Chapter 7: Imaging Artifacts and Pitfalls

1A: Axial or depth direction (artifact below the actual structure)

Characteristics features

How to avoid

Reverberation

• More distant than true object
• Parallel motion
• Distal fading
• Include comet tail artifact in this group

• Decrease gain
• Alternative imaging planes or modalities2
• M-mode to differentiate intimal flap from reverberation

Ring-down

• Equivalent to B lines (from pleural line)
• Straight line through probe center
• No fading

• Pathological in lung if ≥ 3
• Physiological B lines change with position

Mirror-image artifacts

• More distant than true object
• Opposite motion
• Can occur with 2D, PWD and CFI

• Decrease gain
• Change scanning plane and incident angle

Acoustic shadowing

• Pie-like hypo- or anechogenic segment
• Distal to strong reflector, on straight line

• Alternative imaging planes

Acoustic enhancement

• Posterior enhance in fluid filled organs

• Alternative imaging planes and angles

1B: Lateral direction (artifact located to the side of the actual structure)

Refraction artifacts

• Double image
• Same distance from probe

• Change transducer angle and position
• Alternative imaging planes
• Avoid « refracting » structure

Beam width artifacts

• Same distance from probe
• True object/Doppler signal outside of imaging plane

• Adjust focal zone and reduce gain
• Alternative imaging planes

Side lobe artifacts

• Linear artifact from a strong reflector in side lobes, interpret as from central beam
• Symmetric at both sides of the object
• Same distance from probe (‘‘arc-like’’ in radial direction)

• Adjust focal zone
• Use harmonic imaging
• Alternative imaging planes

2) Interference by external equipment and devices

2A: External equipment

Unshielded electrical equip

• Appears only during electrocautery

• Newer US machines remove these

Aliasing

• Occurs when velocity of blood or tissue surpasses the maximum Nyquist limit

• Decreasing transducer frequency and depth
• Choose an anatomic structure with a velocity that does not exceed Nyquist limit

Click

• Normal component of a PWD or CWD image as valve open and close

Quadrature-Channel Cross Talk

• Two identical spectral Doppler signals on opposite sides of the baseline

• The real signal is the strongest

2D-Devices

US interference

• Presence of another US source 

• Removing extra ultrasound device

Near-field clutter

• Noise (‘‘clutter’’) in near field
• No relation with anatomic structures

• Apply CFI, reducing scale
• Alternative imaging planes

VAD

• Wave like artefact from the electromagnetic motor

• Removal of device when indicated

3) 3D artifacts

Stitching

• Incorrect juxtaposition at the interface of sequential subvolumes

• Hold respiration and motion
• Switch to single-beat acquisition

Dropout

• Poor echocardiographic signal strength from weak echoes
• Can interpret as holes or tears ²⁰

• Over set the gain
• Image surfaces perpendicular to US beam
• Adjust gain and use multiple plane

Blurring

• Indistinct edges of structures which appear thicker

• Use perspectives in which the 3D image is created using mostly the axial resolution

Blooming

• Metallic structures appear larger when intersected by US produce fringes extending beyond the borders of metallic devices/catheters

• Not correctable

Railroad-shaped

• Catheters with wide lumens two surfaces are perpendicular to US beam, producing strong echoes, while other two are tangential, producing very weak echoes

• Obtain most favorable perspective (i.e., ‘‘en face’’ view of the surface perpendicular to the beam), and increase compression to merge boundaries

Reverberation

• Multiple reflections of metallic

component of catheters may appear to lengthen the catheter

• Not correctable

Shadowing

• Inability of US to pass through strong reflecting catheters/devices

• Avoid shadowing by properly rotating/angulating the volumetric data set

Gain

• Gain variation may produce significant variation in the size of structures, which may appear smaller or larger

• Gain adjustment

¹US system assumptions are:
1-Pulses and echoes travel along a straight path
2-Echoes return to the transducer after a single reflection
3-Echoes originate from the main beam
4-Echoes travel at a uniform speed (1540 m/s)
5-Pulses and echoes are attenuated uniformly by all tissues (at 0.5 dB/cm/MHz)
2 Alternative imaging modalities include ICE, CT scan, or CMR.

Abbreviations: 2D, two-dimensional; 3D, three-dimensional; CFI, color flow imaging; CMR, cardiac magnetic resonance; CT, computed tomography; CWD, continuous-wave Doppler; ICE intracardiac echocardiography; PWD pulsed-wave Doppler; TGC, time gain compensation; US, ultrasound; VAD, ventricular assist devices. Adapted from Bertrand⁴⁴ Quien² and Faletra et al.¹⁷