Physics and Artifacts Publications

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GENERAL ARTIFACT REVIEWS

• An easy-to-read pictorial article review of the physical basis and appearance of gray-scale artifacts related to the ultrasound beam, propagation of sound through tissue, sound reflection, echo detection, and machine assumptions. Artifacts covered include side/grating lobe, reverberation, comet tail, ring-down, mirror image, speed displacement, refraction, attenuation, shadowing, and increased through-transmission artifacts.
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• Feldman MK, Katyal S, Blackwood MS. US artifacts. Radiographics. 2009 Jul-Aug;29(4):1179-89.

• An article review of basic physical properties of ultrasound waves, how an image is generated, ultrasound probes and their frequencies, orientation, depth and gain; also reviews artifacts, how they are generated and how to incorporate artifacts in the overall ultrasound interpretation.
• Schmidt GA, Schraufnagel D. Introduction to ATS seminars: intensive care ultrasound. Ann Am Thorac Soc. 2013 Oct;10(5):538-9.

TISSUE-SPECIFIC ARTIFACTS

• While fat is classically described as hyperechoic on ultrasound, this paper describes pictorial representations of HYPOechoic fat collections from the most common locations (perinephric space, anterior abdominal wall, breast, pericardium and within ovarian teratomas).
• Spencer GM, Rubens DJ, Roach DJ. Hypoechoic fat: a sonographic pitfall. AJR Am J Roentgenol. 1995 May;164(5):1277-80. doi: 10.2214/ajr.164.5.7717247. PMID: 7717247.

• A prospective study reviewing imaging artifacts that are generated from metallic medical instruments (eg, stainless steel rods) and how artifact can be altered with use of different external roughening and coating in vivo and in vitro. A highlight of this paper is its descriptions of reverberation, ring-down, resonance, side-lobe, range ambiguity, mirror, and shadowing artifacts produced by the instruments.
• Huang J, Triedman JK, Vasilyev NV, Suematsu Y, Cleveland RO, Dupont PE. Imaging artifacts of medical instruments in ultrasound-guided interventions. J Ultrasound Med. 2007 Oct;26(10):1303-22. doi: 10.7863/jum.2007.26.10.1303. PMID: 17901134.

• A retrospective analysis of the morphology and mechanism behind interstitial lung disease. Methodology provides definitions and pictorial collage of comet tail artifact, interstitial-alveolar syndrome, interstitial syndrome, ring-down artifact, septal syndrome, ultrasound lung comets, “white lung,” and resonance artifacts.
• Soldati G, Copetti R, Sher S. Sonographic interstitial syndrome: the sound of lung water. J Ultrasound Med. 2009 Feb;28(2):163-74. doi: 10.7863/jum.2009.28.2.163. PMID: 19168766.

• An article review that defines multiple lung ultrasound artifacts (mirror, range ambiguity, ring-down/resonance, A-lines, B-lines, E-lines, and slice thickness), the assumptions the machine makes that contributes to these artifacts, the correlation of findings to pathophysiology, and techniques to optimize settings to improve diagnostic accuracy.
• Easy Read
• Dietrich CF, Mathis G, Blaivas M, Volpicelli G, Seibel A, Atkinson NS, Cui XW, Mei F, Schreiber-Dietrich D, Yi D. Lung artefacts and their use. Med Ultrason. 2016 Dec 5;18(4):488-499. doi: 10.11152/mu-878. PMID: 27981283.

• A case series reviewing 5 manifestations of pathologic air (air in a location it shouldn’t be) detected by ultrasound and needing emergent intervention/consultation (pneumothorax, pneumoperitoneum, Fournier’s gangrene, subcutaneous emphysema and pneumomediastinum). Addresses the characteristic appearance of air (“dirty shadowing”) on ultrasound, with images for each of the five cases.
• Easy Read.
• Buttar S, Cooper D Jr, Olivieri P, Barca M, Drake AB, Ku M, Rose G, Siadecki SD, Saul T. Air and its Sonographic Appearance: Understanding the Artifacts. J Emerg Med. 2017 Aug;53(2):241-247. doi: 10.1016/j.jemermed.2017.01.054. Epub 2017 Mar 31. PMID: 28372830.

