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Should not be misinterpreted as a dislocated perforated wire into the left ventricular cavity Movie Clip A The theoretical genesis of a mirror artifact animation in Movie Clip 4. B Parasternal long axis image showing a mirror artefact below the pericardium-lung interface red arrow , moving images in Movie Clip 5.

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Comet-tail reverberations below the pericardium due to the strongly reflecting lung interface can be observed as well. A mirror artifact typically appears below a strong reflective surface that acts much as a mirror does with light, producing a duplicate image behind the mirror of the real structures in front of the mirror; the mirrored images move in the opposite direction from the mirror as do the real structures 3 , These intervening objects reflect the waves back to the strong reflector, which in turn sends them back to the transducer.

Due to the assumption of wave propagation — that all the returning sound comes from objects in the initial direction of the sound beam - the scanner displays these objects below the strong reflector, at a distance equal to the distance between strong reflector and the true intervening objects. The most common strong specular reflector that causes mirror artifacts is the lung, best appreciated in the parasternal long-axis view Figure 3—B and apical 4-chamber view on transthoracic echocardiograms and in the mid-esophageal view of the descending thoracic aorta on transesophageal echocardiograms.

Mirror artifacts are usually easy to identify in two-dimensional images as a copy of structures located above a reflective surface. However, the three-dimensional shape of a reflective surface can sometimes mirror structures that are not located in the respective scanning plane, thereby complicating correct interpretation Spectral and color Doppler flow is mirrored as well due to the mirroring mechanism, further enhancing confusion of two adjacent vessels instead of one Figure D.

A special case of Doppler flow mirroring is so-called pseudo-MR in mechanical mitral valve prostheses due to mirroring of left ventricular outflow tract LVOT flow as will be discussed below 17 — A Reverberation artifact of mitral valve leaflet at exactly twice the distance from the probe, presenting as a wire in the left ventricular cavity Movie Clip C Transseptal guiding catheter during pulmonary vein isolation procedure presenting with a series of closely-spaced reverberations arrowheads due to reflections at the upper and lower side of the hollow catheter and one reverberation at twice the distance to the probe due to reflection at the transducer itself.

Notice the mirroring of the color flow in the mirror image as well, the mechanism being similar i. E Reverberation artifact in the left atrial appendage mimicking thrombus. G Side lobe artifact arrow from a calcified sinotubular junction arrowhead extending in the ascending aorta Movie Clip 21 should not be misinterpreted as a dissection flap. H Similarly, a reverberation in the ascending aorta might be misinterpreted as being a dissection flap.

A The theoretical genesis of a refraction artifact. B Double image of the aorta full arrowhead in a subcostal short-axis image of the heart, due to refraction of the ultrasound beam at perihepatic fatty tissue arrow. A Swann-Ganz catheter in the right ventricular outflow tract is doubled as well empty arrowhead. Moving images in Movie Clip 7.

These artifacts mostly occur in subcostal and parasternal imaging planes, with costal cartilage, fascial structures and fat, and pleural and pericardial surfaces acting as the medium inducing refraction of the ultrasound beam 21 , Structures behind an ultrasound lens may not be visible in that plane because the sound beam never reaches them and instead they are overwritten by the duplicate image of a nearby structure.

Adjusting the probe to avoid the lens or using alternative imaging windows are strategies to avoid the double image and assess the structures that were shadowed. In routine clinical practice refraction artifacts are typically recognizable because they create impossible anatomic relations, such as intersecting duplicated images of the mitral valve in long-axis imaging 22 , or the aortic root and left ventricle in short-axis imaging Figure 4 However in apical long-axis images more subtle doubling of the ventricular wall can occur due to refraction at the apex pericardium, fat complicating assessment of left ventricular dimensions and ejection fraction.

Adjusting the image settings and changing the probe angulation are possible strategies to avoid refraction in such cases 7. A The genesis of a side lobe artifact. B Parasternal long axis view with linear side lobe artifact arrow in the aorta ascendens due to a calcified sinotubular junction arrowhead.


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This artifact can sometime be misinterpreted as a dissection flap. C Parasternal long axis view of a healthy patient with strongly reflecting pericardium, causing a side lobe artifact in the left atrium arrow. In moving images Movie Clip 9 comet-tail reverberations, acoustic shadowing, near field clutter and a mirror image of the mitral valve leaflets can be observed as well. However, when this side lobe energy is reflected by a strong reflector wires, calcifications, pericardium in its path, these reflections are interpreted by the scanner as originating from the central beam As the transducer scans the imaging window by sweeping in a radial direction, numerous side lobe artifacts can be generated on both sides of the true reflector.

When the true reflector is bright and wide, these multiple side lobe images can overlap and visually merge, producing a linear arc-like artifact at a radial distance of the transducer 2 , Clinical recognition is important to avoid misdiagnosis of thrombi or vegetations generated by side lobe artifacts from highly reflective annular or prosthetic interfaces.

