Optical Tracking Device Research Articles

Impact of optical navigation variables on the accuracy of robot-assisted surgery: a study of the TIANJI Robot system.

This study aims to explore factors related to optical navigation that interfere with the accuracy of robot-assisted surgery, specifically focusing on the TIANJI Robot system. A measurement model was created to assess the accuracy of the TIANJI Robot system in simulated screw placement. Deviation between actual and planned positions was measured using a three-coordinate machine. Various experiments were conducted to investigate the impact of different optical navigation factors on screw placement accuracy. Deviations were measured at different distances (ranging from 1.2 to 2.2m) between the optical navigation stereo camera and the tracker, with each distance being tested 50 times. The distance between the optical camera and patient tracker was set at 1.4m. Deviations were also measured at different angles between the camera and robot tracker, repeated over 25 times for each angle. Data were analyzed using mean and standard deviation, with line charts illustrating deviation changes based on distance and angle details. Within the range of the TIANJI Robot system's optical navigation (1.2-2.2m), deviation increased as distance increased (χ2 = 479.107, P < 0.001). The robotic system demonstrated high and consistent accuracy (mean deviation: 0.332mm ± 0.067mm) when the relative angle between the optical camera and tracker was below 40°. The accuracy of the TIANJI Robot system was found to be influenced by relative distance and angle between the optical camera and tracker during screw placement procedures. Surgeons are recommended to set a relative distance of 1.4-1.5m between the optical camera and patient tracker, with a relative angle below 40° when placing and adjusting optical tracking devices.

TrackPose

Several studies have explored the estimation of finger pose/angle to enhance the expressiveness of touchscreens. However, the accuracy of previous algorithms is limited by large estimation errors, and the sequential output angles are unstable, making it difficult to meet the demands of practical applications. We believe the defect arises from improper rotation representation, the lack of time-series modeling, and the difficulty in accommodating individual differences among users. To address these issues, we conduct in-depth study of rotation representation for the 2D pose problem by minimizing the errors between representation space and original space. A deep learning model, TrackPose, using a self-attention mechanism is proposed for time-series modeling to improve accuracy and stability of finger pose. A registration application on a mobile phone is developed to collect touchscreen images of each new user without the use of optical tracking device. The combination of the three measures mentioned above has resulted in a 33% reduction in the angle estimation error, 47% for the yaw angle especially. Additionally, the instability of sequential estimations, measured by the proposed metric MAEΔ, is reduced by 62%. User study further confirms the effectiveness of our proposed algorithm.

Markerless head motion tracking and event-by-event correction in brain PET

Objective. Head motion correction (MC) is an essential process in brain positron emission tomography (PET) imaging. We have used the Polaris Vicra, an optical hardware-based motion tracking (HMT) device, for PET head MC. However, this requires attachment of a marker to the subject’s head. Markerless HMT (MLMT) methods are more convenient for clinical translation than HMT with external markers. In this study, we validated the United Imaging Healthcare motion tracking (UMT) MLMT system using phantom and human point source studies, and tested its effectiveness on eight 18F-FPEB and four 11C-LSN3172176 human studies, with frame-based region of interest (ROI) analysis. We also proposed an evaluation metric, registration quality (RQ), and compared it to a data-driven evaluation method, motion-corrected centroid-of-distribution (MCCOD). Approach. UMT utilized a stereovision camera with infrared structured light to capture the subject’s real-time 3D facial surface. Each point cloud, acquired at up to 30 Hz, was registered to the reference cloud using a rigid-body iterative closest point registration algorithm. Main results. In the phantom point source study, UMT exhibited superior reconstruction results than the Vicra with higher spatial resolution (0.35 ± 0.27 mm) and smaller residual displacements (0.12 ± 0.10 mm). In the human point source study, UMT achieved comparable performance as Vicra on spatial resolution with lower noise. Moreover, UMT achieved comparable ROI values as Vicra for all the human studies, with negligible mean standard uptake value differences, while no MC results showed significant negative bias. The RQ evaluation metric demonstrated the effectiveness of UMT and yielded comparable results to MCCOD. Significance. We performed an initial validation of a commercial MLMT system against the Vicra. Generally, UMT achieved comparable motion-tracking results in all studies and the effectiveness of UMT-based MC was demonstrated.

