Late Effects of Radiation

Question 1

what are late effects and long term results od radiation exposure

Answer 1

Radiation-induced damage at the cellular level may lead to measurable somatic and genetic damage in the living organism as a whole later in life
- months to years after exposure

Question 2

Late effects of long term exposure may result from

Answer 2

• previous whole or partial body acute exposure (not at the diagnostic level)
• previous high radiation doses (cardiac cases with fluoroscopy)
• long term low level doses sustained over several years (various doses over years (general/fluoro/CT))

Question 3

Why are female germ cells sensitive?

Answer 3

follicles mature with the eggs - they are radiosensitive

Question 4

late effects are caused by what cells?

Answer 4

cells that are damaged but live

Question 5

non-stochastic late effect

Answer 5

late effects that can be directly related to dose received

Question 6

non-stochastic late effect syndromes

Answer 6

1. cataracts
2. sterility
3. fibrosis
4. atrophy

Question 7

stochastic late effect

Answer 7

late responses that do not have a threshold

Question 8

stochastic late effect syndromes

Answer 8

1. cancer
2. embryologic effects

Question 9

Most stochastic effects and genetic effects at low dose levels from low-LET radiation, appear to follow a linear non-threshold curve. What does this imply?

Answer 9

• Implies that the chance of a biological response is directly proportional to the dose received
• A model that may overestimate risk but is not expected to underestimate risk

Question 10

occupational exposure late effects

Answer 10

• thyroid cancer
• within 15 years of the discovery of x-rays, 100 cases of skin cancer were reported

Question 11

cataratogenesis

Answer 11

cataracts

Question 12

carcinogenesis

Answer 12

various cancers

Question 13

embryologic effects

Answer 13

birth defects

Question 14

cataracts

Answer 14

• cells die → cloud the lens
• There is a high probability that a single dose of approximately 2 Gy will induce the formation of cataracts.
• threshold dose of 10 Gy for chronic exposure
• latent period for chronic exposure - about 15 years

Question 15

What is the DL for the lens of the eye?

Answer 15

• 20 mSv equivalent dose per year averaged over a 5 year period and 50 mSv in any single year
• 15 mSv for members of the general public

Question 16

results of cataracts

Answer 16

• Partial or complete loss of vision
• Results of laboratory experiments with mice
• Radiation-induced cataracts in humans follow a threshold, nonlinear dose-response relationship

Question 17

what does the lens of the eye do?

Answer 17

• focuses length on the retina so that as the image forms it may be transmitted though the optic nerve

Question 18

what are examples of human radiation cataractogensis?

Answer 18

• Japanese bomb survivors
• nuclear physicists
• patients undergoing radiation treatments

Question 19

posible effects at low (diagnostic doses)

Answer 19

• No conclusive proof that doses below 0.1 Sv (10 REM) have a significant risk
• Low level radiation from: xrays and radioactive material (diagnostic procedures), employment related exposures, natural background
• cancer induction, genetic effects

Question 20

radium watch dial painters?

Answer 20

ingested radium on paintbrush
- developed bone cancer and cancer of sinuses

Question 21

uranium miners

Answer 21

inhalation of radioactive particles and radon gas
- lead to lung cancer (50%)
- families also affected from clothes

Question 22

early radiation workers

Answer 22

• anemia
• leukemia

Question 23

therapy for enlarged thymus

Answer 23

• thyroid cancer

Question 24

ankylosing spondylitis patients

Answer 24

• received radiation therapy
• RT was in high doses leading to leukaemia

Question 25

Japanese atomic bomb survivors?

Answer 25

- high incidence of leukaemia - increased breast cancer

Question 26

chernobyl nuclear disaster

Answer 26

- radiation syndromes - ongoing monitoring population

Question 27

what are genetic effects?

Answer 27

stochastic effects from damaged genes

Question 28

cause of genetic effects?

Answer 28

- Ionizing radiation is one of the most effective mutagens and can increase the frequency of genetic mutations - Even a non lethal dose to a germ cell can create genetic mutations which can be passed to successive generations - Because these genetic alterations are permanent and heritable they can be passed from one generation to the next

Question 29

what are frequent natural mutations

Answer 29

- huntingtons - Down-syndrome - Duchenne muscular dystrophy - cystic fibrosis

Question 30

where did the evidence of genetic effects come from?

Answer 30

- mice and fruit flies - GE's or hereditary effects do not have a threshold

Question 31

what are dominant mutations of germ cells?

Answer 31

expressed in an individuals offspring - only requires a mutated gene from one individual

Question 32

what are recessive mutations of germ cells?

Answer 32

not likely expressed for generations - requires a mutated gene from both parents

Question 33

genetic effects in the population

Answer 33

Ionizing radiation is thought to cause primarily recessive mutations, both parents must have this for it to be expressed - Defect must be located on the same part of a specific DNA base sequence in each parent - Rare, not likely to appear in the population at the diagnostic level

Question 34

how may damage from recessive mutation appear?

Answer 34

- allergies - alteration on metabolism - decreased intelligence - predisposition to certain diseases

Question 35

Dose doubling

Answer 35

- doubling dose is the radiation dose that causes the number of spontaneous mutations occurring in a given generation to increase to 2 times their original number

Question 36

doubling dose in humans

Answer 36

The radiation doubling equivalent dose for humans, as determined from studies of the children of the atomic bomb survivors of Hiroshima and Nagasaki, is estimated to have a mean value of 1.56 Sv.

Question 37

significance of mutations to a population

Answer 37

- leads to elevated health costs due to disease - lead to a possible change to the gene pool, more recessive diseases present