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GLOSSARY
387
Radiopaque A classification for objects
that block radiation rather than allow it to
pass through. Lead is the most common
example.
Radiosensitivity Comparable sensitivity
of human cells, tissues, and organs to the
injurious action of ionizing radiation.
Radio waves Electromagnetic waves which
have frequencies from 300 GHz to as low as
3 kHz, and corresponding wavelengths
from 1 millimeter to as large as 100 kilometers. Their range of frequencies and wavelengths is very extensive.
Radium This element (Z 5 88, A 5 226)
has an unstable nucleus and decays with a
half-life of 1622 years by alpha particle
emission to the radioactive element radon
(Z 5 86, A 5 222).
Radon (Z 5 86, A 5 222) The first decay
product of radium. Radon is a colorless,
odorless, heavy radioactive gas (T
5
1/2
3.8 days) that, along with its own decay
products, polonium-218 and polonium-214 (solid form), is always present
to some degree in the air. It comprises the
largest component of natural background radiation and is predominantly
an alpha particle emitter during its decay
sequence.
Rayleigh scattering See Coherent scattering.
Recessive mutation A genetic mutation
that probably will not be expressed for several generations because both parents must
possess the same genetic characteristic.
Recoil electron See Compton scattered
electron.
Reconstruction interval This refers to
the selected generated or displayed spacing between adjacent slices being a chosen
amount (gapping) or being contiguous
(no spacing) or overlapping.
Relative biologic effectiveness (RBE)
Describes the relative capabilities of radiation with differing linear energy transfers (LETs) to produce a particular
biologic reaction. Simply defined, it is the
ratio of the dose of a reference radiation
(conventionally, 250 kVp x-rays) to the
dose of radiation of the type in question
that is necessary to produce the same
biologic reaction in a given experiment.
The reaction is produced by a dose of the
test radiation delivered under the same
conditions.
Relative risk Model predicting that the
number of excess cancers will increase as
the natural incidence of cancer increases
with advancing age in a population.
Rem (radiation equivalent man) Tradi-
tional unit for the radiation quantity
equivalent dose (EqD); defined as the
dose that is equivalent to any type of ionizing radiation that produces the same
biologic effect as 1 rad (radiation absorbed dose) of x-radiation.
Remnant radiation See Exit, or image
formation, radiation.
Repair enzymes Enzymes that can mend
damaged molecules and are therefore capable of helping the cell to recover from a
small amount of radiation-induced damage.
Repeat analysis program An attempt to
record the various causes of inadequate
quality on occasions when an image has
to be retaken (i.e., a repeat image).
Reproductive cells Male and female
germ cells (relatively radiosensitive).
Reproductive death The permanent loss
of a cell’s ability to divide because of exposure to doses of ionizing radiation in
the range of 1 to 10 Gy. The cell itself does
not die but continues to metabolize and
synthesize nucleic acids and proteins.
Restitution A process in which chromo-
some breaks rejoin in their original configuration with no visible damage.
Retina A curved sheet or layer at the rear
of the eyeball containing cells that are
sensitive to light (rods and cones) and
that trigger nerve impulses that pass via
the optic nerve to the brain where a visual
image is formed.
Ribonucleic acid (RNA) Type of nucleic
acid that carries genetic information from
the DNA in the cell nucleus to the ribosomes located in the cytoplasm.
Ribose A simple sugar and carbohydrate
with molecular formula C5H10O5.
Ribosomal RNA (rRNA) Type of RNA
that assists in the linking of messenger
RNA (mRNA) to the ribosome to facilitate protein synthesis.
Ribosomes Very small, spherical, cyto-
plasmic organelles that attach to the endoplasmic reticulum; they are the assembly
sites where mRNA and tRNA combine
amino acids into proteins. They are the
cell’s “protein factories.”
Right-to-Know Act (Employee) A series
of statutes passed by individual states requiring that employees be made aware of
the hazards in the workplace. This act
covers hazardous substances, infectious
agents, ionizing radiation, and nonionizing radiation.
Risk In general terms, the probability of
injury, ailment, or death resulting from an
activity. In the medical industry with reference to the radiation sciences, risk is the
possibility of inducing a radiogenic cancer or genetic defect after irradiation.
Road mapping A method of digital image
subtraction in which the frame that contains the greatest amount of contrast material in vessels is identified and is then
subtracted from all subsequent images.
Live fluoroscopic images of the catheter
moving through the vasculature can then
be seen even after the vessels contain less
contrast.
Roentgen (R) Internationally accepted
traditional unit of measurement of exposure to x-radiation and gamma radiation.
One roentgen is the photon exposure that
under standard conditions of pressure
and temperature produces a total positive
or negative ion charge of 2.58 3 (10)24
coulombs per kilogram of dry air.
Rung A step in the DNA ladder-like struc-
ture composed of a pair of nitrogenous
bases.
S
Saccharides See Carbohydrates.
Salts Chemical compounds resulting
from the action of an acid and a base on
each other. They are sometimes referred
to as electrolytes.
Sarcophagus Large concrete shelter con-
structed by the Soviet Union atop the remains of the Reactor 4 building after the
Chernobyl nuclear accident to provide
protection from radiation exposure.
Scan direction collimation The product
of the number of data channels or detector rows used during one axial acquisition
(N) and the size or width of a data channel or individual detector (T).
Scattered radiation All the deflected ra-
diation that arises from the interaction of
an x-ray beam with the atoms of a patient
or any other object in the path of the
beam.
Scintillator A substance that undergoes
atomic transitions causing it to emit visible radiation or “glow” when hit by highenergy particles or photons.
388
GLOSSARY
Scotopic vision Rod vision (night vi-
sion).
