168 results on '"Modulation factor"'
Search Results
2. CIRM-SNN: Certainty Interval Reset Mechanism Spiking Neuron for Enabling High Accuracy Spiking Neural Network.
- Author
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Niu, Li-Ye and Wei, Ying
- Subjects
CERTAINTY ,MEMBRANE potential ,ENERGY consumption - Abstract
Spiking neural network (SNN) based on sparse trigger and event-driven information processing has the advantages of ultra-low power consumption and hardware friendliness. As a new generation of neural networks, SNN is widely concerned. At present, the most effective way to realize deep SNN is through artificial neural network (ANN) conversion. Compared with the original ANN, the converted SNN suffers from performance loss. This paper adjusts the spike firing rate of spiking neurons to minimize the performance loss of SNN in the conversion process. We map the ANN weights to the corresponding SNN after continuous normalization, which ensures that the spike firing rate of the neuron is in the normal range. We propose a certainty interval reset mechanism (CIRM), which effectively reduces the loss of membrane potential and avoids the problem of neuronal over-activation. In the experiment, we added a modulation factor to the CIRM to further adjust the spike firing rate of neurons. The accuracy of the converted SNN on CIFAR-10 is 1.026% higher than that of the original ANN. The algorithm not only achieves the lossless conversion of ANN, but also reduces the network energy consumption. Our algorithm also effectively improves the accuracy of SNN (VGG-15) on CIFAR-100 and decreases the network delay. The work of this paper is of great significance for developing high-precision depth SNN. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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3. Generation and Modulation of Controllable Multi-Focus Array Based on Phase Segmentation.
- Author
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Liu, Zihan, Hou, Jiaqing, Zhang, Yu, Wen, Tong, Fan, Lianbin, Zhang, Chen, Wang, Kaige, and Bai, Jintao
- Subjects
FAST Fourier transforms ,PHASE modulation - Abstract
A Circular-Sectorial Phase Segmentation (CSPS) noniterative method for effectively generating and manipulating muti-focus array (MFA) was proposed in this work. The theoretical model of the CSPS was built up based on vectorial diffraction integral and the phase modulation factor was deduced with inverse fast Fourier transform. By segmenting the entrance pupil into specified regions, which were sequentially assigned with the values carried out by phase modulation factor, the methodology could generate flexible MFAs with desired position and morphology. Subsequently, the CSPS was investigated in parallelized fabrication with a laser direct writing system. The positioning accuracy was greater than 96% and the morphologic consistency of the parallelly fabricated results was greater than 92%. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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- View/download PDF
4. Effect of modulation factor and low dose threshold level on gamma pass rates of single isocenter multi-target SRT treatment plans.
- Author
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Timakova E and Zavgorodni SF
- Abstract
Purpose: SRS MapCHECK (SMC) is a commercially available patient-specific quality assurance (PSQA) tool for stereotactic radiosurgery (SRS) applications. This study investigates the effects of degree of modulation, location off-axis, and low dose threshold (LDT) selection on gamma pass rates (GPRs) between SMC and treatment planning system, Analytical Anisotropic Algorithm (AAA), or Vancouver Island Monte Carlo (VMC++ algorithm) system calculated dose distributions., Methods: Volumetric-modulated arc therapy (VMAT) plans with modulation factors (MFs) ranging from 2.7 to 10.2 MU/cGy were delivered to SMC at isocenter and 6 cm off-axis. SMC measured dose distributions were compared against AAA and VMC++ via gamma analysis (3%/1 mm) with LDT of 10% to 80% using SNC Patient software., Results: Comparing on-axis SMC dose against AAA and VMC++ with LDT of 10%, all AAA-calculated plans met the acceptance criteria of GPR ≥ 90%, and only one VMC++ calculated plan was marginally outside the acceptance criteria with pass rate of 89.1%. Using LDT of 80% revealed decreasing GPR with increasing MF. For AAA, GPRs reduced from 100% at MF of 2.7 MU/cGy to 57% at MF of 10.2 MU/cGy, and for VMC++ calculated plans, the GPRs reduced from 89% to 60% in the same MF range. Comparison of SMC dose off-axis against AAA and VMC++ showed more pronounced reduction of GPR with increasing MF. For LDT of 10%, AAA GPRs reduced from 100% to 83% in the MF range of 2.7 to 9.8 MU/cGy, and VMC++ GPR reduced from 100% to 91% in the same range. With 80% LDT, GPRs dropped from 100% to 42% for both algorithms., Conclusions: MF, dose calculation algorithm, and LDT selections are vital in VMAT-based SRT PSQA. LDT of 80% enhances sensitivity of gamma analysis for detecting dose differences compared to 10% LDT. To achieve better agreement between calculated and SMC dose, it is recommended to limit the MF to 4.6 MU/cGy on-axis and 3.6 MU/cGy off-axis., (© 2024 The Author(s). Journal of Applied Clinical Medical Physics is published by Wiley Periodicals, Inc. on behalf of The American Association of Physicists in Medicine.)
- Published
- 2024
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5. 高增益准Z源网络间接矩阵变换器的结构研究.
- Author
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王固萍, 叶培乐, 王斌, 程启明, and 薛育1鲁飞
- Subjects
MATRIX converters ,VOLTAGE-frequency converters ,VOLTAGE ,TOPOLOGY ,QUASI-Newton methods - Abstract
Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2021
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6. Generation and Modulation of Controllable Multi-Focus Array Based on Phase Segmentation
- Author
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Zihan Liu, Jiaqing Hou, Yu Zhang, Tong Wen, Lianbin Fan, Chen Zhang, Kaige Wang, and Jintao Bai
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phase segmentation ,multi-focus array ,modulation factor ,numerical simulation ,parallelized laser fabrication ,Mechanical engineering and machinery ,TJ1-1570 - Abstract
A Circular-Sectorial Phase Segmentation (CSPS) noniterative method for effectively generating and manipulating muti-focus array (MFA) was proposed in this work. The theoretical model of the CSPS was built up based on vectorial diffraction integral and the phase modulation factor was deduced with inverse fast Fourier transform. By segmenting the entrance pupil into specified regions, which were sequentially assigned with the values carried out by phase modulation factor, the methodology could generate flexible MFAs with desired position and morphology. Subsequently, the CSPS was investigated in parallelized fabrication with a laser direct writing system. The positioning accuracy was greater than 96% and the morphologic consistency of the parallelly fabricated results was greater than 92%.
- Published
- 2022
- Full Text
- View/download PDF
7. Total body irradiation of bone marrow transplant using helical TomoTherapy with a focus on the quality of dose contribution at junction target volumes.
- Author
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Sresty, N. V. N. Madhusudhana, Gudipudi, Deleep, Krishnam Raju, A., Anil kumar, T., Lakshmi, V. R. P., Srikanth, G., and Narasimha, M.
- Abstract
Purpose: Total body irradiation (TBI) can be safely delivered on TomoTherapy (Accuray, Sunnyvale, CA, USA) in both pediatric and adult patients with proper imaging and planning despite the length constraint of 135 cm. To overcome this limitation, two CT (Computed Tomography) scans (CT1& CT2) are taken in patients above 135 cm in height. Adequate junction dose coverage is important in TBI. Presently, there is no clinical report with a focus on the quality of dose distribution at the CT junction in view of the guidelines on quality of coverage from the RTOG. Hence, our main objectives were to evaluate the dose distribution and quality of coverage at the junction in 16 patients who received TBI using TomoTherapy. Methods: PTV(upper) and PTV(lower) along with a junction were created on CT1 and CT2, respectively. Subsequently, the 10 cm junction in the thigh region was divided into five target volumes of 2 cm thickness with dose prescription ranging from 10 to 90% to deliver a total dose equal to 100% when fused. Results: The D
50 was equal to the prescribed dose in most of the cases ranging from 99.5 to 104% for PTV(upper), 100–103% for PTV(lower), and 99.5–108% for junctional PTVs (1PTV, 2PTV, 3PTV, 4PTV, and 5PTV). The average D95 doses from PTV(upper) and PTV(lower) were 97 ± 1.4% and 96.7 ± 1.08%, respectively. The average D95 doses for 1PTV, 2PTV, 3PTV, 4PTV, and 5PTV were 96.1 ± 1.88%, 91.6 ± 1.82%, 87.3 ± 1.5%, 91.6 ± 1.4%, and 96.2 ± 1.5% respectively. QRTOG values ranged between 0.85 and 1.05 and were in concordance with RTOG guidelines. Conclusion: Since junction-based planning was required for most TBI patients, it is essential to evaluate the quality of dose coverage in the junction for better TBI plans. [ABSTRACT FROM AUTHOR]- Published
- 2021
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8. Research on the modulation factor of the constrained TV for optical deflection tomography reconstruction.
- Author
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Li, Huaxin, Zhang, Bin, Kong, Huihua, and Pan, Jinxiao
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DEFLECTION (Light) , *ADAPTIVE modulation , *CONVEX sets , *ALGORITHMS , *OPTICAL tomography , *COMPRESSED sensing - Abstract
Under the condition of extremely under-sampling, the iterative algorithm based on the total variation(TV) constrain is common for the reconstruction of optical deflection tomography. In the algorithm, the minimization of TV is implemented by the gradient descent approach, and the constraints are performed by projection on convex sets (POCS). In this paper, we discuss the modulation factor of the gradient descent method, and propose a new adaptive modulation factor for gradient descent. Experiments were done on a series of modulation factor functions under different projection angles and noise environment, and the experimental results were compared and analysed. And the algorithm proposed in this paper is compared with the soft threshold filter TV minimization algorithm. The results demonstrate that the adaptive modulation factor proposed in this paper can automatically and continuously update the value of the modulation factor, reduce the reconstruction error and improve the reconstruction quality. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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9. Fluence-weighted average subfield size in helical TomoTherapy.
