Full-Field Digital Mammography
Mammography is defined as radiography of the breast. Digital mammography (DM) or full-field digital mammography (FFDM) has become commonplace in medical imaging departments. FFDM overcomes the limitations of film-screen mammography (FSM). Two major limitations include a limited dynamic range, and that the display characteristics such as brightness and contrast are fixed due to the chemical processing of the film. FFDM is radiography of the breast using a digital detector coupled to a digital computer that makes use of digital image processing techniques to enhance the visibility of detail and contrast of the image, in an effort to improve the detectability of breast lesions. FFDM consists of five steps which includes data acquisition, analog-to-digital conversion (ADC), digital image processing, image display, image storage, archiving, and communications via the picture archiving and communications system (PACS). Four types of digital detector systems are used for FFDM: flat-panel phosphor system, charge-coupled device (CCD) system, Flat-Panel amorphous Selenium (a-Se) System, and a computed radiography (CR) FFDM system. Detectors for FFDM must be capable of providing a spatial resolution of at least 10 line pairs/mm (lp/mm) to improve lesion detectability. Another performance characteristic of a FFDM detector is the detective quantum efficiency (DQE), which provides an indication of how well the FFDM imaging system can efficiently transfer the input signal-to-noise ratio (SNR) (at the detector) to the output SNR (image displayed on the monitor) so that it is useful to the observer in making a diagnosis. Digital image processing is an essential feature of FFDM and include operations such as windowing, measurement and annotation tools, as well as various sophisticated digital post-processing techniques, such as frequency processing for enhancing the sharpness of an image as well as manual intensity windowing (MIW), histogram-based intensity windowing (HIW), mixture-model intensity windowing (HMIW), contrast-limited adaptive histogram equalization (CLAHE), unsharp masking, and peripheral equalization. Applications of FFDM include computer-aided detection and diagnosis, digital breast tomosynthesis (DBT), and contrast-enhanced digital mammography. DBT is also referred to as three-dimensional (3D) mammography and is a relatively new technique which has increased attention in the literature.
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