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Double aorta artifact in sonography – a diagnostic challenge

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ABSTRACT

The double aorta artifact was described and studied thoroughly twenty-five years ago. Despite this, it is still not commonly known today and can cause diagnostic difficulty. Total aortic duplication can be considered an anatomic defect whilst partial duplication mimics aortic dissection. In the literature, this artifact has been compared with a very rare anomaly, i.e. the occurrence of two aortas in one patient. Currently, however, the differentiation of this artifact from abdominal aortic dissection seems to be of greater significance. The double aorta image occurs when ultrasound waves encounter prismatic fat tissue of the anterior abdominal wall. This artifact is more frequently observed in children and athletic young adults since the structure of this anatomic region in these individuals is conductive to the occurrence of this phenomenon. Moreover, it can be observed more often when curved transducers are used. Due to all these factors, an ultrasound beam undergoes greater refraction and make the artifact clearer. This phenomenon is usually easily recognizable and avoidable, but it sometimes might cause diagnostic difficulty. Obtaining an image of double abdominal vessels on ultrasound examination in transverse sections requires further inspection of the aorta in a different (sagittal) plane. This is not always possible due to poor patient preparation for scanning. Symmetrical flow on Doppler sonography is a typical feature of this artifact. Finally, magnetic resonance imaging or computed tomography can be considered to rule out a pathology.

No MeSH data available.


Related in: MedlinePlus

A beam (continuous line) sent by the transducer (G) crosses the superficial fat tissue and rectus abdominis muscle (M), and refracts medially on prismatic slow-conductive deep fat tissue (T). The base of the prism is made by the edge of the liver. Subsequently, ultrasounds reach the aorta (A) through soft tissues. Produced echoes undergo identical refraction (continuous line) on their way back to the probe. The monitor shows two vessels (Ar). They are located on a straight line created by the emitted beam (dashed/dotted line) (1, 4, 11). They are observed to the left and right from the medially situated genuine aorta (A). Duplication concerns not only the aorta, but also all structures located on the way of ultrasounds undergoing refraction. This image is clearer distally from the probe since alleged images are then separated by a greater distance. An abnormal presentation of the margin of the vertebral body located behind the aorta (visible from below) frequently confirms the presence of the artifact rather than genuine duplication(3)
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f0001: A beam (continuous line) sent by the transducer (G) crosses the superficial fat tissue and rectus abdominis muscle (M), and refracts medially on prismatic slow-conductive deep fat tissue (T). The base of the prism is made by the edge of the liver. Subsequently, ultrasounds reach the aorta (A) through soft tissues. Produced echoes undergo identical refraction (continuous line) on their way back to the probe. The monitor shows two vessels (Ar). They are located on a straight line created by the emitted beam (dashed/dotted line) (1, 4, 11). They are observed to the left and right from the medially situated genuine aorta (A). Duplication concerns not only the aorta, but also all structures located on the way of ultrasounds undergoing refraction. This image is clearer distally from the probe since alleged images are then separated by a greater distance. An abnormal presentation of the margin of the vertebral body located behind the aorta (visible from below) frequently confirms the presence of the artifact rather than genuine duplication(3)

Mentions: An ultrasound image of double aorta occurs when an ultrasound beam is refracted in an adequate way from abdominal wall structures. The rectus abdominis muscles and fat tissue between them can create an acoustic prism that refracts ultrasounds(3, 4, 10, 11). This phenomenon was studied and described in 1990 by Vandeman, but it is still not commonly known and can cause diagnostic difficulty to less experienced ultrasonographers. This artifact more frequently occurs in young athletic individuals(3, 11). Refraction occurs at the border of centers with different acoustic properties (Snell’s law: sin α2/sin α1 = V2/V1). The greater the speed of sound between tissues, the greater the refraction of an ultrasound beam. Ultrasound wave refraction creates an image of the viewed structure in a false location (Fig. 1). The greater the refraction, the further the false aortas are located from each other(4). That is why greater probe curvature is conductive to the occurrence of the artifact. Authors argue that both the triangular shape of fat deposits between the rectus abdominis bellies and the neighborhood of tissues characterized by considerable conduction speed differences (muscles and fat) affect the occurrence of this artifact(3, 4). In an in vitro test and literature review concerning computed tomography performed in 100 patients, deep deposition of fat tissue was believed to have the greatest impact on the occurrence of the artifact. Superficial fat and muscles play a lesser role. A prismatic shape of a fat deposit makes waves entering from both its left and right sides refract towards the center. Subsequently, they run convergently and reach the aorta from both sides(11). Returning echoes undergo the same refraction and reach the receiver. The scanner analyzes returning signals as if the echo appeared in the structures located along one straight line from a beam sent by the transducer. This is how an image of two aortas is formed (Fig. 1)(1, 4, 11).


