Continuous Real-time Tracking Research Articles

MR-Guided Radiotherapy (MRgRT) for Laryngeal Cancer With Real-Time Visualization of Intrafraction Larynx Motion

Although early larynx cancers require treatment of only the vocal cord(s), radiation for early larynx cancer historically consisted of opposed lateral portals that included the entire larynx. Treatment techniques have advanced to 3D conformal and intensity modulated radiotherapy (IMRT), but the treatment target has remained the entire larynx. One concern preventing volume reduction in these patients is periodic swallowing that occurs during treatment delivery due to normal patient physiology. Such intrafraction swallowing can displace the treatment target up to 2 cm and could lead to tumor underdosing. Treatment with real-time target tracking could greatly mitigate this concern. Herein, we describe our initial experience using MR-guided radiotherapy (MRgRT) to visualize and understand the impact of intrafraction larynx motion.Three patients with cT1-2 laryngeal cancer were treated using an MRgRT Linac. Treatment volume included the entire larynx to evaluate feasibility of setup, immobilization, patient tracking, and treatment planning. A commercial MR-compatible head-and-heck immobilization system was developed and utilized, consisting of an indexable baseplate with integrated MR receiver coils affixed to a head cradle, with an open-face thermoplastic mask and head-mold cushion. Treatment plans were inversely planned utilizing 5 anterior IMRT fields to eliminate entrance dose to posterior organs at risk (OARs). The tracking structure consisted of patients' intrinsic larynx muscles delineated by a head and neck radiation oncologist on a 35cm x 35cm x 0.70cm sagittal MR plane. Patients were instructed not to swallow during setup imaging and during treatment. Continuous real-time tracking was performed at 4 frames per second with automatic beam hold if > 5% of the area of the tracking structure exceeded the 3mm isotropic boundary limit.Images were taken during patient treatment, and movement of the intrinsic muscles of the larynx was apparent in all patients due to periodic deglutition. At the time of analysis, 63 fractions have been delivered. The average total in-room time for the three patients in the study was 27:22 minutes (range 18:00 - 45:00 minutes), while the average beam-on time was 8:44 minutes (range 4:00 - 30:00 minutes).MR real-time visualization of the patient's intrinsic laryngeal muscles during MRgRT provides a method of gating treatment during patient swallowing. Robust intrafraction target tracking appears to enable higher confidence in reducing the treatment volume for early larynx cancers such that improvements in preservation of voice quality and deglutition capabilities are possible without sacrificing local control. A clinical trial is planned to examine such volume reduction and its effect on patient quality of life and function.

Mathematical modeling and dynamic characteristic analysis of a novel parallel tracking mechanism for inter-satellite link antenna

Inter-satellite link antenna tracking mechanism is an important enabling component of relay satellite for continuous real-time tracking of medium and low orbit target spacecraft. Facing the major demand of advanced technology development in aerospace engineering, this paper mainly tackles the problem on the rigid-flexible coupling dynamic modeling and dynamic characteristics analysis of a novel parallel tracking mechanism. Firstly, adopting a novel shape function of three-dimensional isoparametric beam element with curvature, the elasto-dynamic model is derived with floating coordinate method and Lagrangian equation. Then the natural frequencies of the system are investigated and ANSYS software is utilized to verify the model. An efficient numerical solution strategy consisting of the implicit integration algorithm and Baumgarte stabilization technology is employed to precisely evaluate the dynamic response of the system. Meanwhile, trajectory planning is carried out for high tracking precision. Furthermore, the validity of the numerical results of dynamic response is illustrated by simulations with the ADAMS software. Finally, the natural frequency sensitivity analysis is implemented by direct differential method with a novel sensitivity index to identify the structure weakness of the mechanism. A novel design idea for the cross-sectional parameters of each flexible beam is proposed with the sensitivity index. Above mentioned research results enrich the basic theoretical researches of parallel mechanism and lay a theoretical foundation for the practical application of tracking mechanism.

Multisensor Distributed Dynamic Programming Method for Collaborative Warning and Tracking

Multisensor distributed dynamic programming for collaborative warning and tracking during antimissile combat serves to meet the tracking accuracy requirements of all ballistic targets in the battlefield under the circumstance of a limited total amount of sensor resources. This paper proposes a method of multisensor distributed dynamic programming for collaborative warning and tracking based on game theory. First, starting from the target tracking algorithm, according to the characteristics of antimissile multisensor combat planning, the box particle filter (BPF) theory capable of distributed filtering and inaccurate measurement is introduced. Using the flight phase characteristics of ballistic targets, a variable structure adaptive multimodel box-based particle filter tracking method is constructed. A box particle filter with the variable structure adaptive interacting multiple model (VSAIMM-BPF) is proposed. The method solves the continuous real-time tracking problem of the ballistic target in all the phases and achieves high tracking accuracy while reducing computational complexity. Then, the motion state of each ballistic target in combat is recursively evaluated by the filtering algorithm, and the calculated sensor information gain is used as a measure to obtain more or better sensor resources for the community of interest to track the corresponding ballistic target through the game. Ultimately, the method achieves distributed dynamic programming.

Continuous Real-Time Tracking of a Quantum Phase Below the Standard Quantum Limit.