A clinical comparison of sagittal condylar inclination and Bennett angle derived from a conventional electronic tracking device and an optical jaw tracking device

The challenges of conventional methods to measure the sagittal condylar inclination and the Bennett angle include patient discomfort and an output of averaged values calculated on the arc of mandibular movement. Programming these average values into a mechanical or mathematically simulated articulator may introduce occlusal errors. The purpose of this clinical study was to compare the sagittal condylar inclination and Bennett angle measurements derived from a conventional electronic tracking device and an optical tracking device. Fifteen dentate participants with at least 12 occluding units, 25 years old and above, participated in the study. Each participant's mandibular movements were recorded by the 2 systems for different condylar guidance values. A conventional tracking device, the Cadiax Compact 2, and an optical tracking device, the MODJAW, were used for this study. Sagittal condylar inclination was measured at 3mm and 5mm using protrusive records and the values of the Bennett angle at 3mm were measured using excursive records along the path traced by mandibular condyles. The Wilcoxon signed-rank test was used to analyze the paired data from the 2 methods. A significant difference was found between right (P=.007) and left sagittal condylar inclinations (P=.010) measured at 3mm with the conventional and optical tracking devices. A significant difference was found between right (P=.015) and left sagittal condylar inclinations (P=.004) measured at 5mm with the conventional and optical tracking devices. The right and left Bennett angles measured at 3mm with the conventional and optical tracking devices were statistically different (P=.043 and P=.035 respectively). The sagittal condylar inclination and Bennett angle measured at different positions along the path of movement exhibited significant differences. The sagittal condylar inclination and Bennett angle values obtained from the conventional tracking device were generally significantly less than those derived from the optical tracking device.

Inertial Measurement Unit-Assisted Ultrasonic Tracking System for Ultrasound Probe Localization.

Ultrasonic tracking is a promising technique in indoor object localization. However, limited success has been reported in dynamic orientational and positional ultrasonic tracking for ultrasound (US) probes due to its instability and relatively low accuracy. This article aims at developing an inertial measurement unit (IMU)-assisted ultrasonic tracking system that enables a high accuracy positional and orientational localization. The system was designed with the acoustic pressure field simulation of the transmitter, receiver configuration, position-variant error simulation, and sensor fusion. The prototype was tested in a tracking volume required in typical obstetric sonography within the typical operation speed ranges (slow mode and fast mode) of US probe movement. The performance in two different speed ranges was evaluated against a commercial optical tracking device. The results show that the proposed IMU-assisted US tracking system achieved centimeter-level positional tracking accuracy with the mean absolute error (MAE) of 12 mm and the MAE of orientational tracking was less than 1°. The results indicate the possibility of implementing the IMU-assisted ultrasonic tracking system in US probe localization.

A Dynamic Elbow Testing Apparatus for Simulating Elbow Joint Motion in Varying Shoulder Positions

To develop and evaluate the capabilities of a dynamic elbow testing apparatus that simulates unconstrained elbow motion throughout the range of humerothoracic (HTA) abduction. Elbow flexion was generated by six computer-controlled electromechanical actuators that simulated muscle action, while six degree-of-freedom joint motion was measured using an optical tracking device. Repeatability of joint kinematics was assessed at four HTA angles (0°, 45°, 90°, 135°) and with two muscle force combinations (A1-biceps brachialis, brachioradialis and A2-biceps, brachioradialis). Repeatability was determined by comparing kinematics at every 10° of flexion over five flexion-extension cycles (0° to 100°). Multiple muscle force combinations can be used at each HTA angle to generate elbow flexion. Trials showed that the testing apparatus produced highly repeatable joint motion at each HTA angle and with varying muscle force combinations. The intraclass correlation coefficient was greater than 0.95 for all conditions. Repeatable smooth cadaveric elbow motion was created that mimicked the invivo situation. These results suggest that the dynamic elbow testing apparatus can be used to characterize elbow biomechanics in cadaver upper extremities.