Double aorta artifact in sonography – a diagnostic challenge
A beam (continuous line) sent by the transducer (G) crosses the superficial fat tissue and rectus abdominis muscle (M), and refracts medially on prismatic slow-conductive deep fat tissue (T). The base of the prism is made by the edge of the liver. Subsequently, ultrasounds reach the aorta (A) through soft tissues. Produced echoes undergo identical refraction (continuous line) on their way back to the probe. The monitor shows two vessels (Ar). They are located on a straight line created by the emitted beam (dashed/dotted line) (1, 4, 11). They are observed to the left and right from the medially situated genuine aorta (A). Duplication concerns not only the aorta, but also all structures located on the way of ultrasounds undergoing refraction. This image is clearer distally from the probe since alleged images are then separated by a greater distance. An abnormal presentation of the margin of the vertebral body located behind the aorta (visible from below) frequently confirms the presence of the artifact rather than genuine duplication(3)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5392552&req=5

f0001: A beam (continuous line) sent by the transducer (G) crosses the superficial fat tissue and rectus abdominis muscle (M), and refracts medially on prismatic slow-conductive deep fat tissue (T). The base of the prism is made by the edge of the liver. Subsequently, ultrasounds reach the aorta (A) through soft tissues. Produced echoes undergo identical refraction (continuous line) on their way back to the probe. The monitor shows two vessels (Ar). They are located on a straight line created by the emitted beam (dashed/dotted line) (1, 4, 11). They are observed to the left and right from the medially situated genuine aorta (A). Duplication concerns not only the aorta, but also all structures located on the way of ultrasounds undergoing refraction. This image is clearer distally from the probe since alleged images are then separated by a greater distance. An abnormal presentation of the margin of the vertebral body located behind the aorta (visible from below) frequently confirms the presence of the artifact rather than genuine duplication(3)
Mentions: An ultrasound image of double aorta occurs when an ultrasound beam is refracted in an adequate way from abdominal wall structures. The rectus abdominis muscles and fat tissue between them can create an acoustic prism that refracts ultrasounds(3, 4, 10, 11). This phenomenon was studied and described in 1990 by Vandeman, but it is still not commonly known and can cause diagnostic difficulty to less experienced ultrasonographers. This artifact more frequently occurs in young athletic individuals(3, 11). Refraction occurs at the border of centers with different acoustic properties (Snell’s law: sin α2/sin α1 = V2/V1). The greater the speed of sound between tissues, the greater the refraction of an ultrasound beam. Ultrasound wave refraction creates an image of the viewed structure in a false location (Fig. 1). The greater the refraction, the further the false aortas are located from each other(4). That is why greater probe curvature is conductive to the occurrence of the artifact. Authors argue that both the triangular shape of fat deposits between the rectus abdominis bellies and the neighborhood of tissues characterized by considerable conduction speed differences (muscles and fat) affect the occurrence of this artifact(3, 4). In an in vitro test and literature review concerning computed tomography performed in 100 patients, deep deposition of fat tissue was believed to have the greatest impact on the occurrence of the artifact. Superficial fat and muscles play a lesser role. A prismatic shape of a fat deposit makes waves entering from both its left and right sides refract towards the center. Subsequently, they run convergently and reach the aorta from both sides(11). Returning echoes undergo the same refraction and reach the receiver. The scanner analyzes returning signals as if the echo appeared in the structures located along one straight line from a beam sent by the transducer. This is how an image of two aortas is formed (Fig. 1)(1, 4, 11).

View Article: PubMed Central - PubMed

ABSTRACT

The double aorta artifact was described and studied thoroughly twenty-five years ago. Despite this, it is still not commonly known today and can cause diagnostic difficulty. Total aortic duplication can be considered an anatomic defect whilst partial duplication mimics aortic dissection. In the literature, this artifact has been compared with a very rare anomaly, i.e. the occurrence of two aortas in one patient. Currently, however, the differentiation of this artifact from abdominal aortic dissection seems to be of greater significance. The double aorta image occurs when ultrasound waves encounter prismatic fat tissue of the anterior abdominal wall. This artifact is more frequently observed in children and athletic young adults since the structure of this anatomic region in these individuals is conductive to the occurrence of this phenomenon. Moreover, it can be observed more often when curved transducers are used. Due to all these factors, an ultrasound beam undergoes greater refraction and make the artifact clearer. This phenomenon is usually easily recognizable and avoidable, but it sometimes might cause diagnostic difficulty. Obtaining an image of double abdominal vessels on ultrasound examination in transverse sections requires further inspection of the aorta in a different (sagittal) plane. This is not always possible due to poor patient preparation for scanning. Symmetrical flow on Doppler sonography is a typical feature of this artifact. Finally, magnetic resonance imaging or computed tomography can be considered to rule out a pathology.

No MeSH data available.


Related in: MedlinePlus