1. X-Ray Production

Question 1

How are x-rays produced in the x-ray tube

What happens on the cathode side

Answer 1

the tungsten filament is heated and produces e- through thermionic emission

Question 2

How are x-rays produced in the x-ray tube

What happens on the anode side

Answer 2

e- produced at the anode side accelerate towards the anode and hits the metal target

Question 3

what type of electrode is the cathode

what is the role of the cathode in x-ray production

Answer 3

its a negative electrode

its the source of e-

Question 4

what type of electrode is the anode

what is the role of the anode in x-ray production

Answer 4

positive electrode

e-s attracted to the positive charge and accelerate towards it where they are stopped/decelerated

Question 5

what occurs at the anode in terms of energy that produces x-rays

what else does the process produce

Answer 5

kinetic energy of e- transferred to the anode (when e- strike target it loses energy which is the kinetic energy)

x-rays and heat are produced

Question 6

what material is the center of the anode made of

Answer 6

tungsten

Question 7

where do the x-rays leave the x-ray tube from

Answer 7

the window

Question 8

what does the vacuum in the x-ray tube prevent and do

Answer 8

it makes sure that the e- energy is undissipated so produces x-rays and prevents energy from being lost as heat

Question 9

what are the 2 types of anodes

Answer 9

stationary and rotating

Question 10

what is the limitation of the stationary anode and what is the benefit of the rotating anode

Answer 10

stationary = compact but wears and creates heat

rotating = larger and longer life as can tolerate higher mAs and dissipate more heat

Question 11

what 2 components make up the cathode

Answer 11

filament (large and small) and focusing cup

Question 12

what is the filament and what is its role in x-ray production

Answer 12

coiled tungsten wire

source of e- during x-ray production

filament current heats the tungsten filament and causes thermionic emission

Question 13

what is the focusing cup and what is its role in x-ray production

Answer 13

surrounds filament and open at one end to allow e- to flow from cathode to anode

purpose is the focus the e- stream, it does this with its negative charge which prevents the filaments emitted e- from spreading apart

Question 14

what are the 3 components of the rotating anode and how are they arranged in a x-ray tube

Answer 14

target, stator and rotor

rotor attached to target and the stator is found either side of the rotor

Question 15

what is the purpose of the anode target

Answer 15

metal that abruptly decelerates/stops e- in the tube current

either rotational or stationary

Question 16

what is the purpose of the stator and rotor

Answer 16

electric motor that turns the rotor

the rotor is connected to the target through the molybdenum anode stem

Question 17

what components of the x-ray tube prevent overheating

Answer 17

insulating oil

Question 18

which 2 types of interactions produce x-ray photons

Answer 18

bremsstrahlung and characteristic interactions

Question 19

in terms of the incident e- and x-ray production what occurs in bremsstrahlung interactions

Answer 19

incident e- is attracted to the nucleus but doesnt eject any e-s

incident e- loses energy and changes direction

excess energy is emitted as a photon

Question 20

which 2 factors impact the photon energy produced from a bremsstrahlung interaction

Answer 20

proximity to nucleus

atomic number

Question 21

how does increased proximity of the incident e- to the nucleus impact the photon energy produced from a bremsstrahlung interaction

Answer 21

closer = incr attractive forces = more energy lost = incr photon energy

Question 22

how atom size impact the photon energy produced from a bremsstrahlung interaction

Answer 22

larger atom = incr attractive force = incr photon energy

Question 23

is the range of energy produced for photons from bremsstrahlung interactions discrete or continuous

Answer 23

continuous

Question 24

what is a bremsstrahlung interaction

Answer 24

projectile e- completely avoids the orbital e- of the tungsten atom and travels very close to its own nucleus

the strong electrostatic force of the nucleus causes the e- to slow down

e- loses energy and change direction and energy lost produces an x-ray photon

Question 25

in the diagnostic energy range most of the interactions are characteristic/bremsstrahlung

Answer 25

bremsstrahlung interaction

Question 26

in terms of the incident e- and x-ray production what occurs in characteristic interactions

