Production of X-rays part 2

Question 1

The higher the kVp the _______ the chances of having x-rays

Answer 1

higher

Question 2

What is electricity?

Answer 2

Flow of electrons through an electrical conductor

Question 3

What is current?

Answer 3

Amount of electrons flowing through a conductor per second. Measured in amperes (A).

• mA

Question 4

What is circuit?

Answer 4

Path of electrical current

Question 5

What is voltage (potential difference)?

Answer 5

Difference in electrical potential energy between two points in an electric circuit. Measured in volts (V).

Question 6

What do you need to turn a current from alternate to direct?

Answer 6

rectifier

Question 7

What type of current can pass through a transformer?

Answer 7

alternate current

Question 8

What type of current CANNOT pass through a transformer?

Answer 8

direct current

Question 9

During each half-cycle (1/120 of a second), anode is _______ and attracts the electrons from the cathode (x-radiation ____ produced).

Answer 9

positive
is

Question 10

During each alternate half-cycle (1/120 of a second), anode is ________, therefore, no attraction for electrons exists and x-radiation ____ produced.

Answer 10

negative
is not

Question 11

How many cycles of current happen per second in the USA?

Answer 11

60 cycles per second

Question 12

How many cycles of current per second do you need to make x-rays?

Answer 12

110 cycles per second

Question 13

If only alternate current was used in an x-ray machine what would happen?

Answer 13

electricity would go back and forth from anode to cathode and vice versa (x-rays only produced half of the time)

Question 14

What does a full wave rectifier do?

Answer 14

Only goes in one direction from max to zero and back again

Question 15

How do you go from alternating current from the wall to a direct current with a high mean energy?

Answer 15

1. Changing alternating current into direct current
2. Full-waive rectification, high frequency power supply
3. Essentially constant potential between cathode and anode.
4. Higher mean energy of beam compared to AC.

Question 16

What does a constant potential and direct current lead to in terms of…

exposure time
beam intensity
mean energy of beam
radiation dose

Answer 16

1. Shorter exposure times
2. More consistent beam intensity
3. Higher mean energy of beam
4. Decreased radiation dose

Question 17

How are x-rays produced?

Answer 17

X-rays are produced whenever high-speed electrons are suddenly decelerated or brought to a stop when they pass close to the nuclei of a high Z # absorbing material (in this case tungsten 74W)

Question 18

What are the two mechnanisms for x-ray formation?

Answer 18

• Bremsstrahlung radiation
• Characteristic radiation

Question 19

What is another term for breaking radiation?

Answer 19

Bremsstrahlung radiation

Question 20

What type of x-ray formation is electron to nucleus interaction?

Answer 20

Bremsstrahlung radiation

Question 21

What type of x-ray formation is electron to electron interaction?

Answer 21

Characteristic radiation

Question 22

What happens during Characteristic radiation?

Answer 22

◦ A few electrons interact with tungsten target orbital electrons, imparting enough energy to ionize the tungsten target.
◦ When electrons displace inner shell electrons, characteristic radiation is produced

Question 23

What happens during Bremsstrahlung radiation?

Answer 23

◦ The fast-moving electrons either slow down or stop when they come close to the nucleus of the atoms and part of their energy is transferred as X-rays.

Question 24

Bremsstrahlung radiation increases
with increasing what two components?

Answer 24

• the voltage (kV)
• the atomic number of the target (Z#)

Question 25

The higher the velocity,
the _______ the KE of electrons

Answer 25

greater

Question 26

What type of energy is lost when an impinging electron is deflected and decelerated than this energy is emitted as an x-ray photon?

Answer 26

kinetic energy

Question 27

What allows for the maximum energy photon from Bremsstrahlung radiation?

Answer 27

Head-on collision with nucleus

Question 28

What gets rid of the low energy x-rays?

Answer 28

aluminum filter

Question 29

Which type of x radiation has a wide distribution of wavelengths (heterogeneous)?

Answer 29

Bremsstrahlung radiation

Question 30

What is the reason that Bremsstrahlung radiation is heterogeneous (multiptle wavelengths)?

Answer 30

◦ Electrons lose their energies in random fashion when they interact with tungsten atoms.
◦ Multiple interactions between electrons and tungsten atoms.

Question 31

What happens to the electrons in Bremsstrahlung radiation?

Answer 31

At the anode they either interact with the nucleus or rapidly decelerate and get deflected (change of direction).

Question 32

How does characteristic radiation occur?

Answer 32

1. Arises when cathode electron collides with inner orbital electron of tungsten atom (target) and removes it from orbit.
2. Atom is now ionized and unstable.
3. Immediately, the hole left by the electron is filled by an electron from an outer shell, and energy is emitted from this electron in the form of x-radiation characteristic of tungsten and the involved shell

Question 33

The energy emitted in characteristic radiation by the electron is equivalent to…

Answer 33

the difference in the binding energies of the two shells/orbitals

Question 34

What is the characteristic radiation ev for L to K transition?

Answer 34

57,400 ev

Question 35

What is the characteristic radiation ev for M to K transition?

Answer 35

66,700 ev

Question 36

___% of diagnostic x-ray beam is characteristic radiation

Answer 36

30%

Question 37

_____________ radiation makes up the majority of the x-ray beam and produces a heterogeneous beam of varying photon energies

Answer 37

Bremsstrahlung

Question 38

____________ radiation is only a minor source of radiation from the x-ray tube and produces photon energies specific for the target material

Answer 38

Characteristic