Scout view A preliminary radiographic
image of a desired portion of a patient’s
anatomy in either the coronal or sagittal
direction obtained before performing a
CT scan in that region.
Secondary electron See Compton scat-
tered electron.
Secondary protective barrier A barrier
that affords protection from secondary
radiation (leakage and scattered radiation) only; as such, it is not designed to
intercept the direct x-ray beam or to provide adequate attenuation of the beam.
Secondary radiation The radiation that
results from the interaction between primary radiation and the atoms of the irradiated object and the off-focus, or leakage, radiation that penetrates the x-ray
tube protective housing.
Semipermeable membrane A structure
that permits the passage of a pure solvent
such as water but does not allow material
dissolved by the solvent to pass through it.
Shadow shield A shield of radiopaque
material suspended from above the radiographic beam-defining system; these
shields are positioned at some distance
above the patient to cast a radiation protection shadow in the primary beam over
the area spanned by the patient’s reproductive organs.
Shallow equivalent dose The external
exposure of the skin or extremity at a tissue depth of 0.007 cm averaged over an
area of 1 cm2.
Shaped contact shield A cup-shaped ra-
diopaque shield, containing 1 mm of lead
that is contoured to enclose the scrotum
and penis to protect the male reproductive organs from exposure to ionizing radiation.
Shielding Radiation-absorbent barrier of
appropriate thickness used to provide protection from radiation. The most common materials used for structural barriers
are lead and concrete. Accessory devices
such as aprons, gloves, and thyroid shields
are made of lead-impregnated vinyl to
provide shielding from radiation exposure
when individuals cannot remain behind a
protective structural barrier during certain imaging procedures.
Shift and add algorithm (SAA) The con-
ventional method of image reconstruction
used in digital breast tomosynthesis to
generate in-focus slice images by shifting
and then adding projection images of registered structures in the breast acquired at
multiple viewing angles.
Side scatter Photons that interact signifi-
cantly with the atoms of an object and
consequently are deflected to the side.
Sievert (Sv) The SI unit of measure for
the radiation quantities, equivalent dose
(EqD), and effective dose (EfD). It is the
product of the absorbed dose and the radiation weighting factor. For x-radiation
(Q 5 1) one sievert equals one joule of
energy absorbed per kilogram of tissue.
This unit is used only for radiation protection purposes. It provides a common
scale whereby varying degrees of biologic
damage caused by equal absorbed doses
of different types of ionizing radiation (Q
equals one or greater) can be compared
with the degree of biologic damage
caused by the same amount of x-radiation or gamma radiation. In the traditional system, 100 rem equals 1 sievert.
Sigmoid or “S-shaped” (nonlinear),
threshold curve of radiation dose–response Generally employed in radia-
tion therapy to demonstrate high-dose
cellular response. This curve indicates the
existence of a threshold. Different effects
require different minimal doses.
Signal-to-noise ratio (SNR) The com-
parison of the average computed tomography (CT) number in a region with the
statistical variation of CT number in that
region.
Single-strand break The ionization of a
DNA macromolecule resulting in a break
of one of its chemical bonds, thereby
severing one of the sugar–phosphate
chain side rails or strands of the ladderlike DNA molecular structure.
Skin dose In general represents the ab-
sorbed dose to the most superficial layers
of the skin.
Skin erythema dose The received quan-
tity of radiation, amounting roughly to an
absorbed dose of several gray to a portion
of skin surface, that causes diffused redness over an area of skin usually at some
short period of time after irradiation.
Small angle scatter Photons that pass
through the patient being radiographed,
interact with the atoms of the body, and
are deflected at such a small angle that
they can reach the image receptor, thereby
degrading the completed radiographic
image by introducing small amounts of
off focus signal or fog.
Solid angle A measure of the amount of
the field of view from some particular
point that a given object covers. That is, it
is a quantification of how large the object
appears to an observer looking from that
point. The dimensionless unit of solid
angle is the steradian, with 4p steradians
covering or encompassing a full sphere
field of view.
Somatic cells All the cells in the human
body other than female and male germ
cells.
Somatic tissue reactions Biologic reac-
tions in tissues of the body that were irradiated that can be directly related to the
dose of ionizing radiation received. These
are cell-killing responses that exhibit a
threshold dose below which the reactions
are absent and above which the severity of
the early tissue reactions increases as the
radiation dose increases.
Source-to–image receptor distance
(SID) The distance from the x-ray tube
anode focal spot to the radiographic image receptor or detector.
Source-to-skin distance (SSD) The dis-
tance from the anode focal spot of an xray tube to the skin of the patient.
Spacer bar A device that projects down
from the housing of some collimators to
prevent the collimators from being closer
than 15 cm to the patient.
Spatial Resolution The ability to distin-
guish between closely spaced objects. Often quantitatively described in terms of
the number of clearly resolved line pairs
per millimeter.
Specific area shielding The use of lead
or lead-impregnated material to protect
selective body areas from exposure to ionizing radiation.
Spermatocytes Sperm cells at their in-
fancy. They divide by meiosis to produce
cells with half the number of chromosomes.
Spermatogonium The male germ cell.
Spiral computed tomography In com-
puted tomography (CT), a data acquisition method that combines a continuous
gantry rotation with a table advance
movement to form a spiral path of acquired scan data. It is also known as heli-
cal CT.
Spontaneous mutations A natural phe-
nomenon involving alterations in genes
GLOSSARY
389
and DNA. These mutations occur at random and without a known cause.
Standardized dose reporting A system
of standardizing or regulating a patient’s
radiation dose by having the dose dictated
into the patient’s report and then tracking
the dose amount for any subsequent similar procedures.
Stem cells Immature or precursor cells.
Stem radiation See Off-focus radiation.
Stent A tubular support that can be
placed inside a blood vessel, canal, or duct
to open up a previously obstructed or
narrowed pathway.
Steradian The SI unit of solid angle. It is
the angle at the center of a sphere generated by a portion of the surface area of the
sphere equal to the square of its radius.
Stochastic effects Mutational or ran-
domly occurring biologic changes, independent of dose, in which the chance of
occurrence of the effect rather than the
severity of the effect is proportional to the
dose of ionizing radiation. These effects
occur months or years after high level, and
possibly also after low level, radiation exposure. Examples include cancer and genetic effects. Also called probabilistic effects.
Structural proteins Those proteins from
which the body acquires its shape and
form. They also are a source of heat and
energy.
Sunspots Temporary phenomena on the
Sun’s photosphere (visible surface of the
Sun) that appear as spots darker than the
surrounding areas. They are regions of
reduced surface temperature caused by
concentrations of magnetic field flux that
inhibit normal heat convection. This can
induce a sudden explosion of energy
called a solar flare. Solar flares are sometimes accompanied by a mass ejection
comprised of huge bubbles of radiation
and particles.
Surface contamination External con-
tamination of the skin or clothing of an
individual with radioactive material.
Surface integral dose The total amount
of radiant energy transferred by ionizing
radiation to the human body surface or
superficial skin area during a radiation
exposure.
Syndrome A collection of symptoms.
Systole and diastole Two phases of the
cardiac compression/relaxation cycle. Systole occurs when the heart contracts to
pump blood out, and diastole occurs
when the heart relaxes or returns to its
normal volume after contraction.
T
Target theory Concept of radiation dam-
age resulting from discrete and random
events. If a critical location on the master
molecule (believed to be DNA) is a target
receiving multiple hits from ionizing radiation, it may well be inactivated. Normal cell function will then cease, and the
cell will die. If, on the other hand, it receives only a single hit, then the master
molecule most likely will still be operational. The target theory concept may be
useful for explaining cell death and nonfatal cell abnormalities caused by exposure to radiation.
Technetium-99m (
99m
Tc) A gamma-
emitting radioisotope with a 6-hour halflife that is produced from the beta decay
of another unstable isotope, molybdenum-99. Technetium-99m is the most
common radioisotope used in nuclear
medicine studies.
Telangiectasia Dilation of capillaries and
sometimes of terminal arteries of an organ.
Telophase The phase of mitosis during
which cell division is completed with the
formation of two new daughter cells, each
of which contains exactly the same genetic material as the parent cell.
Temporal resolution The ability to dis-
tinctly resolve (i.e., remove blur from)
fast-moving objects.
Teratogenesis Birth effects induced by ir-
radiation in utero.
Terrestrial radiation Long-lived radioac-
tive elements such as uranium-238, radium-226, and thorium-232 that emit
densely ionizing radiations (alpha particles) as part of their decay processes.
These sources are present in variable
quantities in the crust of the earth.
Therapeutic ratio The ratio obtained by
dividing the effective therapeutic dose by
the minimum lethal dose; a comparison
of the amount of a therapeutic agent that
causes the therapeutic effect to the
amount that causes toxicity. In radiotherapy, the therapeutic ratio denotes the
relationship between the probability of
tumor control and the likelihood of normal tissue damage.
Thermal neutron Nominally classified as
a neutron whose kinetic energy is approximately equal to 1 eV. Typically, these
are neutrons whose kinetic energy has
been significantly degraded as a result of
multiple energy loss collisions.
Thermoluminescent dosimeter ring
(TLD) A personnel monitoring device
that most often contains a crystalline
form of lithium fluoride as its sensing
material. When this device is placed in a
TLD analyzer and heated, the crystals
emit visible light in proportion to the
amount of radiation to which the TLD
dosimeter ring was exposed. A graphic
plot of this light intensity (also known as
thermoluminescence intensity) versus the
heating temperature is known as a “glow
curve.” The glow curve represents a
unique signature of the exposure received
by the TLD dosimeter ring.
Thompson scattering The elastic scatter-
ing of an x-ray photon by a free electron.
Thoron A radioactive decay product of an
isotope of radon, namely radon-220, with
a half-life of 54.5 seconds. It is given the
name thoron because radon-220 was itself
derived from the radioactive decay of thorium-232, a naturally occurring material.
Threshold (1) The point at which a re-
sponse or reaction to an increasing stimulation first occurs; (2) with reference to
ionizing radiation, this means that below
a certain radiation level or dose, no biologic effects are observed.
Thrombocytes See Platelets.
Thrombocytopenia A disorder in which
there is a relative decrease of thrombocytes, commonly known as platelets, present in the blood. A normal human platelet
count ranges from 150,000 to 450,000
platelets per microliter of blood.
Thymine (T) A pyrimidine base found
only in DNA.
Thymus gland An organ of the lymphatic
system, located in the mediastinal cavity
anterior to and above the heart. It plays a
critical role in the body’s defense against
infection.
Thyroid gland A gland located in the
neck just below the larynx. The hormone
produced by this gland helps regulate the
body’s metabolic rate and the process of
growth.
Thyroid shield See Protective apparel.
Time A method of radiation protection that
reflects the fact that the amount of radiation a worker receives is directly proportional to the length of time that the individual is exposed to ionizing radiation.
390
GLOSSARY
Time interval difference A method of
digital image subtraction in which each
image is subtracted from an image a few
frames in advance. This technique reveals
vessels containing contrast material and
suppresses soft tissue in the images. It is
less sensitive to patient motion than when
the first image (also known as a “mask”) is
subtracted from all successive images.
