EMBARGOED UNTIL 5 p.m., OCTOBER 30, 1997
Contact: Kara Villamil, or Mona S. Rowe
UPTON, NY Tomorrow's mammograms could be much more effective at spotting extremely small and elusive breast cancers, thanks to a new X-ray imaging method developed at the U.S. Department of Energy's Brookhaven National Laboratory.
The technique, which uses ultra-brilliant X-rays, is described in a paper published today in the November issue of Physics in Medicine and Biology by scientists from BNL, the Illinois Institute of Technology, North Carolina State University and the University of North Carolina. It was pioneered at BNL's National Synchrotron Light Source (NSLS) facility.
"This work wouldn't have been possible without the intense, tunable X-rays produced by the NSLS," said BNL Physicist William Thomlinson. "Now, the challenge is to take it from today's experimental stage to future use in mammography, and other medical and materials imaging as well."
Both at the NSLS and in recent tests at the Advanced Photon Source at Argonne National Laboratory, the scientists showed that their technique creates a dramatic contrast between normal tissue and tumors, an important accomplishment for mammography. They have named it diffraction-enhanced imaging, or DEI.
"This development offers new hope for early detection of breast cancer," said Secretary of Energy Federico Peña. "I congratulate the team behind this accomplishment, and am pleased that the DOE's national laboratories are helping make such progress in combatting this disease."
"Mammography presents very difficult imaging problems because of the density of the tissues which often hide tumors," says team member Dr. Etta Pisano, chief of mammography in the department of radiology at the UNC. "With our method, we have produced images showing improved detail of cancerous tumors in human breast tissue. The detail is outstanding."
In conventional mammograms, differences in tissue
densities and composition show up as contrasting areas due to X-ray absorption,
allowing doctors to see tumors or changes in tissue. The problem is that
differences between healthy and cancerous tissues are very small and scattering
of X-rays can lead to blurring and even lower contrast, making it difficult
to detect small tumors. The recent DEI tests showed up to 25 times better
contrast than normal in a quality-control phantom.
The DEI method uses a single-energy (monochromatic) fan beam of X-rays instead of the broad-energy beam used in conventional imaging. The object is scanned through the beam. The key to the new imaging method is an analyzer crystal placed between the object and the X-ray detector. The analyzer can differentiate between X-rays that are traveling much less than one ten thousandth of a degree apart. "That's about the size an ant would appear if you were looking at it from a mile away," said BNL Physicist Zhong Zhong.
"This method of line scan imaging reduces
scatter and helps us visualize low-contrast areas that otherwise would be
lost," explained Dean Chapman, director of Illinois Institute of Technology's
(IIT) Center for Synchrotron Radiation Research and Instrumentation.
Two Images from One Scan
DEI produces two images: one that shows how the X-rays were refracted, or bent, as they passed through the object; and one that shows how much the X-rays were absorbed by the object as they passed through.
The first, or refraction, image highlights the edges of structures in the object. Objects that have very little absorption contrast may have strong refraction properties, which this image will highlight. An example is the fine, thread-like fibers that characterize some malignant tumors. Normally difficult to see using conventional radiography, they are clearly visible in the refraction image.
The second DEI image, the apparent absorption image,
is similar in appearance to a normal radiograph of the object but shows
improved contrast. "Since the analyzer rejects X-rays that are scattered
through small angles by various types of tissues, this method is sensitive
to tissue structure," explained Thomlinson.
A Roadmap for Future Research
For the paper, the team of scientists demonstrated their technique's capability at BNL's NSLS using a "phantom" breast model, created by the American College of Radiology for quality control in mammography. More recently, their preliminary results from studies of actual human breast tissue at Argonne's APS showed higher contrast than conventional images. They also show that the technique works equally well at the X-ray energy used in conventional mammography and at a higher energy level, although the higher energy X-rays caused a lower radiation dose to the breast tissue.
The researchers say their DEI method could be used in experimental clinical trials within five years and possibly in routine mammography in 10 years. In addition to mammography, potential applications of DEI include other low contrast tissues and organs such as kidneys, and in non-destructive testing of materials.
To continue this research, the team has established its own station at the NSLS, on the beam line called X15A. The beam line will provide the necessary experimental time to advance the technology over the next two years or more.
The authors of the paper, titled "Diffraction Enhanced X-ray Imaging," are BNL's Thomlinson, Zhong Zhong, Fulvia Arfelli, Nicholas Gmur and Ralf Menk; IIT's Chapman; Dale Sayers of the physics department at North Carolina State University; and Eugene Johnston, David Washburn, and Pisano, all of the department of radiology at the University of North Carolina.
Brookhaven National Laboratory carries out basic
and applied research in the physical, biomedical and environmental sciences
and in selected energy technologies. BNL is operated by Associated Universities,
Inc., a nonprofit research management organization, under contract with
the U.S. Department of Energy.
These three images of human breast tissue were taken using 18 KeV X-rays at the Advanced Photon Source at Argonne National Laboratory. The first is comparable to a conventional mammogram. The second and third were taken using the DEI method developed by scientists from Brookhaven National Laboratory, Illinois Institute of Technology, the University of North Carolina and North Carolina State University. Note the dramatic increase in contrast between the conventional and DEI images.
The BNL participants in the DEI research
team at the
National Synchrotron Light Source experimental station where future
development of the technique will be performed: (from left)
Nicholas Gmur, Zhong Zhong, and William Thomlinson.