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Ultrasound Physics > Exam 2 Flashcards > Flashcards

Exam 2 Flashcards

1
Q

Definition of HVLT

A

Distance sound travels in tissue that reduces the intensity of sound to 1/2 the original value

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2
Q

Define the 10dB rule

A

+10dB is number increased by tenfold
-10dB is number decreased by 1/10
10 dB log rule for intensity and power

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3
Q

Define impedance

A

Acoustic resistance to sound traveling in a medium

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4
Q

Define attenuation

A

Decrease in intensity, power, and amplitude as sound travels

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5
Q

Define diffuse

A

Rough irregular or diffusive surfaces that scatter incoming lights/waves in multiple directions

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6
Q

Define specular

A

Reflecting interfaces with smooth (mirror-like) surface

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7
Q

Define Duty Factor, the abbreviation, and the equation

A

Percentage or fraction of time that the system transmits a pulse
DF
DF = PD/PRP

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8
Q

Define spatial pulse length, the abbreviation, and the equation

A

Distance that a pulse occupies in space from the start to the end of a pulse
SPL
SPL = Wavelength x # of cycles

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9
Q

Draw and label parts of a transducer

A

Look at picture on study guide

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10
Q

What are the consequences of using back material

A
  1. Decrease sensitivity
  2. Wide bandwidth
  3. Low Q-Factor
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11
Q

What is the equation for BW
What about QF

A

BW = Max-min
QF = Main frequency/bandwidth

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12
Q

Wha is the Piezoelectric effect

A

Transmission phase - energy converted to sound
Receiving phase - Reflected sound pulse converted to electric energy

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13
Q

Define intensity

A

Concentration of energy in a sound beam

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14
Q

Define a multi-frequency transducer

A

Transducers can produce more then 1 frequency of U/S as long as the frequencies are in the bandwidth of the transducer

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15
Q

Thickness of PZT and its effect on frequency

A

Thin - Higher frequency
Thick - Lower frequency

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16
Q

Name the regions of a sound beam

A

Near zone
Focal length/Near zone length/NFL
Focal zone
Far zone/Fraunhofer zone

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17
Q

Define the near zone

A

Narrowing part

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18
Q

Define the near zone length

A

Length of the near zone

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19
Q

Define focal zone

A

Area of relatively high intensity and narrow beam width that extends on either side of the focus

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20
Q

Define the far zone/fraunhofer zone

A

Diverging part of the beam

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21
Q

What is the equations for PD
PRP?
PRF?

A

PD = 1/frequency
PRP = 1/PRF
PRF = 1/PRP

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22
Q

What is the equation for axial resolution

A

AR = Wavelength x # of cycles in a pulse

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23
Q

Define the 13 dB rule

A

For every 13 us, sound travels 1 cm into the body (“Round trip”)

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24
Q

What is the equation for thickness and frequency

A

Frequency (MHz) = (Sound speed in PZT (mm/us) /2) x Thickness (mm)

25
What is the equation for 10 dB What are the units in intensity and power
10 x log (I/Io) I = mw/cm^2 P = w/cm^2
26
What is the angle information of importance and how you figure out the angles of 1 & 2
Speed 1 = Speed 2 - Same material Speed 1 < Speed 2 - Slow to fast - Large angle Speed 1 > Speed 2 - Fast to slow - Small angle
27
What is the purpose/importance of the 1/4 value
Matching layer is 1/4 of the thickness of the wavlenegth to act as a layer of protection
28
%T + %R = ?
100%
29
In S.T sound travels to a reflector and comes back in 39 us. How deep is the reflector?
3 cm
30
T or F: With certain transducer the systems axial resolution is invariant and there's nothing you can do to improve it.
True
31
You have a PRP of 1.2 ms, SPL of 2 mm, and wavelength of 0.4 mm. What is the axial resolution
1 mm
32
Axial resolution depends on
Wavelength
33
Where is the highest intensity on a transducer
At the focus
34
What region from the transducer to the smallest area beam called
Near zone/Fresnal Zone
35
T or F: Damping material helps to reduce PRP and given depth
False
36
T or F: Period in 3 MHz is > period in 6 MHz
T
37
In this equation which is the highest value, intermediate value, and the lowest value: Zm = square root of Ztissue x Ztransducer
Zm - Intermediate value Ztissue - Lowest value Ztransducer - Highest value
38
What does backscatter provides for organs
Much of the tissue texture information about organs
39
Reflectors are much ____ than the wavelength
Smaller
40
What is Rayleigh dependent on
Frequency dependent
41
In non-specular reflectors the amount of scattering will increase with ____ frequencies
Higher
42
Examples of specular reflectors
Renal capsule Endometrial and vag stripes Diaphragm
43
At specular reflectors the angle of reflection is = to?
Angle of incidence
44
What is the equation for %R
[Z2 - Z1 / Z2 + Z1] x 100
45
If you have a DF of 1 what type of wave do you have
Continuous wave
46
If you have a DF of <1 what type of wave do you have
Pulse wave
47
Name the characteristics of axial resolution
Determined by SPL LARRD (Long, range, radial, depth) Not adjustable Range 0.1-1mm
48
Name the characteristics of lateral resolution
Determined by width of sound beam LATA (Lateral, angular, transverse, Azimuthal)
49
Lateral resolution = to?
Beam diameter
50
Color in a scan takes longer due to
Machine needing to "paint" each line
51
How can you speed up the process of a color scan
Decrease sector Closer to transducer face = Faster refresh rate
52
What is the relationship of imaging depth and frame rate
Inversely related
53
Frame rate is how often a
Complete image is formed by the lines of the ultrasound
54
What are the units for frame rate
Frames/second or Hz
55
What are the characteristics of a high Q-Factor Low Q-Factor?
Long ring, CW, narrow BW, poor AR Short ring, PW, wide BW, good AR
56
What is the relationship of the PZT and frequency
Inversely related
57
Region of the transducer to the focus characterized by fluctuations in ampltiude and intensity from 1 point in the beam to another
Near field
58
Region of beam starting at focus and extending deeper
Far field

Ultrasound Physics (6 decks)

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