Research on real-time detection system of catheter delivering force in vascular interventional robots / 生物医学工程学杂志

In existing vascular interventional surgical robots, it is difficult to accurately detect the delivery force of the catheter/guidewire at the slave side. Aiming to solve this problem, a real-time force detection system was designed for vascular interventional surgical (VIS) robots based on catheter push force. Firstly, the transfer process of catheter operating forces in the slave end of the interventional robot was analyzed and modeled, and the design principle of the catheter operating force detection system was obtained. Secondly, based on the principle of stress and strain, a torque sensor was designed and integrated into the internal transmission shaft of the slave end of the interventional robot, and a data acquisition and processing system was established. Thirdly, an ATI high-precision torque sensor was used to build the experimental platform, and the designed sensor was tested and calibrated. Finally, sensor test experiments under ideal static/dynamic conditions and simulated catheter delivery tests based on actual human computed tomography (CT) data and vascular model were carried out. The results showed that the average relative detection error of the designed sensor system was 1.26% under ideal static conditions and 1.38% under ideal dynamic stability conditions. The system can detect on-line catheter operation force at high precision, which is of great significance towards improving patient safety in interventional robotic surgery.

Transmission Model of Tendon-Sheath System for Endoscopic Flexible Instrument and Experimental Study / 医用生物力学

Objective To establish the pushing transmission model of tendon-sheath system (TSS) for endoscopic flexible instrument, and study the key influencing factors of transmission efficiency. Methods The force and displacement transmission models of TSS in pushing configuration were built and simulated. The tendon-sheath transmission testing platform was designed to validate the model. The influencing factors, such as transmission velocity, tendon-sheath diameter ratio, curvature radius, were explored using this setup. Results There were obvious nonlinear phenomenon in force and displacement transmission. The model simulation results accorded quite well with the experiment results. Transmission velocity, tendon-sheath diameter ratio, curvature radius all had great effects on pushing force transmission of endoscopic flexible instrument, while they had a smaller effect on displacement transmission. Conclusions The proposed model can be used for calculating pushing force transmission of tendon-sheath system for endoscopic flexible instrument, so as to provide the doctors with force feedback at the tip of the end effector, and ensure the safe operation and improve the surgical effects. For better design and control of endoscopic flexible instrument, the transmission velocity, tendon-sheath diameter ratio, curvature radius must be comprehensively considered.

A New Micro-traumatic Laparoscopic Surgery Robot System / 中国医疗器械杂志

At present, there still exist some limitations in the laparoscopic surgery robot represented by da Vinci surgical robot, such as the lack of force feedback function. Doctor can not feel the force feedback while operating. In this paper, a new minimally invasive laparoscopic surgery robot system is designed. Based on the master side surgeon's console, stereo vision subsystem and the slave side surgical cart, the multi-dimensional instrument force feedback technology and force feedback based safety protection strategy are introduced. The design realizes the force sensing function of full state operation. Besides, a number of different live pig experiments are carried out. The amount of bleeding in these experiments is relatively small compared with the data of the same kind of surgical robots, which effectively validates the force feedback and surgical safety protection strategies of the new robot system.

Testing and research of drilling feed force on fresh porcine femur / 医用生物力学

Objective To record the drilling feed force on different layers of fresh porcine femur, so as to provide reference for collecting and outputting the feedback signals of drilling feed force for orthopedic virtual surgery system. Methods The biological bone drilling feed force testing system was established by modifying the universal material testing machine and adjustable speed electric drill (drill bit Φ5.0 mm). The feed forces on 6 fresh porcine femoral shafts with a total of 162 drilling markers were collected at 3 different rotate speeds (n＝500, 800, 1 200 r/min) and 3 feed speeds (v＝30, 50, 70 mm/min), and their variation with corresponding tissues and locations were also analyzed. Results At the same drill marker of the fresh porcine femur, the drilling feed force on bilateral cortical bone was the largest (fmax＝103.63~142.59 N), while that on marrow cavity was the smallest, which was almost close to zero, and the drilling feed force on the middle part (f4,5,6＝124.69 N) was larger than that at two ends (f1,2,3,7,8,9＝121.84 N); the drilling feed force was smallest (f＝106.04 N) at v＝30 mm/min, n＝1 200 r/min, while the largest drilling feed force (fmax＝139.84 N) appeared at v＝70 mm/min、n＝500 r/min. Conclusions The modified drilling feed force testing system could efficiently collect the biological bone drilling data. The drilling feed force had a close relationship with bone structure, feed speed and rotate speed of electric drill as well. A larger bone density, smaller rotate speed of electric drill and higher feeding speed would lead to a larger drilling feed force, and vice versa. The accurate drilling feed force data and its variation tendency on porcine femoral obtained in this experiment could provide a reliable basis for force-feedback signal output in the virtual orthopedic surgery system.

Force feedback technology in virtual cardiovascular interventional surgery / 医用生物力学

Virtual technology of cardiovascular interventional surgery can be used for surgical training, surgical navigation, surgical optimization and postoperative evaluation in cardiovascular interventional procedures. In this paper, the composition of virtual cardiovascular interventional operation system was introduced, and the research status of virtual cardiovascular interventional operation both at home and abroad was discussed, including detailed analysis on working principles of several representative products. Through the intensive study on force feedback used as the key techniques in virtual cardiovascular interventional surgery, the author investigated its future development as well as how to improve the training effect and success rate of cardiovascular interventional operation.