Answer 26

incident e- removes an e- from the inner k shell of the orbit via repulsion other e-s in the orbit falls form outer shell to inner shell to replace the removed e- x-rays are emitted in this process due to the energy difference created

Question 27

is the range of energy produced for photons from characteristic interactions discrete or continuous

Answer 27

discrete specific energies due to specific orbits

Question 28

Is there a difference in x-rays produced by bremsstrahlung and characteristic interactions at the same energy level

Answer 28

no they are the same simply produced by different processes

Question 29

the x-ray spectrum has what on its y and x axis

Answer 29

y = x-ray intensity x = energy (keV)

Question 30

what is the x ray quantity and how is this show on the spectrum

Answer 30

total number of x-ray photons area under whole curve

Question 31

what is x-ray quality

Answer 31

average energy of x-ray photons contained in x-ray beam/spectrum

Question 32

is the x-ray spectrum representative of the average energy

Answer 32

no

Question 33

why is there a lower and upper limit on the bremsstrahlung interactions on the x-ray spectrum

Answer 33

upper = cant produce more energy than it had to start with (need to apply more voltage to increase the upper limit) lower = doesnt go to 0 as its filtered by the x-ray tube and the tube components

Question 34

what is the tube current

Answer 34

the mA is the current of e- flowing from cathode to anode in the x-ray tube

Question 35

what is the space charge effect

Answer 35

e- from the filament during thermionic emission form a cloud around the filament called space charge tendency to prevent more e- boiled off the filament (number of e- is limited)

Question 36

what aspect of the e- in the tube current does kV control

Answer 36

speed at which they move

Question 37

in terms of quality and quantity what does the kV affect and how

Answer 37

quantity and quality higher quality = high energy and greater penetrability

Question 38

in terms of quality and quantity what does the mA affect and how

Answer 38

quantity, doesnt affect quality or energy more e- in the tube current the more x-ray produced

Question 39

what effect does exposure time have on the x-ray quantity

Answer 39

longer exposure time results in more e- moving in the tube current from cathode to anode more x-rays produced

Question 40

what is the anode heel effect

Answer 40

x-ray beams have higher intensity (number of x-rays) on cathode side but lower intensity on anode side

Question 41

why is the anode heel effect present

Answer 41

the x-rays produced leave in many directions and the x-rays produced at the anode side have further to travel and some are absorbed by the anode itself this reduces the x-ray numbers compared to the to photon produced in the direction of the cathode

Question 42

how can the anode heel effect be used advantageously

Answer 42

place cathode over thicker anatomy to produce a more even exposure

Question 43

what is the line focus principle

Answer 43

relationship between the actual focal spot and the effective focal spot by angling the anode target the actual focal spot can remain large and effective fs can be reduced in size (greater heat capacity and greater image quality achieved)

Question 44

what is the actual focal spot and what does it depend on

Answer 44

size of area on anode target that is exposed to e- from tube current depends on the filament size producing the e- stream

Question 45

what is the effective focal spot

Answer 45

focal spot size as measured directly under the anode target

Question 46

what is the difference between using small and large focal spots in terms of quality and exposures

Answer 46

large fs can withstand large exposures small fs can give better image quality

Question 47

the larger the anode angle, the larger/smaller the effective focal spot

Answer 47

larger

Question 48

In terms of the line focus principle what does biased and non biased mean for the voltage

Answer 48

Biased = voltage applied Non-biased = same voltage everywhere

Question 49

Effective focal spot is smaller/bigger near cathode & smaller/bigger near anode

Answer 49

cathode = bigger anode = smaller

Question 50

the smaller the anode target angle the smaller/bigger the effective focal spot size

Answer 50

smaller

Question 51

Total filtration in the x-ray beam includes which 2 types of filtration

Answer 51

inherent and added filtration

Question 52

the intensity of the x-ray beam is greater on the ___ side of the tube

Answer 52

cathode

Question 53

the clouds of e- that forms before x-ray production is referred to as ___ ____

Answer 53

space charge

Question 54

what % of kinetic energy is converted to heat when moving e-strike the anode target

Answer 54

99%