DOPPLER

• A review of basic concepts of the physics of Doppler sonography; the reasoning for the use of Doppler investigation; discusses instrumentation including continuous-wave, pulsed-wave, duplex and color-flow Doppler equipment; identifies limitations and artifacts introduced by Doppler equipment.
• Nelson TR, Pretorius DH. The Doppler signal: where does it come from and what does it mean? AJR Am J Roentgenol. 1988 Sep;151(3):439-47. doi: 10.2214/ajr.151.3.439. PMID: 2970215.

• An article review of the physics behind the principles of Doppler imaging, with emphasis on the uses and limitations from a cardiology standpoint. Includes simple explanations and sketches of Doppler tracings according to the flow of blood within chambers, across valves, and in great vessels, spanning normal anatomic flow, regurgitation, and stenosis.
• Nishimura RA, Miller FA Jr, Callahan MJ, Benassi RC, Seward JB, Tajik AJ. Doppler echocardiography: theory, instrumentation, technique, and application. Mayo Clin Proc. 1985 May;60(5):321-43. doi: 10.1016/s0025-6196(12)60540-0. PMID: 3887049.

• The third review paper in a series of articles on ultrasound physics and instrumentation in the Echo Rounds section. Aliasing (produced by pulse wave Doppler) causes inaccurate representation of the speed and direction of blood flow. This review discusses the limitations of pulse wave Doppler technology, explains the mechanism behind aliasing, and troubleshoots how it can be avoided [eg, use lower ultrasound frequencies, increasing the pulse repetition frequency (PRF), changing to continuous wave Doppler, and reducing the depth of the sample].
• Pellett AA, Tolar WG, Merwin DG, Kerut EK. Doppler aliasing. Echocardiography. 2005 Jul;22(6):540-3. doi: 10.1111/j.1540-8175.2005.40099.x. PMID: 15966943.

DOPPLER (CARDIAC)

• A prospective study evaluating right ventricular (RV) systolic pressures through use of continuous wave Doppler ultrasound (and the modified Bernoulli equation). This study demonstrated that using continuous wave Doppler on tricuspid regurgitation jets of 54 patients with elevated RV pressures accurately predicted right ventricular systolic pressures when compared to catheterization values performed within 24 hours of Doppler study.
• Yock PG, Popp RL. Noninvasive estimation of right ventricular systolic pressure by Doppler ultrasound in patients with tricuspid regurgitation. Circulation. 1984 Oct;70(4):657-62. doi: 10.1161/01.cir.70.4.657. PMID: 6478568.

DOPPLER (VESSELS)

• An article review with 11 high resolution color images demonstrating sonographic findings of the normal artery as well as how it would change in the setting of a thromboembolism, atherosclerosis, bypass graft occlusion, dissection, trauma, compartment syndrome, hyperemia, pseudoaneurysm, and arteriovenous fistula. The spectral Doppler waveforms encountered in each are labeled with easy-to-understand captions.
• Nuffer Z, Rupasov A, Bekal N, Murtha J, Bhatt S. Spectral Doppler ultrasound of peripheral arteries: a pictorial review. Clin Imaging. 2017 Nov-Dec;46:91-97. doi: 10.1016/j.clinimag.2017.07.007. Epub 2017 Jul 16. PMID: 28755582.

• An article review explaining the physics behind Doppler ultrasound and some of the more common mathematical equations applied in routine clinical examinations; also descriptions and pictorial demonstrations of normal versus abnormal spectral Doppler signature waveforms of vessels in the neck, abdomen, pelvis and fetus. Comprehensive, with 35 figures.
• Moderately difficult read, but good reference.
• Wood MM, Romine LE, Lee YK, Richman KM, O’Boyle MK, Paz DA, Chu PK, Pretorius DH. Spectral Doppler signature waveforms in ultrasonography: a review of normal and abnormal waveforms. Ultrasound Q. 2010 Jun;26(2):83-99. doi: 10.1097/RUQ.0b013e3181dcbf67. PMID: 20498564.

