3D reconstruction of a femoral shape using a parametric model and two 2D fluoroscopic images

In medical diagnostic imaging, the X-ray CT scanner and the MRI system have been widely used to examine 3D shapes and internal structures of living organisms and bones. However, these apparatuses are generally large and very expensive. Since an appointment is also required before examination, these systems are not suitable for urgent fracture diagnosis in emergency treatment. However, X-ray/fluoroscopy has been widely used as traditional medical diagnosis. Therefore, the realization of the reconstruction of precise 3D shapes of living organisms or bones from a few conventional 2D fluoroscopic images might be very useful in practice, in terms of cost, labor, and radiation exposure. The present paper proposes a method by which to estimate a patient-specific 3D shape of a femur from only two fluoroscopic images using a parametric femoral model. First, we develop a parametric femoral model by the statistical analysis of 3D femoral shapes created from CT images of 56 patients. Then, the position and shape parameters of the parametric model are estimated from two 2D fluoroscopic images using a distance map constructed by the Level Set Method. Experiments using synthesized images, fluoroscopic images of a phantom femur, and in vivo images for hip prosthesis patients are successfully carried out, and it is verified that the proposed system has practical applications.     

基于虚拟现实的计算机辅助立体定向神经外科手术系统

介绍了一个计算机辅助立体定向神经外科手术系统,该系统基于实时可视化绘制、机器人和虚拟现实技术,辅助医生完成立体定向神经外科手术,系统首先利用患者脑部的扫描数据重构并绘制出患者脑部的三维组织结构,为医生调整和确定手术规划提供参照。系统采用了标记点的校准方法,在手术前和手术中分别进行脑部模型和患者的坐标校准。通过机械臂的导航,使机械壁达到了手术规划规定的位置和姿态,医生利用安装在机械臂上的手术器械完成     

Real‐time Simulation of Catheterization in Endovascular Surgeries

This paper proposes an efficient and stable numerical method for modeling catheterization during endovascular surgeries. The guidewire‐catheter combination is treated as an elastic rod, which has very large resistance against twisting about its medial axis. A torsion free assumption is made, and the physical behavior of the rod is predominately governed by stretching and bending energies. This simplification greatly reduces the computational complexity and makes the model more stable, while the simulation results are still realistic enough for its application in endovascular surgeries. A contact handling algorithm that directly makes use of the volume data of the relevant tissues is proposed to simulate the interaction between the guidewire‐catheter combination and the aortic wall. During each simulation step, the penetration depth of each vertex in contact with the aortic wall is calculated using moving least squares surfaces, and the contact is then resolved in a position‐based manner. A comprehensive quantitative evaluation of the rod model is performed to validate its accuracy. Finally, the proposed approach is applied in a prototype system for simulation of endovascular aneurysm repair surgeries. Its efficiency and effectiveness are demonstrated in a real‐time interactive catheterization simulation. Copyright © 2016 John Wiley & Sons, Ltd.     

Impact of aortic repair based on flow field computer simulation within the thoracic aorta

Purpose of this computational study is to examine the hemodynamic parameters of velocity fields and shear stress in the thoracic aorta with and without aneurysm, based on an individual patient case and virtual surgical intervention. These two cases, case I (with aneurysm) and II (without aneurysm), are analyzed by computational fluid dynamics. The 3D Navier-Stokes equations and the continuity equation are solved with an unsteady stabilized finite element method. The vascular geometries are reconstructed based on computed tomography angiography images to generate a patient-specific 3D finite element mesh. The input data for the flow waveforms are derived from MR phase contrast flow measurements of a patient before surgical intervention.The computed results show velocity profiles skewed towards the inner aortic wall for both cases in the ascending aorta and in the aortic arch, while in the descending aorta these velocity profiles are skewed towards the outer aortic wall. Computed streamlines indicate that flow separation occurs at the proximal edge of the aneurysm, i.e. computed flow enters the aneurysm in the distal region, and that there is essentially a single, slowly rotating, vortex within the aneurysm during most of the systole.In summary, after virtual surgical intervention in case II higher shear stress distribution along the descending aorta could be found, which may produce more healthy reactions in the endothelium and benefit of vascular reconstruction of an aortic aneurysm at this particular location.     

