++++Lecture 8 Flashcards

1
Q

Radiation life-shortening?

A

1-5% reduction in remaining life expectancy per Sv for acute exposure

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2
Q

Life shortening has been observed in

A

US radiologists * and the A-bomb survivors

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3
Q

life shortening also attributed to?

A

cancer and cancer with age specific diseases.

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4
Q

Life shortening for Mouse study displays?

A

increased relative risk with increased radiation dose.

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5
Q

Effects of IR on embryo?

A

pre- and neo-natal death *growth retardation *abnormalities *post-natal induction of cancer

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6
Q

In utero effects

A
  • cells are more sensitive to IR than adults

- Larger life expectancy through adverse effects

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7
Q

The three stages of embryonic development?

A

The preimplantation
Organogenesis
fetal

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8
Q

Preimplantation stage

A

-Stage of conception until fetilised egg attaches to uterus wall 0-9 days
Pre-natal death is most common in this stage
-0.05Gy can kill
LD 50/30=1

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9
Q

The peak incidence of abnormalities is during what stage?

A

Organogenesis (10 days to 6 weeks)
CNS very sensitive
0.2Gy can increase some abnormalities
LD 50/30=1.5

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10
Q

Possible effects of organogenesis?

A

Malformation of organs

Small head size

Intrauterine growth retardation

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11
Q

Fetal stage?

A

LD 50/30 is 2-3Gy
(growth stage)
8-16 weeks
Nervous system may be affected and carcinogenesis

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12
Q

Threshold for mental retardation?

A

0.2 Fy

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13
Q

Observed shift in IQ is?

A

30 points per Gy during sensitive period

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14
Q

Natural incidence of fatal childhood cancer is?

A

1 in 2000 people
200-250 deaths for under 10 yrs/10mSv
1-2 Leukaemia

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15
Q

Total cancer induction period is?

A

20 yrs but leukaemia risk is doubled during in utero stage

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16
Q

A absorbed dose of 0.1 Gy to an embryo (organogenesis) can result in?

A

pre natal death or IQ loss

17
Q

Risks of in-utero irradiation

A

0-2 wks Spontaneous abortion
2-10wks-Abnormality
2-15wks-Mental retardation
0-9mon-Cancer, growth retardation, genetic

18
Q

Are there any genetic effects?

A

In humans no data

19
Q

No human data because of?

A
  • long life cycle (we live too long)
  • studies require large populations > 1 million
  • too few offspring
  • large incidence of naturally occurring genetic damage
20
Q

Is there evidence of heritable mutations in humans

A

Yes

21
Q

Summary of Megamouse experiment?

A

Different gene loci have different rates of induction of mutation

  1. Mutation frequency is dose-rate dependent and sex dependent
  2. The time between irradiation and conception is important
  3. Magnitude of the effect depends upon the stage of sex cell irradiated
22
Q

Are males or females more sensitive on average?

A

Male
At high dose rates 1Gy/min same
as it decreases males more sensitive

23
Q

A delay in conception following irradiation means what?

A

reduces the effect of irradiation, due to repair (6 months)

24
Q

Are later stages of male and female sex cells more sensitive?

A

Mature sex cells by a factor of 5

25
Q

Doubling dose?

A

Doubles spontaneous rate
mutations per million 10mSv
(relative risk 1Gy)
(absolute risks 100 mutations/ 10mSv for future generations and 60 per million per 10mSv) mutations for working age population)

26
Q

Sundry effects of IR?

A

Sterility
cataract formation
skin damage
epilation