Bush__The_Essential_Physics_for_Medical_Imaging - Biomedical ...

Mammography is a radiographic examination that is specially designed fordetecting breast pathology. Interest in breast imaging has been fostered by therealization that approximately one in eight women will develop breast cancerover a lifetime. Technologic advances over the last several decades have greatlyimproved the diagnostic sensitivity of mammography. Early x-ray mammographywas performed with nonscreen, direct exposure film, required high radiationdoses, and produced images of low contrast and poor diagnostic quality. In fact,it is possible that early mammography screening exams, in the 1950s and 1960s,did not provide any useful benefits for the early detection of breast cancer. Mammographyusing the xeroradiographic process was very popular in the 1970s andearly 1980s, spurred by good spatial resolution and edge-enhanced images; however,the relatively poor contrast sensitivity coupled with a higher radiation dosein comparison to the technologic advances of screen-film mammographic imagingled to the demise of the Xerox process in the late 1980s. Continuing refinementsin technology have vastly improved mammography over the last 15 years,as illustrated by breast images from the mid-1980s and late 1990s (Fig. 8-1). TheAmerican College of Radiology (ACR) mammography accreditation programchanged the practice of mammography in the mid-1980s, with recommendationsfor minimum standards of practice and quality control, which spurredtechnologic advances and ensured quality of service. In 1992, the federal MammographyQuality Standards Act (MQSA) largely adopted the voluntary programand incorporated many of the recommendations into regulations. The goalof the MQSA is to ensure that all women have access to quality mammographyfor the detection of breast cancer in its earliest, most treatable stages, with optimalpatient care and follow-up. The MQSA regulations continue to evolve andadapt to changing technologies. Emerging full-field digital mammographydevices promise rapid image acquisition and display with better image quality,anatomy-specific image processing, and computer-aided detection tools to assistthe radiologist in identifying suspicious features in the images.Breast cancer screening programs depend on x-ray mammography because itis a low-cost, low-radiation-dose procedure that has the sensitivity to detectearly-stage breast cancer. Mammographic features characteristic of breast cancerare masses, particularly ones with irregular or "spiculated" margins; clusters ofmicro calcifications; and architectural distortions of breast structures. In screeningmammography, two x-ray images of each breast, in the mediolateral oblique