Digital mammography has become common in hospitals only recently, but already it is having a positive effect on early detection of breast cancer, particularly compared to traditional film imaging.
"Studies have suggested that approximately 10 percent to 20 percent of breast cancers that were detected by breast self-examination or physical examination are not visible on film mammography," according to a report by the National Cancer Institute (NCI). "A major limitation of film mammography is the film itself. Once a film mammogram is obtained, it cannot be significantly altered; if the film is underexposed, for example, contrast is lost and cannot be regained."
Digital mammography is much more flexible. "The image of the breast is recorded electronically and can be displayed immediately on a monitor," says Dr. Mary Beth Lobrano, a radiologist at East Jefferson General Hospital (EJGH). "With traditional film-screen mammograms, the films are exposed then developed in a processor and hung on a light box to be read. This faster, more efficient process (digital) allows us to image more patients per day in the Breast Care Center. It also helps us do invasive procedures (like needle localizations prior to breast surgery and ductograms) much more quickly, which I know our patients appreciate."
Most important is the difference digital mammography has made in doctors' ability to detect abnormalities. A study published in Radiology in 2007 concluded that full-field digital mammography (FFDM) detected instances of cancer at an increased rate when compared to screen-film mammography. Similarly, results from a clinical trial comparing the two methods published in the October 2009 American Journal of Roentgenology concluded: "The cancer detection rate for FFDM was higher than screen-filming mammography for initial screening and subsequent screening, for invasive cancer and ductal carcinoma in situ [a noninvasive condition], and across all age groups."
Lobrano attributes these results in part to improved contrast resolution of digital mammography and the fact that radiologists now have more flexibility in the way they can manipulate the images. On a computer, for instance, an image can be magnified, converted, the levels can be adjusted, etc. "This helps us pick out subtle abnormalities that might not otherwise be visible, which ultimately leads to the detection of more breast cancers at earlier stages," Lobrano says.
Another facet of the technology that contributes to the improved effectiveness of digital mammography is the way in which the digital format works with Computer Assisted Detection (CAD) programs — which, in this case, essentially double-check the images for irregularities, assisting specialists in determining how to proceed.
"CAD will circle a potential problem area on screen," explains Dawn Hymel, a supervisor at EJGH's Breast Care Center. "At that point, we can decide to take more views and angles, whereas before, it might be harder to detect."
Digital mammography software further assists health professionals. "Studies have shown that the use of CAD improves detection of breast cancers," Lobrano says. "Digital technology also means that mammograms are available on a Web-based viewer for multiple physicians to review simultaneously. This is particularly helpful if multiple specialists are involved in the care of a patient and need to review the films prior to treatment."
Digital mammography also means there no longer is just one set of films that could get lost or damaged. Electronic images can be duplicated with the same level of quality as the originals — as many times as needed. "This is particularly important in our part of the world," Lobrano says. "As a result of Hurricane Katrina (and flooding from the levee failures), many traditional mammogram films stored in local imaging centers or hospitals were destroyed. Having electronic, Web-based storage of mammograms protects our patients' images from being destroyed in a hurricane, flood or other natural disaster."
Even without the threat of natural disaster, hospitals should add the technology to their cancer-fighting tools because of its efficacy. Breast cancer is the second-leading cause of cancer-related deaths in the United States and the second most common type of cancer found in women (after skin cancer), according to the NIC. Deaths from breast cancer have been on the decline since the early 1990s, an improvement attributed to early detection and better treatments. Digital mammography can improve early detection and continue the decrease in the number of breast cancer deaths.