The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Paul J. Keall - One of the best experts on this subject based on the ideXlab platform.
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A six-degree-of-freedom robotic motion system for quality assurance of real-time image-guided radiotherapy.
Physics in medicine and biology, 2019Co-Authors: Saree Alnaghy, Andre Kyme, Vincent Caillet, Doan Trang Nguyen, Ricky O'brien, Jeremy T. Booth, Paul J. KeallAbstract:In this study we develop and characterise a six degree-of-freedom (6 DoF) robotic motion system for quality assurance of real-time image-guided radiotherapy techniques. The system consists of a commercially available robotic arm, an acrylic phantom with embedded Calypso markers, a custom base plate to mount the robot to the treatment couch, and control software implementing the appropriate sequence of transformations to reproduce measured tumour motion traces. The robotic motion system was evaluated in terms of the set-up and motion trace repeatability, static Localization Accuracy and dynamic Localization Accuracy. Four prostate, two liver and three lung motion traces, representing a range of tumor motion trajectories recorded in real patient treatments, were executed using the robotic motion system and compared with motion measurements from the clinical Calypso motion tracking system. System set-up and motion trace repeatability was better than 0.5 deg and 0.3 mm for rotation and translation, respectively. The static Localization Accuracy of the robotic motion system in the LR, SI and AP directions was 0.09 mm, 0.08 mm and 0.02 mm for translations, respectively, and 0.2°, 0.06° and 0.06° for rotations, respectively. The dynamic Localization Accuracy of the robotic motion system was
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A six-degree-of-freedom robotic motion system for quality assurance of real-time image-guided radiotherapy
'IOP Publishing', 2019Co-Authors: Alnaghy S, Kyme A, Dt Nguyen, O'brien R, Jt Booth, Paul J. KeallAbstract:© 2019 Institute of Physics and Engineering in Medicine. In this study we develop and characterise a six degree-of-freedom (6 DoF) robotic motion system for quality assurance of real-time image-guided radiotherapy techniques. The system consists of a commercially available robotic arm, an acrylic phantom with embedded Calypso markers, a custom base plate to mount the robot to the treatment couch, and control software implementing the appropriate sequence of transformations to reproduce measured tumour motion traces. The robotic motion system was evaluated in terms of the set-up and motion trace repeatability, static Localization Accuracy and dynamic Localization Accuracy. Four prostate, two liver and three lung motion traces, representing a range of tumor motion trajectories recorded in real patient treatments, were executed using the robotic motion system and compared with motion measurements from the clinical Calypso motion tracking system. System set-up and motion trace repeatability was better than 0.5 deg and 0.3 mm for rotation and translation, respectively. The static Localization Accuracy of the robotic motion system in the LR, SI and AP directions was 0.09 mm, 0.08 mm and 0.02 mm for translations, respectively, and 0.2°, 0.06° and 0.06° for rotations, respectively. The dynamic Localization Accuracy of the robotic motion system was
Raimund J Ober - One of the best experts on this subject based on the ideXlab platform.
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improved single particle Localization Accuracy with dual objective multifocal plane microscopy
Optics Express, 2009Co-Authors: Sripad Ram, Sally E Ward, Prashant Prabhat, Raimund J OberAbstract:In single particle imaging applications, the number of photons detected from the fluorescent label plays a crucial role in the quantitative analysis of the acquired data. For example, in tracking experiments the Localization Accuracy of the labeled entity can be improved by collecting more photons from the labeled entity. Here, we report the development of dual objective multifocal plane microscopy (dMUM) for single particle studies. The new microscope configuration uses two opposing objective lenses, where one of the objectives is in an inverted position and the other objective is in an upright position. We show that dMUM has a higher photon collection efficiency when compared to standard microscopes. We demonstrate that fluorescent labels can be localized with better Accuracy in 2D and 3D when imaged through dMUM than when imaged through a standard microscope. Analytical tools are introduced to estimate the nanoprobe location from dMUM images and to characterize the Accuracy with which they can be determined.
