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physics exam 2 > Exam 2 > Flashcards

Exam 2 Flashcards

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1
Q

Which tube will dissipate heat better?

A

Tube with the larger FSS and larger angle

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2
Q

Which tube has largest Effective FSS?

A

Pick tube with the largest angle

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3
Q

What amperage does thermoionic emission take place?

A

between 3-5 so 4 would be “best answer”

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4
Q

Focusing cup in the cathode must be what electrical charge?

A

Negative

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5
Q

When is focusing cup positive?

A

When you want short exposure time with grid x-ray- usually used in interventional therapy

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6
Q

Increasing anode angle from 7 –> 15 causes a(n) _____ in the EFSS?

A

Increase

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7
Q

What is the Heel Effect?

A

CR intensity will be greater towards cathode side and less intense towards anode side because electrons have to travel through more material in anode so they are weaker

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8
Q

Where do you place the patient in relation to anode/cathode side?

A

Thicker parts under cathode side and thinner under anode

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9
Q

What does a small focal spot and a small Field Of View (FOV) make more prominent?

A

The darkness scale is more prevalent in images with a small FSS and a small FOV

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10
Q

When do you see the Heel Effect the most? 3 things..

A
  • small focal spot
  • shorter SID
  • larger film size
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11
Q

What could damage the tube? 3 things..

A
  • high exposure without warmup
  • long exposure time could melt it
  • filament vaporization, some point filament will crack
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12
Q

What three things are built in to the machine to keep the machine from breaking?

A
  • anode cooling chart
  • housing cooling chart
  • radiographic cooling chart
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13
Q

What number to remember in formula for 3 phase 6 pulse heat calculation?

A

1.35

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14
Q

What number to remember in formula for 3 phase 12 pulse heat calculation?

A

1.41

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15
Q

How do we cool the tube? 2 ways..

A

oil and a fan

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16
Q

What are the 2 types of xrays produced?

A

Characteristic and Brem’s

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17
Q

We send electrons across with KE. The more kVp you select, the more…

A

energy across the tube

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18
Q

Every 100 electrons that cross the tube, how many actually produce an xray?

A

1%, 99% converted to heat

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19
Q

Amount of heat is ____ related to the amount of electrons.

A

directly related, MA^, H^

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20
Q

What is the typical diagnostic range for kVp?

A

50 kVp-150 kVp

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21
Q

As you increase kVp, you are ___ amount of xrays, similarly producing more ___ interaction instead of ____ interactions.

A

increasing, xray, heat

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22
Q

What kVp level must occur for Characteristic xrays to occur?

A

69 kVp and up

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23
Q

What is the formula to calculate Characteristic xray?

A

binding energy from shell that electron was taken from from the binding energy of the new shell

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24
Q

What shell gives USEFUL interaction?

A

k

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25
Q

What is quality in an xray?

A

kEv

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26
Q

What gives you max xray interaction?

A

When the electron crashes into the nucleus head on and gives off 100% of its energy

27
Q

What is the kEv in tungsten to create characteristic?

A

69/70 kEv

28
Q

To increase the KE of an electron, you can change the what?

A

e- velocity, AKA kVp

29
Q

What % of electrons reaching the anode create xray?

A

1%

30
Q

Characteristic xray requires what to occur?

A

Electron removal from an atom

31
Q

Brem’s radiation production at 70 kVp accounts for what % of beam?

A

85%, 15% is characteristic

32
Q

What is an emission spectrum?

A

graphical representation of an xray

33
Q

What do you look at in an emission spectrum to determine max kVp output?

A

The end kVp on the chart

34
Q

When kVp increases or decreases, what is directly proportional to it?

A

of xray photons

35
Q

___ % increase in kV equals ___ of mAs

A

15, doubling

36
Q

Higher kVp and more energetic xrays, means what for the patient?

A

More are penetrating the patient

37
Q

What 3 things are inherent filters in the xray tube? What are their numbers?

A
  • window, 1.0 mm AlEq
  • oil
  • mirror, 1-1.5mm AlEq
38
Q

What is the FDA requirement for amount of aluminum equivalent required for attenuation?

A

2.5mm

39
Q

Number of xrays coming out on anode side is ___ with more filtration?

A

less

40
Q

What does filtration look like on a chart?

A

filtration= amplitude DOWN, and shift to the RIGHT

41
Q

What is it termed when there are less xrays in the beam, but has a higher energy?

A

Hard beam

42
Q

For anodes, what material is used in the center for most attraction?

A

Tungsten, because high Z#, the higher the Z#, the more attraction and more energy

43
Q

What happens to the graph when kVp is increased?

A

The amplitude goes down and the graph shifts to the right

44
Q

What happens to the graph when you just change mAs?

A

Only the amplitude changes

45
Q

An xray beam may be termed as which of the following?

A

Polyenergetic

46
Q

The emission spectrum cross the x axis at what % of the kVp?

A

100% (last number on the graph= input kVp)

47
Q

An increase in the amp of emission spectrum only indicates increase in ____?

A

mAs

48
Q

How many half-value layers must be added to the primary beam to reduce its intensity to less than 20% of the original value>

A

3

49
Q

Which of the following is affected by half-layer value?

A

patient exposure

50
Q

The amount of material that will reduce the intensity of the primary beam to one-half its original value is?

A

half-layer value

51
Q

Which of the following are useful as a filter?

A

aluminum, oil, glass

52
Q

The types of target interaction that occurs in the production of diagnostic range xray photons are dependent upon…?

A

electron KE

53
Q

The transfer of incident electrons’ KE to the outer shell electrons causing vibration of the outer shell electron results in emission of what?

A

infrared radiation

54
Q

Almost all of the KE of the incident electrons is converted to ____.

A

heat

55
Q

What type of voltage is required for portable units?

A

3 phase voltage

56
Q

How far do electrons usually travel into the tube target?

A

.5mm

57
Q

What is 1 R in mGy?

A

10mGy

58
Q

The kVp is on the X axis- what does it represent? Quality or quantity?

A

Quality

59
Q

Where is the peak shown on the graph for characteristic radiation?

A

69 kEv

60
Q

The quantity of the xray beam is described as its ___.

A

intensity

61
Q

What are the two elements used for mammography?

A

Molybdenum and Rhodium

62
Q

What is the typical intensity of a diagnostic xray beam?

A

.05mGy

63
Q

Xray quantity is ____ to mAs.

A

directly proportional

64
Q

T/F Increasing mAs does not increase xray efficiency.

A

True

physics exam 2 (1 decks)

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