US Physics 61-90

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US Physics 61-90
2013-06-19 22:43:40

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  1. When you image sound reflected from a large, smooth interface, you are observing results of:
    Specular reflection
  2. During a sonographic examination of a large vessel, a 45° beam-to-vessel angle would be called:
    Oblique incident
  3. What occurs when you image a structure with oblique incident?
    The angle of reflection will be oriented away from the transducer resulting in decreased visualization of the structure.

  4. The shadow depicted in this image of a renal stone is primarily a result of the following sound-tissue interaction:
  5. Which of the following statements regarding the effect of frequency on Rayleigh scattering is TRUE?
    Scattering intensity is proportional to frequency raised to the fourth power
  6. An echo from which one of the following sound reflectors is most dependent on the angle of incidence?
    Specular reflection
    What term describes the hyperechoic region (arrow) seen beneath this complex structure?
    Acoustic enhancement
  8. The hyperechoic region in the previous illustration results from:
    Decreased attenuation through a fluid-filled structure
  9. What determines acoustic impedance?
    Density and propagation speed of the medium
  10. What system control should you adjust to compensate for sound attenuation with increased depth?
  11. Diagnostic ultrasound is limited in its diagnostic application to the adult brain because:
    The greater acoustic impedance mismatch between the cranium and soft tissue caused most of the sound to be reflected at that interface
  12. Which of the following describes diffuse reflection?
    The reflected beam is scattered in various directions
  13. According to Snell's law, the angle of transmission is related to the incident beam angle and:
    The relative speeds of sound in the two media
  14. Which of the following interactions of sound and tissue decreases the intensity of the transmitted beam?
    Absorption, Reflection, Scattering and Conversion of sound to heat
  15. What is the relationship of frequency to absorption?
    If frequency is double, absorption is double
  16. What term is used to describe the reduction in the intensity of sound as it propagates through tissue?
  17. Another term for nonspecular reflection is:
  18. While performing a sonogram, you encounter the following interfaces. Which will produce in weakest reflected signal?
    Organ parenchyma/organ parenchyma
  19. During a diagnostic ultrasound examination, you encounter all of the interactions of ultrasound and tissue listed below. Which one will not cause a redirection of part of the ultrasound energy?
  20. As you perform a sonogram, you switch from a 3.5 MHz transducer to a 7.0 MHz transducer to image a superficial structure. Compared to the 3.5 MHz transducer, what will the 7.0 MHz attenuation rate and wavelength be?
    Double the attenuation rate, one half the wavelength
  21. You are scanning a large mass that is composed primarily of fat. Which of the following are you most likely to encounter?
    Axial misregistration of objects distal to the mass on the screen caused by the slower propagation speed through fat
  22. What two conditions must be presented to cause refraction of a sound wave?
    Oblique incidence and different media propagation speeds
  23. The transducer you are using transmits wide-bandwidth pulses whose frequency content is 2-5 MHz. Which of the following most correctly describes the reflected echo signals after they have traversed the tissue?
    The echo signals will be shifted down in frequency due to the increased attenuation of higher frequencies.
  24. When the sound beam is refracted during a sonographic examination, which of the following might you detect of the ultrasound image?
    Lateral misregistration
  25. During production of a sonogram, you image the following structures. Which is the most attenuating?
  26. What can you do to enhance the visibility of a specular reflector?
    Scan with perpendicular incidence
  27. What interaction of ultrasound and tissue is primarily responsible for imaging the internal structure of organs?
  28. What sound-tissue interaction is necessary to form an ultrasound image?
  29. For soft tissue, one of the factors responsible for determining acoustic impedance is:
  30. When you image a structure that is a specular reflector, the strength of the received signal depends on the following two factors:
    Difference in acoustic impedance and angle of incidence