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Localization Accuracy in single molecule microscopy
Biophysical Journal, 2004Co-Authors: Raimund J Ober, Sripad Ram, Sally E WardAbstract:One of the most basic questions in single-molecule microscopy concerns the Accuracy with which the location of a single molecule can be determined. Using the Fisher information matrix it is shown that the limit of the Localization Accuracy for a single molecule is given by, lambda(em)/2pi n(a) square root of gammaAt, where lambda(em), n(a), gamma, A, and t denote the emission wavelength of the single molecule, the numerical aperture of the objective, the efficiency of the optical system, the emission rate of the single molecule and the acquisition time, respectively. Using Monte Carlo simulations it is shown that estimation algorithms can come close to attaining the limit given in the expression. Explicit quantitative results are also provided to show how the limit of the Localization Accuracy is reduced by factors such as pixelation of the detector and noise sources in the detection system. The results demonstrate what is achievable by single-molecule microscopy and provide guidelines for experimental design.
Moe Z Win - One of the best experts on this subject based on the ideXlab platform.
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energy efficient cooperative network Localization
International Conference on Communications, 2014Co-Authors: Wenhan Dai, Yuan Shen, Moe Z WinAbstract:Accurate position information enables numerous location-based applications. Wireless network Localization is a promising Localization technique that permits cooperation among mobile objects to enhance Localization services. The allocation of transmitting power for such networks plays a critical role since it determines network lifetime, throughput, as well as the Localization Accuracy. In this paper, we establish an optimization framework for power allocation in cooperative Localization networks. We first show that the optimal solution for the power allocation problem can be obtained by semi-definite programs (SDPs). For implementation in cooperative Localization networks, we develop efficient and distributed power allocation strategies via relaxation of the original problem. In particular, we decompose the power allocation problem into infrastructure and cooperation parts. We transform the former into SDPs and derive upper bounds for the Localization Accuracy of the latter. These bounds enable us to develop efficient distributed strategies. Simulation results show that these strategies can achieve significant performance improvement compared to the unoptimized strategies in terms of Localization Accuracy.
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on the impact of a priori information on Localization Accuracy and complexity
International Conference on Communications, 2013Co-Authors: Francesco Montorsi, Santiago Mazuelas, G M Vitetta, Moe Z WinAbstract:Accuracy and complexity represent fundamental aspects of Localization and tracking systems. In this manuscript the impact of a priori knowledge about agent position on the Accuracy and the complexity of Localization algorithms is investigated. In particular, first Cramer-Rao bounds on Localization Accuracy are derived under the assumption that a priori information is described by a map restricting the agent position to a specific region. Then, the computational complexity of optimal map-aware and map-unaware Localization techniques is assessed. Our results evidence that: a) map-aware Localization Accuracy can be related to some geometrical features of the map but usually exhibits a complicated dependence on them; b) in some scenarios map-aware Localization algorithms provide better Accuracy than their map-unaware counterparts at comparable computational complexity.
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fundamental limits of wideband Localization part i a general framework
IEEE Transactions on Information Theory, 2010Co-Authors: Yuan Shen, Moe Z WinAbstract:The availability of position information is of great importance in many commercial, public safety, and military applications. The coming years will see the emergence of location-aware networks with submeter Accuracy, relying on accurate range measurements provided by wide bandwidth transmissions. In this two-part paper, we determine the fundamental limits of Localization Accuracy of wideband wireless networks in harsh multipath environments. We first develop a general framework to characterize the Localization Accuracy of a given node here and then extend our analysis to cooperative location-aware networks in Part II. In this paper, we characterize Localization Accuracy in terms of a performance measure called the squared position error bound (SPEB), and introduce the notion of equivalent Fisher information (EFI) to derive the SPEB in a succinct expression. This methodology provides insights into the essence of the Localization problem by unifying Localization information from individual anchors and that from a priori knowledge of the agent's position in a canonical form. Our analysis begins with the received waveforms themselves rather than utilizing only the signal metrics extracted from these waveforms, such as time-of-arrival and received signal strength. Hence, our framework exploits all the information inherent in the received waveforms, and the resulting SPEB serves as a fundamental limit of Localization Accuracy.
