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Ultrasound Tissue Interactions: Reflection and Acoustic Impedance
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Ultrasound Tissue Interactions: Reflection and Acoustic Impedance

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Questions and Answers

What happens when two adjacent tissues have identical acoustic impedance?

  • Total transmission and no reflection occur (correct)
  • A small amount of waves are reflected but the majority is transmitted
  • Most of the waves will be reflected and only a small amount will be transmitted
  • Scattering of waves in multiple directions occurs
  • How does impedance mismatch between two tissues affect ultrasound waves?

  • All waves penetrate deeply into the tissue
  • Scattering of waves in multiple directions occurs
  • Most waves are reflected and only a small amount is transmitted (correct)
  • Total transmission and no reflection occur
  • How does the angle of reflection (ÆŸr) relate to the angle of incidence (ÆŸi) in ultrasound reflection?

  • ÆŸr is always smaller than ÆŸi
  • ÆŸr is perpendicular to ÆŸi
  • ÆŸr is always greater than ÆŸi
  • ÆŸr is equal to ÆŸi in the opposite direction (correct)
  • What does the process of scattering refer to in ultrasound interactions?

    <p>Redirection of sound in several directions due to small and/or irregular surfaces</p> Signup and view all the answers

    What property is used to describe the resistance encountered by an ultrasound beam as it passes through a tissue?

    <p>Acoustic impedance</p> Signup and view all the answers

    Which tissue interface results in nearly all of the sound wave being reflected back (approx. 99.9%)?

    <p>Soft tissue/Air interface</p> Signup and view all the answers

    How does a large difference in impedance between two tissues affect the transmission and reflection of an ultrasound wave?

    <p>Increases transmission and reflection</p> Signup and view all the answers

    What happens to the percentage of reflected sound at tissue interfaces as the magnitude of impedance mismatch increases?

    <p>It increases</p> Signup and view all the answers

    What happens to the acoustic energy of the beam as it passes through the body?

    <p>It is converted to heat absorbed by the tissues, attenuating the beam.</p> Signup and view all the answers

    Which type of tissue would likely attenuate more ultrasound waves?

    <p>Dense tissue like bone</p> Signup and view all the answers

    What is refraction in the context of ultrasound?

    <p>The change in direction of an ultrasound beam when passing from one medium to another</p> Signup and view all the answers

    What is the main function of a Brightness Scan (B-Scan) in ocular ultrasound?

    <p>To evaluate posterior segment and orbital pathology using a two-dimensional image</p> Signup and view all the answers

    Study Notes

    Ultrasound Waves and Tissue Interactions

    • When two adjacent tissues have identical acoustic impedance, there is no reflection of the ultrasound wave, and it passes through the tissue without interruption.
    • An impedance mismatch between two tissues causes the ultrasound wave to reflect back, with a greater mismatch resulting in a larger amount of reflection.
    • The angle of reflection (ÆŸr) is equal to the angle of incidence (ÆŸi) in ultrasound reflection, illustrating the concept of specular reflection.

    Ultrasound Scattering

    • The process of scattering refers to the random redirection of ultrasound waves by small particles or irregularities in the tissue, resulting in a loss of energy and image resolution.

    Ultrasound Beam Propagation

    • The property used to describe the resistance encountered by an ultrasound beam as it passes through a tissue is acoustic impedance.
    • The tissue interface that results in nearly all of the sound wave being reflected back (approx. 99.9%) is the air-lung interface.

    Effects of Impedance Mismatch

    • A large difference in impedance between two tissues affects the transmission and reflection of an ultrasound wave, with more energy being reflected back and less energy being transmitted through the tissue.
    • As the magnitude of impedance mismatch increases, the percentage of reflected sound at tissue interfaces also increases.

    Attenuation of Ultrasound Waves

    • The acoustic energy of the beam decreases as it passes through the body due to absorption and scattering of the sound wave by the tissue.
    • Bone tissue would likely attenuate more ultrasound waves due to its higher density and acoustic impedance.

    Ultrasound Refraction

    • Refraction in the context of ultrasound refers to the bending of the ultrasound wave as it passes through a tissue with a different acoustic impedance.

    Ocular Ultrasound

    • The main function of a Brightness Scan (B-Scan) in ocular ultrasound is to produce a 2D image of the eye and its structures, allowing for visualization and diagnosis of ocular disorders.

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    Description

    Explore how ultrasound interacts with tissues in terms of reflection and acoustic impedance. Learn about the outcomes when two adjacent tissues have identical or different acoustic impedance levels.

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