- Author
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Howitz, Simon, Wiezorek, Tilo, Wittig, Andrea, Vorwerk, Hilke, and Zink, Klemens
- Abstract
Helical TomoTherapy allows a highly conformal dose distribution to complex target geometries with a good protection of organs at risk. However, the small field sizes associated with this method are a possible source of dosimetrical uncertainties. The IAEA has published detector-specific field output correction factors for static fields of the TomoTherapy in the TRS483. This work investigates the average subfield size of helical TomoTherapy plans. A new parameter for helical TomoTherapy was defined – the fluence-weighted average subfield size. The subfield sizes were extracted from the leaf-opening time sinograms in the RT-plan files for 30 clinical prostate and head and neck plans and were put in relation to Delat4 Phantom+ measurement results. Additionally the influence of planning parameters on the subfield size was studied by varying the modulation factor, number of iterations and pitch in the dose optimization and calculation for three different clinical indications H&N, prostate and rectum cancer. Selected plans were dosimetrically verified by Delta4 measurements to examine the reliability in dependence of the average subfield size. Furthermore, the impact of the planning parameters on a) the dose distribution, with regard to the planning target volume and regions at risks, and b) machine characteristics such as delivery time, actual modulation factor and leaf-opening times were evaluated. The average equivalent square subfield lengths ( s ¯ e q) of the two investigated indications did not differ significantly – prostate plans: 2.75 ± 0.14 cm and H&N plans: 2.70 ± 0.16 cm, both with a jaw width of 2.5 cm. No correlation between field size and measured dose deviation was detected. The number of iterations and the modulation factor have a considerable influence on the average subfield size. The higher the planned modulation factor and the more iterations are used during optimization, the smaller is the subfield size. In our pilot study plans were calculated with field sizes s ¯ e q between 4.2 cm and 1.7 cm, with a jaw width of 2.5 cm. Again, the measurement results of Delta4 showed no significant deviation from the doses calculated by the TomoTherapy planning system for the whole range of subfield sizes, and no significant correlation between field sizes and dose deviations was found. As expected, the clinical dose distribution improved with increasing modulation factor and an increasing number of iterations. The compromise between an improved dose distribution and smaller s ¯ e q was shown. In this work, a method was presented to determine the average subfield size for helical TomoTherapy plans. The response of the Delta4 did not show any dependence on field size in the range of the field sizes covered by the studied plans. The influence of the subfield sizes on other dosimetry systems remains to be investigated. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
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10. Catalyst Replacement Policy on Multienzymatic Systems: Theoretical Study in the One-Pot Sequential Batch Production of Lactofructose Syrup
- Author
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Pablo Silva, Vanessa Arancibia, Daniela Cid, Oscar Romero, Andrés Illanes, and Lorena Wilson
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multi-enzymatic reactions ,one-pot ,catalyst replacement policy ,modulation factor ,sequential batch ,lactofructose syrup ,Chemical technology ,TP1-1185 ,Chemistry ,QD1-999 - Abstract
One-pot systems are an interesting proposal to carry out multi-enzymatic reactions, though this strategy implies establishing an optimal balance between the activity and operability of the involved enzymes. This is crucial for enzymes with marked differences in their operational stability, such as one-pot production of lactofructose syrup from cheese whey permeate, which involves two enzymes—β-galactosidase (β-gal) and glucose isomerase (GI). The aim of this work was to study the behavior of one-pot sequential batch production of lactofructose syrup considering both enzymes immobilized individually, in order to evaluate and design a strategy of replacement of the catalysts according to their stabilities. To this end, the modelling and simulation of the process was carried out, considering simultaneously the kinetics of both reactions and the kinetics of inactivation of both enzymes. For the latter, it was also considered the modulating effect that sugars present in the medium may have on the stability of β-gal, which is the less stable enzyme. At the simulated reaction conditions of 40 °C, pH 7, and 0.46 (IUGI/IUβ-gal), the results showed that considering the stability of β-gal under non-reactive conditions, meaning in absence of the effect of modulation, it is necessary to carry out four replacements of β-gal for each cycle of use of GI. On the other hand, when considering the modulation caused by the sugars on the β-gal stability, the productivity increases up to 23% in the case of the highest modulation factor studied (η = 0.8). This work shows the feasibility of conducting a one-pot operation with immobilized enzymes of quite different operational stability, and that a proper strategy of biocatalyst replacement increases the productivity of the process.
- Published
- 2021
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11. Determining efficient helical IMRT modulation factor from the MLC leaf‐open time distribution on precision treatment planning system.
- Author
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Boyd, Robert, Jeong, Kyoungkeun, and Tomé, Wolfgang A.
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INTENSITY modulated radiotherapy ,RADIATION dosimetry ,LIMIT theorems ,ACCURACY ,CLINICAL trials - Abstract
Purpose: Since the modulation factor (MF) impacts both plan quality and delivery efficiency in tomotherapy Intensity Modulated Radiation Therapy (IMRT) treatment planning, the purpose of this study was to demonstrate a technique in determining an efficient MF from the Multileaf Collimator (MLC) leaf‐open time (LOT) distribution of a tomotherapy treatment delivery plan. Methods: Eight clinical plans of varying complexity were optimized with the highest allowed MF on the Accuracy Precision treatment planning system. Using a central limit theorem argument a range of reduced MFs were then determined from the first two moments of the LOT distribution. A step down approach was used to calculate the reduced‐MF plans and plan comparison tools available on the Precision treatment planning system were used to evaluate dose differences with the reference plan. Results: A reduced‐MF plan that balanced delivery time and dosimetric quality was found from the set of five MFs determined from the LOT distribution of the reference plan. The reduced‐MF plan showed good agreement with the reference plan (target and critical organ dose‐volume region of interest dose differences were within 1% and 2% of prescription dose, respectively). Discussion: Plan evaluation and acceptance criteria can vary depending on individual clinical expectations and dosimetric quality trade‐offs. With the scheme presented in this paper a planner should be able to efficiently generate a high‐quality plan with efficient delivery time without knowing a good MF beforehand. Conclusion: A methodology for deriving a reduced MF from the LOT distribution of a high MF treatment plan using the central limit theorem has been presented. A scheme for finding a reduced MF from a set of MFs that results in a plan balanced in both dosimetric quality and treatment delivery efficiency has also been presented. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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12. A New Pulse Shift Method of DC Bus Current Detection for Driving with a Low Modulation Factor
- Author
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Sano Sota, Akira Satake, and Shinichi Furutani
- Subjects
Physics ,business.industry ,Optoelectronics ,Electrical and Electronic Engineering ,Current (fluid) ,business ,Industrial and Manufacturing Engineering ,DC-BUS ,Modulation factor ,Pulse (physics) - Published
- 2021
13. RFID Backscattering in Long-Range Scenarios.
- Author
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Amato, Francesco, Torun, Hakki M., and Durgin, Gregory D.
- Abstract
This paper presents a 5.8-GHz RFID tag that, by exploiting the quantum tunneling effect, significantly increases the range of backscatter radio links. We present an electronically simple Tunneling RFID Tag characterized by return gains as high as 35 dB with link sensitivity as low as −81 dBm. Without relevant increase in power consumption, the tunneling tag enables a host of new wireless sensors and Internet of Things applications that require both the long range of conventional wireless links and the low power consumption of semi-passive RFID devices. Selected measurements demonstrate a reader-to-tag separation distance 10 times higher than the maximum range of ideal semi-passive tags. Moreover, the collected experimental results allowed to outline a mathematical model demonstrating how the long-range RFID tag prototype can achieve distances unusual for this technology. [ABSTRACT FROM PUBLISHER]
- Published
- 2018
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14. The robustness of truncated Airy beam in PT Gaussian potentials media.
- Author
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Wang, Xianni, Fu, Xiquan, Huang, Xianwei, Yang, Yijun, and Bai, Yanfeng
- Subjects
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GAUSSIAN function , *FREE-space optical technology , *WAVELETS (Mathematics) , *HOMODYNE detection , *MINIMUM variance estimation - Abstract
The robustness of truncated Airy beam in parity-time (PT) symmetric Gaussian potentials media is numerically investigated. A high-peak power beam sheds from the Airy beam due to the media modulation while the Airy wavefront still retain its self-bending and non-diffraction characteristics under the influence of modulation parameters. Increasing the modulation factor results in the smaller value of maximum power of the center beam, and the opposite trend occurs with the increment of the modulation depth. However, the parabolic trajectory of the Airy wavefront does not be influenced. By utilizing the unique features, the Airy beam can be used as a long distance transmission source under the PT symmetric Gaussian potentials medium. [ABSTRACT FROM AUTHOR]
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- 2018
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15. Dynamic conformal arcs-based single-isocenter VMAT planning technique for radiosurgery of multiple brain metastases
- Author
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William H. St. Clair, Allison N Palmiero, Mark E. Bernard, and Damodar Pokhrel
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Lung Neoplasms ,medicine.medical_treatment ,Dose distribution ,Radiosurgery ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Carcinoma, Non-Small-Cell Lung ,Humans ,Medicine ,Dosimetry ,Radiology, Nuclear Medicine and imaging ,Radiological and Ultrasound Technology ,Brain Neoplasms ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Isocenter ,Radiotherapy Dosage ,Planning Techniques ,Modulation factor ,Oncology ,Treatment delivery ,030220 oncology & carcinogenesis ,Dynamic conformal arc ,Brain lesions ,Radiotherapy, Intensity-Modulated ,business ,Nuclear medicine - Abstract
Multiple small beamlets in the delivery of highly modulated single-isocenter HyperArc VMAT plan can lead to dose delivery errors associated with small-field dosimetry, which can be a major concern for stereotactic radiosurgery for multiple brain lesions. Herein, we describe and compare a clinically valuable dynamic conformal arc (DCA)-based VMAT (DCA-VMAT) approach for stereotactic radiosurgery of multiple brain lesions using flattening filter free beams to minimize this effect. Original single-isocenter HyperArc style VMAT and DCA-VMAT plans were created on 7 patients with 2 to 8 brain lesions (total 35 lesions) for 10 MV- flattening filter free beam. 20 Gy was prescribed to each lesion. For identical planning criteria, DCA-VMAT utilizes user-controlled field aperture shaper before VMAT optimization. Plans were evaluated for conformity and target coverage, low- and intermediate dose spillages to brain volume that received more than 30% (V30%) and 50% (V50%) of prescription dose. Additionally, mean brain dose, V8, V12 and maximal dose to adjacent organs-at-risk (OAR) including hippocampi were reported. Total monitor units, beam modulation factor, treatment delivery efficiency, and accuracy were recorded. Comparing with original VMAT, DCA-VMAT plans provided similar tumor dose, target coverage and conformity, yet tighter radio-surgical dose distribution with lower dose to normal brain V30% (p = 0.009), V50% (p = 0.05) and other OAR including lower dose to hippocampi. Lower total number of monitor units and smaller beam modulation factor reduced beam on time by 2.82 min (p0.001), on average (maximum up to 3.8 min). Beam delivery accuracy was improved by 8%, on average (p0.001) and maximum up to 13% in some cases for DCA-VMAT plans. This novel DCA-VMAT approach provided excellent plan quality, reduced dose to normal brain, and other OAR while significantly reducing beam-on time for radiosurgery of multiple brain lesions-improving patient compliance and clinic workflow. It also provided less MLC modulation through the targets-potentially minimizing small field dosimetry errors as demonstrated by quality assurance results. Incorporating DCA-based VMAT optimization in HyperArc module for radiosurgery of multiple brain lesions merits future investigation.