Super-resolution in brain positron emission tomography using a real-time motion capture system

Super-resolution (SR) is a methodology that seeks to improve image resolution by exploiting the increased spatial sampling information obtained from multiple acquisitions of the same target with accurately known sub-resolution shifts. This work aims to develop and evaluate an SR estimation framework for brain positron emission tomography (PET), taking advantage of a high-resolution infra-red tracking camera to measure shifts precisely and continuously. Moving phantoms and non-human primate (NHP) experiments were performed on a GE Discovery MI PET/CT scanner (GE Healthcare) using an NDI Polaris Vega (Northern Digital Inc), an external optical motion tracking device. To enable SR, a robust temporal and spatial calibration of the two devices was developed as well as a list-mode Ordered Subset Expectation Maximization PET reconstruction algorithm, incorporating the high-resolution tracking data from the Polaris Vega to correct motion for measured line of responses on an event-by-event basis. For both phantoms and NHP studies, the SR reconstruction method yielded PET images with visibly increased spatial resolution compared to standard static acquisitions, allowing improved visualization of small structures. Quantitative analysis in terms of SSIM, CNR and line profiles were conducted and validated our observations. The results demonstrate that SR can be achieved in brain PET by measuring target motion in real-time using a high-resolution infrared tracking camera.

VentroAR: an augmented reality platform for ventriculostomy using the Microsoft HoloLens

ABSTRACT Freehand ventriculostomy is one of the most common neurosurgical procedures performed when cerebrospinal fluid increases in the ventricular system causing an increase in intracranial pressure. In freehand ventriculostomy, surgeons use anatomical landmarks to determine where to make a burr hole on the skull and insert a catheter inside the brain to drain cerebrospinal fluid. Often, several insertion attempts are required to successfully reach the ventricular target. Misplacement of catheter in ventriculostomy can cause complications such as infection, haemorrhage and longer hospitalisations. In this paper, we introduce an augmented reality pipeline using an optical tracking device and HoloLens to help surgeons locate ventricles more easily and reduce the risk associated with this procedure. The proposed system, VentroAR, was evaluated in a user study with 15 subjects. We found that the gesture-based registration accuracy was on average 10.75 mm and targeting accuracy was 10.64 mm. Although the HoloLens shows promise in terms of workflow and ease of use, more work needs to be done to improve accuracy for clinical acceptance.

Stereotactic navigation using registration based on intra-abdominal landmarks in robotic-assisted lateral pelvic lymph node dissection.

We carried out robot-assisted lateral pelvic lymph node dissection (LPLND) for rectal cancer with a stereotactic navigation system. The purpose of this study was to evaluate the accuracy and feasibility of the system. We constructed a navigation system based on the Polaris Spectra optical tracking device (Northern Digital Inc., Canada) and the open-source software 3D Slicer (version 3.8.1; http://www.slicer.org ). We used the landmark-based registration method for patient-to-image registration. Body surface landmarks and intra-abdominal landmarks were used. We evaluated the time required for registration and target registration error (TRE; the distance between corresponding points after registration) for the root of the superior gluteal artery the root of the obturator or superior vesical artery, and the obturator foramen during minimally invasive LPLND for rectal cancer. Five patients who had LPLND for rectal cancer at the University of Tokyo Hospital between September 2020 and May 2021 were enrolled. The mean time required for registration was 49s with the body surface landmarks and 88s with the intra-abdominal landmarks. The mean TRE improved markedly when the registration was performed using intra-abdominal landmarks. The mean TRE of the root of the superior gluteal artery, the root of the obturator or superior vesical artery, and the obturator foramen were 55.8mm, 53.4mm, and 55.2mm with the body surface landmarks and 11.8mm, 10.0mm, and 12.6mm with the intra-abdominal landmarks, respectively. There were no adverse events related to the registration process. When stereotactic navigation systems are used for minimally invasive LPLND, the use of intra-abdominal landmarks for registration is feasible and may allow simpler and more accurate navigation than the use of body surface landmarks.

