Stephen William Smith - US grants

This is a request for partial funding for a workshop on "Ultrasound Transducers: The Next Generation". The workshop is to take place on the Duke campus on Sept. 10- 11, 1990. The workshop is to include leading researchers both from the U.S. and foreign countries, and will examine those areas where transducers still hamper full utilization of ultrasound technology in biomedical applications. The workshop is co-sponsored by the Duke ERC.

9415342 Smith The research proposed in this application is concerned with an improved 2-D ultrasonic transducer by using opto- electronic transmitter technology to replace power amplifiers and coaxial cables. Low power diode lasers, optical fibers and photo conductive switches will be used in the new system. The research has the potential to eliminate the bulky transducer cables now used in high density ultrasonic arrays, and thus allow the system to be more flexible and to consist of more transmit channels. ***

9414558 Casey A major practical limitation to the application of high resolution two-dimensional ultrasonic imaging is the size and flexibility of the cable linking the transmitter/receive transducer element with the powering and processing electronics. The PI's have successfully fabricated a prototype based on a combination of a fiber optics and integrated optoelectronics, which would replace the cumbersome coaxial cable currently used to excite the transmit pulses for relatively small linear transducer arrays. They propose the use of the Electronics and Power Sources Directorate (EPSD) facility for assistance in the design and fabrication of the photoconductive semiconductor switch (PCSS) which is the critical element of our approach. Support of the proposed research would be in direct support of advanced biomedical ultrasound techniques already being partially supported by the National Science Foundation as well as Army interests in the application of high resolution ultrasonic non-destructive evaluation (NDE) to materials and structures of military significance. ***

DESCRIPTION (Adapted from Applicant's Abstract): Although intra-luminal ultrasound scanning has been developed with some degree of success for the imaging of the cardiovascular system, the circular side scanning geometry of the catheter ultrasound transducer is intrinsically unsuitable for many diagnostic applications. The objective of this application is the improvement of real time intra-luminal scanning via the development of a new generation of miniature forward looking mechanical sector scanners incorporating high frequency transducers above 20 MHz to enable improved guidance of cardiac interventional procedures. Each piezoelectric transducer is driven by a tiny linear actuator operating electrostatic forces combined with pivoting hinges to produce a sector scan. The linear actuator is an example of a microelectromechanical system (MEMS), now one of the most important research fields of microelectronics. The transducer / MEMS assembly will be totally housed within a cardiac catheter. Applications may include: 1) real time intra-luminal sector scanning of the heart at 20-40 MHz; 2) real time intra-vascular sector scanning at 20-50 MHz; 3) real time intra-luminal volumetric scanning; 4) the combination of cardiac intra- ventricular ultrasound imaging with electrophysiological endocardial mapping; 5) the combination of intra-luminal ultrasound imaging and intra-luminal radio-frequency or ultrasound thermal ablation.

Triple immunosuppressant therapy with cyclosporine (CsA), prednisone, and azathioprine has been the mainstay of initial maintenance immunosuppression for renal transplantation in the U.S. These drugs have different mechanisms of action and different toxicities. CsA causes scarring of the transplanted kidney in many patients. Many patients do well with only two immunosuppressant agents late after renal transplantation, however, there are no controlled comparative trials of the withdrawal of immunosuppressant agents. Mycophenolate mofetil (MMF) when used with CsA and steroids in two large randomized trials reduced the rate of acute rejection in the first year post transplant to about half the rate obtained when CsA/azathioprine/steroids were used. Thus the rate of acute rejection following withdrawal of CsA or steroids will likely be lower with the substitution of MMF for azathioprine. This is an open label, randomized, controlled, therapeutic comparison trial, limited to patients at low risk for acute rejection following a decrease in immunosuppression. The primary hypothesis is that withdrawal of cyclosporine in stable renal allograft recipients 12 months or more after transplantation results in a slower decline in renal function and less kidney scarring than withdrawal of either mycophenolate or prednisone.

[unreadable] DESCRIPTION (provided by applicant): [unreadable] Real time trans-thoracic volumetric scanning, using 2-D array transducers based on Duke University designs, offers potential to increase the accuracy of cardiac measurements such as ventricular volumes and improve the diagnosis of coronary heart disease. The objective of this proposal is to extend the advances of real time volumetric scanning to transesophageal endoscopes, surgical endoscopes for applications in minimally invasive cardiac surgery. In this research, we will develop new 2D array transducers including cylindrical and hemispherical curvilinear probes operating from 5-10 MHz which produce a panoramic 3-D field of view approaching 1800. We will also develop an intracardiac catheter which combines 3-D ultrasound imaging and endocardial ultrasound thermal ablation system integrated within a single catheter delivery device for applications to the cardiac arrhythmias and interventional cardiology. [unreadable] [unreadable]

vitamin B12; vitamin B6; folate; human therapy evaluation; dietary supplements; kidney transplantation; dosage; diet therapy; homocysteine; patient oriented research; human subject; clinical research;

DESCRIPTION (provided by applicant): There is growing evidence of the clinical benefits of real-time 3-D ultrasound for transthoracic cardiovascular applications using 2-D array transducers as originally developed in our laboratories at Duke University. More recently we have achieved a number of significant advances by expanding real time 3D echocardiography to intra-cardiac (3D-ICE), intra-vascular (3D-IVUS), transesophageal (3D-TEE) and thoracoscopic and laparoscopic (3D-LUS) applications by developing 2D array transducers at the tips of catheters and endoscopic probes for the guidance of minimally invasive cardiovascular procedures. The last decade has also seen tremendous breakthroughs in the development and application of interventional medical devices including vascular stents, aortic aneurysm stent grafts, vena cava filters, vascular occluders, cardiac occluders, prosthetic cardiac valves, and catheter and needle delivery of radio frequency ablation. Each minimally invasive procedure involves extensive real time imaging to guide the deployment of these devices currently requiring long periods of x-ray fluoroscopy with its inherent disadvantages of ionizing radiation exposure, poor tissue contrast and requirement for nephrotoxic contrast agents in angiography. Our hypothesis is that we can develop new generations of miniature 2D array transducers integrated into the deployment kits for these interventional devices to enable real time 3D ultrasound scanning for improved guidance of minimally invasive procedures. Thus in our specific aims we will extend our previous advances in cardiovascular real time 3D ultrasound by developing integrated catheter array transducers to guide the implantation of two important interventional cardiovascular devices from those listed above. We propose: (1) To investigate 3D ultrasound guidance of the deployment of the vena cava filter which prevents a venous thrombus from embolizing to the pulmonary circulation. (2) To investigate 3D ultrasound guidance of the aortic stent graft which isolates a weakened abdominal aortic aneurysm wall from the arterial circulation. (3) To conduct in vitro and in vivo evaluation of integrated catheter arrays for the aortic aneurysm stent graft and vena cava filter. Our long term goals are to significantly reduce exposure to ionizing radiation and x-ray contrast agents during these procedures while working toward the possibility of bedside implantation of vena cava filters and evaluating the patency of the aortic stent graft and its associated vasculature.