MRI-Compatible Pneumatic Robot for Transperineal Prostate Needle Placement

Magnetic resonance imaging (MRI) can provide high-quality 3-D visualization of prostate and surrounding tissue, thus granting potential to be a superior medical imaging modality for guiding and monitoring prostatic interventions. However, the benefits cannot be readily harnessed for interventional procedures due to difficulties that surround the use of high-field (1.5T or greater) MRI. The inability to use conventional mechatronics and the confined physical space makes it extremely challenging to access the patient. We have designed a robotic assistant system that overcomes these difficulties and promises safe and reliable intraprostatic needle placement inside closed high-field MRI scanners. MRI compatibility of the robot has been evaluated under 3T MRI using standard prostate imaging sequences and average SNR loss is limited to 5%. Needle alignment accuracy of the robot under servo pneumatic control is better than 0.94 mm rms per axis. The complete system workflow has been evaluated in phantom studies with accurate visualization and targeting of five out of five 1 cm targets. The paper explains the robot mechanism and controller design, the system integration, and presents results of preliminary evaluation of the system.     

CT/MR-compatible physical human-robotized needle interactions: From modeling to percutaneous steering

In recent years a number of robotic steering systems have been proposed that are geared towards improving interventional radiology procedures such as tumor ablation and biopsy. These solutions have introduced new safety challenges in the physical human–robot interaction domain. This study presents a new 3D robotized needle steering algorithm compatible with CT and MR-imaging guidance. The steering algorithm is featured with an adaptive self-correction mechanism that works as a failure contingency tool that could be adapted online at each insertion step. The developed pHRI solution was designed to be compatible to ferro-magnetic issues and a reduced workspace inside the scanner bore. As far as we know, this is the first approach designed to steer rigid needles free of force sensors and which meets the challenges that prevail in our context. Our proposed approach helps overcome safety issues regarding the physical interaction between robotized needles and patients. Validation testing highlighted the feasibility of the new needle steering algorithm, while its accuracy revealed the potential of the approach under the proposed scope of application.     

Using English as a High-Level Robot Command Language

To facilitate expedient communication with robots, a very high-level hierarchical robot command language (Hirob) has been designed and implemented. Hirob uses the full and comprehensive syntax of the English imperative, allowing users to control a robot without the need of learning an esoteric programming language. A Parser/Scanner/Recognizer (PSR) performs a lexical analysis of a Hirob command stream, and identifies which portions of the command stream already exist as fully defined procedures in the files of the Procedure Management System (PMS). Those portions which do not exist must be defined using either existing Hirob procedures (English phrases), or by using the primitive commands of the low-level robot command language (Lorob). This process is fully recursive, so that Hirob procedures may consist of defined or undefined Hirob procedures, as well as Lorob commands, with the understanding that a high-level command cannot be executed until all of its hierarchical subcommands have been fully defined. A user-friendly editor has been incorporated into the PMS to allow convenient creation, modification, and testing of Hirob commands.     

基于webots的机器人避障及物体识别仿真

本文运用webots对机器人在家庭环境下物体识别可能遇到的问题进行了模拟仿真,验证其可行性.主要完成了对家庭环境和机器人模型的搭建及控制程序的编写并以此实现机器人避障和物体识别.仿真结果表明,此方法可行.为今后的算法改进奠定了基础.     

Methods for providing probe position and temperature information onMR images during interventional procedures

Interventional magnetic resonance imaging (MRI) can be defined as the use of MR images for guiding and monitoring interventional procedures (e.g., biopsy, drainage) or minimally invasive therapy (e.g., thermal ablation). This work describes the development of a prototype graphical user interface and the appropriate software methods to accurately overlay a representation of a rigid interventional device [e.g., biopsy needle, radio-frequency (RF) probe] onto an MR image given only the probe's spatial position and orientation as determined from a three-dimensional (3-D) localizer used for interactive scan plane definition. This permits 1) “virtual tip tracking”, where the probe tip location is displayed on the image without the use of separate receiver coils or a “road map” image data set, and, 2) “extending” the probe to predict its path if it were directly moved forward toward the target tissue. Further, this paper describes the design and implementation of a method to facilitate the monitoring of thermal ablation procedures by displaying and overlaying temperature maps from temperature sensitive MR acquisitions. These methods provide rapid graphical updates of probe position and temperature changes to aid the physician during the actual interventional MRI procedures without altering the usual operation of the MR imager     

Accurate localization of optic radiation during neurosurgery in an interventional MRI suite

