ABSTRACT
3D ultrasound imaging has enabled minimally invasive, beating heart intracardiac procedures. However, rapid heart motion poses a serious challenge to the surgeon that is compounded by significant time delays and noise in 3D ultrasound. This paper investigates the concept of using a one-degree-of-freedom motion compensation system to synchronize with tissue motions that may be approximated by 1D motion models. We characterize the motion of the mitral valve annulus and show that it is well approximated by a 1D model. The subsequent development of a motion compensation instrument (MCI) is described, as well as an extended Kalman filter (EKF) that compensates for system delays. The benefits and robustness of motion compensation are tested in user trials under a series of non-ideal tracking conditions. Results indicate that the MCI provides an approximately 50% increase in dexterity and 50% decrease in force when compared with a solid tool, but is sensitive to time delays. We demonstrate that the use of the EKF for delay compensation restores performance, even in situations of high heart rate variability. The resulting system is tested in an in vitro 3D ultrasound-guided servoing task, yielding accurate tracking (1.15 mm root mean square) in the presence of noisy, time-delayed 3D ultrasound measurements.
ABSTRACT
The recent advent of real-time 3-D ultrasound (3DUS) imaging enables a variety of surgical procedures to be performed within the beating heart. Implementation of these procedures is hampered by the difficulty of manipulating tissue guided by the distorted, low resolution 3DUS images and the dexterity constraints imposed by the confined intracardiac space. This paper investigates the use of surgical robotics in conjunction with 3DUS to overcome these limitations. In addition, it describes the development of a graphics processor based volume Tenderer for real-time stereo visualization of the ultrasound data. Stereo displayed 3DUS was compared to ID-displayed 3DUS and endoscopic guidance with a user study. Five subjects performed in vitro surgical tasks using a surgical robot. Results indicate that subjects were able to complete surgical tasks 35 % faster with stereo-displayed 3DUS images compared to conventional two dimensional display of 3DUS.
Subject(s)
Data Display , Image Interpretation, Computer-Assisted/instrumentation , Imaging, Three-Dimensional/instrumentation , Photogrammetry/instrumentation , Robotics/instrumentation , Surgery, Computer-Assisted/instrumentation , Ultrasonography, Interventional/instrumentation , Equipment Design , Equipment Failure Analysis , Image Interpretation, Computer-Assisted/methods , Imaging, Three-Dimensional/methods , Photogrammetry/methods , Reproducibility of Results , Robotics/methods , Sensitivity and Specificity , Surgery, Computer-Assisted/methods , Ultrasonography, Interventional/methods , User-Computer InterfaceABSTRACT
BACKGROUND: The recent advent of real-time 3D ultrasound (3DUS) imaging enables a variety of new surgical procedures. These procedures are hampered by the difficulty of manipulating tissue guided by the distorted, low-resolution 3DUS images. To lessen the effects of these limitations, we investigated stereo displays and surgical robots for 3DUS-guided procedures. METHODS: By integrating real-time stereo rendering of 3DUS with the binocular display of a surgical robot, we compared stereo-displayed 3DUS with normally displayed 3DUS. To test the efficacy of stereo-displayed 3DUS, eight surgeons and eight non-surgeons performed in vitro tasks with the surgical robot. RESULTS: Error rates dropped by 50% with a stereo display. In addition, subjects completed tasks faster with the stereo-displayed 3DUS as compared to normal-displayed 3DUS. A 28% decrease in task time was seen across all subjects. CONCLUSIONS: The results highlight the importance of using a stereo display. By reducing errors and increasing speed, it is an important enhancement to 3DUS-guided robotics procedures.
