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SEM III - Radiation Biology > LET/RBE/OER & Direct/Indirect > Flashcards

LET/RBE/OER & Direct/Indirect Flashcards

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0
Q

RBE

A

Relative biological effectiveness

Biologic reaction compared to a standard

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1
Q

LET

A

Linear energy transfer

Energy deposited in tissue per unit of distance

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2
Q

Standard RBE

A

250 KV X-rays

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3
Q

OER

A

Oxygen enhancement ratio

Oxygen deprived versus oxygen rich environment

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4
Q

The amount of energy transferred to tissue per unit of distance travelled in tissue is

A

LET - linear energy transfer

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5
Q

High LET

A

Damage localized and severe (per unit of distance)

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6
Q

Low LET

A

Damage widespread and minimal (per unit of distance)

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7
Q

The higher the LET or energy deposited into tissue the greater…

A

Cellular damage will occur

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8
Q

As LET goes up, tissue damage…

A

Goes up

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9
Q

Whether LET is high or low depends upon:

A

Charge - neutral or ionic

Velocity - speed of light or slower

Mass - pure energy or matter

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10
Q

Charge of the particle will be

A

Attracted to opposites as they transverse matter.

A charged particle will do more damage than a neutral particle

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11
Q

A charged particle will do more damage than a

A

Neutral particle

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12
Q

Alpha particles cause the most damage because

A

It carries a +2 charge

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13
Q

X-rays and gamma rays cause the least damage due to

A

Being neutral (no charge)

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14
Q

Charged particles “pull” at tissue ironically as

A

They pass through

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15
Q

Velocity

A

The higher the velocity the more spread out the damage due to the large distance traveled in small time periods.

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16
Q

X-rays travel very fast so the damage caused is

A

Spread over a large area - small scale damage per unit of distance

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17
Q

Alpha particles travel relatively slowly causing damage to be

A

Limited to a small area - large scale damage per unit of distance

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18
Q

AMU

A

Atomic mass unit

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19
Q

Mass

A

The sum of an objects matter

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20
Q

Protons have a mass of

A

1 AMU

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21
Q

Electrons have an AMU of

A

5.486x10^-4 (.0005486 AMU)

Virtually no mass

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22
Q

X-rays have no mass making the

A

Highly penetrating

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23
Q

Alpha particles are

A

2 Protons and 2 neutrons

AMU = 4

Minimally penetrates matter - about 1mm

24
Q

Summation of high LET

A 
Particles are charged
Move at slow velocity
Have mass
Greater possibility of cell death
Low penetration of tissue
Greatest concern when inhaled or ingested
25
Q

High LET and DNA damage

A

Causes severe damage to DNA

  • double strand breaks
  • damage typically irreparable
26
Q

High LET damage to DNA is usually

A

Lethal to the cell

27
Q

Summation of low LET

A

No charge
Travel at speed of light
Have no mass
Highly penetrating

28
Q

Low LET and DNA damage

A

Typically causes sub lethal damage that can be repaired by the cell.

Point mutations or single strand breaks are more common.

29
Q

Low LET damage to DNA is usually

A

Repaired - the cell survives

30
Q

Cells that exist in a higher aerobic state have a

A

Higher radio sensitivity than cells that exist in an anoxic state (no or little oxygen available)

31
Q

As OER goes up, biologic damage…

A

Goes up

32
Q

OER is expressed as

A

The dose required to cause damage in anoxic/aerobic conditions

Damage can be 2-3 times greater in oxygenated state than the damage to the same tissue in an anoxic state.

33
Q

OER and LET

A

OER is enhanced with low LET radiation

34
Q

OER is minimal with

A

High LET radiation

35
Q

As LET goes up it will take less radiation to cause these e biological damage aaa

A

Low LET radiation. As LET goes up RBE goes up and vice versa

36
Q

RBE is not practical for measured dose received in human sand is most commonly used for

A

Experiments I specific tissue types in labs

37
Q

For radiation protection purposes we use the

A

Radiation Weighting Factor to calculate the equivalent dose and take into consideration different types of radiation

38
Q

As LET increases biological damage

A

Will increase - the chance of tissue repair will decrease

39
Q

As LET increases, RBE

A

Will also increase - damage due to mass and charge

40
Q

OER increases with

A

Low LET radiation (indirect action)

41
Q

Molecular effect of radiation

A 
Direct and indirect
Radio luzia of water
Effects upon DNA
Effects upon mitosis
Target theory
Cell death
42
Q

Direct action of irradiation - physical damage

A

Biological damage due to ionization of atoms on master molecules.

43
Q

Indirect action - chemical damage due to irradiation

A

Interraction of radiation with water molecules, production of ions and free radicals resulting in undesired chemical reactions - cell death due to indirect chemical reactions - toxic to cells
More likely with low LET radiation like X-ray.

44
Q

Radiolysis of water

A

X-ray ionizes matter by removing an electron which causes disruption of normal water molecule consumption.

45
Q

ionizing radiation and DNA

A

Single strand breakage aka point mutation.

Most common with low LET radiation.

46
Q

Single strand breakage is aka

A

Point mutation

47
Q

Double strand breakage ruptures both DNA side rails and is more common

A

With high LET radiation

48
Q

Mutation

A

Alternation of DNA base sequence.

May not be reversible and may be passed along to daughter cells.

49
Q

Ionizing radiation and effects upon chromosomes

A

Can cause breakage of chromosomes - both somatic and genetic cells.

50
Q

Genetic fragments

A

Broken chromosomes can “stick” together.

51
Q

Target theory

A

Master molecule within a cell, a unique or key molecule that cannot be replaced if damaged or destroyed. DNA is presumed to be the mater molecule.

52
Q

Rapid exposure to 100,000 rads (1,000 gray) will cause

A

Instant death in a period of a few minutes or less

53
Q

Reproduction death

A

Exposures of 100-1,000 rads.

Cells lose the ability to reproduce

54
Q

Apoptosis

A

Programmed cell death

Non-mitotic

Cells die without attempting cell division - occurs in interphase

55
Q

Mitotic death

A

Occurs when a cell dies after one or more divisions following exposure to ionizing radiation

56
Q

Ionizing radiation can affect cell division

A

May retard mitotic process or permanently inhibit mitotic process.

57
Q

Permanent inhibition leads to

A

Mitotic death

58
Q

Mitotic delay can occur

A

With exposures as small as 1 rad.

Exposure just before cell division begins, delay in beginning mitosis. After the delay, the cell continues on as normal.

SEM III - Radiation Biology (8 decks)

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