6. X-Ray Hardware

Question 1

what is beam filtration and what does it do to the beam

Answer 1

filtration hardens the x-ray beam

Question 2

the standard bremsstrahlung spectrum is formed by which type of filtration

Answer 2

inherent filtration of machine

Question 3

what is beam hardening

Answer 3

increases average energy of x ray beams by removing the lower energies because of presence of filtrating materials

lead to only higher energy beam passing through so higher quality

Question 4

why are low energy photons undesirable

Answer 4

Low energy photon very unlikely to exit patient so not contributing to image quality at all so bad for patient as extra energy/radiation without any image benefits

Question 5

what happens to the k edge of attenuation as you increase keV

Answer 5

increases but at a certain point you match the e- orbital and get extra absorption of photon and more attenuation

Question 6

contrast between tumor and breast tissue gets smaller with increasing/decreasing kV

Answer 6

increasing

increase kV = lower contrast

Question 7

what are compensating filters

Answer 7

modifies the x-ray beam intensity across the field of view

Question 8

what is added filtration

Answer 8

filtration that is added to the port of x-ray tube

Question 9

what does added filtration do in terms of the photon energy

Answer 9

absorbs more low energy photons while higher energy photons can exit

Question 10

what are inherent filtration

Answer 10

filtration that is permanently in the path of the x-ray beam

Question 11

what are the 3 components that contribute to the inherent filtration

Answer 11

envelope of the tube

oil that surrounds the tube

window of tube housing

Question 12

what is the total filtration

Answer 12

sum of added and inherent filtration

Question 13

what is compensating filtration

Answer 13

added to the primary beam to alter its intensity

used to image areas that are non-uniform in makeup and assist in producing more consistent exposure to the IR

Question 14

what is the heat unit

Answer 14

amount of heat produced from any given exposure

Question 15

what 2 factors does the HU depend on

Answer 15

type of x-ray generator

exposure factors selected

Question 16

what is the equation for HU

Answer 16

HU = mA x time x kVp x generator factor

Question 17

what are tube rating charts

Answer 17

gives the max current that you can run through the x-ray tube

Question 18

what are the 2 factors that need to be satisfied in terms of the machines voltage source

Answer 18

Need to get voltage as high as we need

Need a way to keep voltage constant with the machinery

Question 19

what are the 2 types of diodes in terms of bias

Answer 19

forwards and reverse bias

Question 20

what are diodes and what are they made of

Answer 20

Diodes are solid state electrical device, has semi conductor type materials in it

allows current flow in one direction and restricts it in another (acts as a one way switch)

Inside you have 2 materials, one which we made slightly more positive than the other and the other you dope with some positive charge with some insulating material in the middle

Question 21

what are forward bias diodes and what is their charge distribution

is there conduction

Answer 21

Top positive (where the + charges are) bottom negative (where the - charges are)

Positive charges are repelled downwards and produces a current and allows current to go through so is in the conductive state

e- and holes more across the junction

conduction

Question 22

what are reverse bias diodes and what is their charge distribution

is there conduction

Answer 22

Top negative (where the + charges are) bottom positive(where the - charges are)

they’re attracted to opposite charge so don’t flow through insulating material and no conduction as stay away from junction in the middle

e- and holes stay away from the junction

no conduction

Question 23

when the diode acts in a forward bias in a AC current what does the diode become in terms of conduction

Answer 23

becomes conductor

acts like a closed circuit

Question 24

when the diode acts in a reverse bias in a AC current what does the diode become in terms of conduction

Answer 24

diode does not conduct

no current flow

Question 25

a diode in a AC circuit produces what

Answer 25

half rectified waveform

Question 26

what does the diode do to the waveforms in a AC current

Answer 26

Can take signal that’s alternating and makes it completely positive so when its negative there's no current at all but when its positive it allows current to flow

Question 27

what are transformers and what do they do in a electrical circuit

Answer 27

transfers electrical energy from one circuit to another used to step up/down the voltage from an AC power supply

Question 28

the coils in transformers are not connected so what transfers the power

Answer 28

magnetic field As each turn creates a magnetic field

Question 29

for transformers the amount of current produced depends on what

Answer 29

Amount of current you produce depends how many coils on the wire there are

Question 30

more secondary turns in a transformer than primary turns means there is an increase/decrease in voltage what has happened to the power

