Ultrasound Imaging Artifacts Quiz

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What are two types of artifacts that can occur due to the ultrasound beam width?

Beam width artifacts and slice thickness artifacts.

What is the main cause of side lobe artifacts?

Side lobes are low energy beams that emanate from the transducer, causing echoes to be displayed outside the main beam.

How does the ultrasound beam width affect lateral resolution?

Lateral resolution is best at the focal zone where the beam is narrowest, and deteriorates as the beam widens in the near and far fields.

What is the relationship between the ultrasound frequency and beam width?

Higher frequency transducers have a narrower beam width. Signup and view all the answers

How do side lobe artifacts differ from slice thickness artifacts?

Side lobe artifacts occur due to low energy beams emanating from the side of the transducer, while slice thickness artifacts occur because the ultrasound beam has a height and can detect structures above or below the intended plane. Signup and view all the answers

What is the focal zone and why is it important in ultrasound imaging?

The focal zone is the narrowest region of the ultrasound beam. It is important because lateral resolution is optimal at the focal zone. Signup and view all the answers

What is meant by the term “lateral resolution” in ultrasound imaging?

Lateral resolution refers to the ability to distinguish two separate objects that are close together at the same depth within the imaging plane. Signup and view all the answers

Explain how beam width artifacts can lead to the misinterpretation of ultrasound images.

Beam width artifacts can cause two objects that are close together to appear as one, especially in the near and far fields where the beam is wider. Signup and view all the answers

What is the fundamental assumption about ultrasound beam direction that is violated when side lobes or grating lobes occur?

The assumption that echoes arise only from structures within the main ultrasound beam is violated. Side lobes and grating lobes are low-energy beams sent out of the transducer at the same time as the main beam, potentially picking up echoes from structures outside the intended imaging plane. Signup and view all the answers

Explain the difference between side lobes and grating lobes.

Side lobes are low-intensity beams that radiate from the sides of the main ultrasound beam. Grating lobes are stronger, distinct side lobes that can occur with certain types of transducers, particularly those using a phased array. Signup and view all the answers

What assumption about the imaging plane is challenged by the slice thickness artefact?

The assumption that the imaging plane is thin (both laterally and elevationally) is challenged by the slice thickness artifact. Signup and view all the answers

Describe a scenario where the slice thickness artefact might be particularly prominent.

The slice thickness artefact might be particularly prominent when imaging structures that are long and thin, like blood vessels or small tubular structures, as the artifact can create an illusion of greater thickness than the actual structure. Signup and view all the answers

What is the primary reason why ultrasound beam artefacts arise, even though sound wave propagation is assumed to be in a straight line?

The ultrasound beam isn't perfectly focused and can deviate from a straight line, particularly when imaging structures that have a complex shape or are located at a significant depth. Signup and view all the answers

How does the beam width artefact differ from the slice thickness artefact?

Beam width artefact refers to the width of the ultrasound beam in the imaging plane, while the slice thickness artefact refers to the thickness of the ultrasound beam along the elevational plane. Signup and view all the answers

Explain why ultrasound beam artefacts might be particularly challenging to differentiate from actual tissue structures in specific clinical scenarios.

Ultrasound beam artefacts can be challenging to differentiate from actual tissue structures in specific clinical scenarios, such as when imaging complex structures with intricate borders or in the presence of significant tissue heterogeneity. Signup and view all the answers

How can understanding the underlying principles of ultrasound beam artefacts help in interpreting ultrasound images effectively?

Understanding the principles of ultrasound beam artefacts helps in interpreting ultrasound images effectively by allowing the sonographer to recognize these artefacts, distinguish them from real structures, and make informed decisions about tissue characteristics. Signup and view all the answers

What are the two essential conditions for refraction to occur in ultrasound imaging?

Different propagation speed between two tissue types and oblique incidence. Signup and view all the answers

Describe how edge shadowing appears in ultrasound imaging.

Edge shadowing appears as hypoechoic parallel lines projecting distal to the edges of a structure, especially at the lateral edges of cysts or soft-tissue masses. Signup and view all the answers

What happens to an ultrasound beam when it encounters a curved surface at an increased angle?

The ultrasound beam reflects and refracts off the surface, resulting in decreased intensity of the beam reaching tissue distal to the curve. Signup and view all the answers

Explain the phenomenon of range ambiguity in ultrasound imaging.

Range ambiguity occurs when returning echoes are incorrectly assigned depth due to echoes from a deeper structure being received after a new pulse is generated. Signup and view all the answers

How does depth assignment based on time intervals impact ultrasound imaging accuracy?

Depth assignment impacts accuracy because if echoes from a prior pulse arrive after a subsequent pulse, the time interval is miscalculated, leading to incorrect depth perception. Signup and view all the answers

What is the primary cause of artifactual echoes in anechoic structures?

Artifactual echoes are primarily caused by adjacent objects at different apparent depths superimposing on the target. Signup and view all the answers

How does the assumption of a constant sound speed affect ultrasound imaging?

Assuming a constant sound speed of 1540 m/s leads to misplacement of echoes, resulting in artifacts in the image. Signup and view all the answers

What happens to sound waves when they encounter boundaries at oblique angles?

Sound waves change direction when encountering boundaries at oblique angles due to refraction. Signup and view all the answers

What are the four types of velocity error artifacts identified in ultrasound?

The four types are propagation speed artifact, refraction, edge shadowing, and range ambiguity. Signup and view all the answers

Describe the effect of boundary distortion on ultrasound imaging.

Boundary distortion occurs when echoes return from regions with different sound speeds, causing a distorted appearance of the interface. Signup and view all the answers

What is an example of how propagation speed artifacts affect echo placement?

If sound travels slower than 1540 m/s, the echoes will be placed deeper on the image than their actual depth. Signup and view all the answers

Why may ultrasound images show echoes adjacent to a target structure?

Echoes may appear adjacent due to side lobes or overlapping signals from nearby structures like adjacent bowel loops. Signup and view all the answers

What role does refraction play in the placement of echoes in an ultrasound image?

Refraction causes echoes to be placed to the side of their true location as sound waves bend at interfaces between different mediums. Signup and view all the answers

Ultrasound Beam Artefact

Artefacts arising from echoes outside the main ultrasound beam.

Straight Line Sound Travel

Sound travels in a straight line until it encounters a structure.