Jack E. Bridges

Correction to "Two-Dimensional FDTD Analysis Of A Pulsed Microwave Confocal System For Breast Cancer Detection: Fixed-Focus And Antenna-Array Sensors"

A novel focused active microwave system is investigated for detecting tumors in the breast. In contrast to X-ray and ultrasound modalities, the method reviewed here exploits the breast-tissue physical properties unique to the microwave spectrum, namely, the translucent nature of normal breast tissues and the high dielectric contrast between malignant tumors and surrounding lesion-free normal breast tissues. The system uses a pulsed confocal technique and time-gating to enhance the detection of tumors while suppressing the effects of tissue heterogeneity and absorption. Using published data for the dielectric properties of normal breast tissues and malignant tumors, the authors have conducted a two-dimensional (2-D) finite-difference time-domain (FDTD) computational electromagnetics analysis of the system. The FDTD simulations showed that tumors as small as 2 mm in diameter could be robustly detected in the presence of the background clutter generated by the heterogeneity of the surrounding normal tissue. Lateral spatial resolution of the tumor location was found to be about 0.5 cm.

Three-dimensional FDTD analysis of a pulsed microwave confocal system for breast cancer detection: design of an antenna-array element

We are investigating a new ultrawide-band (UWB) microwave radar technology to detect and image early-stage malignant breast tumors that are often invisible to X rays. We present the methodology and initial results of three-dimensional (3-D) finite-difference time-domain (FDTD) simulations. The discussion concentrates on the design of a single resistively loaded bowtie antenna element of a proposed confocal sensor array. We present the reflection, radiation, and scattering properties of the electromagnetic pulse radiated by the antenna element within a homogeneous, layered half-space model of the human breast and the polarization and frequency-response characteristics of generic tumor shapes. We conclude that the dynamic range of a sensor array comprised of such elements in conjunction with existing microwave equipment is adequate to detect small cancerous tumors usually missed by X-ray mammography.

FDTD analysis of a pulsed microwave confocal system for breast cancer detection

A novel focused active microwave system is investigated for detecting breast cancer. In contrast to x-ray and ultrasound modalities, the method reviewed here exploits the breast-tissue physical properties unique to the microwave spectrum, namely, the translucent nature of normal breast tissues and the high dielectric contrast between malignant and normal breast tissues. The system uses a confocal technique and time-gating to enhance the detection of malignant tumors while suppressing the effects of tissue heterogeneity and absorption. Using published data for the dielectric properties of normal and malignant breast tissues, we have conducted a preliminary 2-D finite-difference time-domain (FDTD) computational electromagnetics analysis of the system. We considered two types of inhomogeneities of normal tissue: a statistically random variation of the dielectric parameters throughout the breast in a /spl plusmn/10% range, and a spatially coherent inhomogeneity representing a vein. The modeled excitation was a pulsed 6-GHz waveform. The FDTD simulations showed that malignant tumors as small as 2 mm in diameter could be robustly detected in the presence of the background clutter generated by the heterogeneity of the surrounding normal tissue. Spatial resolution of the tumor location was found to be in the order of 1 cm.

The IITRI In Situ RF Fuel Recovery Process

AbstractIn this paper the history and current status of development of IITRI’s RF process for in situ oil shale/tar sand fuel extraction is described. A brief description of the salient features of IITRI’s RF process is given, together with a review of past laboratory development activities. The results of the recently completed 5 million dollar cooperative program, jointly funded by government and industry, are also described, including oil shale field tests, tar sand field tests, and supporting laboratory and analytical studies. Of special interest are the results of the latest tar sand field test wherein a 60-ton block of tar sand was heated in place to 200°C and nearly 30% of the in place tars were recovered in two weeks.

