Introduction
The goal in screen-film mammography for mass screening and diagnosis is to produce consistently high-contrast, high-resolution, low-noise images at the lowest radiation dose consistent with these image-quality requirements. In recent years, there have been many significant technologic improvements in mammographic screen-film combinations AAPM, 1990 Haus, 1991 1999b KimmeSmith, 1991 Rothenberg and Haus, 1995 Yaffe, 1990 . Until the early 1970s, direct-exposure industrial type x-ray films were...
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aPercentages in parentheses indicate the number of cases divided by the number of examinations interpreted. cancers at fairly similar rates. This apparent discrepancy is best understood by observing that the most experienced radiologist makes fewer abnormal interpretations while still identifying a relatively high percentage of favorable-prognosis cancers. However, viewed from a different perspective, it also is evident that radiologists B, C, D and F are overreading because they produce higher...
Grid 1
Dedicated mammographic units should be equipped with anti-scatter grids ACR, 1993 AHCPR, 1994 . Scattered radiation can cause a significant reduction in subject contrast in mammogra-phy resulting in impaired detection of calcifications and the outlines of tumor masses. The advent of specialized mammographic grids revolutionized the radiologist's ability to evaluate dense tissue Barnes and Brezovich, 1978 Chan et al., 1985 Dershaw et al, 1985 Egan et al., 1983 Friedrich and Weskamp, 1978 Jost,...
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system can be designed such that the dynamic range of the image receptor is very large so that recording of scattered radiation will not be a limiting factor. Under these conditions, only the third effect, the scatter contribution to random quantum noise, should be of any importance. 4.2.1.1.2 Grids for mammography. The use of specifically designed grids for mammography reduces the amount of scattered radiation detected and improves subject contrast. This is especially significant when imaging...
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Fig. 3.2. Geometry of a mammography x-ray tube. Fig. 3.2. Geometry of a mammography x-ray tube. dimension of a 24 x 30 cm cassette. For a 60 cm SID, this requires an effective target angle of 22 degrees. In turn, this can be achieved by using an x-ray tube with a 22 degree target or by appropriately tilting an x-ray tube with a smaller target angle e.g., a six degree tilt of a 16 degree target . The effective size of the x-ray tube focal spot feff is another important consideration in...
Usefulness of Mammography for Breast Cancer Screening
There is little, if any, opposition to the practice of diagnostic mammography, probably because of the compelling clinical need for the information obtained. Many mammography examinations are performed for diagnostic purposes, and mammographic screening programs have also been widely implemented. There has been some opposition to screening in the past for a variety of reasons 1 concern over a few published indications of a relatively unfavorable benefit risk ratio, 2 concern about exposure to...
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reference axis Figure 3.5 . Therefore, in order to compare measured and nominal focal-spot sizes, the measurement made at the chest wall needs to be corrected to estimate its size at the reference axis. The reference axis usually bisects the angle formed by the x-ray tube target and the ray perpendicular to the image receptor at the chest-wall edge of the image receptor . Thus, for an x-ray tube with an effective target angle of 22 degrees target angle of 16 degrees plus a tube tilt of six...
Transillumination
Transillumination of the breast began in 1929 with the real-time viewing diaphanoscopy of the breast by a dark-adapted examiner Cutler, 1929 . The technique was found somewhat helpful in distinguishing cystic from solid lesions and, specifically, in suggesting the diagnosis of hematoma and retroareolar intraductal papilloma. After a period of initial interest, the technique lapsed into relative obscurity, only to be revived in France in the 1950s with the recording of hard-copy images...
Anatomy
The fully-developed female breast is a well-differentiated apocrine sweat gland originating in the ectoderm that secretes milk during lactation. Each breast is cone-shaped, particularly in younger nulliparous females, extends from the sternum to the midaxillary line, and lies anterior to the pectoral muscle. A thin outer dermal layer covers a subdermal layer of adipose tissue that varies in thickness from several millimeters to 1 cm. Cooper's ligaments Figure 2.1 are strings of fibrous...