Joel F. Jensen

Telepresence surgery demonstration system

Endoscopic surgical methods are replacing open surgery in many procedures, but dexterity and force feedback are not adequate with current tools. To enhance the ability of surgeons to operate endoscopically, we have developed a telepresence system with integrated 3D stereo viewing, a prototype force-reflecting manipulator, and aural feedback. Careful attention was paid to the human factors in the endoscopic surgery setting to make the system natural to use in the hope of eliminating the long training period normally required. The 4-axis (plus gripper) manipulator provides the same degrees of freedom as the laproscopic tools now being used for surgery. The bilateral control system provides for magnified motion and/or force reflection. This approach eliminates the motion reversal, or fulcrum effect, in operating through the abdominal wall. Preliminary dexterity experiments with different force feedback and viewing conditions verify intuitive use and fast learning.<<ETX>>

Reflex Transmission Imaging: Visualization and Evaluation of Calculi for Lithotripsy

Reflex transmission imaging (RTI) is a method for producing orthographic images that depict focal-plane ultrasonic transmittance.1–4 Unlike conventional transmission imaging methods, which require an opposing pair of transducers, RTI can be implemented using modified B-mode equipment and a bidirectional scan probe. Contemporaneously, an integrated reflection C-scan (IRCS) image can be generated, representing the focal plane reflectivity. The two images are in perfect registration, and reveal complementary information. In this study, we use these methods to image human gallstones and kidney stones in tissue phantoms, both before and after their disintegration by a piezoelectric lithotripter.

Reflex Transmission Imaging

Reflex transmission imaging (RTI) is a method for making orthographic acoustic transmission images without requiring the presence of an acoustic source on the opposite side of the object. It is well-suited to imaging specific planes in objects of moderate scatter cross section, such as human tissue. Each pixel of the image is formed by pulsing a transducer that is well-focused at the image plane, then rectifying and integrating the signals received from a selected range zone beyond the focus. This zone acts as a spatially and temporally incoherent insonification source. The pixel value is diminished twice by the attenuation at that focal point. A complete image is produced by raster scanning or bidirectional sector scanning; a reflection C-scan can be acquired simultaneously. Reflex transmission images can be made with a relatively small transducer. For medical diagnosis, RTI can be readily integrated with a real-time B-scanner, allowing multimodal imaging. The RTI process also can be used to form attenuation B-mode images.

Multiplane Deconvolution in Orthographic Ultrasonic Transmission Imaging

Orthographic ultrasonic transmission imaging has received renewed interest and demonstrated significant potential clinical applicability during the past few years. The ultrasonic camera developed at SRI for the Orthopaedic Clinic of the University of Muenster in West Germany is an example of a real-time ultrasonic transmission imaging system. Using a spatially and temporally incoherent method of insonification, which eliminates diffraction artifacts and smoothly blurs out-of-focus structures, the SRI camera produces sharply focused images within the focal plane. Although well-focused images can be obtained in orthographic transmission imaging, the overlapping of out-of-focus structures frequently detracts from image quality. To overcome this difficulty and to extend the applicability of ultrasonic transmission imaging, we proposed to apply image-processing techniques to remove out-of-focus structures through multiplane deconvolution. We used a linear model for the imaging process and investigated different algorithms for the multiplane deconvolution. Our simulation results show that an algorithm based on the minimum mean square error appears to be the most effective. We have also applied the algorithm to improve the images collected with an experimental ultrasonic transmission imaging system. In this paper, we briefly describe the principles of multiplane deconvulution and present simulation and experimental results that illustrate its effectiveness in improving the image quality.