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S4: Radiographic Imaging > Chapter 5 Notes > Flashcards

Chapter 5 Notes Flashcards

1
Q

x-ray production requires what

A

a source of electrons, an appropriate target material, a high voltage, and a vacuum

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2
Q

the x-ray tube consists of

A

a cathode and anode enclosed within an envelope and then encased in a protective housing

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3
Q

the cathode is the _____ side of the x-ray tube

A

negative

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4
Q

function of the cathode

A

produce a thermionic cloud, conduct the high voltage to the gap between cathode and anode, and focus the electron stream as it heads for the anode

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5
Q

cathode assembly consists of

A

the filament or filaments, focusing cup, and associated wiring

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6
Q

what is the filament

A

a small coil of thin, thoriated tungsten wire

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7
Q

the focusing cup serves to

A

narrow the thermionic cloud as it is driven to the anode

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8
Q

the anode is the _____ side of the x-ray tube

A

positive

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9
Q

anodes are divided into what two types

A

stationary and rotating

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10
Q

anodes are made using what

A

tungsten

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11
Q

tungsten is used to make anodes because

A

high atomic number, high melting point, and good heat-conducting ability

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12
Q

anode assembly consists of

A

anode, stator, and rotor

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13
Q

the portion of the anode where the high-voltage electron stream impacts is called

A

target, focus, focal point, focal spot, or focal track

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14
Q

effective focal spot describes

A

the area of the focal spot that is projected out of the tube toward the object being radiographed

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15
Q

line-focus principle is used to

A

reduce the effective area of the focal spot (permits the best detail in as large of an area as possible)

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16
Q

effective focal-spot is controlled by

A

the filament size and the anode target angle

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17
Q

when the target angle is less than _____ degrees, the effective focal spot is smaller than the actual focal spot

A

45 degrees

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18
Q

anode heel effects states that

A

radiation intensity is greater on the cathode side than on the anode side

19
Q

what can cause serious degradation of radiographic image quality?

A

off-focus or extrafocal radiation

20
Q

off-focus radiation comprises

A

photons that were not produced at the focal spot

21
Q

three types of heating charts

A

radiographic tube rating charts, anode cooling charts, and housing cooling charts

22
Q

heating charts are available to help radiographers

A

avoid thermal damage to x-ray tubes

23
Q

which heating chart is most valuble

A

radiographic rating charts because they provide a guide regarding the maximum technical factor combinations that can be used without overloading the tube

24
Q

what is the melting point of tungsten

A

3,370 degrees C

25
Q

what are also good choices for filament material

A

rhenium and molybdenum

26
Q

most modern x-ray tubes will last between how many exposures

A

10,000-20,000 exposures

27
Q

focusing cup is composed of

A

nickel

28
Q

grid-biased tubes changes charge of focusing cup from

A

negative to positive

29
Q

grid-biased tubes permit

A

very short, rapid sequencing of exposures

30
Q

rotating anode made of

A

tungsten-rhenium alloy

31
Q

anode layering assists with

A

heat loading

32
Q

when should tube warm-up procedure be performed

A

if tube has been idle for an extended period of time (>2 hours)

33
Q

rotating anode can increase heat capacity by

A

300x

34
Q

the actual focal spot is

A

the physical area of the focal track being hit by electrons

35
Q

the effective focal spot is

A

the projected area of x-ray beam

36
Q

with the anode heel effect, beam intensity can vary as much as

A

45%

37
Q

what is the only part of the x-ray tube located outside the envelope

A

stator

38
Q

rotor is made of

A

copper cylinder connected to anode disk by molybdenum stem

39
Q

what is the Gyroscopic effect

A

when high speed anode rotations add stress to x-ray tube design

40
Q

envelope is made of

A

heat tolerant Pyrex glass or metal

41
Q

two functions of envelope

A

supports anode/cathode assemblies and maintains a vacuum

42
Q

off-focus radiation contributes up to what percent of the total primary beam

A

25%

43
Q

ways to extend x-ray tube life

A
  1. follow recommended tube warm-up procedures
  2. avoid frequent and successive “boosting” of tube
  3. use low mA settings when possible
  4. use low speed rotor rotation when possible
  5. follow rating charts
  6. avoid rough handling of x-ray tube head
  7. listen for unusual sounds

S4: Radiographic Imaging (31 decks)

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