# physics

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1. The effects of the medium upon the sound wave.
Acoustic Propagation Properties
2. The effects of the sound wave on biologic tissue
Biologic Effects
3. Sound is what kind of wave?
Mechanical, longitudinal
4. Period-
Definition?
Determined by?
Changed by sonographer?
The time required to complete a single cycle

determined by--source

changed by sonographer--no
5. Frequency-
Definition?
Units?
Determined by?
Changed by sonographer?
• Definition--The number of certain events that occur in a particular time duration
• Units-- per second, hertz, Hz
• Determined by--Source
• Changed by sonographer--no
6. Ultrasound Range?
Greater than 20,000Hz, not audible
7. Audible Sound
20-20,000 Hz
8. Infrasound?
Less than 20 Hz
9. Formula for intensity?
• I= power/area
• I=w/cm2
10. Intensity is proportional to?
Amplitude2
11. Formula for wavelength?
wavelength (mm)= prop. speed (mm/us) / frequency (MHz)
12. Formula for wavelength in soft tissue?
wavelength= 1.54mm/frequency (MHz)
13. Wavelength is determined by?
Source and Medium
14. Propagation speed is determined by?
• Medium only,
• density and stiffness
15. Propagation Speed formula?
• speed= frequency x wavelength
• (m/s) =(Hz) x (m)
16. In-Phase waves interfere how?
Constructively
17. Pulse duration formula?
PD= number of cycles in pulse x period

or

PD=number of cycles in pulse / frequency
18. Pulse Repetition Period definition?
The time from the start of one pulse to the start of the next pulse. Includes "on time" and "off time"
19. PRP
Determined by?
Changed by sonographer?
• Determined by-- source
• Changed by sonographer--yes
• (amount of listening time is determined by image depth)
20. PRF definition?
The number of pulses that occur in one second
21. PRP formula?
1/ PRF
22. PRF formula?
1/ PRP
23. Depth and PRF are related how?
Inversely proportional
24. Depth and PRP are related how?
directly proportional
25. PRP x PRF = ??
1
26. Duty Factor formula?
DF = PD/PRP x 100
27. Duty Factor
Definition?
Determined by?
Changed by sonographer?
• Definition-- The percentage of time the system is transmitting sound. (% of "on time")
• Determined by-- source
• changed by sonographer--yes
28. SPL formula?
SPL= number of cycles x wavelength
29. SPL determines resolution?
Axial resolution
30. PRP, PRF, and DF are all affected by what?
Depth of view
31. What intensity is most relevant with respect to tissue heating?
SPTA
32. What is the log of:
a-100?
b-10,000?
• a-2
• b-4
• (count the zeros)
 Author: lmarie ID: 16174 Card Set: physics Updated: 2010-04-26 02:11:38 Tags: Period Folders: Description: ARDMS SPI Physics Review Show Answers: