Biological Effects

Question 1

2 types of radiation

Answer 1

byproducts of radioactive decay
- alpha, beta, gamma ray

artifically produced EM
- xray

Question 2

ionising radiation
what is it and effect

Answer 2

energy to turn atoms to ions

causes DNA damage
cancer
mutations

Question 3

direct vs indirect DNA damage

Answer 3

direct -
radiation interacts with atoms in dna

indirect -
interacts with water in cell, free radicals, damage due to instability and reactive nature

Question 4

tissue sensitivity
stem vs differentiated cells

Answer 4

stem -
very radiosensitive
the more rapidly the cell dividing, the more sensitive
[bone marrow, lymphoid]

differentiated -
less radiosensitive
[CNS, bone, cartilage]

Question 5

absorbed dose

Answer 5

measure of energy deposited
gray (Gy)

Question 6

equivalent dose

Answer 6

absorbed dose multiplied by weighting factor depending on type of radiation
sieverts (Sv)

Question 7

Linear No Threshold (LNT) model

Answer 7

assumes damage directly proportional to radiation dose
assumes always harmful with no safety threshold

ALARP

Question 8

deterministic vs biological effects

Answer 8

deterministic -
tissue reaction, related to dose, several days after

stochastic -
related to dose, no threshold, cannot predict
years later
somatic = disease/disorder
genetic = descendants

Question 9

pregnancy and radiation
lethal dose
what gestation weeks most critical

Answer 9

1000Gy lethal before or immediately after inplantation

during organogenesis 2-8 weeks
>250mGy could lead to growth retardation

Question 10

what is the annual background radiation dose

Answer 10

2.2mSv

Question 11

how far should the controlled area extend from xray tube and pt

Answer 11

1.5mm

Question 12

diagnostic reference levels

Answer 12

established doses for typical standard procedures

Question 13

how to optimise image quality

Answer 13

CR plate prone to damage via teeth marks so insert between two plastic sheets

images with minor artefact should be saved