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X-rays are what form of ionizing radiation?


Which type of radiation originates from a radioactive nucleus?


CT scanning is now a major source of medical radiation exposure. T/F


Which interaction involves photons generally below 10keV?
A. Classical
B. Photoelectric
C. Compton
D. Photodisintegration


Interactions between higher energy photons and outer shell electrons of tissue atoms result in:
A. Classical
B. Compton
C. Photoelectric
D. Photodisintegration


Most of the scatter produced during radiography procedures results from which interactions?
A. Pair production
B. Compton
C. Photoelectric
D. Classical


Photoelectric absorption increases as the effective atomic number of matter increases. Which of the following has the highest atomic number?
A. Water
B. Bone
C. Soft tissue
D. Air


What is the ejected electron called in a photoelectric event?
A. Photodisintegration
B. Positron
C. Negatron
D. Photoelectron

Pair production

What interaction produces a positron and an electron?
A. Compton
B. Photoelectric
C. Photodisintegration
D. Pair production


Photodisintegration involves an interaction with the nucleus of a tissue atom. T/F

Molecular, cellular, organic

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

All of the above

In what part of the body can radiation absorption take place?
A. Skin
B. Bone
C. Organs
D. All of the above

Ion pair is created

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.


If HOH+ and an electron combine, which of the following occurs?
A. H20
B. OH*
C. H*

When water is ionized

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

Dense ionization

During irradiation, which of the following is more biologically dangerous?
A. Sparse ionization
B. Dense ionization
C. Both are equal


Which of the following is used as the standard for RBE?
A. Gamma
B. X-rays
C. Alpha
D. Beta


The presence of which of the following with low LET radiation will increase biologic damage?
A. Oxygen
B. Water
C. Heat
D. Soft tissue

Main-chain scission

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

Instant death

Which cellular effect would result from 1000 gray over a very short period?
A. Instant death
B. Reproductive death
C. Apoptosis
D. Mitotic Death


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


During a typical exam the radiographer is most likely to be exposed to which of the following?

A. Classical
B. Compton
C. Pair Production


Which interaction results in excitation of the tissue atom but not ionization?

A. Compton
B. Photoelectric
C. Classical
D. Pair Production


Prior to 1990, medical sources of radiation contributed less than half of the total exposure to radiation in the United States. T/F


Photodisintegration is a common interaction in diagnostic radiography. T/F

pair production

1.02 MeV is required for which interaction?

A. Compton
B. Photoelectric
C. Pair Production
D. Photodisintegration


Which type of ionizing radiation is from the same family as microwaves?

A. Electromagnetic
B. Particulate


Which of the following involves an inner shell interaction and total absorption of the photon?

A. Classical
B. Compton
C. Photoelectric
D. Photodisintegration

Indirect Action

Most biologic damage from ionizing radiation is a result of which of the following?

A. Direct Action
B. Indirect Action

Direct Action

What is the process called when ionizing radiation transfers its energy to important macromolecules?

A. Direct Action
B. Indirect Action


The most serious change to a cell occurs when there is damage to which of the following?

A. Membrane
B. Nucleus
C.Cellular fluid

All of the Above

How do hydrogen and hydroxl radicals cause biologic damage?

A. They destroy chemical bonds
B. Hydroxl radicals can bond to form hydrogen peroxide
C. A hydrogen radical can interact with molecular oxygen forming hydroperoxyl radical
D. All of the above


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

Subcellular effect

Radiation interacting with DNA would be a

A. Cellular effect
B. Subcellular effect


Which of the following units is used to compare the different types of radiation with their biologic effects at different doses?

A. Seivert
C. Gray

Unit length of track (micron)

LET is the term used to describe the average energy deposited per

A. Gray
B. Dose
C. Ionization
D. Unit length of track (micron)

Mitotic death

Which of the following occurs after cell division?

A. Instant death
B. Reproductive death
C. Apoptosis
D. Mitotic death


According to the Law of Bergonie and Tribondeau, cell radiosensitivity is directly proportional to reproductive activity. T/F


Radiation can affect organic molecules in the same manner as inorganic molecules. T/F

Low LET radiation

OER is significant with

A. Low LET radiation
B. High LET radiation
C. Both are equal

Classical scattering

A process that is most likely to occur with low-energy x-rays (below 10 keV). When a photon from such an x-ray enters an atom, it does not have enough energy to knock out an electron and cause Compton scattering. Instead, the photon's energy causes a momentary state of excitation in the atom—a higher state of energy—which results in a secondary x-ray photon exiting the atom in a different direction but with the same energy. This process is also called Thompson, coherent, or unmodified, scattering.


The likelihood that certain types of interactions will occur in certain situations.


The process in which x-ray photons diverge from their original path in the x-ray beam and strike the film in random locations, producing an overall characteristic called film fog. It results from Compton and classical scattering.


A process that is most likely to occur with x-rays in the energy range of 30 to 50 keV. The photon of the x-ray knocks an electron out of the atom that it strikes, but not all of its energy is absorbed by the interaction. The x-ray photon exits the atom with lower energy in a different direction.

