ARRT Radiography Exam (Mosby Review)

Ionizing Radiation

radiation that is able to remove electrons from an atom through ionization

Somatic effects

refers to the effects of radiation to the body being irradiated

Genetic Effects

refers to effects of radiation to a germ cell's genetic code; effects the next generation

natural background radiation

radiation contained in the unpolluted environment

Artificially produced radiation

also called man-made radiation (e.g., medical x-rays)

Primary radiation

radiation exiting the x-ray tube

Exit radiation (remnant radiation; image-producing radiation)

x-rays that emerge from the patient and strike the image receptor

attenuation

absorption and scatter of the x-ray beam as it passes through the patient

heterogenous beam

x-ray beam that has photons of many different energies

photoelectric effect

absorption of x-ray photons in the atoms of the body

compton effect

scatter of x-ray photons from the atoms of the body

air kerma

unit of exposure

gray

unit of absorbed dose, measured in joules per kilogram (J/kg); 1 Gy = 1 J/kg

gray(a)

unit of radiation absorbed in air

gray(t)

unit of radiation absorbed in tissue

sievert

unit of effective dose or unit of equivalent dose

becquerel

unit of activity

international commission on Radiologic Protection (ICRP)

organizaiton that

uncontrolled area

general public area, like waiting room or stairways

controlled area

occupied by people trained in radiation safety and wear radiation badges/monitors

x-ray tube leakage may not exceed what?

1mGy(a) per hour at a distance of 1 meter from the housing

minimum lead equivalent for fluoro curtain

0.25mm

minimum lead equivalent for bucky slot shield

0.25mm

NAS or NRC-BEIR

National Academy of Sciences/National Research Counsel on the Biological Effects of Ionizing Radiation

studies biologic effects of ionizing radiation and publishes the data

NCRP

National Counsel on Radiation Protection

publishes radiation protection guidelines for the US

NRC

Nuclear Regulatory Commission

enforces radiation protection standards at the federal level

NCRP Report #102

makes recommendations on equipment design and protection regarding lead shielding and fluoro and mobile exposure rates

NCRP Report #116

makes recommendations pertaining to risk-benefit analysis of radiation exposure; states genetic and somatic effects need to be kept to a minimum; makes annual dose limits

NCRP #160

addresses radiation exposure from all sources to people in the US

effective dose limit

upper boundary dose that can be absorbed (either in a single exposure or annually) with negligible risk of genetic or somatic effects to the individual

cumulative effective dose

lifetime occupational exposure must not exceed radiographer's age x 10 mSv

equivalent dose

equal to the absorbed dose multiplied by the radiation weighting factor

equivalent dose limit

upper boundary dose that can be absorbed (either in a single exposure or annually) with negligible risk of deterministic effect

Dose Area Product (DAP)

total air kerma striking the patient

probabilistic effects (stochastic)

randomly occurring effects of radiation; probability is proportional to the dose (increased dose = increased probability)

Deterministic Effects

radiation effects that become more severe at higher levels of radiation exposure; do not occur below a certain threshold

GSD (Genetically Significant Dose)

average annual gonadal dose of radiation to individuals of childbearing age; addresses the relationship of gonadal doses to individuals versus an entire population and the overall effects

Linear Energy Transfer (LET)

amount of energy deposited by radiation per unit length of tissue

Relative biologic effectiveness (RBE)

ability to produce biologic damage; varies with the LET

Direct effect

occurs when radiation directly strikes DNA in the cellular nucleus

Indirect effect

occurs when radiation strikes the water molecules in the cytoplasm of the cell

Radiolysis of water

occurs as radiation energy is deposited in the water of the cell; the result of radiolysis is an ion pair in the cell: a positively charged water molecule (HOH+) and a free electron

Mutation

erroneous information passed to subsequent generations via cell division

Law of Bergonie and Tribondeau

ells are most sensitive to radiation when they are immature, undifferentiated, and rapidly dividing

Early somatic effects of radiation

hematopoietic syndrome; gastrointestinal (GI) syndrome; central nervous system syndrome

