Production of X-rays part 1

Question 1

What are the two parts of the tubehead?

Answer 1

x-ray tube
power supply (generator)

Question 2

What buttons are on the control panel?

Answer 2

Exposure time, kVp and mA selectors

Question 3

What type of exposure button do we use?

Answer 3

dead-man type (if you take finger off it stops exposure)

Question 4

What three things are required on the control panel?

Answer 4

• dead-man type exposure button
• indicator light
• audible signal

Question 5

What is in the tube head?

Answer 5

Power supply + x-ray tube

Question 6

What transformer is on the cathode (-) side?

Answer 6

step-down transformer

Question 7

What transformer is on the anode (+) side?

Answer 7

step-up transformer

Question 8

X-rays are produced by the anode or cathode?

Answer 8

anode

Question 9

Electrons are produced by the anode or cathode?

Answer 9

cathode

Question 10

What does the step-up transformer do?

Answer 10

raises voltage

Question 11

What does the step-down transformer do?

Answer 11

lowers voltage

Question 12

What are the parts of the tube head besides the power supply and x-ray tube?

Answer 12

◦ Glass envelope
◦ Insulating oil
◦ Metal housing
◦ Tube window
◦ Aluminum filters
◦ Lead collimator

Question 13

What does the insulating oil in the tube head do?

Answer 13

disperse heat

Question 14

What does the lead collimator do in the tube head?

Answer 14

determines final shape of the x-rays

Question 15

What do the aluminum filters do in the tube head?

Answer 15

filters the x-rays that are not useful (don’t go to patient)

Question 16

What is the space called inside the x-ray tube?

Answer 16

vacuum

Question 17

What are the two main parts of the cathode (-)?

Answer 17

filament
focusing cup

Question 18

What is the filament made of?

Answer 18

tungsten

Question 19

What is the focusing cup made of?

Answer 19

molybdenum

Question 20

What is the source of electrons?

Answer 20

filament

Question 21

How does the filament generate electrons?

Answer 21

Is heated with a low voltage source and emits electrons at a rate proportional to its temperature (thermionic emission)

Question 22

What is the charge of the focusing cup?

Answer 22

negative charge

Question 23

What does the focusing cup do?

Answer 23

Focuses the electrons into a narrow beam directed to the focal spot (+)

Question 24

What is thermionic emission?

Answer 24

emits electrons at a rate proportional to its temperature

Question 25

What are the two parts of the anode (+)?

Answer 25

- tungsten target - copper stem

Question 26

What does the copper stem do?

Answer 26

Works as a thermal conductor to remove the heat from the tungsten avoiding target melting

Question 27

What does the tungsten target do?

Answer 27

Transform the kinetic energy of the colliding electrons into x-ray photons

Question 28

What produces the x-rays?

Answer 28

x-rays produced on the focal spot on the tungsten target (anode)

Question 29

Is the tungsten target efficient or inefficient at producing x-rays?

Answer 29

Highly inefficient: produces 99% heat and 1% x-rays

Question 30

Why is tungsten a good target material?

Answer 30

1. High atomic number: efficient production of x-rays 2. High melting point 3. High thermal conductivity: to dissipate the heat produced away from the target 4. Low vapor pressure: helps maintain vacuum in the tube at high temperatures. 5. Cheap

Question 31

What are the conditions necessary for x-ray production?

Answer 31

1.Separation of electrons 2.Production of high-speed electrons 3.Concentration of electrons 4.Sudden stoppage of electron stream

Question 32

What allows for the separation of electrons?

Answer 32

Low voltage filament current heats the tungsten filament to incandescence with resultant separation of outer shell electrons from the tungsten atom (thermionic emission)

Question 33

What allows for the production of high-speed electrons?

Answer 33

High potential difference is produced between the cathode and anode by applying a high voltage between them

Question 34

What allows for the concentration of electrons?

Answer 34

Electron beam is focused by the focusing cup (negative charge) and directed towards the focal spot

Question 35

What allows for the sudden stoppage of electron stream?

Answer 35

Upon striking the focal spot in the anode, the electron stream is stopped abruptly, and kinetic energy of the electron stream undergoes conversion to greater than 99% heat and less than 1% x-radiation

Question 36

What is the focal spot?

