An ultrasound machine assumes a single pulse of ultrasound enters the tissues, is reflected off a structure, and returns directly to the transducer for interpretation. When this does not occur ultrasound artefacts are created.
Not infrequently and ultrasound pulse encounters two parallel reflective surfaces lying perpendicular to its path. Some of the pulse becomes caught between the two surfaces, bouncing forwards and backwards before returning in increments, between each reverberation, to the transducer. This reverberation causes a repetitive artefact on the ultrasound image.
The appearance of the reverberation artefact depends on:
- The size of the two reflective surfaces
- The distance between the two reflective surfaces (long vs short path reverberation artefacts)
- And how much ultrasound energy is lost – dissipated or attenuated, between each re-reflection.
Types of Reverberation Artefacts
- Long path reverberation artefact (A-lines in lung)
- Short path reverberation artefact (B-lines in lung; ringdown anywhere else!)
- Fatiguing short path reverberation artefact (Comet tails)