6D Tracking Research Articles

PLACET3: 6D tracking through PETS and accelerating structures wakefields

We present the latest updates to the PLACET3 tracking package, which focus on the impact of both transverse and longitudinal wakefields on a beam travelling through accelerating and decelerating structures. The main focus of this update was the first implementation of 6D tracking through Power Extraction and Transfer Structures (PETS) for the Compact Linear Collider (CLIC), which is described through short and long-range longitudinal wakefields. Additionally, we present the impact of different numerical schemes on the computation of wakefields in accelerating structures.

A Robust 6-D Pose Tracking Approach by Fusing a Multi-Camera Tracking Device and an AHRS Module

Optical tracking technique based on multiple cameras is widely employed in robots, virtual reality, and industrial measurements due to its excellent position accuracy. However, its 6-dimensional (6D) tracking practicability is impaired by the line-of-sight issue and the complicated tracker based on multiple markers. Hence, we implemented a custom-built hybrid tracking system consisting of four-camera equipment and a 6D tracker comprising a single optical marker and an automatic heading reference system (AHRS). AHRS provides the 3D orientation of the tracked object directly and compensates for the 3D position when the optical tracking is occluded. A two-stage cascaded adaptive Unscented Kalman Filtering (CAUKF) was proposed to enhance real-time fusion tracking performance. The CAUKF not only provides a reliable frequency enhancement solution for the optical tracking adapting to various frequencies, but also improves the continuality of prediction on fusion state variables and the corresponding covariance matrix, which helps to initialize the occlusion tracking accurately. When an occlusion occurs, a learning-based adaptive Unscented Kalman Filter (LAUKF) module can adaptively adjust noise estimation matrices in the unscented transformation according to the AHRS data, thereby significantly reducing the position estimation error. Experimental results reveal that the proposed tracking approach achieved 6D tracking at 100 Hz with 0.32 mm position error (mean absolute error) and 0.1° orientation error. This study furnishes a novel implementation method for the full 6D pose tracking with a simplified tracker structure and improved accuracy, continuity, and stability.

Association of Nanodiamond Rotation Dynamics with Cell Activities by Translation-Rotation Tracking.

Correlated translation-orientation tracking of single particles can provide important information for understanding the dynamics of live systems and their interaction with the probes. However, full six-dimensional (6D) motion tracking has yet to be achieved. Here, we developed synchronized 3D translation and 3D rotation tracking of single diamond particles based on nitrogen-vacancy center sensing. We first performed 6D tracking of diamond particles attached to a giant plasma membrane vesicle to demonstrate the method. Quantitative analysis of diamond particles' motion allowed elimination of the geometric effect and revealed the net rotation on the vesicle. 6D tracking was then applied to measure live cell dynamics. Motion characteristics of nanodiamonds on cell membranes under various controlled physiological conditions suggest that the nanodiamonds' rotation is associated with cell metabolic activities. Our technique extends the toolbox of single particle tracking and provides a unique solution to problems where correlated analysis of translation and rotation is critical.

Geometric and Clinical Factors Affecting Active Fiducial Tracking in Robotic Stereotactic Body Radiation Therapy in the Lung

The movement of lung tumors during the breathing cycle presents a challenge in active tumor and fiducial tracking in the robotic stereotactic body radiation therapy (SABR). Robotic SABR manufacturer guidelines for fiducial placement rarely allows 6D tracking of lung targets, which requires a minimum of 3 tracked fiducials. Advances in navigational bronchoscopy are allowing more controlled fiducial placement. This review of 4D geometric and clinical factors affecting the number of fiducials tracked can potentially optimize fiducial placement. Patients treated at our institution with robotic SABR for lung tumors where error data was available were identified, and their clinical characteristics collected. When available, the fiducials were contoured in each of 10 phases on 4D CT using HU thresholds, and the centroids of the objects calculated in Matlab. The number of fiducials tracked, and the errors in the breathing model that prevented at least 3 fiducials from being tracked were recorded. Clinical correlations were determined using Chi-square tests, comparison of maximum and minimum inter-fiducial distances and errors by Mann-Whitney U, and local control/survival by Kaplan-Meier analysis. 76 patients with 83 treated lesions were identified, 48 patients with available PFTs, 28 patients with fiducial centroid data. Lung primaries and oligometastatic disease were included. Overall survival and local control were not affected by the number of tracked fiducials (p = 0.20, p = 0.79) with 2.5 year follow up. COPD was associated with higher likelihood of having > = 3 fiducials tracked (p = 0.034). Elements of the PFTs, smoking history, and prior lung surgery were not correlated with > = 3 fiducials tracked. The errors preventing at least 3 fiducials to be tracked included rigid body errors (60.2%), spacing (37.3%), uncertainty (15.7%), fiducial shadowing (6.0%), and high collinearity (1.2%). Tumors in the lower lobes had higher rates of uncertainty errors (p = 0.015), especially the left lower lobe (p = 0.007). High maximum inter-fiducial spacing was correlated with rigid body errors (p = 0.022), with incidence rising with fiducial spacing above 3 cm. Low minimum inter-fiducial distance was correlated with spacing errors (p = 0.017). Tumor control and survival were not affected by having <3 fiducials tracked. The increased uncertainty errors in the lower lobes could be due to increased motion, and on the left lower lobe due from superimposed cardiac motion. Fiducials may be more easily tracked in patients with COPD due to the loss of lung elasticity. The expansile nature of lung tissue could increase rigid body errors with increased inter-fiducial distance. Further study is needed to determine how fiducial placement can be optimized to improved tracking and influence how clinicians determine the expansions used to create PTVs.

