radiation physics

Question 1

In what part of the EM spectrum do you find X-rays?

Answer 1

In the ionising radiation sector.

Question 2

Describe x-rays in terms of their wavelength and energy.

Answer 2

SHORTER WAVELENGTHS with HIGHER ENERGY.

Question 3

What is the x-ray tube target made out of?

Answer 3

Tungsten

Question 4

Why is the x-ray tube target made out of tungsten?

Answer 4

Due to its high melting point.

Question 5

What is the x-ray tube surrounded by?

Answer 5

A glass envelope creating a vacuum.

Question 6

What potential difference is used?

Answer 6

70 kv

Question 7

What happens to the electrons in the continuous spectrum?

Answer 7

The incoming electrons are slowed down and deflected to varying degrees, producing a complete range of x-ray photon energies.(the continuous spectrum is the CONTINUOUS line)

Question 8

Where on the graph is the highest energy of x-rays to be produced?

Answer 8

Where the line hits the X-axis but this is 0.

Question 9

What is the characteristic spectrum?

Answer 9

Photon energy emissions characteristic of the tungsten target.

Question 10

What element is used to selectively filter the beam?

Answer 10

Aluminium

Question 11

What is the purpose of the aluminium filter?

Answer 11

To absorb the low energy, harmful x-rays so they are not absorbed by the body.

Question 12

What determines the quality of the x-ray beam?

Answer 12

Voltage (kV)

Question 13

Which factor affects the film contrast?

Answer 13

Voltage (kV)

Question 14

Which factor determines the QUANTITY of the x-ray photons?

Answer 14

time and current (mA)

Question 15

What occurs during the photoelectric effect?

Answer 15

1. The x-ray hits the electron and causes it to shoot off.
2. Electron is ejected and this is the photoelectron.
3. The vacancy from the ejected electron is filled by an electron dropping in from the outer shells.
4. Excess energy is released via characteristic radiation.

Question 16

Why are photoelectrons damaging?

Answer 16

Because of the impact it may have elsewhere in the body.

Question 17

What occurs during Crompton scatter?

Answer 17

The x-ray photon interacts with an outer electron, changes direction (scatters) and loses energy.

Question 18

Where does Crompton scatter occur?

Answer 18

Not dependent on any factors - OCCURS IN ALL TISSUES EQUALLY.

Question 19

Which interaction is responsible for producing contrast?

Answer 19

PHOTOELECTRIC EFFECT - produces contrast between the different atomic numbers.

Question 20

Which 2 types of abnormality are caused by direct damage?

Answer 20

1. Radiation induced malignancies (somatic cells)
2. Congenital abnormality (genetic cells)

Question 21

How does indirect damage occur?

Answer 21

Electron interacts with a water molecule, producing harmful free radicals.

Question 22

Deterministic effects on the oral cavity.

Answer 22

1. Mucositis
2. Loss of taste
3. Xerostomia
4. Radiation-induced caries
5. Tooth defects if developing teeth are irradiated

Question 23

Radiation Absorbed Dose

Answer 23

Amount of energy absorbed from the radiation beam per unit mass of tissue.

(amount coming out of the x-ray tube)

Question 24

Equivalent Dose

(type x = type y)

Answer 24

Allows the radiobiological effectiveness of different types of radiation to be compared.

Question 25

Effective Dose

Answer 25

Allows investigations of different parts of the body to be compared by converting all doses to an EQUIVALENT WHOLE BODY DOSE.