Bioeffects

Question 1

What is QA?

Answer 1

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

Question 2

What is the purpose of QA?

Answer 2

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

Question 3

What are the goals of QA?

Answer 3

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

Question 4

What is sensitivity?

Answer 4

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

Question 5

What are 2 forms of sensitivity?

Answer 5

1. Normal
2. Maximum

Question 6

What is normal?

Answer 6

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

Question 7

What is maximum?

Answer 7

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

Question 8

What is the dead zone?

Answer 8

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

Question 9

What are the characteristics to a tissue equivalent phantom?

Answer 9

• Similar to tissue
  
  • Speed
  • Attenuation
  • Scattering
  • Echogenicity

Question 10

What is the Doppler phantom?

Answer 10

It is the device of choice for evaluating doppler systems

Question 11

What is the modern doppler phantom?

Answer 11

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

Question 12

What is slice thickness phantom?

Answer 12

It assess the slice thickness and it effect on image quality

Question 13

What does slice thickness determine?

Answer 13

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

Question 14

What is the AIUM statement?

Answer 14

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

Question 15

What does ALARA mean?

Answer 15

As Low As Reasonably Achievable

Question 16

What does the AIUM limit?

Answer 16

• 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)

Question 17

What is the logic behind bioeffects?

Answer 17

• –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

Question 18

What is dosimetry?

Answer 18

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

Question 19

What does in vivo mean?

Answer 19

It is research is performed within the living body.

Question 20

What does in vitro mean?

Answer 20

It is research that is performed outside the living body

Question 21

What is thermal effect related to?

Answer 21

It is related to related to exposure time

Question 22

What is the thermal effect?

Answer 22

Conversion of US to heat→ à metabolic breakdown

(Core body temperature = 37°C)

Question 23

What does the thermal effect depend on?

Answer 23

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

Question 24

What is cavitation?

Answer 24

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

Question 25

What are the two forms of cavitation?

Answer 25

1. Stable
2. Transient

Question 26

When does stable cavitation occur?

Answer 26

It overs at lower MI levels

Question 27

What happens om stable cavitation?

Answer 27

The gaseous nuclei tend to oscillate, or expand and contract.

Bubbles do not burst.

Question 28

What is power?

Answer 28

rate energy is transferred (mWatts)
n.b. Watt = Joules / second

Question 29

What is intensity?

Answer 29

= power / unit area (mWatts / cm2)

Question 30

What does temporal refer to?

Answer 30

Refers to time exposure

Question 31

What does spatial refer to?

Answer 31

Refers to physical beam area exposure

Question 32

What does I _SPTP mean?

Answer 32

highest; spatial peak, temporal peak→ Mechanical

Question 33

What does I _{SP PA} mean?

Answer 33

spatial peak, pulse average

Question 34

What does I _{SP TA} mean?

Answer 34

spatial peak, temporal average→ Thermal

Question 35

What does I _{SA TP} mean?

Answer 35

(spatial average, temporal peak)

Question 36

What does I _{SA TA} mean?

Answer 36

lowest; spatial average, temporal average

Question 37

What does the temporal average equal?

(TA)

Answer 37

TA = PA • DF

Question 38

What does the pulse average equal?

(PA)

Answer 38

PA = TA / DF

Question 39

What does spatial average equal?

(SA)

Answer 39

SA = SP / BUF

Question 40

What is the thermal index?

Answer 40

predicts max temp ↑

Question 41

What is the equation for TI?

Answer 41

TI = 6 – (log10t / 0.6)

Question 42

What does the mechanical index do?

Answer 42

predicts cavitation injury

Question 43

What is the equation for MI?

Answer 43

MI = Peak Neg Press / √freq