scholarly journals Comparison of MLC Positioning Deviations Using Log Files and Establishment of Specific Assessment Parameters for Different Accelerators With IMRT and VMAT

2021 ◽  
Author(s):  
Xiutong Lin ◽  
Tao Sun ◽  
Xiao Liu ◽  
Guifang Zhang ◽  
Yong Yin
Keyword(s):  
Influencing Factor ◽  
Similar Data ◽  
Position Errors ◽  
Positioning Errors ◽  
Log Files ◽  
Average Maximum ◽  
Treatment Plans ◽  
Specific Assessment ◽  
Rms Error ◽  
Rms Errors

Abstract Background and purpose: The study evaluated the differences in leaf positioning deviations by the log files of three advanced accelerators with two delivery techniques, and established specific assessment parameters of leaf positioning deviations for different types of accelerators.Methods: A total of 300 treatment plans with 5 consecutive treatment log files were collected from the Trilogy, TrueBeam and Halcyon accelerators. 50 IMRT and 50 VMAT plans were selected randomly on each accelerator. The log files information was parsed by SunCheck software from Sun Nuclear Corporation. The maximum leaf RMS errors, 95th percentile errors and percentages of different leaf positioning errors were statistically analyzed. The correlations between these evaluation parameters and accelerator performance parameters (maximum leaf speed, mean leaf speed, gantry and arc angle) were analyzed.Results: The average maximum leaf RMS errors of the Trilogy in the IMRT and VMAT plans were 0.45±0.1mm and 0.80±0.07mm, respectively, which were higher than the TrueBeam's 0.03±0.01mm, 0.03±0.01 mm and the Halcyon's 0.06±0.01 mm, 0.07±0.01mm. Similar data results were shown in the 95th percentile error. The maximum leaf RMS errors were strongly correlated with the 95th percentile errors. The leaf positioning deviations in VMAT were higher than those in IMRT for all accelerators. In TrueBeam and Halcyon, leaf position errors above 1 mm were not found in IMRT and VMAT plans. The main influencing factor of leaf positioning deviation was the leaf speed, which has no correlation with gantry and arc angles.Conclusions: Compared with the quality assurance guidelines, the MLC positioning deviations tolerances of the three accelerators should be tightened. For both IMRT and VMAT techniques, the 95th percentile error and the maximum RMS error are suggested to be tightened to 1.5 mm and 1 mm for the Trilogy accelerator respectively. In TrueBeam and Halcyon accelerators, the 95th percentile error and maximum RMS error of 1 mm and 0.5 mm, respectively, are considered appropriate.

scholarly journals Performance Analysis of the Korean Positioning System Using Observation Simulation

2020 ◽  
Vol 12 (20) ◽  
pp. 3365
Author(s):  
Byung-Kyu Choi ◽  
Kyoung-Min Roh ◽  
Haibo Ge ◽  
Maorong Ge ◽  
Jung-Min Joo ◽  
...  
Keyword(s):  
Precise Point Positioning ◽  
Service Area ◽  
Geosynchronous Orbit ◽  
Positioning System ◽  
Satellite Navigation System ◽  
Position Errors ◽  
Geo Satellites ◽  
Point Positioning ◽  
Ranging Errors ◽  
Rms Errors

The Korean government has a plan to build a new regional satellite navigation system called the Korean Positioning System (KPS). The initial KPS constellation is designed to consist of seven satellites, which include three geostationary Earth orbit (GEO) satellites and four inclined geosynchronous orbit (IGSO) satellites. KPS will provide an independent positioning, navigation, and timing (PNT) service in the Asia-Oceania region and can also be compatible with GPS. In the simulation for KPS, we employ 24 GPS as designed initially and 7 KPS satellites. Compared to the true orbit that we simulated, the averaged root mean square (RMS) values of orbit-only signal-in-space ranging errors (SISRE) are approximately 4.3 and 3.9 cm for KPS GEO and IGSO. Two different positioning solutions are analyzed to demonstrate the KPS performance. KPS standard point positioning (SPP) errors in the service area are about 4.7, 3.9, and 7.1 m for east (E), north (N), and up (U) components, respectively. The combined KPS+GPS SPP accuracy can be improved by 25.0%, 31.8%, and 35.0% compared to GPS in E, N, and U components. The averaged position errors for KPS kinematic precise point positioning (KPPP) are less than 10 cm. In the fringe of the KPS service area, however, the position RMS errors can reach about 40 cm. Unlike KPS, GPS solutions show high positioning accuracy in the KPS service area. The combined KPS+GPS can be improved by 28.7%, 27.1%, and 30.5% compared to GPS in E, N, and U components, respectively. It is noted that KPS can provide better performance with GPS in the Asia-Oceania region.

scholarly journals Evaluation and Recommendations for Improving the Accuracy of an Inexpensive Water Temperature Logger

2013 ◽  
Vol 30 (7) ◽  
pp. 1576-1582 ◽  
Author(s):  
S. J. Lentz ◽  
J. H. Churchill ◽  
C. Marquette ◽  
J. Smith
Keyword(s):  
Surface Layer ◽  
Solar Radiation ◽  
Water Temperature ◽  
Solar Heating ◽  
Bias Error ◽  
Mean Square ◽  
Temperature Logger ◽  
Accurate Temperature ◽  
Rms Error ◽  
Rms Errors

Abstract Onset's HOBO U22 Water Temp Pros are small, reliable, relatively inexpensive, self-contained temperature loggers that are widely used in studies of oceans, lakes, and streams. An in-house temperature bath calibration of 158 Temp Pros indicated root-mean-square (RMS) errors ranging from 0.01° to 0.14°C, with one value of 0.23°C, consistent with the factory specifications. Application of a quadratic calibration correction substantially reduced the RMS error to less than 0.009°C in all cases. The primary correction was a bias error typically between −0.1° and 0.15°C. Comparison of water temperature measurements from Temp Pros and more accurate temperature loggers during two oceanographic studies indicates that calibrated Temp Pros have an RMS error of ~0.02°C throughout the water column at night and beneath the surface layer influenced by penetrating solar radiation during the day. Larger RMS errors (up to 0.08°C) are observed near the surface during the day due to solar heating of the black Temp Pro housing. Errors due to solar heating are significantly reduced by wrapping the housing with white electrical tape.

Building a precise machine-specific time structure of the spot and energy delivery model for a cyclotron-based proton therapy system

2021 ◽  
Author(s):  
Lewei Zhao ◽  
Gang Liu ◽  
Weili Zheng ◽  
Jiajian Shen ◽  
Andrew Lee ◽  
...  
Keyword(s):  
Proton Therapy ◽  
Switching Time ◽  
Specific Model ◽  
Clinical Treatment ◽  
Main Beam ◽  
Log Files ◽  
Treatment Plans ◽  
Beam Delivery ◽  
Precise Machine ◽  
Accelerator System

Abstract Objective: We proposed an experimental approach to build a precise machine-specific beam delivery time (BDT) prediction and delivery sequence model for standard, volumetric, and layer repainting delivery based on a cyclotron accelerator system. Approach Test fields and clinical treatment plans’ log files were used to experimentally derive three main beam delivery parameters that impacted BDT: energy layer switching time (ELST), spot switching time (SSWT), and spot drill time (SDT). This derived machine-specific model includes standard, volumetric, and layer repainting delivery sequences. A total of 103 clinical treatment fields were used to validate the model. Main results: The study found that ELST is not stochastic in this specific machine. Instead, it is actually the data transmission time or energy selection time, whichever takes longer. The validation showed that the accuracy of each component of the BDT matches well between machine log files and the model’s prediction. The average total BDT was about (-0.74±3.33)% difference compared to the actual treatment log files, which is improved from the current commercial proton therapy system’s prediction (67.22%±26.19%). Significance: An accurate BDT prediction and delivery sequence model was established for an cyclotron-based proton therapy system IBA ProteusPLUS®. Most institutions could adopt this method to build a machine-specific model for their own proton system.

Impact of Frame Positioning Errors on Fuselage Panel Assembly Variation

2013 ◽  
Vol 433-435 ◽  
pp. 847-851
Author(s):  
Wei Miao Yan ◽  
Yun Bo Bi ◽  
Xin Tian Fan ◽  
Kun Peng Du ◽  
Wei Wang
Keyword(s):  
Finite Element ◽  
Information Matrix ◽  
Principal Component ◽  
Element Model ◽  
Position Errors ◽  
Positioning Errors ◽  
Influence Coefficients ◽  
Assembly Accuracy ◽  
Optimum Selection ◽  
The Impact

This paper firstly establishes a finite element model of a fuselage panel, and then an assembly variation model is derived from the method of influence coefficients (MIC) and principal component analysis (PCA). With the calculation of Fisher information matrix and effective independence (EFI), 49 measurement points are extracted from a number of finite element nodes by the optimum selection method, and the mathematical relation between the position errors of measurement points and the positioning errors of frames is established, which is utilized to analyze the impact of positioning errors of each frame on fuselage panel assembly variation. Finally, the key frame that is important to ensure assembly accuracy and to improve the assembly process is determined.

The Estimation of Angular Misalignments for Ultra Short Baseline Navigation Systems. Part I: Numerical Simulations

2013 ◽  
Vol 66 (4) ◽  
pp. 561-578 ◽  
Author(s):  
Hsin-Hung Chen
Keyword(s):  
Numerical Simulations ◽  
Survey Method ◽  
Alignment Error ◽  
Navigation Systems ◽  
Misalignment Angle ◽  
Short Baseline ◽  
Position Errors ◽  
Positioning Errors ◽  
Line Survey ◽  
Survey Approach

Ultra Short Baseline (USBL) navigation systems are often faced with positioning errors arising from misalignments between sensors. This paper proposes a line survey method for USBL angular alignment calibration. In the scheme of USBL line survey, mathematical representations of positioning error arising from heading, pitch and roll misalignments are derived, respectively. The effect of each misalignment angle and how the differences can be used to calibrate each misalignment angle in turn are presented. An iterative algorithm that takes advantage of the geometry of position errors resulting from angular misalignments is developed for USBL calibration. Numerical simulations are provided to demonstrate the effectiveness of the USBL line survey approach. In addition, the effect of measurement error on the estimation of roll alignment error is evaluated and discussed.

scholarly journals NPC, A New Combined Position Catalogue of Stars in the Northern Pole Region

1997 ◽  
Vol 165 ◽  
pp. 499-504
Author(s):  
L.G. Taff ◽  
V.V. Tel’nyuk-Adamchuk ◽  
O.A. Molotaj
Keyword(s):  
Main Task ◽  
Proper Motions ◽  
Polar Cap ◽  
Position Errors ◽  
The North ◽  
The Mean ◽  
North Polar ◽  
Right Ascension ◽  
Second Use ◽  
Rms Errors

AbstractThe main task of this work was to construct a new catalogue of positions and proper motions of stars in the north polar cap, and using the results obtained to study the systematic features of the source catalogues as well as the reference system in the polar region. To achieve the goal, thirteen source catalogues, both meridian and photographic, covering an epoch span near one and a half century, were collected. Most of them were not involved in the process of both the PPM and the ACRS constructions. The new combined catalogue of positions and proper motions, named North Polar Catalogue (NPC), lists 4272 stars on the FK5 system, J2000.0. The catalogue was constructed using the method of infinitely overlapping circles. It represents the second use of this procedure to construct a star catalogue. External rms accuracy of positions for the epoch of 2000 is equal to 015 and 025 for the centennial proper motions, respectively. The internal rms errors of positions at the mean catalogue epoch, near 1940, are equal to 018 and 015 for right ascension and declination correspondingly, while external rms position errors for that epoch are of the order of 005. Comparisons were made between the NPC and three modern catalogues, the FK5, PPM, and ACRS. The systematic differences between the new catalogue and PPM one for the epoch of 2000 are valuable, especially in the case of errors depending on right ascension. The authors consider as an essential part of the systematic differences that, which is caused by some shortcomings of the PPM in the polar zone. For the mean epoch of the new catalogue positions the systematic differences are smaller.

scholarly journals EP-1922: Comparing MLC positioning errors in Clinac and Truebeam Linacs by analysing log files

2016 ◽  
Vol 119 ◽  
pp. S912
Author(s):  
J. Olasolo Alonso ◽  
P. Gago ◽  
A. Vazquez ◽  
S. Pellejero ◽  
C. Eito ◽  
...  
Keyword(s):  
Positioning Errors ◽  
Log Files

1330 poster THE ROBUSTNESS OF CLINICAL VMAT TREATMENT PLANS TO MLC LEAF POSITIONING ERRORS

2011 ◽  
Vol 99 ◽  
pp. S497-S498
Author(s):  
U. Isacsson ◽  
K. Nygård ◽  
K. Wikström ◽  
E. Blomquist
Keyword(s):  
Positioning Errors ◽  
Treatment Plans

Using Multiple Surrogates for Minimization of the RMS Error in Meta-Modeling

2008 ◽  
Author(s):  
Felipe A. C. Viana ◽  
Raphael T. Haftka
Keyword(s):  
Cross Validation ◽  
Weighted Average ◽  
Large Set ◽  
High Dimensions ◽  
Engineering Problems ◽  
Cross Validation Error ◽  
Data Points ◽  
Meta Modeling ◽  
Rms Error ◽  
Rms Errors

Surrogate models are commonly used to replace expensive simulations of engineering problems. Frequently, a single surrogate is chosen based on past experience. Previous work has shown that fitting multiple surrogates and picking one based on cross-validation errors (PRESS in particular) is a good strategy, and that cross validation errors may also be used to create a weighted surrogate. In this paper, we discuss whether to use the best PRESS solution or a weighted surrogate when a single surrogate is needed. We propose the minimization of the integrated square error as a way to compute the weights of the weighted average surrogate. We find that it pays to generate a large set of different surrogates and then use PRESS as a criterion for selection. We find that the cross validation error vectors provide an excellent estimate of the RMS errors when the number of data points is high. Hence the use of cross validation errors for choosing a surrogate and for calculating the weights of weighted surrogates becomes more attractive in high dimensions. However, it appears that the potential gains from using weighted surrogates diminish substantially in high dimensions.

Calibration of omnidirectional wheeled mobile robots: method and experiments

Robotica ◽  
2013 ◽  
Vol 31 (6) ◽  
pp. 969-980 ◽  
Author(s):  
Yaser Maddahi ◽  
Ali Maddahi ◽  
Nariman Sepehri
Keyword(s):  
Mobile Robot ◽  
Mobile Robots ◽  
Systematic Errors ◽  
Wheeled Mobile Robot ◽  
Wheeled Mobile Robots ◽  
Omnidirectional Mobile Robot ◽  
Position Errors ◽  
Positioning Errors ◽  
Surface Irregularities ◽  
Omnidirectional Wheels

SUMMARYOdometry errors, which occur during wheeled mobile robot movement, are inevitable as they originate from hard-to-avoid imperfections such as unequal wheels diameters, joints misalignment, backlash, slippage in encoder pulses, and much more. This paper extends the method, developed previously by the authors for calibration of differential mobile robots, to reduce positioning errors for the class of mobile robots having omnidirectional wheels. The method is built upon the easy to construct kinematic formulation of omnidirectional wheels, and is capable of compensating both systematic and non-systematic errors. The effectiveness of the method is experimentally investigated on a prototype three-wheeled omnidirectional mobile robot. The validations include tracking unseen trajectories, self-rotation, as well as travelling over surface irregularities. Results show that the method is very effective in improving position errors by at least 68%. Since the method is simple to implement and has no assumption on the sources of errors, it should be considered seriously as a tool for calibrating omnidirectional mobile having any number of wheels.

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