We propose a scheme for continuously measuring the evolving quantum phase of a collective spin composed of N pseudospins. Quantum nondemolition measurements of a lossy cavity mode interacting with an atomic ensemble are used to directly probe the phase of the collective atomic spin without converting it into a population difference. Unlike traditional Ramsey measurement sequences, our scheme allows for real-time tracking of time-varying signals. As a bonus, spin-squeezed states develop naturally, providing real-time phase estimation significantly more precise than the standard quantum limit of Δϕ_{SQL}=1/sqrt[N] rad.

A NEW METHOD FOR DETECTION OF UNBALANCE VOLTAGE SUPPLY IN THREE PHASE INDUCTION MOTOR

Induction motors are associated with various techno-economic advantages; therefore these are widely used in residential, commercial and industrial systems. Cost effective and reliable process of condition monitoring of induction motor is very important. It is found that unbalance voltage supply is one of the major factors that produce uneven heating due to reverse current and leads to inter-turn short circuit. The issue regarding unbalanced voltage supply has attracted the attention of researcher and engineers in recent past. In this paper, a new effective non-invasive (online) method is proposed that only use rotor harmonic current signature for the detection of unbalance voltage supply instead of main line current signature. This is a sensor-less and online approach that accomplishes the reliable and accurate analysis of the induction motors. Moreover, it allows a continuous real time tracking without disturbing the normal operation and guarantees the overall production process. Additionally, this method recognizes the unbalance and estimate the severity of the unbalance in the voltage source. The effects of unbalance voltage supply are investigated through experiments. In order to perform the analysis and detect the asymmetry due to unbalance voltage, an experimental set up is designed that can accurately repeat the measurements. In the proposed work, unbalance voltage supply is diagnosed through experimental hardware setup. To validate the propose methods an experiment is performed that confirm that motor operating under unbalance voltage supply give a significant rise in the rotor harmonic while under balance voltage supply there is so such a rise in the rotor harmonic.

An evaluation of indoor location determination technologies

The development of real-time locating systems (RTLS) has become an important add-on to many existing location aware systems. While GPS has solved most of the outdoor RTLS problems, it fails to repeat this success indoors. A number of technologies have been used to address the indoor tracking problem. The ability to accurately track the location of people indoors has many applications ranging from medical, military and logistical to entertainment. However, current systems cannot provide continuous real-time tracking of a moving target or lose capability when coverage is poor. The deployment of a real-time location determination system however is fraught with problems. To date there has been little research into comparing commercial systems on the market with regard to informing IT departments as to their performance in various aspects which are important to tracking devices and people in relatively confined areas. This article attempts to provide such a useful comparison by providing a review of the practicalities of installing certain location-sensing systems. We also comment on the accuracies achieved and problems encountered using the position-sensing systems.

Deep phase modulation interferometry

We have developed a method to equip homodyne interferometers with the capability to operate with constant high sensitivity over many fringes for continuous real-time tracking. The method can be considered as an extension of the "J1 . . .J4" methods, and its enhancement to deliver very sensitive angular measurements through Differential Wavefront Sensing is straightforward. Beam generation requires a sinusoidal phase modulation of several radians in one interferometer arm. On a stable optical bench, we have demonstrated a long-term sensitivity over thousands of seconds of 0.1 mrad/√Hz that correspond to 20 pm/ √Hz in length, and 10 nrad/ √Hz in angle at millihertz frequencies.

Quantifying Respiratory-induced Prostate Motion using Continuous Real-time Tracking Technology

Prostate positional variability can alter the effectiveness of radiation therapy when precise target location is unknown. Traditionally, PTV margins are designed to compensate for inter-fraction prostate setup variability. PTV margins may be reduced when using daily image-guidance. More recently, the dosimetric relevance of intra-fraction prostate motion has been recognized, and may be compensated for by continuous real-time adaptive radiation therapy afforded by the Calypso® 4D Localization System. As of today, sparse data is available regarding the magnitude and clinical relevance of highfrequency respiratory-induced prostate motion. The specific aim of this analysis was to quantify respiratory-induced prostate motion using electromagnetic continuous real-time tracking technology.

An Approach to Tracking Deformable Hand Gesture for Real-Time Interaction

The tracking of deformable hand gesture is a very important task in vision-based HCI (human-computer interaction) research. A novel real-time tracking approach is proposed to capture the motion of deformable hand gesture with single camera. The proposed approach uses a set of 2D hand models in place of high-dimensional 3D model. It achieves auto-initialization by firstly using Bayesian classifier to do posture recognition, and then locating fingers and fingertips to fit image features to recognized posture. It solves the problem of interference among fingers during tracking successfully by the integration of K-means clustering and particle filter. Moreover, a state checking process is embedded into tracking method, and it realizes resumption from tracking failure and update of hand models automatically. Experimental results show that the proposed method can achieve continuous real-time tracking of deformable hand gesture with high precision, and thus it can meet the requirements from real-time vision-based human-computer interaction.

Application of Kalman filtering for continuous real-time tracking of power system harmonics

The paper describes a unit based on an 8-bit microprocessor which enables continuous real-time tracking of the harmonics in the voltage or current waveforms of a power system. The unit is part of a distributed system for monitoring and controlling a power system which applies a 12-state Kalman filter to the voltage or current samples to obtain in real time the instantaneous values for a maximum of six harmonics as well as the existing harmonic distortion. The unit maintains a buffer in memory with the magnitudes of the harmonics detected in the last second and generates an alarm signal when the distortion level of an individual harmonic, or that of the group as a whole, exceeds the threshold established by the international standard.