LO 1 Flashcards
_________ discovered x-rays in 1895
Wilhelm Conrad Roentgen
What are the 7 reasons to take radiographs?
- Detect - lesions
- Confirm or classify - suspected disease
- Localize - lesions or foreign objects
- Provide - information during procedures
- Evaluate - growth and development
- Illustrate - changes to secondary caries, periodontal disease, trauma
- Document - current condition of the patient
Define x-ray
A beam of energy that has the power to penetrate substances and record image shadows on photographic film
Define radiograph
Image produced on a receptor (radiation sensitive film, phosphor plate, or digital sensor) by exposure to ionizing radiation. A 2d representation of 3d object
Define image receptor
A recording medium (e.g. x-ray film, phosphor plate, digital sensor)
Define dental imaging
The creation of a digital, print, or film representation of atomic structure for the purpose of diagnosis.
_________ is one of the most significant advances in dentistry, allowing for instant transmission of images, reducing patient exposure, and improving diagnostic potential.
Digital imaging
Everything in the world is composed of these 2 things
- Matter - has mass
- Energy - has no mass
_______ makes electrons chemically stable but electrically unstable
Ionization
Most of the atom is _______
Empty space
Electrons travel around the nucleus in well-defined paths known as ______ or ______
Orbits or shells
The shell located closest to the nucleus has the ______ binding energy level
Highest
An atom contains a maximum of ___ shells starting with ____
7;K
Electrons are maintained in their orbits by ________ force
Electrostatic force (binding energy)
__________ is determined by the distance between the nucleus and the orbiting electron
Binding energy
In what 2 ways are molecules formed?
- Transfer of electrons - Ionic bonds
- Sharing of outer most electrons - covalent bonds
The energy required to remove an electron from its orbital shell must exceed the _______
Binding energy
Easier to dislodge M shell than K shell
Atoms are electrically neutral when ______
They have the same number of protons and electrons
This is the typical state
When does an atom have a positive charge? A negative charge?
- Positive when loses an electron
- Negative when gains an electron
Describe the ion pair
The atom that loses electron becomes the positive ion and the ejected electron becomes the negative ion. The pair rests with other ions until electrically stable atoms are formed
What are the 2 types of radiation?
- Ionizing radiation such as x-radiation
- Non-ionizing radiation such as light
Radiation is the emission and propogation of energy through a space or a substance in the form of waves or particles, while radioactivity is _________
The process by which unstable atoms or elements undergo spontaneous decay
What is ionizing radiation?
Radiation capable of producing ions by removing or adding and electron to an atom
_______ and _______ are the 2 classifications of ionizing radiation
- Particulate radiation
- Electromagnetic radiation
X-radiation acts as both ______ and ______ radiation
- Particulate
- Electromagnetic
Describe particulate radiation
- Particles of matter that posses mass and travel at high speeds
- Can be electrons (beta particles or cathode rays), alpha particles, protons, or neutrons
- Transmit their kinetic energy b/c fast moving small masses
Electromagnetic radiation moves as a _______
Wave
In electromagnetic radiation, oscillating electric and magnetic fields are positioned _______ to one another
At right angles
Is electromagnetic radiation always man-made?
No, cosmic rays, gamma rays, ultraviolet light, and visible light are examples of naturally occuring electromagnetic radiation.
Only ________ radiations are capable of ionization
High-energy
What are the 4 charactersistics of photons?
- No mass
- No charge
- Travel at the speed of light
- Travel in a straight line
What are the 3 characteristics of electromagnetic radiation waves?
- Velocity - speed of the wave (always speed of light in the case of electromagnetic radiation)
- Wavelength - distance between crests
- Frequency - the number of wavelengths that pass a certain point in a given time
Low energy radiation has _______ frequency and ________ wavelengths
Low; long
High energy radiation has ________ frequency and ________ wavelengths
High; short
The 3 main parts of an x-ray machine are ________
- Control panel
- Extension arm
- Tube head
What is contained on the control panel?
- On-off switch
- Indicator light
- Control devices (time, kilovoltage, miliamperage)
- Plugged into electrical outlet
What does the extension arm of the x-ray machine do?