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fundamental limits of wideband Localization part i a general framework
arXiv: Information Theory, 2010Co-Authors: Yuan Shen, Moe Z WinAbstract:The availability of positional information is of great importance in many commercial, public safety, and military applications. The coming years will see the emergence of location-aware networks with sub-meter Accuracy, relying on accurate range measurements provided by wide bandwidth transmissions. In this two-part paper, we determine the fundamental limits of Localization Accuracy of wideband wireless networks in harsh multipath environments. We first develop a general framework to characterize the Localization Accuracy of a given node here and then extend our analysis to cooperative location-aware networks in Part II. In this paper, we characterize Localization Accuracy in terms of a performance measure called the squared position error bound (SPEB), and introduce the notion of equivalent Fisher information to derive the SPEB in a succinct expression. This methodology provides insights into the essence of the Localization problem by unifying Localization information from individual anchors and information from a priori knowledge of the agent's position in a canonical form. Our analysis begins with the received waveforms themselves rather than utilizing only the signal metrics extracted from these waveforms, such as time-of-arrival and received signal strength. Hence, our framework exploits all the information inherent in the received waveforms, and the resulting SPEB serves as a fundamental limit of Localization Accuracy.
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position error bound for uwb Localization in dense cluttered environments
IEEE Transactions on Aerospace and Electronic Systems, 2008Co-Authors: Damien B Jourdan, Davide Dardari, Moe Z WinAbstract:For most outdoor applications, systems such as global positioning system (GPS) provide users with accurate location estimates. However, similar range-only Localization techniques in dense cluttered environments typically lack Accuracy and reliability due, notably, to dense multipath, line-of-sight (LOS) blockage and excess propagation delays through materials. In particular, range measurements between a receiver and a transmitter are often positively biased. Furthermore, the quality of the range measurement degrades with distance, and the geometric configuration of the beacons also affects the Localization Accuracy. In this paper we derive a fundamental limit of Localization Accuracy for an ultrawide bandwidth (UWB) system operating in such environments, which we call the position error bound (PEB). The impact of different ranging estimation errors due to beacons distance and biases on the best positioning Accuracy is investigated. The statistical characterization of biases coming from measurement campaigns can easily be incorporated into this analysis. We show that the relative importance of information coming from different beacons varies depending on the propagation conditions, such as whether the beacon is LOS or non-line-of-sight (NLOS). We show, in particular, that any a priori information knowledge on NLOS beacons can significantly improve the Localization Accuracy, especially in dense cluttered environments. Finally we put forth the concept of Localization outage probability and epsi-Localization Accuracy outage, and use them to characterize the quality of Localization throughout the area.
Jason N Gross - One of the best experts on this subject based on the ideXlab platform.
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slip based autonomous zupt through gaussian process to improve planetary rover Localization
International Conference on Robotics and Automation, 2021Co-Authors: Cagri Kilic, Nicholas Ohi, Jason N GrossAbstract:The zero-velocity update (ZUPT) algorithm provides valuable state information to maintain the inertial navigation system (INS) reliability when stationary conditions are satisfied. Employing ZUPT along with leveraging non-holonomic constraints can greatly benefit wheeled mobile robot dead-reckoning Localization Accuracy. However, determining how often they should be employed requires consideration to balance Localization Accuracy and traversal rate for planetary rovers. To address this, we investigate when to autonomously initiate stops to improve wheel-inertial odometry (WIO) Localization performance with ZUPT. To do this, we propose a 3D dead-reckoning approach that predicts wheel slippage while the rover is in motion and forecasts the appropriate time to stop without changing any rover hardware or major rover operations. We validate with field tests that our approach is viable on different terrain types and achieves a 3D Localization Accuracy of more than 97% over 650 m drives on rough terrain.
Alexander M. Haimovich - One of the best experts on this subject based on the ideXlab platform.
