Ultrasound Terms & Concepts

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1. Ultrasound
High frequency "sounds" inaudible to the human hear. >20kHz
2. Sound
• traveling variation of acoustic variables
• ; audible 20Hz - 20kHz
3. Frequency
number of cycles in a wave that occur in one second.
4. Acoustic variables
• Pressure
• Density
• Particle Motion
5. Wave
traveling variation of some quantity or quantities
6. Hertz
one cycles per second (Hz)
7. Kilohertz
• 1000 cycles per second
• kHz
8. Megahertz
• in million cycles per second
• MHz
9. Infra
"below" audible sounds and is a frequency too low for human hearing
10. ultrasound
"above" a frequency too high for human hearing.
11. Period
time it takes for one cycle
12. Frequency and period relationship?
• Inverse.
• As frequency increases period decreases.
13. Wavelength
the length of a cycles in space
14. Propagation Speed
speed at which a wave moves through a medium
15. Frequency and Wavelength relationship?
• inversely
• as frequency increases, wavelength decreases
16. Propagation speeds in solids and gases
• highest in solids
• lower in gases
17. Propagation speed in tissue
1.54 mm/microsec.
18. Harmonics
even and odd multiples of fundamental frequency
19. What is PRF?
• Pulsed Repetition Frequency
• # of pules per second
20. What is PRP
time from beginning of one pulse to the next
21. PRF and PRP relationship?
inversely

• PRF increases
• PRP decreases
22. Pulse duration
TIME for a pulse to occur
23. Duty Factor
fraction of TIME that pulsed ultrasound is on
24. PRP increases, PRP decreases and Duty Factor...
increases
25. Spatial Pulse Length
DISTANCE in space that a pulse takes up
26. # of Cycles in a pulse increases, SPL increaces. If frequency increases, wavelength and SPL....
decrease
27. What do shorter pulses do to image resolution
improves resolution
28. Bandwidth
range of frequencies contained in a pulse
29. Intensity (I)
rate at which energy passes through a unit area
30. How is Intesity related to power?
• proportional
• Intensity = power (mW)/area (cm^2)
31. If beam power increases, intensity increases. If beam area ____, intensity _____.
• decreases
• increases
32. If frequency increases penetration ______
decreases
33. Attenuation
weakening of sound as it propagates
34. If the attenuation coefficient ______, attenuation ______
• increases
• increases
35. If path length _____ attenuation ______
• increases
• increases
36. As frequency ______ increases, attenuation ______.
• increases
• increases
37. Perpendicular Incidence
denotes a directoin of travel  of US wave perpendicular to the boundary between two media.
38. Impedance
determines how much of an incident sound wave is reflected back into the first medium and how much is transmitted into the second medium.
39. If density _____, impedance ______.
If propogation speed _______, impedance _____.
• increases
• increases
• increases
• increases
40. Oblique incidence
denotes a direction of travel of the incident US that is NOT perpendicular to the boundary between two medium.
41. Refraction
"turn aside" - change of direction of sound when it crosses a boundary
42. Scattering
redirection of sound in many directions by rough surfaces, like tissue and blood.
43. Backscatter
sound scattered in the direction from which it came.
44. Speckle
grainy dots or "noise" in the display representing interference between constructive and destructive.
 Author: bjlewis44 ID: 192477 Card Set: Ultrasound Terms & Concepts Updated: 2013-01-15 05:44:57 Tags: ultrasound echo Folders: Description: US terms Show Answers: