Lecture 12

Question 1

Who invented the word radioactivity?

Answer 1

Marie Curie

Question 2

Where is radioactivity useful in medicine?

Answer 2

• It can kill living tissue so can be used to treat cancer.
• It is easily detected so can be used as a tracer for imaging.

Question 3

What are the negative impacts of radioactivity in medicine?

Answer 3

Radioactivity can cause cancer

Question 4

_____ ______________ are generated from ionisation of water molecules.

Answer 4

Free radicals

Question 5

Describe the process of free radical production

Answer 5

Question 6

How do free radials and/or direct ionisation cause points of defects in DNA?

Answer 6

They cause point defects in DNA that can break either one or both strands.

Question 7

What is the hardest type of damage to DNA to repair?

Answer 7

Double strand breakages.

Question 8

How do genetic mutations occur at points in DNA?

Answer 8

Free radicals damage DNA frequently and the DNA is usually repaired, however, sometimes the cells stay damaged. Damaged cells either undergo apoptosis or replicate.

Question 9

What is the result of the replication of damaged cells?

Answer 9

• Cancer
• Hereditary genetic effects (if in the sperm or egg).

Question 10

What are the three basic types of radiation effects?

Answer 10

• Stochastic
• Deterministic
• Hereditary (genetic)

Question 11

Define stochastic effects of radiation

Answer 11

An effect that could occur at any dose of radiation, down to zero dose. The severity of the effect is independent of the dose but the probability of an effect increases with dose (linearly). This is a statistical assumption as there isn’t sufficient data in the low data range.

Question 12

Define deterministic effects of radiation

Answer 12

An effect that requires a certain level of radiation before it can occur, giving a threshold value. Below the threshold there is no effect and above the certainty and severity of the effect increases with dose.

Question 13

Define hereditary effects of radiation

Answer 13

Genetic effects are assumed to have stochastic incidence, however, the effects manifest themselves in future generations.

Question 14

What are the effects of 3-5 Gy of radiation (and what effect does that have on the time to death)?

Answer 14

Hematopoietic syndrome in bone marrow: the production of red blood cells is stopped.

Time to death: 30-60 days

Question 15

What are the effects of 5-15 Gy of radiation (and what effect does that have on the time to death)?

Answer 15

The gastrointestinal tract and lung epithelia are impacted.

Time to death: 10-20 days

Question 16

What are the effects of >15 Gy of radiation (and what effect does that have on the time to death)?

Answer 16

The central nervous system is impacted.

Time to death: 1-5 days

Question 17

What is the radiation dose that causes permanent sterility in males and females?

Answer 17

Males: 3.5-3.6 Gy
Females: 2.5-2.6 Gy

Question 18

What is the radiation dose that causes temporary sterility in males and females?

Answer 18

Males: 0.15 Gy
Females: 0.6 Gy

Question 19

A _ __ dose of radiation on the skin causes erythema and at higher doses can cause ___________.

Answer 19

3 Gy
Ulceration

Question 20

What is the allowed radiation dose for the general public annually?

Answer 20

1 mSv (5 mSv if a medical procedure is required)

Question 21

What is the allowed radiation dose for a radiologist annually?

Answer 21

20 mSv

Question 22

What’s is the ALARA principle?

Answer 22

The as low as reasonably achievable principle. It is regulation that states that the use of radiation should be:
1- Justified
2- Optimised
3- In compliance with limits.

Question 23

A ______ __ dose of radiation on the lens of the eye causes cataracts.

Answer 23

2-10 Gy