Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Dental Radiology > X-Ray Production > Flashcards

X-Ray Production Flashcards

1
Q

what are the main components of the dental x-ray unit

A

tubehead, collimator, positioning arm, control panel, circuitry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the components of the x-ray tube

A

glass envelope, cathode, anode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the cathode filament

A

coiled metal wire

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what gets passed through the cathode filament

A

low voltage, high current electricity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

how are electrons released from the cathode wire

A

by thermionic emission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what happens if you increase the current in the cathode filament

A

increased heat and increased electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is the cathode filament made of

A

tungsten

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are the properties of tungsten

A

high melting point, high atomic number (lots of electrons), malleable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the cathode focusing cup

A

metal plate shaped around filament

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is the cathode focusing cup made of

A

molybdenum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are the properties of molybdenum

A

high melting point, relatively poor thermionic emitter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is the relationship between the cathode and anode

A

electrons released at filament are repelled away from the cathode and attracted to the anode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

how is kinetic energy generated between cathode and anode

A

when the electrons collide with the anode target they have a high kinetic energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what do transformers do

A

take mains electrical supply and convert it by changing the voltage and current

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the mains electrical supply

A

220-240v

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the 2 transformers present in the tubehead

A

step up and step down

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what does the step up transformer do

A

increase potential difference across x-ray tube to 60,000-70,000V

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what does the step down transformer do

A

decrease the potential difference across filament to about 10V

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what do electron volts measure

A

the kinetic energy gained by electrons as they accelerate from cathode to anode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is an anode target

A

metal block bombarded by electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is the anode target made of

A

tungsten

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is the focal spot on the anode target

A

precise area on target where electrons collide and x-rays are produced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is the purpose of the heat dissipating block on the anode

A

heat produced in target dissipates into the block by thermal conduction to reduce risk of overheating

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is the heat dissipating block made of

A

copper

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
what are the properties of copper
high melting point and high thermal conductivity
26
what is the penumbra effect
blurring of a radiographic image due to focal spot not being a single point
27
how do you minimise the risk of the penumbra effect
shrinking size of focal spot
28
what is the solution to the need to have a small focal spot
have an angled target
29
what is the effect of having an angled target
increases the actual surface area where electrons impact and reduces the apparent surface area from where the x-ray beam is emitted
30
what does the glass envelope do
supports cathode and anode, maintains a vacuum
31
what is the purpose of the glass envelope to be leaded
to absorb x-ray photons
32
what are the main components of the tubehad
x-ray tube, metal shielding, aluminium filtration, oil, spacer cone
33
what is the purpose of the oil in the tubhead
dissipates heat produced by x-ray tube by thermal conduction
34
what does the filtration in the tubehead do
removes lower energy x-rays from beam to decrease patient dose
35
why is the filtration made of aluminium
it can absorb those photons so that the resulting x-ray beam contains mostly diagnostic x-ray photons
36
what is the minimum thickness of aluminium required for a filtration
for less than 70kV = 1.5mm for greater than 70kV = 2.5mm
37
what does the spacer cone do
dictates distance between focal spot and patient and indicates direction of the beam
38
what is the distance between the focal spot and patient called
focus to skin distance
39
what will altering the focus to skin distance do
affect degree of divergence of x-ray photons in x-ray beam
40
what does increasing the focus to skin distance do
reduced divergence of x-ray beam and therefore reduces magnification of image
41
what does a set focus to skin distance allow
consistent radiographic technique
42
what is the focus to skin distance required for modern equipment (>60kv)
200mm
43
where is the focus to skin distance measured from
the focal spot which is marked on tubehead
44
what are the 3 possibilities for the fate of x-ray photons emitted from the focal spot
attenuated by lead shielding attenuated by aluminium filtration exit tubehead to form x-ray beam
45
what is the collimator
lead diaphragm attached to end of spacer cone
46
what is the purpose of the collimator
reduces patient dose and crops x-ray beam to match size and shape of x-ray receptor
47
when using size 2 receptors what should rectangular collimators reduce the beam area at the patient end of spacer cone to
50mm x 40mm
48
what can rectangular collimation reduce the surface area irradiated to
by almost 50%
49
what is the disadvantage to using collimation
can increase risk of collimation errors
50
what are the consequences of electrons bombarding the target
heat production and x-ray production
51
what kind of electrons are involved in heat production at the target
outer shell electrons of tungsten atoms
52
what kind of electrons are involved in x-ray production at the target
inner shell electrons and nuclei of tungsten atoms
53
how common is it for x-rays to be produced at the target
<1%
54
what happens in a heat producing interaction
bombarding electron reaches tungsten outer shell electron which either collides or deflects bombarding electron loses kinetic energy which is converted to heat heat energy dissipated
55
what are the 2 x-ray producing interactions
continuous radiation interactions characteristic radiation interactions
56
what is the continuous radiation interaction
bombarding electron passes close to target nucleus causing it to be rapidly decelerated and deflected meaning lost kinetic energy released as x-ray photons
57
when is the maximum energy achieved in the continuous radiation spectrum
when the electron collides directly with the nucleus and stops completely
58
what does continuous radiation spectrum mean
photons produced over wide range of energies
59
what does filtration of the continuous spectrum do
remove lower energy non-diagnostic x-ray photons from beam
60
what is the characteristic radiation interaction
bombarding electron collides with an inner shell electron and either displaces it into a more peripheral shell or removes it completely remaining orbiting electrons rearrange themselves to re-fill the innermost shells
61
what happens when electron drops to a lower shell
loses energy which is emitted as a photon of specific energy
62
what is photon energy
difference in the binding energies of the 2 shells involved
63
what is the binding energy of a K shell
69.5keV
64
why do dental x-ray tubes operate at 70kV
so that bombarding electrons have sufficient energy to displace K shell electrons
65
what is the dental x-ray beam spectrum
continuous radiation + characteristic radiation - filtered photons

Dental Radiology (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions