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Development of a Soft-Copy Reading Environment for Digital Mammography in Breast Cancer Screening

Exploitable results

Breast cancer is the leading cause of death for European women aged 35 to 55. In the EU, the disease is diagnosed every two-and-a-half minutes and a woman dies every six-and-a-half minutes. This can be prevented. A European project, SCREEN, is taking the lead by developing soft-copy reading (SCR) technology to increase the effectiveness of digital mammography that will help save the lives of millions of women worldwide. Finland, Sweden, the Netherlands, UK, Iceland, Norway, Belgium and Luxemburg have implemented nationwide screening programmes. Most European countries have regional screening pilot projects running and some, such as Ireland, Germany, France and Spain, are expanding these nationwide in the next few years. Early detection and treatment reduces mortality. Currently, screen-film mammography screening is the most efficient and effective medical imaging method to address what some have called a "breast cancer epidemic". Studies in different countries predict a reduction in death from cancer of about 30 per cent due to mammography screening in women aged 50 to 75. The emerging digital mammography technologies have the potential to further increase the efficiency and effectiveness of breast cancer screening. The two-year SCREEN project started in January 2000 to develop a prototype high-volume soft-copy reading (SCR) system to replace film-based reading in screening. Researchers at seven university hospitals in France, Germany, The Netherlands, Italy, Norway and Sweden developed and evaluated a workstation that can be used in digital screening mammography. In a population-based screening mammography programme, very high-volumes of data are collected each day from screening units distributed over the country. Typically about 80 women can be screened per day on each mammography unit. With digital mammography, reading and archiving can be centralised more efficiently, and the lack of film will result in significant savings over time. Making the transition to digital mammography Traditionally, mammograms are film-based. Today, computer aided detection (CAD) is being used by increasing numbers of radiologists as a second pair of eyes. This technology has the potential to detect lesions and other abnormalities that might otherwise be overlooked. In particular, CAD technology is very effective at identifying calcifications, some of which are the only visible sign of a cancer. The lack of a soft-copy reading environment has been a major obstacle to the transition from film-based to digital mammography in Europe's breast screening programmes. In a film-based environment, image acquisition, storage and display are coupled to film, while in digital mammography these processes are handled separately. Image acquisition takes place in digital detectors, images are stored on electronic storage media such as hard drives, and the display can be done on computer monitors. Reading from the computer monitors is known as soft-copy reading. SCREEN demonstrated the medical, technical and economic feasibility of SCR with digital mammograms and will provide technological and scientific guidance to other facilities to help complete the transition process over the next few years across Europe. "Soft-copy reading and computer-aided detection technology are expected to have significant impact on the efficacy and quality of patient care, and overall improvement in accuracy of mammography," said project coordinator Dr Carl Evertsz, CEO of MeVis BreastCare, Bremen, Germany. "By bringing together the leading-edge soft-copy reading platform and integrating CAD-markings, as well as patient information into an optimised workflow system, we are able to provide radiologists the best of CAD and soft-copy reading technology available for early breast cancer detection." SCREEN leads to all round improvements Project partners developed software architecture capable of handling very large amounts of image data using off-the-shelf computer hardware. A digital mammography image can be 60 MB comprising of 4800x6000 pixels. Because women are encouraged to be screened at regular intervals (typically every two years in the age group 50-75) the four current mammograms (two per breast) must be compared with the four prior ones, so as to detect temporal differences. Per woman, this yields about 0.25 GB of image data. The new workflow developed in the project is reader-driven via a dedicated keypad that concentrates most actions in a few keys. Predefined templates allow efficient and detailed digital annotation for each detected lesion individually. Reports for each case are automatically generated. The system has been designed to allow screening radiologist to read more than 150 women in an hour. Various features have been built into the system to help improve the efficiency and accuracy of the screening radiologists. The display of CAD results have been integrated in the soft-copy reading system to naturally fit in the reading workflow. Special graphics boards are used to drive two high-resolution 5 MegaPixel monitors with 10 bit greyscale resolution. An anonymous database of over 1,000 fully annotated digitised film-screen cases from the Dutch screening programme have been collected to support research, teaching, the development of algorithms, product testing and product demonstration. The original film-screen mammograms have been digitised to a resolution of 100 microns. Each case consists of images from two consecutive screening rounds. A computer assisted training system has been built into the softcopy reading system that is based on the case database. Cases with known pathology can be added at random during the radiologist's reading session. If the radiologist makes a mistake on such cases, a warning is issued. If mammograms are not displayed by the radiologist in the resolution necessary for detecting the smallest cancers, the system automatically warns the user. SCREEN Trial addresses future challenges SCREEN removed the obstacles to soft-copy reading. Challenges ahead include incorporating the digital technologies. For example, the transition to digital mammography typically takes about two years, requires training and is costly. To come up with solutions to expedite the use of digital mammography, soft-copy reading and CAD in European screening programmes, SCREEN Trial was launched in April 2002. The project's strategy is to bundle and manage existing technological, scientific and clinical expertise to install soft-copy reading and digital mammography at user demonstrate sites in Norway, The Netherlands, Germany, Italy, Sweden and France. The global market is promising and includes Original Equipment Manufacturers (OEM) of digital mammography, OEM in technological areas that require high-quality high-resolution display systems (medical, aviation, military), European screening mammography programmes, hospitals and clinics, breast care centres and private practitioners that specialise in mammography. The work of SCREEN and its subsequent trials together should help radiologists around the world to embrace and adopt digital mammography, increase the effectiveness of screening programmes and ultimately contribute to saving millions of lives worldwide. Promoted by the IST Results Service