Optical Tracking System Research Articles

Inertial Measurement Units’ Reliability for Measuring Knee Joint Angle during Road Cycling

We explore the reliability of joint angles in road cycling obtained using inertial measurement units. The considered method relies on 3D accelerometer and gyroscope measurements obtained from two such units, appropriately attached to two adjacent body parts, measuring the angle of the connecting joint. We investigate the effects of applying a simple drift compensation technique and an error-state Kalman filter. We consider the knee joint angle in particular, and conduct two measurement trials, a 5 and a 20 minute one, for seven subjects, in a closed, supervised laboratory environment and use optical motion tracking system measurements as reference. As expected from an adaptive solution, the Kalman filter gives more stable results. The root mean square errors per pedalling cycle are below 3.2°, for both trials and for all subjects, implying that inertial measurement units are not only reliable for short measurements, as is usually assumed, but can be reliably used for longer measurements as well. Considering the accuracy of the results, the presented method can be reasonably extended to open, unsupervised environments and other joint angles. Implementing the presented method supports the development of cheaper and more efficient monitoring equipment, as opposed to using expensive motion tracking systems. Consequently, cyclists can have an affordable way of position tracking, leading to not only better bicycle fitting, but to the avoidance and prevention of certain injuries as well.

The sizing and suitability of nonspherical ellipsoid humeral heads for total shoulder arthroplasty.

Total shoulder arthroplasty (TSA) implants have evolved to include more anatomically shaped components that better replicate the native state. The geometry of the humeral head is nonspherical, with the frontal diameter of the base of the head being up to 6% larger than the sagittal diameter. Despite this, most TSA humeral head implants are spherical, meaning that the diameter must be oversized to achieve complete coverage, resulting in articular overhang, or portions of the resection plane will remain uncovered. It is suggested that implant-bone load transfer between the backside of the humeral head and the cortex on the resection plane may yield better load-transfer characteristics if resection coverage were properly matched without overhang, thereby mitigating proximal stress shielding. Eight paired cadaveric humeri were prepared for TSA by an orthopedic surgeon who selected and prepared the anatomic humeral resection plane using a cutting guide and a reciprocating sagittal saw. The humeral head was resected, and the resulting cortical boundary of the resection plane was digitized using a stylus and an optical tracking system. To simulate optimal sizing of both circular and elliptical humeral heads, both circles and ellipses were fit to the traces. Two extreme scenarios were also investigated: upsizing until 100% total coverage and downsizing until 0% overhang. By switching from a spherical (circular) to an ellipsoid (elliptical) humeral head, a small, 2.3%±0.3% increase in total coverage occurred (P<.001), which led to a large, 19.5%±1.3% increase in cortical coverage (P<.001). Using a circular head resulted in 2.0%±0.1% greater overhang (P<.001), defined as a percentage of the total enclosed area that exceeded the bounds of the humeral resection. As a result of increasing the head size until 100% resection coverage occurred, the ellipse produced 5.4%±3.5% less overhang than the circle (P<.001). When the head size was decreased until 0% overhang occurred, total coverage was 7.5%±2.8% greater for the ellipse (P<.001) and cortical coverage was 7.9%±8.2% greater for the ellipse (P=.01). Cortical coverage was greater for circular heads when the head size was shrunk below -2.25% of the optimal fitted size. Reconstruction with ellipsoid humeral heads can provide greater total resection and cortical coverage than spherical humeral heads while avoiding excessive overhang; however, cortical coverage can be inferior when undersized. These initial findings suggest that resection-matched humeral heads may yield benefits worth pursuing in the next generation of TSA implant design.

Characterization of cadmium sulfide light dependent resistors sensors for optical solar trackers

&lt;span lang="EN-US"&gt;The aim of this paper is to study the effect of dissimilarity of the intrinsic characteristics of the light dependent resistor (LDRs) on optical sun tracking systems, designed for solar power concentration applications such as parabolic trough collectors, Fresnel mirrors concentrators, and concentrated photovoltaic, a comparative study was done between a sun tracker based on LDRs chosen randomly with and without an initial calibration of the offsets, and a sun tracker based on LDRs selected meticulously thanks to a black box test bench, developed especially for this purpose. By choosing two light dependent resistors randomly, the dissimilarity between them can reach 23.2%, which cause a bad sun tracking even with initial offset calibration, in the other hand, and by the use of selected LDRs using the test bench, the dissimilarity drops to 0.06%, which meets requirements of solar power concentration systems.&lt;/span&gt;