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In addition, side lobe artifacts from highly reflective aortic sinotubular junctions could be mistaken for aortic dissection flaps Figure 5—B. A The lateral width and elevation width of the ultrasound beam respectively cause a decrease in lateral resolution and the occurrence of beam width artifacts. The blue squared object within the scanning plane is correctly identified in the center of the beam.

However, due to the elevation width of the beam, the green circular object outside of the imaging plane is incorrectly positioned within the scanning plane. B Parasternal short-axis image of pulmonary arteries showing unexplained turbulent flow into the left pulmonary artery LPA, arrow , without evidence of shunting or stenosis. C Tilting of the probe out of the scanning plane reveals massive mitral regurgitation into the left atrium picked up by the beam as if occurring in the pulmonary artery. In most of the current machines and transducers, the ultrasound beam is able to focus only over a limited distance and increasingly diverges beyond from the focal zone 8.

Within the imaging plane the wider the beam is, the poorer the lateral resolution, i. Objects or blood flow out of the imaging plane but within the elevation width of the beam are interpreted as if located in the imaging plane, sometimes leading to diagnostic dilemmas and enigmas 24 — In clinical practice, beam width artifacts from highly reflective annular or prosthetic interfaces could be confused for thrombi or vegetations similar to side lobe artifacts.

Furthermore, it is important to recognize out-of-plane artifacts displaying strong Doppler signals in adjacent structures, e. This is especially relevant in case an apical ventricular thrombus is suspected Figure 7 , Movie Clip The introduction of harmonic imaging and the technologic advances in transducer design have already reduced the occurrence of this type of artifact.

In contrast to a thrombus, clutter is unaffected by ventricular wall motion and appears to pass through the wall. Moving images Movie Clip 10 show normal apical myocardial kinetics, and no relationship between clutter and myocardial motion. Cardiac devices therefore complicate the interpretation of echocardiographic images Figure 8 , and demand careful examination of the device and surrounding structures from different imaging views. In addition, devices with specific geometric designs can sometimes generate uncommon artifacts due to the interaction between ultrasound waves and the device geometry, bearing in mind the physical principle that for a specular reflector the angle of reflection equals the angle of incidence.

The figure-of-eight artifact Figure 9 obtained when imaging a percutaneous disc occluder is a typical example of such a device-specific artifact based on the physics of ultrasound reflection. This artifact occurs in disc occluders e. Our mathematical analysis previously demonstrated that those locations constitute a figure-of-eight, explaining the artifact that is frequently seen in apical 5-chamber view after LAA closure using the Amplatzer Cardiac Plug 29 , 30 , but also in off-axis parasternal long-axis views following ASD or PFO closure procedures In contrast, three-dimensional echocardiographic imaging with the beam propagating perpendicular to the plane of the device frontal probe position will correctly display the rounded extent of the occluder A Three-dimensional echocardiography of an Amplatzer Cardiac Plug after successful implantation in left atrial appendage.

B Apical 5-chamber view in the same patient, with an Amplatzer Cardiac Plug in the correct position presenting as a figure-of-eight Movie Clip C Apical 3-chamber view slightly off-axis in a patient following left atrial appendage occlusion. Central image Because of the epitrochoidal mesh geometry of the disc occluders, sound is reflected back to the probe only by the small segments of mesh with fibers orthogonal to the beam direction. These align in a figure-of-eight as shown by the green lines on the figure. Adapted from Bertrand et al. In spectral and color Doppler imaging, similar physical principles and limitations apply to the incident and scattered Doppler-shifted sound waves, and thus similar imaging artifacts can be observed in Doppler imaging 32 — Mirror artifacts and beam width artifacts are the most relevant Doppler artifacts.

In mirror artifacts the velocity signal above the reflector is mirrored as well, and interpreted by the transducer as originating from below the reflector due the assumption of wave propagation Figure 4 Therefore, both color and spectral Doppler signals remain detectable in the mirror image Figure D. Misdiagnosis of severe prosthetic MR has important consequences, as Faletra et al. B—C extend to spectral Doppler signals as well. A spuriously elevated TR jet velocity in a patient with medially directed MR wrongfully included in the continuous wave beam interrogating the TR jet leads to an incorrect diagnosis of pulmonary hypertension and potentially results in MR surgery for the mistaken pulmonary hypertension indication.

On the other hand, Doppler color flow imaging can be a powerful tool to help distinguish artifacts; for example, an apparent mass in the LAA that is otherwise filled with flow of a normal and undisturbed velocity. In apical hypertrophic cardiomyopathy, paucity of intramyocardial specular reflectors can produce the spurious impression of an apical aneurysm to be distinguished from the occasional true small outpouching of the obstructed apical blood pool — an artifactual dropout that can be remedied by color Doppler showing a narrow apical flow stream or left ventricular echo contrast opacification.

