Color or power Doppler is a useful method to quickly assess vascularity. Breast vascularity is low, so one should be aware of methods to optimize the color or power Doppler. Generally, this means that one is using a color or power Doppler frequency slightly lower than the gray scale frequency and the focal zone adjusted at the correct depth. The filter and scale should be low. The Doppler gain is optimized by initially increasing the gain until the entire screen is filled with color and then by slowly reducing the gain until the color appears only within pulsating vascular structures. If no color is detected using these methods, then the sample volume size should be increased. Increasing the sample volume size reduces color resolution. The color may “bleed” and be demonstrated outside of the vessel walls. Color or power Doppler is useful to delineate vessels or highly vascular structures such as arteriovenous malformations. This Doppler technique is also useful to clarify whether a hypoechoic or anechoic mass is cystic or solid (Fig. 2–3; also see Section 3 Case 32).
Figure 2–2. (A). Left MLO mammogram. (B). Left CC mammogram. (C). Left MLO spot magnification mammogram. (A–C). In the left upper outer quadrant, there is a small irregular mass (circle). (D). Left antiradial (8 MHz) breast sonogram: Sonographic examination of the mammographic mass with a low-contrast technique poorly demonstrates the mass (arrows). The hypoechogenicity of the mass blends into the surrounding fat. (E). Left antiradial (8 MHz) breast sonogram: Sonographic examination of the same location as Figure 2–2D with high-contrast technique greatly improves the conspicuity of the mass. This mass is a mucinous carcinoma.
Figure 2–3. (A). Right MLO mammogram. (B). Right CC mammogram. (A,B). The patient and the breast surgeon have identified some small palpable lumps at the 9:00 position of the right breast. The lumps are arranged in a linear pattern. The left breast has similar lumps that are less conspicuous. Bilateral mammograms are normal. (C). Right radial breast sonogram: Gray scale sonographic examination of the palpable lumps shows normal tissue. (D). Right radial breast sonogram: Color Doppler examination of the palpable lumps demonstrates that the lumps are due to the lateral blood vessels of the breast. Each lump corresponds to the superficial curve of the blood vessel (arrows) (see Color Plate 2–3D).
Dynamic clips are useful to document vascularity and to demonstrate the spatial relationship of multiple lesions. Dynamic clips are the ideal method to show color flow in pseudoaneurysms or intravenous contrast enhancement of solid masses. Until high-resolution three-dimensional (3-D) imaging is universally available, dynamic clips are an excellent way to demonstrate the relationship of multiple cysts to a solid mass or to show debris or calcifications moving within a complex cyst.
Wide field of view compound imaging is sometimes useful to document larger masses or the relationship of multiple masses in the same plane. The wider field of view provides observers with more landmarks so cross correlation with mammography and magnetic resonance imaging (MRI) may be easier.
Newer sonographic techniques that may have more applications in the future include 3D imaging and harmonic imaging. Like compound imaging, 3-D imaging may produce a wide field of view that would be similar to a mammogram or magnetic resonance image. In the future, 3-D imaging may also allow surgeons and patients to better appreciate the location and size of sonographic findings and facilitate surgical planning.
Harmonic imaging may improve image resolution and increase both gray scale and color Doppler sensitivity for intravenous sonographic contrast agents. These contrast agents may improve both vascular and gray scale characterization of masses.
Approach to a Palpable Mass
In many breast centers, palpable masses are the most common reason for a breast sonogram. Therefore, it is important that sonographic breast imagers learn how to palpate breasts. Usually, the patient will be able to identify the palpable lump. When the patient locates the lump, the breast imager should confirm the presence of the lump by palpating the area identified by the patient. Even if the lump is obvious, the imager should scan the lump and reconfirm the location of the lump by moving a finger into the scan plane. If the imager cannot detect the lump or if the patient is not sure of the exact location of the lump, then palpation of the entire quadrant is useful. By palpating a larger area, one is able to detect asymmetries within the region. Finally, if palpating the quadrant isn't helpful, then one may palpate the comparable area in the opposite breast. Commonly, the parenchymal pattern of patients is symmetric, so the physical exam is also symmetric. By palpating the corresponding contralateral quadrant, one may detect abnormal asymmetries. This technique is particularly useful with malignancies that are commonly difficult to feel such as lobular carcinoma.
Cross Correlation of Sonographic and Mammographic Image
To accurately, efficiently, and confidently sonographically identify a mammographic abnormality, the personnel who perform the breast sonographic examination should be familiar with mammographic imaging. Furthermore, the ultrasound examiner should be able to review the mammogram and identify internal landmarks that can be cross correlated with the ultrasound. Finally, by confirming the mammographic landmarks sonographically, the examiner should be able to pinpoint the location of the mammographic abnormality in the breast with ultrasound and consequently be able to explain the etiology of the puzzling mammographic finding.
Unfortunately, sometimes the ultrasound examiner does not attempt to closely cross correlate anatomically the ultrasound examination with the mammogram. In some cases, the examiner does not attempt to correlate the exams because he or she does not routinely interpret mammograms and is uncomfortable reviewing mammograms. However, more common reasons for lack of close cross correlation include the following: (1) The sonographic image has a small field of view compared with the mammographic global field of view. (2) The patient position for an ultrasound examination is completely different than the position for the mammographic examination. Therefore, the position of a breast mass for these exams appears extremely different. (3) Even if one places the patient in the same position, the difference in technology between ultrasound and mammography creates different orientations of tissue visualization. (4) Unlike other organs, the breast does not have a uniform or constant normal anatomy. The breasts of different individuals have different breast architecture. Furthermore, some individuals have a right breast that exhibits a pattern different from the left breast. Finally, the breasts of many individuals change with age.
As a result of the reasons stated above, ultrasound examiners commonly ignore internal breast anatomic landmarks and estimate the location of the mammographic abnormality using external landmarks. The most commonly used systems are the “O'clock” method and the quadrant method. The O'clock method views the breast as a circular clock with the nipple in the center of the circle: 12:00 is directly above the nipple; 3:00 is to the left of the nipple; 6:00 is below the nipple; 9:00 is to the right of the nipple. The quadrant method divides the breast into four parts or quadrants. These quadrants are defined by drawing a horizontal and a vertical line through the nipple. The quadrants label four regions of the breast: upper outer quadrant, upper inner quadrant, lower outer quadrant, and lower inner quadrant.
There are several problems with using external anatomic landmarks for locating mammographic abnormalities: (1) Mammographic estimation of location is not accurate and may be difficult to determine if the abnormality is only on one view; (2) The change in patient position between the mammogram and the ultrasound commonly results in changes in the relative position of internal breast structures compared to external landmarks; (3) The external breast position of a handheld transducer does not correlate to a specific internal imaging position.
Estimating location on a mammogram is commonly inaccurate as the standard mammographic views are the craniocaudal (horizontal) and mediolateral oblique views. The greatest source of error is related to the mediolateral oblique