A mixed reality-based navigation method for dental implant navigation method: A pilot study

This in vitro study aimed to put forward the development and investigation of a novel Mixed Reality (MR)-based dental implant navigation method and evaluate implant accuracy. Data were collected using 3D-cone beam computed tomography. The MR-based navigation system included a Hololens headset, an NDI (Northern Digital Inc.) Polaris optical tracking system, and a computer. A software system was developed. Resin models of dentition defects were created for a randomized comparison study with the MR-based navigation implantation system (MR group, n = 25) and the conventional free-hand approach (FH group, n = 25). Implant surgery on the models was completed by an oral surgeon. The precision and feasibility of the MR-based navigation method in dental implant surgery were assessed and evaluated by calculating the entry deviation, middle deviation, apex deviation, and angular deviation values of the implant. The system, including both the hardware and software, for the MR-based dental implant navigation method were successfully developed and a workflow of the method was established. Three-Dimensional (3D) reconstruction and visualization of the surgical instruments, dentition, and jawbone were achieved. Real-time tracking of implant tools and jaw model, holographic display via the MR headset, surgical guidance, and visualization of the intraoperative implant trajectory deviation from the planned trajectory were captured by our system. The MR-based navigation system was with better precise than the free-hand approach for entry deviation (MR: 0.6914 ± 0.2507 mm, FH: 1.571 ± 0.5004 mm, P = 0.000), middle deviation (MR: 0.7156 ± 0.2127 mm, FH: 1.170 ± 0.3448 mm, P = 0.000), apex deviation (MR: 0.7869 ± 0.2298 mm, FH: 0.9190 ± 0.3319 mm, P = 0.1082), and angular deviation (MR: 1.849 ± 0.6120°, FH: 4.933 ± 1.650°, P = 0.000).

Accuracy of Advanced Active Robot for Total Knee Arthroplasty: A Cadaveric Study.

Although the accuracy of other types of robotic systems for total knee arthroplasty (TKA) has been assessed in cadaveric studies, no investigations have been performed to evaluate this newly advanced active robotic system. Therefore, the authors aimed to analyze the accuracy of bone resection in terms of thickness and alignment in a cadaveric study. Three cadaveric specimens (six knees) and an active robotic system (CUVIS Joint, CUREXO) were used in the study. Three surgeons with different experiences in robotic TKAs performed this cadaveric study using the same robotic protocol with two different implant designs. The thickness and angle of bone resection planes obtained from the optical tracking system and the difference between resection planes and the planning data were assessed to determine accuracy. With respect to the overall resection accuracy compared to the plan, the cutting depth accuracy was within 1.0 mm mean of root mean square (RMS), and the resection angle accuracy in terms of sagittal, coronal, and axial planes was within 1.0 degree mean RMS. In contrast, no significant differences were observed between the planned and measured values in terms of the resection angles and cutting thickness. The hip-knee-ankle angle at postoperative evaluation was 0.7 degrees ± 0.7 degrees (RMS 1.0 degrees). This in vivo study suggests that the use of this newly advanced active robotic system for TKA demonstrates a high degree of accuracy in terms of resection thickness and alignment. This finding supports the clinical application of this advanced robotic system. LEVEL OF EVIDENCE: Cadaveric study, Level V.

Robotic biomechanical evaluation of six different reverse shoulder implants

BackgroundThe reverse total shoulder arthroplasty is a popular surgical treatment for a degenerative shoulder with a nonfunctional rotator cuff. Currently, more than 36 different brands with small different features are available. This creates choice stress among many surgeons, who no longer know which parameters and surgical factors are important to optimize the placement of the implant. PurposeThe first purpose of this pilot study was to compare the passive range of motion (ROM) of 6 different implant designs implanted following the manufacturer’s guidelines. The second goal was to identify the impingements after implantation which determines the maximal ROM. The last goal of the study was to link the different parameters of an implant with the ROM. MethodsSix implant systems were implanted on identical sawbones. The procedure was repeated 3 times on a different sawbone to objectify the surgical repeatability of the procedures. A Stäubli TX-90 robot was used to perform and control the humerus' kinematic movement. An optical tracking system was used to perform the system's calibrations, track the humerus and scapula in space, and compute the center of rotation. ResultsThere was a wide ROM in the scapular plane (44.8°-105.5°) while the minimal elevation (adduction) varied between −4.8° and 35.6°. The rotational movements were limited by contact of the superior humeral polyethylene inlay and the inferior scapular neck. The adduction in the coronal and scapular plane was limited by inferior scapular impingement, whereas the maximal abduction was limited either by bony contact between the humerus and acromion or by contact between the humeral polyethylene inlay and the superior glenoid cavity. A bigger radius of the glenosphere resulted in a larger passive humeroscapular ROM (P < .001). A larger Neck-Shaft-Angle results in a better abduction (P < .001) but compromised adduction (P < .001). The localization of the center of rotation has a significant impact on the ROM. The medialized designs have larger abduction and rotational angles (P < .001). ConclusionThere is a wide variation in the measured glenohumeral ROM between the 6 frequently implanted prostheses. The most important factor to optimize the impingement-free ROM in all types of prostheses is the creation of the prosthetic overhang of the glenosphere to the bone. Too much lateralization of the center of the glenosphere with or without lateralization of the humeral stem can create a subacromial and/or subcoracoidal impingement.

