Radiation Biology Review

A collection of questions and answers covering key concepts from the lecture on radiation biology.

What is the basic functional unit of all plants and animals?

The cell.

What percentage of water is the human body made up of?

80%.

What is the most radiosensitive target molecule in the human cell?

DNA.

Does meiosis deal with somatic or genetic cells?

Genetic cells.

What is it called when a cell is NOT undergoing mitosis or meiosis?

Interphase.

In which phase will any chromosome damage induced by radiation be seen?

Metaphase.

What increases the probability of a hit from radiation?

High O2 & high LET (Linear Energy Transfer).

In which phase of the cell cycle are human cells the MOST radiosensitive?

Mitosis.

Which type of radioactive particle has the highest LET?

Alpha particles.

How does the mean lethal dose for high-LET compare to low-LET radiation?

High LET is lower or the same.

What effect does oxygen being present during low-LET radiation have?

The effect of radiation is maximal.

What effect does oxygen have on HIGH-LET radiation?

Radiation effect remains the same.

What are the two types of irradiation hits?

Direct and indirect.

What happens in a main-chain scission?

One big macromolecule breaks into smaller molecules.

What type of DNA damage may not be reversible?

Base change/loss.

What can radiation damage to DNA cause?

Cell death, malignant disease, and genetic changes.

What is the principal radiation interaction within the human body?

H2O.

What is radiolysis?

The dissociation of a water molecule following irradiation.

What does an atom of water FIRST disassociate into after being irradiated?

An ion pair.

What can two OH* free radicals join to form?

Hydrogen peroxide.

Why can free radicals be damaging?

They are unstable and highly reactive.

What molecule does an indirect effect from ionizing radiation occur on?

Water.

What is LET?

Linear Energy Transfer.

As LET increases, what happens to RBE?

It also increases.

What is the LET of diagnostic x-rays?

3.0.

What is the RBE of diagnostic x-rays?

1.0.

What effects does the presence of high oxygen have on tissue?

Tissue is more radiosensitive.

Which human is most radiosensitive?

The embryo fetus during the first trimester.

The human application of radioprotective agents would be what?

Fatally toxic.

When can human cells NOT recover from radiation damage?

After an interphase death.

What is hormesis?

When small amounts of radiation are beneficial to the body.

What types of radiation are considered low-LET radiations?

X-rays and gamma rays.

What does a loss or change of a base in the DNA chain represent?

Mutation in the genetic code.

When is direct action of damage more likely to occur?

When it is high LET particles.

What are the rungs of the DNA ladder-like structure made of?

Pairs of nitrogenous bases.

What compounds are called purines?

Adenine and guanine.

What are the cell components that contain the centrioles?

Centrosomes.

Who was the first American radiation worker to die from radiation-induced cancer in 1904?

Clarence Madison Dally.

What does 0.2Gy equal?

200mGy.

What is the definition of air kerma?

The total kinetic energy released in a unit mass of air.

What is Dose Area Product?

The sum total of the air kerma over the exposed area of the patient's body surface.

What do radiation weighting factors take into consideration?

Some types of radiation are more efficient at causing biological damage.

What does 1Gy equal in the SI system?

An energy absorption of 1J/kg of matter.

Which types of ionizing radiation produce virtually the same biologic effect in body tissue for equal absorbed doses?

X-rays, gamma rays, beta particles.

What is the definition of exposure?

The measure of total electrical charge per unit of mass.

What is the formula for effective dose?

Efd = D x Wr x Wt.

What is the numerical value for the radiation weighting factor of alpha particles?

20.

What units are NOT SI units?

Roentgens, rads, rems.

What are beta particles?

High-speed electrons.

What are the regularly used SI units to describe dose in therapeutic radiology?

Gray/centigray.

Who discovered X-rays and on what day?

Wilhelm Conrad Roentgen on Nov 8, 1895.

What are X-ray photons?

Particles associated with electromagnetic radiation.

What is NOT a type of interaction between x-radiation and biologic matter?

Bremsstrahlung.

What does the “Z” symbol indicate?

Atom’s atomic number.

What does pair production involve?

X-ray photons with a matter-antimatter annihilation reaction.

What are enhanced natural sources?

Ionizing radiation from natural sources due to human actions.

What are the two forms of cosmic radiation?

Solar and galactic.

How can radon enter houses?

Crawl spaces, floor drains, and porous cement block foundations.

What is the most common unit of measure of equivalent dose?

mSv (milliSievert).

What are examples of human-made radiation sources?

Atmospheric fallout and nuclear power plant accidents.

In photoelectric absorption, what must the incoming x-ray photon have?

Energy as large or larger than what holds the electron.

What was the immediate cause of damage if free radicals strike DNA?

The free radicals produced from radiation with a water molecule.

What is the RBE of the test radiation if 4Gyt produced a biologic reaction requiring 16 Gyt of x-rays?

4.