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Clinical T2 > X-ray > Flashcards

X-ray Flashcards

1
Q

principles for x-ray

A

beam of high energy electrons
interact with a target material
interact with patient tissue, some pass through
interact with image to produce grey scale

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2
Q

why is bone very absorbant

A

due to its high density and atomic no.

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3
Q

white parts of image

A

more energy absorbed

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4
Q

what is xray energy measured in

A

kVp

peak kilovolts

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5
Q

what is the role of aluminum filter

A

absorb low energy photons

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6
Q

what is the effects of a higher kVp

A

lower contrast - more grey

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7
Q

what is the effect of a lower kVp

A

high contrast

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8
Q

what is the amount of xrays measured in

A

mAs

milli amps x second

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9
Q

what is the relationship between density and absorption

A

linear

if you double density of tissue, you double absorption and scattering

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10
Q

role of image receptor

A

convert xrays energy to image

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11
Q

different types of receptor

A

film screen - chemical reaction
computed - sacnning laser
direct-direct - computing

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12
Q

how does direct - direct radiography work

A

as xrays pass through crystals, release electrons, they ionise and form current which is collected at the capacitor.
thin film tranistor is switched so the current is released

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13
Q

what should you look at to get a good image

A

amount of collimnation
centering - where the middle ray will be
limit diverging beam

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14
Q

generator

A

creates high voltage
made up of coils
primary and secondray (has more coils =higher current)
alternating current, changes direction of a magnetic field, generates voltage

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15
Q

order of electromagnetic spectrum

A 
radio 
microwaves 
infared 
ultra violet 
xrays 
gamma (highest)
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16
Q

useful characteristics of xrays

A

penetrate matter
interact with matter
can cause certain materials to fluoresce
can cause certain materials to produce electric charge

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17
Q

how are xrays generated

A

cathode produces electrons
filaments are heated, removing electrons
creates a high potenial difference between cathode and anode
electrons accelerate to anode

18
Q

why is the glass tube in oil

A

heat disserpation

electrical insulation

19
Q

properties of anode

A

good conductor
good heat disapator
made of tungston

20
Q

electricity

A

flow of electrons in a material and the rate of flow of electrons is a meaure of the electrical current

21
Q

potential force

A

is the ‘driving force’ which moves the electrons along a conductor, has an effect on kinetic energy, measured in kVp

22
Q

electric current

A

amount of current, determines the amount of thermionic emission, measured in milliampes mA

23
Q

3 ways which electrons collide with target

A
  1. interaction between them and outer electrons in the atom (no heat or xray)
  2. interaction between them and the nuclei of the atom (heat and xray)
  3. interaction between them and individual electron in the inner orbits (heat and xray)
24
Q

how much energy is produced as heat in xray production

A

95-99%

25
Q

quality of xray beam

A

measure of its penetraing power

26
Q

quanity of xray beam

A

measure of the number of photons in the beam

27
Q

why is funneling of xray important

A

saftey
only hits part of the body you want
less radiation exposure

28
Q

newtons law of conservation of energy

A

energy neither created nor desroyed, only changed in form

29
Q

why is tungsten used

A

heat stable
good electrical conductor
has alot of electrons
- positive protons in nucleus

30
Q

why do we have rotating andoes

A

heat diserpation
preserves the anode
more high energy eletrons

31
Q

andoe angle

A

makes source of xray as close to point source as possible

small angle = closer to point source = more effective source

32
Q

role of filtration

A

enriches beam with high energy photons by absorbing lower energy xrays
higher average energy
- greater penetration
- reduce skin dose

33
Q

ionisation chamber

A

gas filled
a propotion of incident photons cause ioniastion which is collected at the charged anode of the chambre
measure dose area product in cG

34
Q

generators

A

cathode needs low voltage so mulitple circuits
high voltage tranformer
voltage rectifier

35
Q

what does voltage rectifier do

A

converts oscilaiting voltage to constant voltage

36
Q

intensity across the beam

A

varies because electrons travel into deeper layers of the anode, deeper they go = lower intensity
increase as angle is reduced, side closest to andoe is lower

37
Q

fine focus filament

A

smaller
used when geometric focus limit image quality
energy focused on smaller area
reduce tube loading to prevent damage

38
Q

when is the fine focus filament used

A

high detail
low patient attenutaion
extremities

39
Q

broad focus filament

A

image limited by patient attentuation
increased heat dissipation
permits higher tube loading

40
Q

when is broad focus filament used

A

less detail required
high patient attenuation
chest, abdomen, l.spine

Clinical T2 (16 decks)

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