FDTD modeling of a coherent-addition antenna array for early-stage detection of breast cancer

A novel pulsed microwave confocal system for the detection of breast cancer has been proposed by Hagness, Taflove and Bridges (see Proc. of the IEEE Engineering in Medicine and Biology, Society Conference, p.2506-8, Chicago, IL, 1997). An elliptical reflector focuses a microwave signal at a potential tumor site and efficiently collects the backscattered energy by refocusing it at the point of origin of the illumination. This technology is based upon two fundamental dielectric properties of breast tissues at microwave frequencies: (1) the large contrast in /spl epsiv//sub r/ and /spl sigma/ between malignant and normal tissues, which causes tumors to have significantly greater microwave scattering cross sections than normal tissues of comparable geometry; and (2) the low attenuation in normal breast tissue (less than 4 dB/cm up to 10 GHz), which permits constructive addition of wideband backscattered returns using confocal-imaging techniques. We replace the fixed-focus elliptical reflector reported by Hagness et al. with a variable-focus antenna array and extend the range of breast tissue structures modeled to include small tumors obscured by veins and mammary glands and ducts.

2-D FDTD study of fixed-focus elliptical reflector system for breast cancer detection: frequency window for optimum operation

We have previously reported investigations of a novel pulsed confocal microwave system for detection of breast tumors (Hagness et al., 1997). In this paper, we extend this work by identifying a frequency window for optimum operation of the tumor detection system. The finite difference time-domain (FDTD) method is used to study a simplified 2-D breast-tissue geometry adjacent to an elliptical reflector antenna. First, power density results are presented to demonstrate the focusing abilities of the reflector antenna for sinusoid excitation at 3, 6 and 9 GHz. Second, a tumor located at the in-breast focus of the antenna is included in the geometry in order to observe the pulse response of the detector as a function of the tumor size at center frequencies of 3, G and 9 GHz.

Massive storage of wind power to reduce CO 2 emissions to produce wind-clean fuels

Wind power is being curtailed because large scale electrical energy storage systems are not available. However, a practical, large-scale, electro-thermal in situ energy storage system has been designed. Wind energy via the grid is transferred into unconventional oil deposits, such as the oil shale, tar sand or heavy oil deposits in the USA. This stored heat eventually converts the hydrocarbons into recoverable oil and gas products without generating CO2 emissions or needing much water. The energy in these wind clean fuels greatly exceeds the applied electrical energy. These wind-clean fuels can be used to offset use of foreign oil or to regenerate electrical power into back into the grid. The grid is stabilized by electronically controlling the system load. It can be used for smart grid functions. Fuel production can be sustained for over 100 years by the massive oil shale and tar sand deposits in the USA.

Three-dimensional FDTD analysis of an ultrawideband antenna-array element for confocal microwave imaging of nonpalpable breast tumors

We are developing a confocal microwave imaging system for the detection of early-stage breast cancer. Our proposed microwave sensor represents a novel adaptation and application of the principles of ultrawideband radar technology and confocal optical microscopy. The sensor is comprised of an electronically switched monostatic antenna array that, synthetically focuses a low-power pulsed microwave signal at a focal point within the breast and collects the backscattered signal. Malignant tumors have a significant scattering radar cross section due to the large dielectric contrast between malignant tumors and adjacent normal breast tissue. Therefore, the intensity of the backscattered signal increases dramatically when the focused transmitted signal encounters a malignant tumor. Two key performance specifications for the microwave sensor are the signal-to-clutter (S/C) ratio, defined as the ratio of the peak backscatter return from a tumor to the peak backscatter return from clutter, and the system dynamic range, defined as the ratio of the peak pulse power of the source to the system noise floor due to reverberations and thermal noise. Our two-dimensional FDTD simulations involving the computation of S/C ratios have demonstrated the feasibility of detecting lesions as small as 1 mm in diameter. In this paper, we highlight the results of our three-dimensional simulations of an antenna-array element placed at the surface of a breast tissue half-space.

Electrical Safety Concepts And Implementation

The cost-effective and safe design of electrical equipment depends on the reliability of data on electro-biological shock effects on humans. At present, these data are in the process of revision, yet some important aspects remain unresolved, and additional research is needed to address these issues. Once these are addressed, improved but less costly electrical shock safety methods, such as grounding or ground-fault current interruptors, can be implemented.