SMOKE

• This prospective study used spontaneous echo contrast in an in-vitro model to determine whether echocardiographic “smoke” has thromboembolic characteristics. Average signal intensities were compared and found no significant difference between flow with spontaneous echo contrast and flow without echoes (p=0.71). Injection of embolic material compared with normal saline did not generate a smoke-like image but did cause a higher than average signal intensity than the flow with spontaneous contrast (p=0.001). The article concludes that smoke-like echo at low flow states does not produce material capable of embolizing into the systemic circulation. This paper challenges previous studies that have shown presence of smoke to be associated with greater incidence of left atrial thrombi.
• Yang Y, Grosset DG, Li Q, Lees KR. Identification of echocardiographic “smoke” in a bench model with transcranial Doppler ultrasound. Stroke. 2000 Apr;31(4):907-14. doi: 10.1161/01.str.31.4.907. PMID: 10753997.

• An article review of spontaneous left atrial echo contrast (LA smoke). LA smoke is present in almost all patients with LA thrombus and is associated with previous embolic events in many patient populations; its detection on ultrasound arises from increased amplitude of backscatter from red cell aggregates.  LA smoke is a marker of a hypercoagulable state and can assist in selecting patients with atrial fibrillation or mitral stenosis who may benefit from anticoagulant therapy.
• Easy Read
• Black IW. Spontaneous echo contrast: where there’s smoke there’s fire. Echocardiography. 2000 May;17(4):373-82. doi: 10.1111/j.1540-8175.2000.tb01153.x. PMID: 10979010.

TWINKLE

• An in-vitro investigation of the twinkling artifact that occurs when color Doppler is applied to kidney stones. This review found that suppression of twinkling artifact with elevated static pressure and return of the twinkling artifact when the pressure was released suggests the presence of bubbles on the stone surface is the mechanism that gives rise to twinkling artifact.
• Difficult Read
• Lu W, Sapozhnikov OA, Bailey MR, Kaczkowski PJ, Crum LA. Evidence for trapped surface bubbles as the cause for the twinkling artifact in ultrasound imaging. Ultrasound Med Biol. 2013 Jun;39(6):1026-38. doi: 10.1016/j.ultrasmedbio.2013.01.011. Epub 2013 Apr 3. PMID: 23562014; PMCID: PMC3646957.

• A prospective study investigating the hypothesis that twinkling artifacts are created by bubbles on the surface of kidney stones (crevice bubble hypothesis). Experimentation with 5 different compositions exposed to acoustic rarefaction pulses or hypobaric static pressure was performed while simultaneously capturing their appearance by high-speed photography and ultrasound imaging. This study concluded that hyperbaric and hypobaric static pressures did modify twinkling artifact for rough-surfaced stones but was inadequate for smoother stones; ultimately, yielding support of the crevice bubble hypothesis.
• Easy read.
• Simon JC, Sapozhnikov OA, Kreider W, Breshock M, Williams JC, Bailey MR. The role of trapped bubbles in kidney stone detection with the color Doppler ultrasound twinkling artifact. Phys Med Biol. 2018 Jan 9;63(2):025011. doi: 10.1088/1361-6560/aa9a2f. PMID: 29131810; PMCID: PMC5791757.

• An article review of the usefulness of twinkling artifact in the diagnosis of calculi, especially those too small to generate shadowing; proper knowledge and use of this sign allows the radiologist to properly use the information to increase test sensitivity  
• Hirsch MS, Palavecino TB, Leon BR. Color doppler twinkling artifact: a misunderstood and useful sign. Revista Chilena de Radiología. Vol. 17 No 2, año 2011; 82-84.

BIOEFFECTS OF ULTRASOUND

• Defines thermal index, as well as guidelines (thermal index and exposure time limits) to minimize thermal injury from ultrasound.
• Harris GR, Church CC, Dalecki D, Ziskin MC, Bagley JE; American Institute of Ultrasound in Medicine; Health Canada; British Medical Ultrasound Society. Comparison of Thermal Safety Practice Guidelines for Diagnostic Ultrasound Exposures. Ultrasound Med Biol. 2016 Feb;42(2):345-57. doi: 10.1016/j.ultrasmedbio.2015.09.016. Epub 2015 Nov 28. PMID: 26626492.

• Overview and definitions of ALARA, Mechanical Index (MI), and Thermal Index (TI).
• Nelson TR, Fowlkes JB, Abramowicz JS, Church CC. Ultrasound biosafety considerations for the practicing sonographer and sonologist. J Ultrasound Med. 2009 Feb;28(2):139-50. doi: 10.7863/jum.2009.28.2.139. PMID: 19168764.

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