Philip S. Green

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>>

Vascular applications of telepresence surgery: Initial feasibility studies in swine

PURPOSE Telepresence surgery is a novel technology that will allow procedures to be performed on a patient at locations that are physically remote from the operating surgeon. This new method provides the sensory illusion that the surgeons hands are in direct contact with the patient. We studied the feasibility of the use of telepresence surgery to perform basic operations in vascular surgery, including tissue dissection, vessel manipulation, and suturing. METHODS A prototype telepresence surgery system with bimanual force-reflective manipulators, interchangeable surgical instruments, and stereoscopic video input was used. Arteriotomies created ex vivo in segments of bovine aortae or in vivo in femoral arteries of anesthetized swine were closed with telepresence surgery or by conventional techniques. Time required, technical quality (patency, integrity of suture line), and subjective difficulty were compared for the two methods. RESULTS All attempted procedures were successfully completed with telepresence surgery. Arteriotomy closures were completed in 192+/-24 sec with conventional techniques and 483+/-118 sec with telepresence surgery, but the precision attained with telepresence surgery was equal to that of conventional techniques. Telepresence surgery was described as intuitive and natural by the surgeons who used the system. CONCLUSIONS Blood-vessel manipulation and suturing with telepresence surgery are feasible. Further instrument development (to increase degrees of freedom) is required to achieve operating times comparable to conventional open surgery, but the system has great potential to extend the expertise of vascular surgeons to locations where specialty care is currently unavailable.

A New, High-Performance Ultrasonic Camera

By virtue of their true-perspective presentation, focused and holographic methods of ultrasonic imaging hold great promise for soft tissue visualization. However, none of the numerous methods demonstrated to date combine the features required of a clinically useful instrument.

Ultrasonic transducer system and method

An ultrasonic transducer system for use with tissue is shown, which system includes a container of liquid acoustic coupling medium within which focused transducer means are located. Focusing of the transducer means may be effected acoustically, as by use of an acoustic lens, and/or electronically, as by use of a transducer array. The liquid medium container is closed at one end by a rigid acoustically transparent window, or diaphragm, for acoustically coupling to the skin and underlying tissue of the subject under investigation. The material of the liquid acoustic coupling medium is selected so that the velocity of propagation of acoustic waves therein is substantially less than the velocity of the acoustic waves within the tissue under investigation. By using a low speed-of-sound coupling medium a shorter propagation path may be employed than is required by prior art transducer arrangements in which the speed-of-sound in the tissue and coupling fluid is substantially the same. Operation in either scanning or non-scanning modes is contemplated, and scanning, when employed, may be effected mechanically or electronically. In the sector scanning mode, the system may be operated in a manner such that the angular sector swept out by the focused beam in the tissue exceeds that in the low speed-of-sound liquid coupling medium as a result of refraction at the window interfaces.

Ultrasonic Reflex Transmission Imaging

Reflex Transmission Imaging (RTI) is a new imaging method by which orthographic transmission images can be made using augmented B-mode equipment. Conventional transmission imaging requires acoustic coupling to large areas on both sides of the body, whereas RTI can be performed from one side with a single, small transducer probe. In this mode, transmission images in a plane normal to the beam are made by integrating the reverberations from beyond the focal zone of the transducer. These reverberations provide, in essence, a source of incoherent insonification from behind the focal plane. Preliminary in-vitro images have been made using a computer-interfaced rectilinear scanner with a 1-inch diameter f/2.8 transducer. The images have good resolution and signal-to-noise ratio, and a short depth-of-field. Backscatterer inhomogeneity is well smoothed. Transmission images provide information that is complementary to B-scans. RTI will allow both to be made with the same instrument and presented on the same display. A time-gated reflection C-scan could be generated simultaneously. Other RTI modes, including an attenuation B-mode, also are discussed.

Considerations for Diagnostic Ultrasonic Imaging

It is becoming increasingly apparent that ultrasonic imaging (focused and holographic) will develop into a useful tool for diagnostic medicine. In this paper we examine the benefits to be derived with this application, particularly as they compare to the results obtainable with currently-used techniques of diagnostic ultrasonics.

A real-time ultrasonic imaging system for carotid arteriography

Abstract A real-time ultrasonic imaging system for the noninvasive assessment of atherosclerotic vascular disease has been developed. This instrument displays cross-sectional images of the artery and surrounding tissues plus superimposed profiles of blood flow within the vessel. The anatomical structure is depicted by a 10-MHz B -scan subsystem operating at 15 frames/sec. An instantaneous profile of the blood flow velocity is produced by a 5-MHz pulsed Doppler subsystem that can display the velocity at up to 20 individual points along a line segment intersecting the artery. Cross-sectional high-resolution gray-scale images, both transverse and longitudinal, of the major vessels in the neck in the region of the carotid bifurcation are presented. These images also demonstrate the skin, subcutaneous fat, muscle, and thyroid gland. Estimates of severity of atherosclerotic disease measured as percentage of lumen diameter obstructed by each lesion, are essentially the same as subsequent estimates made using roentgen angiography. Pulsating blood flow profiles in the common carotid have been clearly displayed; however, clinical applicability of the Doppler subsystem is not yet demonstrated.

Combined reflection and transmission ultrasound imaging

Reflex transmission imaging (RTI) is a method for producing orthographic ultrasound transmission images, which depict focal-plane transmittance, by using a single transducer rather than an opposed transducer pair. RTI can be implemented using modified B-scan equipment, and a bidirectional scan probe. It has the further advantage of enabling simultaneous generation of integrated reflection C-scan (IRCS) images, which depict backscatter from the focal plane, in perfect registration with the transmission images. We describe these methods, demonstrate a new process by which the reflection and transmission images can be combined to produce a new image of superior quality, and demonstrate the applicability of this technique to improved visualization of kidney stones, with potential application to lithotripsy.

A New Liquid-Surface-Relief Method of Acoustic Image Conversion

The liquid-surface-relief method of acoustic image conversion is one of the two earliest methods to be devised for the real-time visualization of ultrasonic images (the other being the electron-beam scanning tube of Sokolov). It is certainly the most easily demonstrated. In the early versions1 demonstrated by Topler and Sokolov, an ultrasonic image field focused onto the liquid surface causes the surface to elevate at each point until equilibrium is established by the restoring forces of surface tension and gravity. The relief pattern formed in this way is an analog of the pattern of acoustic intensity incident at the surface. The deformed fluid surface serves as an optical “phase-object,” and a visible representation of the ultrasonic image is produced by reflecting light from or refracting it through the surface and subsequently forming an image of the deformation pattern, using one of several phase-contrast imaging techniques.

Spatially and Temporally Varying Insonification for the Elimination of Spurious Detail in Acoustic Transmission Imaging

Acoustic transmission images obtained with spatially coherent insonification are often difficult to interpret since complex interference patterns are superimposed on pertinent object details.