physics 5

Question 1

Radiobiological effects of ionising radiation

Answer 1

cells undamaged: alterations mimic natural changes

cells damaged, repair, operate normal: breakdown of structure: the limited damage is repaired

cells damaged, repair, abnormal: incorrect function and damage to other cells, uncontrolled reproduction of these

cell damaged, death: they die dependent on sensitivity level

Question 2

define cellular radio sensitivity

Answer 2

varies directly with:
1. the rate of proliferation
2. number of future divisions,
3. inversely with the degree of morphological and functional differentiation

Question 3

how does radiation effect pregnancy?

Answer 3

Birth defects are only produced when acute doses are high enough to kill a relatively large proportion of cells in the embryo/fetus (>500 mSv).

Question 4

what happens when an embryo is exposed to high doses in early pregnancy before 10 days?

Answer 4

• fails to develop
• spontaneously aborts

Question 5

what happens when an embryo is exposed to high doses in early pregnancy after 40 days?

Answer 5

• low birth weight
• delayed growth
• possible mental deficits

Question 6

what are safe and unsafe limits of dose?

Answer 6

<0.25 Sv

but more is bad

10 Sv - death

Question 7

bone marrow suppression

Answer 7

over exposure of this can cause reduction in number of blood cells:
like:
- neutrophils
- leukocytes
- thrombocytes
- erythrocytes

can also cause:
- low white blood cell count
- low platelet count
- low blood cell count

Question 8

how to stop over-exposing to bone marrow?

Answer 8

take adequate steps:
- shielding areas with high concentrations of bone marrow if they are not in region of interest

Question 9

What are the 2 radiobiological effects?

Answer 9

• stochastic
• deterministic

Question 10

define the stochastic effects

Answer 10

Stochastic effects arise from cellular DNA damage which may lead to disease or future genetic defect

incorrectly repaired damage resulting in a modified cell which may still be able to divide giving rise to a clone of modified cells that may eventually become malignant

Question 11

define the deterministic effects

Answer 11

Deterministic effects are due to irreparable damage resulting in immediate or eventual cell death. Once a threshold dose is reached irreparably damaged cells will display signs and symptoms

Question 12

define stochastic and deterministic in simple terms:

Answer 12

stochastic: The probability of the effect occurring is related to the radiation dose, but the severity of the resulting injury is not related to the dose.

deterministic: An injury whose severity increases with increasing absorbed dose.

Question 13

what are harmful tissue reactions in deterministic effects

Answer 13

erythema
cataracts
fibrosis
haematopoietic damage
acute radiation syndrome