A comparative analysis of two immersive virtual reality systems in the integration and visualization of natural hand interaction

It is generally accepted that the use of natural interaction provides a positive impact in Virtual Reality (VR) applications. Therefore, it is important to understand what is the best way to integrate and visualize this feature in VR. For this reason, this paper presents a comparative study of the integration of natural hand interaction in two immersive VR systems: a Cave Audio Visual Experience (CAVE) system –where users’ real hands are visible– and a non-see-through Head-Mounted Display (HMD) system –where only a virtual representation of the hands is possible–. In order to test the suitability of using this type of interaction in a CAVE and compare it to an HMD, we raise six research questions related to task performance, usability and perception differences regarding natural hand interaction with these two systems. To answer these questions, we designed an experiment where users have to complete a pick-and-place task with virtual balls and a text-typing task with virtual keyboards. In both systems, the same tracking technology, based on a Leap Motion device, was used. To the best of our knowledge this is the first academic work addressing a comparison of this type. Objective and subjective data were collected during the experiments. The results show that the HMD has a performance, preference and usability advantage over the CAVE with respect to the integration of natural hand interaction. Nevertheless, the results also show that the CAVE system can be, as well, successfully used in combination with an optical hand tracking device.

Multi-Modality guidance based surgical navigation for percutaneous endoscopic transforaminal discectomy

ObjectiveFluoroscopic guidance is a critical step for the puncture procedure in percutaneous endoscopic transforaminal discectomy (PETD). However, two-dimensional observations of the three-dimensional anatomic structure suffer from the effects of projective simplification. To accurately assess the spatial relations between the patient vertebra tissues and puncture needle, a considerable number of fluoroscopic images from different orientations need to be acquired by the surgeons. This process significantly increases the radiation risk for both the patient and surgeons. MethodsIn this paper, we propose an augmented reality (AR) surgical navigation system for PETD based on multi-modality information, which contains fluoroscopy, optical tracking, and depth camera. To register the fluoroscopic image with the intraoperative video, we design a lightweight non-invasive fiducial with markers and detect the markers based on the deep learning method. It can display the intraoperative video fused with the registered fluoroscopic images. We also present a self-adaptive calibration and transformation method between a 6-DOF optical tracking device and a depth camera, which are in different coordinate systems. ResultsWith the substantially reduced frequency of fluoroscopy imaging, the system can accurately track and superimpose the virtual puncture needle on fluoroscopy images in real-time. From operating theatre in vivo animal experiments, the results illustrate that the system average positioning accuracy can reach 1.98mm and the orientation accuracy can reach 1.19∘. From the clinical validation results, the system significantly lower the frequency of fluoroscopy imaging (42.7%) and reduce the radiation risk for both the patient and surgeons. ConclusionCoupled with the user study, both the quantitative and qualitative results indicate that our navigation system has the potential to be highly useful in clinical practice. Compared with the existing navigation systems, which are usually equipped with a variety of large and high-cost medical equipments, such as O-arm, cone-beam CT, and robots, our navigation system does not need special equipment and can be implemented with common equipment in the operating room, such as C-arm, desktop, etc., even in small hospitals.

Automatic robot-world calibration in an optical-navigated surgical robot system and its application for oral implant placement.

