Chapter 1: Ionzing Radiation and Basic Principles of X-Rays Generation
How far away should the operation stand for safety when exposing x-rays?
6 ft.
What are the dimensions of the x-ray tube?
6 inches long, 1.5 inches in diameter
Photon
A discrete unit of energy
Electron
A negatively charged particle, which is a constituent of every neutral atom
Neutron
A particle that has no charge but mass. It is found in the nucleus of an atom.
Radionuclide
A radioactive substance.
What happens the electrons strike the target?
A transfer of energy from kinetic energy to x-ray photon and heat energy occurs creating the actual x-ray.
What is the hittorf-crookes tube and how does it work?
A vacuum tube with an electric current from a battery source in which Roentgen used to discover and describe x-rays. X-rays were named for 'x' in algebra as the unknown. The current created a glow which grew stronger when he was closer to the object which is used to describe the inverse square law. His tube had an anode and cathode end with a fixed electric current.
Who is given credit for suggesting the bisecting technique?
A. Cieszynski
Shell
AKA orbit. A prescribed path or ring which electrons travel around the nucleus of an atom.
What does the exposure button do?
Activated the high voltage circuit crossing from cathode to anode when the high voltage circuit is complete.
What is an Isotope?
An atom whose nucleus has the same number of protons but a different number of neutrons
In the x-ray tube, x-rays originate from:_____.
Anode
Atom
Basic unit of matter composed of a positively charged nucleus w/negatively charged electrons revolving around.
Bremsstrahlung
Braking radiation' the release of a photon of energy by a bombarding electron slowed and bent off course by atom
What is particulate radiation?
Consists of atoms or subatomic particles that have mass and travel at high speeds to transmit kinetic energy. Emitted from radioactive substances called radionuclide.
What is the focusing cup?
Directs the electrons from the cathode to the anode.
What is wavelength?
Distance from one crest to the next
Wavelength
Distance from the crest of one wave to the crest of the next wave. Wavelength is a measurement of energy.
Who was credited with taking the first intraoral radiograph?
Dr. Edmund C. Kells
Who first used x-rays useful in the dental field?
Dr. Otto Walkoff of a lower premolar.
The release of electrons from the hot tungsten filament at the cathode is called the _______.
Electron cloud or cathode ray.
What are some examples are particulate radiation?
Electrons (or beta particles Protons Neutrons Alpha particles
What is radiation?
Emission of energy through space or substance in the form of wave or particles
Who is given credit for developing the paralleling technique?
Franklin McCormack
Explain the similarities and differences of x-rays and gamma rays.
Gamma and x-rays have identical wavelengths. The difference is the for x-rays are electrons whereas the source for gamma rays originates from the nuclei of radioactive material.
What is electromagnetic spectrum?
Grouping of energy wave with common weightlessness and speed of waves. Radiation levels vary based on wavelength and frequency properties
What limits the mA setting?
Heat production. Any thing over 15 mA too many electrons would hit the target and produce too much heat for the machine to handle.
What is crest? Trough?
Height of the wave/depth of the wave
Why is tungsten used?
High melting point and low vapor pressure. The high atomic number makes it more dense and creates more efficient x-rays when electrons contact it.
What is a rare form of dental x-rays?
High speed electrons hit the nucleus of the tungsten atom and give up all its energy.
What are the 3 basic elements of the x-ray tubes?
High voltage to accelerate the electrons Source of electrons Target to stop the electrons
Collimator cutoff (cone cutting) is caused by: ______.
Improper beam film alingment
What does turning the x-ray machine on do?
It closes the filament circuit and heats the tungsten filament causing thermionic emission
What is ultrasonic radiation?
It is not part of the electromagnetic spectrum, nonionizing radiation with no effects on tissue.
What is ionizing radiation?
It takes a higher energy than that binding energy to knock an electron out of its shell. Low energy photons (UV light) can knock an outer electron. Ionizing radiations have a high energy that can knock electrons close to the nucleus out of orbit (x-rays and gamma rays and some particulate radiations._
What is the closest shell to the nucleus?
K then L, M, N, O
Which way does the electric current flow?
Negative to Positive
What is frequency?
Number of oscillations per unit of time
Why is the dental x-ray machine insufficient?
Only 1% of the energy is x-ray the rest is heat
What are x-rays?
Penetrating electromagnetic radiations having wavelengths shorter than those of visible light and that are produce by bombarding a metal w/ high speed electrons X-rays are energy waves with no mass and are part of a grouping called electromagnetic radiation
What is Ionization?