A geometric approach to the modeling of the catheter-heart interaction for VR simulation of intra-cardiac intervention

Cardiac intervention is a minimally invasive diagnostic and therapeutic procedure used to treat cardiac diseases. The mapping of heart geometry with minimal visual assistance presents a technical challenge for interventional cardiologists attempting catheter navigation. This paper presents a geometric approach to modeling the catheter-heart interaction for VR simulations of catheter navigation within a heart chamber. Three types of modeling are used to model the interaction between the catheter and the heart wall: non-slip, pseudo-slip and slip modeling. A two-step shape memory process that minimizes the bending of and strain on the catheter is designed for catheter deformation for non-slip or pseudo-slip contact, and a progressive group linkage bending process that constrains the catheter curvature and position within the volume enclosure is designed for catheter deformation for slip contact. The proposed model is consistent with the observations made during the experiment. The model is able to deform the catheter in any free-state shape within the volume enclosure and is independent of local motion increment. Thus, it presents advantages in terms of complexity and real-time requirements.     

Tree Height and Diameter Extraction with 3D Reconstruction in a Forest based on TLS

In view of the low accuracy of Tree Height(TH) and Diameter at Breast Height(DBH) estimation,as well as the difficulty of individual tree modeling in dense forest,a method to extract forest structure parameters(TH and DBH) and reconstruct a Three-Dimensional(3D) model of forest in subtropical environment based on TLS point cloud data is proposed.The first step is to apply a multi-scale method to extract the ground points for the generation of Digital Elevation Model(DEM).Secondly,using similarity of principal direction between neighboring points and distribution density of points,trunk and other plant organs are separated.Next the trunk points are processed to automatically estimate the tree position and DBH by iterative least squares cylinder fitting;the tree height is automatically estimated by using the octree segmentation.Finally,by combining with the technology of individual tree modeling,a plot-scale 3D forest scene has been reconstructed by planting individual tree model on the terrain model iteratively.The results showed that the correlation coefficient of DBH is R²=0.996,and the average relative error was 2.09%,RMSE was 0.66 cm;the correlation coefficient of tree height is R²=0.972,and the average relative error was 2.16% with RMSE of 0.92 m.The plot-scale reconstructed 3D model of the forest can express the true shape of forest.     

Laser-machined shape memory alloy sensors for position feedback in active catheters

Catheter-based interventions are a form of minimally invasive surgery that can decrease hospitalization time and greatly lower patient morbidity compared to traditional methods. However, percutaneous catheter procedures are hindered by a lack of precise tip manipulation when actuation forces are transmitted over the length of the catheter. Active catheters with local shape memory alloy (SMA) actuation can potentially provide the desired manipulation of a catheter tip, but hysteresis makes it difficult to control the actuators. A method to integrate small-volume, compliant sensors on an active catheter to provide position feedback for control would greatly improve the viability of SMA-based active catheters. In this work, we describe the design, fabrication, and performance of resistance-based position sensors that are laser-machined from superelastic SMA tubing. Combining simple material models and rapid prototyping, we can develop sensors of appropriate stiffness and sensitivity with simple modifications in sensor geometry. The sensors exhibit excellent linearity over the operating range and are designed to be easily integrated onto an active catheter substrate.     

微创血管介入手术机器人的主从交互控制方法与实现

微创血管介入手术是治疗冠心病的重要治疗手段, 手术中要求对导管、导丝等介入器械高精度递送.得益于机器人技术的高精度、可远程操作等特点, 血管介入手术机器人的研制受到了极大关注.在微创血管介入手术中, 按导管或导丝远端所处血管部位, 将介入器械递送过程分为三个阶段: 1) 主动脉阶段:导丝或导管远端位于主动脉, 需快速前送, 以减少X射线和造影剂的使用; 2) 冠脉入口阶段:导丝或导管远端进入冠脉, 此时需选择相应的病变冠脉分支; 3) 冠脉病变阶段:导丝或导管远端位于狭窄病变部位, 需要高精度操作才能使导丝或导管穿过狭窄病变.针对器械递送的不同阶段, 提出具有运动缩放的主从控制方法, 通过改变血管介入手术机器人主端和从端之间的运动缩放关系, 实现机器人从端对主端操作的放大、缩小或等比例复现.通过在微创血管介入手术机器人平台实验, 验证了机器人从端对主端操作缩放的可行性和有效性.通过操作时间和操作精度对比分析得到:在缩放因子为4时操作时间减少39.9%;在缩放因子为1/4时, 平移和旋转操作精度分别提高72.9%和77.1%.     