Optimization Scheme for Online Viewpoint Planning of Active Optical Navigation System in Orthopedic Surgeries

Optical tracking system (OTS) is widely used in robot orthopedic surgeries. During the surgery, the locomotion of the surgical instrument along different osteotomy planes and the adjustment of the patient’s body will lead to obvious variations on the spatial relationship among the positioning tools. Usually, the OTS is manually placed at a fixed viewpoint. As the size of the measurement volume (MV) of the OTS is limited, some positioning tools might move towards the boundaries of the MV, increasing the risk of navigation failure. This paper proposes a two-phase optimization scheme for the active online adjusting of the OTS viewpoint to guarantee the consistency of navigation. A novel optimization structure is proposed with the consideration of continuous state inequality constraints. The dynamic accuracy of the OTS during the active adjusting is also demonstrated to be reliable. Ultimately, simulations and experiments are performed on an active navigation system to verify the effectiveness of the proposed two-phase optimization scheme. Experimental results show that the OTS can be moved to the optimal viewpoint smoothly when confronted with significant variations on the spatial relationship among the positioning tools, guaranteeing the consistency of navigation. The navigation robot successfully keeps the positioning tools around the central region of the MV at different surgical phases.

Does player age influence match physical performance? A longitudinal four-season analysis in Spanish Soccer LaLiga.

This study aims to analyse the evolution of match running performance in relation to the age distribution of professional soccer players using a large-scale analysis. An explorational-longitudinal and retrospective study was designed and a total of 36,883 individual match observations were collected on outfield players competing across four consecutive Spanish LaLiga seasons (from 2015/16 to 2018/19), using an optical tracking system (ChyronHego). Soccer players were divided into 3 age groups: young (18-24 years old), middle-aged (25-30 years old), and seniors (31-41 years old). Relative total distance (TD/min), distance covered at 21-24 km · h-1 (HIRD/min), and > 24 km · h-1 per minute (VHIRD/min) were analysed; also, the number of efforts at 21-24 km · h-1 (Sp21) and > 24 km · h-1 (Sp24) were taken into consideration. Seasons were divided into four phases (P): P1 (matches 1-10), P2 (11-19), P3 (20-29), and P4 (30-38). The results showed that young players covered significantly greater TD, HIRD and VHIRD than the rest of the players (p < .05) in all season phases. In addition, TD significantly decreased along season phases in all player age group (p < .01). Crucially, young players performed significantly greater numbers of Sp21 and Sp24 than the rest of the players (p < .05) in all season phases. In addition, Sp21 and SP24 significantly decreased in middle-aged (p < .01) and senior players (p < .05) across the seasons. This study demonstrated that players' match running performance decreases with increasing years, especially in high-intensity running distances.

Modeling of a Soft Robotic Tongue Driven by Compressed Air

A novel soft robotic tongue is proposed for the purpose of presenting typical tongue movements in speaking, which is pneumatically actuated and supposed to be applied in pronunciation teaching device and humanoid robot to gain verisimilitude. The actuation and control system is mainly composed of solenoid proportional valves (ITV0010, SMC, Japan), DAQ card (PCIe6321, NI, USA) and motion tracking system (OptiTrack, NaturalPoint, USA). A theoretical model based on continuum mechanics is established building the relationship between input air pressure and output deformation. On the basis of the proposed theoretical model and Artificial Neural Network (ANN), an integrated control algorithm is preliminarily raised for different purpose of use in static and dynamic control. A series of verification experiments are carried out based on OptiTrack system in order to test motion controllability and working performance of the robotic tongue. The experimental results indicate that the proposed theoretical model is more suitable for static shape control due to obvious deformation delay compared with input air pressure. High deformation repeatability guarantees the precision of ANN based control method which is more suitable for dynamic motion control. The results of performance test show that actual movements of the robotic tongue generally meet the demand in demonstrating tongue shape when speaking.

