BREAST ULTRASOUND IMAGING
Ultrasound imaging of the breast is primarily used to help diagnose breast lumps or other abnormalities found during a physical exam, mammogram or breast MRI.
WHY IS THE PROCEDURE PERFORMED?
Determining the nature of a breast abnormality (solid or cystic or both)
Abnormalities not visible with mammography may be identified, including some that may require biopsy
Ultrasound-guided biopsy
THE PROCEDURE ITSELF:
You will lie on your back on the examining table and may be asked to raise your arm above your head.
After you are positioned on the examination table, the radiologist or sonographer will apply a warm water-based gel to the area of the body being studied. The gel will help the transducer make secure contact with the body and eliminate air pockets between the transducer and the skin that can block the sound waves from passing into your body. The transducer is placed on the body and moved back and forth over the area of interest until the desired images are captured.
There is usually no discomfort from pressure as the transducer is pressed against the area being examined. However, if scanning is performed over an area of tenderness, you may feel pressure or minor pain from the transducer.
BASICS
WHAT IS SEEN:
1. CYSTS
Are classified as either simple, complex or complicated depending on their inner echogenicity.
SIMPLE CYSTS
Virtually no chance of containing malignancy.
Do not need to be aspirated unless they are causing discomfort or are preventing adequate mammographic compression and evaluation. Although malignancy inside the cyst itself is virtually unknown, carcinoma can occur in the immediate vicinity of a cyst, so the tissues surrounding it should be evaluated too.
Anechoic centre
Thin echogenic capsule
Enhanced through transmission
Thin edge shadows
COMPLEX AND COMPLICATED CYSTS
Those which are not simple cysts. Complicated cystic breast malignancies are extremely rare and usually have other features that are obviously malignant. The majority of non simple cysts fall within the broad spectrum of fibrocystic change. So the majority of them are non-worrisome. Complex cysts are those that have some potential to be associated with malignancy, they demonstrate at least one of three findings:
Thick walls
Thick seperations
Mural nodules
2. SOLID NODULES
All solid nodules should be considered worrisome and malignant findings sought, with findings recorded as being present or absent. If even single malignant feature is present, the nodule cannot be classified as benign. If no malignant features are found, specific benign features then need to be sought. Only if benign features are found, can the nodule then be classified as benign. If specific benign features are not found, the lesion should be classified as intermediate.
MALIGNANT FINDINGS
Spiculation (invasion of surrounding tissues and desmoplastic host response to the lesion. Alternating hypoechoic and hyperechoic lines that radiate out perpendicular to the surface of the nodule)
Taller-than-wide (generally associated with smaller malignancies, as they enlarge they tend to be wider than tall)
Angular margins (identical to the jagged or irregular margins seen on mammography. A single angle should be considered suspicious and should exclude the lesion from the probably benign.)
Markedly hypoechoic (compared with fat, suspicious)
Shadowing (suggests invasive malignancy, in approximately a third of malignant nodules, caused by the desmoplastic components of the tumour)
Calcifications (mammographically suspicious findings that have been applied to sonography, occur within the lumen of the ducts distended by DICS)
Duct extension (correlates with the presence of DCIS components of the tumour, best demonstrated when the scan plane is oriented parallel to the long axis of the mammary ducts in the region of the nodule)
Branch pattern
Microlobulation (lobulations that vary in number and distribution along the surface and within the nodule, their size correlates with the histologic grade of the tumour)
BENIGN FINDINGS
Pure and marked hyperechogenicity (interlobular stroll fibrous tissue)
Elliptical, wider-than-tall lesion shape
Three or fewer gentle lobulations
Thin, echogenic capsule
PITFALLS
Scanning with too light transducer pressure may result in artificial shadowing.
Scanning with too heavy transducer pressure may result in underlying lesions being obscured.
Scanning with too heavy transducer pressure while using colour or power Doppler may ablate blood flow.
Scanning a superficial area without the use of stand-off pad or gel can result in a lesion being missed secondary to partial volume artefact, particularly with older equipment.
Using breast ultrasound without performing mammographic correlation may result in non-visulaization of a suspected lesion.
LENGTH OF THE EXAM
About 30 minutes.
WHERE ELSE TO CHECK
If a suspicious lesion is found, the patient's axilla should also be evaluated for the presence of metastatic lesions or abnormal lymph nodes.
Is a suspicious lesion is identified, the entire breast should be evaluated for the presence of multifocal or multicentric disease.
When using ultrasound to evaluate asymmetric tissue density seen on mammography, the mirror image area of the contralateral side should be scanned for comparison, using a "split screen" image can be very effective in showing this comparison.
Sources:
Clinical sonography, Roger C. Sanders, Tom C. Winter
https://www.radiologyinfo.org/en/info.cfm?pg=breastus