- Published
- 2021
16. Analysis of modulation factor to shorten the delivery time in helical tomotherapy.
- Author
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Shimizu, Hidetoshi, Sasaki, Koji, Tachibana, Hiroyuki, Tomita, Natsuo, Makita, Chiyoko, Nakashima, Kuniyasu, Yokoi, Kazushi, Kubota, Takashi, Yoshimoto, Manabu, Iwata, Tohru, and Kodaira, Takeshi
- Subjects
THERAPEUTICS ,PROSTATE cancer ,ELECTRONIC modulation ,SIMULATED annealing ,WORKING hours - Abstract
A low modulation factor (MF) maintaining a good dose distribution contributes to the shortening of the delivery time and efficiency of the treatment plan in helical tomotherapy. The purpose of this study was to reduce the delivery time using initial values and the upper limit values of MF. First, patients with head and neck cancer (293 cases) or prostate cancer (181 cases) treated between June 2011 and July 2015 were included in the analysis of MF values. The initial MF value (MF
initia l) was defined as the average MFactual value, and the upper limit of the MF value (MFUL ) was defined according the following equation: MFUL = 2 × standard deviation of MFactual value + the average MFactual Next, a treatment plan was designed for patients with head and neck cancer (62 cases) and prostate cancer (13 cases) treated between December 2015 and June 2016. The average MFactual value for the nasopharynx, oropharynx, hypopharynx, and prostate cases decreased from 2.1 to 1.9 (p = 0.0006), 1.9 to 1.6 (p < 0.0001), 2.0 to 1.7 (p < 0.0001), and 1.8 to 1.6 (p = 0.0004) by adapting the MFinitia l and the MFUL values, respectively. The average delivery time for the nasopharynx, oropharynx, hypopharynx, and prostate cases also decreased from 19.9 s cm-1 to 16.7 s cm-1 (p < 0.0001), 15.0 s cm-1 to 13.9 s cm-1 (p = 0.025), 15.1 s cm-1 to 13.8 s cm-1 (p = 0.015), and 23.6 s cm-1 to 16.9 s cm-1 (p = 0.008) respectively. The delivery time was shortened by the adaptation of MFinitia l and MFUL values with a reduction in the average MFactual for head and neck cancer and prostate cancer cases. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
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17. Results of a 10-year survey of workload for 10 treatment vaults at a high-throughput comprehensive cancer center.
- Author
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Saleh, Ziad H., Jeong, Jeho, Quinn, Brian, Mechalakos, James, St. Germain, Jean, and Dauer, Lawrence T.
- Subjects
LINEAR accelerators in medicine ,RADIATION shielding ,ONCOLOGY ,CARCINOGENS ,X-ray absorption - Abstract
The workload for shielding purposes of modern linear accelerators (linacs) consists of primary and scatter radiation which depends on the dose delivered to isocenter (cGy) and leakage radiation which depends on the monitor units (MUs). In this study, we report on the workload for 10 treatment vaults in terms of dose to isocenter (cGy), monitor units delivered (MUs), number of treatment sessions (Txs), as well as, use factors (U) and modulation factors (CI) for different treatment techniques. The survey was performed for the years between 2006 and 2015 and included 16 treatment machines which represent different generations of Varian linear accelerators (6EX, 600C, 2100C, 2100EX, and TrueBeam) operating at different electron and x-ray energies (6, 9, 12, 16 and 20 MeV electrons and, 6 and 15 MV x-rays). An institutional review board (IRB) approval was acquired to perform this study. Data regarding patient workload, dose to isocenter, number of monitor units delivered, beam energies, gantry angles, and treatment techniques were exported from an ARIA treatment management system (Varian Medical Systems, Palo Alto, Ca.) into Excel spreadsheets and data analysis was performed in Matlab. The average (± std-dev) number of treatment sessions, dose to isocenter, and number of monitor units delivered per week per machine in 2006 was 119 ± 39 Txs, (300 ± 116)×10
2 cGys, and (78 ± 28)×103 MUs respectively. In contrast, the workload in 2015 was 112 ± 40 Txs, (337 ± 124) × 102 cGys, and (111 ± 46) × 103 MUs. 60% of the workload (cGy) was delivered using 6 MV and 30% using 15 MV while the remaining 10% was delivered using electron beams. The modulation factors (MU/cGy) for IMRT and VMAT were 5.0 (± 3.4) and 4.6 (± 1.6) respectively. Use factors using 90° gantry angle intervals were equally distributed (~0.25) but varied considerably among different treatment techniques. The workload, in terms of dose to isocenter (cGy) and subsequently monitor units (MUs), has been steadily increasing over the past decade. This increase can be attributed to increased use of high dose hypo-fractionated regimens (SBRT, SRS) and the increase in use of IMRT and VMAT, which require higher MUs per cGy as compared to more conventional treatment (3DCRT). Meanwhile, the patient workload in terms of treatment sessions per week remained relatively constant. The findings of this report show that variables used for shielding purposes still fall within the recommendation of NCRP Report 151. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
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18. 변조도를 정밀하게 조정 하는 TACAN 안테나용 변조신호발생기.
- Author
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김종원, 손경식, and 임재현
- Abstract
TACAN(TACtical Air Navigation) was created to support military aircraft's short range navigation (200~300 mile). TACAN must fulfill a condition of MIL-STD-291C, the U.S. Military Standards, which addresses the sum of 15Hz and 135Hz should be within 55%, following the factor of modulations for both to be 21±9% each. Within the existing TACAN antenna, modulation factor for 15Hz and 135Hz are created differently depending on its diameter, wavelength, angle of gradient, internal modulation method or using frequency code. It brings up a problem where applications needed to be stopped and repaired when modulating signal exceeds the standard of MIL-STD-291C since the existing TACAN antenna does not have coordination function. Hence, plan and produce a modulating signal generator using FPGA, and check the changes in the modulation factor for 15HZ and 135Hz, depending on the values that have been set in each criteria. Moreover, allow the modulating signal generator to be automatically adjusted based on the monitoring signal emitted by antenna, and place alarm sound just in case if it exceeds the standard. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
19. Finite-Control Set Model Predictive Control Method for Torque Control of Induction Motors Using a State Tracking Cost Index.
- Author
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Ahmed, Abdelsalam A., Koh, Byung Kwon, Park, Hyo Sung, Lee, Kyo-Beum, and Lee, Young Il
- Subjects
- *
PREDICTIVE control systems , *TORQUE control , *INDUCTION motors , *PRICE indexes , *MATHEMATICAL optimization - Abstract
This paper presents a novel torque control method for two-level-inverter-fed induction motor drives. The control principle is based on a finite-control set model predictive control (FCS-MPC) using a state tracking cost index. In the online procedure of the proposed FCS-MPC, the optimal voltage vector and its corresponding optimal modulation factor are determined based on the principle of torque and rotor flux error minimization. In this method, a reference state is determined in a systematic way so that the reference torque tracking with maximum torque per ampere and flux-limited operation could be achieved. In addition, a weighting matrix for the state tracking error is optimized in offline using the linear matrix inequality based optimization problem. The efficacy of the proposed FCS-MPC method is proved by the simulation and experimental results at different working circumstances. The comparison of the presented control system with the conventional FCS-MPC and with other reported FCS-MPC with modulation control is made. The proposed algorithm yields fast dynamic performance and minimum torque and current ripples at different speed and torque levels. [ABSTRACT FROM PUBLISHER]
- Published
- 2017
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20. Optimal Combination of Pitch, Modulation Factor and Dosimetric Considerations in Treatment Planning for Total Body Irradiation Using Helical Tomotherapy.
- Author
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Kaliyaperumal V, Kataria T, Tamilselvan S, Gupta D, Abraham SK, Narang K, Banerjee S, Dayanithi K, Rajesh S, Bisht SS, and Shishak S
- Subjects
- Humans, Whole-Body Irradiation, Radiotherapy Planning, Computer-Assisted methods, Radiotherapy Dosage, Radiometry methods, Radiotherapy, Intensity-Modulated methods
- Abstract
Objective: The aim of this study is to makethe standard total body irradiation (TBI) protocol for Helical tomotherapy© (HT) and to analyze the optimal pitch and modulation factor (MF) with respect to dose homogeneity index (HI), target dose coverage, target overdose, beam on time (BOT) and mean lung dose., Materials and Methods: Ten patients who underwent high-dose TBI were taken for this study. For each patient, 35 dose plans were created by different combination of pitch and MF. The optimal pitch and MF were deduced using scatter plot and regression methodology based on target coverage, HI, target volume receiving 103%(V103%), 105%(V105%) and 107% (V107%) of the prescription dose and BOT. Using these optimal pitch and MF, the final dose plan was made and the planning aim and achieved dose was compared using two tailed student's t-test. Radiochromic films and ionization chambers were used to measure the delivered dose using anthropomorphic phantom on various points for the head and pelvis regions to verify the skin flash margin and its effect on skin dose., Results: The optimal pitch and MF value were 0.287 and 2.4 respectively. Based on optimal pitch and MF, the mean BOT was 1692 seconds with optimal inhomogeneity (7.4%). For target, D95 and D98 were 97.09% (range:94.7-99.6%, p=0.002) and 93.9% (range:91.5-94.4%,p=0.007) respectively, and mean D2 was within 107% with SD of ±1.22% (p=0.04). The mean of PTV receiving V103, V105 and V107 was 24.48% (range=7.7-36.6%, p=0.03), 5.76% (range=1.4-12.1%, SD=±3.3%), 1.93% (range=0.1-4.6%, p=0.008) respectively. Our measurements show that the flash margin did not increase the skin dose., Conclusion: In our study, the optimal combination of pitch value of 0.287 and MF value of 2.4 provided acceptable plans for all patients planned for TBI in HT. The flash margin can provide adequate coverage during patient position uncertainty without increasing the skin dose.
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- 2023
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21. Analysis of the Effect of Tomotherapy Plan Parameters on Patient-Specific Delivery Quality Assurance (DQA)
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Jina Kim, Young-Nam Kang, Chul-Seung Kay, and Hong-Seok Jang
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010302 applied physics ,medicine.medical_specialty ,business.industry ,medicine.medical_treatment ,Significant difference ,General Physics and Astronomy ,Regression analysis ,02 engineering and technology ,Patient specific ,021001 nanoscience & nanotechnology ,01 natural sciences ,Standard deviation ,Tomotherapy ,Modulation factor ,Beam delivery ,0103 physical sciences ,medicine ,Medical physics ,0210 nano-technology ,business ,Quality assurance - Abstract
When Delivery Quality Assurance (DQA) results do not coincide with specific criteria, re-measurement and re-treatment planning are required because incorrect beam delivery to the patient may occur. Therefore, an analysis of the plan parameters to find reasons for failure is essential. In this paper, we examine the effect of plan parameters on the DQA passing rate and clarify the plan parameters that should be adjusted mainly for each Tomotherapy when DQA fails and re-planning is required. Two versions of Tomotherapy treatment machines, Tomotherapy Hi-art and Radixact X9, were used. An independent t-test was performed to confirm the significant difference between the DQA passing rates of Tomotherapy Hi-art and Radixact X9. Also, a regression analysis was performed to analyze the correlation between plan parameters and passing rates. The average passing rate for Radixact X9 was 99.82 (standard deviation [SD] = 0.32) and that for Tomotherapy Hi-art was 98.46 (SD = 1.76). The passing rate of Radixact X9 was significantly higher than that of Tomotherapy Hi-art (P = 0.000). Statistically significant independent variables adopted from Tomotherapy Hi-art were IEC Yf (p = 0.025), the modulation factor (p = 0.003), and the number of control points (p = 0.006). The statistically significant parameter for Radixact X9 was IEC Xf (p = 0.000). According to the results, the new version of Tomotherapy(Radixact X9) has a relatively higher DQA pass rate than the old version (Tomotherapy Hi-art), and if the DQA fails and re-planning is required, each of the plan parameters can be adjusted to achieve a higher pass rate.
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- 2019
22. Fluence-weighted average subfield size in helical TomoTherapy
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Hilke Vorwerk, Andrea Wittig, Klemens Zink, Simon Howitz, and Tilo Wiezorek
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Male ,Field (physics) ,medicine.medical_treatment ,Biophysics ,Fluence ,Square (algebra) ,Tomotherapy ,Imaging phantom ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Range (statistics) ,medicine ,Humans ,Dosimetry ,Radiology, Nuclear Medicine and imaging ,Mathematics ,Radiological and Ultrasound Technology ,Mathematical analysis ,Prostatic Neoplasms ,Radiotherapy Dosage ,Modulation factor ,Head and Neck Neoplasms ,Radiotherapy, Intensity-Modulated ,Organ Sparing Treatments ,Software - Abstract
Introduction Helical TomoTherapy allows a highly conformal dose distribution to complex target geometries with a good protection of organs at risk. However, the small field sizes associated with this method are a possible source of dosimetrical uncertainties. The IAEA has published detector-specific field output correction factors for static fields of the TomoTherapy in the TRS483. This work investigates the average subfield size of helical TomoTherapy plans. Material and methods A new parameter for helical TomoTherapy was defined – the fluence-weighted average subfield size. The subfield sizes were extracted from the leaf-opening time sinograms in the RT-plan files for 30 clinical prostate and head and neck plans and were put in relation to Delat4 Phantom+ measurement results. Additionally the influence of planning parameters on the subfield size was studied by varying the modulation factor, number of iterations and pitch in the dose optimization and calculation for three different clinical indications H&N, prostate and rectum cancer . Selected plans were dosimetrically verified by Delta4 measurements to examine the reliability in dependence of the average subfield size. Furthermore, the impact of the planning parameters on a) the dose distribution, with regard to the planning target volume and regions at risks, and b) machine characteristics such as delivery time, actual modulation factor and leaf-opening times were evaluated. Results The average equivalent square subfield lengths ( s ¯ e q ) of the two investigated indications did not differ significantly – prostate plans: 2.75 ± 0.14 cm and H&N plans: 2.70 ± 0.16 cm, both with a jaw width of 2.5 cm. No correlation between field size and measured dose deviation was detected. The number of iterations and the modulation factor have a considerable influence on the average subfield size. The higher the planned modulation factor and the more iterations are used during optimization, the smaller is the subfield size. In our pilot study plans were calculated with field sizes s ¯ e q between 4.2 cm and 1.7 cm, with a jaw width of 2.5 cm. Again, the measurement results of Delta4 showed no significant deviation from the doses calculated by the TomoTherapy planning system for the whole range of subfield sizes, and no significant correlation between field sizes and dose deviations was found. As expected, the clinical dose distribution improved with increasing modulation factor and an increasing number of iterations. The compromise between an improved dose distribution and smaller s ¯ e q was shown. Conclusion In this work, a method was presented to determine the average subfield size for helical TomoTherapy plans. The response of the Delta4 did not show any dependence on field size in the range of the field sizes covered by the studied plans. The influence of the subfield sizes on other dosimetry systems remains to be investigated.
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- 2019
23. Clinical implementation of low-dose total body irradiation using topotherapy technique
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Selli Simone, G. Salvadori, Andrea Assanelli, Anna Chiara, Fabio Ciceri, Marcella Pasetti, Jacopo Peccatori, Sara Broggi, Nadia Di Muzio, Riccardo Calandrino, Simona Piementose, Claudio Fiorino, Broggi, S., Fiorino, C., Chiara, A., Salvadori, G., Peccatori, J., Assanelli, A., Piementose, S., Pasetti, M., Simone, S., Ciceri, F., Di Muzio, N. G., and Calandrino, R.
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lcsh:Medical physics. Medical radiology. Nuclear medicine ,lcsh:R895-920 ,Planning target volume ,lcsh:RC254-282 ,030218 nuclear medicine & medical imaging ,Dose homogeneity ,03 medical and health sciences ,0302 clinical medicine ,Tomotherapy, Automatic planning ,TBI ,Radiology, Nuclear Medicine and imaging ,Original Research Article ,Mathematics ,Radiation ,business.industry ,Low dose ,Total body irradiation ,lcsh:Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,Modulation factor ,TomoDirect ,030220 oncology & carcinogenesis ,Treatment time ,Nuclear medicine ,business ,Quality assurance - Abstract
Background and Purpose: The topotherapy technique was recently suggested as a robust alternative to helical radiation delivery for total body irradiation (TBI). It allows to deliver a discrete number of beams with fixed gantry. A Topotherapy-based low-dose TBI technique was optimized and clinically implemented. Materials and methods: TBI delivery was split in two parts: the first treating from the head to half thigh and the second the remaining legs. An in-silico investigation aimed to optimize plan parameters was first carried out on four patients. For the upper plan, field width and pitch were fixed to 5 cm and 0.5: the combined impact of five modulation factor (MF) values and different field configurations (6/8/12 fields) was investigated. For the lower plan, two anterior/posterior beams (field width: 5 cm; pitch: 0.5; MF:1.5) were used. After assessing the optimal technique, set-up/quality assurance/image-guidance procedures were defined and the technique clinically implemented: 23 patients were treated up to now. Results: The best compromise between treatment time and planning target volume (PTV) coverage/homogeneity was found for MF = 1.5 and 8 fields. All clinical plans were automatically optimized using an “ad-hoc” plan template: excellent PTV coverage (PTV95%>98.5%) and homogeneity (median SD:4%) were found with a median beam-on time of 17/9 min for the upper/lower plan. All patients were successfully treated and transplanted. Conclusions: TBI delivered with the topotherapy approach robustly guarantees adequate coverage and dose homogeneity. Semi-automatic clinical plans can be quickly generated and efficiently delivered. Keywords: TBI, TomoDirect, Tomotherapy, Automatic planning
- Published
- 2019
24. Power and Phase Variation of Backscattered RFID Signal with Respect to the Incident Power at the Tag
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Spyros Megalou, Aggelos Bletsas, Antonis G. Dimitriou, and Traianos V. Yioultsis
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Phase variation ,Physics ,Modulation factor ,RFID tag ,Phase ,Acoustics ,Passive RFID ,RSSI ,Signal ,Power (physics) - Abstract
Summarization: In this paper, we investigate how the incident power at the tag affects the backscattered signal that reaches the reader. It is shown experimentally and theoretically that the backscattered complex signal, i.e. magnitude and phase, changes significantly with respect to the incident power at the tag’s antenna. This effect is neglected in prior art and is due to the change of the input impedance of the tag’s front end, due to the presence of non-linear components, like the rectifier’s diodes. Measured deviation of 14dBs and phase shift of 100 degrees is reported herein. These variations might lead to large localization errors, depending on the method and the measured quantity, unless the localization algorithm accounts for the expected variability. Παρουσιάστηκε στο: 2021 IEEE International Conference on RFID Technology and Applications
- Published
- 2021
25. Influence of Modulation Factor on Treatment Plan Quality and Irradiation Time in Hippocampus-Sparing Whole-Brain Radiotherapy Using Tomotherapy
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Hiromasa Kurosaki, Hideyuki Sakurai, Akihiko Ishibashi, Kosei Miura, and Nobuko Utsumi
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tilt heading ,Cancer Research ,hippocampus-sparing ,Time Factors ,medicine.medical_treatment ,tomotherapy ,Hippocampus ,Irradiation time ,Dose distribution ,Radiation Dosage ,whole-brain radiotherapy ,Patient Positioning ,Tomotherapy ,Treatment plan ,brain metastases ,Humans ,Medicine ,Radiation Injuries ,RC254-282 ,Brain Neoplasms ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Whole brain radiotherapy ,Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,Modulation factor ,Radiation therapy ,Oncology ,Original Article ,Radiotherapy, Intensity-Modulated ,Cranial Irradiation ,Tomography, X-Ray Computed ,Nuclear medicine ,business ,Organ Sparing Treatments - Abstract
Objectives: Hippocampus-sparing whole-brain radiotherapy (HS-WBRT) using tomotherapy is known to provide a better dose distribution than volumetric-modulated arc therapy but requires an extended irradiation time. The present study aimed to investigate whether irradiation time can be shortened by reducing the modulation factor (MF) without losing the target dose distribution. Methods: Using six tilted computed tomography images in the head area, the planning target volume (PTV) and hippocampal doses, and the irradiation time was investigated with a jaw width of 1 cm, a pitch of 0.200, and the MF changed from 3.0 to 2.6, 2.2, 1.8, and 1.4. Results: No significant changes in the PTV or hippocampus were found with MF in the range from 3.0 to 1.8, but marked deterioration was found with that of 1.4. The irradiation time showed a linear relationship with the MF within the range from 3.0 to 1.8, with 1334, 1158, 986, and 817 s at modulation factors of 3.0, 2.6, 2.2, and 1.8, respectively. However, when the MF was 1.4, the irradiation time was 808 s. Conclusions: When HS-WBRT is performed with a tilted body position and a jaw width of 1 cm, with a MF of 1.8, a favorable balance between dose parameters and irradiation time is achieved, whereas with a MF of 1.4, the quality of the radiotherapy plan deteriorates, and the irradiation time is approximately the same as that with a MF of 1.8.