Tissue reactions Any radiation effects on
organ or organ systems that increase with
increasing dose, and below a certain dose
level, the effect rarely or never occurs.
They may occur as early effects, immediately after irradiation, or late effects, after
some latent period.
Tissue weighting factor (WT) A value
that denotes the percentage of the summed
stochastic (cancer plus genetic) risk stemming from irradiation of specific tissues to
the all-inclusive risk when the entire body is
irradiated in a uniform fashion.
Title 10 of the Code of Federal Regula-
tions, Part 20 A document prepared
and distributed by the US Office of the
Federal Register. The rules and regulations of the Nuclear Regulatory Commission (NRC) and fundamental radiation
protection standards governing occupational radiation exposure are included in
this document.
TLD ring badge See Extremity dosimeter.
Tolerance dose A radiation dose to which
occupationally exposed persons could be
continuously subjected without any apparent harmful acute effects, such as erythema of the skin.
Tomosynthesis A method of obtaining a
three-dimensional x-ray image of an object by combining multiple obtained infocus planar images each obtained at different depths using an x-ray beam that
moves in a limited arc about the object
with a center of rotation for each arc at
the desired imaging depth. Planar depths
above and below the center of rotation
plane will be blurred. This technique,
modified so that isocenter changes are not
needed and with the application of specialized computer image reconstruction
algorithms, can also be successfully applied to digital mammography.
Total effective dose equivalent (TEDE) A
system of units and quantities used to
monitor occupationally exposed personnel
such as nuclear medicine technologists and
interventional radiologists. TEDE is the
sum of effective dose equivalent from external radiation exposures and the committed effective dose equivalent (CEDE)
from internal sources. It is designed to take
into account all possible causes of radiation exposure.
Total filtration Inherent filtration plus
added filtration.
Traditional units Long established funda-
mental units associated with radiation
protection and dosimetry, namely, the
roentgen and the rad.
Transfer RNA (tRNA) Type of RNA that
combines with individual amino acids
from different areas of the cell and attaches or transfers them to the ribosomes.
Trimester A 3-month period of embryo/
fetal gestation or development (i.e., first,
second, and third trimesters).
Tubules Minute tubes which are a major
transport component of the cell’s endoplasmic reticulum.
Tungsten A metal with a high melting
point (greater than 3400°C or 6100°F)
and a high atomic number (Z 5 74). In
an x-ray tube, tungsten is a major component of both the filament (cathode) and
the target (anode).
Tungsten rhenium (W/Rh) A metal alloy
with a high melting point (greater than
3000°C) and a high atomic number. The
anode of a general purpose x-ray tube is
usually made of this alloy.
U
Ulceration The process of pus or dis-
charge formation on a surface, such as the
skin or a mucous membrane, to form an
ulcer.
Umbra See Primary radiation.
Uncontrolled area Area such as a nearby
hallway or corridor that can be frequented
by the general public.
Undifferentiated cells Immature or
nonspecialized cells.
Unit A fixed amount of some property or
characteristic (e.g., distance in meters,
time in seconds, energy in joules) used as
a measure for which other amounts of
that property or characteristic can be precisely described.
United Nations Scientific Committee on
the Effects of Atomic Radiation (UNSCEAR) A group that plays a promi-
nent role in the formulation of radiation
protection guidelines. This group evaluates human and environmental ionizing
radiation exposure from a variety of
sources and research conclusions to derive radiation risk assessments for radiation-induced cancer and for genetic (hereditary) effects.
Unmodified scattering See Coherent
scattering.
Unnecessary radiologic procedure Any
radiation examination that does not benefit a person in terms of the diagnostic
information obtainable and thus for
which there is no sufficient justification to
subject a patient to the risk of the absorbed radiation dose resulting from the
procedure.
Uracil (U) A pyrimidine base found only
in RNA. It replaces thymine (T) as the
nitrogenous base in ribonucleic acid.
US Code of Federal Regulations Docu-
ment prepared and distributed by the US
Office of the Federal Register that contains the rules and regulations of the Nuclear Regulatory Commission (NRC) and
the radiation protection standards governing occupational radiation exposure.
Use factor (U) For primary radiation, the
use factor represents the portion of beamon time that the x-ray beam is targeted or
directed at a particular barrier during the
week. Also known as beam direction factor.
Useful beam See Primary radiation.
V
Vacuum discharge tube A glass tube con-
taining a gas and two electrodes sealed
through its walls. When a substantial electrical potential difference is established
between the two electrodes and the pressure of gas in the tube is reduced enough, a
situation will be reached at which a current
flows through it, and energetic interactions
occur such that the gas begins to glow.
Variable rectangular collimator A box-
shaped device containing the radiographic beam-defining system; the device
is most often used to define the size and
shape of the radiographic beam.
Vasculitis An inflammation of the blood
vessels. It causes changes in the walls of
blood vessels, including thickening, weakening, narrowing, and scarring. These changes
obstruct or hamper blood flow, leading
eventually to organ and tissue damage.
Vesicle Small cavities or sacs containing
liquid.
Volt (V) SI unit of electrical potential and
potential difference.
GLOSSARY
391
Voltage Electrical potential at a point or
position relative to ground potential.
Voluntary motion Motion controlled by
will (i.e., skeletal muscle).
Voxel A unit of graphic information that
defines a region in three-dimensional
space. Unlike a pixel (picture element)
which defines an area in two-dimensional space with its x and y coordinates,
a voxel also includes a third dimension or
z coordinate and therefore defines a volume element.
W
Wavelength Distance between two con-
secutive crests or troughs in a wave (given
in meters or some fraction thereof).
