ACHRE Report
Final Report
Executive Summary
Preface
Introduction
Part I
Part II
Part III
Discussion: Part III
Part IV
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Glossary
Terms in italics appear in the Glossary as separate entries.
- Alpha radiation
- See Ionizing radiation.
- Association
- In statistics, the correlation or relationship between one
factor and one or more other pertinent factors as demonstrated by experimental
data.
- Atomic bomb
- An explosive device in which a large amount of energy is
released through the nuclear fission of uranium or plutonium. The first
atomic bomb test, known as the Trinity Shot, took place in the desert north of
Alamogordo, New Mexico, on July 16, 1945. Several weeks later, an atomic bomb
was used for the first time as an instrument of war, detonating over the
Japanese cities of Hiroshima (August 6) and Nagasaki (August 9).
- Atomic pile
- See Nuclear reactor.
- Becquerel
- See Units of radioactivity.
- Beta radiation
- See Ionizing radiation.
- Biodistribution
- The pattern and process of a chemical substance's
distribution through the body.
- Biological dosimeter
- See Dosimeter.
- Biopsy
- The removal and/or examination of tissues, cells, or fluids
from a living body for the purposes of diagnosis or experimental tests.
- Biophysics
- The application of physical principles and methods to the
study of the structures of living organisms and the mechanics of life
processes.
- Body burden
- The amount of a radioactive material present in a body
over a long time period. It is calculated by considering the amount of
material initially present and the reduction in that amount due to elimination
and radioactive decay. It is commonly used in reference to radionuclides
having a long biological half-life. A body burden that subjects the
body's most sensitive organs to the highest dose of a particular
radionuclide that regulators allow is known as a maximum permissible
body burden (MPBB).
- Bone marrow infusion
- The injection of bone marrow (an essential tissue
producing red and white blood cells and platelets) into the body, used
primarily to replace bone marrow destroyed by disease or in the course of
radiation and other therapies for certain types of cancer.
- Carcinogen
- A material that can initiate or promote the development of
cancer. Well-known carcinogens include saccharine, nitrosamines found in cured
meat, certain pesticides, and ionizing radiation.
- Chain reaction
- The process by which the fission of a nucleus
releases neutrons, causing other nuclei to undergo fission in turn. Both the
atomic bomb and the nuclear reactor use a chain reaction
to generate energy.
- Clinical trial
- A research study involving human subjects, designed to
evaluate the safety and effectiveness of new therapeutic and diagnostic
treatments.
- Common Rule
- The 1991 federal regulation that provides the basic
procedures and principles that are to be followed in the conduct of human
subject research sponsored by federal agencies.
- Critical mass
- The amount of fissionable material (uranium 235 or
plutonium 239) sufficient to sustain a nuclear chain reaction.
- Curie
- See Units of radioactivity.
- Cyclotron
- A device that uses alternating electric fields to accelerate
subatomic particles (a particle smaller than an atom, such as an alpha particle
or a proton). When these particles strike ordinary nuclei, radioisotopes
are formed. For his work in developing the cyclotron in the early 1930s,
Ernest Lawrence of the University of California received the 1939 Nobel Prize
in Physics.
- Deterministic effect
- An effect, such as kidney damage, whose severity
increases with increasing dose of radiation or other agent.
- Diagnostic procedure
- A method used to identify a disease in a living
person.
- Dosage
- The prescribed amount of medicine or other therapeutic agent
administered to treat a given illness.
- Dose
- In radiology, a measure of energy absorbed in the body from
ionizing radiation, measured in rad.
- Dose reconstruction
- The process of using information about an
individual's past exposures to ionizing radiation as well as general
knowledge about the behavior of radioactive materials in the human body and in
the environment to estimate the dose of radiation that someone
has received.
- Dosimeter
- An instrument that measures the dose of ionizing
radiation. A biological dosimeter is a biological or biochemical
indicator of the effects of exposure, such as a change in blood chemistry or in
blood count. A highly accurate biological dosimeter has yet to be
found.
- Dosimetry
- The measurement and calculation of radiation doses.
- Endocrinology
- The study of the body's hormone-producing glands, such as
the thyroid, pituitary, and adrenal glands, and the functions of the hormones
they synthesize and secrete.
- Epidemiology
- The study of the determinants (risk factors) and
distribution of disease among populations.
- Fallout
- Radioactive debris that falls to earth after a nuclear
explosion.
- Fission
- The division of an atomic nucleus into parts of comparable
mass. Generally speaking, fission may occur only in heavier nuclei, such as
isotopes of uranium and plutonium. Atomic bombs derive energy
from the fission of uranium or plutonium.
