Radiobiology Mosby (Module 2 Biophysical Events and Cellular and Subcellular Effects of Radiation)

What happens when a free electron combines with another water molecule? a. The free electron and ionized water molecule form a stable, positively charged molecule. b. An unstable, negatively charged molecule results. c. The free electron and ionized water molecule form an unstable positively charged molecule. d. A stable, negatively charged molecule results.

An unstable, negatively charged molecule results.

is measured as the average energy deposited per unit length of track.(Kev/micro meter)

LET (Linear Energy Transfer)

The presence of vital structures within the cell is the basis of the ______________ __________. Theres a few key molecules, such as DNA, that if damaged would severely alter or kill the cell. A "direct hit" on one of these structures is purely random.

The Target theory

According to the Law of Bergione and Tribondeau, cell radiosensitivity is directly proportional to the degree of differentiation. a. True b. False

b. False

Diagnostic x-rays are considered to have an RBE of: a. 1 b. 2 c. 3 d. 4

1

are injuries to cells that occur when chemical bonds are broken. This is a cellular impairment or the loss of a function. When hydroxyl and hydrogen radicals destroy chemical bonds of molecules, there is significant potential for biologic damage. What is this?

Point Lesion

What is the process called when ionizing radiation transfers its energy to important macromolecules? a. Direct action b. Indirect action

a. Direct action note: When the energy is transferred directly to the macromolecule it is direct action, and when it is done secondarily, such as from radiolysis of water, it is indirect action.

If HOH+ and an electron combine, which of the following occurs? a. H20 b. OH* c. H* d. HOH-

a. H20 note: The best outcome following radiolysis of water is for the HOH+ to recombine with an electron to reform water (H2O) and no damage occurs.

OER is significant with: a. Low LET radiation b. High LET radiation c. Both are equal

a. Low LET radiation note: With high LET, the deposition of energy is generally by direct action, and the presence of oxygen makes no difference. However, with low LET radiation, the indirect actions create free radicals that combine with oxygen, making the damage permanent.

Which subcellular effect may involve the breaking of one side rail of DNA? a. Main-chain scission b. Rung breakage c. Loss of base d. separation of base

a. Main-chain scission

Indirect action usually involves what molecule first? a. Non-critical (water) b. Critical c. DNA d. RNA

a. Non-critical (water)

The presence of which of the following with low LET radiation will increase biologic damage? a. Oxygen b. Water c. Heat d. soft tissue

a. Oxygen

According to the Law of Bergonie and Tribondeau, cell radiosensitivity is directly proportional to reproductive activity. a. True b. False

a. True

Radiation can affect organic molecules in the same manner as inorganic molecules. a. True b. False

a. True

Which cellular effect would result from 1000 gray (100,000 rad) over a very short period? a. Instant death b. reproductive death c. Apoptosis d. Mitotic death

a. instant death

Which of the following would be most radiosensitive? a. Cells that reproduce slowly b. Cells that reproduce rapidly

b. Cells that reproduce rapidly

During irradiation, which of the following is more biologically dangerous? a. Sparse ionization b. Dense ionization c. both are equal

b. Dense ionization

Most biologic damage from ionizing radiation is a result of which of the following? a. Direct action b. Indirect action

b. Indirect action note: Because the human body is 80% water and less than 1% DNA, most of the biologic damage from ionizing radiation is presumed to be through the indirect effect.

The most serious change to a cell occurs when there is damage to which of the following? a. Membrane b. Nucleus c. Cellular fluid

b. Nucleus

Radiation interacting with DNA would be a: a. Cellular effect b. Subcellular effect

b. Subcellular effect

The interaction between ionizing radiation and a vital cell structure is the basis for which of the following? a.Law of Bergonie and Tribondeau b.Target theory c.Compton effect d.Image forming radiation

b. Target theory

Which of the following is used as the standard for RBE? a. Gamma b. X-rays c. Alpha d. Beta

b. X-rays

Radiation absorbed inside the patient is known as which of the following? a. Patient internal dose b. Soft tissue dose c. Absorbed dose d. Low-energy patient dose

c. Absorbed dose

Which of the following describes cell death prior before it attempts division? a. Instant death b. Reproductive death c. Apoptosis d. Mitotic death

c. Apoptosis

What first happens when an x-ray interacts with and ionizes a molecule of water? a. Metabolism b. Anabolism c. Ion pair is created d. All of the above

c. Ion pair is created

Which subcellular effect would result in no damage? a. Deletion b. Broken-end rearrangement c. Restitution d. None of the above

c. Restitution

How do hydrogen and hydroxyl radicals cause biologic damage? a. They destroy chemical bonds b. Hydroxyl radicals can bond to form hydrogen peroxide c. A hydrogen radical can interact with molecular oxygen to form a hydroperoxyl radical d. All of the above

d. All of the above

What increases the probability of biologic damage? a. Increased ionization per micron of soft-tissue b. Increased LET c. Reduced speed of particles d. All of the above

d. All of the above

Most biologic damage resulting from diagnostic x-rays occurs from which of the following? a. Interaction of positive and negative ions b. Recombination of free radicals and positive water ions c. Hydrogen and hydroxyl ions d. Hydrogen peroxide and hydroperoxyl radicals

d. Hydrogen peroxide and hydroperoxyl radicals

When comparing a dose of radiation delivered over a short period of time to a dose of the same amount delivered over a greater period of time, which of the following is true of the biologic effect of the dose delivered over a short period of time? a. It would be equal. b. It would be less. c. It would be greater. d. More information is needed.

d. It would be greater.

Which of the following is the term used to describe the average energy deposited along the path of radiation? a. Radiolysis of water b. Compton scattering c. RBE d. LET

d. LET

Which of the following occurs after cell division? a. Instant death b. Reproductive death c. Apoptosis d. Mitotic death

d. Mitotic death note: Mitotic death occurs after the cell has divided one or more times.

What are the three levels of biologic effects of radiation on humans? a. Genetic, molecular, cellular b. Organic, cellular, genetic c. Molecular, genetic, organic d. Molecular, cellular, organic

d. Molecular, cellular, organic

Which of the following units is used to compare the different types of radiation with their biologic effects at different doses? a. Seivert b. LET c. Gray d. RBE

d. RBE note:Relative biological effectiveness (RBE) is a ratio that compares a standard (usually x-rays) with another radiation.

LET is the term used to describe the average energy deposited per: a. Gray b. Dose c. Ionization d. Unit length of track (micron)

d. Unit length of track (micron)

When does radiolysis of water occur? a. When water interacts with a macromolecule b. When free radicals form toxic substances c. When there is an interaction of radiation and human tissue d. When water is ionized

d. When water is ionized

When ionizing radiation interacts with vital cell structures, like DNA, the interaction is classified as _________ action

direct note: rare effect

Most biologic damage that results from ionizing radiation occurs because of the ___________ that are ejected in the process of ionization

electrons

A dose delivered in equal fractions over time is called a ________________ dose.

fractionated note: Radiation treatments for cancer, for example, use fractionated doses to minimize damage to healthy body tissues.

The __________ action is the result of the interaction with a non-critical molecule first (usually water), creating free radicals that then transfer the energy to the target molecule. Because the human body is approximately 80% water and less than 1% DNA, it is presumed that most biologic damage from ionizing radiation is through this effect.

indirect "action or (effect)" note: most common

Biologic damage resulting from ionizing radiation occurs on three levels: _______________, ___________, and ____________.

molecular, cellular, and organic.

A dose delivered continuously over a period of time is called a _____________ dose.

protracted

The interaction between water and ionizing radiation is called the ______________ of water

radiolysis note: this is the indirect effect