Standard projections and positioning
Two main projections are used for a full assessment of the breast:
- Mediolateral oblique projection (mediolateral oblique, MLO). This is the only projection that allows visualization of all breast tissue in a single image. When properly positioned, the nipple is in profile (nipple in profile), the inframammary fold (inframammary angle) is visible, and the pectoralis major muscle (pectoralis major) crosses the posterior edge at an angle of 25–30 degrees, reaching the level of the nipple.
- Craniocaudal projection (craniocaudal, CC). The X-ray beam is directed from top to bottom. The breast is pulled forward and upward, with compression applied from above. The image displays the medial and most of the lateral tissue (except for the axillary tail). The pectoral muscle is visible in approximately 30% of women.
Additional projections
If standard images are insufficient, additional techniques are used to address specific clinical tasks:
- CC projection rotation. Helps to better examine the medial or lateral aspects.
- True lateral view (true lateral view). The machine is rotated by 90 degrees (mediolateral or lateromedial beam direction). It helps distinguish tissue overlap from a true lesion and is used for wire localisation.
- Paddle views (paddle views). Targeted compression of an area using a special paddle to differentiate tissue overlap from real tumors and to assess the margins of a lesion.
- Magnification views (magnification views). Used primarily to evaluate microcalcifications. A typical sign of benign calcifications in the lateral projection is the "teacups" sign (teacups).
The role of compression and the presence of implants
Breast compression (breast compression) is a mandatory condition for a high-quality image. It reduces dynamic and geometric blurring, lowers the radiation dose (by decreasing tissue thickness), and improves contrast by suppressing scattered radiation. In addition, compression helps separate overlapping structures and more accurately assess lesion density (cysts compress easier than dense carcinomas).
In patients with silicone (silicon) or saline (saline) implants, standard mammography is difficult because they are radiopaque (radio-opaque) and obscure the breast tissue. In such cases, the Eklund technique (Eklund technique) is used: the implant is displaced posteriorly behind the compression paddle to maximize the capture of glandular tissue. No cases of implant rupture due to mammography have been reported.
Digital breast tomosynthesis (DBT)
Standard 2D mammography has limitations: tissue superposition can hide a tumor or, conversely, create the appearance of pathology, especially in dense breasts.
Digital breast tomosynthesis (digital breast tomosynthesis) solves this problem by creating thin cross-sectional slices from multiple low-dose exposures taken at different angles. The slices are viewed as a movie clip, which eliminates the influence of overlying and underlying tissues.
Tomosynthesis replaces spot compression views during workup and is actively being introduced into screening because it increases cancer detection rates and reduces the recall rate.
Briefly: answers to topical questions
What types of breast parenchymal density are identified according to the BI-RADS classification?
Four types of mammographic density are distinguished, designated by letters from A to D according to the ACR classification.
- Types C and D indicate high mammographic density.
High density is a high-risk factor for breast cancer, reduces the sensitivity of mammography, and requires additional examination: breast ultrasound, contrast-enhanced MRI, or tomosynthesis.
Which radiological features of microcalcifications indicate their malignant nature?
Malignant microcalcifications have a number of specific radiological characteristics.
- Distribution — grouped into clustered formations, with a ductal, linear, or segmental distribution.
- Morphology — they vary in size and shape, being pleomorphic.
- Shape — in high-grade ductal carcinoma in situ, they are classically rod-shaped and branched.
Such calcifications are also known as casting or comedo microcalcifications.
On which day of the menstrual cycle is it optimal to perform routine screening mammography?
The exact day of the menstrual cycle for routine screening mammography is not specified in the sources.
What direct and indirect radiological signs are characteristic of breast cancer on a mammogram?
The sources do not divide breast cancer signs into direct and indirect, but the following characteristic radiological manifestations on a mammogram are described:
- Masses — an ill-defined mass, an area of asymmetrically dense tissue, spiculated masses, as well as new or enlarging multi-lobulated masses (multi-lobulated masses).
- Structural changes — architectural distortions and an abnormal trabecular pattern.
- Calcifications — the presence of malignant microcalcifications.
- Skin changes — skin and trabecular thickening (in inflammatory breast cancer).
Class and exam questions
Why is it mandatory to take two projections?
A pathology clearly visible in one projection (e.g., MLO) may be completely invisible in another (e.g., CC) due to tissue overlap or the location of the lesion in blind spots.
How is the correctness of MLO performance evaluated?
The criteria include clear visualization of the inframammary fold, the nipple in profile, and correct display of the pectoralis major muscle (crossing the image at the correct angle and reaching the level of the nipple).
Is the radiation dose in mammography dangerous?
The average dose is about 3 mGy, which equals approximately two months of natural background radiation. The ratio of lives saved to the potential risk of radiation-induced cancer is 300:1.
What else to study on this topic
- X-ray spectra and anode materials (molybdenum, tungsten)
- Physics of contrast formation in mammography
- Features of microcalcification detection
- Comparison of iterative reconstruction and filtered back projection in tomosynthesis
- Prospective studies on DBT screening efficacy (STORM, Oslo, Malmo)
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