- Published
- 2021
26. Quantitative evaluation of micro-cracks using nonlinear ultrasonic modulation method.
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Li, Nan, Sun, Junjun, Jiao, Jingpin, Wu, Bin, and He, Cunfu
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- *
MICROCRACKS , *NONLINEAR acoustics , *STRUCTURAL health monitoring , *CRACK propagation (Fracture mechanics) , *RELIABILITY in engineering - Abstract
Nonlinear acoustic coefficients have a close relationship with structural cracks. A nonlinear ultrasonic modulation method for micro-crack quantitative evaluation is developed. The influence of phase threshold on the crack evaluation is discussed. Ultrasonic modulation using a unilateral incentive model is applied to the quantitative evaluation of micro-cracks for different specimens. The experimental results indicate that the method can be beneficially applied for micro-cracks detection. A proper phase threshold can improve the reliability of the method based on nonlinear ultrasonic modulation. The presented modulation factor can be used to quantitatively evaluate the structural cracks, and it is suitable for small-crack quantitative evaluation. [ABSTRACT FROM AUTHOR]
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- 2016
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27. Stress response as implemented by hibernating ribosomes: a structural overview
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Anat Bashan, Mee-Ngan Frances Yap, Donna Matzov, and Ada Yonath
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Ribosomal Proteins ,0301 basic medicine ,Cell Survival ,Protein Conformation ,Dimer ,Biochemistry ,Ribosome ,Fight-or-flight response ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Hibernation ,Protein biosynthesis ,Structural Snapshot ,single particle cryo‐EM ,Molecular Biology ,100S ,biology ,Chemistry ,Mechanism (biology) ,Escherichia coli Proteins ,Cryoelectron Microscopy ,Cell Biology ,Ribosomal RNA ,biology.organism_classification ,Modulation factor ,030104 developmental biology ,ribosome ,Protein Biosynthesis ,030220 oncology & carcinogenesis ,Biophysics ,Energy Metabolism ,Dimerization ,Ribosomes ,Gammaproteobacteria ,Bacteria ,Protein Binding - Abstract
Protein synthesis is one of the most energy demanding cellular processes. The ability to regulate protein synthesis is essential for cells under normal as well as stress conditions, such as nutrient deficiencies. One mechanism for protein synthesis suppression is the dimerization of ribosomes into hibernation complexes. In most cells, this process is promoted by the hibernating promoting factor (HPF) and in a small group of Gram-negative bacteria (γ-proteobacteria), the dimer formation is induced by a shorter version of HPF (HPFshort ) and by an additional protein, the ribosome modulation factor. In most bacteria, the product of this process is the 100S ribosome complex. Recent advances in cryogenic electron microscopy methods resulted in an abundance of detailed structures of near atomic resolutions 100S complexes that allow for a better understanding of the dimerization process and the way it inhibits protein synthesis. As ribosomal dimerization is vital for cell survival, this process is an attractive target for the development of novel antimicrobial substances that might inhibit or stabilize the complex formation. As different dimerization processes exist among bacteria, including pathogens, this process may provide the basis for species-specific design of antimicrobial agents. Here, we review in detail the various dimerization mechanisms and discuss how they affect the overall dimer structures of the bacterial ribosomes.
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- 2019
28. Determining efficient helical IMRT modulation factor from the MLC leaf‐open time distribution on precision treatment planning system
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Wolfgang A. Tomé, Robert Boyd, and Kyoungkeun Jeong
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Male ,Accuracy and precision ,Mathematical optimization ,treatment planning ,Computer science ,Genital Neoplasms, Female ,medicine.medical_treatment ,tomotherapy ,leaf‐open time ,Plan (drawing) ,Tomotherapy ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Region of interest ,Acceptance testing ,medicine ,Range (statistics) ,Radiation Oncology Physics ,Humans ,Radiology, Nuclear Medicine and imaging ,Radiation treatment planning ,Instrumentation ,Radiation ,Phantoms, Imaging ,Radiotherapy Planning, Computer-Assisted ,Prostatic Neoplasms ,Radiotherapy Dosage ,Prognosis ,Multileaf collimator ,Head and Neck Neoplasms ,030220 oncology & carcinogenesis ,Female ,Radiotherapy, Intensity-Modulated ,Particle Accelerators ,modulation factor ,Algorithms - Abstract
Purpose Since the modulation factor (MF) impacts both plan quality and delivery efficiency in tomotherapy Intensity Modulated Radiation Therapy (IMRT) treatment planning, the purpose of this study was to demonstrate a technique in determining an efficient MF from the Multileaf Collimator (MLC) leaf-open time (LOT) distribution of a tomotherapy treatment delivery plan. Methods Eight clinical plans of varying complexity were optimized with the highest allowed MF on the Accuracy Precision treatment planning system. Using a central limit theorem argument a range of reduced MFs were then determined from the first two moments of the LOT distribution. A step down approach was used to calculate the reduced-MF plans and plan comparison tools available on the Precision treatment planning system were used to evaluate dose differences with the reference plan. Results A reduced-MF plan that balanced delivery time and dosimetric quality was found from the set of five MFs determined from the LOT distribution of the reference plan. The reduced-MF plan showed good agreement with the reference plan (target and critical organ dose-volume region of interest dose differences were within 1% and 2% of prescription dose, respectively). Discussion Plan evaluation and acceptance criteria can vary depending on individual clinical expectations and dosimetric quality trade-offs. With the scheme presented in this paper a planner should be able to efficiently generate a high-quality plan with efficient delivery time without knowing a good MF beforehand. Conclusion A methodology for deriving a reduced MF from the LOT distribution of a high MF treatment plan using the central limit theorem has been presented. A scheme for finding a reduced MF from a set of MFs that results in a plan balanced in both dosimetric quality and treatment delivery efficiency has also been presented.
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- 2019
29. Evaluation and validation of IBA I'MatriXX array for patient-specific quality assurance of tomotherapy®
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T. Anil Kumar, G Deleep Kumar, B Nagarjuna Reddy, V C Sahithya, G Durga Prasad, N V N Madhusudhana Sresty, S Aparna, A. Krishnam Raju, Tasneem Rushdi, Yakub Mohmd, and Harjot Kaur Bajwa
- Subjects
lcsh:Medical physics. Medical radiology. Nuclear medicine ,medicine.medical_specialty ,Intensity-modulated radiation therapy ,Computer science ,medicine.medical_treatment ,lcsh:R895-920 ,Biophysics ,quality assurance ,Tomotherapy ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Technical Note ,medicine ,Radiology, Nuclear Medicine and imaging ,Medical physics ,business.industry ,2d array ,Patient specific ,Modulation factor ,Distance to agreement ,Radiation therapy ,Gamma index ,030220 oncology & carcinogenesis ,TomoTherapy® ,business ,Quality assurance - Abstract
TomoTherapy® is a modern radiation treatment technique in which intensity-modulated radiation therapy (IMRT) is delivered in helical fashion. A two-dimensional (2D) array which has been existing for IMRT patient-specific quality assurance (PSQA) verifications for many years is I'MatriXX. Our objectives were to validate this I'MatriXX and to evaluate it for different patient sites and fractionation schedules of TomoTherapy treatment. Twenty-five plans were created with virtual target for different possible pitch values and field widths for validation. Gamma index criteria of 3%/2% dose differences and 3/2 mm distance to agreement were used. QA plans of 26 different treatment sites and different fractionation schedules were used. Results indicated that the matrix response is independent of field width, pitch, and modulation factor of TomoTherapy with 3%, 3 mm criteria. High passing rate ranging from 99.7% to 90.7% was observed for selected patient plans. We found that I'MatriXX 2D array can be utilized for easy and quick TomoTherapy PSQA.
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- 2019
30. Research of the adaptive control on modulation factor for <scp>PSR</scp> fly‐back <scp>PSM</scp> converter
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Weiheng Wang, Lei Tian, and Qinqin Li
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Physics ,PSR ,Adaptive control ,General Computer Science ,PSM ,self‐adapting ,lcsh:Electronics ,Mode (statistics) ,Energy balance ,lcsh:TK7800-8360 ,Discontinuous conduction ,fly‐back ,020206 networking & telecommunications ,02 engineering and technology ,energy balance ,lcsh:Telecommunication ,Electronic, Optical and Magnetic Materials ,Modulation factor ,Control theory ,lcsh:TK5101-6720 ,0202 electrical engineering, electronic engineering, information engineering ,020201 artificial intelligence & image processing ,Electrical and Electronic Engineering - Abstract
The energy balance (EB) model of a primary side regulation (PSR) fly‐back converter in the discontinuous conduction mode (DCM) is discussed in this paper. Based on this EB model, the stability of a PSR fly‐back converter in the pulse skipping mode (PSM) is analyzed, and a self‐adapting modulation factor control strategy is proposed. Theoretical analysis and simulation results show that by saving an optocoupler and correlative circuits, which are necessary in traditional PSM fly‐back converters, the modulation factor tolerance controlled by this method is 1.26% on average, corresponding to the ideal value. Compared with traditional fly‐back PSM controllers, the power saved in the sampler/comparator modules is 87% on average for a load range of 1 Ω to 1 kΩ.
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- 2018
31. Effects of modulation factors in breast cancer treatment with helical tomotherapy
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Zincircioğlu, S. B., Doğan, M. H., Dicle Üniversitesi, Tıp Fakültesi, Dahili Tıp Bilimleri Bölümü, Radyasyon Onkolojisi Ana Bilim Dalı, Zincircioğlu, S.B., and Doğan, M.H.
- Subjects
Breast cancer ,Modulation factor ,Irradiation - Abstract
WOS:000649198300002 Background: The aim of this study was to compare the dosimetric values of TomoHelical (TH) plans using modulation factors 3 and 5 in patients with breast cancer. Materials and Methods: Two different radiotherapy treatment plans, including modulation factors 3 and 5, were generated retrospectively for 12 consecutive intact breast cancer patients. Twelve different plans in terms of the modulation factor were generated. Other optimization parameters (i.e., pitch and field width) were the same for all plans. Results: No differences were found between the conformity index (CI) and homogeneity index (HI) values of both plans (p>0.05). The values of D mean, V5, and V20 of the ipsilateral lung in the TomoHelical plan with modulation factor 5 (TH5) were significantly lower than with modulation factor 3 (TH3) for all 12 patients (4.9 Gy, 20.14%, 3.23%. Vs, 10.95 Gy, 58.9%, 18.7%; p=0.01, p=0.00, p=0.002, respectively). Also, the values of Dmean and V5 of the heart in TH5 were significantly lower than in TH3 (6.45 Gy, 34.33%, vs. 7.12 Gy, 64.22%; p=0.004, p=0.00, respectively). Conclusion: Both the TH5 and TH3 plans provided adequate coverage of the intact breast. TH5 delivered a decreased dose to the ipsilateral organs at risk (OARs), especially in the lung and heart volume, which is the main cause of long-term toxicity. The novelty of this work is the obvious reduction in same-sided lung volume irradiation by increasing the modulation factor.
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- 2021
32. The optimal tomotherapy treatment planning parameters for extremity soft tissue sarcomas.
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Meyer, Philippe, Bouhours, Hugo, Dehaynin, Nicolas, Jarnet, Delphine, Gantier, Matthieu, Karamanoukian, Diran, and Niederst, Claudine
- Abstract
Background and purpose To determine the optimum combination of treatment parameters between pitch, field width (FW) and modulation factor (MF) for extremity sarcomas in tomotherapy. Materials and methods Six patients previously treated for extremity sarcomas (3 arms and 3 legs) with tomotherapy were included in this study. 288 treatment plans were recalculated, corresponding to all combinations between 2 FW (2.5 and 5 cm), 4 MF (1.5, 2, 2.5 and 3) and 6 pitches (0.215, 0.287, 0.43 and 3 off-axis pitches). The treatment parameters (MF, FW or pitch) are modified between each plan, and the calculation is relaunched for 400 iterations, without modifying the optimisation constraints of the plan under which the patient has been treated. Results We suggest eliminating the 0.43 pitch and never combining a 0.215 pitch with an MF ≤ 2. We also do not recommend using an MF = 1.5 unless treatment time is an absolute priority over plan quality. We did not see any advantage in using Chen off-axis pitches, except for targets far from the axis (>15 cm) treated with a high pitch. A combination of MF = 2/FW = 5 cm/pitch = 0.287 gives plans of acceptable quality, combined with reduced treatment times. These conclusions are true only for extremity sarcomas treated in 2 Gy/fraction. Conclusions We have shown that the choice of pitch/MF/FW combination is crucial for the treatment of extremity sarcomas in tomotherapy: some produce good dosimetric quality with a reduced irradiation time, while others may increase the time without improving the quality. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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33. Leaf open time sinogram (LOTS): a novel approach for patient specific quality assurance of total marrow irradiation
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Srinivas Chilukuri, Suryakant Kaushik, Rakesh Jalali, Rangasamy Sivaraman, D. Sharma, K. Ganapathy, Rajesh Thiyagarajan, Kartikeswar Ch. Patro, Manthala Padannayil Noufal, Mayur Sawant, Jose Easow, N. Arunai Nambi Raj, S. Sundar, and A Manikandan
- Subjects
lcsh:Medical physics. Medical radiology. Nuclear medicine ,Patient-Specific Modeling ,medicine.medical_treatment ,lcsh:R895-920 ,lcsh:RC254-282 ,Tomotherapy ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Planned Dose ,Total marrow irradiation ,Helical tomotherapy ,Bone Marrow ,MVCT ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Dose Reconstruction ,Patient specific QA ,Radiometry ,Exit dosimetry ,Upper body ,business.industry ,Phantoms, Imaging ,Research ,Radiotherapy Planning, Computer-Assisted ,Reproducibility of Results ,Radiotherapy Dosage ,Total Marrow Irradiation ,Patient specific ,Cone-Beam Computed Tomography ,lcsh:Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,Reconstruction method ,Modulation factor ,Oncology ,030220 oncology & carcinogenesis ,Sinogram ,Radiotherapy, Intensity-Modulated ,business ,Nuclear medicine ,Quality assurance ,Whole-Body Irradiation - Abstract
There is no ideal detector-phantom combination to perform patient specific quality assurance (PSQA) for Total Marrow (TMI) and Lymphoid (TMLI) Irradiation plan. In this study, 3D dose reconstruction using mega voltage computed tomography detectors measured Leaf Open Time Sinogram (LOTS) was investigated for PSQA of TMI/TMLI patients in helical tomotherapy. The feasibility of this method was first validated for ten non-TMI/TMLI patients, by comparing reconstructed dose with (a) ion-chamber (IC) and helical detector array (ArcCheck) measurement and (b) planned dose distribution using 3Dγ analysis for 3%@3mm and dose to 98% (D98%) and 2% (D2%) of PTVs. Same comparison was extended for ten treatment plans from five TMI/TMLI patients. In all non-TMI/TMLI patients, reconstructed absolute dose was within ± 1.80% of planned and IC measurement. The planned dose distribution agreed with reconstructed and ArcCheck measured dose with mean (SD) 3Dγ of 98.70% (1.57%) and 2Dγ of 99.48% (0.81%). The deviation in D98% and D2% were within 1.71% and 4.10% respectively. In all 25 measurement locations from TMI/TMLI patients, planned and IC measured absolute dose agreed within ± 1.20%. Although sectorial fluence verification using ArcCHECK measurement for PTVs chest from the five upper body TMI/TMLI plans showed mean ± SD 2Dγ of 97.82% ± 1.27%, the reconstruction method resulted poor mean (SD) 3Dγ of 92.00% (± 5.83%), 64.80% (± 28.28%), 69.20% (± 30.46%), 60.80% (± 19.37%) and 73.2% (± 20.36%) for PTVs brain, chest, torso, limb and upper body respectively. The corresponding deviation in median D98% and D2% of all PTVs were 98% and D2%
- Published
- 2020
34. Evaluation of Optimal Combination of Planning Parameters (Field Width, Pitch, and Modulation Factor) in Helical Tomotherapy for Bilateral Breast Cancer
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A Pichandi, TK Bijina, and CA Muthuselvi
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business.industry ,medicine.medical_treatment ,Homogeneity (statistics) ,Biophysics ,helical tomotherapy ,Bilateral breast cancer ,Tomotherapy ,Modulation factor ,Conformity index ,planning parameters ,Organ at risk ,medicine ,Optimal combination ,Radiology, Nuclear Medicine and imaging ,Original Article ,Nuclear medicine ,business ,Mathematics ,Homogeneity index - Abstract
Aim: The aim of the study was to find the most balanced plan with an optimal combination of planning parameters in helical tomotherapy (HT) for bilateral breast irradiation by evaluating dosimetric indices and time factors. In particular, we investigated the best combination of field width (FW), pitch, and modulation factor (MF). Materials and Methods: A total of 90 plans (18 plans for each patient) was created in this study, with different combination of planning parameters (FW: 2.5 cm [F1] and 5 cm [F2]; pitch: 0.215 [P1], 0.287 [P2], and 0.43 [P3]; and MF: 2.0 [M1], 2.5 [M2], and 3.0 [M3]). Plans were analyzed using several dosimetric indices: homogeneity index, conformity index, dose near minimum D98%, dose near maximum D2%, and the coverage by D95% of the target. Organ at risk (OAR) doses were evaluated by mean dose, V5Gy and V25Gy for the heart and mean dose V5Gy and V20Gy for both the lungs. Treatment time was also reported for all plans. Results: Reducing FW from 5 cm to 2.5 cm increased the treatment time by 40%–50% and improved homogeneity of the target. Tightening the pitch value from 0.43 to 0.215 improved target as well as OAR doses without increasing the treatment time. Increasing MF from 2 to 3 improved all the dosimetric indices and also increased treatment time. Conclusions: On the basis of our analysis, a plan with FW 5 cm, pitch 0.215, and MF 2.5 can be considered as an optimal combination of planning parameters for bilateral breast irradiation in HT technique.
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- 2020
35. Terahertz Single-Pixel Imaging Improved by Using Silicon Wafer with SiO2 Passivation
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Guanglu Wei, Rongbin She, Guangyuan Li, Lu Yuanfu, and Liu Wenquan
- Subjects
Materials science ,Passivation ,Silicon ,Terahertz radiation ,chemistry.chemical_element ,02 engineering and technology ,01 natural sciences ,lcsh:Technology ,010309 optics ,lcsh:Chemistry ,0103 physical sciences ,General Materials Science ,Wafer ,passivation ,Instrumentation ,terahertz single-pixel imaging ,lcsh:QH301-705.5 ,compressed sensing ,Fluid Flow and Transfer Processes ,business.industry ,lcsh:T ,Process Chemistry and Technology ,General Engineering ,021001 nanoscience & nanotechnology ,lcsh:QC1-999 ,Computer Science Applications ,Modulation factor ,Single pixel ,Compressed sensing ,chemistry ,lcsh:Biology (General) ,lcsh:QD1-999 ,lcsh:TA1-2040 ,Optoelectronics ,0210 nano-technology ,business ,photomodulation ,lcsh:Engineering (General). Civil engineering (General) ,lcsh:Physics - Abstract
We demonstrate terahertz single-pixel imaging is improved by using a photomodulator based on silicon passivated with SiO 2 . By exploring various SiO 2 thicknesses, we show that the modulation factor of the as-fabricated terahertz photomodulator can reach 0.9, three times that based on bare silicon. This improvement originates from chemical passivation, as well as anti-reflection. Single-pixel imaging experiments based on the compressed sensing method show that reconstructed images adopting the new photomodulator have better quality than the conventional terahertz modulator based on bare silicon. Since the passivation process is routine and low cost, we expect this work will reduce the cost of terahertz photomodulator and single-pixel THz imaging, and advance their applications.
- Published
- 2020
36. Infl uence of the modulation factor on the treatment plan quality and execution time in Tomotherapy in head and neck cancer: In-phantom study.
- Author
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Ryczkowski, Adam and Piotrowski, Tomasz
- Subjects
- *
HEAD & neck cancer treatment , *IMAGING phantoms , *DRUG dosage , *RADIOTHERAPY treatment planning , *CANCER radiotherapy - Abstract
Purpose: The overall aim was to conduct an analytical study of the impact of the modulation factor (MF) on the quality of the head and neck treatment plans and their execution time on Tomotherapy. Materials and Methods: In-phantom (RANDO® Alderson) planning study of the head and neck cancer was performed. Thirteen different plans in terms of MF were prepared. Other optimization parameters were the same for all plans. Results: Analysis of treatment plans in terms of quality shows that MF < 1.4 does not provide an accepted dose distribution (physician decision). Statistically significant differences were observed for plans with an MF < 1.6. No differences were obtained for plans with MF from 6.0 to 1.8. Decreasing of MF leads to a shorter time of irradiation. The maximum rotational speed has been reached for an MF = 3.0. Further reducing this however produces no decrease in the time of irradiation. The actual and planned values of the MF were compared. The optimal range of MF for head and neck was determined as 3.0 > MF > 1.8. The lower limit increases to 2.4 when hard reduction of the dose in critical organs is required. Conclusions: It was showed that the final MF value is less than the value calculated after each loop of optimization. The computer system reduces MF by shortening the longest time and increasing the average time of leaves opening. Increase in the average time is obtained by eliminating the use of leafs with the shortest times of opening, thereby reducing the dose in critical organs that are outside the direct irradiation area. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
37. ppGpp ribosome dimerization model for bacterial persister formation and resuscitation
- Author
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Sooyeon Song and Thomas K. Wood
- Subjects
0301 basic medicine ,Ribosomal Proteins ,Resuscitation ,Multidrug tolerance ,Biophysics ,Guanosine Tetraphosphate ,Biochemistry ,Ribosome ,Models, Biological ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Stress, Physiological ,Escherichia coli ,Guanosine pentaphosphate ,Molecular Biology ,biology ,Chemistry ,Escherichia coli Proteins ,Cell Biology ,biology.organism_classification ,Modulation factor ,Cell biology ,030104 developmental biology ,030220 oncology & carcinogenesis ,Dimerization ,Ribosomes ,Bacteria ,Alarmone - Abstract
Stress is ubiquitous for bacteria and can convert a subpopulation of cells into a dormant state known as persistence, in which cells are tolerant to antimicrobials. These cells revive rapidly when the stress is removed and are likely the cause of many recurring infections such as those associated with tuberculosis, cystic fibrosis, and Lyme disease. However, how persister cells are formed is not understood well. Here we propose the ppGpp ribosome dimerization persister (PRDP) model in which the alarmone guanosine pentaphosphate/tetraphosphate (henceforth ppGpp) generates persister cells directly by inactivating ribosomes via the ribosome modulation factor (RMF), the hibernation promoting factor (Hpf), and the ribosome-associated inhibitor (RaiA). We demonstrate that persister cells contain a large fraction of 100S ribosomes, that inactivation of RMF, HpF, and RaiA reduces persistence and increases single-cell persister resuscitation and that ppGpp has no effect on single-cell persister resuscitation. Hence, a direct connection between ppGpp and persistence is shown along with evidence of the importance of ribosome dimerization in persistence and for active ribosomes during resuscitation.
