Ultrasound Artifacts - Vocabulary Flashcards

Vocabulary flashcards covering core ultrasound artifact concepts and related imaging principles from the notes.

Artifact (ultrasound)

A defect or error in an ultrasound image caused by physics, equipment, assumptions, or operator error; reflections may be not real or improperly shaped, sized, positioned, or bright.

Reverberation artifact

Multiple echoes produced by sound bouncing between reflectors, causing repeated images along the beam path.

Comet tail

A reverberation artifact from hard, reflective objects where reflections are very close together and fade distally.

Ring down

Reverberation artifact caused by gas, producing a pattern similar to a comet tail.

Twinkle artifact

Color Doppler counterpart of comet tail; occurs behind highly reflective objects and can help distinguish stones from poor borders or shadows.

Shadowing

Hypoechoic or anechoic region distal to a strong attenuator such as stones, bone, or dense masses.

Edge shadow

Shadowing at the border of rounded structures due to beam refraction at the edge.

Enhancement (through-transmission)

Increased brightness distal to tissue with low attenuation, often seen behind cystic structures.

Focal enhancement

Hyperechoic band across the image caused by concentrated sound energy in the focal zone.

Side lobes

Weak images produced by energy outside the main beam from a single element; reduce lateral resolution.

Grating lobes

Lobes generated by array transducers, causing secondary images away from the main beam; mitigated by apodization and subdicing.

Beam width artifact

The beam is not perfectly straight; divergence can exceed convergence, causing objects to appear inside the area of interest; corrected by proper focal zone.

Slice thickness artifact

Also called section thickness or partial volume artifact; elevational thickness causes tissue in front of and behind the main axis to be superimposed, blurring the image.

Multipath artifact

Echoes take several paths back to the transducer, creating images at incorrect depths and reducing axial resolution.

Range ambiguity artifact

Echoes from an earlier pulse overlap with echoes from a newer pulse, distorting depth information and spatial resolution.

Propagation speed error artifact

Sound travels at a speed other than the assumed 1540 m/s, causing misplacement of structures; includes Step-off/ bayonet artifacts.

Step-off (bayonet) artifact

Apparent bending or discontinuity of a needle or structure due to propagation speed differences; best viewed from a different acoustic window or with compound imaging.

Refraction artifact

Beam bends at impedance boundaries, displacing reflectors; refracted image often appears beside the real image.

Mirror image artifact

A second image appears on the opposite side of a strong reflector (often the diaphragm) because of sound reflection creating a longer path.

Mirror image (illustration)

A duplicate image generated by reflection off a strong reflector, typically seen deeper than the real structure.

Noise artifact

Small-amplitude echoes from many sources leading to poor SNR; near field; grainy texture; can be reduced with harmonics.

Speckle artifact

Granular texture due to constructive/destructive interference; inherent to ultrasound and not removable; varies with settings and hardware.

Clutter artifact

Noise outside the beam’s main axis caused by side/grating lobes; Doppler clutter from vessel walls or myocardium can contaminate signals.

Wall motion artifact

Doppler clutter caused by motion of surrounding tissue; reduced with wall filters, without affecting large Doppler shifts.

Wall filter

Filter that rejects clutter from wall motion in Doppler imaging; may not affect high-velocity signals.

Color aliasing artifact

Color Doppler artifact from low PRF/scale; appears as abrupt color changes with no intermediate colors; mitigated by adjusting scale or using multiregion/vertical PRF changes.

Crosstalk artifact

Mirror Doppler spectrum with inverted signals below baseline; caused by high Doppler gain or Doppler angle near 90 degrees.

Axial resolution

Ability to distinguish two structures along the beam; roughly half the SPL; improves with higher frequency.

Lateral resolution

Ability to distinguish two structures perpendicular to the beam; roughly equal to beam width; varies with depth.

Temporal resolution artifact

Frame-rate-related blurring; higher frame rates yield smoother real-time images; improved by reducing depth, sector size, focal zones.

Spatial resolution artifact

Overall image detail; improved with high line density, appropriate depth, sector size, frequency, and focusing.

Harmonic imaging

Imaging using tissue harmonic frequencies to enhance image quality and reduce low-level echoes; often paired with rejection filtering.

Apodization

Weighting of transducer elements to reduce sidelobes and improve lateral resolution.

Subdicing

Dividing transducer elements into smaller subelements to reduce grating lobes and improve image quality.

1.5D array

A transducer array that improves elevational (slice) resolution compared to a 2D array.

Analog displays

CRT-based displays where spatial resolution depends on raster lines; HD displays can double resolution.

Digital displays

Displays where spatial resolution depends on pixel density; higher pixel density yields finer detail and less blocky images.