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target Localization Accuracy gain in mimo radar based systems
IEEE Transactions on Information Theory, 2010Co-Authors: Alexander M. HaimovichAbstract:This paper presents an analysis of target Localization Accuracy, attainable by the use of multiple-input multiple-output (MIMO) radar systems, configured with multiple transmit and receive sensors, widely distributed over an area. The Cramer-Rao lower bound (CRLB) for target Localization Accuracy is developed for both coherent and noncoherent processing. Coherent processing requires a common phase reference for all transmit and receive sensors. The CRLB is shown to be inversely proportional to the signal effective bandwidth in the noncoherent case, but is approximately inversely proportional to the carrier frequency in the coherent case. We further prove that optimization over the sensors' positions lowers the CRLB by a factor equal to the product of the number of transmitting and receiving sensors. The best linear unbiased estimator (BLUE) is derived for the MIMO target Localization problem. The BLUE's utility is in providing a closed-form Localization estimate that facilitates the analysis of the relations between sensors locations, target location, and Localization Accuracy. Geometric dilution of precision (GDOP) contours are used to map the relative performance Accuracy for a given layout of radars over a given geographic area.
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target Localization Accuracy gain in mimo radar based systems
arXiv: Information Theory, 2008Co-Authors: Hana Godrich, Alexander M. Haimovich, Rick S. BlumAbstract:This paper presents an analysis of target Localization Accuracy, attainable by the use of MIMO (Multiple-Input Multiple-Output) radar systems, configured with multiple transmit and receive sensors, widely distributed over a given area. The Cramer-Rao lower bound (CRLB) for target Localization Accuracy is developed for both coherent and non-coherent processing. Coherent processing requires a common phase reference for all transmit and receive sensors. The CRLB is shown to be inversely proportional to the signal effective bandwidth in the non-coherent case, but is approximately inversely proportional to the carrier frequency in the coherent case. We further prove that optimization over the sensors' positions lowers the CRLB by a factor equal to the product of the number of transmitting and receiving sensors. The best linear unbiased estimator (BLUE) is derived for the MIMO target Localization problem. The BLUE's utility is in providing a closed form Localization estimate that facilitates the analysis of the relations between sensors locations, target location, and Localization Accuracy. Geometric dilution of precision (GDOP) contours are used to map the relative performance Accuracy for a given layout of radars over a given geographic area.
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cramer rao bound on target Localization estimation in mimo radar systems
Conference on Information Sciences and Systems, 2008Co-Authors: Hana Godrich, Alexander M. Haimovich, Rick S. BlumAbstract:This paper presents an analysis of target Localization Accuracy, attainable by the use of MIMO (multiple-input multiple-output) radar systems, configured with multiple transmit and receive antennas, widely distributed over a given area. The Cramer-Rao lower bound (CRLB) for target Localization is developed for coherent processing. It is shown that the Localization estimation Accuracy can be approximated as inversely proportional to the carrier frequency in the coherent case. Evaluation of the relation between sensors locations, target location, and Localization Accuracy is provided by a metric known as geometric dilution of precision (GDOP). GDOP contours map the relative performance Accuracy for a given layout of radars over a given geographic area.
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Target Localization techniques and tools for MIMO radar
2008 IEEE Radar Conference, 2008Co-Authors: Hana Godrich, Alexander M. Haimovich, Rick S. BlumAbstract:MIMO (multiple-input multiple-output) radar refers to an architecture that employs multiple, spatially distributed or colocated transmitters and receivers. The widely spaced antenna structure suggests unique features that set MIMO radar apart from other radar systems, making it strongly related to MIMO communications. The widely separated transmit/receive antennas capture different aspects of the target cross section that can be exploited to obtain diversity gain for detection and estimation of the targetpsilas various parameters, such as angle of arrival, and Doppler. The use of coherent processing can provide Localization Accuracy gains well beyond that supported by the radarpsilas waveform. This paper provides a review of some recent work on computing the Cramer-Rao lower bound (CRLB) on the achievable Localization Accuracy. The geometric dilution of precision (GDOP) is used as a tool for assessing and illustrating the Localization Accuracy of the best linear unbiased estimator (BLUE).
