What Radiologists Need To Know About Lung CAD
- There are lung CAD options for two modalities-x-ray and CT, but it's not an either-or scenario. Either or both solutions could be justified depending on site needs. The acceptance of CT as a screening tool could play a key role in the longer term CAD market.
- Both types of systems offer clinical benefits by serving as a second reader to highlight potential malignancies. CT systems provide additional workflow benefits via tools that facilitate navigation through CT data and automate clinical measurements.
- Reimbursement for lung CAD is not likely in the short-term. This may not deter adoption, however, as sites that take a comprehensive look at these systems, particularly CT-based solutions, find that they are cost-effective.
Lung CAD is here, with new systems arriving to radiology departments near you. First on the scene was Deus Technologies RS2000 in 2001, a x-ray-based system designed to highlight abnormalities on chest films. Deus followed up with the RS2000D in 2003, which is also marketed by GE Healthcare as RS Digital. This second-generation system works with digital and computed radiography (DR and CR) systems or digitized films.
R2 Technology's lung CAD answer is ImageCheckerCT, a lung CAD system designed to work with CT images. And Siemens Medical Solutions offers syngo LungCARE, a viewing technology designed to aid physicians in the diagnosis of pulmonary nodules, although not a CAD system. iCAD is working on Second Look CT Lung, its CT-based CAD solution.
The rapidly evolving lung CAD market spurs a number of questions. Pablo Delgado, MD and associate professor of radiology at University of Missouri-Kansas City, explains, "CAD technology is pushing radiologists to think about things they never did before. It could initiate a dramatic change in the practice of radiology."
Lung CAD vendors tout both clinical and workflow benefits. Lung cancer is notoriously lethal; its five-year survival rate is less than 15 percent. But when lung cancer is detected in the early stages, the survival rate increases to more than 50 percent. The hitch? Only 15 percent of lung cancers are found in the early stages. Studies demonstrate that radiologists miss nodules on lung CTs in 20 to 30 percent of cases. The statistics for chest x-rays are equally compelling. Clinical studies performed for the RapidScreen system indicate that radiologists working without the x-ray CAD system miss an average of 35 percent of solitary pulmonary nodules and 42 percent of solitary pulmonary nodules between 9 and 15 mm.
X-RAY BASED LUNG CAD
Physicians rely on chest x-rays for a laundry list of indications. It's an economical procedure that is the first line of offense for most patients with lung symptoms. Deus Technologies aims to increase the yield of truly positive lung cancers by highlighting suspicious regions on chest films.
RS-2000, Deus' first generation product, works exclusively with analog films and includes a digitizer. The DICOM compatible RS-2000D (also sold by GE as the RS-Digital) works with DR, CR and digitized films. RS-Digital is a simple and efficient process. The radiologist reads the unmarked chest image. It takes 20 to 30 seconds for the CAD post-processing algorithm to analyze the digital x-ray data and merge the CAD results with the patient's electronic exam folder. The radiologist pushes a key to display the CAD results on a separate screen. Suspicious areas are circled for additional review with an average of three or fewer marks per case.
Robert Gilkeson, MD, director of cardiothoracic imaging at University Hospitals of Cleveland says RS-Digital adds an extra 5 to 10 seconds per case and has not changed workflow in the radiology department. Gilkeson is cautiously optimistic about the future of lung CAD. After using CAD for two years, he estimates that CAD has made a difference in 3 to 5 percent of cases. John Brown, MD, chairman of radiology at Garden City Hospital and a beta user of the Deus system, agrees. He notes, "There are 155,000 deaths a year from lung cancer and 170,000 new cases each year, and it's less treatable than breast cancer. If we can find small lesions and treat them early, hopefully we will have better outcomes." Indeed, early stats with Deus' systems indicate that the technology can increase detection of small lesions by up to 72 percent.
Gilkeson expects to see additional gains in true positives in the future after CAD is applied with dual-energy subtraction,