Radiation quantities and units

Question 1

what is Absorbed dose

Answer 1

The amount of radiation energy deposited per unit mass of tissue.

Unit is Gray

Question 2

What is Equivalent dose

Answer 2

Accounts for the type and energy of the radiation, reflecting on its biological impact (damaging power).
Different types of radiation have different doses.

Unit is Sievert

Equivalent dose = Radiation weighting factor x Dose

Question 3

What is Effective dose

Answer 3

Different tissues are assigned different tissue weighting factors, these are used to calculate the effective dose based on each organ, as tissues have different radio sensitivities.

Unit is J.Kg-1

Effective dose = Equivalent dose x the tissue weighting factor

Question 4

What are the four interactions radiation can have with matter

Answer 4

Coherent scattering
Compton scattering
Photoelectric absorption
Pair production

Question 5

What is coherent scattering

Answer 5

No change is energies, xray is changed direction

Question 6

What is Compton scattering

Answer 6

Photon gives the electron some energy ejecting the electron (ionisation) the xray itself is scattered.

Question 7

What is photoelectric absorption

Answer 7

Photon hits inner shell electron gets fully absorbed (transfers all its energy), ejecting the electron causing a L shell electron to take its space in the K shell and sends off a characteristic xray.

Question 8

What is pair production

Answer 8

It is where a high energy photon converts into an electron and positron.