- Published
- 2019
38. Interfacility variation in treatment planning parameters in tomotherapy: field width, pitch, and modulation factor
- Author
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Takahiro Aoyama, Koji Sasaki, Takeshi Kodaira, Hiroshi Fukuma, Hidetoshi Shimizu, Takashi Kubota, Tohru Iwata, and Hiroyuki Tachibana
- Subjects
Male ,Health, Toxicology and Mutagenesis ,medicine.medical_treatment ,Dose distribution ,Data submission ,Time based ,Dose per fraction ,Tomotherapy ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Japan ,Surveys and Questionnaires ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Radiation treatment planning ,Mathematics ,Internet ,Radiation ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Prostatic Neoplasms ,Reproducibility of Results ,Radiotherapy Dosage ,Modulation factor ,Radiation therapy ,Head and Neck Neoplasms ,030220 oncology & carcinogenesis ,Radiotherapy, Intensity-Modulated ,Nuclear medicine ,business - Abstract
Several studies have reported changes in dose distribution and delivery time based on the value of specific planning parameters [field width (FW), pitch, and modulation factor (MF)] in tomotherapy. However, the variation in the parameters between different facilities is unknown. The purpose of this study was to determine standard values of the above parameters for cases of head and neck cancer (HNC) and prostate cancer (PC) in Japan. In this survey, a web-based questionnaire was sent to 48 facilities performing radiation therapy with tomotherapy in March 2016. The deadline for data submission was April 2016. In the questionnaire, the values of the planning parameters usually used were requested and 23 responses were received, representing a response rate of 48% (23/48). The FW selected was 2.5 cm in most facilities, and facilities with a tomoEDGE license used dynamic FW rather than fixed FW. Facilities changed the pitch based on FW, dose per fraction, or target offset more frequently in HNC than in PC. In contrast, >50% of the facilities used the magic number proposed by Kissick et al. Median preset MFs (range, min to max) in HNC and PC were 2.4 (1.8-2.8) and 2.0 (1.8-3.0), respectively, and MF values showed large variations between the facilities. Our results are likely to be useful to several facilities designing treatment plans in tomotherapy.
- Published
- 2018
39. Catalyst Replacement Policy on Multienzymatic Systems: Theoretical Study in the One-Pot Sequential Batch Production of Lactofructose Syrup
- Author
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Lorena Wilson, Vanessa Arancibia, Pablo Silva, Daniela Cid, Andrés Illanes, and Oscar Romero
- Subjects
Glucose-6-phosphate isomerase ,Immobilized enzyme ,one-pot ,Kinetics ,β-galactosidase ,TP1-1185 ,Sequential batch ,Catalysis ,Modulation factor ,Glucose isomerase ,Physical and Theoretical Chemistry ,QD1-999 ,Multi-enzymatic reactions ,One-pot ,chemistry.chemical_classification ,Chemical technology ,sequential batch ,lactofructose syrup ,Chemistry ,Enzyme ,multi-enzymatic reactions ,catalyst replacement policy ,chemistry ,Chemical engineering ,Biocatalysis ,Catalyst replacement policy ,Lactofructose syrup ,glucose isomerase ,Batch production ,modulation factor - Abstract
One-pot systems are an interesting proposal to carry out multi-enzymatic reactions, though this strategy implies establishing an optimal balance between the activity and operability of the involved enzymes. This is crucial for enzymes with marked differences in their operational stability, such as one-pot production of lactofructose syrup from cheese whey permeate, which involves two enzymes—β-galactosidase (β-gal) and glucose isomerase (GI). The aim of this work was to study the behavior of one-pot sequential batch production of lactofructose syrup considering both enzymes immobilized individually, in order to evaluate and design a strategy of replacement of the catalysts according to their stabilities. To this end, the modelling and simulation of the process was carried out, considering simultaneously the kinetics of both reactions and the kinetics of inactivation of both enzymes. For the latter, it was also considered the modulating effect that sugars present in the medium may have on the stability of β-gal, which is the less stable enzyme. At the simulated reaction conditions of 40 °C, pH 7, and 0.46 (IUGI/IUβ-gal), the results showed that considering the stability of β-gal under non-reactive conditions, meaning in absence of the effect of modulation, it is necessary to carry out four replacements of β-gal for each cycle of use of GI. On the other hand, when considering the modulation caused by the sugars on the β-gal stability, the productivity increases up to 23% in the case of the highest modulation factor studied (η = 0.8). This work shows the feasibility of conducting a one-pot operation with immobilized enzymes of quite different operational stability, and that a proper strategy of biocatalyst replacement increases the productivity of the process.
- Published
- 2021
40. Extension of the cumulant definition for low particle number systems.
- Author
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Kong, Liguo
- Subjects
- *
CUMULANTS , *DENSITY matrices , *QUANTUM chemistry , *APPROXIMATION theory , *PARTICLES , *CHEMICAL systems - Abstract
Cumulants are usually interpreted as the connected components of density matrices, but this interpretation fails and practical problems arise when the rank n of cumulants is larger than the number of particles ( N) in the system. In that case, cumulants defined in the traditional way become disconnected. To solve this problem, the definition of cumulants is extended by introducing a simple modulation factor. The modified cumulants reduce to the conventional definition, but they vanish when N < n. Using the modified definition also eliminates the error in the approximation of density matrices by low-rank cumulants, when N < n. The problem assumes a slightly different form when we work with active space-based theories, and it can be solved by a similar approach. Another problem with cumulants, due to spin coupling [Herbert, Int J Quantum Chem 2007, 107, 703], can be solved via the introduction of a similar modulation factor. A related yet more serious issue, termed as the local particle number constraint problem, is also discussed. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
41. APOE ϵ4: A Potential Modulation Factor in Rett Syndrome.
- Author
-
Zahorakova, Daniela, Jachymova, Marie, Kemlink, David, Baxova, Alice, and Martasek, Pavel
- Subjects
- *
RETT syndrome , *X-linked intellectual disabilities , *APOLIPOPROTEIN E , *CARRIER proteins , *GENETIC mutation , *MEDICAL genetics - Abstract
Rett syndrome is a neurodevelopmental disorder mainly caused by de novo mutations in the MECP2 (methyl-CpG-binding protein 2) gene. There is considerable variation in the severity of clinical features among Rett syndrome patients, even among patients with the same MECP2 mutation. In addition to X-chromosome inactivation pattern, the genetic background of the affected individual might also have a role in determining the severity of the disorder. We suggest that APOE is one of the genetic modulating factors. We analyzed clinical phenotypes of 46 patients with Rett syndrome, with confirmed MECP2 mutation. We discovered that among ϵ4 carriers, some clinical features were more severe, and the developmental regression occurred 4 months earlier on average than in those without the ϵ4 allele. Earlier onset of regression suggests a possible trend; however, it did not achieve distinctive statistical significance. Nevertheless, the ϵ4 allele of APOE may serve as a candidate modulation factor for the Rett syndrome phenotype. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
42. Catalyst Replacement Policy on Multienzymatic Systems: Theoretical Study in the One-Pot Sequential Batch Production of Lactofructose Syrup.
- Author
-
Silva, Pablo, Arancibia, Vanessa, Cid, Daniela, Romero, Oscar, Illanes, Andrés, and Wilson, Lorena
- Subjects
- *
IMMOBILIZED enzymes , *SYRUPS , *ISOMERASES , *CATALYSTS , *CHEMICAL kinetics , *ENZYMES , *BIOCATALYSIS - Abstract
One-pot systems are an interesting proposal to carry out multi-enzymatic reactions, though this strategy implies establishing an optimal balance between the activity and operability of the involved enzymes. This is crucial for enzymes with marked differences in their operational stability, such as one-pot production of lactofructose syrup from cheese whey permeate, which involves two enzymes—β-galactosidase (β-gal) and glucose isomerase (GI). The aim of this work was to study the behavior of one-pot sequential batch production of lactofructose syrup considering both enzymes immobilized individually, in order to evaluate and design a strategy of replacement of the catalysts according to their stabilities. To this end, the modelling and simulation of the process was carried out, considering simultaneously the kinetics of both reactions and the kinetics of inactivation of both enzymes. For the latter, it was also considered the modulating effect that sugars present in the medium may have on the stability of β-gal, which is the less stable enzyme. At the simulated reaction conditions of 40 °C, pH 7, and 0.46 (IUGI/IUβ-gal), the results showed that considering the stability of β-gal under non-reactive conditions, meaning in absence of the effect of modulation, it is necessary to carry out four replacements of β-gal for each cycle of use of GI. On the other hand, when considering the modulation caused by the sugars on the β-gal stability, the productivity increases up to 23% in the case of the highest modulation factor studied (η = 0.8). This work shows the feasibility of conducting a one-pot operation with immobilized enzymes of quite different operational stability, and that a proper strategy of biocatalyst replacement increases the productivity of the process. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
43. Analysis of modulation factor to shorten the delivery time in helical tomotherapy
- Author
-
Tohru Iwata, Takeshi Kodaira, Koji Sasaki, Kuniyasu Nakashima, Hiroyuki Tachibana, Natsuo Tomita, Hidetoshi Shimizu, Takashi Kubota, Manabu Yoshimoto, Kazushi Yokoi, and Chiyoko Makita
- Subjects
Male ,medicine.medical_specialty ,Time Factors ,medicine.medical_treatment ,Dose distribution ,Tomotherapy ,030218 nuclear medicine & medical imaging ,head and neck ,03 medical and health sciences ,Prostate cancer ,0302 clinical medicine ,Treatment plan ,Prostate ,87.53.Tf ,medicine ,Radiation Oncology Physics ,Humans ,Radiology, Nuclear Medicine and imaging ,Head and neck ,Instrumentation ,prostate ,Radiation ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Head and neck cancer ,helical tomotherapy ,Prostatic Neoplasms ,Radiotherapy Dosage ,delivery time ,medicine.disease ,Surgery ,Modulation factor ,medicine.anatomical_structure ,Head and Neck Neoplasms ,030220 oncology & carcinogenesis ,Radiotherapy, Intensity-Modulated ,business ,Nuclear medicine ,Tomography, Spiral Computed ,modulation factor - Abstract
A low modulation factor (MF) maintaining a good dose distribution contributes to the shortening of the delivery time and efficiency of the treatment plan in helical tomotherapy. The purpose of this study was to reduce the delivery time using initial values and the upper limit values of MF. First, patients with head and neck cancer (293 cases) or prostate cancer (181 cases) treated between June 2011 and July 2015 were included in the analysis of MF values. The initial MF value (MF initial) was defined as the average MF actual value, and the upper limit of the MF value (MFUL) was defined according the following equation: MFUL = 2 × standard deviation of MF actual value + the average MF actual Next, a treatment plan was designed for patients with head and neck cancer (62 cases) and prostate cancer (13 cases) treated between December 2015 and June 2016. The average MF actual value for the nasopharynx, oropharynx, hypopharynx, and prostate cases decreased from 2.1 to 1.9 (p = 0.0006), 1.9 to 1.6 (p < 0.0001), 2.0 to 1.7 (p < 0.0001), and 1.8 to 1.6 (p = 0.0004) by adapting the MF initial and the MFUL values, respectively. The average delivery time for the nasopharynx, oropharynx, hypopharynx, and prostate cases also decreased from 19.9 s cm−1 to 16.7 s cm−1 (p < 0.0001), 15.0 s cm−1 to 13.9 s cm−1 (p = 0.025), 15.1 s cm−1 to 13.8 s cm−1 (p = 0.015), and 23.6 s cm−1 to 16.9 s cm−1 (p = 0.008) respectively. The delivery time was shortened by the adaptation of MF initial and MFUL values with a reduction in the average MF actual for head and neck cancer and prostate cancer cases.
