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Ultrasound Physics > Exam 2 Flashcards > Flashcards

Exam 2 Flashcards

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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
Q

What is the equation for 10 dB
What are the units in intensity and power

A

10 x log (I/Io)
I = mw/cm^2
P = w/cm^2

26
Q

What is the angle information of importance and how you figure out the angles of 1 & 2

A

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
Q

What is the purpose/importance of the 1/4 value

A

Matching layer is 1/4 of the thickness of the wavlenegth to act as a layer of protection

28
Q

%T + %R = ?

A

100%

29
Q

In S.T sound travels to a reflector and comes back in 39 us. How deep is the reflector?

A

3 cm

30
Q

T or F:
With certain transducer the systems axial resolution is invariant and there’s nothing you can do to improve it.

A

True

31
Q

You have a PRP of 1.2 ms, SPL of 2 mm, and wavelength of 0.4 mm. What is the axial resolution

A

1 mm

32
Q

Axial resolution depends on

A

Wavelength

33
Q

Where is the highest intensity on a transducer

A

At the focus

34
Q

What region from the transducer to the smallest area beam called

A

Near zone/Fresnal Zone

35
Q

T or F:
Damping material helps to reduce PRP and given depth

A

False

36
Q

T or F:
Period in 3 MHz is > period in 6 MHz

A

T

37
Q

In this equation which is the highest value, intermediate value, and the lowest value:
Zm = square root of Ztissue x Ztransducer

A

Zm - Intermediate value
Ztissue - Lowest value
Ztransducer - Highest value

38
Q

What does backscatter provides for organs

A

Much of the tissue texture information about organs

39
Q

Reflectors are much ____ than the wavelength

A

Smaller

40
Q

What is Rayleigh dependent on

A

Frequency dependent

41
Q

In non-specular reflectors the amount of scattering will increase with ____ frequencies

A

Higher

42
Q

Examples of specular reflectors

A

Renal capsule
Endometrial and vag stripes
Diaphragm

43
Q

At specular reflectors the angle of reflection is = to?

A

Angle of incidence

44
Q

What is the equation for %R

A

[Z2 - Z1 / Z2 + Z1] x 100

45
Q

If you have a DF of 1 what type of wave do you have

A

Continuous wave

46
Q

If you have a DF of <1 what type of wave do you have

A

Pulse wave

47
Q

Name the characteristics of axial resolution

A

Determined by SPL
LARRD (Long, range, radial, depth)
Not adjustable
Range 0.1-1mm

48
Q

Name the characteristics of lateral resolution

A

Determined by width of sound beam
LATA (Lateral, angular, transverse, Azimuthal)

49
Q

Lateral resolution = to?

A

Beam diameter

50
Q

Color in a scan takes longer due to

A

Machine needing to “paint” each line

51
Q

How can you speed up the process of a color scan

A

Decrease sector
Closer to transducer face = Faster refresh rate

52
Q

What is the relationship of imaging depth and frame rate

A

Inversely related

53
Q

Frame rate is how often a

A

Complete image is formed by the lines of the ultrasound

54
Q

What are the units for frame rate

A

Frames/second or Hz

55
Q

What are the characteristics of a high Q-Factor
Low Q-Factor?

A

Long ring, CW, narrow BW, poor AR
Short ring, PW, wide BW, good AR

56
Q

What is the relationship of the PZT and frequency

A

Inversely related

57
Q

Region of the transducer to the focus characterized by fluctuations in ampltiude and intensity from 1 point in the beam to another

A

Near field

58
Q

Region of beam starting at focus and extending deeper

A

Far field

Ultrasound Physics (6 decks)

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