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New Light on Breast Cancer

Laser light and thermal heat could help improve the accuracy of mammograms
computed tomography laser mammography scan



IMAGING DIAGNOSTIC SYSTEMS, INC.
In a quiet exam room, Susan Conlan, 50, prepared for the mammogram that would help confirm whether her breast cancer had returned. She untied her robe, positioned herself on the machine and moved her arms out of the way. Ordinarily this is when a woman would begin to cringe--the moment before her breast is smashed onto a cold x-ray platform. But Conlan never felt a thing.

"I was extremely comfortable," Conlan recalls.

Conlan is one of the first patients in the country to test a gentler, radiation-free breast-imaging method called CT (computed tomography) Laser Mammography (CTLM). CTLM, developed by Florida-based Imaging Diagnostic Systems, Inc., is one of several experimental technologies (see sidebar) aimed at improving the accuracy of breast imaging, especially in distinguishing benign breast conditions from breast cancer. Like CTLM, another method, Computerized Thermal Imaging (CTI), also scans the tissue for the temperature differences that might indicate a growing tumor. Recent concerns over the sensitivity of standard x-ray mammography images and the competency of the human readers have underscored the need for better tests.

"Approximately 10 to 20 percent of the time, a mammogram is read negative when a breast cancer is present," says Susan Curry, a radiologist at the Women's Center for Radiology Orlando.

X-ray mammograms are recorded onto large, flat sheets of black-and-white photographic film. Because the anatomical images vary tremendously from woman to woman, they are difficult to read. What may be considered normal for one patient could indicate a need for concern for another. In addition, some breast changes are just too subtle to recognize. "When I had my cancer, the lump did not show on the mammogram," Conlan notes.

In Living Color

CTLM gives radiologists a colorful 3-D cross-sectional view of each breast. The bright green and white globes conjure the image of a lime Jell-O salad filled with fruit.

"We can look through the breast from the front, the side, the back and all the way through," explains Eric Milne, chief radiologist for Imaging Diagnostic Systems, Inc. The company is currently seeking approval by the U.S. Food and Drug Administration (FDA) as an adjunct to mammography. It plans to eventually push for the technique's use as a screening tool.

During an exam, a patient lies face down and suspends one breast through a hole in the table. Inside the console, a low-wavelength laser sweeps around the entire breast, a process that can take up to 15 minutes depending on breast size. The system calculates how the light is absorbed and uses the information to create an image. For some smaller-breasted women, it may be more difficult to make an image of the breast with this technique, as with mammograms, because they can't get as much tissue into the machine.

This physiological approach is based on the theory that malignant tumors sprout new blood vessels, a process called angiogenesis. Hemoglobin in the blood absorbs the CTLM laser light much more than surrounding tissue. The more blood flow, the whiter the image. The trick is deciphering which blood vessels are normal and which are not. Ordinary blood vessels in the breast tend to reveal themselves in a bicycle-spoke-like pattern.

While Milne declined to quantify how much the laser-based technique might improve the detection of breast cancer, he did say that the "incidence of false positives is much lower than that of mammography."

The CTLM test, which is expected to cost patients about $150, revealed that Conlan's most recent lump was much larger than x-rays indicated, prompting her doctor to recommend a biopsy.

Cutting Back on Biopsies

Millions of dollars are spent each year on breast biopsies, the majority of which reveal that nothing is wrong. Experts say more informative imaging could dramatically reduce the number of unnecessary procedures.

"If we can say with 100-percent accuracy that 20 to 30 percent of these [cases] shouldn't go to biopsy, we save some money and save some patients from needless worry," says Yuri Parisky, director of breast-imaging services at the USC/Norris Comprehensive Cancer Center in Los Angeles.

Parisky is leading a multi-institutional study to determine if thermal imaging could help radiologists observe questionable mammogram abnormalities with greater clarity. The painless 10-minute CTI exam is similar to the CTLM approach in theory and patient preparation. A woman lies on the same type of table with a breast suspended through a center ring. But instead of laser light, CTI uses mirrors and a sensitive thermal camera to capture the heat emitted by the breast. Cool air is circulated around the breast, lowering the local body temperature and causing blood vessels to constrict. Malignant tissue has increased blood flow, so it constricts less than normal. That means the tissue stays "hot" and emits a strong thermal signature.

"In mammography, we use radiation that comes out of a machine and goes into a patient. This imaging involves only the heat or energy coming off the patient," explains Robert Hamm, director of breast imaging at Providence Hospital in Washington, D.C.

Highlighting Areas of Concern

The FDA is now considering CTI as an adjunct to mammography; a review panel is expected to meet in October. Lake Oswego, Oregon-based CTI, Inc., emphasizes that the technique is not intended as a substitute for mammography. Because the thermal differences displayed by the CTI system are so minute, the naked eye cannot discern between malignant and benign lesions. Instead, the radiologist uses the patient's mammogram as a guide to identify the area of concern. The CTI system then calculates the likelihood of cancer. "I don't think this is a technology that will be rejected," Parisky says. "Radiologists have long tried to meld anatomic and physiological images. That's just what we've done."

But not everyone boasts the same enthusiasm. The idea of breast thermography dates to the 1970s, and has long been viewed with skepticism. Previous research attempts using heat as a screening tool failed miserably.

"I am quite skeptical about the usefulness based on the dismal experiences with the original thermography studies," says Kathryn Evers, director of mammography at the Fox Chase Cancer Center in Philadelphia.

Parisky says that researchers have overcome that obstacle with equipment that is much more sensitive to heat variation. "I think this opens up a whole new field, now that we have more sophisticated infrared cameras and computers," she adds.

Tonya Powell, 37, volunteered for the CTI procedure after a physical exam revealed a suspicious lump. She wanted to avoid a biopsy or any other invasive breast procedure. "My mother had microcalcifications detected on a mammogram for which she underwent a breast biopsy, which was negative," she recalls.

Powell's thermal scan, when compared with her mammogram, indicated that there was nothing to worry about. Her doctor has advised her to perform routine breast exams. "I have a lot of confidence in the accuracy of the procedure," Powell says.

Milne and Evers suggest that patients ask their physician whether or not a particular test is reasonable. Experts say patients will find the most reliable information concerning the newest technologies at a large university medical center or dedicated cancer hospital.


Kelli A. Miller is a science and medical writer based in Atlanta. She runs NewScience, Inc., and works as executive producer for NewsProNet's Discoveries & Breakthroughs Inside Science TV news service.


Articles from "What You Should Know About Cancer," a September 1996 Scientific American special issue, are available for purchase from the Scientific American Archive.
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