Bioeffects Flashcards

(43 cards)

1
Q

What is QA?

A

It is the routine, periodic evaluationg of an ultrasound system to guarantee an optimal image quality

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2
Q

What is the purpose of QA?

A
  1. Optimize image quality
  2. Assess intersystem differences
  3. Assess intrasystem changes over time
  4. Verify system specifications
  5. Minimize artifacts
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3
Q

What are the goals of QA?

A
  1. To guarantee proper operation of the system
  2. Detect gradual changes over time
  3. Minimize machine downtime
  4. Reduce # of non-diagnostic exams
  5. Reduce # of repeat scans
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4
Q

What is sensitivity?

A

It is the ability of a system to display low-level echoes.

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5
Q

What are 2 forms of sensitivity?

A
  1. Normal
  2. Maximum
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6
Q

What is normal?

A
  • Uses “normal setting”
  • It detects all pins
  • It detects all solid masses
  • It detects all cystic structures
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7
Q

What is maximum?

A
  • It is evaluated with output power and amplification.
  • Maximium visualization depth is used to assess sensitivity
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8
Q

What is the dead zone?

A
  • It is the region closest to the transducer
  • It extends from the transducer to the shallowest depth from which meaningful reflections appear (pins)
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9
Q

What are the characteristics to a tissue equivalent phantom?

A
  • Similar to tissue
    • Speed
    • Attenuation
    • Scattering
    • Echogenicity
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10
Q

What is the Doppler phantom?

A

It is the device of choice for evaluating doppler systems

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11
Q

What is the modern doppler phantom?

A

It includes cirulation pumps which properl fluid through vessels embedded in a tissue phantom.

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12
Q

What is slice thickness phantom?

A

It assess the slice thickness and it effect on image quality

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13
Q

What does slice thickness determine?

A

It determines evalutional resoluton which is more likely to degrade image quality.

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14
Q

What is the AIUM statement?

A
  • Valid medical reason
  • Understand equipment
  • Use ­ receiver gain, ¯ output power
  • ALARA
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15
Q

What does ALARA mean?

A

As Low As Reasonably Achievable

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16
Q

What does the AIUM limit?

A
  • Thermal: Unfocused beam = 100 mW/cm2 ;Focused beam = 1 W/cm2
  • Non-thermal: 0.4 MPa or MI =0.4 (gas bodies); 4MPa or MI = 4.0 (non-gas bodies)
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17
Q

What is the logic behind bioeffects?

A
  • –Ultrasound (US) = mechanical wave
  • Mechanical wave interacts with medium
  • US attenuated in medium
    (E is absorbed)
  • Modalities have different
    wave characteristics
  • intensities at £ focus
  • Understand effects of
    output power vs.
    receiver gain
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18
Q

What is dosimetry?

A

It is the science of idenitfying and measuring the characteristics of an ultrasound beam that are relevant to its potential for producing biological effects.

19
Q

What does in vivo mean?

A

It is research is performed within the living body.

20
Q

What does in vitro mean?

A

It is research that is performed outside the living body

21
Q

What is thermal effect related to?

A

It is related to related to exposure time

22
Q

What is the thermal effect?

A

Conversion of US to heat→ à metabolic breakdown

(Core body temperature = 37°C)

23
Q

What does the thermal effect depend on?

A

Depends on PRF, DF, ability of body to duct heat

  • Worst in non-scanned regions (narrow area, fast rate)
  • Greatest risk with Doppler (DF = 100%)
  • Increased with color Doppler
  • Lowest risk with B-mode
24
Q

What is cavitation?

A

It is the interaction of sound waves with microscopic, stabilized, gas bubbles in the tissue.

25
What are the two forms of cavitation?
1. Stable 2. Transient
26
When does stable cavitation occur?
It overs at lower MI levels
27
What happens om stable cavitation?
The gaseous nuclei tend to oscillate, or expand and contract. Bubbles do not burst.
28
What is power?
rate energy is transferred (mWatts) n.b. Watt = Joules / second
29
What is intensity?
= power / unit area (mWatts / cm2)
30
What does temporal refer to?
Refers to time exposure
31
What does spatial refer to?
Refers to physical beam area exposure
32
What does **I SPTP** mean?
highest; spatial peak, temporal peak→ Mechanical
33
What does **I SP PA** mean?
spatial peak, pulse average
34
What does **I SP TA **mean?
spatial peak, temporal average→ Thermal
35
What does **I SA TP** mean?
(spatial average, temporal peak)
36
What does **I SA TA **mean?
lowest; spatial average, temporal average
37
What does the temporal average equal? | (TA)
TA = PA • DF
38
What does the pulse average equal? | (PA)
PA = TA / DF
39
What does spatial average equal? | (SA)
SA = SP / BUF
40
What is the thermal index?
predicts max temp ↑
41
What is the equation for TI?
TI = 6 – (log10t / 0.6)
42
What does the mechanical index do?
predicts cavitation injury
43
What is the equation for MI?
MI = Peak Neg Press / √freq