Computer-aided detection (CAD) shows great promise for assisting radiologists as they analyze images to detect cancers of the breast, lung and colon. A CAD algorithm highlights and marks suspicious regions, which steers the radiologist to review a spot that may be overlooked during the initial analysis. In theory, CAD boosts cancer detection rates. This month, Health Imaging & IT asks how CAD pans out in practice.
Breast CAD, which first earned Food and Drug Administration approval in the summer of 1998, is the most mature technology and available for both analog and digital mammography. Lung CAD comes in two flavors-x-ray and CT-based solutions. CAD systems for lung x-rays circle suspicious nodules on the classic chest film, while CAD systems examining CT images aid radiologists by marking suspicious areas and completing automatic measurements as they navigate through the tremendous volume of data generated by a chest CT. The newest CAD option - colon CAD - is based on a similar premise. That is, CAD helps the radiologist sort through the volume of data acquired during CT colonography and by placing marks on suspicious areas.
Breast CAD: Tried & true
Breast CAD is a winner. With fewer breast imaging centers and radiologists to practice mammography over the last several years, as well as high malpractice rates, breast CAD lends mammographers a helping hand with great skill. "CAD certainly helps radiologists diagnose more cancers. All studies across the board from private practices to academic medical centers to experienced and novice mammographers demonstrate that CAD helps find cancers earlier and better," sums Rachel Brem, MD, director of breast imaging and interventional center at George Washington University Medical center (Washington, D.C.). Brem and her colleagues rely on iCAD's SecondLook CAD solution to analyze both analog and digital mammography images.
|Mapping Your CAD Options|
CAD Sciences: Breast and prostate MRI
Cedara: Breast ultrasound
Confirma: Breast MRI
EDDA Technology: Digital chest radiographs and liver CT*
iCAD: Film-based and digital mammography, CT lung*, CT colon
iMED: Colon CT
Median Technologies: Lung CT and colon CT
Medicsight: Lung CT and colon CT
Neurognostics: Functional MRI
R2 Technology: Film-based mammography, digital mammography and lung CT
Riverain Medical: Analog chest radiographs
Siemens Medical Solutions: Echocardiography*, lung CT*, colon CT* and digital mammography*
*Not yet available for sale in the U.S.
Multiple clinical studies link the use of CAD with an increase in the breast cancer detection rate. Increases range from just over 6 percent to nearly 20 percent depending on the study and setting - with the average increase in the 15 percent range. For example, a two-year prospective study published in the American Journal of Roentgenology in October 2005 showed that CAD increased the cancer detection rate by 16.1 percent. This was the expected result, says chief investigator Tommy E. Cupples, MD, breast imaging and interventional specialist with ImageCare, LLC in Columbia, S.C.
Cupples says the study also revealed some unexpected findings. Studies that only look at the cancer detection rate don't tell about the nature of the cancer. That is, is it the size of a pea or a golf ball? Is the CAD finding smaller cancers earlier in the disease process?
"CAD is supposed to find small, irregular masses that are likely to be overlooked and associated with earlier cancers. So the real question is does CAD find small, earlier cancers," explains Cupples.
Cupples, who uses R2 Technology, Inc.'s ImageChecker, found that CAD does help find smaller cancers earlier in their development. The study found a 164 percent increase in small, invasive cancers less than one centimeter in size. In raw numbers, the results translate into two or three more cancers in a screening population in one year's time, estimates Cupples.
The study also examined patients' age at the time of diagnosis and found that the average patient age at time of cancer diagnosis decreased by 5.3 years with CAD. "CAD is doing exactly what is predicted-advancing diagnosis by finding subtle, faster growing cancers," states Cupples. A five millimeter mass in a 40-year-old woman is a larger concern than a similar mass in an 80 year-old patient. That's because the mass may increase only one or two millimeters per year in the older patient. The