Accurate localization of the optic radiation is key to improving the surgical outcome for patients undergoing anterior temporal lobe resection for the treatment of refractory focal epilepsy. Current commercial interventional magnetic resonance imaging (MRI) scanners are capable of performing anatomical and diffusion weighted imaging and are used for guidance during various neurosurgical procedures. We present an interventional imaging workflow that can accurately localize the optic radiation during surgery. The workflow is driven by a near real-time multichannel nonrigid image registration algorithm that uses both anatomical and fractional anisotropy pre- and intra-operative images. The proposed workflow is implemented on graphical processing units and we perform a warping of the pre-operatively parcellated optic radiation to the intra-operative space in under 3 min making the proposed algorithm suitable for use under the stringent time constraints of neurosurgical procedures. The method was validated using both a numerical phantom and clinical data using pre- and post-operative images from patients who had undergone surgery for treatment of refractory focal epilepsy and shows strong correlation between the observed post-operative visual field deficit and the predicted damage to the optic radiation. We also validate the algorithm using interventional MRI datasets from a small cohort of patients. This work could be of significant utility in image guided interventions and facilitate effective surgical treatments.     

Collaborative work during interventional radiological procedures based on a multicast satellite-terrestrial network.

Collaboration is a key requirement in several contemporary interventional radiology procedures (IRPs). This work proposes a multicast hybrid satellite system capable of supporting advanced IRP collaboration, and evaluates its feasibility and applicability. Following a detailed IRP requirements study, we have developed a system which supports IRP collaboration through the employment of a hybrid satellite-terrestrial network, a prototype multicast version of wavelet based interactive communication system (WinVicos) application, and a partition aggregation and conditional coding (PACC) wavelet codec. A semistructured questionnaire was also used to receive evaluative feedback from collaborating participants. The departments of interventional radiology of University Hospital of Patras, Greece and of Charite Hospital of Berlin, Germany have been connected on the system. Eight interventional radiologists and a vascular surgeon participated periodically in three satellite-terrestrial "fully collaborative" IRPs (average time 90 min) of high complexity and in four terrestrial educational sessions with great success, evidenced by considerable improving the IRP outcomes (clinical and educational). In case of high complexity, where the simultaneous presence of remote interventional expert and/or surgeon is required, advanced collaboration among staff of geographically dispersed international centers is feasible via integration of existing networking and other technologies.     

Design, Performance, and Applications of a Hybrid X-Ray/MR System for Interventional Guidance

Image-guided minimally invasive procedures have made a substantial impact in improving patient management, reducing the cost, morbidity, and mortality of treatments and making therapies available to patients who would otherwise have no option. X-ray fluoroscopy and magnetic resonance imaging (MRI) are two powerful tools for guiding interventional procedures but with very different strengths and weaknesses. X-ray fluoroscopy offers very high spatial and temporal resolution and is excellent for guiding and deploying devices. MRI offers tomographic imaging with complete freedom of plane orientation, outstanding soft tissue discrimination, and the ability to portray physiological responses during treatment. We have shown that it is feasible to fully integrate an X-ray fluoroscopy system into the bore of an interventional MR scanner to provide a single congruent field of view, with integration requiring minor modifications to the flat-panel digital detector, and using a static-anode X-ray tube. Given the limited availability of the MR scanner platform (0.5T GE Signa SP magnet), and the X-ray fluence limitations of the static-anode X-ray tube, we are now investigating the technology developments required to place a rotating-anode digital flat-panel X-ray system immediately adjacent to a closed-bore MRI system. These types of hybrid systems could have enormous impact in the diagnosis and treatment of oncologic, cardiovascular, and other disorders.     

基于模糊控制的机器人寻线控制系统改进设计

针对移动机器人寻线控制的传统寻线控制系统使机器人在导引线上摇摆前进的问题,引入模糊控制的思想,并在此基础上设计一种新型基于多传感器信息融合的寻线控制系统,并根据反模糊化结果和实验修正给出核心程序。实际运行显示此改进设计很大程度改变机器人寻线中的摇摆现象,实现平稳的寻线控制。此设计思想对各种条件下的移动机器人寻线控制具有一定参考价值。     

LPR: A CT and MR-Compatible Puncture Robot to Enhance Accuracy and Safety of Image-Guided Interventions

Image-guided percutaneous interventions are common procedures used for diagnosis or therapeutic purposes. The clinical demand for such interventions is growing since they are minimally invasive. To increase the quality of the operations and provide optimal accuracy and safety to patients, puncture robots may be very helpful. This paper presents a new robotic architecture designed to perform abdominal and thoracic punctures under computer tomography (CT) or MRI guidance. Innovations concerning the robotic architecture, materials, and energy sources are described. Segmentation and registration algorithms have been developed to localize the robot on images coming from CT or MRI devices, and a specific control loop is used to verify the movements and the positioning of the robot. The results of the initial experiments made under CT and MRI environments are presented.     