Robot-world calibration, used to precisely determine the spatial relation between optical tracker and robot, is regarded as an essential step for optical-navigated surgical robot system to improve the surgical accuracy. However, these methods are complicated with numerous computation. Therefore, a more efficient method of a robot-world calibration is necessary. A fully automatic robot-world calibration was proposed and applied in a surgical robot system for oral implant placement. Making full usage of the movement characteristics of a tandem robot, the least square fitting algorithm was implemented to calculate the relationship between the tool center point of the robot and the robot reference frame, with the robot-world calibration matrix obtained as result. The experiment was designed to verify the accuracy of the robot-world calibration. The average distance deviation was 1.11mm, and the average angle deviation was 0.99°. From the animal experiment on the pig maxilla, the entry, apical and angle deviation of the surgical robot system were 1.44 ± 1.01mm, 1.68 ± 0.76mm, 1.01 ± 1.06°, respectively. The surgical robot system for oral implant placement with our robot-world calibration maintains a high precision. Besides, the operation range of the surgical tool is no longer limited by the visual range of the optical tracking device. Hence, it is unnecessary to adjust the optical tracking device for the planned implant trajectories to different positions and directions.

Augmented reality for dental implant surgery: enhanced ICP

Augmented reality surgery has not been successfully implemented in dental implant surgery due to the negative impact of an incorrect implant placement. This research aimed to improve the convergence between computed tomography derived teeth model and real-time stereo view of patient’s teeth to provide high registration accuracy. Enhanced iterative closest point algorithm is proposed to reduce the error caused due to matching wrong points. Weighting mechanism and median value are used to reduce alignment error caused due to matching wrong points. In addition, random sample consensus (RANSAC) algorithm is used to detect and remove the outlier. Furthermore, the current solution for dental implants did not provide the position and orientation of the surgical tool, and without this information, there is a risk of damaging adjacent structure, dental nerves, and root canals. Optical tracking device is used in the proposed solution to address this information and ensure that nerve does not get damaged during the dental implant placement surgery. While the state-of-the-art solution provided 0.44 mm registration accuracy, the proposed solution was improving it by providing 0.33 mm registration accuracy. Additionally, the proposed system can produce good results despite not having a good initialization. The processing time improved to 14 fps in comparison to the 9-fps given by state-of-the-art solution. The proposed system improved the accuracy of convergence and the processing time compared to the globally optimal-ICP algorithm. We also employed RANSAC algorithm to detect and remove the outlier on the estimation and reduce the influence of extreme points.

Modeling and Clinical Application of Incision Space in Facial Contour Surgery.

Virtual simulation surgical system is a good way to develop surgical instruments, make surgical plan, and train surgeons. At present, due to the deformation of intraoperative soft tissue after retraction and the lack of effective data collection, the surgical simulation of facial contour surgery can only be conducted according to the preoperative computed tomography data. Due to the difficulty of obtaining real operative spatial data, it is difficult for the virtual surgery trajectory planning process to yield a good effect on surgeon training. In this study, an optical tracking device was used to record the actual posture of surgical instruments, patient position, and incision space in the surgical environment, so as to construct a more accurate actual surgical space. The clinical data obtained in this study can be used for virtual simulation of surgical instrument movement and osteotomy, as well as selection, planning, and teaching purposes of surgical programs.

A Skin-Conformal, Stretchable, and Breathable Fiducial Marker Patch for Surgical Navigation Systems

Augmented reality (AR) surgical navigation systems have attracted considerable attention as they assist medical professionals in visualizing the location of ailments within the human body that are not readily seen with the naked eye. Taking medical imaging with a parallel C-shaped arm (C-arm) as an example, surgical sites are typically targeted using an optical tracking device and a fiducial marker in real-time. These markers then guide operators who are using a multifunctional endoscope apparatus by signaling the direction or distance needed to reach the affected parts of the body. In this way, fiducial markers are used to accurately protect the vessels and nerves exposed during the surgical process. Although these systems have already shown potential for precision implantation, delamination of the fiducial marker, which is a critical component of the system, from human skin remains a challenge due to a mechanical mismatch between the marker and skin, causing registration problems that lead to poor position alignments and surgical degradation. To overcome this challenge, the mechanical modulus and stiffness of the marker patch should be lowered to approximately 150 kPa, which is comparable to that of the epidermis, while improving functionality. Herein, we present a skin-conformal, stretchable yet breathable fiducial marker for the application in AR-based surgical navigation systems. By adopting pore patterns, we were able to create a fiducial marker with a skin-like low modulus and breathability. When attached to the skin, the fiducial marker was easily identified using optical recognition equipment and showed skin-conformal adhesion when stretched and shrunk repeatedly. As such, we believe the marker would be a good fiducial marker candidate for patients under surgical navigation systems.

