RT206: M3 - RADIATION TRANSFER ENERGY

free radical

A _______ is an uncharged molecule that contains a single unpaired electron in its valence shell, which makes it chemically unstable and highly reactive.

Radiolysis of water

_________ is the breaking down of water molecules with the use of radiation.

Direct Inter

Occurs when any type of radiation deposits its energy directly in the critical target resulting in ionization of this target.

Direct Interaction

This directly affects DNA. After that interaction, it results in ionization of DNA. If a target becomes ionized, it is considered as abnormal. Thus, DNA is now damaged.

radiolysis of water

_________ is the primary effect from radiation exposure to the cell.

Puck and Marcus (1956)

Studies of cellular sensitivity first became possible when ___________ first used HeLa cells for in vitro studies.

Target Theory

It states that there are areas on the DNA chain, that if damaged, are lethal to the cell.

cellular death

On HeLa cells they are exposed to various doses of radiation and then they count the number of surviving HeLa cells. Due to that, they began to theorize that when radiation directly interacts with the DNA, there are certain areas on the DNA chain that if damaged by the radiation, it is considered to be lethal to the overall cell, thus resulting in _______ .

Single target/single hit theory

________ means that you only need one target, like in this case, your DNA. And it only needs to be hit once in order to occur damage.

SINGLE TARGET/MULTIPLE HIT THEORY

Single target, meaning it needs only one target, or in this case your DNA it needs to be hit multiple times, or you need multiple DNA, but it needs to only be hit once.

MULTIPLE TARGET/MULTIPLE HIT THEORY

The third theory is that you need multiple targets, and it needs to be hit multiple times in order to cause damage to the cell.

MULTIPLE TARGET/MULTIPLE HIT THEORY

Least likely to be fatally damaged by radiation.

radiolysis of water

If water is irradiated, the water is ionized, and separates into other molecular products. This is called the ________.

free radical

When radiation indirectly interacts with the cell, the radiation interacts with the water molecules resulting in a ________.

free radicals

It is believed that ________ to be a major factor in cellular damage.

• Physical Stage

• Physical Chemical Stage

• Chemical Stage

In the radiolysis of water, there are about three stages:

Physical Stage

It occurs within one femtosecond. And in this stage, there is a deposition of energy to the water molecules followed by a fast relaxation process.

H2O Radical

If the water molecules are excited, so they product _________.

H2O positive plus an electron

But if the water molecules are ionized, so they produce __________.

physicochemical stage

During the __________, numerous processes occur including ion molecule reaction.

Linear Energy Transfer

The rate at which energy is deposited per unit length as a charged particle travels through matter, like the soft tissues, by a specific particular type of radiation.

High Let

_______ includes radiation types that has high mass and high charge and is likely to interact directly with biologic tissue

Low LET

_______ on the other hand is likely to interact indirectly because they do not have enough energy to interact critical targets.

high LET

Alpha particles and neutrons have ______.

low LET

Beta particles, X-rays, and gamma rays have _______

Relative Biological Effectiveness

_______ is the comparison of similar doses of one type of radiation to another. This means that the same doses of two different types of radiation do not yield the same biologic effect.

Oxygen enhancement ratio or OER

______________ is the ratio of the dose of a given radiation needed to cause a given biologic effect in deoxygenated conditions to the dose of the same radiation needed to cause the same biologic effect under oxygenated conditions.

oxygenated conditions

The response of the biologic tissue to radiation is greater when irradiated in ________.

oxygen effect

If the body is oxygenated, therefore the body is more sensitive to radiation than when it is deoxygenated. This is known as your ________.

low LET radiation

This means that for ________, the biologic effect received will be higher when cells are oxygenated.