Wave-particle duality Electromagnetic
radiation can travel and interact with
matter in the form of a wave or a particle.
For this reason, x-rays may be described
as both waves and particles.
Window level Sets the midpoint of the
range of densities visible on a digital image.
Workload (W) Essentially the radiation
output weighted time that an x-ray
machine is actually delivering radiation
during the week. It is specified either in
units of milliampere-seconds (mAs) per
week or milliampere-minutes (mA-min)
per week.
World Health Organization The author-
ity that directs and coordinates for health
within the United Nations system.
X
X-ray beam limitation device Any de-
vice that limits the dimensions of the
useful beam to a designated size and
shape before it enters the area of clinical
interest.
X-rays (x-ray photons) Electromagnetic
radiation that emerges from the anode of
an x-ray tube after bombardment by
high-speed electrons in a highly evacuated glass tube or from an atom that has
experienced a photoelectric interaction.
The latter are typically called characteris-
tic x-rays.
I N D E X
Page numbers followed by “f” indicate figures, “t” indicate tables, and “b” indicate boxes.
A
Abdominal radiologic examinations, of
female patients, 240
Abortion, after irradiation of unknown
pregnancy, 240–241, 242b
Absolute risk model, for cancer, 158, 159f
Absorbed dose (D), 4, 20, 35–36,
64–65, 64b, 65b, 212–213
Absorption, 35–36, 35f. see also
Photoelectric absorption
body structures and, 44, 45f
significance of, 35–36, 36f
Accessory protective devices, 303–304
Acentric fragment, 122, 123f
Acids, in cell, 97
Action limits, 189
Acute radiation lethality, 142, 143t
Acute radiation syndrome (ARS),
140–143
after Chernobyl nuclear power plant
accident, 142–143
after Nagasaki and Hiroshima
atomic bombing, 143
medical management of, 337–338
symptoms of, 140–142, 141f
Adenosine triphosphate (ATP), 101,
101f
Advisory Committee on X-Ray and
Radium Protection. see National
Council on Radiation Protection
and Measurements
AEC. see Automatic exposure control
Agreement states, 178, 178t
Air gap technique, 235, 236f
Air kerma, 64
Air travel, radiation exposure due to, 25
ALARA. see As low as reasonably
achievable (ALARA) principle/
concept
Alert levels, 12
Alliance for Radiation Safety in
Pediatric Imaging, 10–11, 247
Alopecia, 146
Alpha particles, 19–20, 23–24, 113b,
114f, 115–116
American College of Radiology,
position on abdominal radiologic
examinations of female
patients, 240
Amino acids, 90–91, 90f
Ampere, 63–64
Analyzer, TLD, 75
Anaphase, 105f, 106
Anatomic structures. see Body
structures
Annihilation photons, 50–51
Annihilation radiation, 50–51, 324
Annual occupational effective dose
limit, 186, 294–295
Anode, 36
Antibodies, 91
Antigens, 91
Aplastic anemia, 56–57
Apoptosis
as cellular effect of irradiation, 127
radiosensitivity and, 127
Apron. see Protective apron
Area monitoring
detection and measurement for, 81
ionization chamber-type survey
meter for, 82f
ARS. see Acute radiation syndrome
Artificial radiation. see Human-made
(artificial) radiation
As low as reasonably achievable
(ALARA) principle/concept,
6–7, 7f
cardinal rules of radiation
protection and, 7
dose limits and, 181, 182f
in imaging personnel radiation dose,
294–295, 296f
responsibility for maintaining,
7–8, 8b
Atmospheric fallout, 25, 26f
Atomic bomb survivors, carcinogenesis
and, 161–164, 162f
Atomic bombing, acute radiation
syndrome after, 143
Atomic Energy Commission, 177
Atomic number, 20. see also Effective
atomic number
Compton scattering and, 41t, 48–49
pair production and, 41t
photoelectric absorption and,
41–48, 41t
ATP. see Adenosine triphosphate
Atrophy, tissue, 144
Attenuated photons, 37–38, 38f
Attenuation
direct and indirect transmission
x-ray photons, 37
effects on radiographic images,
44–45, 45f, 46f
primary, exit, and attenuated
photons in, 37–38, 38f
Auger effect, 43
Auger electron, 43
Automatic collimation system, 247
Automatic exposure control (AEC),
204–206, 204f, 255
B
B lymphocyte, 91
Background equivalent radiation time
(BERT), 8–9, 10t
Background radiation. see Natural
radiation
Barrier shielding, calculating, 312–315
Bases, in cell, 97
Beam direction factor. see Use factor
Beam-on indicator sign, 315
Benign postpartum mastitis, radiation
treatment of, 161
BERT. see Background equivalent
radiation time
Beta decay, 19–20, 322
Beta particles, 19
Bilateral wedge filter, 203
Biologic damage
blood cell response to ionizing
radiation, 129–131
cellular effects of ionizing radiation.
