Mammography

Introduction to Mammography

Lesson Objectives

• Basics of mammography.
• Learn about screening mammography.
• How are mammography images obtained?
• Effect of breast density on interpreting mammograms.
• Basics of interpreting mammograms.
• Basics of digital mammography and tomosynthesis.

Basics of Mammography

• A mammogram is a low dose x-ray of the breast used to screen for breast cancer.
• Mammography can also be used in a diagnostic setting such as:
• Further characterize an abnormality seen on a screening mammogram.
• Evaluate a patient or provider's concern found on a self or physical exam.

• Screening mammography is governed by federal law by The Mammography Quality Standards Act (MQSA).
• Set a minimum standard that all hospitals preforming screening mammography must comply to.
• American College of Radiology uses BI-RADS, which standardizes image terminology, report organization, assessment structure and classification system used to risk stratify and help determine next steps in diagnosing and following lesions.

Screening Mammography

• Why screen? About 1 in 8 U.S. women will develop invasive breast cancer in their lifetime.
• Breast cancer has the second highest cancer death rate in women, second to lung carcinoma.
• Early detection of breast cancer can lead to:
• Greater range of treatment options
• Less extensive surgery
• Better treatment outcomes as lower stage cancers have better long term survival.

*Chart (survival, treatment, cost, stage) removed pending source

Regular screening mammography began in the 1980s and the breast cancer death rate has decreased by ~35% since.

Chart accompanying above removed pending source

• Mixed interpretation of the data has resulted in many organizations having different screening guidelines.
• American College of Surgeon (ACS) Guidelines: Age 40-44: Women may begin annual screening, age 45-54: Annual screen, Age 55+: yearly or every 2 years, as long as >10yrs life expectancy.
• United States Preventive Services Task Force (USPSTF): Biennial screening for ages 50-74. Ages 40-49 should be individual choice.
• American College of Radiology (ACR) and American College of Obstetricians and Gynecologists (ACOG): Annual at age 40
• Just to name a few!

How Images Are Obtained

• Breast is compressed between a plastic compression plate and the X-ray detector.
• Why compression is used:
• Compression helps spread out the fibroglandular tissue making it easier for radiologists to detect abnormalities.
• Limits motion artifact which also helps aid in detection.
• More compression means less radiation exposure required to produce optimal images.
• Unit can rotate 360 degrees to obtain different views.
• Cranial-Caudal (CC) and Mediolateral Oblique (MLO) are the standard views obtained on a routine screening mammogram.

Standard Mammography Views 

Effects of Breast Density on Mammography

• Varying differences in breast density are seen, which can play a big role in the ability to detect lesions.
• Four main categories of breast densities are assigned to each case.
• Almost entirely fatty
• Scattered density
• Heterogeneously dense
• Extremely dense

Test your knowledge

Placeholder quiz - we may want to craft a different / better question.

Basics of Interpreting Mammograms

• First step is to determine if the study is technically adequate.
• Nipple should be in profile in at least one view.
• Image should be free of motion or artifact.
• Adequate breast tissue should be included.
• Posterior nipple line: line drawn from posterior nipple on MLO view should intersect with the pectoralis muscle. Line is also measure on CC view, measurements should be within 1.0cm of each other.
• Inclusion of the inframammary fold on the MLO view. 
• Inclusion of retroglandular fat

Digital Mammography

• Film was used up until 2000, until FDA approved use of digital mammography.
• No longer use actual film as the detector, rather a digital detector converts photons into a digital signal.
• Digital signal can be viewed on high resolution monitors instead of older light boxes.
• Digital mammography has nearly completely replaced film at this point.
• Digital mammography also allows use of tomosynthesis (3-D mammography).
• Thought to help aid in detection of subtle lesions.

Tomosynthesis