Answer 36

Area on the target to which the focusing cup directs the electrons and from which the x-rays are produced

Question 37

Size of the _________ is important for image quality

Answer 37

focal spot

Question 38

smaller focal spot, _____ spatial resolution

Answer 38

higher

Question 39

smaller the focal spot → _____ heat accumulates

Answer 39

more

Question 40

Inclining the tungsten target does what to do the focal point?

Answer 40

smaller focal point

Question 41

What are two ways to alter the focal point heat problem?

Answer 41

1. Rotating anodes 2. Stationary anodes (line- focus principle)

Question 42

What is a rotating anode?

Answer 42

Allows heat at the focal spot to spread out over a large surface (medical devices mostly)

Question 43

What is the line-focus principle (stationary anode)?

Answer 43

Angling the target to achieve a smaller effective focal spot than the actual focal spot - Results in sharper radiographic image while maintaining the original surface area of the target for heat dissipation

Question 44

What is the actual focal spot?

Answer 44

the projection of the focal spot perpendicular to the target

Question 45

What is the effective focal spot?

Answer 45

the projection of the focal spot perpendicular to the electron beam

Question 46

Effective focal spot is always _____ than the actual focal spot

Answer 46

smaller

Question 47

What is the average size of the actual focal spot and effective focal spot?

Answer 47

actual - 3 mm effective - 1 mm

Question 48

What are the two functions of the power supply?

Answer 48

◦ Provide a low-voltage current to heat the x-ray tube filament (step-down transformer) ◦ Generate a high potential difference to accelerate electrons form the cathode to the focal spot on the anode (step-up transformer)

Question 49

What does a transformer do?

Answer 49

Electromagnetic device that either increases or decreases the voltage in a circuit

Question 50

What are the 3 types of transformers?

Answer 50

◦ Step-down transformer (filament transformer) ◦ Step-up transformer (high voltage) ◦ Autotransformer

Question 51

Used to convert 110 or 220 volts to 3-5 volts to heat the filament: step-up or step-down transformer?

Answer 51

Step-down transformer

Question 52

Which transformer is regulated by the mA switch?

Answer 52

Step-down transformer

Question 53

increasing mA setting will _______ the number of electrons emitted

Answer 53

increase

Question 54

Used to convert 110 or 220 volts to 60,000-100,000 volts to move the electrons across the tube: step-up or step-down transformer?

Answer 54

Step-up transformer

Question 55

Which transformer is regulated by the kV setting?

Answer 55

Step-up transformer

Question 56

Increasing the kV will ________ the energy of the electrons traveling from the cathode to anode

Answer 56

increase

Question 57

What does exposure time do?

Answer 57

Determines amount of time the high voltage circuit is applied across the x-ray tube (amount of time x-rays are produced)

Question 58

What is the time delay circuit?

Answer 58

delay of ½ second to heat the filament

Question 59

What is the timing circuit?

Answer 59

Actual time of exposure

Question 60

What does the kV (kilovoltage) do?

Answer 60

controls the acceleration of electrons from cathode to anode

Question 61

What does the mA (milliamperage) do?

Answer 61

controls heating of the filament

Question 62

What does the exposure time do?

Answer 62

controls the time in which x-rays are produced

Question 63

Answer 63

glass envelope

Question 64

Answer 64

x-ray tube

Question 65

Answer 65

power supply - step up transformer

Question 66

Answer 66

aluminum filter

Question 67

Answer 67

aiming cylinder

Question 68

Answer 68

power supply - step down transformer

Question 69

Answer 69

collimator

Question 70

Answer 70

insulating oil

Question 71

Answer 71

anode

Question 72

Answer 72

cathode

Question 73

Answer 73

cathode

Question 74

Answer 74

tube window

Question 75

Answer 75

anode

Question 76

Answer 76

copper stem

Question 77

Answer 77

vacuum

Question 78

Answer 78

glass envelope

Question 79

Answer 79

focal spot on tungsten target

Question 80

Answer 80

Electron focusing cup

Question 81

Answer 81

filament and electron cloud

Question 82

Answer 82

filament circuit

Question 83

Answer 83

aluminum discs

Question 84

Answer 84

postion indicating device

Question 85

Answer 85

lead collimator

Question 86

Answer 86

unleaded glass window of x-ray tube

Question 87

Answer 87

insulating oil

Question 88

Answer 88

metal housing of x-ray tube head

Question 89

Answer 89

anode

Question 90

Answer 90

step-up transformer

Question 91

Answer 91

x-ray tube

Question 92

Answer 92

step-down transformer

Question 93

Answer 93

cathode