It is important to note that artifacts generated by structural reverberations and mirror images will not accelerate or disturb surrounding flows in any way; however, flow may not necessarily be displayed in the same pixels as a structural artifact because the scanner must select structural versus flow signals for display based on its tissue priority algorithm and the strength of the respective signals. Although this overview article is mainly focused on routine transthoracic echocardiography, the above artifacts are frequently encountered in transesophageal echocardiography as well.

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Reverberations, mirror artifacts and side lobe artifacts in particular play an important role in these settings due to the often linear aspect of the artifact resembling a dissection flap in the ascending or descending aorta 43 — 47 , or mimicking a thrombus in the LAA 48 , Historically, lack of recognition of artifacts in transesophageal echocardiography for aortic dissection created the impression that echocardiography lacked specificity for the diagnosis relative to other modalities such as magnetic resonance imaging 50 — a misimpression that can be eliminated by understanding the nature of artifacts.

Furthermore, in the early years of transesophageal imaging, occasional patients were being operated on because of artifacts — now largely eliminated by our understanding. Even so, to date patients are still being anticoagulated rather than immediately cardioverted for atrial fibrillation because of image artifacts.

This again shows the importance of understanding the physics of ultrasound reflection, refraction, and beam formation — a practical consequence of that knowledge. Table 2 summarizes some typical features of true structures versus artifacts, which can aid in the investigation of uncommon echocardiographic findings and offer clues toward a correct interpretation both in transthoracic and transesophageal imaging. One central principle to recall for all forms of artifact is that true structures cannot pass through cardiac or vascular walls, and are typically well-defined even thrombi, with their mildly fluctuant borders , unlikely the sometimes nebulous borders of artifacts.

Furthermore, true structures are seen in multiple imaging views whereas artifacts typically cannot be reproduced from alternative probe positions e. In addition, unlike true anatomic structures, artifacts will not accelerate or disturb surrounding color Doppler flow in any way. In case an artifact is suspected, a logical physical explanation for its presence in that location should be explored based on the above principles.

Careful examination from multiple imaging views, with optimized imaging settings and with application of color Doppler flow is mandatory in cases of doubt.

In addition to artifacts, it is important to recognize causes of apparently abnormal myocardial motion such as pseudodyskinesis, in which external compression of the LV diaphragmatic surface causes characteristic diastolic flattening, while the normal systolic contraction causes outward epicardial motion — similar to paradoxical septal motion when the IVS is flattened in RV volume overload Image artifacts in clinical echocardiography are related to the physics of reflection and refraction reverberation, acoustic shadowing, mirror artifact, refraction artifact or to ultrasound beam properties and equipment side lobe artifact, beam width artifact, near field clutter.

A physical explanation of artifact mechanisms and a recognition of the most common image artifacts encountered in routine clinical practice is important for it will provide clues to correct diagnosis and approaches to avoid the production of artifacts. Movie Clip 18 —Reverberation artifact in the left atrial appendage mimicking thrombus. Movie Clip 19 — Alternate imaging plane of the left atrial appendage of Movie Clip 18 confirms the presence of a reverberation artifact of the warfarin ridge.

Movie Clip 2 — Reverberation artifact of aortic calcification mimicking left atrial mass.

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Movie Clip 20 — Color flow imaging in the left atrial appendage of Movie Clip 18 — 19 shows no thrombus is present. Movie Clip 21 — Transesophageal image of the ascending aorta with side lobe artifact from calcified sinotubular junction mimicking aortic dissection. Movie Clip 3 — Stepladder of reverberations below aortic calcification. Movie Clip 5 — Mirror artifact in parasternal long axis window.

Movie Clip 7 — Double image of aorta and Swann-Ganz catheter in subcostal short axis view. Movie Clip 10 — Near field clutter mimicking left ventricular apical thrombus. Movie Clip 9 — Parasternal long axis window showing side lobe artifact of the strong reflecting pericardium in left atrium , comet-tail reverberations, acoustic shadowing, near field clutter, and a mirror image of the mitral valve below the pericardium.

Movie Clip 11 — Mechanical mitral valve prosthesis causing multiple reverberations, comet-tails and acoustic shadowing below the prosthesis. Movie Clip 12 — Parasternal short-axis image of a linear arc-like side lobe artifact caused by the presence of a defibrillator wire in right ventricle. The artifact crosses the anatomical borders interventricular septum. Movie Clip 13 — The figure-of-eight artifact in the apical 5-chamber view in a patient following successful left atrial appendage closure with the Amplatzer Cardiac Plug.

Movie Clip 14 — The figure-of-eight artifact caused by a PFO occluder in parasternal off-axis image of the interatrial septum.