Ultrasound Physics inthe Operating Room      Tamas Seres, M.D.        UC Denver            2012
Ultrasound   Ultrasound (US) represents a mechanical    pressure disturbance propagating as wave    through materials den...
Piezoelectric Crystal
Piezoelectric Crystal as a Sender
Piezoelectric Crystal as a Receiver
Propagation of the Sound
Sound is a traveling variation of acustic variables.Acustic variables: particle motion, density and pressure.
Description of US waves   Amplitude - decibels (dB)   Frequency (f) - Cycles/sec – Hz   Wavelength (λ) - mm   Velocity...
Amplitude of the Sound   Amplitude: the difference between the reference    value (1x10-12 W/m2 ) and the maximum value o...
Amplitude   Decibels (dB) are logarithmic units based on a    ratio of the measured value V of acoustic    pressure to a ...
Decibel Scale of Sound
Amplitude Change in dB and %
Propagation Velocity, Frequency and           Wavelength                 c=fxλ    c= m/s, mm/µs    λ = mm    f = cycles/s ...
Propagation velocity of US indifferent tissues (m/s or mm/µs )                                   m/s                      ...
Frequency and Wavelength
Propagation Velocity, Frequency and           Wavelength                 c=λxf    λ (mm) = 1.54 (mm/µs)/ f (cycles/µs)    ...
Air Bubbles in the Blood during TMR
Ultrasound Pulses
Ultrasound Pulses
Ultrasound Pulse
Ultrasound Pulse
Ultrasound Pulse
Ultrasound Pulse
Ultrasound Pulse
Axial ResolutionFor better reflection from a particle: particle diameter > λFor axial resolution: Pulse Length/2 < Distanc...
Impedance   Impedance is the acoustic resistance to sound    traveling through a medium (Z).   Units: RAYL   Characteri...
Impedance                 Acoustic ImpedanceBody Tissue                 (106 Rayls)        Air                 0.0004     ...
ReflectionZ transducer >>> Z air <<<<Z tissue
TransmissionZ transducer = Z jelly = Z tissue
Reflection    Z tissue <<< Z needle
ReflectionIRC = Intensity Reflection Coefficient
Refraction
Refraction
Ultrasound in the Human Body   Can be oriented like beams.   Follow the physical laws of reflection, refraction    and s...
Air Bubbles in the Blood during TMR
Attenuation   As US penetrates into the body, signal strength    is attenuated due to absorption of the US energy    by c...
Attenuation
Amplitude Change in dB and %
Attenuation                 Attenuation CoefficientBody Tissue                 (dB/cm at 1MHz)       Water                ...
Half-power distances for a         frequency of 2 MHz   Water         380 cm   Blood          15 cm   Soft tissue   1-5...
Attenuation
US: 7.2 MHz
US: 5 MHz
US: 3.5 MHz
END
Ultrasound physics in the operating room I 972012
Ultrasound physics in the operating room I 972012
Upcoming SlideShare
Loading in …5
×

Ultrasound physics in the operating room I 972012

936 views

Published on

Helping material for learning TEE

Published in: Education, Business, Technology
0 Comments
1 Like
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
936
On SlideShare
0
From Embeds
0
Number of Embeds
7
Actions
Shares
0
Downloads
35
Comments
0
Likes
1
Embeds 0
No embeds

