A Virtual Reality Haptic Robotic Simulator for Central Venous Catheterization Training1

摘要

Central venous catheterization (CVC) is a medical procedure performed over five million times a year in the U.S., which allows doctors to deliver medication, nutrition, and take measurements not possible through noninvasive means. During this procedure, a catheter is inserted through the skin into the internal jugular vein (IJ), subclavian vein, or femoral vein with the tip placed near the heart. Unfortunately, some CVC patients experience adverse effects, including pneumothorax, hematoma, hemothorax, accidental arterial puncture, and thrombosis [1]. Currently, medical residents are trained in CVC using mannequin patient simulators, and the concept of “see one, do many, do one competently, and teach everyone” is wide spread [2]. Virtual reality simulators like the Mediseus Epidural simulator have shown great potential as medical training tools by allowing the unique possibility of exposing trainees to a much wider variety of medical scenarios than static patient simulators [3].The design and accuracy of a two-part haptic virtual reality training system for the insertion of a CVC needle into the IJ are introduced in this paper. This system utilizes a Geomagic Touch (Rock Hill, SC) haptic feedback robot and 3D Guidance trakSTAR electromagnetic tracking system by Northern Digital, Inc. (Waterloo, ON). This system allows the user to “scan” the neck using a virtual ultrasound and then feel the haptic forces that occur during needle insertion.The design of the CVC haptic robot simulator is divided into two components: a haptic robot arm and pen representing the syringe, and a position tracking system simulating an ultrasound probe, as shown in Fig. 1. The system is programed using matlab and simulink interfacing with Quanser's Quarc real-time control software. All the imaging used for the virtual ultrasound is in VRML using matlab.The major component of the CVC haptic robot simulator is the haptic robot arm that provides realistic force feedback to the user as shown in Fig. 1. The Geomagic Touch gives 3 deg of force feedback along with 6 deg of position sensing. Using the needle insertion characterizations developed in Gordon et al. [4], which characterize needle force as a piecewise exponential function, this haptic feedback is programed into the device to give the feeling of a needle being inserted into tissue. The virtual needle tip is projected 8 cm away from the robotic pen tip. Small bounding forces are also applied in the direction perpendicular to insertion to restrict the lateral movement when in the virtual tissue. The force characterization equations are interchangeable to allow for a variety of needle insertion scenarios including scar tissue and excess fat tissue.When a simulated needle insertion is performed, simulink exports the position of the ultrasound, position of the needle tip, angle of the needle, final distance from the needle tip to the vein center, and overall test time to matlab. This can then be analyzed to detect known problematic procedure behaviors, such as multiple insertion attempts, and determine the performance of the user.The creation of the virtual ultrasound image begins with the visualization of 3D space as a 2D cutting plane. The IJ and carotid artery (CA) are represented by two circles in a VRML virtual world with 16 circumferential reference points. These reference points can then be scaled in the x and y directions to vary the initial shapes and sizes of the vessels and allow for deformation in the vessel shape. Using the rotation of the 3D tracking device as reference, the images of the vessels stretch in the x and y directions. This mimics how an ultrasound plane through the vessels appears when placed in the transverse and longitudinal directions. The needle can then interact with the position of these data points to simulate vessel flexibility. Virtual patient anatomy can be easily varied by moving the vessel positions in the virtual tissue.An essential component of the ultrasound is the