Intuitive gesture-based control system with collision avoidance for robotic manipulators

PurposeThis paper aims to present an intuitive control system for robotic manipulators that pairs a Leap Motion, a low-cost optical tracking and gesture recognition device, with the ability to record and replay trajectories and operation to create an intuitive method of controlling and programming a robotic manipulator. This system was designed to be extensible and includes modules and methods for obstacle detection and dynamic trajectory modification for obstacle avoidance.Design/methodology/approachThe presented control architecture, while portable to any robotic platform, was designed to actuate a six degree-of-freedom robotic manipulator of our own design. From the data collected by the Leap Motion, the manipulator was controlled by mapping the position and orientation of the human hand to values in the joint space of the robot. Additional recording and playback functionality was implemented to allow for the robot to repeat the desired tasks once the task had been demonstrated and recorded.FindingsExperiments were conducted on our custom-built robotic manipulator by first using a simulation model to characterize and quantify the robot’s tracking of the Leap Motion generated trajectory. Tests were conducted in the Gazebo simulation software in conjunction with Robot Operating System, where results were collected by recording both the real-time input from the Leap Motion sensor, and the corresponding pose data. The results of these experiments show that the goal of accurate and real-time control of the robot was achieved and validated our methods of transcribing, recording and repeating six degree-of-freedom trajectories from the Leap Motion camera.Originality/valueAs robots evolve in complexity, the methods of programming them need to evolve to become more intuitive. Humans instinctively teach by demonstrating the task to a given subject, who then observes the various poses and tries to replicate the motions. This work aims to integrate the natural human teaching methods into robotics programming through an intuitive, demonstration-based programming method.

The use of sonification for physiotherapy in human movement tasks: A scoping review

Summary Objectives This review aims to: (1) map the use of sonification in human movement tasks for physical therapy; (2) identify methods of data capture, tasks and its effects on human subjects; (3) suggest future research directions. News Sonification can be described as a technique to translate data into sound. It has been used for human motion analysis tasks even if it is not part of most physical therapist's lexicon. Prospects and projects Identify and analyze publications where sonification was used as an audio-feedback technique for physical therapy. Thirty-five papers were included, 13 randomized-control-trials. Thirteen papers reported an investigation on a specific dysfunction, while upper limb movements were investigated in fifteen papers. Inertial measurement units were the most commonly used technology to capture human movement, 10 papers reported improvements in motor control and/or movement quality. Gaps in the literature were identified: (1) absence of sonification framework for rehabilitation, (2) no long-term comparison with gold-standard interventions for specific populations, (3) approaches for cardio-respiratory physical therapy and injury prevention were absent. Conclusion Sonification has the potential to support rehabilitation for physical therapy. Effects of sonification were varied and ranged from improvements in movement quality/control, increased movement and body-awareness and improvements in performance when compared with activities with audio-visual or non-specific audio-feedback among others. Data for sonification was mainly captured using inertial measurement units, smartphones and optical tracking devices but others are also commonly used. Well-designed clinical trials supported by current promising results need to be developed. We recommend testing different sonification techniques in common physical therapy disfunctions using significant outcome measures to understand and maximize its effects on motor learning and control while scoping for further benefits.