Digital robot-aided surgery system based on biomechanical information / 医用生物力学

Objective To establish a set of digital robot-aided surgery system to represent the real surgery process, and realize robot control and force feedback in virtual environment by digital human tissue simulation combined with outer force feedback instrument. Methods The digital robot aided-surgery system design includes human tissue biomechanical modeling, biomechanical model calculation, force feedback instrument design, control algorithm, digital robot-aided surgery system based on biomechanical information. Results After local area network was successfully connected between haptic device control system and virtual environment, the system completed closed-loop information transfer process. Conclusions The robot-aided surgery system can realize the master-slave control, visual feedback and force feedback in virtual environment, which will contribute to the development of digital surgery simulation technology and gain advantages in the aspects of improving surgery success rate and training new doctors.

Model sculpture for virtual coronary artery bypass operation / 医用生物力学

Objective To conduct the operation of capture and deformation in virtual three-dimensional (3D) environment with force feedback device and simulate the coronary artery bypass operation. Methods Based on data collected from real CT images of the patient with heart disease, digitized visual model of the heart was reconstructed. Then the bypass vessel was built and the vessel model was sculptured by force feedback device to simulate the bypass surgery from pulmonary artery to ventriculus dexter in Fontan operation. Results Space structure of the heart was shown in the virtual 3D reconstructed environment. Bypass vessel with any diameter and angle was transformed to simulate the coronary artery bypass operation. Heart patch with any size was built to repair the heart model. The satisfactory model and parameters of the postoperative model were finally achieved. Conclusions The application of force feedback device in virtual coronary artery bypass operation sets the stage for cardiovascular surgery planning system with mechanical characteristics to simulate multiple modalities of such operation.

DEVELOPMENT OF AN ELECTRO-MECHANICALLY CONTROLLED HAND ORTHOSIS FOR ASSISTING FINGER EXTENSION IN STROKE SURVIVORS

Stroke is the leading cause of long-term disability in the world. It causes chronic deficits, such as hemiparesis, especially prevalent in the distal upper extremities. An electro-mechanically driven hand orthosis has been developed to assess the potential therapeutic use of such devices in rehabilitating hand function. A small Direct Current (DC) brushed motor is used as the main actuator, and a cable-driven glove connected to the motor shaft is the central component of the device. The orthosis control is achieved through a force feedback loop using a miniature load cell attached in series to the cable and control module. The later, generates Pulse Width Modulated (PWM) and direction signals required to drive the motor. The speed is determined by the duty cycle of the PWM signal while the direction by the status of a flag bit modified by a user-operated switch. A portable design was achieved by using a 6 V battery pack as the power supply. The device is ready for use in clinical trials with stroke survivor subjects as it has already been tested on healthy individuals with satisfactory performance.

Los accidentes cerebro-vasculares son una de las causas más comunes de discapacidad permanente en los Estados Unidos y el mundo. Esta condición causa déficits crónicos, como la hemiparesis, que es especialmente prevalente en las extremidades distales superiores. Se ha desarrollado una órtesis de mano controlada electromecánicamente para determinar el potencial uso terapéutico de este tipo de dispositivos en la rehabilitación funcional de la mano. Un pequeño motor de corriente directa es utilizado como el actuador principal, y un guante operado mecánicamente por el usuario por medio de un cable es el componte central del dispositivo. El control de la órtesis se logra por medio de un sistema automatizado utilizando un sensor de fuerza conectado al cable del guante. Adicionalmente se usa un microcontrolador para generar la señal de ancho de pulso modulada (PWM) y las señales de dirección requeridas para operar el motor, a una velocidad determinada por el ciclo de trabajo de la señal de PWM y en la dirección determinada por el estado de un bit bandera que es modificado por un interruptor que opera el usuario. El diseño es portátil y el dispositivo está listo para pruebas clínicas, ya que mostró un desempeño aceptable en pruebas iniciales con individuos sanos.

Virtual Laparoscopic Cholecystectomy Simulator Using Force-Feedback Device / 대한의료정보학회지

For the minimally invasive surgery, endoscopic surgery has been being a useful technique in diagnosis and treatment of many kind of human diseases and injuries. But, performing endoscopic operations demand expert skills which allow surgeon to learn navigating complex organs in the body through limited view of endoscope as well as manipulating surgical instruments. So the virtual reality based endoscopic surgery simulator has been great increasingly developed with improvements in computing power, graphic hardware, and haptic device in the recent few years. A good balance between surgical realism and real-time interactive rates of simulation is one of most challenging problems in surgical simulation. And when coupled with precise computations of the forces and deformation of organs, it may be possible for the surgeon to feel haptic sensations close to reality. We describe the virtual laparoscopic cholecystectomy simulator using force-feedback device. A goal of this paper is to improve the realism of simulator through real-time interaction between force-feedback and visual-feedback. To calculate deformation of virtual objects separately from the force-feedback, because the latter must be updated much more frequently, the two feedbacks are implemented in each processor. And pre-calculated data set which used for reducing amount of calculation about deformation results in improvement of the real-time interactive rates between the two feedbacks. When virtual surgical tool, manipulated by the user, was collided with isosurface based organ, the surface was deformed in real-time and the graphics, including tissue deformation, performed at 20~30 frames per second. Simultaneously, force-feedback was transmitted to the user at about 500 times per second, therefore we could implement real-time interactive virtual laparoscopic surgery simulator.