How Xrays Are Produced

Question 0

Label the components of the X-ray machine? (4)

Answer 0

Cone
X-ray head
Arm
X-ray control box

Question 1

What comprises the tube head?

Answer 1

Metal housing
Transformers
     Step up transformer
     Step down transformer
X-ray tube
Oil
Collimators lined with lead
Aluminum filters
Aiming cylinder

Question 2

What does the X-ray tube consist of?

Answer 2

Cathode

Anode

Question 3

Cathode

Answer 3

• charged
  Tungsten filament
  Produces electrons to be accelerated
  Molybdenum focusing cup

Question 4

Anode

Answer 4

\+ charged
Focal spot (tungsten) located in a copper stalk

Question 5

Step up transformer

Answer 5

Will increase voltage
PROPEL ELECTRONS FROM CATHODE TO ANODE.
The max energy of the X-ray photon is equal to the voltage the step up transformer is set at

Question 6

Step down transformer

Answer 6

Reduces incoming voltage

Creates electrons as the cathode at the filament

Question 7

What is Bremsstrahlung X-rays?

Answer 7

Created when high speed electrons interact with tungsten nuclei in the target resulting in a spectrum of X-rays with different energies.

Accounts for the bulk of X-ray photons produced

Question 8

High energy bremsstrahlung X-ray

Answer 8

Electrons directly collide with a nucleus, producing a high energy photon (keV) - that is equal in energy to. The incident electron

Question 9

Medium energy bremsstrahlung X-ray

Answer 9

Produced by electrons passing close to the nucleus causing deflection and deceleration of the electron. The deceleration causes the electron to lose some energy in the form of photon radiation.

Question 10

Low energy bremsstrahlung X-ray

Answer 10

Produced when the electrons pass at a distance from the nucleus. They are deflected and slowed somewhat producing a low energy photon.

Path not altered dramatically

Question 11

What is characteristic radiation?

Answer 11

Electrons collide with an orbiting inner electron ejecting it from orbit. The electron in the higher ring will drop down to the lower ring to fill in. This drop releases energy. The energy. Is released in the form of a photon

Inner ring has the lowest binding energy
Accounts only for a small fraction of X-rays

Question 12

The X-ray tube is a vacuum tube - why?

Answer 12

No gas molecules for the electrons to hit into, no oxidation or burnout (combustion)

Question 13

What is the focal spot?

Answer 13

Where the stream of X-ray photons originate.

Placed at an angle to shoot the X-ray photons out and creat an effective focal spot for sharp images

Question 14

What is a molybdenum cup?

Answer 14

Found in the cathode - focuses the electrons towards the anode and narrows the beam of electrons

Question 15

What is the auto transformer?

Answer 15

Controlled by the kVp dial on the control panel. This transformer varies the voltage to the step up transformer to abide the desired high energy kVp to the tube

Question 16

What is the most frequent malfunction of the X-ray tube?

Answer 16

Filament burnout

The X-ray unit should be left on all day to prevent this for as long as possible. Turning it on on off with keep heating and cooling the filament

Question 17

Why should you change the exposure time between field of teeth?

Answer 17

Molars - have more tissue to pass through

Incisors- less tissue

Question 18

What is the tube current mA?

Answer 18

The quantity if radiation produced
As mA is increased the number of electrons increases
More collisions more radiation

Question 19

More collisions means more radiation. T or F

Answer 19

True

Question 20

Increasing kVp increases the X-ray penetration of matter. T or F

Answer 20

True

Question 21

What is tube voltage kVp?

Answer 21

The energy used to propel the electron to strike the target.
Increasing the kVp increases in efficiency of the conversion of electonr energy into x ray photons.

Increase = more quantity and quality of radiation

Question 22

What is a collimator?

Answer 22

A metal barrier used to reduce the size of the X-ray beam. Lined with lead - absorbs stray photons

Question 23

The intensity if the xray beam is inversely proportional to the he square of the he distance between the source and the target. T or. F

Answer 23

True - the X-rays will ospreys out decreasing intensity. Having an effect on exposure

Question 24

What is coherent scattering?

Answer 24

Low energy photons are deflected by Outer ring electrons - emits a secondary photon at a different angle
Creates a foggy look on film

Question 25

What is photoelectric absorption?

Answer 25

Incident electrons are absorbed by an atom by interacting with inner shell electrons,
This makes the lighter areas of film
Depends on density and thickness - gives contrast to films
Photon strikes - electron ejected and quickly absorbed

Question 26

What is Compton scattering?

Answer 26

Photon interacts with an outer orbital electron
Accounts of 49% of interactions in dental radiography
Scattered electrons darken and degrade the image - no useful info
Photons strikes outer electron - lower energy photon ejected sling with a recoil electron

Question 27

How is the beam attenuated (refined)?

Answer 27

Lower energy photons are more readily absorbed

Question 28

Higher energy photons transmit easier through absorber. T or F

Answer 28

True

Question 29

Compton scattering vs Coherent scattering

Answer 29

Compton - higher energy photon, creates darkness on the film. Accounts for majority of scatter.

Coherent - low energy photon, creates fuzziness, accounts for little scattering