This Report is intended to be a practical guide to physicians who interpret mammographic images, technologists who perform mammographic examinations, as well as medical physicists who monitor mammographic facilities, evaluate image quality, and determine radiation dose.
Mammography is one of the most difficult radiographic examinations technically. Both specialized equipment and the correct use of that equipment are essential to the achievement of satisfactory results. Facilities should not perform the examination if they are unable or unwilling both to: (1) provide and maintain x-ray equipment, image receptors, film processors, and viewing conditions capable of producing the necessary images at acceptable dose levels; and (2) assure that the examination is performed with the proper technique factors, patient positioning, and compression. In fact, the implementation of MQSA (1992) has made it illegal for facilities to continue to perform mammography unless these conditions are fulfilled.
This Report contains several major sections, a summary and conclusions, and an extensive bibliography.
Sections 2 and 3 present conventional imaging techniques used for x-ray mammography. Positioning and breast anatomy are discussed in Section 2 along with optimum technique. Section 3 discusses recommendations for optimum choice of equipment.
A major consideration of any mammography system is the quality of the image. In Section 4 the factors which affect image quality are defined, the parameters used to judge image quality are discussed, appropriate phantoms to measure these parameters are described, and the relationship between patient dose and image quality is examined for several imaging systems.
Mammography dosimetry is necessary to compare different imaging techniques and to evaluate their risks. Section 5 discusses the various dose or exposure parameters which have been employed as "risk" indicators and describes how to calculate mean glandular dose from measured exposures (free-in-air) and a knowledge of x-ray tube operating potential, beam quality, and x-ray tube target and filter material.
A QA program is necessary to insure consistent high-quality mammography at acceptably low dose levels. Section 6 discusses the various factors which should be evaluated and techniques for measuring them, limits beyond which corrective action should be taken, and the testing frequency and personnel requirements.
Section 7 contains a discussion of the benefits and risks of mammography derived from results of mass screening studies along with estimates of the risk of inducing breast cancer at mam-mographic screening radiation dose levels. Section 7 concludes with an analysis of the benefit to radiation risk relationship in mammography.
Several imaging techniques have been developed in recent years. Those now being applied to imaging of the breast are described in Section 8.
The summary and conclusions section of this Report briefly review the detailed material presented and present recommendations for: (1) equipment to obtain optimum mammograms; (2) QA programs; and (3) the necessity and frequency of mammographic examinations for women based on their symptoms, age, and risk factors.
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