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SEM II - Rad Physics > Xray Tube, Production & Emission > Flashcards

Xray Tube, Production & Emission Flashcards

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1
Q

Tube Housing/Protective Housing

A

Metallic housing usually lead lined which protects tube, absorbs unusable X-ray, protects from unnecessary radiation and electrical shock risk. Contains oil

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2
Q

Primary Beam/Useful Beam

A

Polyenergetic in nature, exists in a variety of strengths from 1kv to kvp

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3
Q

Tube window

A

Where the primary beam exists in the tube housing

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4
Q

Leakage Radiation

A

radiation that leaves the tube housing at a point other than the tube window

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5
Q

glass envelope of the X-ray tube

A

maintains a vacuum within

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6
Q

cathode

A

the negative side of the X-ray tube whose function is to emit electrons

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7
Q

filament

A

thightly wound coil, most xray tubes are dual focus (2 filaments), only one is used at a time

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8
Q

thermionic emission

A

electron emission from a heated source

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9
Q

filament current

A

the current supplied to the filament for heating

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10
Q

focusing cup

A

metallic cup that encases the filaments, composed of nickel or molybdenum; given a negative charge

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11
Q

millamperage

A

the number of electrons thermionically emitted per second

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12
Q

space charge/electron cloud

A

the collection of electrons “hovering” off the filament

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13
Q

anode

A

the positive side of the X-ray tube

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14
Q

rotating anode

A

anode capable of higher technical factors, anode disk rotates during exposure which spreads out heat over a larger area

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15
Q

stationary anode

A

lower technical factors, anode stationary as electrons impact to produce xray

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16
Q

target of anode

A

the point on the anode where the electrons strike

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17
Q

properties of tungsten that make it great for use in xray

A

high melting point (3422*c)
high atomic number (74)
good conductor of heat
good conductor of electricity

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18
Q

rotor

A

rotates, located inside the glass envelope, connected to the disk by the shaft of molybdenum.
can be noisy and continue to spin long after exposure

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19
Q

stator/induction motor

A

turns the anode disk, located on the outside of the glass envelope and tube housing.
no physical contact between the stator and anode, electromagnetism.

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20
Q

true/actual focal spot

A

the area of electron impact

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21
Q

effective focal spot

A

the true focal spot projected towards the patient

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22
Q

line focus principle

A

the effective focal spot will always be smaller than the true/actual focal spot

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23
Q

angle of anode

A

usually 7-15; 12 is standard

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24
Q

anode heel effect

A

the construction of the anode results in a disparity of X-ray intensity from cathode to anode. More X-rays on the cathode side versus the anode side

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25
Q

central ray

A

the portion of the X-ray beam that is directed tower the center of the film or object being imaged

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26
Q

off focus radiation

A

X-rays produces by stray electrons that interact at positions on the anode at points other than the focal spot

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27
Q

heat units

A

kvp x mas x rectification factor

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28
Q

methods of heat transfer

A

conduction, convection, radiation

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29
Q

conduction

A

the transfer of heat through a material by touching or physical contact of solid objects

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30
Q

convection

A

the transfer of heat by the mixing of molecules in a liquid or gas

31
Q

radiation

A

the transfer of heat by the emission of infrared radiation

32
Q

dielectric oil in X-ray tube function

A

absorbs unusable cry energy, electrically insulates, conducts heat away from the X-ray tube

33
Q

xray tube rating charts

A

designed for specific manufacturer and tube design,
based upon anode speed, angle, voltage rectification.
used to ensure heat limits not exceeded

34
Q

anode cooling charts

A

used to prevent damage to the anode by allowing it to cool sufficiently between exposures, shows how long it takes to cool from its max heat level

35
Q

3 things for X-ray production

A

source of free electrons, acceleration of free electrons, abrupt halting of high speed electrons

36
Q

characteristics of high speed projectile electrons include

A

have mass (small); negative charge; moving at high speed; possess massive kinetic energy

37
Q

characteristic of tungsten atoms include

A

high melting point, good conductor of heat/electricity, high atomic number (74)

38
Q

electron binding energy

A

unique characteristic of elements, measurable, no elements have the same binding energy values

