Real-Time Noncoherent UWB Positioning Radar With Millimeter Range Accuracy: Theory and Experiment

In this paper, we propose a novel architecture for ultra-wideband (UWB) positioning systems, which combines the architectures of carrier-based UWB systems and traditional energy detection-based UWB systems. By implementing the novel architecture, we have successfully developed a standalone noncoherent system for positioning both static and dynamic targets in an indoor environment with approximately 2 and 5 mm of 3-D accuracy, respectively. The results are considered a great milestone in developing such technology. 1-D and 3-D experiments have been carried out and validated using an optical reference system, which provides better than 0.3-mm 3-D accuracy. This type of indoor high-accuracy wireless localization system has many unique applications including robot control, surgical navigation, sensitive material monitoring, and asset tracking.      

A 3-D reconstruction system for the human jaw using a sequence of optical images

This paper presents a model-based vision system for dentistry that will assist in diagnosis, treatment planning, and surgical simulation. Dentistry requires an accurate three-dimensional (3-D) representation of the teeth and jaws for diagnostic and treatment purposes. The proposed integrated computer vision system constructs a 3-D model of the patient's dental occlusion using an intraoral video camera. A modified shape from shading (SFS) technique, using perspective projection and camera calibration, extracts the 3-D information from a sequence of two-dimensional (2-D) images of the jaw. Data fusion of range data and 3-D registration techniques develop the complete jaw model. Triangulation is then performed, and a solid 3-D model is reconstructed. The system performance is investigated using ground truth data, and the results show acceptable reconstruction accuracy.     

Computer-aided stereotactic functional neurosurgery enhanced by the use of the multiple brain atlas database

This paper introduces a computer-aided atlas-based functional neurosurgery methodology and describes NeuroPlanner, a software system which supports it. NeuroPlanner provides four groups of functions: 1) data-related for data reading, interpolation, reformatting, and image processing; 2) atlas-related for multiple atlases reading, atlas-to-data global and local registrations, two-way anatomical indexing, and multiple labeling in two and three dimensions; 3) atlas-data exploration-related for three-dimensional (3-D) display and real-time manipulation of cerebral structures, continuous navigation, two-dimensional (2-D), triplanar, 3-D presentations, and 2-D interaction in four views; and 4) neurosurgery-related for targeting, trajectory planning, mensuration, simulating the insertion of microelectrode, and simulating therapeutic lesioning. All operations, excluding atlas and data reading, are real time. The combined anatomical index of the multiple brain atlas database containing complementary 2-D and 3-D atlases has about 1000 structures per hemisphere, and over 400 sulcal patterns. Neurosurgical planning with mutually preregistered multiple brain atlases in all three orthogonal orientations is novel. The approach is validated with 24 intraoperative and postoperative datasets for thalamotomies, thalamic stimulations, pallidotomies, and pallidal stimulations. Its potential benefits include increased accuracy of target definition, reduced time of the surgical procedure by decreasing the number of tracts, facilitated planning of more sophisticated trajectories, lowered cost by reducing the number of microelectrodes used, reduced surgical complications, and the extra degree of confidence given to the neurosurgeon.     

A Novel Manipulator for Percutaneous Needle Insertion: Design and Experimentation

In this paper, we present the design of a novel 5-DOF manipulator for percutaneous needle insertion. The requirements of the manipulator have been instigated by a relatively common medical procedure: low-dose rate brachytherapy of the prostate. The manipulator can perform orientation, insertion, and rotation of the needle and linear motion of the stylet to drop radioactive seeds contained in a thin hollow needle (cannula) at targeted locations. The key features of the manipulator such as backdrivable joints, a fault-tolerant needle driver, stationary actuators, and redundant sensors enhance overall safety and reliability of the mechanism, a critical requirement for surgical manipulators. The manipulator is an integral part of a system utilizing a mechanically rotated side-firing transducer to create 3-D ultrasound images of the organ and utilizing 3-D SLICER software to visualize those images. Experimental results in agar phantoms prove that the manipulator is capable of positioning the needle tip at the targeted locations with good accuracy.      

RSSI-Based Indoor Localization and Tracking Using Sigma-Point Kalman Smoothers

Solutions for indoor tracking and localization have become more critical with recent advancement in context and location-aware technologies. The accuracy of explicit positioning sensors such as global positioning system (GPS) is often limited for indoor environments. In this paper, we evaluate the feasibility of building an indoor location tracking system that is cost effective for large scale deployments, can operate over existing Wi-Fi networks, and can provide flexibility to accommodate new sensor observations as they become available. This paper proposes a sigma-point Kalman smoother (SPKS)-based location and tracking algorithm as a superior alternative for indoor positioning. The proposed SPKS fuses a dynamic model of human walking with a number of low-cost sensor observations to track 2-D position and velocity. Available sensors include Wi-Fi received signal strength indication (RSSI), binary infra-red (IR) motion sensors, and binary foot-switches. Wi-Fi signal strength is measured using a receiver tag developed by Ekahau, Inc. The performance of the proposed algorithm is compared with a commercially available positioning engine, also developed by Ekahau, Inc. The superior accuracy of our approach over a number of trials is demonstrated.     

Computer system for craniofacial surgical planning based on CT images

A system for craniofacial surgical planning utilizing stacks of 2-D tomographic images is described. The four parts of the system are image generation, 2-D surgical planning, 3-D plan confirmation, and rough prediction of face shape after an operation. The four parts are combined to provide a useful surgical planning system. Because a gradient shading technique is used for generating 3-D images, the bumpy shape of the voxel (volume element for 3-D objects) sometimes obscures the essential shape of the displayed objects. To smooth undesirable bumps without losing the essential object shape, 2-D filtering is applied. Arbitrary bone blocks can be specified and moved interactively with a graphic terminal to any derived location to aid surgical planning. The chosen plan can be confirmed by observing computer-generated 3-D images from arbitrary directions since the process necessary to generate a 3-D image for any one direction should be adequate for all directions. Postoperative face-shape prediction is available for evaluating the operation plan at the last stage of the planning sequence.     

Markerless real-time 3-D target region tracking by motion backprojection from projection images

Accurate and fast localization of a predefined target region inside the patient is an important component of many image-guided therapy procedures. This problem is commonly solved by registration of intraoperative 2-D projection images to 3-D preoperative images. If the patient is not fixed during the intervention, the 2-D image acquisition is repeated several times during the procedure, and the registration problem can be cast instead as a 3-D tracking problem. To solve the 3-D problem, we propose in this paper to apply 2-D region tracking to first recover the components of the transformation that are in-plane to the projections. The 2-D motion estimates of all projections are backprojected into 3-D space, where they are then combined into a consistent estimate of the 3-D motion. We compare this method to intensity-based 2-D to 3-D registration and a combination of 2-D motion backprojection followed by a 2-D to 3-D registration stage. Using clinical data with a fiducial marker-based gold-standard transformation, we show that our method is capable of accurately tracking vertebral targets in 3-D from 2-D motion measured in X-ray projection images. Using a standard tracking algorithm (hyperplane tracking), tracking is achieved at video frame rates but fails relatively often (32% of all frames tracked with target registration error (TRE) better than 1.2 mm, 82% of all frames tracked with TRE better than 2.4 mm). With intensity-based 2-D to 2-D image registration using normalized mutual information (NMI) and pattern intensity (PI), accuracy and robustness are substantially improved. NMI tracked 82% of all frames in our data with TRE better than 1.2 mm and 96% of all frames with TRE better than 2.4 mm. This comes at the cost of a reduced frame rate, 1.7 s average processing time per frame and projection device. Results using PI were slightly more accurate, but required on average 5.4 s time per frame. These results are still substantially faster than 2-D to 3-D registration. We conclude that motion backprojection from 2-D motion tracking is an accurate and efficient method for tracking 3-D target motion, but tracking 2-D motion accurately and robustly remains a challenge.     

Integration of Ground-Penetrating Radar and Laser Position Sensors for Real-Time 3-D Data Fusion

Full-resolution 3-D ground-penetrating radar (GPR) imaging of the near surface should be simple and efficient. Geoscientists, archeologists, and engineers need a tool capable of generating interpretable subsurface views at centimeter-to-meter resolution of field sites ranging from smooth parking lots to rugged terrain. The authors have integrated novel rotary laser positioning technology with GPR into such a 3-D imaging system. The laser positioning enables acquisition of centimeter accurate x, y, and z coordinates from multiple small detectors attached to moving GPR antennas. Positions streaming with 20 updates/s from each detector are fused in real time with the GPR data. The authors developed software for automated data acquisition and real time 3-D GPR data quality control on slices at selected depths. Industry standard (SEGY) format data cubes and animations are generated within an hour after the last trace has been acquired. Such instant 3-D GPR can be used as an on-site imaging tool supporting field work, hypothesis testing, and optimized excavation and sample collection in the exploration of the static and dynamic nature of the shallow subsurface     

