Radiation: PP1

Question 1

What is Radiation?

Answer 1

Emission or transmission of energy in the form of waves or particles through space or a material medium

Question 2

What are the two main types of radiation that we are concerned with?

Answer 2

Electro-magnetic: eg radio waves, x-rays, gamma rays

Partical Radiation: alpha, beta, and neutron radiation. Radioactive fission, fusion and decay

Question 3

Ionising:

Answer 3

Process of knocking electrons out of the valence shell of atoms

Question 4

What damage can Ionising Radiation cause?

Answer 4

Exposure to ionising radiation can cause damage to living tissue resulting in mutation, cancer, radiation sickness and death.

Question 5

Sources of Ionisation Radiation:

Answer 5

Background:

Artificial radiation:

Question 6

Examples of Background Radiation

Answer 6

• radon and thoron (gases)- decay products of uranium 238 exposure due to inhalation
• Terrestrial Radiation: radioactive materials from 4.5 billion y/a
• Internal Exposure: ingestion of radio nucleotides (40K or 14C)
• Cosmic Radiation: rays interacting with atoms from outer space

Question 7

What are examples Artificial Radiation

Answer 7

Medical exposure: largest controllable exposure

Consumer products and activities: air travel- increased cosmic, building materials, smoking

Question 8

Radiation quantities and units:

Answer 8

Exposure (X)
Absorbed Dose (D)
Equivalent Dose (H)
Effective Dose (E)

Question 9

What is Exposure (X)?

Answer 9

The amount of charge produced by ionising radiation per mass unit of air.

SI Unit: colombs per kilogram (C/kg)

X= Charge/ Mass (air)

Question 10

KERMA

Answer 10

kinetic energy released in matter

Question 11

Absorbed does (D)

Answer 11

the amount of energy being transferred (absorbed) into an object.

SI Unit: Grey (gy)

D= Energy/ Mass (matter)

Question 12

Equivalent Dose (H)

Answer 12

This is the quantity used for radiation protection and expresses dose on a common scale for all types of radiation. While taking into account the ability of different types of radiation to produce damage.

SI Unit: Sievert (sv)

H= D1x Wr1 + D2x Wr2 +…
*Multiply the absorbed does (D) by radiated weighting factor (Wr) and add all contributing factors

Question 13

Effective Dose (E)

Answer 13

Takes into account that different tissues have different sensitivities to radiation. Is used to work out risk- included tissue wighting factor (Wt)

SI Unit: Sieverts (sv)

E= H1x Wt1 + H2x Wt2+…
*multiply equivalent does (H) by Wt and add up contributions of each tissue

Question 14

What does DAP stand for?

Answer 14

Dose Area Product (DAP).
SI Unit: mGy.cm2
It measured the radiation does to air multiplied to the area of the x-ray field.

Question 15

How can DAP results be changed?

Answer 15

• Altering technique factors – kVp, mA or time
• Varying the size of the area of the exposed field

Examples:
A 5 x 5cm x-ray field with an entrance dose of 1 mGy will yield 25 mGy.cm2.
Increasing the x-ray field to 10 x 10cm at 1 mGy will yield 100 mGy.cm2 (4 times)
Back to 5 x 5cm x-ray field with an entrance dose of 2 mGy will yield 50 mGy.cm2