An MRI-compatible endonasal surgical robotic system: Kinematic analysis and performance evaluation

Neurosurgical interventions are often complicated and require procedure-specific solutions for a better outcome. A pituitary tumor is one of the common brain tumors resected by trans-sphenoidal surgery. Magnetic resonance imaging (MRI) provides better vision when compared to other imaging modalities. Simultaneous resection and imaging of pituitary tumors under MRI can improve the surgical outcome. Herein, we propose the first MRI-compatible robotic system for pituitary tumor removal via trans-sphenoidal/endonasal access. The presented system follows the current gold standard procedure of pituitary tumor resection and integrates it with a commercial MR scanner to provide a widely applicable system. The robotic system is the procedure-, anatomy-, and geometry-specific with 6-degree-of-freedom actuated by a bed-type actuation platform in the MRI room. A K-means clustering algorithm detects the tumor and develops and updates the brain model periodically during MR-guided interventions. The robot has procedure-specific stiffness changing capability with a unique stiffness-dependent kinematic model. The workspace subtended by the robotic system in all stiffness cases satisfies the workspace required for surgical procedures. The accuracy and repeatability of the robot are also in a desirable range. The procedure and patient-specific robot design are evaluated by in-vivo experiments in the live porcine under MRI. This work is a step toward a dual-arm surgical system for pituitary tumor removal under MRI guidance and experimental results validate the proposed solution and supplement further development to achieve a clinically applicable system.     

Vielgliedrige elastische Roboter

A multi-link elastic robot system is discussed which consists of a number of subsystems including motor, gear and elastic beam. These undergo rapid rigid body motion with superimposed small elastic deformations. The latter are taken into account with a direct Ritz approach. Evaluation of the projection equation along with the use of nonholonomic (intermediate) variables leads to simple equation structures. One obtains, moreover, a very efficient recursion procedure for the numerical treatment which, using common procedures (inversion of the total mass matrix), might be problematic.     

A Framework for Testing of Wireless Underwater Robots

Underwater applications of wireless robots are foreseen to hold a market potential. The standardization process will drive the development of the necessary technology so that devices can work cooperatively. Specific testing procedures have to be developed in order to verify that a device meets requirements. In this paper, a general framework for testing of underwater wireless robot communications is described. The methodology for conformance and interoperability tests is addressed by considering wireless robots as terminals in an underwater acoustic network.     

Nonrigid 2D/3D registration of coronary artery models with live fluoroscopy for guidance of cardiac interventions

A 2D/3D nonrigid registration method is proposed that brings a 3D centerline model of the coronary arteries into correspondence with bi-plane fluoroscopic angiograms. The registered model is overlaid on top of interventional angiograms to provide surgical assistance during image-guided chronic total occlusion procedures, thereby reducing the uncertainty inherent in 2D interventional images. The proposed methodology is divided into two parts: global structural alignment and local nonrigid registration. In both cases, vessel centerlines are automatically extracted from the 2D fluoroscopic images, and serve as the basis for the alignment and registration algorithms. In the first part, an energy minimization method is used to estimate a global affine transformation that aligns the centerline with the angiograms. The performance of nine general purpose optimizers has been assessed for this problem, and detailed results are presented. In the second part, a fully nonrigid registration method is proposed and used to compensate for any local shape discrepancy. This method is based on a variational framework, and uses a simultaneous matching and reconstruction process to compute a nonrigid registration. With a typical run time of less than 3 s, the algorithms are fast enough for interactive applications. Experiments on five different subjects are presented and show promising results.     

A virtual reality simulator for remote interventional radiology: concept and prototype design

We present a virtual reality simulator to realize interventional radiology (IR) procedures remotely. The simulator contains two subsystems: one at the local site and the other at the remote site. At the local site, the interventional radiologist interacts with a three-dimensional (3-D) vascular model extracted from the patient's data and inserts IR devices through the Motion Tracking Box (MTB), which converts physical motion (translation and rotation) of IR devices into digital signal. This signal is transferred to the Actuator Box (AB) at the remote site that drives the IR devices in the patient. The status of the IR devices is subsequently fed back to the local site and displayed on the vascular model. To prove the concept, the prototype developed employs a physical angiography phantom (mimicking the patient) and its corresponding 3-D digital model. A magnetic tracking system provides information about positioning of the IR devices in the phantom. The initial results are encouraging. The AB controlled remotely drives IR devices with resolution of 0.00288 mm/step in translation and 0.079 deg/step in rotation.     

