Technological Advances Improve Mammography Speed and Accuracy
Recent studies of cone-beam CT in breast imaging and a new type of computed radiography (CR) offer the promise of faster, safer and potentially more accurate mammography.
 Wei-Tse Yang, M.D. The University of Texas M.D. Anderson Cancer Center |  Rick Lubinsky, Ph.D. Stony Brook University |
Cone-Beam CT Offers Excellent Contrast with Reduced Exam Time
Researchers at The University of Texas M.D. Anderson Cancer Center in Houston investigated the feasibility of diagnostic breast imaging using a flat-panel detector CT system.
Using cone-beam CT on 12 mastectomy specimens, the researchers found that the images have exceptional tissue contrast and can potentially reduce examination time with comparable radiation dose. Results of the study were published in the December 2007 issue of the American Journal of Roentgenology.
"It is an extremely new and exciting technique," said lead author Wei-Tse Yang, M.D., an associate professor of radiology and chief of the Breast Imaging Section. Cone-beam CT breast imaging is different than the technique used for whole-body CT, she said.
"Instead of the patient moving through a gantry—which is what happens in routine CT of the chest, abdomen and pelvis—the cone-beam CT device makes a single rotation around the breast," she said. "We can keep the radiation dose down and the study can be completed in a very short time, within 17 seconds."
Dr. Yang added that cone-beam CT eliminates the compression associated with routine mammography, which is at best uncomfortable but can be painful for some women.
With cone-beam CT, the patient lies prone with the breast in a dependent position through a gap in the table. The position is somewhat similar to that of MR breast imaging, however the 17-second acquisition time is a huge advantage over the 30 and 40 minutes MR requires. "If you're looking at someone elderly or with a pre-morbid medical condition, it might be difficult to stay still for 40 minutes," said Dr. Yang. "That has an adverse impact on image quality."
Dr. Yang, Chris Shaw, Ph.D., a professor of Medical Physics at The University of Texas M.D. Anderson Cancer Center and colleagues also found that structured noise on cone-beam CT was minimal due to the absence of overlapping tissue. Breast anatomy was well resolved and microcalcifications within cancers clearly shown.
"Cone-beam CT has significant potential advantages," Dr. Yang said. "I think it's something that's going to be very attractive and therefore, the onus is on investigators to prove equivalence and down the line, objective benefit as compared to conventional breast imaging methods."
CR System Affordably Improves Resolution
A transparent glass-ceramic plate that could make CR mammography more detailed and less expensive is the centerpiece of a new storage phosphor CR system developed by U.S. and German scientists.
"The use of such a screen with storage phosphor-based CR is not a new idea," said Rick Lubinsky, Ph.D., an assistant professor of research radiology at Stony Brook University in Stony Brook, N.Y. "It's more like something people have been wishing they could do for many years."
Dr. Lubinsky collaborated with materials scientist Jacqueline A. Johnson, Ph.D., of Argonne National Laboratory near Chicago and Stefan Schweizer, Ph.D., of the University of Paderborn, Germany, to develop the ultra-high resolution mammography system.
"I think the edge that we have is in resolution," said Dr. Johnson, who holds a joint appointment with the University of Tennessee Space Institute. "The reason is that our plate is transparent."
Dr. Lubinsky explained how the system differs from conventional mammography. "In film screen or even nowadays with digital radiography based on phosphors, X-rays enter the breast, encounter the phosphors, make light and the light scatters around before either going to an electronic detector or exposing the film," he said. "As a result, you get the scattering or spreading of the light, which translates into a blurred image and loss of resolution.
"In the transparent material, X-rays are absorbed and a stored image is created, then you come along with a laser and read that stored image out," Dr. Lubinsky continued. "There is no light scattering, so the spatial resolution is extremely high."
Early tests produced resolution down to 17 microns, said Dr. Johnson, adding that the system is also a lot less costly than current technology.
"It's just a piece of glass, so it can be any shape or size," she said. "The real top-notch mammography systems right now are selenium. Selenium has a resolution of about 70 microns, but it's very expensive because each plate requires a dedicated readout. Ours does not. Our system is a storage phosphor, so physicians can retrofit what they have already in a film screen device and need just one readout system."
The researchers recently received a grant from the National Institutes of Health (NIH) to continue the project. "We're going to scale up this plate and maximize its properties to be better than it is now," said Dr. Johnson.
"What I'll do is build a little laser scanner in which we can test these materials and learn things that we need to learn in order to make a full-scale, clinical prototype system," Dr. Lubinsky added.
The researchers estimated it could be more than five years before the technology is ready for clinical use. They hope the system will eventually prove attractive to smaller hospitals and radiology groups that cannot afford more costly digital radiography systems.
"What we're hoping to come up with is a system that not only achieves really high-resolution radiographic image quality, but also does so in an inexpensive way," said Dr. Lubinsky.
