Cone-beam breast CT could revolutionize screening for breast cancer
Study shows significant progress for potentially powerful weapon
While the next generation of technology for breast cancer screening may well be based on digital breast tomosynthesis (DBT), there is another promising approach under development that also can produce three-dimensional images of the breast. Investigators in Texas and New York are reporting positive developments with respect to cone-beam breast CT (CBBCT), an approach that may be able to deliver certain advantages in terms of exam time, comfort, and diagnostic accuracy.
The latest findings regarding CBBCT come from a team of researchers from the University of Texas M.D. Anderson Cancer Center in Houston, TX. In tests, using a lab-based system to examine 12 mastectomy specimens, the researchers report that the detection of cancers based on morphologic assessment of tissue structures could potentially be improved over mammography because of the absence of overlapping glandular tissue.1 "This [technology offers] a true three-dimensional tomographic image acquisition of the breast that will permit post-processing and image manipulation in multiple different planes," explains Wei Tse Yang, MD, the lead author of the study and an associate professor of diagnostic radiology at M.D. Anderson.
Further, while DBT produces three-dimensional images as well, the images produced by CBBCT are of near isotropic resolution, according to Chris Shaw, PhD, a co-author of the study and a professor of imaging physics at M.D. Anderson. "Unlike tomosynthesis images, CBBCT images generally do not contain any reconstruction artifacts," Shaw says. "The artifacts, if present, are generally star-like and are related to metal clips or large calcifications…and can easily be distinguished from anatomy."
Radiation is not a concern
Until recently, concerns about radiation have kept CT from being considered for breast screening purposes, but researchers report that they have honed the technology to the point where CBBCT scans can be done with about the same level of radiation exposure as a typical mammogram.
John Neugebauer, general manager for U.S. operations for West Henrietta, NY-based Koning Corp., says, "It depends on the patient, it depends on the size of the breasts, and it depends on the density of the tissue, because you have to increase the radiation dose to penetrate denser tissue. So all of those factors being involved, we think we are probably in the same ballpark and maybe a little bit higher, but it is not going to be the kind of concern that is worth worrying about."
Koning is testing its first clinical CBBCT system at the University of Rochester Medical Center (URMC). Koning's system was developed by Ruola Ning, PhD, the founder of Koning and a professor at URMC's Radiology Department. It consists of a table where the patient lies down flat and places her breast in a hole. An X-ray tube then rotates around the breast at 360 degrees while generating several hundred pictures of the breast. A computer then reconstructs the pictures into a three-dimensional image, which enables a radiologist to examine the breast from every angle.
In early trials of the system, it has taken only about 10 seconds to image a breast. In addition, a significant advantage of CBBCT over mammography and DBT is that no compression of the breast is needed, making the examination much more comfortable for women. Further, while DBT may have an advantage in its ability to visualize tiny calcifications, CBBCT offers much higher contrast, so the hope is that the technology will be better able to detect early-stage cancer, even in dense breast tissue.
"We know we get more information in the picture…but how all of that is going to pan out, I am not sure, but that is the magic bullet," says Neugebauer. "One wants to penetrate those dense tissues that are hiding things in them."
Further research planned
Investigators, lead by Avice O'Connell, MD, MRCPI, the director of women's imaging and an associate professor of imaging sciences at URMC, have conducted a 60-patient pilot study comparing CBBCT to mammography and other technologies. A to-be-published paper demonstrates that the system allows adequate coverage of the breast tissue at radiation dose comparable to mammography and delivers equal or better image quality compared to mammography, Neugebauer says. The company plans to install a second CBBCT system at the Breast Imaging Center on the campus of Emory Hospital in Atlanta, and a third system is being installed at a second breast imaging center in Rochester, NY. The company then plans to have these high-volume centers participate in a clinical trial now under discussion with the Food and Drug Administration.
While the initial price of Koning's CBBCT system may be as high as $800,000, Neugebauer anticipates that costs will come down substantially with higher production levels. "After we get the first unit introduced for diagnostic purposes, we are really planning on doing a total cost revision and structural revision to get [the system] to a range where people would use it for screening," says Neugebauer, pointing out that the price of a full-field digital mammography system is in the $350,000 range.
Further research into CBBCT is also planned by the Texas researchers. "We are planning detailed reader studies on mastectomy specimens to assess detection of soft tissue masses, calcifications, and reproducibility of results amongst different readers," explains Yang. "There is hope and excitement that CBBCT will have the potential to be of use in screening for breast cancer and in monitoring response to therapy for breast cancer. However, results are currently extremely preliminary."
Reference
- Yang WT, Carkaci S, Chen L, et al. Dedicated cone-beam breast CT: feasibility study with surgical mastectomy specimens. Amer J Roentgen 2007; 189:1,312-1,315.
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