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AAPM/RSNA Physics Tutorial for Residents

Digital Mammography: An Overview¹

¹ From The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, JHOC Suite 4235, 601 N Caroline St, Baltimore, MD 21287-0856. From the AAPM/RSNA Physics Tutorial at the 2003 RSNA scientific assembly. Received May 12, 2004; revision requested June 17 and received June 30; accepted July 15. The author has no financial relationships to disclose. Address correspondence to the author (e-mail: mmahesh@jhmi.edu).

View larger version (32K): [in a new window]   Figure 1.  Typical process of x-ray mammography.

View larger version (28K): [in a new window]   Figure 2.  Typical response curves for SFM and digital mammography. SFM has a limited dynamic range, whereas digital mammography has a wider dynamic range.

View larger version (39K): [in a new window]   Figure 3.  Limitations of SFM in imaging a breast composed of a wide range of tissues. Different regions of the breast image are represented according to the characteristic response of a typical mammographic film.

View larger version (19K): [in a new window]   Figure 4.  Unlike with SFM (left), each component of the mammographic process can be optimized with digital mammography (right).

View larger version (55K): [in a new window]   Figure 5a.  (a-c) Images of a breast phantom obtained with an SFM system by using automatic exposure control (b), using one-half of the milliampere-seconds value (a), and using double the milliampere-seconds value (c). The images are displayed on a high-luminance view box. (d-f) Corresponding images obtained with a full-field digital mammography (FFDM) system. The effect of underexposure on image quality is increasing noise, whereas overexposure decreases noise at the expense of longer exposure and higher breast dose. With the digital mammograms (d-f), underexposure and overexposure do not affect image contrast.

View larger version (78K): [in a new window]   Figure 5b.  (a-c) Images of a breast phantom obtained with an SFM system by using automatic exposure control (b), using one-half of the milliampere-seconds value (a), and using double the milliampere-seconds value (c). The images are displayed on a high-luminance view box. (d-f) Corresponding images obtained with a full-field digital mammography (FFDM) system. The effect of underexposure on image quality is increasing noise, whereas overexposure decreases noise at the expense of longer exposure and higher breast dose. With the digital mammograms (d-f), underexposure and overexposure do not affect image contrast.

View larger version (85K): [in a new window]   Figure 5c.  (a-c) Images of a breast phantom obtained with an SFM system by using automatic exposure control (b), using one-half of the milliampere-seconds value (a), and using double the milliampere-seconds value (c). The images are displayed on a high-luminance view box. (d-f) Corresponding images obtained with a full-field digital mammography (FFDM) system. The effect of underexposure on image quality is increasing noise, whereas overexposure decreases noise at the expense of longer exposure and higher breast dose. With the digital mammograms (d-f), underexposure and overexposure do not affect image contrast.

View larger version (112K): [in a new window]   Figure 5d.  (a-c) Images of a breast phantom obtained with an SFM system by using automatic exposure control (b), using one-half of the milliampere-seconds value (a), and using double the milliampere-seconds value (c). The images are displayed on a high-luminance view box. (d-f) Corresponding images obtained with a full-field digital mammography (FFDM) system. The effect of underexposure on image quality is increasing noise, whereas overexposure decreases noise at the expense of longer exposure and higher breast dose. With the digital mammograms (d-f), underexposure and overexposure do not affect image contrast.

View larger version (136K): [in a new window]   Figure 5e.  (a-c) Images of a breast phantom obtained with an SFM system by using automatic exposure control (b), using one-half of the milliampere-seconds value (a), and using double the milliampere-seconds value (c). The images are displayed on a high-luminance view box. (d-f) Corresponding images obtained with a full-field digital mammography (FFDM) system. The effect of underexposure on image quality is increasing noise, whereas overexposure decreases noise at the expense of longer exposure and higher breast dose. With the digital mammograms (d-f), underexposure and overexposure do not affect image contrast.

