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Flashcards in chapter 9 EXAM 4 Deck (64):
1

late effects

radiation induced damage at the cellular level that may lead to somatic and genetic damage in the living organism later in life

2

epidemiology definition

science that deals with the incidence, distribution, and control of disease in a population

3

dose response curves establish relationships between

radiation and dose response

4

radiation dose response relationship

graph that maps out the effects of radiation observed in relation to the dose of radiation received

5

horizontal axis of dose response curve =

dose received

6

vertical axis of dose response curve =

biologic effects observed

7

the curve on the dose response curve can be either

linear or non linear

8

the curve on a dose response curve can depict

threshold dose or non threshold dose

9

threshold relationship

a point at which a response or reaction to an increasing stimulation occurs
below a certain radiation level or dose, no biologic effects are observed

10

nonthreshold relationship

means that any radiation dose will produce a biologic effect
no dose is believed to be "safe"

11

what is the BEIR committee

committee on the Biologic Effects of Ionizing Radiation (BEIR)

12

the BEIR committee report of 1980 stated

the majority of stochastic somatic effects at low dose levels appear to follow a linear quadratic nonthreshold curve (LQNT)

13

the BEIR committee report of 1990 stated

the risk of radiation exposure was about 3-4 times greater than previously projected

14

currently BEIR committee recommends the use of what for most types of cancer

the linear nonthreshold curve

15

linear nonthreshold curve (LNT) implies

that the chance of a biologic response to ionizing radiation is directly proportional to the dose received

16

The LNT curve accurately reflects the effects of

high LET radiation at higher doses

17

deterministic (nonstochastic) effects of significant radiation may be demonstrated graphically through the use of a

linear threshold curve

18

the sigmoid or s-shaped (nonlinear) threshold curve is generally used in

radiation therapy to demonstrate high dose cellular response to radiation within specific tissues

19

somatic effects

biologic effects that occur in the living organism that have been exposed to radiation

20

non somatic effects

irradiation of an individuals genetic material leading to genetic malformation
called genetic/heritable effects

21

somatic effects may be subdivided into

1. stochastic effects
2. deterministic effects (nonstochastic effects)

22

stochastic effects

non threshold
mutational or randomly occurring biologic changes independent of dose
ex: cancer

23

deterministic (nonstochastic) effects

effects directly related to the dose received
cell killing effects that exhibit a threshold dose
ex: cataracts

24

late somatic effects

consequences of radiation exposure that appear months or years after exposure

25

late deterministic somatic effects are directly related to

the dose received

26

late stochastic effects

do not have a threshold and occur in random and have a severity that is not dose dependent

27

low level radiation is defined as

an absorbed dose of 0.1 Sv (10rem) or less delivered over a short period of time

28

a typical routine chest xray is about what dose

0.06 Sv (6mrem)

29

3 major types of late effects

1. carcinogenesis
2. cataractogenesis
3. embryonologic effects

30

absolute risk model predicts

that a specific number of excess cancers will occur as a result of exposure

31

relative risk model predicts

that the number of excess cancers will increase as the natural incidence of cancer increases with advancing age
predicts a percentage increase rather than a specific number of cases

32

what is the most important late stochastic somatic effect caused by exposure to ionizing radiation

cancer

33

radium watch-dial painters

1920-1930 pointed their radium containing brush tips with their lips and spit
this caused
osteoporosis
osteogenic carcinoma
other malignancies

34

uranium miners

they mined uranium and sustained lethal doses of radiation caused by breathing dust and drinking radioactive water
died from cancer and respiratory diseases

35

early medical radiation workers

exposed to large amounts of radiation
developed cancerous skin lesions
higher incidence of aplastic anemia and lukemia

36

pts. injected with contrast agent thorotrast

1925-1945
radioactive material emitted alpha particles and were deposited in pts.
causing liver and spleen cancer
angiosarcoma
biliary duct carcinomas

37

infants treated for enlarged thymus gland

1940-50s infants were treated with therapeutic doses to reduce size of thymus gland
resulted in development 20 yrs later of thyroid nodules and carcinoma

38

children of the marshall islanders

children on neighboring islands received substantial absorbed doses to thyroid from external and internal exposures

39

ethos projects

research project in aftermath of chernobyl

40

nonspecific life span shortening

the reduction in life cycle due to radiation

41

the probability that a single dose of radiation about 2 Gy (200rad) will induce formation of cataracts is

high

42

neutron dose of what has been known to cause cataracts in mice

a neutron dose of 0.01 (1 rad)

43

radiation induced cataracts in humans follow a

threshold nonlinear dose response relationship

44

3 stages of gestation in humans

1. preimplantation
2. organogenesis
3. fetal stage

45

irradiation of embryo dureing the first 12 weeks of development to EqD in excess of 200 mSV (200rem) frequently results in

death or causes congenital abnormalities

46

when a high dose of radiation is received witihin aprox. 2 weeks of fertilization, what happens

prenatal death and usually results in spontaneous abortion
if this does not happen pregnancy will continue with no adverse effect

47

if during the preimplantation stage you are irradiated with a dose in the range of what, what will occur

in a dose of 0.05-0.15 Gyt
embryonic death will occur

48

during oganogenesis if you are irradiated,

fetus is more susceptible to abnormalities such as growth inhibition, mental retardation, microcephaly, genital deformities etc.

49

if radiation occurs during late stages of organogensis,

the presence of abnormalities in the fetus will cause neonatal death

50

the United Nations Scientific Committee on Effects of Atomic Radiation proposed an upper limit combined radiation risk for these fetal effects to be

3 chances per 1000 children for reach rem of fetal dose (0.3%)

51

international chernobyl project

study compared seven contaminated russian villages with 6 uncontaminated villages

52

spontaneous mutations

a natural phenomenon involving alterations in genes and DNA
occur at random and without a known cause
are permanent and heritable and can be transmitted from 1 generation to the next
cause a wide variety of disorders/diseases

53

mutagens

agents that increase the frequency of occurrence of mutations

54

agents of mutagens include

elevated temps.
ionizing radiation
viruses
absorption of certain chemicals

55

what is one of the more effective mutagen

ionizing radiation

56

because mutant genes cannot properly run cell's normal chemical reactions, it results in

various genetic diseases

57

point mutations

genetic mutations in which the chomosome is not broken but the DNA within it is damaged
may be either dominant or recessive

58

dominant point mutations

expressed in offspring

59

recessive point mutations

not expressed for several generations

60

radiation is thought to cause what mutations

primarily recessive mutations

61

in order for recessive mutation to appear in offspring, both parents must have

have the same genetic defect, therefore it is not likely to appear in a population

62

damage from recessive mutations may sometimes manifest itself more subtly and may appear as

allergies
slight alteration in metabolism
decreased intelligence
predisposition to certain diseases

63

doubling dose is

the radiation dose that causes the number of spontaneous mutations occurring in a given generation to increase to two times their original number

64

for humans the doubling dose is estimated to have a mean value of

1.56 Sv (156 rem)