Decoupled control of robot movement

Recently, methods have been proposed for the simultaneous decoupling of the controls of nonlinear dynamical systems and for the assignment of poles in the resulting decoupled linear systems. These methods have been used to obtain decoupled controls for the equations of motion of industrial robot arms and their performance has been gauged by simulation. It is shown here that such decoupling procedures do not guarantee stable controls and that their use, where the mathematical models of the controlled systems may be subject to uncertainty, should be attempted with caution.     

Kinematic and deformation analysis of 4-D coronary arterial trees reconstructed from cine angiograms

In the cardiovascular arena, percutaneous catheter-based interventional (i.e., therapeutic) procedures include a variety of coronary and other vascular system interventions. These procedures use two-dimensional (2-D) X-ray-based imaging as the sole or the major imaging modality for procedure guidance and quantification of key parameters. Coronary vascular curvilinearity is one key parameter that requires a four-dimensional (4-D) format, i.e., three-dimensional (3-D) anatomical representation that changes during the cardiac cycle. A new method has been developed for reconstruction and analysis of these patient-specific 4-D datasets utilizing routine cine angiograms. The proposed method consists of three major processes: 1) reconstruction of moving coronary arterial tree throughout the cardiac cycle; 2) establishment of temporal correspondence with smoothness constraints; and 3) kinematic and deformation analysis of the reconstructed 3-D moving coronary arterial trees throughout the cardiac cycle.     

Emulation of robots interacting with environment

In this paper, we present a methodology for emulation of a target robot operating in a complex environment by using an actual robot. The emulation scheme aims to replicate the dynamical behavior of the target robot interacting with an environment, without dealing with a complex calculation of the contact dynamics. This method forms a basis for the task verification of a flexible space robot. The actual emulating robot is structurally rigid, while the target robot can represent any class of robots, e.g., flexible, redundant, or space robots. Although the emulating robot is not dynamically equivalent to the target robot, the dynamical similarity can be achieved by using a control law developed herein. The effect of disturbances and actuator dynamics on the fidelity and the contact stability of the robot emulation is thoroughly analyzed. The concept of robot emulation is demonstrated by performing a number of preliminary experiments for emulation of flexible-joint robots.     

The imperative for medical simulation

The practice of medicine has, for millennia, relied upon a master-apprentice system of learning, with patients providing the necessary anatomy from which one learns how to perform surgery and other procedures. The advent of high-power computing and real-time graphics representations allows medicine to advance beyond this traditional methods of teaching and to begin to educate physicians without putting patients at risk. With innovative haptics interface devices, computer-based training will enable novice physicians to learn procedures that have been developed since their training was completed. Specialty boards and credentialing organizations will, for the first, time, have metrics upon which to base the decisions regarding who is qualified to practice medicine, and both sides of the learning curve, the acquisition of skills and their deterioration, will be discovered. The paper presents the concepts, challenges, and visions of the authors, both of whom have been actively developing simulation for the specialty of interventional radiology. It includes expectations for the future of simulation in other procedural specialties     

Towards cardiac C-arm computed tomography

Cardiac interventional procedures would benefit tremendously from sophisticated three-dimensional image guidance. Such procedures are typically performed with C-arm angiography systems, and tomographic imaging is currently available only by using preprocedural computed tomography (CT) or magnetic resonance imaging (MRI) scans. Recent developments in C-arm CT (Angiographic CT) allow three-dimensional (3-D) imaging of low contrast details with angiography imaging systems for noncardiac applications. We propose a new approach for cardiac imaging that takes advantage of this improved contrast resolution and is based on intravenous contrast injection. The method is an analogue to multisegment reconstruction in cardiac CT adapted to the much slower rotational speed of C-arm CT. Motion of the heart is considered in the reconstruction process by retrospective electrocardiogram (ECG)-gating, using only projections acquired at a similar heart phase. A series of N almost identical rotational acquisitions is performed at different heart phases to obtain a complete data set at a minimum temporal resolution of 1/N of the heart cycle time. First results in simulation, using an experimental phantom, and in preclinical in vivo studies showed that excellent image quality can be achieved.