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Fetal Echo 2022 > Phycis And Instrumentation > Flashcards

Phycis And Instrumentation Flashcards

1
Q

What is the most important physical parameter influencing absorption of the sound beam

A

Frequency

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2
Q

Absorption of energy from attenuation of the ultrasound beam as it travels through tissues is highest in

A

Bone

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3
Q

Function that equalizes the ultrasound signals received from various depths and displays them with equal reflections

A

Time gain compensation
TGC

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4
Q

What function controls the number of ultrasound pulses transmitted per second and is dependent on depth of penetration and sample volume

A

PRF

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5
Q

Why is it important to choose the correct sample volume size

A

Small sample volume prevents interference from the blood flow in nearby vessels
A sample volume too small will not allow parts to flow
Sample volume should be adapted to fit the diameter of the vessel being interrogated

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6
Q

In order to obtain the most precise image the area of interest should be focused in what part of the sound beam

A

Near field

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7
Q

What phenomenas associated with the passage of the ultrasound beam through body tissues are classified as bioeffects

A

Thermal and mechanical effects

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8
Q

The rise in temp in tissues under the influence of ultrasound energy is controlled by the power level settings on the us machine. What is considered an INSIGNIFICANT rise in temp ?

A

< 2.0 degree Celsius

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9
Q

Best description of Alara principle

A

Keeping both output power and exposure time as low as reasonably achievable

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10
Q

Where does maximum tissue heating occur during the ultrasound

A

Between the transducer surface and focal zone

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11
Q

Optimal transducer frequency for a fetal echo

A

5-7 mhz

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12
Q

The transducer emits a sound beam across the field of view. What term describes the location where the sound beam reaches its narrowest diameter

A

Focal zone

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13
Q

What adjustments will eliminate aliasing

A

Changing the angle of insonation
Shifting the baseline
Lowering the frequency
Increasing the PRF

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14
Q

Shadowing occurs when the object of interrogation has a high level of

A

Attenuation

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15
Q

What artifact caused by two strong reflectors with a large surface area is displayed in the near field and has multiple equally spaced echoes that extend into the far field

A

Reverberation artifact

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16
Q

What can you do to eliminate shadowing in a image

A

Decrease the frequency
Adjust the angle of insonation to avoid scanning through fetal ribs
Adjust frame rate
Adjust rejection

17
Q

Which type of artifact is produced by interference patterns and results in the granular appearance of the image

A

Speckle

18
Q

What function is used to eliminate low frequency noise and artifacttual clutter caused by the movement Of the vessel walls

A

Wall filter

19
Q

What is the term for a frequency shift that exceeds the Nyquist limit during pulsed wave or color Doppler imaging

A

Aliasing

20
Q

Color Doppler imaging gives info on

A

Blood flow velocity
Blood flow direction
Frequent shift
Blood flow disturbances

21
Q

In order to Visualize flow in vessels with low flow states such as the pulmonary veins what adjustment should the sonographer make

A

Decrease the PRF

22
Q

What are the benefits of power Doppler when compared to color Doppler

A

Power Doppler is less dependent on the angle of insonation
Power Doppler is not subjective to aliasing
Power Doppler less dependent of direction is blood flow
Power Doppler is useful in slow flow velocity states

23
Q

In a Doppler wave form across the mitral valve the A wave represents

A

Atrial systole

24
Q

Normal patent foreman ovale flow is

A

Biphasic 20-40 cm/sec

25
Q

Pulsatile flow in the umbilical vein seen with Doppler most likely represents

A

Congestive heart failure and volume overload

26
Q

If a fetus has a cardiac defect with reduced cardiac inflow the DV waveform will be abnormal the abnormal waveform will have

A

Reduced A wave toward the baseline reversed flow of the A wave during atrial contraction

27
Q

Which modality of ultrasound transmits the GREATEST amount of energy into the fetus

A

Pulsed Wave Doppler

28
Q

A peak systolic velocity in the ductus arteriosus that exceeds ——— cm per second has been reported in cases of ductal constriction

A

> 140

29
Q

Increasing PRF decreases

A

Aliasing

30
Q

As depth increases the PRF

A

Decreases

31
Q

Increasing the the PRF will ______ the number of pulses transmitted per second eliminating the noise and scatter of the ultrasound frequencies

A

Decrease

Fetal Echo 2022 (7 decks)

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