Production of Xrays

Question 1

what are the main components of the equipment used to take an xray?

Answer 1

tubehad
collimator
positioning arm
control panel
circuitry

Question 2

component of glass x ray tube?

Answer 2

filament
copper block
target

Question 3

what kind of transformers are part of the xray tube?

Answer 3

step up transformer high kv across x ray tube

step down transformer low filament mA

Question 4

what may the glass have?

Answer 4

a lead free window while the rest is leaded

Question 5

what is the purpose of the lead shield?

Answer 5

minimises radiation leakage

Question 6

what is the purpose of the oil?

Answer 6

facilitate heat removal

Question 7

what does the aluminium filter do?

Answer 7

remove soft low energy damaging x rays

Question 8

what is the purpose of the collimator?

Answer 8

restrict size and shape of beam

Question 9

what is BID?

Answer 9

beam indicator device

part of collimator

Question 10

how is an xray produced? what first happens in the filament?

Answer 10

small electric current is passed through 8-10mA
passed through a step down transformer
filament heated by current because of excitation of electrons in the wire

Question 11

how is an xray produced - what happens to the electrons after the current heats the filament?

Answer 11

electrons lost from the outer shell
produce an electron cloud by free electrons surrounding
step up transformer 240V = 50-90kV

Question 12

production of an xray, what does the focusing cup do?

Answer 12

focusing cup points electrons towards focal spot on anode
negative electrons attracted to positive charged anode
pulled across by high kv between cathode and anode
electrons = high energy and fast moving

Question 13

production of an xray, what happens once the electrons are pulled across to the cathode?

Answer 13

electrons hit target and come to a sudden stop
electrons lose energy
energy conversion = 99% heat, 1% xrays

Question 14

last stage of production of an xray?

Answer 14

heat absorbed by copper
dissipated into surrounding oil 
xrays radiate in all directions
most absorbed by leaded glass
target = xrays through unleaded window
= beam of radiation emitted

Question 15

2 types of xray spectra?

Answer 15

1. continuous spec - brehmstrahlung. eide range of photon energies
2. characteristic spec - depends on material in anode, emitted by loss of electrons from k/l shells

Question 16

x ray properties?

Answer 16

travel in straight lines in free space
xray photons form a divergent beam
can travel through a vacuum
penetrate matter
absorbed/scattered
human senses cant detect
cause - ionisation, biological damage, certain salts to fluoresce

Question 17

what is scattering?

Answer 17

random change in direction after hitting something

Question 18

what is absorption?

Answer 18

deposition of energy in the tissues

Question 19

what is intensity?

Answer 19

no. of xray photons in one area of the beam

Question 20

what is attenutation?

Answer 20

reduction in intensity of the beam b/c scattering and absorption

Question 21

what is ionisation?

Answer 21

removal of an electron from a neutral atom to give an electron and a positive ion

Question 22

what is penetration?

Answer 22

ability of photons to pass through into tissues/materials

Question 23

what are interactions of an xray beam?

Answer 23

completely scattered with no loss of energy
absorbed with total loss of energy
scattered with some absorption and some loss of energy
transmitted unchaged

Question 24

interactions of an xray beam at an atomic level?

Answer 24

raleigh scattering
photoelectric effect = pure absorption
conmpton effect = absorption and scatter
pair production = pure absorption

Question 25

what is the photoelectric effect?

Answer 25

incoming electron interacts with inner K shell
electron ejected with much energy
photoelectron undergoes further interactions
xray photon lost all energy and dissapears
inner shell vacancy replaced by an outer shell electron
excess energy = emmited as light/low energy xray
free electron captured
atomic stability and neutral state

Question 26

what is the compton effect?

Answer 26

incoming xray photons interact with loosely bound outer shell electron
electron ejected with some energy from xray and becomes compton recoil electron
compton electron can cause ionisaiton
remaining photon energy scattered
may undergo further compoton reactions
may undergo photoelectric reations
escape tissues into clinical environment