see Cellular effects
current measurement of, 60–61
392
Biologic damage (Continued) Cancer, radiation-induced (Continued)Blood cells, radiation effects on
electromagnetic energy absorption
and, 35–36
energy transfer determinants, 112–116
linear energy transfer, 112–115,
113b, 113f, 114f
oxygen enhancement ratio,
115–116, 116b
relative biologic effectiveness, 115,
115b
epithelial tissue response to ionizing
radiation, 131
equivalence of damage from different
radiation sources, 65, 65t
first reports of, 56–57
mammalian cell survival curves in,
127–128
muscle tissue response to ionizing
radiation, 131
nervous tissue response to ionizing
radiation, 131–132, 131f
radiation potential for, 20–21, 21t
reproductive cell response to
ionizing radiation, 132–133
Biologic dosimetry, 142–143
Biologic effects
of ionizing radiation, safeguard
against, 4–5
medical management for, 337–338,
338t
Biologic tissue
absorbed dose and, 64–65
dose limits for, 189
local tissue damage in, 144, 145f
reproductive system, 147, 147f
skin, 145–146, 145f
structural changes in, 122
Biology. see Cell biology; Radiation
biology
Birth defects. see Embryologic effects
Blood, radiation effects on
erythrocytes, 148, 148f
granulocytes, 148, 148f
hematologic depression, 21t, 129,
147–148
hematopoietic syndrome, 141, 141f
lymphocytes, 21t, 148, 148f
pluripotential stem cells, 148, 148f
thrombocytes, 148, 148f
Blood cells, radiation effects on, 129–131
depletion of immature blood cells
as, 129
(Continued)
during diagnostic imaging
procedures, 131
erythrocytes, 148, 148f
granulocytes, 148, 148f
hematologic depression, 129
lymphocytes, 21t, 130, 148, 148f
neutrophil, 130–131
occupational radiation exposure
monitoring and, 131
during radiation therapy treatment,
131
repopulation after period of
recovery, 129
stem cell, 129–130, 148, 148f
thrombocytes, 131, 148, 148f
whole-body doses in excess of 5Gyt,
130, 130t
Body language, for effective
communication, 229
Body structures
contrast media for visualization of,
47–48, 47f
photoelectric absorption by, 46–47
Bone, photoelectric absorption by, 46–47
Bone marrow dose, 30, 30t, 238–239
“Bone marrow syndrome.” see
Hematopoietic syndrome
Brachytherapy, 320–321
Bragg-Gray theory, 61
Breast cancer. see also Mammography
benign postpartum mastitis
radiation treatment and, 161
Chernobyl nuclear power plant
accident causing, 27–28, 164f, 168
in Japanese atomic bomb survivors,
163
risk models for predicting, 156, 156f
Brightness, 198–199
Broken-end rearrangement, 122, 124f
Bucky slot shielding device, 306, 306f
C
C. see Coulomb
Cancer, radiation-induced, 160–165
Chernobyl nuclear power plant
accident causing, 27–28
effective dose (EfD) limiting system,
175
epidemiology and, 154
first reports of, 56–57
INDEX
from low-level radiation exposure,
risk estimate of, 157–158
radon exposure and, 23
risk estimates for, 158–165
risk models for predicting, 155–156,
156f
Three Mile Island Unit 2 and,
25–26
Cancer treatment, linear accelerator
for, 19–20
Candela per square meter, 198–199
Carbohydrates, in cell, 91–92, 91b
Carbon, 24, 50–51
Carbon fiber, 196
Carcinogenesis, 154
evidence of radiation-induced,
160b
benign postpartum mastitis radia-
tion treatment patients, 161
Chernobyl nuclear power plant
accident conclusions,
164–165, 164f
early medical radiation workers,
161, 161f
Japanese atomic bomb survivors
and, 161–164, 162f, 163f
life span shortening and,
165–166
radium watch-dial painters and,
160
uranium miners, 160–161
Cardiovascular imaging (CVI),
262–271
contrast resolution, 269
ECG gated imaging, 265–269, 266b,
267f
heart anatomy and processes, 263,
264b
heart beat rate, 267–268
image noise, 271, 271t
patient radiation doses and volume
scanning, 270–271
phases, cardiac cycle, 265
radiation doses, 269–270, 270f
spatial resolution, 268–269
temporal resolution, 268
C-arm fluoroscopy
exposure reduction, 308
mobile, 217, 217f
personnel exposure, scattered
radiation, 307, 307f
393
394
INDEX
C-arm fluoroscopy (Continued)
positioning of, 308
protection during, from imaging
personnel radiation dose,
307–308
Cataractogenesis, 158, 166–167, 166f
CDRH. see Center for Devices and
Radiological Health
CEDE. see Committed effective dose
equivalent
Cell(s), 89. see also Blood cells;
Reproductive cells
consequences of ionization in, 2b
inorganic compounds of, 97–98, 98f
organic compounds of, 90–97, 90b
carbohydrates, 91–92, 91b
lipids, 92, 92b
nucleic acids, 92–97
proteins, 90–91, 91f
protoplasm of, 89–90, 90b, 90f
radiosensitivity of, 128–133
blood cell response on ionizing
radiation, 129–133
cell maturity and specialization
effects on, 128, 128b
epithelial tissue response to
ionizing radiation, 131
law of Bergonié and Tribondeau,
129
muscle tissue response to ionizing
radiation, 131
nervous tissue response to ionizing
radiation, 131–132, 131f
oxygen enhancement effects on,
128–129
reproductive cell response to
ionizing radiation, 132–133
structure of, 98–103, 99f
cell membrane, 99
cytoplasm, 99–100, 100b
cytoplasmic organelles, 100–102
nucleus, 102–103, 102f
Cell biology, 88–110
Cell division, 103–108, 104f
meiosis, 106–108, 107f, 108f
mitosis, 104–106, 105f, 106f
anaphase, 105f, 106
