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Is It or Isn’t It Breast Cancer?

A new combination of technologies may help diagnose breast abnormalities with greater confidence

NIRS sends light through breast tissue and evaluates how light is absorbed and scattered by the tissue. This allows radiologists to see metabolic differences between normal tissue and malignant tissue.

The mammogram callback causes anxiety for most women. It happens when the radiologist sees something suspicious on a screening mammogram. Promising research at Norris Cotton Cancer could make follow-up diagnostic testing of the breast easier, faster, and more accurate.

Dartmouth engineers, researchers, and radiologists are refining a method to add near-infrared spectroscopy (NIRS) to breast MRI which is performed as a screening exam in high risk women and to stage women with known breast cancer.

"MRI picks up abnormalities which may not be cancer," said Roberta diFlorio-Alexander, MD, radiologist, Dartmouth-Hitchcock Medical Center. "Many abnormalities will be biopsied because they may look like cancer on an MRI."

Approximately two-thirds of biopsies performed for breast MRI abnormalities are benign.

Breast MRI becomes a more powerful diagnostic test
MRI NIRS breast

During the NIRS process, a woman lies on her stomach and the breast hangs through an opening in the table that contains a series of contacts and optic cables that send near infrared light through the breast.

By adding near-infrared spectroscopy to MRI, doctors can learn more about the abnormality's oxygen level, blood flow, and lipids. "With NIRS we get more out of the MRI," said Keith Paulsen, PhD, co-director of Cancer Imaging and Radiobiology Research Program.

Cells in a cancer tumor behave differently than normal cells. They grow rapidly, use more oxygen, have more blood flow, and use lipids as a fuel source. The MRI/NIRS can see when cells behave this way.

"An MRI offers exquisite anatomical detail and when we couple it with NIRS we can get functional information about breast tissue," said diFlorio-Alexander. "We can see metabolic differences between normal tissue and malignant tissue.

diFlorio-Alexander explains near-infrared spectroscopy as a way of sending light through breast tissue and evaluating how light is absorbed and scattered by the tissue.

Building a better machine to diagnose breast cancer: an engineering enigma

Outfitting an MRI machine with NIRS, however, is a difficult challenge that the biomedical engineers at Thayer School of Engineering at Dartmouth have been working on for more than a decade. For MRI/NIRS to be successfully used in routine patient care, the equipment must adapt to an individual's body size and accommodate a range of cup sizes. To transmit light it must maintain contact with the breast. Given the strength of the magnet in the MRI, it also cannot contain any metal.

Thayer School's prior designs for MRI/NIRS used parallel plates (similar to those in a mammogram), but that approach couldn't capture tissue close to the chest wall. This latest design uses a geometric approach. A woman lies on her stomach and the breast hangs through an opening in the table that contains a series of contacts. These contacts are connected to optic cables that send near infrared light through the breast and also act as receivers to detect the transmitted light that comes through the breast once it is illuminated.

Promising results after more than a decade of Dartmouth research

The new design offers increased coverage of the chest, giving providers improved visibility for "hard to see" areas, such as the outside area of the breast near the armpit.

diFlorio-Alexander said NIRS combined with mammography, breast ultrasound, and breast MRI holds great potential to improve the accuracy of breast imaging. "NIR-MR imaging has promising results for evaluating a patient's response to chemotherapy. Initial results suggest that combined NIRS-MR imaging may help to differentiate benign from malignant lesions in the breast and may one day allow us to improve screening in certain populations of women, such as women with dense breast tissue."

As a next step, Thayer engineers are working to make a non-fiber-detecting system to improve light coupling and detection. By placing optical detectors directly on the breast, they can improve sensitivity and accuracy of the test.

February 03, 2014