Showing papers by "Andrew A. Goldenberg published in 2017"

Signal-to-noise ratio evaluation of magnetic resonance images in the presence of an ultrasonic motor.

Abstract: Safe robot-assisted intervention using magnetic resonance imaging (MRI) guidance requires the precise control of assistive devices, and most currently available tools are rarely MRI-compatible. To obtain high precision, it is necessary to characterize and develop existing MRI-safe actuators for use in a high magnetic field (≥3 T). Although an ultrasonic motor (USM) is considered to be an MRI-safe actuator, and can be used in the vicinity of a high field scanner, its presence interferes with MR images. Although an MR image provides valuable information regarding the pathology of a patient’s body, noise, generally of a granular type, decreases the quality of the image and jeopardizes the true evaluation of any existing pathological issues. An eddy current induced in the conductor material of the motor structure can be a source of noise when the motor is close to the isocenter of the image. We aimed to assess the effects of a USM on the signal-to-noise ratio (SNR) of MR images in a 3-T scanner. The SNR was compared for four image sequences in transverse directions for three orientations of the motor (x, y, and z) when the motor was in the “off” state. The SNR was evaluated to assess three artifact reduction methods used to minimize the motor-induced artifacts. The SNR had a range of 5–10 dB for slices close to the motor in the x and y orientations, and increased to 15–20 dB for slices far from the motor. Averaging the SNR for slices in all cases gave an SNR loss of about 10 dB. The maximum SNR was measured in the z orientation. In this case, the SNR loss was almost the same as that of other motor orientations, approximately 10 dB, but with a higher range, approximately 20–40 dB. The selection of certain scanning parameters is necessary for reducing motor-generated artifacts. These parameters include slice selection and bandwidth. In developing any MRI-compatible assisted device actuated by a USM, this study recommends the use of an approximately 3-mm slice thickness with minimum bandwidth to achieve optimized SNR values when a USM is operating close to (within approximately 40 mm) the region being imaged. The SNR can be further enhanced by increasing the number of signal averages, but this is achieved only at the cost of increased scan duration.

Two joint module and arm using same

Abstract: A two joint module includes a housing and a pair of hollow rotary actuator assemblies. Each actuator assembly has an axis and a hollow shaft and the axes are arranged at an angle to each other. The pair of hollow rotary actuator assemblies are arranged back to back and attached to the housing such that cables can be fed from the outside of one of the pair of hollow rotary actuator assemblies to the inside thereof and to the inside of the other of the pair of hollow rotary actuator assemblies to the outside thereof. The disclosure also relates to a robotic arm. The robotic includes at least two two joint modules as described herein and at least a first link.

Measuring the Temperature Increase of an Ultrasonic Motor in a 3-Tesla Magnetic Resonance Imaging System

Abstract: This paper aims to evaluate the temperature increase caused by a 3.0-T magnetic resonance imaging (MRI) system on an ultrasonic motor (USM) used to actuate surgical robots in the MRI environment. Four fiber-optic temperature sensors were attached to the USM. Temperature was monitored outside the five-Gauss boundary and then inside the bore for 20 min while the USM was powered on. The USM temperature was tested for two states of the scanner, “off” and “on”, by employing common clinical imaging sequences and echo planar imaging sequences. The USM showed a slight temperature increase while operating in the static field of the MRI. A considerable temperature increase (~10 °C) was observed when the scanner was on. The temperature increased to 60 °C, which is beyond the acceptable safe temperature and can result in thermal burns. Most of the temperature increase (80%) was due to effects of the static field on the motion of the rotating parts of the motor, while the remainder (20%) derived from heat deposited in the conductive components of the USM due to radiofrequency pulses and gradient field changes. To solve the temperature increase, the metal components of the USM’s case can be replaced by silicon carbide.

Quantification of Force and Torque Applied by a High-Field Magnetic Resonance Imaging System on an Ultrasonic Motor for MRI-Guided Robot-Assisted Interventions

Abstract: The risk of accidental dislodgement of robot-operated surgical mechanisms can lead to morbidity or mortality The force and torque applied by a 30-tesla scanner on an ultrasonic motor are not fully known The force and torque may displace the motor, which is not fully magnetic resonance imaging (MRI)-compatible but can be safely used in MR environments A suspension apparatus was designed to measure the angles of deflection and rotation applied to the motor by MR magnetic fields Three orientations and two power states of the motor were assessed inside the MR bore The displacement force and torque were measured at eight locations with respect to the bore The displacement force on the motor from 10 cm outside the magnet bore to 20 cm inside the bore ranged from 3 to 7 gF The experimental measurements are in agreement with the theoretical values Running the motor altered the force by 1 gF The force does not significantly change when the MRI scanner is on Considerable displacement force is applied to the motor, and no deflection torque is observed Quantified values can be used to solve dynamic equations for robotic mechanisms intended for MRI-guided operations

Development and control of a magnetorheological haptic device for robot assisted surgery

Abstract: A prototype magnetorheological (MR) fluid-based actuator has been designed for tele-robotic surgical applications. This device is capable of generating forces up to 47 N, with input currents ranging from 0 to 1.5 A. We begin by outlining the physical design of the device, and then discuss a novel nonlinear model of the device's behavior. The model was developed using the Hammerstein-Wiener (H-W) nonlinear black-box technique and is intended to accurately capture the hysteresis behavior of the MR-fluid. Several experiments were conducted on the device to collect estimation and validation datasets to construct the model and assess its performance. Different estimating functions were used to construct the model, and their effectiveness is assessed based on goodness-of-fit and final-prediction-error measurements. A sigmoid network was found to have a goodness-of-fit of 95%. The model estimate was then used to tune a PID controller. Two control schemes were proposed to eliminate the hysteresis behavior present in the MR fluid device. One method uses a traditional force feedback control loop and the other is based on measuring the magnetic field using a Hall-effect sensor embedded within the device. The Hall-effect sensor scheme was found to be superior in terms of cost, simplicity and real-time control performance compared to the force control strategy.

Surgery robot , surgery robot subassembly and modularization surgery robot that can reshuffle

Abstract: The utility model discloses a modularization that supplies to use with the operation instrument can reshuffle surgery robot, surgery robot subassembly and surgery robot in relevancyly Surgery robot contains: a linear module for the linear removal, a capstan head module for the swivelling movement, an elbow roll module for the swivelling movement, and be used for the wrist slope module of swivelling movement The capstan head module has the capstan head rotation axis An elbow roll rotation axis for rotating elbow roll module have and become an angle with the capstan head rotation axis Wrist slope module has wrist slope rotation axis, wrist slope rotation axis becomes an angle with capstan head rotation axis and elbow roll rotation axis Link together in order to form surgery robot, just linear module, capstan head module, elbow roll module and wrist slope module maneuverability be connected to the operation instrument maneuverability in the module Surgery robot can contain one the hunch formula device unit of attachable to other modules in

Mobile robot with a flexible deployable tail

Abstract: A mobile robot includes a deployment mechanism and a flexible tail. The flexible tail is attached to the deployment mechanism and extends outwardly from the mobile robot in a deployment direction. Actuation of the deployment mechanism moves the flexible tail and changes the deployment direction of the flexible tail. Movement of the flexible deployable tail allows the used to change the centre of mass of the mobile robot. As well in use the flexible deployable tail can help to stabilize the mobile robot when it is climbing stairs. As well, the flexible deployable tail can help the robot to absorb energy if it contacts a solid object.