CAD: Computer-Aided Detection is Proving its Worth in Mammography

The thought of taking the human element out of radiology and turning some healthcare decisions over to a computer may be hard to fathom for many providers. However, as computer-aided detection (CAD) becomes an increasingly valuable tool in radiology departments, research on the benefits of CAD are converting more believers.

Computer-aided detection uses proprietary algorithms in a computer program to identify a suspicious mass, such as a lesion, in a patient image after a radiologist has finished his or her initial interpretation. Computer-assisted diagnosis, which also carries the acronym CAD, reviews the discovery of the region in question and helps determine the probability of malignancy or benignity.

The great majority of CAD evaluations are performed for mammography, with a smattering of chest-lung and virtual colonoscopy screenings accounting for a small portion of total procedures. While breast CAD has been utilized in MRI and mammography, companies developing chest-lung and virtual colonoscopy CAD are planning on integration with computed tomography (CT).

Over the last seven years, sales in the U.S. CAD market have blossomed from nothing to $65.2 million in 2002. Last year's numbers are more than double sales in 2001. 

CAD has become so prevalent in mammography that industry estimates are that in 2003 the technology will be used as an adjunct to review more than 5 million mammograms in the United States.  


Spurring the adoption of CAD in health imaging centers, hospitals and radiology practices across the United States are reimbursement rates for CAD mammography screening. Since the American Medical Association approved a CPT (common procedural terminology) code for CAD and mammography, effective January 2002, reimbursement rates advanced 8 percent this year to $19.13 - after receiving an 18 percent hike in 2002.

More than 450 insurance plans have paid for CAD mammography screenings, which also are reimbursed by all but six Blue Cross and Blue Shield plans in the United States. The coverage translates to approximately 90 percent of U.S. female patients.


Frost & Sullivan cited R2 Technologies Inc. and CADx Systems Inc. as the top companies in the U.S. CAD market in a recent study. R2 holds the lion's share after bursting on the scene in May 1998. That's when the FDA cleared R2's pre-market approval (PMA) application for the ImageChecker CAD system for use in mammography screenings. CADx entered the competition with its Second Look CAD system in February 2002 with FDA clearance on its PMA. In the previous month, iCAD Inc. (doing business at the time as Intelligent Systems Software Inc.) received FDA clearance to market its MammoReader CAD product.

In July 2001, Deus Technologies Inc. received the FDA's OK for its RapidScreen RS-2000 CAD system, which digitizes and analyzes chest x-rays to assist in the detection of early-stage lung cancer. This past July, the FDA also cleared Deus' Rapid Screen Digital as an adjunct with digital chest systems.

Scanis Inc. currently is marketing its MammoCAD system in Europe and Canada. MammoCAD is available in the United States for investigational use only. The company in February inked a deal for iCAD to secure a patent license to certain U.S., Canadian and Japanese patents owned by Scanis and related to Scanis' CAD technology.


How successful is CAD in detecting breast cancer when used as a second source in film-screen mammography review? The FDA has accepted R2's estimate derived from its clinical trials that CAD technology can detect an additional 23.4 percent of breast cancer cases in women.

Studies from Stanford University Medical Center (8,682 cases) and The Mayo Clinic (16,203 cases), released at the 2002 annual meeting of the Radiological Society of North America (RSNA), found that mammography screening with CAD increased cancer detection rates by 7.4 percent and 7.3 percent, respectively.

The Blue Cross and Blue Shield Association's Technology Evaluation Center (TEC) also weighed in on the research last December, unveiling its conclusions after evaluating composite results from 11 studies. Seven research projects employed R2's ImageChecker, while CADx's Second Look and iCAD's MammoReader were used in two studies each.

The TEC highlighted one particular study, which included 12,860 mammograms analyzed by R2's ImageChecker M1000 version 2.0 CAD systems. Radiologists detected 41 cancers from the 12,860 screenings; the use of CAD technology detected eight additional cancers, which included six ductal carcinoma in situ lesions and two invasive ductal cell carcinomas. The increased detection rate with CAD translates to 19.5 percent.


Blue Cross' Technical Evaluation Center concluded that the "available evidence suggests the use of CAD after initial radiographic interpretation as a quality adjunct to single-reader mammography in patients having film-screen mammography improves net health outcomes compared with the single-reader radiologist interpretation by increasing true-positive rate without a disproportionate increase in the false-positive rate."

In a paper presented at the annual meeting of American Healthcare Radiology Administrators (AHRA) in August, Gary R. Kolb, J.D., president of Breast Health Management Inc., said the CAD systems approved for sale in the United States are differentiated by the quality of the algorithms, as well as by differences in digitization rates, ease of use and methods of display.

"These differences manifest as process time, both for the technology staff and, more importantly, for the physician," Kolb noted. "Because physician time is so expensive relative to the other cost inputs, it is important that the selection of a CAD system be based on how well CAD can be integrated into the delivery process, including interpretation."


Many industry people see CAD becoming such an invaluable tool in mammography that eventually CAD will reverse roles with the radiologist.

Ronald A. Castellino, M.D., chief medical officer for R2, speaking at AHRA 2003, said that he is "100 percent certain" that CAD eventually will have the first "pass through" on mammograms.

"I think we'll see the first reader being the computer and the radiologist will look at the suspicious areas second," he said.

Also, look for CAD to expand beyond the current scope of mammography into health imaging modalities, especially MRI and CT.

Confirma Inc. in November 2002 launched its CADstream for contrast-enhanced MRI studies, targeting the breast to automate processes used in breast MR analysis. CADstream is FDA-cleared and, as of mid-September, was installed in more than 40 sites throughout the United States.

Confirma is looking to offer CADstream to other contrast enhanced MR imaging study applications, inclu ing head and neck, spine, pelvic/abdominal, vascular and other MRI studies.

R2 also wants to expand its technology portfolio by integrating CAD and CT. The company has a works-in-progress called ImageChecker CT, which R2 says is designed for CAD CT images of the lung to detect nodule. R2 also plans to develop CAD for CT virtual colonoscopy and use with other modalities, such as computed radiography and digital radiography to enhance chest images.