Dexter G. Smith

Wide bandwidth time-domain electromagnetic sensor for metal target classification

A portable, wide bandwidth, time-domain electromagnetic sensor system has been developed and used extensively to measure the eddy current time-decay response of a wide variety of metal targets. The sensor has demonstrated the ability to measure metal target decay times starting approximately 3 to 5 /spl mu/s after the transmitter current is turned off and target decay time constants as short as 1.4 /spl mu/s. The sensor has demonstrated the potential for detecting very low-metal content mines due to the void they create in some types of electrically lossy soils. The development of the sensor is described in detail, and time-decay data are shown for a variety of metal targets, including low metal antitank and antipersonnel mines.

In vivo measurement of tumor conductiveness with the magnetic bioimpedance method

A noninvasive electromagnetic method has been developed that can effectively measure the in-vivo conductivity difference between rat tumor lines having a low and high metastatic potential. These tumor lines are used in the study of human prostate tumor.

Bioimpedance: Novel Use of a Minimally Invasive Technique for Cancer Localization in the Intact Prostate

BACKGROUND. Prostate cancer is presently diagnosed by transrectal ultrasound (TRUS)guided sextant needle biopsy. While echo texture of the tissue can prompt localization of tumor, it is presently imprecise. From 50‐75% of men biopsied, based on an abnormal digital rectal examination (DRE) or elevated prostate-specific antigen (PSA) level, have negative biopsy results. Improvements in tumor localization during TRUS-guided prostate biopsy are greatly needed. Bioimpedance is an electrical property of biologic tissue. Electric current is limited in living tissue by highly insulating cell membranes; however, different tissue architecture such as cancer may impede current differently and allow detection of differences between normal and abnormal or malignant prostate tissue. Our goal was to assess the utility of bioimpedance measurements in differentiating tumor from normal prostatic tissue in an ex vivo model. METHODS. Bioimpedance was measured in six ex vivo prostates, which were removed for clinically localized prostate cancer. Two bioimpedance needles, 1 mm apart, were inserted 3 mm into the posterior surface of the prostate an average of 16 times per gland. Frequencies ranging from 100 kHz‐4 MHz were used to obtain 594 bioimpedance measurements from the six glands. These measurements were then correlated with histology to determine the presence or absence of prostate cancer. RESULTS. Prostate cancer was found to have a higher impedance, of 932 ± 170 ohms, compared to areas of no cancer within the same prostate, 751 ± 151 ohms, P < 0.0001, at 2 MHz. This phenomenon was observed across all frequencies tested. CONCLUSIONS. This study demonstrates for the first time application of bioimpedance to distinguish areas of prostate cancer from areas of normal prostate. This technology may improve identification and localization of cancer within the prostate. Moreover, bioimpedance can potentially guide needle placement during prostate biopsy and thus improve sampling of tumors. Currently, our ex vivo model is limited by variables such as temperature and lack of blood flow. Further studies in an in vivo model will be needed to assess their effect. Prostate 39:213‐218, 1999.

Evolution of a New Series of Self-contained Micromechanical Ventilators for Prehospital Use

Immediate medical care can dramatically reduce the number of fatalities sustained during military operations. However, the shift from large-scale regional conflicts to smaller peacekeeping and humanitarian missions has reduced the military medical support infrastructure. In the civilian emergency medical services arena, there has long been an emphasis on the golden hour during which a patient must receive definitive medical attention. Without on-scene medical support, injured soldiers must be transported significant distances before receiving definitive medical care, and rapid transport to a medical facility is not always a viable option. We reported here three years ago on the development of an early prototype portable ventilator with basic functionality. Since that time, four new prototypes with varying capabilities and sizes have been developed. Each of these fits a particular role in military or civilian use. The design goals and tradeoffs for each unit will be discussed, as well as the design implementation used to achieve those goals.

Electromagnetic holographic imaging of bioimpedance

The electromagnetic bioimpedance method has successfully measured the very subtle conductivity changes associated with brain edema and prostate tumor. This method provides noninvasive measurements using non-ionizing magnetic fields applied with a small coil that avoids the use of contact electrodes. This paper introduces results from combining a holographic signal processing algorithm and a low power coil system that helps provide the 3D image of impedance contrast that should make the noninvasive electromagnetic bioimpedance method useful in health care.

Applying a service-based architecture to autonomous distributed sensor networks

Traditional distributed architectures are not sufficient when developing an autonomous, distributed sensor network. In order to be truly autonomous, a distributed sensor network must be able to survive and reconfigure in-the-field without manual intervention. A limitation of traditional distributed architectures, such as client/server or peer-to-peer, within an autonomous network is that the distributed devices and applications are tightly coupled by their communication protocols prior to implementation and deployment. The introduction of new devices and applications in the field is difficult due to this coupling. Also, autonomous reconfiguration of the devices on the network due to faults or addition of new devices is extremely difficult unless the devices are homogeneous. A service-based architecture is proposed as an alternative architecture for creating autonomous, distributed sensor networks. The service-based approach provides the ability to create a scalable, self-configuring, and self-healing network for building and maintaining large, emerging and ad-hoc virtual networks of devices and applications. New devices can be automatically discovered by current devices on the network and automatically integrated into the system without manual intervention. This paper will explain the benefits and limitations of applying a service-based architecture to autonomous, distributed sensor networks and compare this approach with traditional architectures such as client/server and peer-to-peer. A description will be given of a prototype system developed using service-enabled seismic, acoustic, and visual sensors.

Far-forward life support system prototype

The Far Forward Life Support System (FFLSS) is intended for US Army use in far forward, battlefield situations. The primary patient population is young, otherwise healthy, adult males. The FFLSS must provide stabilizing medical care in the far forward environment. The device must be easily operated, highly mobile, compact and rugged, and provide automated, definitive support for a minimum of one hour. This project design, fabricated and tested a prototype FFLSS.