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As Low As Reasonably Achievable


The largest part of the cell enclosed by the cell membrane

Late effect of radiation

A response to radiation exposure that doesnt appear for months, or even years

At what structural level do x-rays interact wih humans to produce a radiation response?

X-rays interact with electrons

How does inoizing radiation affect an atom within a large molecule?

The ionization can disrupt molecular bonds and cause the large molecule to malfunction.

What is the most abundant atom and molecule in the body?

Hydrogen, water

What is a stem cell?

The earliest stage of a cell line. An immature cell that will develop into a mature cell.

DNA is the abbreviation for what molecule?

Deoxyribonucleic acid

Which molecule is considered the genetic material of the cell?


What is the approximate dose of radiation required to produce a measurable physical change in a macromolecule?

1 Mrad (10 kGy)

List the stages of cell division of a somatic cell

G1, S, G2, M

List the stages of cell division of a genetic cell

The cell undergoes a mitosis-like divisions, and each of the resulting cells undergoes an additional mitosis-like division without DNA replication

What cell type is the most radiosensitive?

Spermatogonia and lymphocytes

What type of tissues is the least radiosensitive?

Nerve cells

List three early radiation effects and three late radiation effects in humans.

Skin erythema, organ atrophy,cytogenetic damage;
Cancer, leukemis,cataracts.

Linear energy transfer (LET)

Measure on the rate at which energy is transferred from a particular type of radiation to soft tissue. Approximately 3keV/m for diagnostic x-rays.

Standard radiation

250-500 kVp range

List 5 human groups in which radiation effects have been observed and thier effects of radiation.

Atomic bomb survivors-cancer and leukemia
American radiologist-life span shortening
Cyclotron physicist-cataracts
Radium watch dial painters- bone cancer
Patients irradiated in eutero- childhood cancer
Ankylosing spondylititis patients- leukemia

Oxygen enhancement ratio

A measure of the increased radiosensitivity of tissue in the presence of oxygen


One mode of cellular recovery from radiation damage

Threshold dose

Dose below which no effect occurs

Interphase death

Radiation effect that kills a cell before its next division


An early radiobiologist

What is the RBE formula

Rbe= Dose of standard radiation to produce an effect/ dose of test radiation to produce the same effect

What is fractionated radiation

a patient is given a dose at the same rate but broken into equal values and given over time

Why is high pressure oxygen used in radiation oncology?

To make them more radiosensitive

What is the formula for Oxygen Enhancement Ratio(OER)

OER= dose necessary under anoxic conditions/dose necessary under aerobic oxygenated conditions

How does age effect the radiosensitivity of tissue?

The younger the tissue, the more radiosensitive

When a radiobiologic expirement is conducted in vitro, what does this mean?

Outside of the human body at the cellular or molecular radiation

Name the three agents that enhance the effects of radiation.

Methotrexate, actinomycin D, vitamin K

Name 3 radioprotective agents.

Cysteine, cysteamine, and sulfhydryl goups

Are radioprotective agents used for human application?

No because they would have to be at a lethal dose.

What occurs in a nonlinear radiation dose-response relationship?

An equal amount of radiation dose will not produce an equal response.

State 2 of the corollaries to the Law of Bergonie and Tribondeau

Srem cells are more sensitive. Young tissue and organs are more radiosensitive than old tissues and organs. Tissue in a high state of metabolic ctivity has high radiosensitivity. As cellular proliferation increases, so does radiosensitivity.

What are the units of LET?


Describe how LET and RBE are related

With increasing LET, Rbe increases to a maximum value of approximately 3

Is occupational radiation exposure fractionated, or continuous?


Describe how OER and LET are related.

OER is LET-dependent. OER is highest for low LET radiation, and decreases for high LET radiation.

In vitro

Outside the body or outside the cell

Cytogenetic damage

radiation-induced structural change in chromosomes

Point mutation

Radiation damage that consists of a molecular lesion of the DNA and causes genetic mutation

Free radical

a short-lived, highly reactive, uncharged molecule that contains a single unpaired electron in the outermost shell

Target theory

The radiobiologic theory that says for a cell to die, after radiation exposure, its target molecule must be inactivated

List the effects of irradiation of macromolecules in solution in vitro.

main chain scission, cross-linking, point mutations, change in viscosity

How is solution viscosity used to determine the degree of radiation macromolecular radiation?

Viscosity drops after a high dose of radiation of macromolecules.Its a measure of the degree of main-chain scission of macromolecules.

In what phase of the cell cycle does the DNA ladder open up in the middle of each rung and consist of only a single chain

Sythesis phase

Name the three principale observable effects of DNA irradiation

Cell death, malignant disease, and genetic damage

Write the formula for radiolysis of water in which the atom of water is ionized and dissociates into two ions.

H20+ Energy in the form of radiation --> HOH+ + e-

What is the difference between vitro and in vitro?

In vitro refers to irradiation that occurs outside the body or outside the cell; in vivo irradiation is irradiation of the macromolecules in the living cell.

H2o+Radiation -->
HOH+ (dissociation)
HOH- (dissociation)

HOH+ +e-
H+ = OH*
OH- = H*

What is the difference between direct effect and indirect effect?

A direct effect exists when the ionizing radiation interacts directly with the target molecule of DNA.............

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