View larger version (128K): [in a new window]   Figure 5f.  (a-c) Images of a breast phantom obtained with an SFM system by using automatic exposure control (b), using one-half of the milliampere-seconds value (a), and using double the milliampere-seconds value (c). The images are displayed on a high-luminance view box. (d-f) Corresponding images obtained with a full-field digital mammography (FFDM) system. The effect of underexposure on image quality is increasing noise, whereas overexposure decreases noise at the expense of longer exposure and higher breast dose. With the digital mammograms (d-f), underexposure and overexposure do not affect image contrast.

View larger version (86K): [in a new window]   Figure 6a.  Analog and digital mammograms of a moderately dense breast. (a) Analog image demonstrates poor penetration in the dense region. (b) Digital image has improved contrast, shows a suspicious mass more clearly, and allows better visualization of peripheral tissue and the skin line. (Courtesy of Laurie Fajardo, MD, University of Iowa, Iowa City.)

View larger version (95K): [in a new window]   Figure 6b.  Analog and digital mammograms of a moderately dense breast. (a) Analog image demonstrates poor penetration in the dense region. (b) Digital image has improved contrast, shows a suspicious mass more clearly, and allows better visualization of peripheral tissue and the skin line. (Courtesy of Laurie Fajardo, MD, University of Iowa, Iowa City.)

View larger version (50K): [in a new window]   Figure 7a.  Full-size (a) and detail (b) photographs of the SenoScan system. The breastplate housing the detector assembly is curved to allow slot-scanning motion. This system is thus different from other mammography systems. (Courtesy of Fischer Imaging.)

View larger version (110K): [in a new window]   Figure 7b.  Full-size (a) and detail (b) photographs of the SenoScan system. The breastplate housing the detector assembly is curved to allow slot-scanning motion. This system is thus different from other mammography systems. (Courtesy of Fischer Imaging.)

View larger version (42K): [in a new window]   Figure 8.  Diagram of an a-Si TFT array. The digital detector array is constructed from an a-Si TFT matrix deposited on a glass substrate. The CsI scintillator is deposited on the a-Si detector, and each light-sensitive diode element is connected by TFTs to control and data lines, so that charge produced in the diode in response to light emission from the scintillator is read out and digitized. (Courtesy of GE Healthcare, Waukesha, Wis.)

View larger version (144K): [in a new window]   Figure 9.  A clinical installation of the Senographe 2000D system. The breastplate housing the detector assembly is flat, similar to that of other mammography systems. In the background is the technologist’s workstation, where images are acquired and previewed before being transmitted to a review workstation located elsewhere. (Courtesy of GE Healthcare.)

View larger version (50K): [in a new window]   Figure 10.  Photograph of the a-Se digital detector used in the Selenia system. a-Se, a good photoconductor, is deposited directly onto the a-Si TFT substrate, enabling direct capture. (Courtesy of Hologic.)

View larger version (48K): [in a new window]   Figure 11a.  (a) Diagram of the digital receptors in a small-field-of-view stereotactic biopsy unit. The scintillator is linked to a CCD by a minifying fiberoptic taper. (b) Photograph of the tiled CCD detector assembly (3 x 4 CCD array) used in the CCD array FFDM system. (Courtesy of Laurie Fajardo, MD.)

View larger version (60K): [in a new window]   Figure 11b.  (a) Diagram of the digital receptors in a small-field-of-view stereotactic biopsy unit. The scintillator is linked to a CCD by a minifying fiberoptic taper. (b) Photograph of the tiled CCD detector assembly (3 x 4 CCD array) used in the CCD array FFDM system. (Courtesy of Laurie Fajardo, MD.)

View larger version (122K): [in a new window]   Figure 12.  Soft-copy display of a digital mammogram shows magnification of a suspicious area, which is evaluated without additional radiation exposure to the patient.

View larger version (114K): [in a new window]   Figure 13.  Typical layout of a mammography reading room in a center with both FFDM and SFM systems. To accommodate both digital and analog images, high-resolution computer monitors are placed at right angles to high-luminance view boxes to minimize spectral reflections from either of the reading systems. With digital displays, it is important to set up computer monitors in areas with minimal ambient light (<5 lux).