Decision Tree based diagnosis for hybrid model-based/data-driven fault detection and exclusion of a decentralized multi-vehicle cooperative localization system*

Cooperative navigation systems are one of the main topics of interest in multi-robot systems emerging nowadays, where the question of safety remains a very critical one preventing the actual integration of the technology. In this article, a multi-sensor multi-vehicle Cooperative Positioning System (CPS) is presented, with a hybrid fault detection method under a decentralized architecture, and that is tolerant to simultaneous sensor faults. In order to detect and isolate faults, a set of fault sensitive residuals are generated based on the divergence of Jensen Shannon (DJS) between the probability distributions predicted by the encoder based evolution model and the various observations obtained by sensors. Then, in order to detect a fault, a data-driven approach is applied, where the classification of faults is done by a pre-trained detection decision tree (D-DT) and isolation random forest (I-RF). The testing and evaluation of the approach is done on real data from three Turtlebot3 burger robot equipped with wheel encoders (for prediction), a gyroscope (for the yaw angle) and a Marvelmind (for the absolute position). A ground truth is also recorded using optitrack system.

Differences in maxillomandibular relationship recorded at centric relation when using a conventional method, four intraoral scanners, and a jaw tracking system: A clinical study

Statement of problemDigital systems including intraoral scanners (IOSs) and optical jaw tracking systems can be used to acquire the maxillomandibular relationship at the centric relation (CR). However, the discrepancy of the maxillomandibular relationship recorded at the CR position when using digital methods remains uncertain. PurposeThe purpose of this clinical study was to compare the accuracy of the maxillomandibular relationship recorded at the CR position using a conventional procedure, 4 different IOSs, and an optical jaw tracking system. Material and methodsA completely dentate volunteer was selected. A Kois deprogrammer (KD) was fabricated. Six groups were created based on the technique used to obtain diagnostic casts and record the maxillomandibular relationship at the CR position: conventional procedures (CNV group), 4 IOS groups: TRIOS4 (TRIOS4 group), iTero Element 5D (iTero group), i700 wireless (i700 group), Primescan (Primescan group), and a jaw tracking system (Modjaw) (Modjaw group) (n=10). In the CNV group, conventional diagnostic stone casts were obtained. A facebow record was used to mount the maxillary cast on an articulator (Panadent). The KD was used to obtain a CR record for mounting the mandibular cast, and the mounted casts were digitized by using a scanner (T710) to acquire the reference scans. In the TRIOS group, intraoral scans were obtained and duplicated 10 times. The KD was used to obtain a bilateral virtual occlusal record at the CR position. To acquire the specimens of the iTero, i700, and Primescan groups, the procedures in the TRIOS4 group were followed, but with the corresponding IOS. In the Modjaw group, the KD was used to record and export the maxillomandibular relationship at the CR position. Articulated virtual casts of each group were exported. Thirty-six interlandmark linear measurements were computed on both the reference and experimental scans. The distances obtained on the reference scan were used to calculate the discrepancies with the distances obtained on each experimental scan. The data were analyzed by using 1-way ANOVA followed by the pairwise comparison Tukey tests (α=.05). ResultsThe trueness and precision of the maxillomandibular relationship record were significantly affected by the technique used (P<.001). The maxillomandibular relationship trueness values from high to low were iTero (0.14 ±0.09 mm), followed by the Modjaw (0.20 ±0.04 mm) and the TRIOS4 (0.22 ±0.09 mm) groups. However, the iTero, Modjaw, and TRIOS4 groups were not significantly different from each other (P>.05). The i700 group obtained the lowest trueness and precision values (0.40 ±0.22 mm) of all groups tested, followed by the Primescan grop (0.26±0.13 mm); however, the i700 and Primescan groups had significantly lower trueness and precision than only the iTero group (P<.05). ConclusionsThe trueness and precision of the maxillomandibular relationship recorded at the CR position were influenced by the different digital techniques tested.

Generating Patient-Specific Acoustic Simulations for Transcranial Focused Ultrasound Procedures Based on Optical Tracking Information.

