Imaging Artifacts
Ultrasound Assumptions
2D Imaging artifacts are causes by violation of several ultrasound assumptions. The table below describes this:
| Ultrasound Assumption | Artifact Generated |
|---|---|
Pulses and echoes travel in straight lines | Refraction |
Waves are infinitely thin or pulses extremely small | Beam width |
Echoes travel back to the transducer after a single reflection | Reverberation, mirror image |
Echoes originate from the main beam | Side lobe, grating lobe |
Speed of sound in tissues is constant | Refraction |
Attenuation is uniform by all tissues | Acoustic shadowing, enhancement |
Dealing With Artifacts
- Shadowing refers to hypoechoic or anechoic areas distal to a STRONG reflector. (eg rib shadows)
- Enhancement refers to hyperechoic areas distal to a WEAK reflector. (eg bladder or fluid filled cyst)
- Reverberation – Multiple duplicated images spaced at regular intervals. (eg. A-Lines)
- Refraction – Misregistration, ommision or duplication of an object.
- Mirror image – Duplicated image deep and equidistant from object
- Beam width – Lateral blurring of an image, 2 objects may appear as one.
- Side lobe – Blurring of rdges of image.
Most artifacts can be dealt with by moving the transducer so that the beam does not pass the reflector causing the issue. Scanning in 2 planes should remove artifacts. Optimizing, depth, gain and focal zone are helpful.
References
Imaging artifacts in echocardiography. Le et al. Anaesthesia & Analgesia 2016.