Concept for Markerless 6D Tracking Employing Volumetric Optical Coherence Tomography.

Optical tracking systems are widely used, for example, to navigate medical interventions. Typically, they require the presence of known geometrical structures, the placement of artificial markers, or a prominent texture on the target’s surface. In this work, we propose a 6D tracking approach employing volumetric optical coherence tomography (OCT) images. OCT has a micrometer-scale resolution and employs near-infrared light to penetrate few millimeters into, for example, tissue. Thereby, it provides sub-surface information which we use to track arbitrary targets, even with poorly structured surfaces, without requiring markers. Our proposed system can shift the OCT’s field-of-view in space and uses an adaptive correlation filter to estimate the motion at multiple locations on the target. This allows one to estimate the target’s position and orientation. We show that our approach is able to track translational motion with root-mean-squared errors below 0.25 mm and in-plane rotations with errors below 0.3°. For out-of-plane rotations, our prototypical system can achieve errors around 0.6°.

From Planes to Corners: Multi-Purpose Primitive Detection in Unorganized 3D Point Clouds

We propose a new method for segmentation-free joint estimation of orthogonal planes, their intersection lines, relationship graph and corners lying at the intersection of three orthogonal planes. Such unified scene exploration under orthogonality allows for multitudes of applications such as semantic plane detection or local and global scan alignment, which in turn can aid robot localization or grasping tasks. Our two-stage pipeline involves a rough yet joint estimation of orthogonal planes followed by a subsequent joint refinement of plane parameters respecting their orthogonality relations. We form a graph of these primitives, paving the way to the extraction of further reliable features: lines and corners. Our experiments demonstrate the validity of our approach in numerous scenarios from wall detection to 6D tracking, both on synthetic and real data.

NimbRo Rescue: Solving Disaster‐response Tasks with the Mobile Manipulation Robot Momaro

Robots that solve complex tasks in environments too dangerous for humans to enter are desperately needed, e.g., for search and rescue applications. We describe our mobile manipulation robot Momaro, with which we participated successfully in the DARPA Robotics Challenge. It features a unique locomotion design with four legs ending in steerable wheels, which allows it both to drive omnidirectionally and to step over obstacles or climb. Furthermore, we present advanced communication and teleoperation approaches, which include immersive three‐dimensional (3D) visualization, and 6D tracking of operator head and arm motions. The proposed system is evaluated in the DARPA Robotics Challenge, the DLR SpaceBot Cup Qualification, and lab experiments. We also discuss the lessons learned from the competitions.

Interplay of Touschek scattering, intrabeam scattering, and rf cavities in ultralow-emittance storage rings

The latest generation of storage ring-based light sources employs multibend achromat lattices to achieve ultralow emittance. These lattices make use of a large number of weak bending magnets which considerably reduces the amount of power radiated in the dipoles in comparison to power radiated from insertion devices. Therefore, in such storage rings, parameters such as emittance, energy spread, and radiated power are—unlike 3rd generation storage rings—no longer constant during a typical user shift. Instead, they depend on several varying parameters such as insertion device gap settings, bunch charge, bunch length, etc. Since the charge per bunch is usually high, intrabeam scattering in medium-energy storage rings with ultralow emittance becomes very strong. This creates a dependence of emittance on stored current. Furthermore, since the bunch length is adjusted with rf cavities but is also varied as insertion device gaps change, the emittance blowup from intrabeam scattering is not constant either. Therefore, the emittance, bunch length, and hence the resulting Touschek lifetime have to be calculated in a self-consistent fashion with 6D tracking taking into account not only the bare lattice and rf cavity settings, but also momentary bunch charge and gap settings. Using the MAX IV 3 GeV storage ring as an example, this paper demonstrates the intricate interplay between transverse emittance (insertion devices, emittance coupling), longitudinal emittance (tuning of main cavities as well as harmonic cavities), and choice of stored current in an ultralow-emittance storage ring as well as some implications for brightness optimization. (Less)

SU-E-T-67: A Simple Tool for Evaluation of Fiducial Placement for CyberKnife SRS/SBRT Treatment