- Published
- 2017
44. Results of a 10‐year survey of workload for 10 treatment vaults at a high‐throughput comprehensive cancer center
- Author
-
Brian T. Quinn, James Mechalakos, J Jeong, Jean St. Germain, Ziad Saleh, and Lawrence T. Dauer
- Subjects
Radiation Protection & Regulations ,Time Factors ,87.55.N, 87.52.-g, 87.52.Df, 87.52.Tr ,Workload ,Cancer Care Facilities ,Gantry angle ,radiation safety ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Surveys and Questionnaires ,Medicine ,Humans ,Scattering, Radiation ,Radiology, Nuclear Medicine and imaging ,Leakage radiation ,Linear Accelerators (Linacs) ,Instrumentation ,Medical systems ,Radiation ,business.industry ,Truebeam ,Conventional treatment ,Isocenter ,shielding design ,3. Good health ,Treatment management ,030220 oncology & carcinogenesis ,Particle Accelerators ,Radiotherapy, Conformal ,business ,Nuclear medicine ,modulation factor - Abstract
The workload for shielding purposes of modern linear accelerators (linacs) consists of primary and scatter radiation which depends on the dose delivered to isocenter (cGy) and leakage radiation which depends on the monitor units (MUs). In this study, we report on the workload for 10 treatment vaults in terms of dose to isocenter (cGy), monitor units delivered (MUs), number of treatment sessions (Txs), as well as, use factors (U) and modulation factors (CI) for different treatment techniques. The survey was performed for the years between 2006 and 2015 and included 16 treatment machines which represent different generations of Varian linear accelerators (6EX, 600C, 2100C, 2100EX, and TrueBeam) operating at different electron and x‐ray energies (6, 9, 12, 16 and 20 MeV electrons and, 6 and 15 MV x‐rays). An institutional review board (IRB) approval was acquired to perform this study. Data regarding patient workload, dose to isocenter, number of monitor units delivered, beam energies, gantry angles, and treatment techniques were exported from an ARIA treatment management system (Varian Medical Systems, Palo Alto, Ca.) into Excel spreadsheets and data analysis was performed in Matlab. The average (± std‐dev) number of treatment sessions, dose to isocenter, and number of monitor units delivered per week per machine in 2006 was 119 ± 39 Txs, (300 ± 116) × 102 cGys, and (78 ± 28) × 103 MUs respectively. In contrast, the workload in 2015 was 112 ± 40 Txs, (337 ± 124) × 102 cGys, and (111 ± 46) × 103 MUs. 60% of the workload (cGy) was delivered using 6 MV and 30% using 15 MV while the remaining 10% was delivered using electron beams. The modulation factors (MU/cGy) for IMRT and VMAT were 5.0 (± 3.4) and 4.6 (± 1.6) respectively. Use factors using 90° gantry angle intervals were equally distributed (~0.25) but varied considerably among different treatment techniques. The workload, in terms of dose to isocenter (cGy) and subsequently monitor units (MUs), has been steadily increasing over the past decade. This increase can be attributed to increased use of high dose hypo‐fractionated regimens (SBRT, SRS) and the increase in use of IMRT and VMAT, which require higher MUs per cGy as compared to more conventional treatment (3DCRT). Meanwhile, the patient workload in terms of treatment sessions per week remained relatively constant. The findings of this report show that variables used for shielding purposes still fall within the recommendation of NCRP Report 151.
- Published
- 2017
45. Experimental Demonstration of an Acoustic Asymmetric Diffraction Grating Based on Passive Parity-Time-Symmetric Medium
- Author
-
Han Jia, Han Zhao, Yuzhen Yang, Jun Yang, and Yafeng Bi
- Subjects
Physics ,Energy distribution ,General Physics and Astronomy ,Parity (physics) ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Imaging phantom ,Modulation factor ,Computational physics ,Nonlinear system ,0103 physical sciences ,Noise control ,010306 general physics ,0210 nano-technology ,Diffraction grating - Abstract
Acoustic asymmetric transport is important for noise control and communication acoustics. Recent progress on non-Hermitian systems has yielded a scheme to realize asymmetric transport without nonlinear effects or mode conversion. The authors report the experimental realization of an asymmetric diffraction grating based on a cleverly designed passive $P\phantom{\rule{0}{0ex}}T$-symmetric medium, in which loss is introduced as an extra modulation factor, and the energy distribution can be adjusted more freely. Moreover, the designed structure is helpful for further research on non-Hermitian acoustic systems.
- Published
- 2019
46. An 80W Power Amplifier with 50% Efficiency at 8dB Power Back-off over 2.6-3.8 GHz
- Author
-
Rui Hou, Paul Saad, Richard Hellberg, and Bo Berglund
- Subjects
Physics ,business.industry ,Amplifier ,020208 electrical & electronic engineering ,dBm ,Electrical engineering ,020206 networking & telecommunications ,02 engineering and technology ,Modulation factor ,Power (physics) ,Electricity generation ,Modulation ,0202 electrical engineering, electronic engineering, information engineering ,Wideband ,business ,Efficient energy use - Abstract
This paper presents the design and implementation of a wideband power amplifier (PA) suitable for applications using signals with large peak-to-average-power-ratio (PAPR). The proposed design approach is based on reducing the load modulation factor compared to conventional Doherty PA. To demonstrate the principle, a PA that operates between 2.55 GHz and 3.8 GHz has been implemented and tested. In this frequency range, the measured peak output power is 49.3 ± 0.5 dBm and the measured drain efficiency is between 47-60 % for output power levels corresponding to 8 dB output back-off (OBO).
- Published
- 2019
47. Dose evaluation indices for total body irradiation using TomoDirect with different numbers of ports: A comparison with the TomoHelical method
- Author
-
Tomonari Sasaki, Hiromi Terashima, Yukihide Fukuyama, Katsumasa Nakamura, and Yuki Kasai
- Subjects
Adult ,Male ,Organs at Risk ,87.55.Gh ,medicine.medical_treatment ,Computed tomography ,Dose distribution ,Tomotherapy ,Neoplasms ,medicine ,Radiation Oncology Physics ,Humans ,Radiology, Nuclear Medicine and imaging ,Radiometry ,87.55.d ,Instrumentation ,87.55.-X ,Aged ,Mathematics ,Radiation ,medicine.diagnostic_test ,business.industry ,TomoTherapy ,Radiotherapy Planning, Computer-Assisted ,Radiotherapy Dosage ,Middle Aged ,Total body irradiation ,Prognosis ,Modulation factor ,TomoDirect ,TomoHelical ,Female ,Radiotherapy, Intensity-Modulated ,Nuclear medicine ,business ,total body irradiation ,Whole-Body Irradiation ,Homogeneity index - Abstract
TomoDirect has been reported to have some advantages over TomoHelical in delivering total body irradiation (TBI). This study aimed to investigate the relationships between the number of ports and the dose evaluation indices in low‐dose TBI in TomoDirect mode using 2–12 ports and to compare these data with those for the TomoHelical mode in a simulation study. Thirteen patients underwent low‐dose TBI in TomoHelical mode from June 2015 to June 2016. We used the same computed tomography data sets for these patients to create new treatment plans for upper‐body parts using TomoDirect mode with 2–12 beam angles as well as TomoHelical mode. The prescription was 4 Gy in two equal fractions. For the TomoDirect data, we generated plans with 2–12 ports with approximately equally spaced angles; the modulation factor, field width, and pitch were 2.0, 5.0 cm, and 0.500, respectively. For the TomoHelical plans, the modulation factor, field width, and pitch were 2.0, 5.0 cm, and 0.397, respectively. D2, D98, D50, and the homogeneity index (HI) were evaluated to compare TomoDirect plans having 2–12 ports with the TomoHelical plan. Using TomoDirect plans, D2 with four ports or fewer, D98 with 10 ports or fewer, D50 with four ports or fewer and HI with five ports or fewer showed statistically significantly worse results than the TomoHelical plan. With the TomoDirect plans, D2 with seven ports or more, D50 with eight ports or more, and HI with eight ports or more showed statistically significant improvement compared with the TomoHelical plan. All of the dose evaluation indices of the TomoDirect plans showed a tendency to improve as the number of ports increased. TomoDirect plans showed statistically significant improvement of D2, D50, and HI compared with the TomoHelical plan. Therefore, we conclude that TomoDirect can provide better dose distribution in low‐dose TBI with TomoTherapy.
- Published
- 2019
48. The Unsteady Spectral Properties of Turbulent Channel Flow at Time Variant Boundary Conditions
- Author
-
Beykirch, M., Hesse, K., Ronneberger, D., Moreau, R., editor, Gavrilakis, S., editor, Machiels, L., editor, and Monkewitz, P. A., editor
- Published
- 1996
- Full Text
- View/download PDF
49. modulation factor
- Author
-
Weik, Martin H. and Weik, Martin H.
- Published
- 2001
- Full Text
- View/download PDF
50. Quantitative evaluation of micro-cracks using nonlinear ultrasonic modulation method
- Author
-
Jingpin Jiao, Cunfu He, Junjun Sun, Nan Li, and Bin Wu
- Subjects
Engineering ,business.industry ,Mechanical Engineering ,Acoustics ,Micro cracks ,Phase (waves) ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Modulation factor ,Nonlinear system ,Modulation ,Nondestructive testing ,mental disorders ,0103 physical sciences ,General Materials Science ,Ultrasonic sensor ,0210 nano-technology ,business ,010301 acoustics ,Reliability (statistics) - Abstract
Nonlinear acoustic coefficients have a close relationship with structural cracks. A nonlinear ultrasonic modulation method for micro-crack quantitative evaluation is developed. The influence of phase threshold on the crack evaluation is discussed. Ultrasonic modulation using a unilateral incentive model is applied to the quantitative evaluation of micro-cracks for different specimens. The experimental results indicate that the method can be beneficially applied for micro-cracks detection. A proper phase threshold can improve the reliability of the method based on nonlinear ultrasonic modulation. The presented modulation factor can be used to quantitatively evaluate the structural cracks, and it is suitable for small-crack quantitative evaluation.
- Published
- 2016
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