The routine two-view mammogram consists of a CC projection, and a MLO projection (ACR, 1993). The following sections describe these views. More specialized views are described in the ACR Mammography Quality Control Manual (ACR, 1999).
The technologist's alertness and diligence are the keys to good positioning. The technologist requires special training to learn correct positioning for mammography. The federal government and some states have already mandated this training for mammo-graphic technologists. During positioning, the technologist should inspect the patient's breasts and record her observations on the patient's information sheet to help the radiologist interpret the mammogram. The technologist should note the location of any previous biopsies and record the presence and location of skin moles, scars, and any other skin conditions that might project over the imaged glandular tissue. When the breast is lifted up to position it on the image receptor, the tissue along the periphery of the breast should be palpated and additional special views of any thickening or mass that would not be imaged on the routine two-view mammo-gram should be obtained.
30° Superolateral-to- 60° Mediolateral
Inferomedial Oblique (SIO) Oblique (MLO)
Left Breast Left Breast
30° Superolateral-to- 60° Mediolateral
Inferomedial Oblique (SIO) Oblique (MLO)
Fig. 2.6. For films to be interpreted correctly, it is necessary to label all images accurately and precisely. A full description of a view should include whether it is right or left breast, the angle of the image-receptor tray to the horizontal plane, and the direction of the x-ray beam.
The patient should stand during the mammographic examination unless a physical disability prevents her from doing so.4 When the technologist positions the breast, she should smooth out the skin of the breast to eliminate wrinkles (Figure 2.7). Since there is a small degree of latitude of angulation for placing the breast on the image receptor, the technologist should roll the breast in her hands, at slight angles from the intended view, to determine the angle at which the breast can be compressed to its thinnest (Figure 2.8). This maneuver, which helps prevent overlapped glandular tissue, is extremely important for performing every view, whether routine or specifically tailored.
One of mammography's important goals is imaging as much posterior glandular tissue as possible, even at the expense of seeing the nipple in profile. It is not necessary for the nipple to be in profile for every view. If the nipple is not in profile on either the CC or the
4While NCRP recognizes that a small percentage of breast cancers arise in male patients and that there are also a few male radiologic technologists performing mammography examinations, the Clinical Mammog-raphy section of this Report is written, in general, to reflect the predominant situation that the vast majority of mammography technologists and of mammography patients, in particular all of those enrolled in screening programs, are female.
ACR has chosen similar language for the Clinical Image Quality section of their Mammography Quality Control Manual (ACR, 1999).
oblique views, the technologist should perform a coned-down third view with the nipple in profile.
The one exception to this rule is a mammogram on a man. Male glandular tissue is almost always subareolar. The radiologist needs to see its relationship to the nipple.
For this reason, the technologist should carefully position a man for the CC and oblique views with the nipple in profile. If all the glandular tissue is not discernible on these two views, the technologist should perform a third oblique view without the nipple in profile.
For the standard CC view, the radiographic beam is directed from above and through the breast to the image receptor, which is positioned caudal to the breast. It is essential to see as much of the medial aspect as possible on the CC view because frequently a small central or medial lesion is visible only on this view (Figure 2.9). On the MLO view, denser lateral tissue will overlap the less dense medial tissue and may obscure a small mass. A lesion close to the sternum may slide out from under the compression device when the patient is being positioned for the MLO image, which is another reason for including as much medial tissue as possible on the CC view.
The patient should stand with her feet pointed towards the image receptor. The technologist may stand either laterally or medially to the breast being imaged. It is usually easier to pull the medial half of the breast onto the film from the lateral side (Figure 2.10). The patient should steady themselves by grasping the support bar with her contralateral hand. The patient should
loosely drop her ispilateral arm. After instructing the patient to relax her shoulders, the technologist should lift up the breast and then raise the film tray to the height of the elevated inframammary crease (Figure 2.10). Because the skin of the lower-half of the breast is more mobile than the upper half, the technologist can lift the breast quite high (Eklund and Cardenosa, 1992). Nevertheless, the technologist needs to be careful not to lift it too high, since an inferior lesion might not be included on the image (Figure 2.11). Conversely, if the position of the image receptor is too low, a superior lesion might not be imaged (Figure 2.12).
The technologist should then place her other arm behind the patient, hold the patient's opposite shoulder, and gently rotate the patient so that her sternum is as close to the film tray as possible.
The technologist can either move the patient's head or instruct the patient to move her head around the tube head toward the contralateral side (Figure 2.10). After placing the breast on the film tray, the technologist should again ask the patient to let her shoulders relax inferiorly to loosen the skin covering the upper chest wall (Figure 2.13). This assists the technologist in pulling as much of the upper half of the breast as possible onto the image receptor. To help in imaging the medial tissue, the technologist should lift the medial aspect of the opposite breast onto the image receptor (Figure 2.14). Next, the technologist grasps the lateral aspect of the breast and lifts as much of the tissue as possible onto the image receptor. The technologist needs to do this without rotating the patient's torso; otherwise, some medial tissue might rotate off the image receptor. Gently placing her hand behind the patient's back to prevent her from pulling back during compression, the technologist should then begin compressing the breast. If the skin overlying the breast is tight, the glandular tissue of the axillary tail often cannot be pulled onto the image receptor. In such instances, the technologist should not try to pull the upper outer portion of the breast onto the image receptor, because this tissue will swing medially, overlap the more sparse medial and central tissue, and might cover up a small cancer. If the CC view does not image the axillary tail and the axillary tail is overlapped on the oblique view, the technologist should perform an additional 20 to 30 degree oblique view. The technologist can pull back redundant tissue between the glandular tissue of the axillary tail and the axilla (Figure 2.15), because imaging this tissue on the CC view is unnecessary since the oblique view will image this area.
Bassett and colleagues (Bassett et al., 1993) found they could image the medial aspect of the pectoral muscle in 32 percent of their CC views (Figure 2.16). If the technologist questions whether this imaged tissue is a true mass, she should repeat the craniocudal view with the image receptor slightly angled obliquely in either direction from the CC view. The shape and size of the mass usually change, indicating that the pectoral muscle has produced the mass (Figure 2.17). A true mass does not change in either size or shape.
Because the MLO view images significantly more of the axillary tail and the posterior aspect of the breast (Lundgren, 1977) than the lateral view, it has replaced the lateral view as the complement
Fig. 2.11. This 60 y old woman's correctly performed right CC-view mammogram (A) demonstrated a posterior neodensity (arrow), which subsequently proved to be a carcinoma. This neodensity was not visible on her MLO view mammogram (B) but was perceptible on a lateral-view mammogram (C). When the CC-view mammogram was repeated with the inframammary crease deliberately raised too high (D), the lesion no longer was apparent (E) because the lower-half of the breast could not be stretched onto the image receptor. If the breast had been elevated too high on her original CC-view screening mammogram, both views would have completely missed this peripheral lesion.
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