|Session:||Session 1A2 - Invited Papers (01b)|
|Date:||Monday, November 06, 2006|
|Time:||11:00 - 12:30|
Ultrawideband Microwave Radar Detection of Breast Cancer:
Challenges and Opportunities
University of Wisconsin-Madison, UNITED STATES
Detecting early-stage breast cancer with high sensitivity and specificity has proven to be a challenging problem for existing clinical modalities. Interest in the development of ultrawideband (UWB) microwave breast cancer detection techniques has grown rapidly over the past decade for a number of reasons. Dielectric spectroscopy studies have suggested that the dielectric-properties contrast between normal fatty breast tissue and malignant tumors is significant over much of the non-ionizing electromagnetic spectrum. The microwave frequency regime has drawn much attention in part because it strikes a balance between the competing demands of penetration depth and imaging resolution. The promise of a screening technology that is low in cost and harmless to the patient has also helped to fuel ongoing research.
An UWB microwave radar approach to breast cancer detection involves transmitting low-power UWB signals from each antenna in an array surrounding the breast. The scattered signals are recorded and processed by a series of preimaging algorithms to identify the location of the surface of the breast, estimate the patient-specific average dielectric properties of the interior breast volume, eliminate the unwanted reflection from the skin interface, and mitigate the effects of clutter generated by the heterogeneous mixture of fatty and fibroglandular tissue in the breast. Signal processing techniques such as beamforming, hypothesis testing, or time-reversal imaging can then be applied to the space-time scattered signals to detect and localize malignant tumors in the breast. UWB imaging can also exploit morphology-dependent characteristics such as spectral and polarization signatures for the purpose of discriminating between malignant and benign lesions.
Promising results have been obtained to date with anatomically realistic numerical phantoms as well as experimental laboratory phantoms of varying complexity in conjunction with compact UWB antennas and microwave reflectometers. However, numerous challenges need to be overcome in order to fulfill the promise of microwave breast imaging in a clinical setting. In this talk, I will review theoretical and experimental progress in this field and address the challenges and opportunities for establishing UWB microwave radar imaging as a clinically relevant tool for breast cancer detection.
Near-Field Technology - An Emerging RF Discipline
The Q-Track Corporation, UNITED STATES
An amazing and often overlooked world of RF phenomena lies within about a half wavelength of an electrically small antenna. This realm is known as the "near-field zone." The near-field zone is usually neglected by RF scientists and engineers because typical RF links operate at distances of many wavelengths where near-field effects are utterly insignificant. "Near-field" means different things in different contexts, and requires some explanation. This paper will begin with a history of the near-field from Faraday to the present day. Engineers put the discoveries of Michael Faraday and Joseph Henry to practical use in motors and generators. As technology progressed near-field wireless was largely ignored in favor of far field wireless. Now with rapidly growing demands for short range wireless links, near-field wireless is emerging as the best solution to a variety of significant problems. This paper will also explore the ways in which a variety of companies are exploring using near-field systems for communications and positioning. Aura Communications was formed in 1995 to exploit near-field behavior in the context of short range communication systems including wireless hands-free ear pieces and head phones.Sony, Nokia, and Phillips teamed to form the Near-Field Communication Forum (NFC), to promote this technology. In 2003, a global standard for near-field communication was adopted. The burgeoning area of RFID technology exploits nearfield physics to enable short-range, low-cost tags with the potential to revolutionize supply-chain management and inventory control. With the recent adoption by WalMart and other large retailers of RFID technology, this alone promises to be a $5 billion industry by 2007. Near-field behavior is also the foundation for a breakthrough in wireless tracking and positioning pioneered by the Q-Track Corporation. "Near-field electromagnetic ranging" or NFERTM technology allows for positioning with an accuracy approaching one foot at ranges up to 200 feet or more, even in complicated indoor propagation environments. The emerging near-field industry is poised for explosive growth, but places unique demands on antenna (or sensor) technology. Near-field sensors and tags are generally not characterized with respect to gain, so there is no way for engineers to mathematically define or evaluate a link equation. The near-field industry relies on trialand- error and empirical approaches to antenna design. There is a significant disconnect between theory and practice which means there are similarly significant opportunities for engineers and scientists in both industry and academia. The aim of this talk is to make engineers and scientists aware of the many opportunities available to advance the state-of-the-art of near field technology while the field is still in its infancy.