CRIGOS: a compact robot for image-guided orthopedic surgery

The CRIGOS (compact robot for image-guided orthopedic surgery) project was set up for the development of a compact surgical robot system for image-guided orthopedic surgery based on user requirements. The modular system comprises a compact parallel robot and a software system for planning of surgical interventions and for supervision of the robotic device. Because it is not sufficient to consider only technical aspects in order to improve clinical routines the therapeutic outcome of conventional interventions, a user-centered and task-oriented design process has been developed which also takes human factors into account. The design process for the CRIGOS system was started from requirement analysis of various orthopedic interventions using information gathered from literature, questionnaires, and workshops with domain experts. This resulted in identification of conventional interventions for which the robotic system would improve the medical and procedural quality. A system design concept has been elaborated which includes definitions of components, functionalities, and interfaces, Approaches to the acquisition of calibrated X-rays will be presented in the paper together with design and evaluation of a first human-computer interface. Finally, the first lab-type parallel robot based on low-cost standard components is presented together with the first evaluation results concerning positioning accuracy     

Registration of three-dimensional cardiac catheter models to single-plane fluoroscopic images

Transvenous cardiac procedures require accurate positioning of catheters within the geometrically complex cavities of the heart. Recently, nonfluoroscopic catheter tracking technologies have been developed to quantitate the (degrees-of-freedom) three-dimensional positions of intracardiac catheters. This paper presents a projection-Procrustes method to register an animated three-dimensional (3-D) model of multiple intracardiac catheters with a single-plane fluoroscopic image. Applying the computed transformation to the catheter coordinates enables the animated 3-D model of the catheters to be viewed from the same perspective as the fluoroscopic image. Mathematical simulations show that the computed transformation parameters are sensitive to both the position errors in the 3-D catheter coordinates and to the spatial distribution of the catheter-mounted transducers. Simulations with a realistic geometric model of three catheters with four transducers per catheter showed an angular error of 1.91 degrees +/- 0.27 degree for 3-D catheter position errors of 2.0 mm. An in vitro experiment demonstrated the feasibility of the method using a water tank phantom of three catheters and fluoroscopic images taken over an 80 degrees range. The mean angular error was 0.61 degree +/- 0.48 degree. The results of this study indicate that the projection-Procrustes method is a useful tool for registering 3-D catheter tracking models to single-plane fluoroscopic images.     

Two-dimensional mesh-based mosaic representation for manipulationof video objects with occlusion

We present a two-dimensional (2-D) mesh-based mosaic representation, consisting of an object mesh and a mosaic mesh for each frame and a final mosaic image, for video objects with mildly deformable motion in the presence of self and/or object-to-object (external) occlusion. Unlike classical mosaic representations where successive frames are registered using global motion models, we map the uncovered regions in the successive frames onto the mosaic reference frame using local affine models, i.e., those of the neighboring mesh patches. The proposed method to compute this mosaic representation is tightly coupled with an occlusion adaptive 2-D mesh tracking procedure, which consist of propagating the object mesh frame to frame, and updating of both object and mosaic meshes to optimize texture mapping from the mosaic to each instance of the object. The proposed representation has been applied to video object rendering and editing, including self transfiguration, synthetic transfiguration, and 2-D augmented reality in the presence of self and/or external occlusion. We also provide an algorithm to determine the minimum number of still views needed to reconstruct a replacement mosaic which is needed for synthetic transfiguration. Experimental results are provided to demonstrate both the 2-D mesh-based mosaic synthesis and two different video object editing applications on real video sequences.     

Depth-buffer targeting for spatially accurate 3-D visualization of medical images

During interactive image-guided surgery (IIGS), a surgeon uses data from medical images to help guide the surgical procedure. At Vanderbilt University, an IIGS software system called Orion has been developed which is capable of displaying up to four 512 x 512 images and the current surgical position using an active optical tracking system. Orion is capable of displaying data from any tomographic image volume and from any NTSC video image. An additional display module has been implemented to display three-dimensional information as well as the tomographic slices. This provides the surgeon with valuable anatomical information that is not readily obtained from the tomographic slices alone. Before the surgery, a set of rendered images is created, each with a different angular view of the tomographic volume in order to surround the site of surgical interest. The major objectives of the display module are to display the appropriate rendered image from the set, identify the current probe position on the selected image, and provide an indication of distance between the probe and the physical point of the anatomy indicated on the image. This can provide the surgeon with vital information such as distance to blood vessels, tumors, or other critical structures.     