面向血液循环系统仿真的全身血管重建

血管的点云数据表示在医疗中有着重要的作用,可以帮助医护人员直观地了解血管的几何信息.对于医疗辅助技术、放射学模拟等应用中,除了对局部的血管系统几何信息进行可视之外,也需要对全身血管进行准确的仿真建模,从而对整体血管系统的拓扑及几何信息都需要进行系统性的重建.传统骨架提取技术无法保证血管模型正确的连接拓扑,提出了一种基于点云数据的交互式全身血管模型重建方法,通过对血管数据分段和拟合,并分析各段血管端点连接情况,重建了一种带有血管截面半径信息的全身血管一维骨架模型,且该模型能直接用于血流血压等仿真.与已有方法相比,其优势在于能应用于大规模的复杂的全身血管点云数据,且重建的模型可以直接用于仿真.BodyParts3D数据集下实验结果表明,与已有方法相比,文中方法重建的全身血管一维骨架模型具有准确的拓扑连接,能够生成更好的仿真效果.     

Development of rotational digital angiography system--clinical value in acute pulmonary thromboembolism

A rotational digital angiography system was newly developed by authors. During the rotation, a pulse exposure is done at every 1.25 degrees by computer control, so that 288 different projectional images can be acquired following a single injection of contrast medium. Because rotational image data can be easily reconstructed to 3-D images, more useful diagnostic informations are obtained. Rotational digital angiography was performed for 15 patients with acute pulmonary thromboembolism, and massive thromboemboli were revealed in all patients. The diagnostic usefulness of this new system has also proven to be improved in the interventional procedures. At the appropriate angle, the thrombosed vessels were clearly distinguished. Thus, as the tip of the catheter was advanced to the target site, the thrombosed lesion could be exclusively treated by interventional techniques. The device has, therefore, been found to be of great value in the diagnosis and intervention of acute pulmonary thromboembolism.     

基于立体视觉的接触式三维测量系统

传统的三维接触式测量方法存在着速度慢、测量范围受限等缺点,而纯粹的非接触式测量方法则存在着特征边缘无法获取的问题。结合两种测量方法,设计了一种新的三维测量系统,该系统采用立体视觉技术对接触式测头的空间位置和姿态进行定位,进而间接计算接触式探针针尖位置来完成空间点的三维坐标测量。实验结果表明:系统测量精度优于0.2 mm,能够应用于工业现场进行复杂工件的典型几何特征检测和模型重构。     

基于描绘单幅图像的三维树木交互建模系统

为了提高树木建模的真实感与可交互性,提出了一种基于单幅树木图像或直接手绘的交互式植物建模系统。系统根据植物形态学规律构建了标准三维树木的模板。通过描绘图像中树的主要枝干,结合叶序周规律,基于三维模板树将其从二维图像变换到三维模型,并通过弯曲、增加和删除枝干以及添加树叶等交互式操作生成和修改三维树木模型。实验结果表明,该系统能便捷快速地生成真实感较强的三维树木。     

The structural and radiative consistency of three-dimensional tree reconstructions from terrestrial lidar

A novel methodology is proposed to reconstruct 3D tree architectures from terrestrial LiDAR (TLiDAR) scans. The methodology is robust and relatively insensitive to wind- and occlusion-induced artefacts in the 3D TLiDAR point clouds. A quantitative evaluation of structural attributes, like the vertical foliage and wood area profiles, as well as the shoot orientation distribution, was performed. Due to the difficulties of acquiring reliable and accurate estimates of these parameters in the field, an original evaluation approach was chosen that reproduces the TLiDAR scanning and subsequent tree reconstruction process in a virtual environment. In a second step the reconstructed tree models were ingested in a validated 3D radiative transfer model to simulate both their reflectance signatures (observable by space borne instruments) and directional transmission properties (measurable during field campaigns) under various spectral, illumination and tree density scenarios. The results of these evaluations confirm the appropriateness of the proposed tree reconstruction model for the generation of structurally and radiatively faithful copies of existing plant and canopy architectures.     

3D stereo interactive medical visualization

Our interactive, 3D stereo display helps guide clinicians during endovascular procedures, such as intraoperative needle insertion and stent placement relative to the target organs. We describe a new method of guiding endovascular procedures using interactive 3D stereo visualizations. We use as an example the transjugular intrahepatic portosystemic shunt (TIPS) procedure. Our goal is to increase the speed and safety of endovascular procedures by providing the interventionalist with 3D information as the operation proceeds. Our goal is to provide 3D image guidance of the TIPS procedure so that the interventionalist can readily adjust the needle position and trajectory to reach the target on the first pass. We propose a 3D stereo display of the interventionalist's needle and target vessels. We also add interactivity via head tracking so that the interventionalist gains a better 3D sense of the relationship between the target vessels and the needle during needle advancement.     

