Clinical Significance of US Artifacts

Abstract

Artifacts are frequently encountered at clinical US, and while some are unwanted, others may reveal valuable information related to the structure and composition of the underlying tissue. They are essential in making ultrasonography (US) a clinically useful imaging modality but also can lead to errors in image interpretation and can obscure diagnoses. Many of these artifacts can be understood as deviations from the assumptions made in generating the image. Therefore, understanding the physical basis of US image formation is critical to understanding US artifacts and thus proper image interpretation. This review is limited to gray-scale artifacts and is organized into discussions of beam- and resolution-related, location-related (ie, path and speed), and attenuation-related artifacts. Specifically, artifacts discussed include those related to physical mechanisms of spatial resolution, speckle, secondary lobes, reflection and reverberation, refraction, speed of sound, and attenuation. The underlying physical mechanisms and appearances are discussed, followed by real-world strategies to mitigate or accentuate these artifacts, depending on the clinical application. Relatively new US modes, such as spatial compounding, tissue harmonic imaging, and speckle reduction imaging, are now often standard in many imaging protocols; the effects of these modes on US artifacts are discussed. The ability of a radiologist to understand the fundamental physics of ultrasound, recognize common US artifacts, and provide recommendations for altering the imaging technique is essential for proper image interpretation, troubleshooting, and utilization of the full potential of this modality. RSNA, 2017.

Artifacts and Technical Restrictions in 2D Shear Wave Elastography

“…Secondly generated echoes will then reverse course along the same path. Since the ultrasound system makes the false assumption of a rectilinear course, the final image will be reconstructed beyond the reflective interface, thus giving a mirror artifact on both sides of the interface [21]. "Ghost" echoes may be located in the primary beam's axis or be laterally displaced.…”

Misdiagnosis or Missed Diagnosis: Digging Out the “Near-Field Clutter” Artifact in a Patient with Stroke

“…As can be appreciated, because of the random presence of multiple reflectors in the near field of the probe, including the scarred myocardial apex of our patient, multiple pathways be-tween the reflectors and the probe generate a stepladder reverberation, which in fact is similar to the well-known comet-tail and ring-down ultrasound artifacts. 3 Finally, the clutter in our patient is not generated by reverberations caused by interfering lung tissue, as this type of reverberation artifact fluctuates or displaces upon (forced) respiration, 7 which was not the case in our patient.…”

“…Although tissue-harmonic imaging (THI) 1 and improved probe design over the past decades have significantly reduced ultrasound artifacts, they nevertheless remain an important issue in daily clinical practice and may lead to misdiagnosis or missed diagnosis. 2,3 The near-field artifact in our patient has been designated in the past as NFC, and this may be particularly challenging, as it may mimic a thrombus. 4 Misdiagnosis may expose the patient to the unnecessary bleeding risk of anticoagulative therapy.…”

Angioleiomyoma of the Extremities: Findings on Ultrasonography and Magnetic Resonance Imaging

“…We found that most angioleiomyomas showed posterior acoustic enhancement; to our knowledge, this finding has rarely been described. Posterior acoustic enhancement (or increased through‐transmission) refers to the increased intensity of echoes relative to surrounding tissues occurring distal to a low‐attenuating structure . Although posterior acoustic enhancement is seen in many cystic tumors, it is important to consider that it is frequently seen in angioleiomyomas.…”