Detection of internal puncture during manual needle insertion is challenging due to the large friction force between a needle shaft and surrounding tissue, which masks small changes in force at the needle tip. A novel robotic coaxial needle insertion assistant was developed to enhance operator perception during epidural puncture. The coaxial needle separates the cutting force at the needle tip from shear friction on the needle shaft. When the assistant is inactive, the human operator controls the motion of the coaxial needle. When the assistant is active under position control, a motor controls the motion of the outer needle, while the operator controls only the motion of the inner needle. When the assistant is active under force control, the operator controls the motion of the entire needle, but receives force feedback that is a scaled version of the force applied by the needle tip to the tissue. The effectiveness of the assistant in enabling puncture detection was tested in an experiment in which users were asked to puncture artificial tissues with the assistant inactive and active. Results show that the ratio of successful to unsuccessful puncture detection was higher with the assistant than without. In addition, users were more confident that they could perceive the moment of puncture. However, when the users successfully perceived puncture, overshoot with the assistant was larger than without.

A numerical simulation of the magnetic field in the imaging volume of a magnetic resonance imaging (MRI) scanner and a method for quick searches for electromagnetic noise source are proposed as part of the design and development process for surgical robots that are compatible with MRI. Although MR compatibility is a major challenge for development of such robots, no simulation method was known that could predict it. This paper demonstrates the potential of two basic techniques that are useful in predicting the magnetic and electromagnetic compatibility. First, the distortion of the magnetic field caused by the robot can be computed by a finite element method. Simulation of the resonance signal distribution showed good agreement with experimentally obtained signal distributions. Second, a noise source and its strength can be visualized by a spectrum analyzer

In this paper, a novel mechanism of remote actuation was proposed and its mechanical problems were discussed. This mechanism consists of leverage and parallelogram mechanism and transmits 3 d.o.f translational and 3 d.o.f rotational motions from the input to output. Such a remote actuation is significantly useful for robotic assist around MRI where the strong and precise magnet is used for imaging, because mutual effect between MRI and robot are inverse proportional to the distance. In this paper, the basic ideas of mechanism were introduced firstly. The discussions of its stiffness and workspace conclude their trade-off. Our new idea of workspace control for mechanical safety is preliminary discussed.

A magnetic resonance (MR) compatible surgical assistance robot system, designed to aid minimally invasive surgical techniques, such as positioning and directing a catheter or a laser pointer, has been built and is under preclinical evaluation. Two specific issues arise in the MR environment: (i) the reduced space in which to place the robot; and (ii) the MR compatibility. The main mechanical body is located above the head of the surgeon, with two rigid, hanging arms that reach into the workspace. This novel configuration contributes to a small occupancy in the workspace and to the MR compatibility. The robot is also carefully designed for safety and sterilization issues. Details of the kinematics and the design of the robot are given, and the MR compatibility is examined. This shows that the robot has no adverse effect on the imaging, even when it is in motion.