Home : Volume 25 : Spring 1999 :
Special `radar' could be next big tool for early breast cancer detection

Locating buried landmines can be a matter of life or death for military personnel. That's why scientists are researching ways of sending microwave pulses into the ground and forming "pictures" with the signals that bounce back.

Some day in the not-too-distant future, medical workers may be able to apply a similar approach to finding a sort of biological landmine -- the breast cancer tumor.

Assistant Professor Susan C. Hagness (left) and WARF Graduate Fellowship student Xu Li examine results of "breast tumor radar." (18K JPG)

Assistant Professor Susan C. Hagness of the Department of Electrical and Computer Engineering is hard at work on this project, designing what she informally refers to as "a breast tumor radar." This instrument would offer several benefits over traditional mammography, explains Hagness: "It has the potential to detect tumors that are invisible to X-rays, eliminate patient exposure to X-rays, and prevent the need for uncomfortable breast compressions associated with X-ray mammography."

In traditional X-ray mammography, a breast image is created by passing high-energy ionizing radiation all the way through a highly compressed breast to expose film on the other side. Though this tumor screening process has warned thousands of women of life-threatening situations, it is far from perfect, notes Hagness. According to the National Cancer Institute, X-ray mammograms miss between 10 and 30 percent of malignant tumors, and many of the suspicious masses they do detect turn out to be benign.

A microwave radar image of a computer-generated breast tissue phantom containing a 0.5-cm-diameter malignant tumor. The image is formed by sending microwave pulses into the breast and processing the echoes--the signals that the tumor sends back to the antenna-array sensor. (12K JPG)

Through the use of highly sensitive microwave detection, malignant tumors might be detected much earlier, says Hagness. "And the anticipated low cost and painless application could make it useful for routine screening." Detailed computer simulations and tests of a laboratory-demonstration sensor suggest that the microwave technology may also help to discriminate malignant from benign tumors, thereby reducing the number of unnecessary surgical biopsies.

Hagness is collaborating with other UW faculty, researchers at Northwestern University, and the staff of the Chicago-area company Interstitial to investigate this new breast imaging modality. Jack Bridges, chairman of Interstitial, explains that microwaves interact with human tissues primarily according to water content. "Since malignant tumors have a much higher water content than normal breast tissue, microwaves can provide the basis for a highly sensitive detection system," he says. "Once we had these key concepts, the technology began to develop very rapidly," says Hagness, who received her PhD from Northwestern in June 1998. She has conducted extensive computational simulations of the microwave sensor using supercomputer time, courtesy of Cray Research, Inc.

"On the Cray supercomputers, we are able to simulate embedding a tumor within randomly oriented veins and mammary ducts and lobes in the breast," says Hagness. "The ability of the microwave sensor to detect small tumors appears to be unaffected by natural variations in the breast tissues."

A complete microwave tumor-detection system will consist of a sensor and a computer processor. The microwave sensor will be a small flat panel containing an array of miniature antennas placed on the surface of the breast. "Instead of compressing the breast between two plates, the microwave antenna array will gently rest flat against the breast, much as a book would if you were lying in bed," says Hagness.

The device has been successfully tested on a "phantom" -- a simulated breast consisting of materials that share key microwave properties of normal breast tissues. A tiny simulated tumor was embedded within the breast phantom and was located using the microwave sensor. Phantoms are well-established proving grounds for new techniques and are used for routine calibration of existing mammography equipment.

One of the next steps, says Hagness, will be conducting measurements on breast material removed through biopsies at the UW Hospitals and Clinics. She is beginning this work with Assistant Professor Steven S. Gearhart (electrical and computer engineering) and Associate Professor Frederick Kelcz (radiology).

Research team members are also creating a database of different breast types, based on anatomical data from MRI scans, for computer simulations that test the microwave sensor in a realistic tissue environment. Hagness is working with Bridges and his staff at Interstitial to develop a prototype system for pre-clinical tests.

Content by perspective@engr.wisc.edu

Date last modified: Tuesday, 06-Apr-1999 12:00:00 CDT

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