Purpose: To develop a simple software tool to help determine whether a fiducial placement meets the Spacing and Collinearity criteria for CyberKnife 6D target tracking. Methods: An Excel spreadsheet has been developed for this purpose. The spreadsheet calculates distances and angles for all possible combinations of fiducial triplets based on the fiducial coordinates entered. In general, a group of 4 fiducials forms 4 triplets; a group of 6 fiducials forms 20 triplets. Distance between any two points in 3D space can be calculated easily. Angles formed by lines joining a fiducial triplet are calculated by using the law of cosines. Calculations using scalar product of vectors method are also implemented and used as a redundancy check. Fiducial placement and CyberKnife treatment data from 78 prostate patients were analyzed. Results: The spreadsheet checks each fiducial triplet against the Spacing & Collinearity Thresholds. Distances or angles failed to meet the thresholds are flagged. If none of the fiducial triplets meet the criteria, extra fiducials need to be implanted. Of the 78 patients studied, most patients were implanted with 4 fiducials; seven patients had 3, and twenty patients had 6 fiducials. A total of the 345 fiducials and 600+ triplets were analyzed. The study showed that 72% of the fiducial distances exceeded the 20-mm Spacing Threshold, and 99% of the fiducial angles exceeded the 15-degree Collinearity Threshold. Conclusions: We have developed an Excel spreadsheet to verify that a fiducial placement meets the Cyberknife 6D tracking criteria before patient treatment. Analyzing past patient data helps provide guidance on how fiducial placement may be improved. It is important that least one of the fiducial triplets exceed both Spacing and Collinearity Thresholds, as the study has found that there were cases where a fiducial triplet met the Spacing criteria but failed Collinearity criteria, and vice versa.

Six-Dimensional Correction of Intra-Fractional Prostate Motion with CyberKnife Stereotactic Body Radiation Therapy

Large fraction radiation therapy offers a shorter course of treatment and radiobiological advantages for prostate cancer treatment. The CyberKnife is an attractive technology for delivering large fraction doses based on the ability to deliver highly conformal radiation therapy to moving targets. In addition to intra-fractional translational motion (left–right, superior–inferior, and anterior–posterior), prostate rotation (pitch, roll, and yaw) can increase geographical miss risk. We describe our experience with six-dimensional (6D) intra-fraction prostate motion correction using CyberKnife stereotactic body radiation therapy (SBRT). Eighty-eight patients were treated by SBRT alone or with supplemental external radiation therapy. Trans-perineal placement of four gold fiducials within the prostate accommodated X-ray guided prostate localization and beam adjustment. Fiducial separation and non-overlapping positioning permitted the orthogonal imaging required for 6D tracking. Fiducial placement accuracy was assessed using the CyberKnife fiducial extraction algorithm. Acute toxicities were assessed using Common Toxicity Criteria v3. There were no Grade 3, or higher, complications and acute morbidity was minimal. Ninety-eight percent of patients completed treatment employing 6D prostate motion tracking with intra-fractional beam correction. Suboptimal fiducial placement limited treatment to 3D tracking in two patients. Our experience may guide others in performing 6D correction of prostate motion with CyberKnife SBRT.

Only a single implanted marker is needed for tracking lung cancers for IGRT

Only a single implanted marker is needed for tracking lung cancers for IGRT

On multi-rate fusion for non-linear sampled-data systems: Application to a 6D tracking system

Egomotion estimation, e.g. for robot navigation or augmented reality applications, requires the fusion of non-linear sampled-data system with different sensors. An example is to fuse the complimentary characteristics of visual and inertial sensors. Existing approaches either use Kalman filters in conventionally sampled systems or use Particle filters to accommodate the uncertainty of motion models. This paper introduces an approach that models multi-rate non-linear systems to exploit the characteristics of both sensors, assuming synchronicity and periodicity of measurements. The final contribution of this paper is an in-depth analysis and performance comparison of the Extended Kalman filter, the Unscented Kalman filter and three particle filters (Bootstrap, Extended and Unscented). While there is large debate over the pros and cons of these two approaches, this work shows the following results for fusing visual and inertial data in 6 DOF (position and orientation) in a tracking application: the Bootstrap Particle filter gives higher estimation error than Extended and Unscented Particle filters, which give very similar results than Extended and Unscented Kalman filters, but with considerable higher computational burden.

Study of the mass resolving power in the CR storage ring operated as a TOF spectrometer

In this paper we focus on the study of the mass resolving power in the Collector Ring (CR). In one of the modes of operation it is planned to be used as a Time-Of-Flight (TOF) mass spectrometer by making it isochronous, i.e., with a revolution time independent of particle velocity. The dependence of the TOF in the storage ring on the acceptance, closed orbit distortion, nonlinear imperfection of magnet field is analyzed. A kinetic simulation code is used to study the beam dynamics in the isochronous ring. The results of a 6D tracking code give us confidence that the isochronous mode of the CR can be used for mass measurements with a high precision, however, with the restrictions on the acceptance.