LET/RBE/OER & Direct/Indirect

Question 0

RBE

Answer 0

Relative biological effectiveness

Biologic reaction compared to a standard

Question 1

LET

Answer 1

Linear energy transfer

Energy deposited in tissue per unit of distance

Question 2

Standard RBE

Answer 2

250 KV X-rays

Question 3

OER

Answer 3

Oxygen enhancement ratio

Oxygen deprived versus oxygen rich environment

Question 4

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

Answer 4

LET - linear energy transfer

Question 5

High LET

Answer 5

Damage localized and severe (per unit of distance)

Question 6

Low LET

Answer 6

Damage widespread and minimal (per unit of distance)

Question 7

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

Answer 7

Cellular damage will occur

Question 8

As LET goes up, tissue damage…

Answer 8

Goes up

Question 9

Whether LET is high or low depends upon:

Answer 9

Charge - neutral or ionic

Velocity - speed of light or slower

Mass - pure energy or matter

Question 10

Charge of the particle will be

Answer 10

Attracted to opposites as they transverse matter.

A charged particle will do more damage than a neutral particle

Question 11

A charged particle will do more damage than a

Answer 11

Neutral particle

Question 12

Alpha particles cause the most damage because

Answer 12

It carries a +2 charge

Question 13

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

Answer 13

Being neutral (no charge)

Question 14

Charged particles “pull” at tissue ironically as

Answer 14

They pass through

Question 15

Velocity

Answer 15

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

Question 16

X-rays travel very fast so the damage caused is

Answer 16

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

Question 17

Alpha particles travel relatively slowly causing damage to be

Answer 17

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

Question 18

AMU

Answer 18

Atomic mass unit

Question 19

Mass

Answer 19

The sum of an objects matter

Question 20

Protons have a mass of

Answer 20

1 AMU

Question 21

Electrons have an AMU of

Answer 21

5.486x10^-4 (.0005486 AMU)

Virtually no mass

Question 22

X-rays have no mass making the

Answer 22

Highly penetrating

Question 23

Alpha particles are

Answer 23

2 Protons and 2 neutrons

AMU = 4

Minimally penetrates matter - about 1mm

Question 24

Summation of high LET

Answer 24

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

Question 25

High LET and DNA damage

Answer 25

Causes severe damage to DNA - double strand breaks - damage typically irreparable

Question 26

High LET damage to DNA is usually

Answer 26

Lethal to the cell

Question 27

Summation of low LET

Answer 27

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

Question 28

Low LET and DNA damage

Answer 28

Typically causes sub lethal damage that can be repaired by the cell. Point mutations or single strand breaks are more common.

Question 29

Low LET damage to DNA is usually

Answer 29

Repaired - the cell survives

Question 30

Cells that exist in a higher aerobic state have a

Answer 30

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

Question 31

As OER goes up, biologic damage...

Answer 31

Goes up

Question 32

OER is expressed as

Answer 32

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.

Question 33

OER and LET

Answer 33

OER is enhanced with low LET radiation

Question 34

OER is minimal with

Answer 34

High LET radiation

Question 35

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

Answer 35

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

Question 36

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

Answer 36

Experiments I specific tissue types in labs

Question 37

For radiation protection purposes we use the

Answer 37

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

Question 38

As LET increases biological damage

Answer 38

Will increase - the chance of tissue repair will decrease

Question 39

As LET increases, RBE

Answer 39

Will also increase - damage due to mass and charge

Question 40

OER increases with

Answer 40

Low LET radiation (indirect action)

Question 41

Molecular effect of radiation

Answer 41

``` Direct and indirect Radio luzia of water Effects upon DNA Effects upon mitosis Target theory Cell death ```

Question 42

Direct action of irradiation - physical damage

Answer 42

Biological damage due to ionization of atoms on master molecules.

Question 43

Indirect action - chemical damage due to irradiation

Answer 43

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.

Question 44

Radiolysis of water

Answer 44

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

Question 45

ionizing radiation and DNA

Answer 45

Single strand breakage aka point mutation. Most common with low LET radiation.

Question 46

Single strand breakage is aka

Answer 46

Point mutation

Question 47

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

Answer 47

With high LET radiation

Question 48

Mutation

Answer 48

Alternation of DNA base sequence. May not be reversible and may be passed along to daughter cells.

Question 49

Ionizing radiation and effects upon chromosomes

Answer 49

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

Question 50

Genetic fragments

Answer 50

Broken chromosomes can "stick" together.

Question 51

Target theory

Answer 51

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.

Question 52

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

Answer 52

Instant death in a period of a few minutes or less

Question 53

Reproduction death

Answer 53

Exposures of 100-1,000 rads. Cells lose the ability to reproduce

Question 54

Apoptosis

Answer 54

Programmed cell death Non-mitotic Cells die without attempting cell division - occurs in interphase

Question 55

Mitotic death

Answer 55

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

Question 56

Ionizing radiation can affect cell division

Answer 56

May retard mitotic process or permanently inhibit mitotic process.

Question 57

Permanent inhibition leads to

Answer 57

Mitotic death

Question 58

Mitotic delay can occur

Answer 58

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.