Intraoperative laparoscope augmentation for port placement and resection planning in minimally invasive liver resection

In recent years, an increasing number of liver tumor indications were treated by minimally invasive laparoscopic resection. Besides the restricted view, two major intraoperative issues in laparoscopic liver resection are the optimal planning of ports as well as the enhanced visualization of (hidden) vessels, which supply the tumorous liver segment and thus need to be divided (e.g., clipped) prior to the resection. We propose an intuitive and precise method to plan the placement of ports. Preoperatively, self-adhesive fiducials are affixed to the patient's skin and a computed tomography (CT) data set is acquired while contrasting the liver vessels. Immediately prior to the intervention, the laparoscope is moved around these fiducials, which are automatically reconstructed to register the patient to its preoperative imaging data set. This enables the simulation of a camera flight through the patient's interior along the laparoscope's or instruments' axes to easily validate potential ports. Intraoperatively, surgeons need to update their surgical planning based on actual patient data after organ deformations mainly caused by application of carbon dioxide pneumoperitoneum. Therefore, preoperative imaging data can hardly be used. Instead, we propose to use an optically tracked mobile C-arm providing cone-beam CT imaging capability intraoperatively. After patient positioning, port placement, and carbon dioxide insufflation, the liver vessels are contrasted and a 3-D volume is reconstructed during patient exhalation. Without any further need for patient registration, the reconstructed volume can be directly augmented on the live laparoscope video, since prior calibration enables both the volume and the laparoscope to be positioned and oriented in the tracking coordinate frame. The augmentation provides the surgeon with advanced visual aid for the localization of veins, arteries, and bile ducts to be divided or sealed.     

Biomechanical modeling of the human head for physically based, nonrigid image registration

The accuracy of image-guided neurosurgery generally suffers from brain deformations due to intraoperative changes. These deformations cause significant changes of the anatomical geometry (organ shape and spatial interorgan relations), thus making intraoperative navigation based on preoperative images error prone. In order to improve the navigation accuracy, we developed a biomechanical model of the human head based on the finite element method, which can be employed for the correction of preoperative images to cope with the deformations occurring during surgical interventions. At the current stage of development, the two-dimensional (2-D) implementation of the model comprises two different materials, though the theory holds for the three-dimensional (3-D) case and is capable of dealing with an arbitrary number of different materials. For the correction of a preoperative image, a set of homologous landmarks must be specified which determine correspondences. These correspondences can be easily integrated into the model and are maintained throughout the computation of the deformation of the preoperative image. The necessary material parameter values have been determined through a comprehensive literature study. Our approach has been tested for the case of synthetic images and yields physically plausible deformation results. Additionally, we carried out registration experiments with a preoperative MR image of the human head and a corresponding postoperative image simulating an intraoperative image. We found that our approach yields good prediction results, even in the case when correspondences are given in a relatively small area of the image only.     

Multiple camera tracking of interacting and occluded human motion

We propose a distributed, real-time computing platform for tracking multiple interacting persons in motion. To combat the negative effects of occlusion and articulated motion we use a multiview implementation, where each view is first independently processed on a dedicated processor. This monocular processing uses a predictor-corrector filter to weigh reprojections of three-dimensional (3-D) position estimates, obtained by the central processor, against observations of measurable image motion. The corrected state vectors from each view provide input observations to a Bayesian belief network, in the central processor, with a dynamic, multidimensional topology that varies as a function of scene content and feature confidence. The Bayesian net fuses independent observations from multiple cameras by iteratively resolving independency relationships and confidence levels within the graph, thereby producing the most likely vector of 3-D state estimates given the available data. To maintain temporal continuity, we follow the network with a layer of Kalman filtering that updates the 3-D state estimates. We demonstrate the efficacy of the proposed system using a multiview sequence of several people in motion. Our experiments suggest that, when compared with data fusion based on averaging, the proposed technique yields a noticeable improvement in tracking accuracy     

基于AR技术的实时互动体验电商系统

电商已经不仅仅满足于线上的商品交易,越来越多地开始关注于线下用户体验的改善.本文以虚拟试鞋为切入口,借助于Kinect硬件设备和3d Max、unity3d软件平台,提出并搭建了基于AR增强现实技术的实时互动体验电商系统.本文对该系统的关键技术进行阐述,包括三维模型的跟踪定位、手势交互和RGB-D抠像.该系统综合应用三维场景虚拟化、三维互动识别以及增强现实融合等技术,硬件成本和算法复杂度低,操作简单,适用于新型电商利用AR技术对品牌进行线上展示和线下用户体验.     

