1. Correct Answer: D. With this artifact, an image will appear in the wrong location but at an appropriate distance within the main (central) ultrasound beam.

Rationale: Ultrasound beams leave the transducer and travel in straight lines with most energy concentrated along the main (central) beam. Some energy is also directed adjacent to the central beam, which can also create echoes that the machine could assume originate along the main (central) beam axis. This can make an image appear in the wrong lateral location, but with an appropriate distance from the transducer (side-lobe artifact). In Figure 14.6A, a highly reflective structure (solid black ellipse) is interacting with a side-lobe beam (red beam) that is adjacent to the primary beam (yellow), causing a false image artifact (dotted grey ellipse) being depicted in the primary central beam image. An example of a side-lobe artifact (white arrow) can be seen in the ultrasound image (Figure 14.6B), where a highly reflective structure (likely the wall of the structure) is causing an artifact to be seen in the lumen of this structure.

1. Baad M, Feng Lu Z, Reiser I, Paushter D. Clinical significance of US artifacts. Radiographics. 2017;37:1408-1423. doi:10.1148/rg.2017160175

2. Perrino AC, Reeves ST. Chapter 20: Common artifacts and pitfalls of clinical echocardiography. In: Perrino AC Jr, Reeves ST, eds. A Practical Approach to Transesophageal Echocardiography. 2nd ed. Lippincott, Williams & Wilkins; 2008:417-434.

3. Quien MM, Saric M. Ultrasound imaging artifacts: how to recognize them and how to avoid them. Echocardiography. 2018;35(9):1388-1401.

4. Rubin DN, Yazbek N, Garcia MJ, Stewart WJ, Thomas JD. Qualitative and quantitative effects of harmonic echocardiography imaging on endocardium edge definition and side-lobe artifacts. J Am Soc Echocardiogr. 2000;13(11):1012-1018.

2. Correct Answer: A. Shadowing

Rationale: The dark areas are caused by rib shadowing, as the sound is reflected back to the ultrasound transducer. The lung point occurs at the site of pneumothorax, and it is the point of transition pleural sliding to no sliding in B-mode or from seashore sign to barcode sign in M-mode. Reverberations off the pleural line appear as A-lines, which are horizontal and double the distance of the pleural from the transducer. Pulmonary edema will appear as B-lines, which is not the case in Figure 14.1.

1. Bertrand PB, Levine RA, Isselbacher EM, Vandervoort PM. Fact or artifact in two-dimensional echocardiography: avoiding misdiagnosis and missed diagnosis. J Am Soc Echocardiogr. 2016;29(5):381-391.

2. Zagzebski JA. Essentials of Ultrasound Physics. 1st ed. Elsevier; 1996.

3. Correct Answer: D. Electrocautery artifact

Rationale: Artifacts due to electrocautery are very common in the operating room. The artifact produced typically has a geometrically fan-shaped interference pattern, not resembling an anatomic structure. Pulmonary artery catheters can cause side-lobe artifacts in some situations but typically would not have the “fan-shaped” appearance noted in Figure 14.2. Air bubbles post bypass often appear as bright “bubbles” on an echocardiogram but usually are in a random pattern, often display collections in specific locations, and would be contained within areas of the heart that receive blood flow. Harmonic imaging typically reduces the incidence of artifacts, and Figure 14.2 is not indicative of harmonic imaging.

1. Quien MM, Saric M. Ultrasound imaging artifacts: how to recognize them and how to avoid them. Echocardiography. 2018 Sep;35(9):1388-1401.

4. Correct Answer: B. In general, tissue harmonic signals pass through the body wall once.

Rationale: In fundamental imaging, the ultrasound beam is emitted from the transducer and first passes through the body wall and a second time during its return to the transducer. Tissue harmonic signals are generated in the body tissue and only travel back to the transducer. The single pass through body tissue by harmonic signals leads to decreased scattering, distortion, reverberations, and other artifacts (including side lobes), although artifacts can still occur at times. Side-lobe artifacts are weaker pulses that rarely produce any harmonics.

1. Rubin DN, Yazbek N, Garcia MJ, Stewart WJ, Thomas JD. Qualitative and quantitative effects of harmonic echocardiography imaging on endocardium edge definition and side-lobe artifacts. J Am Soc Echocardiogr. 2000;13(11):1012-1018.

2. Turner SP, Monaghan MJ. Tissue harmonic imaging for standard left ventricular measurements: fundamentally flawed? Eur J Echocardiogr. 2006;7(1):9-15.

5. Correct Answer: C. Increase the transducer frequency

Rationale: Typically, a ventricular thrombus develops in areas of severe wall motion abnormality and may have definable borders. To facilitate diagnosis, they can be further characterized by decreasing the depth, increasing the transducer frequency, and using multiple views (image planes). Contrast agents can also help distinguish thrombus from artifact, but the mechanical index should be decreased in this situation to minimize bubble destruction.

1. Rubin DN, Yazbek N, Garcia MJ, Stewart WJ, Thomas JD. Qualitative and quantitative effects of harmonic echocardiography imaging on endocardium edge definition and side-lobe artifacts. J Am Soc Echocardiogr. 2000;13(11):1012-1018.

2. Whalley GA, Gamble GD, Walsh HJ, Sharpe N, Doughty RN. Quantitative evaluation of regional endocardial visualisation with second harmonic imaging and contrast left ventricular opacification in heart failure patients. Eur J Echocardiogr. 2005;6(2):134-143.

6. Correct Answer: C. Reverberation artifacts

Rationale: The lines shown in Figure 14.3 are A-lines, which is a normal finding. A-lines are reverberation artifacts from the pleural line. Reverberation artifacts occur when the echo returning to the transducer is of significant magnitude. It is partially reflected at the transducer surface and redirected toward the interface. The second reflection (reverberation) is interpreted by the transducer as a second interface. Additional reverberations correspond to additional round trips of the sound use between the transducer and the interface. The first echo and the reverberating echoes are all equidistant.

B-lines are longitudinal comet-tail artifacts originating from the pleura. B-lines can indicate interstitial edema. Barcode (stratosphere) sign is present in pneumothorax when the lung is imaged in M-mode.

1. Feldman MK, Katyal S, Blackwood MS. US artifacts. Radiographics. 2009;29:1179-1189.

2. Scanlan KA. Sonographic artifacts and their origins. AJR Am J Roentgenol. 1991;156(6):1267-1272.

7. Correct Answer: C. Range ambiguity occurs when first pulse echoes of deep structures return to the transducer after the second pulse has been emitted

Rationale: The PRF helps determine the correct imaging of deep structures. As imaging depth increases, the PRF decreases, which helps to limit range ambiguity by allowing the first impulse to return to the transducer before the next impulse is emitted. As an example, if the initial impulse returns from an out-of-image distant structure after the second impulse is emitted, the time delay will be counted from the second impulse (or most recent) and the true object distance will be misregistered. Thus, a range ambiguity artifact in this situation would incorrectly place the distant structure closer to the transducer than its true location in this situation. By increasing the image depth and thus decreasing the PRF appropriately for a particular depth, the “listening time” of the transducer is increased which allows the initial impulse to return to the transducer before sending another impulse too soon.

1. Baad M, Lu ZF, Reiser I, Paushter D. Clinical significance of US artifacts. Radiographics. 2017;37:1408-1423. doi:10.1148/rg.2017160175

2. Naganuma H, Ishida H, Nagai H, Ogawa M, Ohyama Y. Range-ambiguity artifact in abdominal ultrasound. J Med Ultrason. 2019;46(3):317-324.

3. Perrino AC, Reeves ST. Chapter 20: Common artifacts and pitfalls of clinical echocardiography. In: A Practical Approach to Transesophageal Echocardiography. 417-434.