Wearable Millimeter-Wave Device for Contactless Measurement of Arterial Pulses.

Wearable monitors for measuring vital signs such as blood pressure will greatly impact the medical field. This work presents a millimeter-wave, radar-based system for performing accurate measurements of arterial pulse waveforms without contacting the region that is pulsing. Electromagnetic and radar-system simulation models are utilized to demonstrate the viability and safety of this approach. This is followed by hardware/software implementation and a study on 12 human subjects. Measured radial arterial waveforms exhibit signal strengths that are well above the noise floor of the system and a morphology that would be expected in an arterial pulse. Finally, comparison of the radar-based signals with a reference tonometer indicates a strong correlation between waveforms, as well as similar spectral signatures. The results observed suggest a millimeter-wave based approach for arterial pulse detection is very promising for future applications in pulse wave analysis and pulse transit time measurement for blood pressure tracking.

Microwave thermolysis of sweat glands.

BACKGROUND AND OBJECTIVES: Hyperhidrosis is a condition that affects a large percentage of the population and has a significant impact on peoples' lives. This report presents a technical overview of a new noninvasive, microwave-based device for creating thermolysis of sweat glands. The fundamental principles of operation of the device are presented, as well as the design and optimization of the device to target the region where the sweat glands reside. MATERIALS AND METHODS: An applicator was designed that consists of an array of four waveguide antennas, a cooling system, and a vacuum acquisition system. Initially, the performance of the antenna array was optimized via computer simulation such that microwave absorption was maximized near the dermal/hypodermal interface. Subsequently, hardware was implemented and utilized in pre-clinical testing on a porcine model to optimize the thermal performance and analyze the ability of the system to create thermally affected zones of varying size yet centered on the target region. RESULTS: Computer simulation results demonstrated absorption profiles at a frequency of 5.8 GHz that had low amounts of absorption at the epidermis and maximal absorption at the dermal/hypodermal interface. The targeted zone was shown to be largely independent of skin thickness. Gross pathological and histological response from pre-clinical testing demonstrated the ability to generate thermally affected zones in the desired target region while providing protection to the upper skin layers. CONCLUSIONS: The results demonstrate that microwave technology is well suited for targeting sweat glands while allowing for protection of both the upper skin layers and the structures beneath the subcutaneous fat. Promising initial results from simulation and pre-clinical testing demonstrate the potential of the device as a noninvasive solution for sweat gland thermolysis.

Advances in the 3-D forward-backward time-stepping (FBTS) inverse scattering technique for breast cancer detection.

This paper presents recent advances in a 3-D inverse scattering technique, called forward-backward time-stepping (FBTS), applied to the reconstruction of the microwave properties of the breast. The FBTS algorithm is utilized for a numerical-based study of a 3-D breast model based on an MRI. Several illumination schemes, based on different microwave transmitter/receiver configurations, are compared based on the quality of the reconstructed images of the breast model. A combination of cylindrical and planar arrays is shown to provide accurate estimates of the model electrical parameters that delineate the various regions of the breast. Although further analysis with this combination array demonstrates that tumors of reduced size and reduced contrast with the surrounding fibroglandular region are much more difficult (and in some cases not possible) to reconstruct, the study presents some promising initial results of a reconstruction technique for breast imaging and cancer detection.

Two-dimensional time-domain inverse scattering for quantitative analysis of breast composition.

Forward-backward time-stepping is a unique approach for solving electromagnetic inverse scattering problems in the time domain. In this paper, the technique is applied to a realistic, heterogeneous breast model. The ability to detect a 5-mm diameter malignancy and provide substantial quantitative information about the breast's composition is demonstrated.

Automatic temperature controller for multielement array hyperthermia systems.

This paper concerns the optimization and performance analysis of an automatic control algorithm for managing power output of large multielement array hyperthermia applicators. Simulation and corresponding measurement of controller performance in a solid tissue equivalent phantom model is utilized for analysis of controller response to dynamically varying thermal load conditions that simulate clinical treatments. The analysis leads to an optimum controller which demonstrates the ability to achieve a uniform and stable temperature profile over a large surface area regardless of surrounding thermal load. This paper presents several advancements to the performance of a previously published control routine, including: 1) simplified simulation techniques for thorough characterization of controller performance; 2) an optimization procedure leading to an improved hybrid control algorithm for maintaining optimal performance during periods of both "rising" and "steady-state" temperature; 3) performance analysis of a control algorithm tailored for large area hyperthermia treatments with a mulitelement array applicator. The optimized hybrid controller is applied to the conformal microwave array (CMA) hyperthermia system previously developed for heating large area surface disease such as diffuse chestwall recurrence of breast carcinoma, and shown to produce stable, uniform temperatures under the multielement array applicator for all thermal load conditions.