Optical tracking is a real-time transducer positioning method for transcranial focused ultrasound (tFUS) procedures, but the predicted focus from optical tracking typically does not incorporate subject-specific skull information. Acoustic simulations can estimate the pressure field when propagating through the cranium but rely on accurately replicating the positioning of the transducer and skull in a simulated space. Here, we develop and characterize the accuracy of a workflow that creates simulation grids based on optical tracking information in a neuronavigated phantom with and without transmission through an ex vivo skull cap. The software pipeline could replicate the geometry of the tFUS procedure within the limits of the optical tracking system (transcranial target registration error (TRE): 3.9 ± 0.7 mm). The simulated focus and the free-field focus predicted by optical tracking had low Euclidean distance errors of 0.5±0.1 and 1.2±0.4 mm for phantom and skull cap, respectively, and some skull-specific effects were captured by the simulation. However, the TRE of simulation informed by optical tracking was 4.6±0.2, which is as large or greater than the focal spot size used by many tFUS systems. By updating the position of the transducer using the original TRE offset, we reduced the simulated TRE to 1.1 ± 0.4 mm. Our study describes a software pipeline for treatment planning, evaluates its accuracy, and demonstrates an approach using MR-acoustic radiation force imaging as a method to improve dosimetry. Overall, our software pipeline helps estimate acoustic exposure, and our study highlights the need for image feedback to increase the accuracy of tFUS dosimetry.

Tracking-by-Registration: A Robust Approach for Optical Tracking System in Surgical Navigation

Tracking-by-Registration: A Robust Approach for Optical Tracking System in Surgical Navigation

The effect of ball possession on physical and technical performance in UEFA Champions league matches

ABSTRACT This study aimed to examine the effects of low-percentage ball possession teams (LPBPT) and high-percentage ball possession teams (HPBPT) on the physical and technical performance of UEFA Champions League (UCL) players. All data were obtained from group stage matches of UCL during the 2020/21 season using a semi-automatic optical tracking system. Linear mixed model was fitted with contextual variables as covariates. Wide midfielders and forwards in LPBPT covered more total distance, low-intensity running, and achieved greater average speed than in HPBPT (all large effect sizes [ES]). Central defenders and fullbacks covered more high-intensity running (small ES), while CMs covered more sprinting (medium ES) in HPBPT than in LPBPT. Players on all playing positions produced greater number of passes and successful passes in HPBPT than in LPBPT (large ES), except forwards who produced more passes in LPBPT than in HPBPT (small ES). Both physical and technical performance were highly dependent on ball possession percentages, with evident position-specific changes, indicating that the effect of ball possession is highly position-dependent. These findings provide information for soccer coaches on physical and technical demands across teams with varying percentage ball possession, which could be used to individualise training programs based on playing style and position.

Prediction of soccer clubs’ league rankings by machine learning methods: The case of Turkish Super League

The aim of this research is to predict league rankings through various machine learning models using technical and physical parameters. This study followed a longitudinal observational analytical design. The SENTIO Sports optical tracking system was used to measure the physical demands and technical practices of the players in all matches. Then, the data regarding the last three seasons of the Turkish Super League (2015–2016, 2016−2017, and 2017−2018), was collected. In this research, league rankings were estimated using three machine learning methods: Artificial Neural Networks (ANN), Radial Basis Function (RBFN), Multiple Linear Regression (MLR) with technical and physical parameters of all seasons. Performances were evaluated through R2, Root Mean Square Error (RMSE), and Mean Absolute Error (MAE). Prediction results of the models are the following: ANN Model; R2 = 0.60, RMSE = 3.7855 and MAE = 2.9139, RBFN Model; R2 = 0.26, MAE = 3.6292 and RMSE = 4.5168, MLR Model; R2 = 0.46, MAE = 3.4859 and RMSE = 4.2064. These results showed that ANN can be used as a successful tool to predict league rankings. In the light of this research, coaches and athletic trainers can organize their training in a way that affects the technical and physical parameters to change the results of the competition. Thus, it will be possible for teams to have a better place in the league-end success ranking.

Ultrasound Probe and Hand-Eye Calibrations for Robot-Assisted Needle Biopsy

In robot-assisted ultrasound-guided needle biopsy, it is essential to conduct calibration of the ultrasound probe and to perform hand-eye calibration of the robot in order to establish a link between intra-operatively acquired ultrasound images and robot-assisted needle insertion. Based on a high-precision optical tracking system, novel methods for ultrasound probe and robot hand-eye calibration are proposed. Specifically, we first fix optically trackable markers to the ultrasound probe and to the robot, respectively. We then design a five-wire phantom to calibrate the ultrasound probe. Finally, an effective method taking advantage of steady movement of the robot but without an additional calibration frame or the need to solve the AX=XB equation is proposed for hand-eye calibration. After calibrations, our system allows for in situ definition of target lesions and aiming trajectories from intra-operatively acquired ultrasound images in order to align the robot for precise needle biopsy. Comprehensive experiments were conducted to evaluate accuracy of different components of our system as well as the overall system accuracy. Experiment results demonstrated the efficacy of the proposed methods.