Extraction of line properties based on direction fields

The authors present a new set of algorithms for segmenting lines, mainly blood vessels in X-ray images, and extracting properties such as their intensities, diameters, and center lines. The authors developed a tracking algorithm that checks rules taking the properties of vessels into account. The tools even detect veins, arteries, or catheters of two pixels in diameter and with poor contrast. Compared with other algorithms, such as the Canny line detector or anisotropic diffusion, the authors extract a smoother and connected vessel tree without artifacts in the image background. As the tools depend on common intermediate results, they are very fast when used together. The authors' results will support the 3-D reconstruction of the vessel tree from stereoscopic projections. Moreover, the authors make use of their line intensity measure for enhancing and improving the visibility of vessels in 3-D X-ray images. The processed images are intended to support radiologists in diagnosis, radiation therapy planning, and surgical planning. Radiologists verified the improved quality of the processed images and the enhanced visibility of relevant details, particularly fine blood vessels.     

Improved tracking of limb occlusion pressure for surgicaltourniquets

Constant-pressure tourniquets are widely used to occlude blood flow into a patient's limb to facilitate the performance of a wide variety of surgical procedures. Adaptive tourniquets that automatically adjust the cuff pressure to the minimum necessary for occlusion (limb occlusion pressure) as a function of the patient's changing systolic blood pressure are expected to reduce the incidence of tourniquet-related injuries. However, these devices have not been widely used, largely due to problems in tracking the systolic blood pressure safely, accurately, and reliably in clinical environments with noise present. Initial lab trials and clinical trials compared the performance in tracking limb occlusion pressure during varying noise conditions of a typical oscillometric blood pressure monitor with that of a prototype system. The prototype system functions by detecting noise and rapidly estimating limb occlusion pressure using only data uncorrupted by noise. Results showed that the prototype consistently estimated limb occlusion pressure more rapidly, more accurately, and more reliably than the oscillometric monitor in noisy conditions typical of surgical procedures. The results also indicate that the prototype is feasible for incorporation into an adaptive tourniquet     

An image-guided planning system for endosseous oral implants

A preoperative planning system for oral implant surgery was developed which takes as input computed tomographies (CT's) of the jaws. Two-dimensional (2-D) reslices of these axial CT slices orthogonal to a curve following the jaw arch are computed and shown together with three-dimensional (3-D) surface rendered models of the bone and computer-aided design (CAD)-like implant models. A technique is developed for scanning and visualizing an eventual existing removable prosthesis together with the bone structures. Evaluation of the planning done with the system shows a difference between 2-D and 3-D planning methods. Validation studies measure the benefits of the 3-D approach by comparing plans made in 2-D mode only with those further adjusted using the full 3-D visualization capabilities of the system. The benefits of a 3-D approach are then evident where a prosthesis is involved in the planning. For the majority of the patients, clinically important adjustments and optimizations to the 2-D plans are made once the 3-D visualization is enabled, effectively resulting in a better plan. The alterations are related to bone quality and quantity (p<0.05), biomechanics (p<0.005), and esthetics (p<0.005), and are so obvious that the 3-D plan stands out clearly (p<0.005). The improvements often avoid complications such as mandibular nerve damage, sinus perforations, fenestrations, or dehiscences     

基于InSAR的三维地形匹配导航技术的研究与实现

研究了一种以干涉合成孔径雷达(InSAR)信息为基础的三维地形匹配导航系统,该系统采用基于3-D Zernike矩的三维地形匹配算法,同时针对3-D Zernike矩在地形匹配中计算实时性差的问题进行了改进。为验证系统的有效性和算法性能,搭建了基于VC++和OpenSceneGraph的三维可视化软件仿真平台。仿真结果表明,基于3-D Zernike矩的三维地形匹配算法定位精确度高,对地形的适应能力强,算法的实时性问题得到了良好解决,系统具有较高的工程实用价值。