17.2 Breast Ultrasound and Breast MRI

What "basic knowledge" means on this exam

Under Procedures 2.C, ARRT lists breast ultrasound and breast MRI immediately after screening and diagnostic mammography. Footnote 4 is explicit: the mammographer is expected to have basic knowledge of these examinations and procedures. That is not permission to skip them, and it is not an invitation to memorize the entire ARRT Breast Sonography or Magnetic Resonance Imaging outlines. You need indications, what each test can and cannot do next to mammography, and the safety concepts that change scheduling.

Contrast-enhanced mammography (CEM) appears in some breast-imaging practices as a supplemental tool or as an option when MRI cannot be performed. It is not a listed item on the 2025 ARRT Mammography content specifications. Do not study CEM as if it were a required mammography-exam fact.

Breast ultrasound: the problem-solving partner

Breast ultrasound uses high-frequency sound waves. It does not use ionizing radiation, it is real-time, and it is the usual way to decide whether a mass is a simple cyst or a solid (or complex) lesion. Simple cysts are typically anechoic, circumscribed, and show posterior acoustic enhancement. Solid or complex masses need a sonographic BI-RADS-style assessment and often biopsy if they are suspicious.

High-yield reasons a mammography patient is sent to ultrasound:

• A palpable lump or focal thickening, including a finding you marked with a BB or skin marker
• Characterization of a mammographic mass, asymmetry, or distortion that may have a sonographic correlate
• Dense breasts, when a clinician orders supplemental ultrasound because mammographic sensitivity falls in heterogeneously or extremely dense tissue
• Biopsy guidance for a sonographically visible target (ultrasound-guided core biopsy is detailed under interventional procedures; you still need to know that ultrasound is the guidance method when the lesion is seen on US)

Ultrasound is also the usual first imaging test for a palpable mass in younger patients. ACR appropriateness commonly starts with ultrasound under age 30, uses ultrasound or mammography at 30–39, and pairs mammography with ultrasound at 40 and older. You are not expected to recast every appropriateness table as a math problem. You are expected to know that a 25-year-old with a lump is not "screening mammography first," and a 55-year-old with a lump is diagnostic mammography plus ultrasound, not a screening four-view.

What ultrasound does not do:

• It is not a standalone replacement for mammography in average-risk screening. Mammography (2D and/or DBT) remains the screening backbone because it depicts calcifications and some architectural findings ultrasound will miss.
• It is a weak test for isolated calcifications. Those stay on the mammography and magnification pathway and often toward stereotactic sampling rather than ultrasound.
• Handheld targeted ultrasound is operator-dependent. A negative scan of the wrong quadrant does not clear a mammographic finding elsewhere.

Automated whole-breast ultrasound (ABUS) can be offered as an optional dense-breast adjunct in some programs. ARRT's Breast Sonography documents treat automated whole-breast ultrasound as correlative content in that discipline (including updates effective September 1, 2026). For the mammography exam, remember ABUS only as an optional supplement — not as core mammographic positioning, technique, or QC.

Breast MRI: high-risk adjunct and problem solver

Breast MRI uses a strong magnetic field, radiofrequency pulses, and, for cancer imaging, intravenous gadolinium contrast. The American Cancer Society (ACS) is direct on a sentence you should be able to teach: if MRI is used for screening, it is in addition to, not instead of, a screening mammogram, because MRI can still miss some cancers — especially certain calcifications and ductal carcinoma in situ (DCIS) — that mammography finds.

High-risk screening

ACS recommends annual breast MRI plus mammography, typically beginning around age 30, for women at high risk, including:

• Lifetime risk of about 20% to 25% or greater on a family-history-based model
• Known BRCA1 or BRCA2 pathogenic variant
• Untested first-degree relative of a BRCA carrier
• Chest radiation before age 30 (classic example: Hodgkin lymphoma treatment in adolescence)
• Li-Fraumeni, Cowden, or Bannayan-Riley-Ruvalcaba syndrome, or a first-degree relative with one of these syndromes

ACS recommends against MRI screening when lifetime risk is under 15%. It finds insufficient evidence to recommend for or against MRI solely for dense breasts or for a personal history of atypia without a high calculated risk.

The American College of Radiology (ACR) also treats annual MRI plus mammography as the high-risk package, often starting MRI at 25 to 30 depending on the risk type, with mammography start age tailored to the same risk. ACR has additionally supported MRI for some women with a personal history of breast cancer (for example, diagnosis before age 50 or dense breasts after treatment). For ARRT Mammography, the durable line is: high-risk screening is mammography plus MRI, not MRI alone.

Diagnostic, staging, and implant roles

Beyond screening, recognize these MRI jobs:

• Extent of disease in a newly diagnosed cancer (additional ipsilateral disease, unsuspected contralateral cancer, surgical planning)
• Occult primary: axillary metastatic adenocarcinoma with no finding on mammography or ultrasound
• Silicone implant integrity (silent rupture): typically a non-contrast implant protocol using silicone-specific sequences. Intracapsular rupture may show a collapsed shell (often taught as "linguine" morphology); extracapsular silicone is a different search. Saline implant deflation is usually clinical; silent silicone rupture is the MRI or ultrasound question.
• Problem-solving when mammography and ultrasound remain inconclusive and the question is cancer, not a simple cyst

Contrast is the difference between a cancer MRI and an implant-integrity MRI. Cancer protocols use gadolinium so enhancing lesions can be described by morphology and kinetics. Implant-integrity protocols are looking for silicone, not enhancement.

Contraindications and limits (conceptual)

You do not need an MRI safety officer's binder memorized. You do need to know why a patient might be screened, delayed, or sent to another test:

• Device and metal safety: non-MRI-conditional pacemakers, certain aneurysm clips, ferromagnetic foreign bodies, and some implants require a formal MRI-safety review. "MRI-conditional" is not "walk in without screening."
• Gadolinium: a prior allergic-type reaction, or renal-function concerns because of nephrogenic systemic fibrosis risk in severe kidney disease, can block or modify contrast.
• Pregnancy: gadolinium is generally avoided unless the information is essential.
• Claustrophobia and bore limits: some patients cannot complete a prone breast MRI. That may lead a clinician to another supplemental test; it is not a reason for you to invent mammography-only high-risk screening.

MRI is also time-intensive and more likely than mammography to generate additional workups. That is why ACS drew a high-risk line instead of offering MRI to every average-risk dense-breast screening patient.

Keep both modalities in the ARRT mammography box: you correlate, schedule, and explain them. You are not being tested as if you held the Breast Sonography or MRI credential. You will still miss Procedures 2.C items if you cannot say when each test is indicated, when it is not, and when contrast is part of the study.