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Physics 121 > Ch 7 Performance & Safety > Flashcards

Ch 7 Performance & Safety Flashcards

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1
Q

No confirmed adverse effect in mammals exposed in vivo:

A

Below 1 W/cm2 SPTA
W/ low megahertz range
And
Focused beam

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2
Q

Typical output intensity (SPTA) for US

A

1 mW/cm2

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3
Q

Hydrophone membrane made of

A

Polyvinylidene fluoride (PVDF)

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4
Q

Temp rises significant if

A

Exceed 2 degrees C

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5
Q

Tissue phantoms simulate tissue properties and assess:

A

Detail/contrast resolution, penetration, dynamic range, and TGC

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6
Q

Tissues w/ well-defined gas (like lungs) have been observed for in situ peak rare factional pressures

A

Below 0.4 MPa or MI less than 0.4

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7
Q

Highest acoustic pressure output

A

Spectral Doppler

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8
Q

Lowest outputs

A

Gray-scale

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9
Q

Attenuation due to

A

Absorption (conversion of US to heat)

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10
Q

Test objects contain _____ and ______ to evaluate _______ and ________. They do not _______.

A

Nylon lines; scattering layers
Detail resolution; beam profiles
Simulate tissue characteristics

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11
Q

Regular quality control testing required by ___ at a minimum _____.

A

ACR

Semiannually

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12
Q

Bio effects have not occurred below ___. Above that bio effects depend on ___and ___.

A

39*C

Temp, time

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13
Q

Temp increases in tissues close to transducer surface significantly caused by

A

Transducer self-heating

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14
Q

Bio effects of hyperthermia:

A

Fetal absorption/abortion, IUGR, microphthalmia, cataract production, abdominal wall defects, renal agenesis, palatal defects, reduced brain waves, microencephaly, anencephaly, spinal cord defects, renal amyoplasia, forefoot hypoplasia, tibial/fibular deformities, abnormal tooth genesis

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15
Q

Phantoms and test objects can be used by

A

Service personnel and instrument operators.

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16
Q

Manufacturers must submit ___ to the ___ before _________.

A

Pre market notifications
FDA
marketing a device for a specific application in the U.S.

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17
Q

No significant adverse bio effects have been observed for exposure duration up to ____ from temp increases ____ above normal.

A

50 hours

Less than or equal to 2*C

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18
Q

Doppler test objects useful for testing:

A

Effective penetration of Doppler beam
Ability to distinguish different flow directions
Accuracy of sample volume (gate) location
Accuracy of measured flow speed

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19
Q

Sonography requires application of _____ principle which requires _______________.

A

ALARA

medical indication and using minimum output and exposure time necessary

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20
Q

Output of some current US machines can generate levels that _____.

A

Produce hemorrhage in lungs and intestines of lab animals.

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21
Q

2007 statement by AIUM:

A

Required medical indication for diagnostic examinations.

22
Q

Greatest risk from cracked transducer housing:

A

Electric shock

23
Q

____ regulates outputs

____ evaluates research

A

FDA

AIUM

24
Q

Freq = 1/?

A

Period

25
Q

PRF=

A

1/PRP

26
Q

DF=

A

PD/PRP

27
Q

Wavelength=

A

Prop speed/Freq

28
Q

SPL=

A

cycles X wavelength

29
Q

MI=

A

Peak rarefaction pressure (MPA) /

sq root of Freq

30
Q

Types of bioeffect studies

A
  • Experimental observation in cells
  • Epidemiologic studies on humans
  • Studies of interaction mechanisms (heating & cavitation)
31
Q

Hydrophone aka Microprobe measures…

A

Pressure in a sound wave

Calculates Period, PRP, and PD, PRF, DF, freq, pressure amp, wavelength, SPL, intensity

32
Q

Cavitation

A

Production/behavior of bubbles in liquid.

33
Q

Cavitation types

A

Stable- oscillates and may cause streaming/stresses

Transient- oscillates and collapses; shockwave may cause local extreme high temp and light emission

34
Q

TI Thermal Indices

A

Real-time display of thermal injury likelihood.

Either overestimate or very close

TIS- soft tissue
TIB- bone
TIC- cranial

35
Q

MI Mechanical Index

A

Likelihood of cavitation effects

No effects confirmed

36
Q

Output Intensities

A

Highest- Spectral
Lowest- Grey scale
Color and M mode in between

37
Q

SPTA intensity- Spatial Peak Temporal Average

A

Most commonly used;

Includes listening time

38
Q

Heat and fetal tissues/bones:
Absorption coefficient _______ in bone; Fetal tissue less ____; Most effects in ___ trimester during _____. If temperature is elevated > ____ for ___ min or more it can cause developmental effects.

A

higher
tolerant
1st; organogenesis
4*C; 5

39
Q

In vivo

A

In living

40
Q

In vitro

A

In glass

41
Q

Focused beams

A

less likely to cause temp rise in tissue

Max I= 1,000 mW/cm2 or 1 W/cm2

42
Q

Unfocused beams

A

more likely to cause temp rise in tissue

Max I= 100 mW/cm2

43
Q

Bioeffect study technique

Mechanistic Approach

A

Theoretical

Cause and Effect

44
Q

Bioeffect study technique

Empirical Approach

A

Based on review of info

Relationship btwn exposure and effects

45
Q

Both mechanistic and empirical have merits but…

A

Strongest argument when both approaches are in agreement

46
Q

Attenuation

A

Caused by 1)Reflection 2) Scattering 3) Absorption

Increases w/ longer distance and higher frequency

47
Q

Rayleigh Scattering

A

Scattering that occurs when structure’s dimensions are much smaller than the beam’s wavelength.
Redirects sound equally in all directions.
Ex: US and RBCs
It increases dramatically w/ increased Freq.:
Rayleigh Scatter= Freq^4

48
Q

Contrast Agents

A

Bioeffects confirmed w/diagnostic US and MI of >0.4 and gas body contrast agent present in circulation.

49
Q

Output Power vs. Receiver Gain

A 
Overall brightness- BOTH
Alters signal-to-noise ratio- OP
Alters patient exposure- OP
Bioeffect concerns- OP
Decrease OP if image too BRIGHT
Increase RG if image too DARK
50
Q

Therapeutic US

A 
Many uses (chemo, break of calculi, etc.)
Long duration US increases blood flow to area and speed healing of MSK injuries

Physics 121 (8 decks)

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