Late somatic effects of radiation

carcinogenesis; cataractogenesis; embryologic effects; thyroid dysfunction; life span shortening

Cardinal principles of radiation protection

time, distance, shielding

what is the best protection against radiation exposure?

distance

Mean marrow dose

average dose to bone marrow

mass

the amount of matter in an object; generally considered the same as weight

energy

the ability to do work

Potential energy

energy of position

Kinetic energy

energy of motion

chemical energy

energy from a chemical reaction

Electrical energy

result of the movement of electrons

Thermal energy

heat energy resulting from the movement of atoms or molecules

Nuclear energy

energy from the nucleus of an atom

Electromagnetic energy

energy that is emitted and transferred through matter

Velocity (speed)

how fast an object is moving

Acceleration

the rate of change of speed per unit of time

work

force applied on an object over a distance

power

the rate of doing work (measured in watts)

Atomic nucleus

contains protons (positive charges) and neutrons (no charge); contains most of the mass of an atom

Atomic mass

number of protons plus number of neutrons; represented by the letter A

Electron shells

contain orbital electrons (negative charges); electron shells represented by the letters K, L, M, N, O, P, and Q; in a stable atom the number of electrons and protons is equal

Atomic number of an atom

equals the number of protons in the nucleus; represented by the letter Z; the atomic number determines the chemical element; all chemical elements are represented in the periodic table of the elements

Isotopes

atoms with the same number of protons but with a different number of neutrons

Electron-binding energy

force that holds electrons in orbit around the nucleus

Octet rule

the outer shell of an atom may not contain more than eight electrons

Particulate radiation

alpha particles (helium nucleus: two protons and two neutrons); beta particles (electron-like particles emitted from the nucleus of a radioactive atom)

Photon

the smallest amount of any type of electromagnetic radiation; also considered a bundle of energy called a quantum; travels at the speed of light; travels in waves in a straight path

Sine waves

waves of electromagnetic radiation; wave height is called amplitude; distance between the peaks of the waves is called wavelength; as photon wavelength decreases, photon energy increases

Frequency

number of wavelengths passing a given point per unit time; measured in hertz (Hz)

Speed of travel

electromagnetic radiation travels at the speed of light (186,000 miles per second); travel at the speed of light is constant regardless of wavelength or frequency; wavelength and frequency of electromagnetic radiation are inversely proportional

gamma rays

electromagnetic rays produced by the nucleus of radioactive atoms

wave particle duality

the concept that although xray photons exist as waves, they exist with properties of particles

attenuation

partial absorption of the energy of an xray beam as it traverses an object

inverse square law

intensity of an xray beam is inversely proportional to the square of the distance between the source of xrays and the object

law of conservation of matter

matter cannot be created or destroyed; only changed in form

law of conservation of energy

energy cannot be created or destroyed; only changed in form

electrostatics

stationary electric charges (static electricity)

electrification

movement of electrons between objects

law of electrostatics

unlike charges attract and like charges repel; electrostatic charges reside on the outer surface of a conductor and are concentrated at the area of the greatest curvature; only negative charges move

methods of electrification

friction, contact, induction

conductor

material that allows the free flow of electrons

insulator

objects that prohibit the flow of electrons

electric current

the movement of electrons along a conductor or pathway; measured in amperes

electromotive force (EMF)

measured in volts; the force with which electrons move in an electric circuit

electrodynamics

electric charges in motion

semiconductor

material that may act as an insulator or conductor depending on conditions

electric resistance

inhibits the flow of electrons; measured in ohms

electric circuits

path along which electrons flow; may be wired as series circuits or parallel circuits

alternating current

current of electrons oscillate back and forth

direct current

electrons flow in one direction

sine waves

representation of electron flow as alternating current

magnetic field

energy field surrounding an electric charge in motion; can magnetize a material if placed in the magnetic field

magnetic poles

every magnetic has a north and south pole

laws of magnetic

like poles repel; unlike poles retract; governed by inverse square law

electromagnetism

movement of electrons in a conductor produces a magnetic field around the conductor

self induction

opposing voltage created in an inductor by passing alternating current through it