depth doses for calibration. For each sampling mode with either delivered MU, the depth-dose uncertainty of a single film from repeated scans and that of a single scan of the four films were analyzed. Finally, the calibration error and the combined calibration uncertainty between film determined depth-doses and delivered depth doses were calculated and evaluated for each sampling mode. All standard deviations and the calibration error were demonstrated to be unrelated to the number of sampling lines. The calibration error of the 2-line and 16-line mode was within 3 cGy and better than that of the other modes. The combined uncertainty of the 2-line mode was the lowest, which was generally less than 6 cGy except for the delivered dose around 100 cGy. The evaluation described herein revealed that the EBT2 film calibrated with the 2-line mode has relatively lower error, scanning time and combined uncertianty. Therefore, it is recommended for routine EBT2 film calibration and verification of treatment plans. (C) 2016 Elsevier B.V. All rights reserved.

关键词： EBT2 film Film calibration pdd method Microtek scanner Multiple-sampling

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Dependency of EBT2 film calibration curve on postirradiation time

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MEDICAL PHYSICS 2014年第2期41卷 021726页

作者： Chang, Liyun Ho, Sheng-Yow Ding, Hueisch-Jy Lee, Tsair-Fwu Chen, Pang-Yu I Shou Univ Dept Med Imaging & Radiol Sci Kaohsiung 82445 Taiwan Chi Mei Med Ctr Dept Radiat Oncol Tainan 73657 Taiwan Natl Kaohsiung Univ Appl Sci Dept Elect Engn Med Phys & Informat Lab Kaohsiung 80778 Taiwan Sinlau Christian Hosp Dept Radiat Oncol Tainan 70142 Taiwan

Purpose: The Ashland Inc. product EBT2 film model is a widely used quality assurance tool, especially for verification of 2-dimensional dose distributions. In general, the calibration film and the dose measurement film are irradiated, scanned, and calibrated at the same postirradiation time (PIT), 1-2 days after the films are irradiated. However, for a busy clinic or in some special situations, the PIT for the dose measurement film may be different from that of the calibration film. In this case, the measured dose will be incorrect. This paper proposed a film calibration method that includes the effect of PIT. methods: The dose versus film optical density was fitted to a power function with three parameters. One of these parameters was PIT dependent, while the other two were found to be almost constant with a standard deviation of the mean less than 4%. The PIT-dependent parameter was fitted to another power function of PIT. The EBT2 film model was calibrated using the pdd method with 14 different PITs ranging from 1 h to 2 months. Ten of the fourteen PITs were used for finding the fitting parameters, and the other four were used for testing the model. Results: The verification test shows that the differences between the delivered doses and the film doses calculated with this modeling were mainly within 2% for delivered doses above 60 cGy, and the total uncertainties were generally under 5%. The errors and total uncertainties of film dose calculation were independent of the PIT using the proposed calibration procedure. However, the fitting uncertainty increased with decreasing dose or PIT, but stayed below 1.3% for this study. Conclusions: The EBT2 film dose can be modeled as a function of PIT. For the ease of routine calibration, five PITs were suggested to be used. It is recommended that two PITs be located in the fast developing period (1 similar to 6 h), one in 1 similar to 2 days, one around a week, and one around a month. (C) 2014 American Association of Physi

关键词： EBT2 film calibration pdd method postirradiation time

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