Originally Published MDDI September 2004
|The probe measures absorbed and reflected light to help determine the nature of tissue during a biopsy. (Inset) Although the probe is less than 1¼4–in. wide, researchers hope to make it even smaller and less invasive.|
Researchers in Wisconsin are developing a light-sensitive probe that could lead to more accurate detection of breast cancer. Missed diagnoses occur for as many as 70,000 U.S. women per year, and an additional 60,000 need a second biopsy because the first was inconclusive.
A team from the biomedical engineering department of the University of Wisconsin at Madison has developed a thin fiber-optic probe that can be threaded through the hollow channel of a biopsy needle to its tip. Used in conjunction with x-ray or ultrasound images, it could ensure that the biopsy needle reaches and samples the target area. The technology also has the potential to minimize trauma associated with the biopsy procedure.
Preliminary tests using ultraviolet-visible fluorescent light showed that the technology correctly identified cancer with more than 90% accuracy. A larger test, using both fluorescent and near-infrared light, has just begun on 250 patients. Results from the first test were published in the January issue of the Annals of Surgical Oncology.
Near-infrared light has been used with breast biopsies, but never in the body, while fluorescent light has been used inside the body to detect cancer, but never breast cancer. And neither has been used inside a biopsy needle. The test will help determine whether one approach is better than the other, or whether both can be used in conjunction, said Carmalyn Lubawy, a university biomedical engineering graduate student who is on the research team.
The probe works by emitting light at certain wavelengths and collecting the reflected light and fluorescence. The researchers analyze how much light is absorbed by the tissue and reemitted as fluorescence, and measure how much light is scattered. The absorption rate for tumors is different than that for other components of tissue. The team has also been able to reduce the number of light wavelengths needed to make a diagnosis, which should make the process more efficient.
The team, led by Nirmala Ramanujam, an assistant professor of biomedical engineering at the university, had been looking at a number of issues related to breast cancer and decided to tackle the inefficiencies of the biopsy process, Lubawy said.
The initial tests were done on tissue removed by lumpectomy. The current tests will determine whether the probe can work when used on a biopsy needle.
Designing the probe proved to be challenging, Lubawy said.“One obstacle is that biopsy needles have side apertures. Light has to go down the optical fibers and make a 90-degree turn so it can go into the tissue,” she said. “We couldn't get the direction right on the first biopsy needle we tried, so we had to change needles. We also had to work out problems with light leakage and signal levels. But we are confident that the design we have now will work.”
The probes are thin enough to fit through a needle smaller than the standard 1¼4-in. biopsy device, which could make the procedure less invasive. In fact, Lubawy said, the next step in development is to get the probe to work with even thinner needles. “This way [the procedure] removes less tissue and is less traumatic to the patient while maintaining high accuracy,” she said.
Initial funding for the project came from a Whitaker Foundation Biomedical Engineering Research Grant in 2001. The team has since won $1.2 million in grants from the National Cancer Institute and the National Institute of Biomedical Imaging and Bioengineering. The research team also includes radiologist Elizabeth Burnside and Wisconsin graduate student Changfang Zhu.
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