Answer 30

More turns on the right means there is an increase in voltage = steps up the power Takes the energy and steps it up due to difference in number of turns you can also do the opposite if needed

Question 31

what are the 3 circuits in a full x-ray circuit

Answer 31

Primary filament secondary

Question 32

what is the purpose of the primary circuit in the full x-ray circuit

Answer 32

Primary = control parameter and produce power,

Question 33

what is the purpose of the filament circuit in the full x-ray circuit

Answer 33

Filament circuit controls heating of filaments so release e-

Question 34

what is the purpose of the secondary circuit in the full x-ray circuit

Answer 34

Secondary circuit allows rectifying and flattening out the waveform

Question 35

what is Electromagnetic induction

Answer 35

a changing magnetic field induces an electrical potential difference (voltage) in a nearby conductor and also in which a voltage is induced in a conductor moving through a stationary magnetic field.

Question 36

in Electromagnetic induction the magnitude of the induced voltage is proportional to what factor

Answer 36

The magnitude of the induced voltage is proportional to the rate of change of the magnetic field strength.

Question 37

what are power ratings

Answer 37

The power rating of an x-ray tube or generator is the maximal power that an x-ray tube focal spot can accept or the generator can deliver.

Question 38

what is an anode heating chart

Answer 38

shows the anode heat loading for various input powers (kW or HU/s) as the x-ray tube is operating, taking into account the cooling that simultaneously occurs

Question 39

the anode cooling curve is steeper for larger/smaller anode heat capacities

Answer 39

With larger anode heat capacities, the anode cooling curve is steeper

Question 40

what does the primary circuit do in terms of the power

Answer 40

supplies power from the mains to the x-ray circuit

Question 41

why are circuit breaker included in the primary circuit

Answer 41

protect against short circuits and electric shocks

Question 42

what 2 things does the primary circuit control and what one factor does it monitor

Answer 42

controls tube voltage and exposure time monitor tube voltage

Question 43

what are the 6 components of the primary circuit

Answer 43

power supply mains power switch circuit breaker tube voltage selector voltage meter exposure timer

Question 44

what do auto transformers do in the primary circuit

Answer 44

allows selecting of different powers

Question 45

what are the 4 components of the secondary circuit

Answer 45

step-up transformers rectifier current meter x-ray tube

Question 46

what does the secondary circuit monitor

Answer 46

tube current (mA) only monitoring NOT setting it!

Question 47

what does the secondary circuit do in terms of the power type and voltage

Answer 47

convert AC to DC power creates potential difference across the x-ray tube (for e- to accelerate) step up voltage to voltage that is suitable for x-ray production

Question 48

how many diodes are in the secondary circuit how many will let current through and how many wont what do they allow the current to do

Answer 48

4 2 will, 2 wont allow current to flow in a forward reaction

Question 49

there is a positive tube voltage when there is a ____ ___ ___

Answer 49

positive input voltage

Question 50

there is a negative tube voltage when there is a ____ ___ ___

Answer 50

negative input voltage

Question 51

what does the bridge rectifier in the secondary circuit produce in an AC circuit what does this mean for the voltage

Answer 51

fully rectified waveform negative voltage isn't just removed, it's also turned into a positive waveform

Question 52

what is the voltage ripple how is it dealt with

Answer 52

Ripple = difference between highest and lowest point Take maximum of each one that’s going out of phase, produce a lower ripple

Question 53

why do we need to reduce voltage ripple

Answer 53

get a higher quality x ray and higher average x ray that gets rid of lower energy and makes most of characteristic peaks

Question 54

what does the filament circuit control how is this accomplished

Answer 54

controls the tube current (mA) change resistance to change the current

Question 55

what 3 things does the filament circuit do in terms of the filament

Answer 55

selects the filament to be used produces a current in the filament initiate thermionic emission

Question 56

what % of energy is converted to x-rays what is the rest converted to

Answer 56

1% = x-rays 99% = thermal energy (heat)

Question 57

what is the power rating in terms of the focal spot and the generator

Answer 57

max power that a x-ray tube focal spot can accept | max power that x-ray generator can deliver