Ultrasound Physics

  1. Hydrophone aka?
  2. a small hypodermic needle with a tiny piece of piezoelectric material attacfhed to its end. a wire connects the PZT crystal to an oscilloscope
  3. a hydrophone voltage relates to ______ of the sound beam 
  4. hydrophones measure accoustic pressure at _____ _______ with the sound beam
    specific locations
  5. by moving the hydrophone to many locations one can determine the sound beams what?
  6. What ultrasound variables can be determined by a hydrophone?
    period, PRP, PRF, pulse duration
  7. What output measurements and relationships can be determined by a calibrated hydrophone?
    • acoustic pressure vs pressure created
    • intensities
  8. what is the special quality of the hydrophone that is constructed from a very thin membrane of PZT plastic?
    it is pressure sensitive
  9. what is the measurable force created by transducers that relates to the power of a beam
    radiation force
  10. a shadowing system that allows us to view the shape of a sound beam in a medium
  11. the conversion of sound energy to heat
  12. 3 devices used to measure heat in US
    • calorimeter
    • thermocouple 
    • liquid crystals
  13. measures the total power in a sound beam through absorption
  14. a tiny electronic thermometer it is inserted into the sound beam and the temperature is measured at a particular location. the temp rise is related to the sound beams power 
  15. difference between calorimeter and a thermocouple 
    • calorimeter measures the power of the entire beam
    • thermocouple measures a particular location of the beam
  16. this provides insight into the shape and strength of a sound beam by changing color with temperature fluctuations 
    liquid crystals
  17. type of relationship where the benefits must outweigh the risks
    Risk-Benefit Relationship
  18. the science of identifying and measuring the characteristics of an US beam that are relevant to its potential for producing biological effects
  19. bioeffects research may be conducted in two broad areas
    • in vivo 
    • in vitro
  20. performed within the living body 
    in vivo
  21. performed outside the living body
    in vitro
  22. AIUM stands for
    American Institute of Ultrasound in Medicine
  23. Summary of AIUM in vitro bioeffects
    • in vitro bioeffects research is important
    • in vitro bioeffects are real even though they don't apply in the clinical setting
    • in vitro bioeffects which claim direct clinical significance (without in vivo validation) should be viewed with caution
  24. two techniques used to study bioeffects
    • mechanistic approach
    • empirical approach
  25. begins as a proposal that a specific mechanism has the potential to produce bioeffects. based on that proposal, a theoretical analysisis performed to estimate the scope of the bioeffects at various exposure levels
    mechanistic approach
  26. which technique for studying bioeffects is concerned with cause and effect?
  27. based on the acquisition and review of information from patients or animals exposed to ultrasound. seeks relationship between exposure and response
    empirical approach
  28. 2 important bioeffects mechanisms
    • thermal 
    • cavitation
  29. proposes that bioeffects result from tissue temperature elevation
    thermal mechanism
  30. a calculated number, it is a useful predictor of max temp increase under most clinically relevant conditions
    thermal index TI
  31. TIS stands for 
    thermal index in soft tissue
  32. TIB stands for 
    Thermal index in bone
  33. TIC stands for 
    thermal index in cranial bone
  34. does the thermal index have units
  35. what temperature elevation would cause infertility in the testicles
    2 to 4 degrees celcius 
  36. no confirmed bioeffects have been confirmed for temperatures up to ___C for exposures less than 50 hours
    2 degrees
Card Set
Ultrasound Physics
Condensed Notes