- Fission product
- An atom or nucleus that results from the fission
of a larger nucleus.
- Fusion
- The combining of two light atomic nuclei to form a single
heavier nucleus, releasing energy. Hydrogen bombs derive a large
portion of their energy from the fusion of hydrogen isotopes.
- Gamma radiation
- See Ionizing radiation.
- Genetic effects
- Changes in a person's germ calls (sperm or ova) that
are transmissible to future generations. Such changes result from mutations in
genes within the germ cells.
- Gray
- see Units of radioactivity.
- Half-life
- The average time required for one-half of the amount of
radioactivity of a radionuclide to undergo radioactive decay.
For material with a half-life of one week, half of the original amount of
activity will remain after one week; half of that (one-quarter of the original
amount) will remain after two weeks; and so on.
- Health physics
- A branch of physics specializing in accurate measurement
of agents, such as ionizing radiation, which can have effects on human
health.
- Hydrogen bomb (also known as a thermonuclear weapon)
- An explosive
weapon that uses nuclear fusion to release energy stored in the nuclei
of hydrogen isotopes. The high temperatures essential to fusion
are attained by detonating an atomic bomb placed at the H-bomb's
structural center. The United States tested the first hydrogen bomb in 1954 at
the Pacific Test Site.
- Institutional review board (IRB)
- Under the Common Rule, a local review
board convened by any institution conducting federally sponsored human subject
research, vested with the responsibility to review research proposals to ensure
compliance with federal research regulations.
- Internal emitter
- A radioisotope incorporated into a tissue in the body
that decays in place and continuously exposes that tissue to ionizing
radiation.
- Ionization
- The process by which a neutral atom or molecule loses or
gains electrons, thereby acquiring a net electrical charge. When charged, it
is known as an ion.
- Ionizing radiation
- Any of the various forms of radiant energy that
causes ionization when it interacts with matter. The most common types
are alpha radiation, made up of helium nuclei; beta radiation,
made up of electrons; and gamma and x radiation, consisting of
high-energy particles of light (photons).
- Irradiation
- Exposure to radiation of any kind, especially ionizing
radiation.
- Isotope
- A species of nucleus with a fixed number of protons and
neutrons. The term isotope is usually used to distinguish nuclear
species of the same chemical element (i.e., those having the same number of
protons, but different numbers of neutrons), such as iodine 127 and iodine 131.
- Latency period
- The time between when an exposure occurs and when its
effects are detectable as an injury or illness.
- Maximum Permissible Body Burden (MPBB)
- see Body burden
- Metabolism
- The manner in which a substance is acted upon (taken up,
converted to other substances, and excreted) by various organs of the body.
- Natural background radiation
- Ionizing radiation that occurs
naturally. Its principal sources are cosmic rays from outer space,
radionuclides in the human body, and radon gas (a decay product of
natural uranium in the earth's crust).
- Nuclear medicine
- A branch of medicine specializing in the use of
radionuclides for diagnostic and therapeutic purposes.
- Nuclear reactor
- A device containing fissionable material in
sufficient quantity and suitable arrangement to maintain a controlled,
self-sustaining nuclear chain reaction.
- Nuclide
- A type of nucleus with a fixed number of protons and neutrons.
The term nuclide is usually used to distinguish nuclear species
of different chemical elements (i.e., those having different numbers of
protons and neutrons), such as iodine 127 and uranium 235.
- Partial-Body Irradiation (PBI)
- Exposure of part of the body to
external radiation.
- Permissible dose
- In the judgment of a regulatory or advisory body,
such as the National Committee on Radiation Protection, the amount of
radiation that may be received by an individual within a specified
period.
- Principal investigator
- The scientist or scholar with primary
responsibility for the design and conduct of a research project.
- Protocol
- The formal design or plan of an experiment or research
activity; specifically, the plan submitted to an institutional review
board for review and to a government agency for research support.
Protocols include a description of the research design or methodology to be
employed, the eligibility requirements for prospective subjects and
controls, the treatment regimen(s), and the methods of analysis to be
performed on the collected data.
- Rad
- See Units of radiation
- Radiation
- The emission of waves transmitting energy through space or a
material medium, such as water. Light, radio waves, and x rays are all
forms of radiation.
- Radiation biology
- See radiobiology.
- Radiation oncology
- A branch of medicine specializing in the treatment
of cancer with radiation. Radiation therapy and radiotherapy are
equivalent terms.
- Radiation sickness
- Acute physical illness caused by exposure to
doses of ionizing radiation large enough to cause toxic
reactions. This can include symptoms such as nausea, diarrhea, headache,
lethargy, and fever.
- Radioactive decay
- The process by which the nucleus of a radioactive
isotope decomposes and releases radioactivity. For example, carbon 14
(a radioisotope of carbon) decays by losing a beta particle, thereby
becoming nitrogen 14, which is unstable.
- Radioactivity
- The decay of unstable nuclei through the emission of
ionizing radiation. The resulting nucleus may itself be unstable and
undergo radioactive decay. The process stops only when the decay
product is stable.
- Radiobiology
- Branch of biology specializing in the study of the
effects of radiation on biological molecules, cells, tissues, and whole
organisms, including humans. Radiobiology seeks to discover the
molecular changes responsible for radiation effects such as cancer induction,
genetic changes, and cell death.
- Radiogenic
- A term used to identify conditions observed to be caused by
exposure to ionizing radiation, such as certain kinds of cancer.
- Radioisotope
- A radioactive isotope. Radioisotopes are used in
medical research as tracers. See also isotope, nuclide,
and radionuclide.
- Radiological weapons
- Weapons that use radioactive materials to
cause radiation injury.
- Radionuclide
- A radioactive nuclide. Often used to distinguish
radioisotopes of different chemical elements, such as iodine 131 and
uranium 239.
- Radiopharmaceuticals
- Drugs (compounds or materials) that may be
labeled or tagged with a radioisotope. In many cases, these materials
function much like materials found in the body and do not produce special
pharmacological effects. The principal risk associated with these materials is
the consequent exposure of the body or certain tissues to radiation.
- Radioresistance
- The degree of resistance of organisms or tissues to
the harmful effects of ionizing radiation.
- Radiosensitivity
- The degree of sensitivity of organisms or tissues to
the harmful effects of ionizing radiation.
- Radiotherapy
- See radiation oncology.
- Rem
- See Units of radiation.
- Rep
- See Units of radiation.
- Roentgen
- See Units of radiation.
- Tolerance dose
- See Permissible dose.
- Total-Body Irradiation (TBI)
- Exposure of the entire body to external
radiation.
- Tracer
- A distinguishable substance, usually radioactive,
administered to determine the distribution and/or metabolism of
materials in the body. In 1923, George Hevesy was the first investigator to
use an isotope (radioactive thorium) in metabolic studies, exploring
lead transport in the bean plant. Metabolic studies proliferated after World
War II, when with the development of the cyclotron, radioisotopes
of various atoms became more widely available. Isotopes commonly
used as tracers today include carbon 14, iodine 131 and phosphorus 32.
- Transuranic elements
- Radioactive elements with atomic numbers (i.e.,
the number of protons in the nucleus) greater than 92. Only two of these
elements (plutonium in minute amounts and neptunium) occur in nature; the
others are produced in minute amounts through the radioactive decay of uranium.
The first transuranic elements were discovered as synthetic
radioisotopes at the University of California at Berkeley and the
Argonne National Laboratory in the 1930s and 1940s.
- Units of radiation
- The basic unit of radiation exposure is the
roentgen, named after Wilhelm Roentgen (discoverer of x rays). It is a
measure of ionization in air, technically equal to one ESU
(electrostatic unit) per cubic centimeter, due to radiation. A rep
(roentgen equivalent physical) is an archaic measure of skin exposure to a
dose of beta radiation having an effect equivalent to 1
roentgen of x rays. The basic unit of radiation absorbed by the
body is the rad, technically equal to 100 ergs (energy unit) per gram of
exposed tissue. One roentgen corresponds to roughly 0.95 rad.
The rem (roentgen equivalent in man) is a unit of effective dose,
a dose corrected for the varying biological effectiveness of various types of
ionizing radiation. The currently accepted unit of radiation is the
gray (Gy), the International System unit of absorbed dose, equal to the
energy imparted by ionizing radiation to a mass of matter corresponding to one
joule per kilogram.
- Units of Radioactivity
- The becquerel (Bq), named after
the physicist Henri Becquerel (the discoverer of radioactivity),
is a measure of radioactivity equal to one atomic disintegration per
second. The curie (Ci), whose name honors the French scientists Marie
and Pierre Curie (the discoverers of radium), is a standard based on the
radioactivity of 1 gram of radium. It is equal to 3.7 x 1010
becquerels.
- X rays
- Invisible, highly penetrating electromagnetic radiation
of a much shorter wavelength than visible light, discovered in 1895 by
Wilhelm C. Roentgen. Most applications of X rays are based on their
ability to pass through matter. They are dangerous in that they can destroy
living tissue, causing severe skin burns on human flesh exposed for too long a
time. This property is applied in x-ray therapy to destroy diseased cells.
See Ionizing radiation.
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