Biological Response To Ionizing Radiation

Question 1

Physical factors that affect radiosensitivity of cells

Answer 1

1. Linear energy transfer
2. Relative biological effectiveness
3. Protraction and fractionation

Question 2

Linear energy transfer LET

Answer 2

The measure of the rate at which energy is transferred from ionizing radiation to soft tissue

Question 3

LET and biological response

Answer 3

If the LET increases so does the biological response, high let equals high biological damage

Question 4

Relative biological effectiveness

Answer 4

Ratio of doses required by 2 radiations to cause the same level of effect.

Question 5

Relative biological effectiveness

Answer 5

Ratio of doses required by 2 radiations to cause the same level of effect.

Question 6

Absorbed dose and biological effectiveness

Answer 6

Different types of radiation can have the same absorbed dose, but different impact on the body due to tissue weighting factor

Question 7

Protraction

Answer 7

Radiation dose delivered continuously but at lower dose rate.

Question 8

Fractionation

Answer 8

Radiation delivered at the same dose in equal potions at regular intervals

Question 9

Importance of fractionation

Answer 9

This allows healthy tissues to repair themselves between treatments, minimizing side effects.

Question 10

Importance of protraction

Answer 10

Gives cells enough time to repair themselves from the radiation exposure.

Used in killing cancerous tumors.

Question 11

Biological factors that affect radiosensitivity of cells

Answer 11

1. Oxygen Enhancement Ratio[OER]
2. Age
3. Hormesis
4. Recovery

Question 12

Oxygen enhancement ratio

Answer 12

Is the ratio of radiation dose required to cause a particular biological response in an oxygenated environment to the radiation dose required to cause the same effect in an unoxygenated environment.

Question 13

OER and biological response

Answer 13

Areas where there are oxygen are more radiosensitive that unoxic areas, this is because free radicals are created in the presence of oxygen , and they increase the amount of tissue damage.

Question 14

Hormesis

Answer 14

It encompasses the fact that, small doses of radiation can be beneficial to the body.

Small doses of radiation stimulates hormonal and immune responses to toxic environments

Question 15

Age

Answer 15

Infants are radiosensitive since their cells are still undergoing cell division, adults are less radiosensitive and old people are more radiosensitive.

Question 16

Recovery

Answer 16

Normal cells undergo recovery after radiation, the radiation have to be of insufficient energy so that the cell should be able to recover.

Question 17

Importance of OER

Answer 17

Helps to reduce the dose on patients when x-raying oxygenated areas like tumors

Question 18

Types of cell damage

Answer 18

1. Direct cell damage
2. Indirect cell damage

Question 19

Direct cell damage

Answer 19

Occurs when the radiation energy directly interacts with cell’s tissues thereby damaging it.

Question 20

Indirect cell damage

Answer 20

Occurs when radiation energy interacts with the fluid inside the cell and produce free radicals, these free radicals interacts with the cell organelles and compromises the cell function.

Question 21

Target theory

Answer 21

• Cells have critical targets (e.g., DNA).
• Radiation hits these targets, causing damage.
• More hits equals higher chance of cell death.