Non-orthogonal one-step calibration method for robotized transcranial magnetic stimulation

BackgroundRobotized transcranial magnetic stimulation (TMS) combines the benefits of neuro-navigation with automation and provides a precision brain stimulation method. Since the coil will normally remain unmounted between different clinical uses, hand/eye calibration and coil calibration are required before each experiment. Today, these two steps are still separate: hand/eye calibration is performed using methods proposed by Tsai/Lenz or Floris Ernst, and then the coil calibration is carried out based on the traditional TMS experimental step. The process is complex and time-consuming, and traditional coil calibration using a handheld probe is susceptible to greater calibration error.MethodsA novel one-step calibration method has been developed to confirm hand/eye and coil calibration results by formulating a matrix equation system and estimating its solution. Hand/eye calibration and coil calibration are performed to confirm the pose relationships of the marker/end effector ‘X’, probe/end effector ‘Y’, and robot/world ‘Z’. First, the coil is fixed on the end effector of the robot. During the one-step calibration process, a marker is mounted on the top of the coil and a calibration probe is fixed at the actual effective position of the coil. Next, the robot end effector is moved to a series of random positions ‘A’, the tracking data of marker ‘B’ and probe ‘C’ is obtained correspondingly. Then, a matrix equation system AX = ZB and AY = ZC can be acquired, and it is computed using a least-squares approach. Finally, the calibration probe is removed after calibration, while the marker remains fixed to the coil during the TMS experiment. The methods were evaluated based on simulation data and on experimental data from an optical tracking device. We compared our methods with two classical methods: the QR24 method proposed by Floris Ernst and the handheld coil calibration method.ResultsThe new methods outperform the QR24 method in the aspect of translational accuracy and performs similarly in the aspect of rotational accuracy, the total translational error decreased more than fifty percent. The new approach also outperforms traditional handheld coil calibration of navigated TMS systems, the total translational error decreased three- to fourfold, and the rotational error decreased six- to eightfold. Furthermore, the convergence speed is improved 16- to 27-fold for the new algorithms.ConclusionThese results suggest that the new method can be used for hand/eye and coil calibration of a robotized TMS system. Two complex steps can be simplified using a least-squares approach.

An Inexpensive and Easy to Use Cervical Range of Motion Measurement Solution Using Inertial Sensors.

Neck injuries and the related pain have a high prevalence and represent an important health problem. To properly diagnose and treat them, practitioners need an accurate system for measuring Cervical Range Of Motion (CROM). This article describes the development and validation of an inexpensive, small (4 cm × 4 cm × 8 cm), light (< 200 g) and easy to use solution for measuring CROM using wearable inertial sensors. The proposed solution has been designed with the clinical practice in mind, after consulting with practitioners. It is composed of: (a) two wearable wireless MEMS-based inertial devices, (b) a recording and report generation software application and (c) a measurement protocol for assessing CROM. The solution provides accurate (none of our results is outside the ROM ranges when compared with previously published results based on an optical tracking device) and reliable measurements (ICC = 0.93 for interrater reliability when compared with an optical tracking device and ICC > 0.90 for test-retest reliability), surpassing the popular CROM instrument’s capabilities and precision. It also fulfills the needs for clinical practice attending to effectiveness, efficiency (4 min from setup to final report) and user’s satisfaction (as reported by practitioners). The solution has been certified for mass-production and use in medical environments.

Mid-air interaction with optical tracking for 3D modeling

Compared to common 2D interaction done with mouse and other 2D tracking devices, 3D hand tracking with low-cost optical cameras can provide more degrees of freedom, as well as natural gestures, when shape modeling is done in virtual spaces. However, though quite precise, the optical tracking devices cannot avoid problems intrinsic to hand interaction, such as hand tremor and jump release, and they also introduce an additional problem of hand occlusion. We investigate how to minimize the negative impact of these problems, and eventually propose to use hands in a way similar to how it is done when playing the Theremin – an electronic musical instrument controlled without physical contact by hands of the performer. We suggest that the dominant hand controls manipulation and deformation of objects while the non-dominant hand controls grasping, releasing and precision of interaction. Based on this method, we describe a generic set of reliable and precise interaction gestures for various manipulation and deformation tasks. We then prove with the user study that for the tasks involving 3D manipulations and deformations, hand interaction is faster than common 2D interaction done with mouse.