- Suspends the x-ray tube head
- Houses electrical wires
- Allows for movement and positioning of the tubehead
The ______ in the x-ray tube head permits the exit of x-rays, seals the oil, filters the x-ray beam
Tubehead seal
The heart of the generating system in the x-ray tube head is _______
x-ray tube
________ alters voltage if incoming electricity
Transformer
________ surrounds x-ray tube and transformers, prevents overheating
Insulating oil
_______ filters out non-penetrating, longer wavelengths x-rays
Aluminium disks
___________ restricts the size of the x-ray beam
Lead collimator
________ aims and shapes the x-ray beam
Position-indicating device
What comprises the x-ray tube?
Leaded glass housing with a “window”, cathode, anode
Why does the x-ray tube have a leaded glass housing?
Prevents the x-rays from escaping in all directions
Describe the purpose of the cathode
- Consists of tungsten wire and molybdenum cup
- Supplies electrons needed to generate x-rays (boiled off the tungsten filiment)
- Molybdenum cup focuses electrons toward tungsten target (anode)
- Electrons are accelerated toward the positive anode
Describe the purpose of the anode
- The positive electrode
- Tungsten plate in solid copper rod
- Converts electrons into. X-ray photons
- Tungsten target is focal spot
- Copper step dissipates heat away from tungsten target
_______ is the measurement of the number of electrons moving through a conductor
Amperage (current)
measured in amperes (A) or miliamperes (mA)
_________ is the measurement of electrical force that causes electrons to move from a negative pole to a positive one
Voltage
Measured in volts (V) or kilovolts (kV)
What are the 2 circuits in x-ray machines and what are the rough volts used?
- Filiment circuit (low voltage circuit) - uses 3-5 volts and is controlled by the milliamperage setting
- High-voltage circuit - uses 65,000 to 100,000 volts. Controlled by the kilovoltage settings
What are the 3 transformers in an x-ray machine?
- Step down transformer- decreases the incoming voltage from 110 or 220 to 3-5
- Step up transformer - increases incoming voltage to 65,000 to 100,000
- Autotransformer - corrects for minor fluctuations in current
_______ is the release of electrons into an electron cloud
Thermionic emission
What happens when the high-voltage circuit is activated?
The electrons are pushed high speed toward the tungsten target
____% of energy is converted into x-rays and ____% is lost as heat
1;99
What are the 2 types of radiation created at the anode?
- General (breaking/brehmstrahlung)
- Characteristic radiation
Describe general radiation
- The speed of the electrons are slowed because of their attraction to the nuclei of target atoms -results in low energy photons
- Going from high to low energy is why it is also called breaking radiation
- 70% of energy produced at anode
- A single electron that keeps missing nuclei will continue interacting with atoms creating low-energy photons until it loses kinetic motion - general radiation consists of many wavelengths
What happens if an electron hits the nucleus of an atom on the tungsten target?
All of its energy is converted into a high-energy x-ray photon
Describe characteristic radiation
- Occurs when electron dislodges an inner shell electron, causing ionization of the atom
- It is ideal, what makes radiographs possible
- Bombarding electron loses its charge and the ejected electron becomes bombarding electron
- Remaining electrons rearrange to fill gap
Characteristic radiation only occurs at _____ kVp
70 - this is required to dislodge a k-shell electron
What types of radiation does the patient experience?
- Primary radiation - what exits the tube head
- Secondary radiation - radiation absorbed in the body
- Scatter radiation - radiation enter matter and is deflected by its interaction with matter
What are the 2 types of scatter radiation?
- Compton scatter - photon collides with outer shell electron and gives up some of its energy, photon continues on at lower energy, includes ionization (62% of energy)
- Coherent scatter - x-ray photon has its path altered by matter (8%)
How often is there no interaction with matter from photons leaving the x-ray machine?
Less than 1%
Roughly 30% of the time x-ray photons are completely absorbed withing matter or tissues, resulting in the photoelectric effect. Describe this effect
An x-ray collides with a tightly bound electron and transfers all energy from photon to atom
