B - Radiobiology

Question 1

What is Radiobiology?

Answer 1

Branch of science concerned with the action of ionizing radiation on biological tissues and living organisms
Combination of BIOLOGY and RADIATION PHYSICS

Question 2

What are the 2 different radiation measurements?

Answer 2

Gray (Gy) and Sievert (Sv)

Question 3

What is a Gray?

Answer 3

SI unit (systeme internationale)
standard unit of absorbed ionising-radiation dose
equivalent to one joule per kilogram

Question 4

What is Sievert (Sv)?

Answer 4

SI unit, measure of total biologically effective dose
Calculated by multiplying the number of Grays of radiation by a quality factor or Q factor specified for the type of radiation and its energy, after which these amounts are added together
The factor for x- and gamma rays is 1; therefore, 1 Sv = 1 Gy. The factor for the neutrons in atomic-bomb radiation is 10; therefore, 1 Sv = 0.1 Gy

Question 5

What are the 4 phases of Mitosis?

Answer 5

Mitosis phase (M), Gap1phase (G1), Synthesis phase (S), and Gap2phase (G2)

Question 6

What is the time it takes for a cell to complete a cycle?

Answer 6

This depends on the cell type:
Blood, bone marrow, skin and cell lining the stomach and intestine divide rapidly and constantly
Kidney, liver and lung cells divide when needed to replace damaged or dead cells
Nerve cells stop dividing when mature

Question 7

What is cell death?

Answer 7

Loss of a specific function or reproductive integrity

Question 8

Is the cell cycle time in malignant cells, shorter or longer than normal cells?

Answer 8

Cell cycle time of malignant cells is shorter than that of normal cells, however regeneration of cells after injury of normal cells is quicker

Question 9

What is Irradiation of Cells?

Answer 9

Physical Effects THEN Biological Damage

Biological effects result from damage of DNA

Absorption of ionizing radiation can cause DIRECT and INDIRECT damage

Question 10

What is direct radiation induced cell damage?

Answer 10

Radiation interacts directly with critical target in the cell

Atoms within the cell can be ionized or excited, causing a chain of physical and chemical events

Dominant interaction of high LET particles

Question 11

What is indirect radiation induced cell damage?

Answer 11

Radiation interacts with other molecules within cell (i.e. water)

Produces free radicals, which can damage the critical target in the cell

Accounts for approximately 2/3 damage by low LET radiations, such as medical x-rays

Question 12

There are 9 possible outcomes for an irradiated cell. What are they?

Answer 12

No effect
Division delay
Apoptosis
Reproductive failure
Genomic instability
Mutation
Transformation
Bystander effects
Adaptive responses

Question 13

What is the timescale of radiation damage?

Answer 13

Timescale between breakage of chemical bonds and biological damage may be hours or even years, depending on the type of damage

Question 14

The type of damage caused by radiation can be split into three classifications. What are they?

Answer 14

Lethal Damage
Sub-Lethal Damage
Potentially Lethal Damage

Question 15

Describe characteristics of lethal damage, sub lethal damage and potentially lethal damage?

Answer 15

Lethal Damage
Irreversible
Irreparable
Leads to cell death
Sub lethal Damage
Repaired in Hours
If re-exposed to sub lethal damage again can lead to lethal damage
Potentially Lethal Damage
Can be manipulated by repair when cells are allowed to remain in non-dividing state

Question 16

Effects of radiation on human population are either somatic or genetic. What are they?

Answer 16

SOMATIC: These are effects that an individual will experience in their lifetime, for example; sterility, carcinogenesis, opacification of eye lens
GENETIC: These are radiation induced mutations of an individuals gene’s and DNA that can contribute to birth defects in descendants

Question 17

The harmful effects of radiations can further be classified as Stochastic or Deterministic. What are they?

Answer 17

STOCHASTIC: An effect in which the probability of occurrence increases with increasing dose but the severity in affected individuals does not depend on the dose
DETERMINISTIC: An effect in which i.e. a tissue reaction, that increases with increasing dose, usually above a threshold dose in an individual

Question 18

What is the difference between acute and chronic reactions?

Answer 18

Acute
Manifests soon after exposure
Characterized by inflammation, oedema, denudation of epithelia and haemorrhage

Chronic
Delayed response after exposure
Can be generic reactions and caused by absorption of radiation directly by target tissue or a consequence of acute damage
Can include fibrosis, atrophy, ulceration, stenosis or obstruction of the intestine

Question 19

List tissue and organs of the body in order of most sensitive to leave radiosensitive?

Answer 19

Blood forming organs
Digestive system
Reproductive system
Skin
Bone
Muscle
Nervous system

Question 20

What is a total body response?

Answer 20

Total Body Response is a combination of the response of ALL body systems

Depending on the total dose to the body, the response is described as a specific radiation syndrome:

1Gy < dose < 10Gy: Bone Marrow Syndrome
10Gy < dose < 100Gy: Gastrointestinal Syndrome
Dose > 100Gy: Central Nervous System Syndrome

This is also a technique used in radiotherapy as preparation for haematopoietic stem cell/bone marrow transplantation

Question 21

Data regarding human radiation exposure and reaction has been collected from numerous sources, including?

Answer 21

Accidents in industry and research labs
Exposure to radioactive fallout from testing of nuclear weapons
Chernobyl power plant accident
Hiroshima, Fukushima and Nagasaki
Medical exposure of patients for Total Body Irradiations (TBI)

Question 22

Tell me about foetal irradiation?

Answer 22

There are 3 stages of development between conception and birth:
Pre-implantation (day 1-10)
Organogenesis (day 11-42)
Growth stage (day 43 – birth)
Radiation is referred to as a teratogen i.e. It can cause birth defects
The likelihood of these defects occurring depends on two factors: dose and the stage at which the exposure occurs
Principal effects are foetal or neonatal death, growth retardation, congenital defects and cancer

Question 23

What are RADIOPROTECTORS?

Answer 23

Agents that reduce cell response to radiation.

Question 24

What are RADIOSENSITIZERS?

Answer 24

Agents that enhance cell response to radiation