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MED 107- MEDICAL PHYSICS II > 68. ULTRASOUNDS: DOPPLER ULTRASOUNDS > Flashcards

68. ULTRASOUNDS: DOPPLER ULTRASOUNDS Flashcards

1
Q
  1. What is another term for a Doppler Ultrasound?
A
  • a Colour Flow Ultrasound
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2
Q
  1. What does a Doppler Ultrasound do?
A
  • it measures the speed with which blood flows in the
    body
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3
Q
  1. What do Colour Ultrasounds allow Cardiologists to do?
A
  • they allow Cardiologists to visualise the beating heart
  • they provide a colour-coded map of the flow of the
    blood within the heart’s chambers
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4
Q
  1. What are the 3 main advantages of using Diagnostic Ultrasounds?
A
  1. THEY DO NOT USE IONISING RADIATION
    • this makes it the safest modality
    • this is why it is so important for Obstetric imaging
  2. IT HAS THE ABILITY TO IMAGE IN REAL TIME
  3. THE COST OF THE ULTRASOUND SCANNER
    • is significantly less than that of other imaging
      modalities
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5
Q
  1. What techniques do we use when we cannot make use of an Ultrasound?
A
  • we can use cross-sectional imaging
  • with Computed tomography
  • or we can use an MRI
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6
Q
  1. List 7 more advantages of Ultrasounds.
A
  1. Non-invasive
  2. Painless
  3. Minimal preparation for patients
  4. Portable
  5. Inexpensive
  6. Has no known side effects
  7. Safe in pregnancy
  8. Gives direct vision for Biopsies and guides them
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7
Q
  1. What kind of wave is a sound wave?
A
  • it is a Mechanical wave
  • this is where the particles will propagate in a medium
  • the wave needs a medium to travel through
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8
Q
  1. What happens to the molecules when a wave is travelling through a Medium?
A
  • the molecules are alternately compressed and rarefield
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9
Q
  1. What type of mechanical wave is a Sound Wave?
A
  • they are longitudinal waves
  • they travel in a straight line
  • the motion of the particles is parallel to the motion of
    the wave
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10
Q
  1. What is the propagation of the wave a result of?
A
  • it results from Particle Oscillation
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11
Q
  1. What are Transverse Waves?
A
  • this is where the motion of the particles is
    perpendicular to the direction of the waves
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12
Q
  1. What are the parameters that we can use to completely characterise a Sound Wave?
A
  1. Period
  2. Frequency
  3. Amplitude
  4. Power
  5. Intensity
  6. Wavelength
  7. Propagation Speed

NB:
- these are the Bigness Parameters
- they describe the size, magnitude and strength of the
sound waves

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13
Q
  1. What is the Period?
A
  • this is the time taken for a wave to vibrate a single
    cycle
  • it is the amount of time it takes for a wave to travel one
    wavelength
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14
Q
  1. In which unit do we report the Period?
A
  • it is reported in units of time
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15
Q
  1. What is the Period determined by?
A
  • it is determined by the sound source only
  • it cannot be changed by the Sonographer
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16
Q
  1. How is the Period calculated?
A
  • it is calculated as: 1 / Frequency
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17
Q
  1. Define Frequency?
A
  • this is the number of cycles that occur in one second
  • it is the number of cycles per unit time
18
Q
  1. In which unit do we report Frequency?
A
  • we report it in Hertz (Hz)
19
Q
  1. What is the range of frequency that is used in Clinical Imaging?
A

IT RANGES FROM APPROXIMATELY:
- 2 MHz to 15 MHz

20
Q
  1. What is the Frequency of a sound wave determined by?
A
  • it is determined by the Sound Source only
  • it cannot be changed by the Sonographer
21
Q
  1. How do we calculate Frequency?
A
  • 1 / Period
22
Q
  1. Define Amplitude.
A
  • this is the difference between the maximum value
    (or the minimum value)
  • and the average value of an Acoustic Variable

IN OTHER WORDS:
- it is the main displacement or distance of the wave
from its rest position
- it is a vertical distance

23
Q
  1. In which unit do we report Amplitude?
A
  • we report it in the units of any acoustic variable
24
Q
  1. What is the Amplitude determined by?
A
  • it is initially determined by only the source
  • the Amplitude can be changed by the Sonographer
25
Q
  1. What happens to the Amplitude as the wave propagates through the body?
A
  • the Amplitude decreases at a rate
  • this rate is dependent on the medium and Sound
    Characteristics
26
Q
  1. Define Power.
A
  • Power is the rate of energy transfer
  • it is the rate at which work is performed
27
Q
  1. In which unit do we report Power?
28
Q
  1. What is Power determined by?
A
  • it is determined by the source only
  • it can be changed by the Sonographer
29
Q
  1. What happens to the Power as sound propagates through the body?
A
  • the Power decreases as sound at a rate
  • this rate depends on the medium
  • and on the sound characteristics
30
Q
  1. What is Power proportional to?
A
  • Power is proportional to the Amplitude Squared
31
Q
  1. Define Intensity.
A
  • this is the concentration of energy in a sound beam
  • it relates to how the power in a wave spreads or how it
    is distributed in space

IN OTHER WORDS:
- it is the energy flow per unit area

32
Q
  1. What unit do we report Intensity in?
A
  • Watts / cm²
  • this is the same as Power (W) / Area (cm²)
33
Q
  1. What is Intensity determined by?
A
  • it is initially determined only by the source
  • it can be changed by the Sonographer
34
Q
  1. What happens to the Intensity as the sound propagates through the body?
A
  • the intensity decreases at a rate
  • this depends on the medium
  • and the sound characteristics
35
Q
  1. What is Intensity proportional to?
A
  • it is proportional
    to the Power
  • it is proportional
    to the Amplitude
    squared
36
Q
  1. Define Wavelength.
A
  • this is the distance or length of one complete cycle

IN OTHER WORDS:
- it is the length between peaks
- or the length between troughs

37
Q
  1. In which unit do we report Wavelength?
A
  • it is measured in units of length
  • this can be metres or millimetres
38
Q
  1. What is the wavelength determined by?
A
  • it is determined by the source and the medium
  • it cannot be changed by the Sonographer

EXAMPLE OF SOURCE:
- Ultrasound crystal

EXAMPLE OF MEDIUM:
- tissue
- muscle
- bone

39
Q
  1. What is the wavelength inversely proportional to?
A
  • it is inversely proportional to the Frequency
40
Q
  1. How do we calculate the Wavelength in mm?
A
  • it is calculated as:the speed of the sound wave in a medium (in mm/µs)
    DIVIDED BY
    the frequency (MHz)

MED 107- MEDICAL PHYSICS II (108 decks)

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