3/12/2023 0 Comments Comet tail artifactThe resonant vibrations detected by the ultrasound transducer are displayed as bright vertical lines extending deep to the trapped fluid. Ultrasound waves hit a pocket of trapped fluid, the sound waves resonate within the fluid, and a continuous sound wave is transmitted back to the transducer. The source of ring-down artifact is a small pocket of fluid trapped by surrounding air bubbles. Ring-down artifact is similar to comet-tail artifact but is produced by a different mechanism ( Figure 6.3 ). Comet-tail artifacts can be seen in normal and abnormal lungs and are described in more detail in Chapter 9. This “stacking” of bright horizontal lines spaced very close together with progressively decreasing width creates an image of bright tapering vertical lines ( Video 6.1 ). After several reflections, the amplitude of returning echoes is decreased, which is displayed as narrowing of the lines compared to the original echo. Comet tails classically appear as bright vertical lines with a tapering shape. This improves image quality by decreasing artifacts, improving spatial resolution, and increasing penetration.Ī particular type of reverberation artifact known as comet-tail artifact is produced when sound waves are reflected between two highly reflective surfaces in very close proximity. It transmits only twice the original frequency, and it narrows the width of the ultrasound beam. Tissue harmonic imaging (THI) can reduce artifacts by filtering the fundamental (original) frequencies used. Similarly, decreasing the distance between the object of interest and ultrasound transducer can reduce reverberation artifact. Because reverberation occurs when the ultrasound beam crosses highly reflective structures perpendicularly, adjusting the transducer’s angle of incidence may lessen the presence of reverberation. Reverberation artifacts can be useful in assessing tissue characteristics, but they can hinder adequate image acquisition of deeper structures.Ī-lines are reverberation artifact seen in lungs due to pleural reflections.Ī few techniques can be used to minimize the effects of reverberation artifact. This specific reverberation artifact is caused by multiple reflections between the highly reflective pleural surface and skin-transducer interface. A classic example of reverberation artifact occurs in the normal lung at the pleural surface, called A-lines ( Figures 6.1 and 6.2 ). Reverberation artifact occurs at tissue interfaces with large differences in acoustic impedance. If there is no difference in acoustic impedance between two different tissues, there will be no reflection of sound waves, but if there is a significant difference in acoustic impedance, there will be reflection of a large proportion of sound waves back to the transducer. The amount of sound waves reflected at a tissue interface is directly proportional to the difference in acoustic impedance between two adjacent tissues. This measure of resistance to passage of ultrasound waves through a material or tissue is called acoustic impedance. Tissue interfaces where there is a large difference in speed of sound between the two tissues are highly reflective. Reverberation artifact at the pleural surface produces a series of horizontal lines called A-lines. This chapter reviews some of the most common artifacts encountered in point-of-care ultrasound. Most artifacts can be categorized into one of four categories based on the underlying mechanism: artifacts of wave propagation, beam characteristics, velocity errors, and attenuation. The speed of sound is constant in all types of human tissue (1540 m/s), and the attenuation, or decrease in energy, of ultrasound echoes is uniform.Īrtifacts frequently provide insight into tissue makeup and are diagnostic for certain pathologies, such as gallstones and pulmonary edema. Ultrasound waves always travel in a straight path and return after only one reflection. Ultrasound echoes returning to the transducer originate from a uniform, single ultrasound beam. Barring malfunctioning equipment, artifacts originate from erroneous ultrasound signaling that occurs in biologic tissues due to violation of one or more of the following assumptions: Providers should have a basic understanding of the physical principles of ultrasound artifacts to improve acquisition and interpretation of ultrasound images at the bedside. Artifacts are false images, or parts of images, that do not represent true anatomic structures.
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