39
Q

electron binding energy varies by

A

atomic # and distance from nucleus

40
Q

Tungsten shell levels

A 
K=69.5
L=12.1
M=2.8
N=0.6
O=.008
P=0
41
Q

kinetic energy

A

the energy an object in motion possesses

42
Q

KE=1/2mass x velocity2

A

kinetic energy equals one half mass times velocity squared

43
Q

projectile/incident electrons

A

electrons moving a a high level of speed from cathode to anode by kilovoltage

44
Q

beam quality/penetrability

A

the average X-ray strength in the polyenergetic primary beam

45
Q

beam quality/penetrability is controlled by

A

KVP (primary) and filtration (as filtration goes up, so does beam quality)

46
Q

beam quantity

A

the number of X-rays in the polyenergetic primary beam

47
Q

beam quantity is controlled by

A

MAS (primary); KVP; Filtration (as filtration goes up, beam quantity goes down)

48
Q

beam filtration

A

anything between the focal spot and the patient, can be gas, oil, plastic, mirror, air, etc

49
Q

inherent filtration

A

built into tube and housing

50
Q

added filtration

A

between housing and patient

51
Q

total filtration

A

inherent + added filtration

52
Q

minimum total filtration

A

at least 2.5mm Al/Eq

53
Q

Filtration is measured in

A

Aluminum Equivalence

54
Q

half value layer

A

the amount of filtration required to reduce beam intensity to half its original value

55
Q

As filtration increases

A

beam quality increases

56
Q

As filtration increases

A

beam quantity decreases

57
Q

the 1/3rd rule

A

the majority of X-rays created in the polyenergetic primary beam will have an energy value that is approximately 1/3 of the set KVP

58
Q

differential absorption

A

different materials absorb X-ray energy to differing degrees

59
Q

Bremsstrahlung Interaction

A

Braking:
A high speed/high kinetic energy electron enters a tungsten atom.
The (-1) charged electron is magnetically attracted to the (+74) nucleus.
Of a result, the incident electron slows down (brakes)and changes course.
The lost kinetic energy changes form into X-ray energy - unpredictable amount.

60
Q

How is the strength of Brems X-ray determined

A

The X-ray created is exactly equal to the amount of kinetic energy lost.

61
Q

Continuous emission spectrum

A

A spectrum having no lines or bands

Distributed over an uninterrupted range of wavelengths

62
Q

Characteristic Interaction

A

Collision:
High speed/kinetic energy electron enters a tungsten atom.
There is a collision with one of the orbital electrons.
If electron possesses greater energy than the orbitals, the orbital is ejected from its orbit leaving a hole.
An outer shell electron will jump across the space to fill the hole.
The electron she’ll transfer results in the transfer of energy, X-ray.
The strength of the X-ray is exactly equal to the difference in the orbital ring binding energies involved in the interaction. Only k she’ll interactions produce useful X-ray, predictable.

63
Q

Characteristic cascade

A

movement of electrons from outer shell to inner shell electrons

64
Q

how is the strength of a characteristic X-ray determined

A

The difference in orbital ring binding energies involved in the interaction.

65
Q

discrete emission spectrum

A

A spectrum in which the component wavelengths constitute a discrete sequence of values rather than a continuum of values.

66
Q

xray emission spectrum

A

A set of X-ray frequencies emitted by a target in an X-ray tube.

67
Q

Inverse Square Law

A

Any physical law stating that a specified physical quantity or intensity is inversely proportional to the square of the distance from the source of that physical quantity

68
Q

Xray intensity

A

KVP and filtration

69
Q

Polyenergetic/Heterogenous

A

X-ray energy exists in a variety of strengths from 1kv to the set KVP

70
Q

mGya (mR)

A

?????????

71
Q

Milliampere-seconds

A

(mAs)

The number of electrons in motion = the number of X-rays produced

72
Q

Kilovolt Peak

A

(KVP)

The strength of electron acceleration = the strength of X-rays produced

73
Q

compensating filter

A

A simple or complex system of placing a discretionary metal filter (usually aluminum) in front of the collimator in order to reduce a portion of the primary beam to compensate for varying body part thickness in the same field of view.

SEM II - Rad Physics (6 decks)

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