Characteristic photons

The result that occurs when an electron in an inner shell is knocked from its orbit by a projectile electron and another electron jumps down to fill its place, releasing an x-ray photon in this interaction equal in energy to the differences in electron binding energies.


The process that occurs when an incident x-ray photon is absorbed by the atom it strikes, and an electron is ejected from the inner shell of that atom.

Binding energy

The energy that holds protons and neutrons together in the nucleus through the force of attraction; the amount of energy needed to break up the nucleus.


The electron that is ejected during the process of photoelectric interaction.

Pair production

A process that occurs only with very high-energy x-ray photons. A photon with at least 1022 keV (or 1.02 MeV) of energy may penetrate the electron shells of the atom and reach the nucleus, where its energy is converted into the production of an electron and a positron.


A positively charged electron.

Annihilation event

A process that occurs after pair production. The positron that is created in pair production travels until it strikes an electron with which it interacts. The positron's and electron's mass disappears and is converted into two x-ray photons that radiate out of the atom.


The process that occurs when x-rays with extremely high energy (above 10 MeV) strike the nucleus of the atom and make it unstable. To become stable again, this nucleus ejects a nuclear particle, such as a proton, neutron, or alpha particle.


The smallest unit of a compound or element that can exist by itself and has the chemical properties of the compound or element.

Direct action

Process by which ionized particles directly transfer energy to important macromolecules, resulting in the breaking of chemical bonds, which may cause biologic damage.

Indirect action

Process by which ionized particles interact initially with noncritical molecules, which are then broken down into smaller molecules, producing both ions and free radicals that can recombine to form toxic substances, which can produce biologic damage.

Target theory

The scientific theory that each cell contains a key, or master, molecule and that cell death occurs only if the master molecule is destroyed as a result of exposure to ionizing radiation.

Free radical

An atom or molecule with a single electron in its outer shell.

Point lesion

Damage resulting when the chemical bonds of molecules are disrupted; also known as molecular lesion.

Hydrogen peroxide

H2O2, a toxic substance that is poisonous to human cells.

Hydroperoxyl radical

A combination that can occur during radiolysis of water. Hydrogen free radicals interact with molecular oxygen, creating a hydroperoxyl radical. Hydrogen peroxide and the hydroperoxyl radical are considered the primary causes of biologic damage resulting from radiolysis of water.

Radiolysis of water

The interaction of x-radiation with water.

Organic molecules

Life-supporting molecules; organic molecules that contain some carbon.

Protracted dose

A dose delivered continuously at a low-dose rate.

Fractionated dose

A radiation dose delivered over time in equal fractions.

Main-chain scission

The condition resulting from breakage of the thread or backbone of a long-chain molecule.

Cytoplasmic organelles

Small components of cells contained in the cytoplasm that perform many functions of the cell.


A nonmitotic or nondivision form of cell death that occurs when cells die without attempting division during the interphase portion of the cell life cycle; also called programmed cell death or interphase cell death.

Mitotic death

Damage to a cell's ability to reproduce, which occurs after a cell has divided at least once; also called genetic death.

Mitotic delay

A temporary delay in mitosis caused by radiation exposure.

radiation biology

branch of biology concerned with the effects of ionizing radiation on living systems

areas of study

includes: sequence of events, action of the living system, and injury to the living system

structure, composition, and function

Because we administer radiation ot humans for medical purposes, it is necessary that we have a basic understanding of cell ___, ___, and ___ as well as the adverse effects.


Ionizing radiation damages living systems by removing ___.

x-rays, gamma rays, alpha and beta particles, and protons

What is able to interact with orbital electrons?


Biologic damge begins with the ___ produced by various types of radiation.


What are the 3 important concepts that must be studied to understand the way ionizing radiation causes injury and how the effects my vary? (abbreviations)

Linear Energy Transfer (LET)

This states that ionizing radiation may interact with a material as it passes through and deposit energy.

Linear Energy Transfer (LET)

The average energy deposited per unit of length of path traveled.


X-rays and Gamma rays are forms of low/high LET radiation?

Low LET radiation

This is electromagnetic radiation that is sparsely ionizing, interacts randomly, doesn't give up all of it's energy quickly, and causes damage through indirect actions


Low LET radiation causes damage primarily through the formation of free radicals which is what type of action?

repair enzymes

What can usually reverse cellular damage caused by low LET?


Alpha particles are a form of low/high LET radiation?

High LET radiation

What includes particals that have substantial mass and charge that cause dense ionization and loses energy quickly?


Which form of LET is more destructive to biologic tissue?


The probability of an electron interacting with DNA rather than an alpha particle is ___


These particles have a low probability of interacting with DNA because they do not interact as often and they travel farther.

alpha particles

These particles have a high probability of interacting with DNA because they interact often and they do not travel far.


Biologic damage produced by radiation ___ as the LET of radiation increases.

Relative Biologic Effectiveness (RBE)

This describes the relative capabilities of radiation with differing LETs to produce a certain biologic reaction

Relative Biologic Effectiveness (RBE)

The ratio of the dose of reference radiation to the dose that is necessary to produce the same biologic reaction.


Dose in Gy from 250 kVp x-rays/ dose in Gy of test radiation (abbrev.)


As LET increases, RBE ____


Low-LET have __ RBE


High-LET have ___ RBE


Diagnostic x-rays have a RBE of __?

cells and tissues differ in biologic response

Why is RBE not practical for specifying radiation protection dose levels in humans?

Radiation Weighting Factor (Wr)

What is similar to RBE and used to calculate equivalent dose

Oxygen Enhancement Ratio (OER)

This describes the response of biologic tissue to radiation is greater when irradiated in an oxygenated state than when irradiated in an oxygen deprived state

Oxygen Enhancement Ratio (OER)

Dose required without O2/ Dose required with O2


OER is most pronounced in ___ radiation


The presence or absence of oxygen does not matter with what type of radiation?

free radical

a solitary atom or most often a combination of atoms that behaves as an extremely reactive single entity as a result of the unpaired electrons


Free radicals dramatically ___ the amount of biologic damage


The presence/absence of oxygen in tissue makes bioligic damage produced by free raddicals permaninet

organic peroxide compounds

The presence of O2 makes damage permanent by producing ____, which makes nonrestrable changes in the chemical composition

molecular, cellular, and organic

Bioligic damage from ionizing radiation can be observed on which 3 levels?

cell function

The structures of a cell's constituent molecules determines ___

chemical balance

Exposure to radiation can alter cell structures and disturbe the cell's ____ & ultimately the way it operates

somatic cells

Irradiation of ____ ___ may disrupt body processes

genetic cells

Irradiation of ____ ___ may be passed to future generations in the form of genetic mutations

DNA or water

When radiation interacts with a cell, ionizations or excitations occur in ___ or ____?

site of interaction

The action of radiation on the cell is classified based on the ___ __ _____.

Direct action

interaction with master molecules (DNA)

indirect action

interaction occurs in water molecules

Direct Action

This type of action ay occur after exposre to any type of radiation but is MUCH more likely with high LET radiation

chemical bonds

When ionizing particles interact directly with DNA, RNA, proteins and/or enzymes the reasult is breakage of ____ ____, which makes them abnormal both structurally and functionally.

Indirect Action

this typeo f action occurs when radiation interacts with water which produces free radicals


If free radicals interact with DNA the damage to the DNA is what type of action?


what type of action is more likely to occur?

ions and free radicals

Indirect action involves the breakdown of a water molecule in to smaller molecules, producing what?

HOH+ and e-

If an interaction with water occurs, what ion pair is formed from the water molecule?


How much damage is caused when HOH+ and e- recombine?


Positive and negative water molecules are ___, or they will break apart into smaller molecules.

unpaired electron

what makes free radicals highly reactive?

normal water molecule

if Hydrogen and hydroxyl ions recombine the form what? (no harm)

single-strand break, double-strand break, mutation, and covalent cross-links

What are the 4 effets of ionizing radiation on DNA?

Single-strand Break

Which effect on DNA occurs in low LET radiations and breaks into 2 sugar-phosphate chain that repair enzymes can reverse

point mutation

when a DNA breaks into 1 sugar-phosphate chain

Double-strand break

Which effect on DNA occurs when one ore more breaks in both sugar-phosphate chains occur and is more common with high LET.


The loss or change in a nitrogenous ase on a DNA chain; the alteration of the base sequences

genetic information

what is contained in the strict sequences of DNA bases?

1 or 2

If the cell divides, the mutation will be transfered to how many of the daughter cells?

Covalent Cross-Links

Chemical unions created beween atoms by the single sharing of one or more pair of electrons; can occur in many different forms and are potentially fatal to the cell.


when changes occur in the DNA molecule what exhibits the alteration?

radiation-induced chromosome breaks, chromosomal fragments, and chromosomal anomalies

What are the 3 effects of Ionizing radiation on chromosomes?

Radiation-induced chromosome breaks

What may be viewed microscopically (metaphase and anaphase) and can happen to the chromosomes of somatic and germ cells?

Metaphase and anaphase

During which phases of mitosis can you view radiation-induced chromosome breaks?

chromosomal fragments

What is produced by chromosome breakage and have a fractured extremity that have the ability to adhere to each other?

chromosome anomalies

What are chromosome or chromatid aberrations that can be observed in metaphase?


During which phase of mitosis can you view chromosome anomalies?

Chromosome aberrations

Chromosome anomalies that result when radiation occurs before DNA synthesis; each daughter cell exhibits this

Chromatid aberrations

Chromosome anomalies that result when radiation occurs after DNA synthesis; only 1 daughter cell exhibits the aberration


break rejoins with no visible damage (structural change)


part of the chromosome or chromatid is lost at the next cell division (structural change)

Broken-end rearrangement

grossly mis-shapen chromosome may be reproductive without visible damage to the chromosomes (structural change)


what does broken-end rearrangement result in?

target theory

Concept that DNA is the "master" molecule in a cell, andif it is inactivated by exposure to radiation, the cell will die.


Interactions occur only by ___

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