Bull's-eye Artifact in Breast SWE: How to Recognize
What is the bull's-eye artifact
In breast elastography, cysts exhibit specific patterns. One of them is the bull's-eye artifact: a round or oval elastogram where the central fluid appears soft with a surrounding stiff ring (Diagnostic Imaging: Breast, Berg & Leung, 2019).
Alongside the bull's-eye, a trilaminar pattern is described for cysts: the cyst appears stiff anteriorly, with 3–4 alternating stiff and soft layers posteriorly (Diagnostic Imaging: Breast, 2019).
Features of cysts in SWE
According to SWE data, simple cysts have characteristic features (Diagnostic Imaging: Breast, Berg & Leung, 2019):
| Feature | Characteristic |
|---|---|
| Color map | Cysts appear predominantly black or dark blue |
| Elastography values | < 2.6 m/s (20 kPa) |
| Wave propagation | Shear waves do not propagate in the fluid of a simple cyst |
The absence of shear wave propagation in the fluid is a key physical mechanism explaining the appearance of bull's-eye and trilaminar patterns.
Clinical significance
The identification of the bull's-eye artifact has practical value: it helps reduce the frequency of breast lesion biopsies (the utility of the "bull's-eye" artifact on breast elasticity imaging in reducing breast lesion biopsy rate — Barr RG, Lackey AE, Ultrasound Q 2011; 27:151–155). Recognizing this pattern allows for confident classification of the finding as cystic, avoiding invasive verification.
Methodological cautions
Elastographic patterns should be interpreted only after identifying the lesion in B-mode: first, determine the anatomical boundaries on the grayscale image (higher spatial resolution), then assess the stiffness distribution on the elastogram. The stiff halo may extend beyond the actual boundaries of the lesion, and the soft center may "hide" part of it, so boundaries are always interpreted in B-mode, and stiffness by the color map (according to the accepted methodology).
Frequently asked questions
What does the bull's-eye artifact look like on an elastogram?
A round or oval elastogram: the central fluid is soft, surrounded by a stiff ring (Diagnostic Imaging: Breast, 2019).
What SWE values are characteristic of a simple cyst?
Cysts appear predominantly black or dark blue, elastography values < 2.6 m/s (20 kPa); shear waves do not propagate in the fluid of a simple cyst (Diagnostic Imaging: Breast, 2019).
How does the bull's-eye differ from the trilaminar pattern?
Bull's-eye is a round elastogram with a soft center and stiff ring; trilaminar is a cyst stiff anteriorly with 3–4 alternating stiff and soft layers posteriorly (Diagnostic Imaging: Breast, 2019).
Why recognize this artifact?
It helps reduce the frequency of breast lesion biopsies by confirming the cystic nature of the finding (Barr RG, Lackey AE, Ultrasound Q 2011).
In what order should the lesion be evaluated — B-mode or elastogram?
First B-mode to determine boundaries, then elastogram to assess stiffness; the stiff halo may extend beyond the actual boundaries of the lesion (according to the accepted methodology).