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Radiology > Production of x-rays > Flashcards

Production of x-rays Flashcards

1
Q

what is the domestic electricity supply?

A

220/240v
50 Hz
13 amp

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2
Q

complete the sentence

A is converted to B within the x ray tube

A

a- domestic electrical supply
b-x rays

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3
Q

draw the dental xray tube

A

check notes

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4
Q

where is the filament found within the xray tube?

A

at the cathode

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5
Q

what is the fine wire filament made from?

A

tungsten

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6
Q

why is tungsten used in the xray tube?

A

-because it has a high melting pt and a lot of heat is generated during xray production

-it has a high tensile strength so can be pulled into very fine wire (filament)

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7
Q

what size of current passes along the filament?

A

8-10 mA

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8
Q

what is a step down transformer and why is it needed?

A

current must pass through step down transformer as amp of electrical supply is 13 A

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9
Q

what is the step down transformer made of?

A

copper

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10
Q

what happens to electrons in the cathode?

A

-as current passes along filament- electrons get excited and vibrate
-wire gets hot and gives off light
-excited electrons are lost from outer shells and form electron cloud around cathode within focusing cup

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11
Q

what is the anode made from?

A

copper with a tungsten target

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12
Q

what is the potential difference between the anode and the cathode?

A

50-90 kV

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13
Q

why is a step up transformer needed?

A

because the domestic electrical supply is only 220/240V the voltage will become 70kV

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14
Q

what happens to the high energy electrons when they are pulled towards the anode?

A

the electrons suddenly stop at anode changing their form into 99% heat and 1% X-rays

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15
Q

what are the two types of collisions that give rise to x-rays ?

A

continuing spectrum and characteristic spectrum

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16
Q

what occurs during continuing spectrum collision?

A

-free electrons around cathode are attracted to positive nucleus of tungsten
-electrons slow down/change direction as they reach the tungsten target
-as they slow/deflect energy is lost and released as X-rays

17
Q

what happens if electrons pass close to the nucleus of tungsten?

A

they slow significantly and significantly change direction- giving most of their energy to photons producing x-rays

18
Q

what happens if electrons pass further away from nucleus?

A

they do not slow or change direction as much- therefore giving off less energy to photons producing X-rays

19
Q

why should low energy photons be filtered within the X-ray tube?

A

because they do not produce a quality image and therefore will be absorbed by the patient unnecessarily
-they have little penetration power

20
Q

what are low energy X-rays absorbed by?

A

normally soft tissues (superficial structures)

21
Q

what are X-rays produced by as?

A

bremstraulling radiation

22
Q

is there a wide range of energies produced with continuous spectrum?

A

yes- electrons all have different energy and produce a wide range of photon energies.

23
Q

what is the maximum photon energy produced?

A

directly related to the keV of energy across the x ray tube

24
Q

what happens during characteristic radiation?

A

-an incident electron directly hits an electron within the K shell knocking this electron out (ejected orbital electron)
-k shell is now unstable
-electron from L shell drops to K shell
-the excess binding energy from the L shell is released as xray photon
-the cycle continues for each shell

25
Q

what kV must x ray tube operate ate for characteristic spectrum to be produced?

A

above 69.5kV (if below this will only produce branstraulling radiation)

26
Q

what are the energy levels of K shells?

A

58-69 kV

27
Q

what ways can x-rays interact?

A

-scattered no energy loss
-absorbed-total energy loss
-mix of both
-transmitted unchanged

28
Q

what is an internal scatter?

A

when an xray passes down into the patients body

29
Q

in free space, how do X-rays travel?

A

in a straight line

30
Q

how do multiple X-rays travel?

A

divergently in a beam

31
Q

can X-rays travel through vacuum ?

A

yes

32
Q

are x rays detectable by humans?

A

no

33
Q

what do X-rays do?

A

produce image on film emulsion

34
Q

do x rays cause ionisation?

A

yes

35
Q

do x rays cause biological damage?

A

yes

36
Q

what is the radiation dose?

A

the amount of radiation absorbed by the patient

Radiology (4 decks)

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