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Mammography

Introduction

Mammography, be it screen-film or digital mammography, is one of the most demanding examinations in medical imaging requiring fine detail, high contrast, low patient motion, low noise images, and appropriate viewing conditions. In addition, with screen-film mammography the photographic processing is extremely critical to the quality of the final image.

First and foremost, mammography must be carried out using dedicated mammographic imaging equipment with low energy output (molybdenum or rhodium x-ray tube anode, or a tungsten anode at low kilovoltage, e.g., 30 kVp or less) imaging capability. It is not appropriate to perform mammographic examinations with other than a dedicated mammography system.

Important Principles

There are several manuals available regarding mammographic imaging. These emphasize the importance and proper use of technology, but also stress the importance of correct patient positioning and breast compression. Although the medical physicists do not directly play a role in positioning and compression, they must understand the need and assure that the equipment is functioning appropriately.

Image quality is extremely important in mammography and it is essential to assure that the entire imaging chain is functioning optimally. This includes the screens and film, the mammographic x-ray system, the photographic processor, and the viewing area and view boxes or digital displays. There is a section in the ACR Mammography Quality Control Manual entitled “Important Points” which discusses many of these areas.

Introduction to References

The essential references include information on both screen-film and digital mammography since much of the information regarding screen-film mammography is also applicable to digital mammography. The IAEA documents cover all aspects of a mammography quality assurance programme.

Click here to download IAEA publication "Quality Assurance Programme for Digital Mammography"


Well established national and regional QA programmes in mammography include the American College of Radiology Mammography Accreditation Program and European documents.  The ACR Mammography Accreditation Requirements provides a concise list of the requirements for dedicated mammography equipment in the Equipment section and for quality control in the Quality Control Section.

The NCRP report covers the history of mammography, looks at patient dose and risk, and provides guidance for the overall mammography screening programme and quality control.

Quality assurance

It has been demonstrated that routine screening with high quality mammography is effective in reducing mortality from breast cancer in women aged 40-69 (http://www.cancer.org/). In order to detect breast cancer accurately and at the earliest possible stage, the image must have excellent contrast to reveal mass densities and spiculated fibrous structures radiating from them that are characteristic of cancer. In addition, the spatial resolution must be excellent to reveal the calcifications, their number and their shape.  It has been well established that to achieve high quality mammography the following elements are essential: (i) well-trained and experienced personnel (radiologist, radiographer, medical physicist), (ii) modern, well designed equipment (iii) equipment in good working order (iv) proper positioning and technical factors for exposure and (v) appropriate image viewing conditions.  An effective quality assurance programme is necessary to ensure that all of these elements remain in place over time.

1. Principles of QA

A quality assurance (QA) programme in diagnostic radiology, as defined by the WHO, is an organized effort by the staff operating a facility to ensure that the diagnostic images produced are of sufficiently high quality so that they reliably provide adequate diagnostic information with both the lowest possible cost and the least possible exposure of the patient to radiation consistent with the requisite level of image quality. The establishment of a comprehensive QA program for medical diagnosis is required for this with the technical aspects of such a programme under the supervision of an appropriate medical physicist.

Relevant Human Health Website cross-links: Technology Management

2. Radiograph test

The tests provided in the IAEA QA document form a QC programme for the radiographer. This programme does not include maintenance or calibration procedures. Maintenance and calibration activities should be performed by the appropriate individual according to the manufacturer’s instructions. 

A brief description of the methodology to be undertaken when performing the radiographer’s QC tests is provided. The order in which tests are performed does not necessarily have to be that in which they appear in this document. The preferred order will depend on various factors relating to the mammography facility as well as the preferences of the individual performing the testing, always having in mind that the results of one test may affect the execution of others.

Radiographer data collection sheets can be found in Annex 1 of the Quality Assurance Programme for Screen Film Mammography (IAEA).

A specific IAEA publication addresses the quality assurance program that should be followed for digital mammography.

3. Medical physics tests

The tests provided in the IAEA QA document form a QC programme for the medical physicist. In addition to periodic testing, all tests should be performed at commissioning, i.e. before the equipment is initially used to image patients. Some commissioning tests are necessary to set up the base line values needed for the radiographer QC tests.  In some cases, the medical physicist may also be responsible for performing some of the tests described in the section on radiographer’s tests. 

Medical Physicist data collection sheets can be found in Annex 2 of the Quality Assurance Programme for Screen Film Mammography (IAEA) and for Digital Mammography in Annex II of the IAEA book Quality assurance programme for digital mammography.

4. Appendices

The appendices of the book Quality Assurance Programme for Screen Film Mammography give practical advice on subjects such as mammography room design, darkroom design, automatic processors, and areas of sensitometry. The appendices of the book Quality assurance programme for digital mammography, further to practical advice on mammography room design, also give specifications of test equipment and information on common non-clinical artefacts arising in digital mammography images.