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Mammography technique

» Why is mammography performed on dedicated breast imaging equipment?

Early breast cancer is difficult to detect because it appears similar to normal breast tissue. The difference between cancer and normal tissue needs to be amplified, and for this the use of lower energy X-rays is required. This can be achieved only with specially designed radiographic equipment dedicated to mammography. 

» Are specialized film-screen combinations required for mammography?

Yes.

The intensifying screens used for mammography are designed to produce very low blurring and good visibility of small structures and objects, especially microcalcifications. In order to detect small changes (in attenuation and in size) in breast tissue, it is necessary to have a film-screen combination which can detect very small differences at a low dose.

» Can mammography films be processed in an ordinary film processor?

Ideally the best results for standard non-digital mammography are obtained in a well adjusted film processor dedicated for mammography film. Ordinary processors can be used, but the quality of the mammograms produced might not be as good. Irrespective of which type of processor is used, it is vital that it is subject to rigorous quality control to ensure that optimum processing occurs all the time. 

» Why is a higher X-ray exposure required to produce a mammogram than other radiographic images, such as that of the chest?

This is because image information is required. 

In all X-ray imaging methods there is always a balance between image information (visibility of signs of disease) and the absorbed dose to the patient. In mammography, especially for detection of cancer at the early stage when it can be treated most effectively, images with high contrast sensitivity, high detail, and low visual noise are required. Each of these characteristics requires a relatively high X-ray exposure. 

X-ray beams with low penetrating characteristics must be used to produce visible images because the normal composition of the breast and the usual signs of cancer are in soft tissue with very little difference or physical contrast. This results in higher exposure. Another valuable sign of early cancer are small (micro-) calcifications. The imaging receptors necessary for their visibility require a higher exposure than receptors for other radiographic procedures.

» Can digital mammography be used and are there advantages?

Yes.

Digital imaging is replacing conventional imaging in general and also in mammography. Information is quickly available on the screen for making a diagnosis, it can be transmitted electronically to others and images can be printed on films as necessary. Image storage is easier and less bulky. Digital imaging also has the potential to reduce patient doses because there may be fewer repeat images. 

Staff operating the equipment find operation easier owing to improved equipment ergonomics. However, it may happen that images of quality higher than necessary are taken, as is observed for many other digital imaging techniques, and this can increase patient dose without adding diagnostic information. Chemical processing is not required to produce the images and this reduces the environmental impact as there are no waste chemicals.