Identification of Kinetic Abnormalities in Male Patients after Anterior Cruciate Ligament Deficiency Combined with Meniscal Injury: A Musculoskeletal Model Study of Lower Limbs during Jogging.

There is little known about kinetic changes in anterior cruciate ligament deficiency (ACLD) combined with meniscal tears during jogging. Therefore, 29 male patients with injured ACLs and 15 healthy male volunteers were recruited for this study to investigate kinetic abnormalities in male patients after ACL deficiency combined with a meniscal injury during jogging. Based on experimental data measured by an optical tracking system, a subject-specific musculoskeletal model was employed to estimate the tibiofemoral joint kinetics during jogging. Between-limb and interpatient differences were compared by the analysis of variance. The results showed that decreased knee joint forces and moments of both legs in ACLD patients were detected during the stance phase compared to the control group. Meanwhile, compared with ACLD knees, significantly fewer contact forces and flexion moments in ACLD combined with lateral and medial meniscal injury groups were found at the mid-stance, and ACLD with medial meniscal injury group showed a lower axial moment in the loading response (p < 0.05). In conclusion, ACLD knees exhibit reduced tibiofemoral joint forces and moments during jogging when compared with control knees. A combination of meniscus injuries in the ACLD-affected side exhibited abnormal kinetic alterations at the loading response and mid-stance phase.

Quantitative Analysis of Lower Limb Motion in Parkinson’s Disease Based on Inertial Sensors

This study proposed a wearable inertial motion capture (Mocap) method for Parkinson’s lower limb motion reconstruction and analysis. To eliminate the error accumulation caused by sensor noise, the error state Kalman filter is used for attitude estimation. The inertial Mocap method proposed in this study is compared with the OptiTrack system to verify the motion tracking effect. The accuracy of different phase-detection methods is compared, and the highest recognition accuracy is 99.11% using the long short-term memory (LSTM) method. In addition, this study collected subjects in healthy control (HC), Parkinson’s disease (PD), and freezing of gait (FOG) groups for comparative analysis. The experimental results revealed differences in motion characteristics and kinematics between PD and healthy subjects. Thus, the quantitative analysis results can be used as an important reference for the clinical application of PD.

Real-time motion management for robotic treatment couch in proton therapy system

In proton therapy, robotic couch was used for patient positioning to achieve high precision in cancer treatment. However, no studies have focused on the real-time motion management system (MMS) for the robotic couch. This study was to develop the MMS and verify its feasibility. A real-time MMS was set up with a robotic couch, an NDI Vega optical tracking system, a Special Measurement Tool (SMT) and the developed software. A Leica laser tracker was adopted to verify the accuracy of the tests in this study. The stability and accuracy of the SMT in NDI Vega system were verified to guarantee the reliability of the results. The coordinate transformation was used to unify the measurement. 83 points inside the treatment volume were applied to verify the accuracy of the MMS, with the comparison of results measured by the laser tracker. The synchronism of the SMT in the MMS and Patient Positioning System (PPS) based on the reciprocating motion along axis z was tested to obtain the maximum time delay. Trajectory tracking was performed with different payloads on the couch top. A series of tests were conducted and the results demonstrated the feasibility of potential applications based on real-time motion capturing and monitoring.

Comparison of Passive and Active Fiducials for Optical Tracking

Abstract The paper analyses the constraints related to optical tracking of an HMD with a single commercial binocular stereoscopic optical tracking system and offers an overview of different factors affecting the best active fiducial set-up and marker geometries for reliable tracking with a focus on the rotational accuracy of a marker. Two IR diode models with different emission characteristics were tested as active fiducials and the results were compared to localization accuracy of passive fiducials. In terms of preferable marker geometry, it was found that the area enclosed by the fiducials should be maximized. Thus, due to geometrical constraints, very small marker geometries may not be stable or feasible entirely. Rotational accuracy was analysed for cases when the marker was not directly facing the tracking device and it was found that rotation about one axis introduced errors to the determined orientation in space related to the other axes as well.