interphase, 105f, 106–107
metaphase, 105–106, 105f,
148–149
prophase, 105
telophase, 105f, 106
Cell membrane, 99
Cell survival curves, mammalian,
127–128, 128f
Cellular damage, from radiation, 20
Cellular effects, of irradiation, 126–127
apoptosis as, 127
instant death as, 126
interference with function, 127
mitotic death as, 127
mitotic delay as, 127
reproductive death as, 127
Cellular response, high-dose, risk
model for, 156–157, 156f
Center for Devices and Radiological
Health (CDRH), 180
Centigray (cGy), 64–65, 65b
Centrosome, 102, 102f
Cerebrovascular syndrome, 142, 143t
Cesium, 29
Characteristic photon, 42–43, 42f
Characteristic x-ray, 43
Chernobyl nuclear power plant
accident, 27–28, 28f
acute radiation syndrome after, 142–143
breast cancer incidence after, 27–28
carcinogenesis in f, 164–165
embryonic effects resulting from, 168
follow-up studies of, 164
leukemia incidence after, 27–28, 165
sarcophagus and, 28, 28f
thyroid cancer incidence after,
27–28, 164–165, 164f
worldwide effects of, 164
Children. see also Pediatric imaging
dose requirements for, 245–246
radiation sensitivity of, patient
education and, 9–10
technical exposure factors for, 194
Chromatid aberrations, 148–149
Chromatin, 103
Chromosome aberrations, 148–149
Chromosome breakage, 115
Chromosome translocations, 149
Chromosomes
DNA in, 90–91, 91f
effects of ionizing radiation on,
121–122
anomalies, 122
breaks, 121–122
fragments, 122
structural changes within nucleus,
122
Classical scattering. see Coherent
scattering
Clear lead-acrylic secondary protective
barrier, 302, 303f
Coherent scattering, 38–41
importance of, 41b
process of, 38–41, 41f
soft tissue interaction, 40t
Coincidence, between radiographic
beam and localizing light beam
of, 199
ColEfD. see Collective effective dose
Collective effective dose (ColEfD), 68,
68b
Collimation, in radiographic fog,
37–38, 39f
Collimators
light-localizing variable-aperture
rectangular, 196–197, 197f
in x-ray beam production, 36
Committed effective dose equivalent
(CEDE), 68
Communication, 8, 9f. see also Effective
communication
Compensating filters, 202–203
Compton scattered electron, 48–49
Compton scattered photon, 48
Compton scattering, 38–41
importance of, 41b
probability of, 41t, 43–44
process of, 38–41, 41f
soft tissue interaction, 40t
Computed radiography, 208–210,
209f
avoiding overexposure of patient,
211–212
kilovoltage in, 209
radiographic grids in, 209–210
x-ray beam collimation in, 209
Computed tomography (CT)
cardiovascular imaging, 262–271
contrast resolution, 269
ECG gated imaging, 265–269,
266b, 267f
heart anatomy and processes, 263,
264b
heart beat rate, 267–268
image noise, 271, 271t
patient radiation doses and
volume scanning, 270–271
phases, cardiac cycle, 265
radiation doses, 269–270, 270f
INDEX
395
Computed tomography (Continued)
spatial resolution, 268–269
temporal resolution, 268
defined, 253
Image Gently Campaign and, 11
patient dose management during,
247, 253–254
Alliance for Radiation Safety in
Pediatric Imaging and, 10–11
direct patient shielding in, 254
dose parameters for, 257–258,
257f, 258b
effective dose, 258–260, 259b,
259t
goal of, 260
helical/spiral, 254, 255f
pitch ratio, 254, 255f
reduction methods, 254–257,
255b, 255f
skin dose and dose distribution
concerns, 253–254, 254f
radiation exposure due to, 22t, 29,
29t, 253
radioisotopes in, 324–325, 325f
Computed tomography dose index
(CTDI), 257
Computer, digital imaging and,
206–207
Concise instructions, for effective
communication, 229, 229f
Console. see Control panel
Consumer-Patient Radiation Health
and Safety Act of 1981, 182
Consumer products, radiation
exposure due to, 24–25
Contamination, 336–337
internal, 115, 338
surface, 337
in urban area, cleanup of, 337
Contrast, radiographic, photoelectric
absorption on, 46–47
Contrast media, 47–48
Control-booth barrier, 302, 303f
Control monitor, 77
Control panel, 196
Control switch, fluoroscopic exposure,
217
Controlled areas, in x-ray suite
protection design calculation, 312
Cosmic radiation, 23–24
Coulomb (C), 11
Coulomb per kilogram (C/kg), 4, 64
Counseling, for pregnant personnel
protection, 298–299
Covalent cross-links, in DNA, 121,
121f
Crookes tube, 55–56
Crossover, 108
CT. see Computed tomography
CTDI. see Computed tomography dose
index
CumEfD limit. see Cumulative effective
dose (CumEfD) limit
Cumulative effective dose (CumEfD)
limit, 186, 295
Cumulative timer, 216
Cutie pie. see Ionization chamber-type
survey meter
Cytogenetic effects, 148–149
Cytogenetics, 148
Cytoplasm, 99–100, 100b
Cytoplasmic organelles, 100–102
centrosomes, 102, 102f
endoplasmic reticulum, 100
Golgi apparatus, 100
lysosomes, 101
mitochondria, 100–101
ribosomes, 102
D
Dally, Clarence Madison, 56, 57f
DAP. see Dose area product
Daughter radioactive isotope, 23
Death. see also Lethal dose
acute radiation lethality, 141
as cellular effect of irradiation
apoptosis, 127
instant death, 126
mitotic death, 127
reproductive death, 127
at Chernobyl accident, 27–28
in gastrointestinal syndrome,
141–142
in hematopoietic syndrome, 141
radiation equivalent doses causing,
10t
Decontamination, 337
Deletion, 122, 123f
Density
of Compton scattering, 41t, 48–49
