# ultrasound physics

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1. reciprocal
relationship btwn 2 numbers mutiplies together to equal one
2. pascal
unit of measurement for pressure
3. sound
is mechanical and longitudinal wave
4. y- axis
on a graph the vertical axis
5. x-axis
on a graph the horizontal axis
6. in-phase
if the rarefactions of 2 waves occur at the same time
7. destructive interferance
where the resultant wave is smaller then the one of its components
8. kg/cm cubed
proper unit to describe density
9. waves with different frequencies
type of wave will exhibit both constuctive and distructive interference
10. energys
what wave transfer from one location to another
11. all types of sound
mechanical energy transmitted by pressure waves in a medium
12. vaccum
sound waves can not travel through
13. they cause vibrations in the medium
properties common to all sound sources
14. medium
speed of sound depends on
15. commpressions
in sound wave, regions where the pressure is higher than normal
16. longitudinal wave
thype of sound wave that can propagate through soft tissue ( ultrasound waves)
17. wavelength
• dertemined by medium
• distance a wave travels one period of oscillation of the source
18. halves
frequency doubles, wavelength
19. Snell's Law
predicts the direction of the transmitted beam
20. speed of sound in tissue
• 1540m/s
• 1.54 mm
21. period
• p=1/freq
• time it takes to complete a single cycle
22. frequency
• f= 1/period
• number of times the wave is repeated per second
• number of cycles per unit of time
• determined by source
23. amplitude
peak pressure or height of wave
24. when sound is traveling through same medium if frequency increases
• wavelength= decreases
• propagation= stays the same
• period= decreases
• amplitude= stays the sam
25. pulse duration
• pd=cycle# x period
• pd=cycle#/freq
• is the time that the pulse is acually on
26. duty factor (cycle) for continous wave ultrasound is
100%
27. spatial pulse length
space from start of pulse to the end of that pulse
28. typical freq range in medial ultrasound imaging
1 to 32 MHz
29. watts
unit of power
30. can sonographer adjust intensity of the US beam?
YES
31. speed of sound determined by
medium
32. can pulse duration be changed?
NO
33. when depth is adjusted, what parametes are affected
• PRP (
• PRF (pulse repetition frequency)
• Duty Factor
34. if image depth increases
PRF decreases
35. PRF unit
Hertz
36. aspect of intensity refers to only the transmitted time
pulsed
37. sound intensity
directly proportional to transducer frequency
38. 7 parameters
• period
• frequency
• amplitude
• power
• intensity
• wavelength
• speed
39. acoustic variables
• pressure (pa)
• intensity (kg/cm3)
• distance (unit: cm,ft,mile)
40. propagation speed
determined by density and stiffness
41. if density increases
speed of sound decreases
42. intensity doubled
43. power
• measured in watts
• rate at which work is done
44. ultrasound frequency
>20KHz
45. transducer
determines the initial amplitude of the sound wave
46. SPTP
the highest intensity
47. attenuation coefficient
the amount of attenuation per depth traveled
48. attenuation
• decreased power, amplitude and intensity
• determined by path length and freq
• measured in dB
49. amplitude and intensity
are directly related
50. spatial pulse length
are denoted by source and medium
51. can intensity be adjusted by sonographer
YES
52. rayleigh scatterer
a red blood cell
53. acoustic insulator
thickness is 1/4 wavelength
54. axial
• longitudinal
• range
55. active element
• PZT
• .5 or 1/2 wavelength
56. backing material
improves resolution by reducing ringing
57. order of impedance from large to small
• PZT
• maching layer
• skin
58. low Q factor improved axial resolution and backing material
imaging transducer
59. characteristies of increased freq pulse wave transducer
• thinner PZT crystal
• faster speed in crystal
60. focal zone
thinnest
61. far zone
fraunhfer
62. transducer diameter affect beam divergance
after focus, small diameter crystals diverge wider
63. how does frequency alter beam divergance in far field
decreased freq diverge more
64. lateral resolution
• angular
• transverse
• lateral
65. M-mode
motion
66. A-mode
amplitude
67. B-mode
brightness
68. actual speed in PZT crystal
influences freq
69. sonographer can change
• power
• density
70. TGC & over all gain
brightening screen
71. ALARA
as low as reasonably achievable
72. demodualization
• use retofication to convert neg voltage to pos voltage
• uses smoothing to smooth out the bumps
73. reject
low level echos don't get into machine
74. picture element
pixel
75. 28 shades of gray= ? bits
• 2x2x2x2=16 not enough need 28
• 2x2x2x2x2=32 enough
• then we count the 2's
• so 5 bits
76. binary numbers
1's and 0's
77. types of archieving and storage
• optical media (lazer, CD)
• magnetic media (floppy disk)
78. preprocessing vs postprocessing
• pre= manipulate TGC, zoom in without loss of resolution
• post= zoom in but looses detail
79. how do you find depth
time- round trip
80. transducer
detector of soundwaves by recieving the sound waves from the body
81. what sound parameter influences axial resolution?
pulse duration
82. 2 parameters that influences speed of sound in medium
stifness and density
83. how to depolorize a PZT transducer
• curray point
• heat up to 365
84. infrasound
<20
85. audiable sound
>20 - 20k
86. what's focal depth affected by?
• transducer diameter
• freq of sound
 Author: monkies ID: 21947 Card Set: ultrasound physics Updated: 2010-06-09 16:40:49 Tags: Final Review Folders: Description: outline to study Show Answers: