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How Mammography is Performed: Imaging and Positioning

Notice: Revised breast cancer screening guidelines issued in November 2009.

This article illustrates how different mammography views are taken, and how the patient should be positioned to achieve optimal mammogram images. The information presented in this section is intended for mammography technologists, healthcare professionals, and patients interested in learning more about mammography imaging and positioning.

All images are courtesy of Siemens Medical, and captions are based on information from the Siemens "Mammography Applications" handbook. The information herein is intended for mammography performed with the Mammomat 3000/300 and 3000/1000 Nova but can also be used as a general guideline for mammography performed with other mammography systems. Because each case is unique, different patients may require different mammography views, etc.

Brief Overview of Mammography

Mammography is currently the only exam approved by the U.S. Food and Drug Administration (FDA) to help screen for breast cancer in women who show no signs of the disease. A screening mammography is every one to two years is recommended for in their forties. Women in their 50s should receive screening mammograms every year. Screening mammography typically involves taking two views of the breast, from above (cranial-caudal view, CC) and from an oblique or angled view (mediolateral-oblique, MLO). Diagnostic mammography may be performed to examine an abnormality detected by screening mammography or physical exam. Diagnostic mammography may involve taking supplemental view tailored to the specific problem. These may include views from each side (latero medial, LM: from the side towards the center of the chest, and mediolateral view, ML: from the center of the chest out), exaggerated cranial-caudial, and other special views such as spot compression and magnification views. If an abnormality is detected with diagnostic mammography, follow-up may include additional breast imaging, such as ultrasound, or biopsy.

Mediolateral Oblique View (MLO)

The mediolateral oblique view (MLO) is taken from an oblique or angled view. During routine screening mammography, the MLO view is preferred over a lateral 90-degree projection because more of the breast tissue can be imaged in the upper outer quadrant of the breast and the axilla (armpit).

This illustration shows the angled or oblique MLO view and the cranial-caudal view (CC), which is taken of from above.

 With the MLO view, the pectoral (chest) muscle should be depicted obliquely from above and visible down to the level of the nipple or further down. The shape of the muscle should curve or bulge outward as a sign that the muscle is relaxed; the medial (middle) portion of the breast should be prominent in the MLO view. It is important that compression be applied over the whole image area. The nipple should be depicted in profile and a small stomach fold should be visible as a sign that the whole breast is reproduced.

Positioning a patient for an MLO view:

#1: To take an MLO view, the mammography technologist will set the angle for the desired projection (30 degrees to 60 degrees). The object table is the platform that supports the breast and holds the film cassette or digital detector. The object table should be parallel with the pectoral (chest) muscles, and the top edge of the table should be level with the axillary (armpit) fold.


#2: During an MLO view, the patient should stand stead at a 45-degree angle to the mammogram stand. The technologist will instruct the patient to lift her elbow while keeping her hand firmly on the machine’s handle. The patient will bend slightly forward, and the technologist will take hold of the lifted arm and breast from below, drawing the medial (middle) portion of the breast forward. The technologist will then apply compression while holding the patient’s collarbone (clavicle) so that the compression plate is just clearing the collarbone. When the compression is sufficient, the technologist will make sure nothing is blocking the field of the intended image.

#3: When the patient has been properly positioned, the technologist will ask her to stand absolutely still and then leave to make the exposure.