三维环境下的自由曲面误差评定系统研究

为了提升误差评定系统的效果,针对三坐标测量机的测量方式,基于OpenGL开发了三维环境下的自由曲面误差评定系统。根据三坐标测量机的特点进行了自由曲面测量点的三维球测头半径补偿,采用双三次B样条进行曲面的反求。针对点到自由曲面距离的计算问题,依据点与面片的匹配关系在叠代判断中加入参数越界的判断条件以提高效率。评定结果采用报表与三维显示相配合的方式,使结果更直观、方便。采用三维图形开发技术构建三维环境的误差评定系统,提升了逆向工程配套软件系统的灵活性与直观性,满足了用户需求。     

下颌骨骨折虚拟手术培训系统研究

针对下颌骨骨折手术操作技能要求高的特点,使用Unity3D和HTC VIVE进行用于培训和术前模拟的虚拟手术系统的开发。将虚拟手术系统分为三维模型模块、光照系统模块、交互系统模块和手术室瞬间移动模块,对下颌骨骨折手术的场景、交互和手术过程进行模拟。结果表明此虚拟手术系统具有良好的真实感、沉浸感和交互性,能有效引导操作者完成手术流程,达成进行手术训练、模拟的目的。     

Design and performance evaluation of a novel robotic catheter system for vascular interventional surgery

Vascular interventional surgery (VIS) is an effective treatment method for vascular diseases. However, there are many problems in traditional VIS, such as surgeons are radiated by X-ray, the lack of well skilled surgeons, the security of the surgery will be reduced due to the Surgeons’ fatigue, high risk of the surgery. To solve these problems, a robotic catheter system is needed to protect the surgeons and enhance the safety of the surgery. In this paper, a novel robotic catheter system with master–slave structure for VIS has been developed. This system is designed with the consideration of the operation method in traditional VIS, which allows the surgeon to operate a real catheter on the master side, then the surgeon make full use of the natural catheter manipulation experience and skills obtained in conventional catheter operation. The salve manipulator operates the catheter insert into the blood vessel with following the operation of the surgeon, and the operating force of the salve manipulator is detected. On the master side, a novel damper-based magnetorheological (MR) fluid is designed to realize the force feedback, which is also used to reappear the operation force from the salve manipulator. The damper connected directly with real catheter is a piston structure using the MR fluid to realize the force feedback. It can transmit the feedback force to surgeon’s hand through the operating catheter connected with damper, which seems that the surgeon operates the catheter beside the patient. The operating transparency of the developed system has been enhanced. The mechanism of the developed system has been introduced in detail. Performance evaluation experiments for the developed robotic catheter system have been done. The experimental results indicated that the developed robotic catheter system is fit for VIS.     

心内膜几何模型的计算机三维重建技术

心内膜标测系统中,三维心内膜几何模型的构建是一个重大进步,在手术中导航导管起着关键的作用。本文介绍了一种利用凸包算法,从心腔内导管电极的位置信息中提取建模数据的方法。并用Matlab仿真,证明该法可以筛除心腔内的数据点,而提取心内膜表面上的点,构建心腔舒张期的三维心内膜模型。     

Model free head pose estimation using stereovision

In this paper we present a stereovision based model free 3D head pose (orientation and position) estimation system suitable for human–machine interface applications. The system works by obtaining a ‘face plane’ from the 3D reconstructed face data, which is then used for head pose estimation. The key novelty in this work is the utilization of the face plane together with the eye locations on the reconstructed face data to obtain a robust head pose estimate. This approach leads to a model and initialization free head pose estimation system; therefore it is suitable for natural human–machine interfaces. In order to quantitatively asses the accuracy of the system for such applications, several evaluation experiments were conducted using a commercial motion capture system. The evaluation results indicate that this system can be used in human–computer and human–robot applications.     

口腔颌面疾病辅助诊断系统的设计与实现

为给口腔颌面外科的临床诊断提供帮助,并对TMJ进行虚拟手术操作,设计并实现一个口腔颌面疾病医学辅助诊断系统(OMD- MADS)。系统采用AddIn树设计方法,包括一个医学图像三维重建系统和一个口腔颌面疾病本体。介绍OMD-MADS的功能和设计过程。根据输入的CT图像重建下颌骨的三维模型。该系统可实现疾病信息查询和模型操作,用作医患交流平台和教学工具。