Viewing Your Views: Assessing & Correcting the Standard Mammogram Projections

With the implementation of standard pectoral mobilization mammography techniques, it is now possible to produce consistent images and correct our errors dependably instead of merely ‘repeating’ our mistakes ad infinitum. To properly assess the routine projections of the breast we must identify the delineating landmarks of the breast borders and then take any corrective measures necessary to include them in our film field.

The CC Projection: The cranial\caudal view of the breast should demonstrate all of the breast tissue except for the axillary tail. The essential landmarks delineating the CC view include:

1. Medial curve of the breast: Should be smooth open with a ‘ski-slope’ of tissue toward the contra-lateral side
2. Nipple should be in clear profile (tissue should not be sacrificed to accomplish this)
3. Tail-of-Spence
4. Pectoral muscle
5. Parenchyma spread smoothly across image
6. Posterior Nipple Line must be within 1cm of the MLO’s PNL

1. It is essential for the medial curve or nub to be visible on the CC view. To ensure that this is always the case, be sure to position from the medial\anterior aspect of your patient. Lift, abduct and drape the opposite breast tissue over the edge of the bucky. Never sacrifice medial tissue to obtain the Tail of Spence.
2. The nipple on the CC view should be in direct profile on the image. To help accomplish this be careful to raise the IMF until it is directly parallel with the bucky, use two hands to pull and anchor the breast onto the bucky. NEVER sacrifice tissue to accomplish a profile outline of the nipple. Take adjuvant ‘nipple shot’ to achieve this if necessary.
3. The tail of Spence is the axillary tail visible in the CC projection. To assure we have both the essential medial and the axillary tail in the CC view position from the medial side of the patient and is careful to pull the lateral breast tissue forward and towards you as the compression takes hold of the view. If it is impossible to image the entire tail-of-Spence, take an adjuvant XCCL view.
4. A small ‘half-moon’ of pectoral shadow should show on about 40-65% of your CC images. It is advantageous to image the pectoral ‘moon’ at every opportunity. To do so, lift the IMF and breast mound cephalically until you see the bulge of pectoral muscle emerge just under the clavicle and the IMF is parallel to the bucky. Compress directly along the posterior edge and pull the breast forward and laterally as the compression takes hold.
5. To achieve a well compressed CC projections use the thumb and index fingers to anchor the breast tissue firmly. Pull your hand anteriorly and laterally as the compression takes hold but do NOT let go of the breast until the view is definitely immobilized. The skin of the breast should be taut and slightly whitened. Compression should never cross the line from discomfort to actual pain.
6. The posterior nipple line is measured from the nipple\skin junction directly to the back of the image. The PNL on the CC image MUST be within 1cc of the PNL on the MLO view. Obviously, these measurements loose validity if your MLO was positioned poorly. However, the PNL still provides a simple mechanism for comparative assessment of the adequate depth of the CC projection.
   

The MLO Projection: When properly obtained the mediolateral oblique view should demonstrate virtually all of the breast tissue. The essential landmarks for the MLO view include:

1. Pectoral muscle gently curving convexly from the axilla to below the nipple shadow
   
2. Axillary Tail clearly seen through the pectoralis in its entirety
   
3. Nipple in profile if possible
   
4. Infra-mammary Fold open gently curving to the abdomen
   
5. Posterior Nipple Line
   
6. Parenchyma Spread evenly across the image with the parenchyma ‘up & out’ imaging a line of retro mammary fat at the chest wall

1. The Pectoral Muscle should be seen to below the level of the nipple shadow. If this is not the case, then, the determination of the pectoral angle has been incorrectly estimated. Reassess and change to bucky’s angle if necessary. Mobilize the full length of the lateral border of the pectoral grid. Bring it medially and anteriorly until the pectoral bulge appears along the sternal border from the shoulder to the lower 1\3 of the sternum. Set the bucky angle absolutely parallel to the edge of this pectoral angle. Compress parallel to and directly behind this pectoral bulge until your positioning is immobilized. It is important to remember when performing the MLO view that you are positioning parallel to the pectoral muscle NOT the chest wall. The anterior margin of the pectoral muscle should exhibit a soft convex configuration. Triangular, concave or vastly bulging muscle shadows indicate a significant loss of posterior\inferior breast tissue and/or poor breast compression. To accomplish this we must have our patient’s shoulder softly open and relaxed over the bucky corner. Place the corner of the bucky high up and posteriorly into the axilla. Her elbow should be bent and relaxed with her arm hanging loosely behind the bucky. She should loosely grasp the handle bar with her elbow making an 80 – 95 degree angle.
2. The Axillary Tail The upper glandular tissue that projects over the pectoral muscle MUST project into the field of view. The Tail of Spence is an essential landmark and must not be ‘cut off’. This tissue lies beside and behind the lateral edge of the pectoral margin. The technologist must mobilize the upper lateral edge of the pectoral grid and move it adequately anteriorly and medially to adequately visualize the entire axillary tail in the MLO view.
   
3. The Nipple in profile has been over emphasized in many positioning manuals. This should never be accomplished at the expense of posterior breast tissue. An extra subareolar view can always be obtained with the nipple in profile. The radiologist usually insists upon seeing a profile of the nipple in either the CC or the MLO projection.


4. The Infra-mammary Fold (IMF) should appear as a smooth open concave curve toward the belly at the inferior border of your image. Visualizing the IMF assures the radiologist that a marked amount of inferior posterior tissue has not been excluded form the image. To produce a clear open IMF gently curving toward the abdomen, the mammographer must hold the MLO position immobile until the compression has taken over the task of holding the breast mound perpendicular to the pectoral angle. After removing your hand with the upward\outward movement, as your very last positioning procedure, run your thumb and forefinger down along the IMF towards the abdomen. Carefully tilt your patient’s hips backwards removing any belly folds that are in the field of vision.
5. The Posterior Nipple Line (PNL) on the MLO should be measured from just behind the nipple base directly parallel to the cooper’s ligaments to the front of the pectoral shadow (not to the chest wall). The PNL of the MLO must measure within 1cm of the PNL on the CC.
6. The Parenchyma must spread evenly across the image with cooper’s ligament straight and perpendicular to the pectoralis. To demonstrate all the breast tissue on the MLO view a line of fat should always separate the glandular parenchyma from the pectoral fascia.




To accomplish clearly visualized, well compressed, complete parenchyma in the MLO we must mobilize the pectoral grid medially and pull it forward. We must hold the breast mound perpendicular to the pectoral angle and then, allow the compression to take hold parallel to and just behind the pectoral bulge. If these positioning criteria are adhered to the entire parenchyma will be clearly visualized



SUMMARY

We would never dream of handing in a chest x-ray with a missing apex or base. Please, don’t forget to ‘view your views’ look for the delineating landmarks for your breast x-rays and take the appropriate corrective action.

Until next time friends,
Anne