No notes for slide

Ultrasound physics in the operating room I 972012

  1. 1. Ultrasound Physics inthe Operating Room Tamas Seres, M.D. UC Denver 2012
  2. 2. Ultrasound Ultrasound (US) represents a mechanical pressure disturbance propagating as wave through materials dense enough to transmit the fast oscillations imparted on molecules. 2-12 MHz in medical practice.
  3. 3. Piezoelectric Crystal
  4. 4. Piezoelectric Crystal as a Sender
  5. 5. Piezoelectric Crystal as a Receiver
  6. 6. Propagation of the Sound
  7. 7. Sound is a traveling variation of acustic variables.Acustic variables: particle motion, density and pressure.
  8. 8. Description of US waves Amplitude - decibels (dB) Frequency (f) - Cycles/sec – Hz Wavelength (λ) - mm Velocity of propagation (c)- depends on each carrying medium - approximately 1540 m/s in blood and soft tissue
  9. 9. Amplitude of the Sound Amplitude: the difference between the reference value (1x10-12 W/m2 ) and the maximum value of an acoustic variable (dB). Sound scale:  0 dB hearing treashold  130 dB painful
  10. 10. Amplitude Decibels (dB) are logarithmic units based on a ratio of the measured value V of acoustic pressure to a reference value R ((1*10-12 W/m2) : dB = 20 log (V/R) For example: ratio of 2 20 x log 2 = 20 x 0.3 = 6 dB Ratio of 1000 = 60 dB
  11. 11. Decibel Scale of Sound
  12. 12. Amplitude Change in dB and %
  13. 13. Propagation Velocity, Frequency and Wavelength c=fxλ c= m/s, mm/µs λ = mm f = cycles/s (Hz), cycles/µs (MHz)
  14. 14. Propagation velocity of US indifferent tissues (m/s or mm/µs ) m/s mm/µs Air 330 0.33 Lung 500 0.5 Fat 1450 1.45 Soft tissue 1540 1.54 Bone 4000 4C (human soft tissue) = 1540 m/s or 1.54 mm/µs
  15. 15. Frequency and Wavelength
  16. 16. Propagation Velocity, Frequency and Wavelength c=λxf λ (mm) = 1.54 (mm/µs)/ f (cycles/µs) f = 5 MHz λ= 0.3 mm f = 7.5 MHz λ= 0.2 mm
  17. 17. Air Bubbles in the Blood during TMR
  18. 18. Ultrasound Pulses
  19. 19. Ultrasound Pulses
  20. 20. Ultrasound Pulse
  21. 21. Ultrasound Pulse
  22. 22. Ultrasound Pulse
  23. 23. Ultrasound Pulse
  24. 24. Ultrasound Pulse
  25. 25. Axial ResolutionFor better reflection from a particle: particle diameter > λFor axial resolution: Pulse Length/2 < Distance between 2 particles
  26. 26. Impedance Impedance is the acoustic resistance to sound traveling through a medium (Z). Units: RAYL Characteristic of the medium only. Z=density(kg/m3) x propagation speed(m/s)
  27. 27. Impedance Acoustic ImpedanceBody Tissue (106 Rayls) Air 0.0004 Lung 0.18 Fat 1.34 Liver 1.65 Blood 1.65 Kidney 1.63 Muscle 1.71 Bone 7.8
  28. 28. ReflectionZ transducer >>> Z air <<<<Z tissue
  29. 29. TransmissionZ transducer = Z jelly = Z tissue
  30. 30. Reflection Z tissue <<< Z needle
  31. 31. ReflectionIRC = Intensity Reflection Coefficient
  32. 32. Refraction
  33. 33. Refraction
  34. 34. Ultrasound in the Human Body Can be oriented like beams. Follow the physical laws of reflection, refraction and scattering. Propagate freely in liquids, but very poorly through air.
  35. 35. Air Bubbles in the Blood during TMR
  36. 36. Attenuation As US penetrates into the body, signal strength is attenuated due to absorption of the US energy by conversion to heat, as well as by reflection and scattering.
  37. 37. Attenuation
  38. 38. Amplitude Change in dB and %
  39. 39. Attenuation Attenuation CoefficientBody Tissue (dB/cm at 1MHz) Water 0.002 Blood 0.18 Fat 0.63 Liver 0.5-0.94 Kidney 1.0 Muscle 1.3-3.3 Bone 5.0
  40. 40. Half-power distances for a frequency of 2 MHz Water 380 cm Blood 15 cm Soft tissue 1-5 cm Muscle 0.6-1 cm Bone 0.2-0.7 cm Air 0.08 cm Lung 0.05 cm
  41. 41. Attenuation
  42. 42. US: 7.2 MHz
  43. 43. US: 5 MHz
  44. 44. US: 3.5 MHz
  45. 45. END

×