Process by which an electrically stable or neutral atom or molecule loses or gains electrons and thereby acquires a positive or negative charge Can be removed from atoms by heating or interaction with x-ray photons.
Radioactive
Process where certain unstable elements under spontaneous degeneration and produce hi-energy waves
What is the thermionic emission effect?
Production of free electrons by the passing of an electric current through a tungsten filament w/resultant heating of the filament The boiling off of electrons. As the machine heats up (mA increased) the more electrons are released from the filament to the target.
What describes radiation produced at high kilovoltage?
Short wavelengths of high frequency
What circuit is the tungsten filament connected to?
Step-down transformer circuit
Binding energy
The energy (expressed in electron volts) that binds the orbiting electrons around the nucleus of an atom
What is the binding energy?
The energy needed to hold an electron in its shell. The farther away from the nucleus the lower the bonding energy.
What are characteristic rays?
The entering high speed electron dislodges on orbiting electron when the entering electron possesses more energy than the orbiting one, forcing the dislodge electron to produce the x-ray and heat. Not as useful.
What are bremsstrahling rays?
The entering high speed electron is slowed down and bent off by the positive pull of the nucleus given off x-ray and heat energy.
What affects the step up transformer?
The kVp
What is the relationship between wavelength and frequency?
The longer the wave length the less there is to measure in a given time, therefore the frequency is smaller and not enough energy is released to penetrate matter. Vice versa the shorter the wavelength the higher the frequency the higher the penetrating power.
What is the difference between radiation and particulate radiation?
The moving particulate radiation alter the composition of the substances it strikes.
What is a cathode?
The negatively charged side of the dental x-ray tube. It contains a tungsten filament and the molybdenum focusing cup
What is duty rating?
The number of consecutive in a minute that a dental x-ray can be operated without overheating
What is the atomic mass?
The number of neutrons in a nucleus
What is the atomic number?
The number of protons in the nucleus of an atom.
What is duty cycle?
The number of seconds in a minute that a dental x-ray machine can be operated without overheating. (4)
What is the target aka focal spot of area?
The part of the anode that the high-speed electrons strike and that produces x-rays and heat. In dental x-ray tubes, the target is usually made of tungsten.
What is an anode?
The positively charged side of the dental x-ray tube. It contains the tungsten target at which the electrons are aimed and from which x-rays are emitted
Nucleus
The positively charged, relatively heavy inner core of an atom
What is radioactive material?
The process where unstable elements undergo spontaneous degeneration and produce high energy waves called gamma rays or particulate radiation. Think cancer patients, they will receive radioactive material in order to degenerate their tumor. Patients in dental office receive x-rays that are not radioactive.
What is a molecule?
The smallest particle of a substance that retains the properties of the substance.
What is a cathode ray?
The stream of electrons in the x-ray tube traveling from filament to target.
What is the source of electrons in the x-ray machine?
The tungsten filament
If a radiograph is described as 'underpenetrated' then the error must be____.
Too little kVp
What are isotopes used for?
Tracer elements in diagnosis and maintenance of diseases
The target material (in the anode) for diagnostic tubes is: ______.
Tungsten
What is the significance of the copper stem?
Tungsten has a low degree of thermal conductivity so the copper stem allow the heat to dissipate into the machine itself.
What is the effect of electromagnetic radiation on living organisms?
Varies depending on wavelength. The higher the penetrating power the more the radiation can ionize and negatively affect human tissue.
Electromagnetic radiation
Waves of energy (angstrom) or individual units of energy (ergs)
Ionization is ____.
When a atom loses an electron
Ionization occurs ______.
When atoms lose electrons. They become deficient in negative charges and therefore behave as positively atoms.
Who discovered x-rays and when?
Wilhelm Conrad Roentgen, 1895
What are the basic observations about x-rays?
X-rays are produced by a machine that uses electricity as a source of energy. X-ray invisible X-rays travel in a straight line X-rays can penetrate opaque objects X-rays can affect photographic emulsion to produce a visible image (they show latent images) X-rays can adversely affect human tissue
Select the correct statement. 1) X-rays can be focused to a point 2) X-rays cannot be focused to a point 3) X-rays do not always travel in straight lines 4) X-rays have a positive charge
X-rays can be focused to a point
What is the wavelength of x-rays?
X-rays have short wavelength with higher frequency and penetrating power. They are measured in angstrom units.
The quality of x-rays photons produced is determined by the ____ setting.
kVp
The quantity of x-ray photons produced is determined by the ____ setting.
mA
