Week 6 - Molecular & Cell Biology

Question 1

What is radiation biology?

Answer 1

A branch of science concerned with effects of ionizing radiation on living systems

Question 2

What does radiation biology include?

Answer 2

• Sequence of events occurring after the absorption of energy from ionizing radiation
• Action of living systems to make up for the consequences of this energy assimilation
• Injury to the living system that may be produced

Question 3

What are the information sources for Radiation biology?

Answer 3

• Animal and plant experiments
• Observation of humans who have been exposed to radiation under known circumstances

Question 4

What are the effects of ionizing radiation?

Answer 4

Damages living systems by ionizing atoms comprising the molecular structure of these systems

Question 5

What does biologic damage begin with?

Answer 5

The ionization produced by various types of radiation such as x-rays, gamma rays, alpha particles, beta particles and protons

Question 6

What are 3 important concepts to help us understand the way ionizing radiation causes injury?

Answer 6

• Linear energy transfer (LET)
• Relative biologic effectiveness (RBE)
• Oxygen enhancement ratio (OER)

Question 7

What is LET?

Answer 7

The average energy deposited per unit length of track by ionizing radiation as it passes through and interacts with a medium along its path

Question 8

What is LET measured in?

Answer 8

keV/um

Question 9

What is high LET?

Answer 9

More damaging and less penetrating

Question 10

What are examples of High LET?

Answer 10

Alpha particles

Question 11

What is low LET?

Answer 11

Less damaging but more penetrating

Question 12

What are examples of low LET?

Answer 12

X-ray and gamma rays

Question 13

What is RBE?

Answer 13

The relative capability of radiation with differing LETs to produce a particular reaction

Question 14

What is the formula to calculate RBE?

Answer 14

RBE = Dose in Gyt from 250-kvp rays/Dose in Gyt of test radiation

Question 15

What is the RBE of xray and gamma rays?

Answer 15

Approximately 1

Question 16

What is the RBE for alpha radiation?

Answer 16

Approximately 3

Question 17

What also affects RBE?

Answer 17

The manner in which the dose is delivered

Question 18

What is the general rule for radiation delivered over a long period of time?

Answer 18

Radiation delivered over a long period of time will be less effective

Question 19

What is the reason radiation delivered over long periods of time are less effective?

Answer 19

Some cell will recover from the damage as time passes

Question 20

What are the two ways in which ionizing radiation can be stretched?

Answer 20

• Fractionation
• Protraction

Question 21

What is Fractionation?

Answer 21

Radiation therapy where a total dose is divided into multiple sessions

Question 22

What is protraction?

Answer 22

A continuous dose delivered at a low rate

Question 23

What is OER?

Answer 23

The ratio of the radiation dose required to cause a particular biologic response of cell in an oxygen deprived environment to the radiation dose required to cause an identical response under normal oxygenated conditions

Question 24

What is the OER of x-rays and gamma rays?

Answer 24

3.0 when radiation dose is high

Question 25

When could OER be less?

Answer 25

When radiation dose is below 2 Gyt

Question 26

What is the OER formula?

Answer 26

OER = Radiation dose without O2/Radiation dose with O2

Question 27

At what 3 levels can biologic damage resulting from exposure be observed in?

Answer 27

• molecular
• cellular
• organic

Question 28

Where do any visible radiation-induced injuries of living systems always begin?

Answer 28

At the molecular level

Question 29

What does molecular damage result in?

Answer 29

The formation of structurally changed molecules that may impair cellular function