# Ultrasound Physics

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1. A reduction in the intensity of a sound beam to one-half of its orignal value is ____ dB?
-3dB
2. A reduction in the intensity of a sound beam to one-quarter of its orignal value is _____dB.
-6dB
3. -10 dB means that the intensity is reduced to ____ of its orignal value.
One-tenth
4. dB is a mathematical representation with a ___&___ scale.
logarithmic & relative
5. True/False. We need one intensity to calculate decibels.
False
6. A wave's intensity is 2 mW/cw2. There is a change of +9dB. What is final intensity?
16 mW/cm2
7. Every 3 dB change means that the intensity will ______.
Double
8. Every 10 dB change means that the intensity will _____________.
Increase ten times
9. If the final intensity of a sound beam is more than the initial intensity, then the gain in dB is _____. (+ or -)
Positive
10. If the initial intensity of a sound beam is less than the final intensity, then the gain in dB is _______.
Positive
11. Name the three components of attenuation.
Absorption, reflection & scattering
12. As the path length increases, the attenuation of ultrasound in soft tissue ________.
increases
13. Attenuation in lung tissue is [less than, greater than, the same as] attenuation in soft tissue?
greater than
14. Attenuation in bone is _______ attenuation in soft tissue.
greater than
15. Attenuation in air is ______ attenuation in soft tissue.
greater than
16. What are the units of attenuation?
Decibels (dB)
17. T or F. In a given medium, attenuation is unrelated to speed of sound.
True (Attenuation & propagation speed are unrelated)
18. What is the relationship between ultrasound frequency and the attenuation coefficient in soft tissure?
In soft tissue, the attenuation coeffiecient in dB per centimeter is approx one-half of the ultrasonic frequency in MHz.
19. What are the units of the half-value layer thickness?
distance: centimeters
20. As frequency decreases, depth of penetration _________.
Increases
21. As path length increases, the half boundary layer ______.
remains the same
22. Impedence is a characteristic of ______.
Only the medium
23. As the path length increases, the attenuation coeffiecient of ultrasound in soft tissue [decreases, remains the same, increases]
remains the same
24. Acoustic impedance = _______x_______
Impedance = density (kg/m3) x propagation speed (m/s)
25. Two media A and B have the same densities. The speed of sound in medium A is 10% higher than in medium B. Which medium has the higher acoustic impedance?
Medium A's acoustic impedance is higher than medium B's.
26. Impedance is important in ______ at boundaries.
Reflections
27. Which is better to use while examining a carotid artery, a 7.5 or 3.0 MHz transducer?
The carotid artery is a superficial structure. A 7.5 MHz transducer is better because the higher frequency transducer produces the better image.
28. List temporal intensities from largest to smallest.
TP, Imax, PA, TA
29. List temporal intensities from smallest to largest.
TA, PA, Imax, TP
30. Name the many different names for Axial Resolution.
LARRD. (Longitudinal, Axial, Range, Radial, Depth)
31. Normal incidence is also know as?
PORNN (Perpendicular, Orthogonal, Right angle, Ninety degrees, Normal)
32. A sound wave with intensity of 50 W/cm2 strikes a boundary and is totally reflected. What is the intensity reflection coefficient?
Since the wave is totally reflected, the intensity reflection coefficient is 100%.
33. A sound wave with intensity of 50 W/cm2 strikes a boundary and is totally reflected. What is the intensity reflection coeffiecient?
Since the wave is totally reflected, intensity is 50 w/cm2
34. What is the formula for reflection with Normal Incidence?
IRC=(Z2-Z1) / (Z2+Z1) x 100
35. What is the formula for transmission with Normal Incidence?
• ITC = 1- IRC
• or ITC = transmitted intensity / incidenct intensity X 100
36. What is the conservation of energy concerning coefficients?
100%= IRC+ITC
37. Snell's Law defines what?
refraction
38. What's the formula for Snell's Law?
Sin (transmission angle) /Sin (incident angle) = Speed of Medium 2/ Speed of Medium 1
39. A 2 cm deep reflector has a go-return time of ___microseconds.
26
40. A 3 cm deep reflector has a go-return time of ___microseconds.
39
41. For every 13 microseconds of go-return time, the object creating the reflection is ___cm deeper in soft tissue.
1 cm
42. When the depth of view is shallow, the PRP is ______?
short
43. When depth of view is deep, PRP is ______?
long
44. What is the PRP when imaging to a depth of 4 cm?
52 microseconds (4x13=52)
45. If the PRP is 65 microseconds, what is the max imaging depth?
5 cm (13x5=65)

### Card Set Information

 Author: Ultrasound ID: 108812 Filename: Ultrasound Physics Updated: 2011-10-14 01:07:00 Tags: Test Three Folders: Description: Edelman Test 3 Show Answers:

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