artifacts in echocardiography

Artifacts in Echo

Dr Dilzith

Contents• Artifacts

• In 2D Echo

• In Doppler

• In Colour flow

• In TEE

Artifacts

1. Extraneous US signal that results in appearance of structures that

are not actually present

2. Failure to visualize structures that are present

3. An image of a structure that differs in size or shape or both from its

actual appearance

2-D Echo

Suboptimal Imaging• Cause is poor ultrasound tissue penetration

• Body habitus with interposition of high attenuation tissue. (Lung, Bone)• Increased distance ( Adipose tissue)

• THI can improve the image quality • TEE may be required

Acoustic Shadowing• Reflection of entire US signal by a

strong specular reflector• Ex:• prosthetic valves.• Heavily calcified Native structures • Contrast containing blood also

produces shadowing.

• Try alternate acoustic window or different transthoracic view

• TEE may be required

Reverberations• Multiple linear high amplitude

echo signals originating from two strong specular reflectors

• Results in back and forth reflection

• Typically, a reverberation artifact that originates from a fixed reflector will not move with the motion of the heart.

Beam Width• Superimposition of structures within the beam profile (Including side

lobes) into a single tomographic image• Can be due to strong reflectors at the edge of a larger beam will be

superimposed on structures in central zone.• Can be due to consequences of varying lateral resolution

Range Ambiguity• Echo from previous pulse reaches transducer on next cycle.

• Results in appearance of deep structures closer to the transducer than their actual

location

• Second type of range ambiguity is a double image on the vertical axis

• Echoes being re-reflected by a structure close to the transducer (ex. Rib)

• Results in signal received twice normal and can form double image.

• Range ambiguity can be eliminated by decreasing depth or adjusting the transducer

position

Refraction• Deviation of US signal from a

straight path along the scan line.• Appearance of side-by-side

double image• Commonly seen in parasternal

short axis view

Near Field clutter• Also called as “Ringdown artefact”• Arises from high amplitude oscillations

of the piezoelectric elements.• The artifact is troublesome when trying

to identify structures that are particularly close to the transducer• Greatly reduced in modern day systems

Doppler Artifacts

Velocity Underestimation• Due to non-parallel intercept angle between the US beam and

direction of blood flow

Signal Aliasing• Inability to measure maximum

velocity• Can be due to non-laminar

disturbed flow and high velocity laminar flow• Can be controlled by using low-

frequency, change Nyquist limit and use of CW doppler

Beam width • Superimposition of Doppler signals from adjacent

flows

• Beam width artifacts in Doppler imaging can be

clinically useful.

• beam width artifact often has less desirable effects.

Ex: a large sample volume may hinder

one's ability to distinguish aortic stenosis from mitral

regurgitation.

Range ambiguity• It’s a speed of sound artefact• Doppler signals from more than one depth along the US

beam are recorded.1.misregistration of targets2.distortion of interfaces3.errors in size and4.defocusing of the ultrasound beam.• It can be reduced by decreasing the depth or width to the

minimum required

Mirror Imaging• Also called as “Cross Talk”• Such mirror images are usually less

intense but similar in most other features to the actual signal.• can be reduced by decreasing the

power output or gain and optimizing the alignment of the Doppler beam with the flow direction.

Transit Time Effect• Change in the velocity of the US wave as it passes through a moving

medium results in overestimation of Doppler shifts• Results in broadening of the velocity range at a given time point.

(Blurring on the vertical axis)

Colour Doppler

Shadowing and GhostingShadowing:-• may occur, masking color flow information beyond strong reflectors.Ghosting:-• is a phenomenon in which brief patterns of color are painted over

large regions of the image. • Ghosts are usually a solid color (either red or blue) and bleed into the

tissue area of the image.• These are produced by the motion of strong reflectors such as

prosthetic valves.

Background Noise• Also called as Gain setting artifacts• Too much gain can create a mosaic distribution of color signals

throughout the image. • Too little gain eliminates all but the strongest Doppler signals and may

lead to significant underestimation.• Gain level just below the random background noise can optimize the

flow signal

Other artifacts..• Intercept angle: Change in

colour (or absence at 90 degrees) due to angle between flowstream and US beam• Aliasing: On colour flow results

in “wraparound” of the velocity signal.• Electronic interference:

Instrument dependent

In TEE

Multiple reflections

Misplaced reflections

Thank You!!