of pair production, 41t
of photoelectric absorption, 41t, 44,
45f
radiographic, 45f
Deoxyribonucleic acid (DNA), 92–93
chromosomes and genes, 95–96
high-linear energy transfer radiation
damage to, 114–115, 114f
human genome, 96–97
ionizing radiation molecular effects
on, 119–121
covalent cross-links, 121, 121f
double-strand break, 119–120,
120f
mutation, 121, 121f
single-strand break, 119, 120f
as master chemical substance, 94
nitrogenous organic bases in, 93–94,
93f
structure of, 93f, 94–97
target theory and, 122–125, 126f
Dermatitis. see Radiodermatitis
Desquamation, 140f, 146
Diagnostic efficacy, 5–6, 6b, 6f
Diagnostic imaging professional,
radiation safety and, 3–4
Diagnostic-type protective tube
housing, 195–196, 196f
Diarrhea, radiation doses causing, 21t,
141
Digital breast tomosynthesis (DBT),
278–288, 279f, 280f
advantages, 283, 284f
angular scan range effects, 280–281
artifacts in, 285, 285f, 286f
image reconstruction, 281–283, 282f
imaging unit characteristics, 286,
287f, 287t
procedure, 286–288, 287b, 288f
properties, 286
summary, 289–290
Digital fluoroscopy, 217–219
last image hold feature for dose
reduction in, 218–219
pulsed progressive systems for dose
reduction in, 217–218
Digital imaging, repeats in, 295
Digital imaging equipment, radiation
safety features of, 206–212
computed radiography, 208–210,
209f
digital imaging, 207–208, 207b
digital processed radiography
modes, 206–207
digital radiography, 210
repeat rates and, 210–212, 211f
396
INDEX
Digital mammography, 278
Digital radiography, 210
Digital tomosynthesis, 276–277
Direct action, of ionizing radiation,
116, 117f
Direct radiation. see Primary radiation
Direct transmission, of x-ray photons,
37
Dirty bomb, 336–337. see also
Radiation emergencies
Disaccharides, 91–92, 91b
Discomfort, effective communication
for procedures causing, 229, 230f
Distance, radiation protection and, 7
for personnel exposure reduction,
300–301, 300f, 301b, 301f
Dizygotic twins, 108
DLP. see Dose length product
DNA. see Deoxyribonucleic acid
Dominant point mutations, 169
Dose, 20
absorbed, 4, 20, 35–36, 64–65, 64b,
65b, 212–213
bone marrow, 30, 30t, 238–239
collective effective, 68, 68b
committed effective dose equivalent
(CEDE), 68
effective, 66–67, 67b, 67t
entrance, 64
entrance skin exposure (ESE), 194
of diagnostic imaging procedure,
238
for medical radiation, 30t
equivalent. see Equivalent dose
(EqD)
fetal
determination of, 242–243, 243f,
244t, 245b, 246b, 246f
for medical radiation, 30t
genetically significant, 238
gonadal, 30t, 238, 247
lethal, 143–144
LD 10/30, LD 50/60, and LD
100/60, 144, 144t
LD 50/30, 143–144, 143f
leukemia and, 164
for lumbar spine examination, 67,
67t
maximum permissible, 59
for medical radiation, 30t
monitoring and reporting of, 12
Dose (Continued) Dose limits (Continued)
nominal risk of malignancy and,
162–163, 163f
nonoccupational, limits for, 190
occupational, limits for, 185b, 190, 191t
patient. see Patient dose; Personnel
dose, management during
diagnostic x-ray procedures
quantities and units in use today,
60–61
in roentgen, 58–59
skin, 238, 253–254
skin erythema, 57
threshold, 58–59
tolerance, 58–59
total effective dose equivalent
(TEDE), 68
Dose alerts, protocols for, 12
Dose area product (DAP), 64
Dose commitment, 25
Dose creep, 211–212
Dose distribution, 253–254, 254f
Dose effect relation, after acute
whole-body radiation, 338t
Dose length product (DLP), 257
Dose limits. see also Radiation
protection standards
organizations
action limits, 189
ALARA concept for, 181
model for, 181, 182f
Consumer-Patient Radiation
Health and Safety Act of 1981,
182
current radiation protection
philosophy, 183–185
effective dose limiting system, 183–
184, 184f
basis of, 175, 175f, 185
tissue weighting factor and, 185,
185b
underlying concept of radiation
protection, 185
for exposure to ionizing radiation,
173–193
nonoccupational, 190
occupational, 190
annual occupational effective dose
limit, 186
special limits for selected areas,
190
Radiation Control for Health and
Safety Act of 1968, 180–181
radiation hormesis and, 189–190
radiation-induced responses of
concern, 182–183, 182b
categories for, 182
changes in terminology, 182–183
radiation safety program,
179–180
risk and
embryo-fetus vulnerability, 185
occupational, 184–185
US regulatory agencies, 177–179,
178t
agreement states, 178
Environmental Protection
Agency (EPA), 179
Food and Drug Administration
(FDA), 179
Nuclear Regulatory Commission
(NRC), 177–178
Occupational Safety and Health
Administration (OSHA),
179
White Paper of FDA, 181–182
Dose parameters, 257–258
Dose rate constant, 327
Dose–response relationship, 154–157
curves, 154, 155f
linear nonthreshold curve,
154–155, 155f
linear-quadratic nonthreshold
curve, 155–156, 156f
linear threshold curve, 156–157,
156f
sigmoid threshold curve, 155f,
156–157
linear-quadratic, 115–116, 156f
risk models
for predicting cancer risk and
heritable damage, 155–156,
156f
for predicting high-dose cellular
response, 156–157, 156f
for predicting leukemia, breast
cancer, and heritable
damage, 156
selection, rationale for, 157
threshold and nonthreshold
relationships, 154–155, 155f