week 6 - 8 review (exam) Flashcards
Xray tube charges
Anode - target side of x-ray tube (+)
cathode - filament side of X-ray tube (-)
electricity
energy used to make x-rays
Electrical current
flow of electrons through a conductor
Amperage and miliaperes (general)
Measurement of the number of electrons moving through a conductor
mili - increase of decrease # of electrons passing through cathode
Voltage and kilovolts (general)
measurements of electrical force that causes electrons to move from negative pole to a positive pole
Kili - control the current passing from cathode to anode
Types of transformers (3 types)
- Step-down transformer (ON button) - 3-5 voltage to heat up tungsten and forms electron could
- step-up transformer (connected to exposure button) - 55 k - 100k high voltage and difference between low and high volts free the electrons from the filament
- autotransformers - corrects for minor fluctuations in current
Filtration
- Aluminum filtration - removes long wavelength photons
- total filtration (glass tube, insulating oil, barrier)
- lead collimator - allows the shape and size of beam to be controlled (rectangular 50% less than circular)
Absorption radiation (explained)
radiation energy is absorbed by photons colliding with electrons of the atoms of an absorbing material
- higher the atomic weight, better energy absorption (lead)
3 ways x-ray photons can be absorbed
- pass through patient and expose film
- absorbed by patient - never reaches film
- x-ray photon may be scattered onto the fly or ways from film (film fogging)
photoelectric absorption
total absorption of X-ray photon energy (ejected electron is called photoelectron)
Compton absorption
Partial absorption of x-ray photon energy (scattered, longer wave length, ejected orbital electron (Compton electron)
Thompson/coherent scattering
photon of scattered radiation, no loss of energy just different direction
Quality vs quantity
quality - penetrating ability
quantity - amount
Controls that directly influences with quant and qual
exposure time, mA, kVp, PID
things that will indirectly influence the settings choose on X-ray unit
film speed/imaging sensor plate, film processing, patient size
Amperage (in detail)
Unit of quality of electric current, increase amps results in increase in # of electrons produced in cathode
Miliapere (in detail) mA
1/1000 ampere, only small current used in dental, total # of x-rays produced depends on mA exposure time
(directly influences # of electrons striking target - # produced)
Voltage (in detail)
electrical pressure, amount will determine the speed of electrons which gives energy (penetrating power)
kilovolt
1 kVp = 1000 volts
mA rule of thumb (thermionic emission)
directly influences # of electrons striking target, hence # of photons produced
increased mA: 10 to 25 = 30% more radiation
Decrease mA: 15 to 10 = 30% less radiation
Time influence
(length of time unit produced X-rays - direct prop)
longer time = more x-rays, less time = fewer x-rays
Double time = 2x rad
half time = 50% less rad
kVp
only component that will influence penetrating ability of the beam of radiation Directly influences the speed electrons impact target, thus the efficiency of the x-ray proton
- 15 kVp increase - increase intensity by 2x
- 15 kVp decrease - decrease intensity by 50%
Inverse square law (PID)
the intensity of the radiation is inversely proportional to the square of the distance
- 8 in to 16 in reduced intensity to 1/4 value at 8
- 16 in to 8 in increased intensity to 4x value at 16 in
Electron binding energy
- Electrons in orbital (negative charge) are attracted to protons (positive charge) in nucleolus
- Further away from nucleolus, less binding energy, easier to remove from orbital
- Near nucleolus, greater binding energy, harder to remove form orbital
Radiation atom
large, lots of electrons, easy to steal from outer shell
○ Tungsten, lots of electrons - requires less energy to remove them
Ionization
- Radiation can change an atom (removal of electrons)
- Electrically neutral - same number of electrons as we do protons
If electrons are pulled away ends up an ion
- Electrically neutral - same number of electrons as we do protons
Radiation
the emission and propagation of energy through a space of substance in the form of waves or particles
Radioactivity
the process by which certain unstable atoms or elements undergo spontaneous disintegration, or decay, in effort to attain a more balanced nuclear state (energy is given off as the nuclei disintegrates)
what is particulate radiation
posses mass and travel in straight lines at high speeds
what is electromagnetic radiation
is the propagation of wavelike energy without mass through space or matter
Particulate radiation (alpha and beta)
- alpha: positive helium atoms as a result of radioactive decay from radioactive element (two protons and two neutrons)
○ Lower penetrating power (a sheet of paper - deadly if ingested or inhaled) - Beta: similar to electrons, penetrate about 1.5 cm into skin
Common characteristics of all energies on spectrum (electro)
- Have no mass or weight, no electrical charge, travel at the speed of light, travel as a wave
- Different measurable energies (frequencies and wave lengths)
- Ionizing - high-energy radiations (cosmic rays, gamma rays, and X-rays) capable of ionization
Photons
- Bundles of energy that move in wave pattern at the speed of light
- Waves are characterized by wavelength and frequency that correlates with the energy the photon has
wave concept
- Wavelength is the distance between the crest (peak) of one wave and the crest of the next
- Shorter, higher frequency waves have stronger penetration power
X-radiation, X-rays, X-ray photons (dental radiation)
- X-radiation: High-energy, ionizing electromagnetic radiation
- X-rays: weightless bundles of energy without an electrical charge that travel in waves with a specific frequency at the speed of light
- X-ray photons: interact with the materials they penetrate and cause ionization
Characteristic production of radiation
- E- displaces an electron, another electron is attached to the empty spot, radiation is produces
- Minor source of dental radiation
- Energy of radiation is equal to the energy difference between one electron jumping into the empty space
Bremsstrahlung production of radiation
- Breaking action of a near miss: (most dental radiation), some radiation is created with a direct hit to the nucleus
- Many different energy levels
- Mostly used in X-rays
