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117 Cards in this Set
- Front
- Back
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What is radiation
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The emission and propagation of energy through space in the form of waves or particles
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Who was Wilhelm C. Roentgen
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father of diagnostic radiology
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Who was Otto Walkhoff
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first person to take a dental radiograph
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Who was Edmond Kells
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first dentist in the United States to take a radiograph
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Who was William Rollins
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first person to develop a facsimile of the X-ray machine, but that X-ray machine had no shielding, it had no protection, it had wires sticking all over the place, sparks were coming out of all over the place.
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Who was W.D. Coolige?
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Developed the hot filament tube
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Molecules
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smallest particle of a substance that retains the property of the substance
Ex: H2O, Sodium Chloride |
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Atom
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basic unit of matter
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Neutral atom
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the number of protons equals the number of electrons
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Which electrons have the strongest binding energy?
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Electrons closest to the nucleus
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atomic number
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the number of protons.
Z |
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Z
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atomic number
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Atomic mass
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the mass of protons and neutrons
A |
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A
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Atomic mass
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Ionization
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when a neutral atom loses one of its electrons.
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Electromagnetic radiation
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is the movement of energy through space as a combination of electric and magnetic fields
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electromagnetic spectrum
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a grouping of waves
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What commonalities is the electromagnetic spectrum grouping based on?
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Speed of travel
Weightlessness |
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What differences is the electromagnetic spectrum grouping based on?
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Wavelength
Frequency Penetrating ability |
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Wavelength
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the distance from the crest or top of one wave to the other.
The shorter the wavelength, the more energy and more penetrating the wavelength of energy is. |
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Penetrating ability
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The shorter the wavelength, the more energy and more penetrating the wavelength of energy is.
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Frequency
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the amount of waves in a certain period of time or space
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What are the properties of electromagnetic radiation
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No mass
Neutral polarity Travels at the speed of light Propagates an electric field at right angles to their path of travel |
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Properties of Short Wave Radiation like X-Radiation
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Odorless
Tasteless Invisible Travels in straight lines Travels at the speed of light Ionize atoms Produced by electrical current Penetrates opaque tissues and structures Can effect living tissue Can effect a photographic emulsion |
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Anode
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Positive part of the X-ray tube
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Cathode
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Negative part of the X-ray tube
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Primary Radiation
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Radiation coming out of the X-ray tube before hitting any object
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Thermionic emission effect
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Heat induced emission of electrons from a hot cathode, into a vacuum
Electrical current heats up the tungsten filament and boils off electrons |
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Filament circuit
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Low tension circuit
Step-down transformer taking 110V of electricity and converting it to 2-5V to heat the tungsten filament and create thermionic emission |
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High tension circuit
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Completed when you activate the button on the X-ray. Causes the anode to become positive, allowing the electrons to shoot across and hit the tungsten target
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What is the role of the copper sleeve?
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Used to dissipate the heat generated from the electrons striking the anode tungsten target
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What percentage of the energy is radiation?
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Only 1% is energy, 99% is heat
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Rare Occurrence X-ray produced
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Electron is attracted to the nucleus
Electron Hits the nucleus Electron gives up all of its energy No radiation is produced |
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Bremsstrahlung X-ray produced
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High speed electron hits tungsten target
Once in inner shell, electron is veered off course and leaves atom in the form of radiation and attacks another atom releasing more radiation The amount of radiation that comes out each successive BR is less and less |
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Characteristic X-ray produced
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Incoming electron is attracted to the nucleus and hits an inner shell electron and knocks it out of its shell
Electrons from the outer shells cascade in to fill the spot Knocking the electron produces radiation |
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What type of X-ray produced is the most common?
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Bremsstrahlung Radiation
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How can you shorten the exposure time?
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Have higher mA so more electrons are boiled off and available to be fired
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What is the limiting factor for the amount of mA you can use?
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The amount of heat produced
Higher mA causes more electrons to produce more heat |
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What occurs if you increase kV?
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Increase the speed of electrons therefore more penetrating short wavelengths
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How can you increase the penetrating ability of X-rays
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Increase the speed of electrons by increasing the kV
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What is the quality of X-rays dependent on?
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The amount of penetrating short waves available which is controlled by the speed of electrons which is controlled by increasing kV
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What is the quantity of X-rays dependent on?
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Dependent on The amount of X-rays produced which is controlled by the mA.
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Secondary Radiation
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AKA Scatter Radiation
Radiation that occurs after you hit the patient with the primary radiation |
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How can you decrease the divergence of X-rays
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By having a longer PID
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Which X-rays are the most parallel?
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The rays closest to the central rays
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What is the purpose of the aluminum filter
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TO remove the long wavelength radiation being produced
It protects the patient from receiving unnecessary radiation |
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What amount of filtration is necessary if the machine is operating at less than 70kVp?
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1.5mm of filtration is necessary
If operating at 70kVp or higher, need 2.5mm of filtration |
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What amount of filtration is necessary if the machine is operating at or more than 70kVp?
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2.5mm of total filtration is necessary
If operating at less than 70kVp, then you need 1.5mm of fiiltration |
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What types of filtration does the X_ray machine have?
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Inherent filtration (glass and oil)
Added filtration (aluminum disk) |
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Diaphragm
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Collimating device that Absorbs all radiation to ensure that the X-rays coming out do not diverge
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What is the purpose of a PID
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Collimation
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Half Value Layer
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Thickness of aluminum that will reduce the amount of radiation by half
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What is beam intensity affected by?
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Affected by kVp, mA, exposure time and Focal film distance (FFD)
Intensity = (kVp) x (mA) Increase kVP --> Increase Intensity Increase mA --> Increase Intensity Increase exposure time --> Increase Intensity Increase FFD --> Decrease Intensity by 1/(x^2) |
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What happens if the FFD increases?
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Intensity of the beam decreases because the divergence of the beam produces a larger field size
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What are characteristics of an acceptable radiograph
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Detail sharpness
Minimum amount of enlargement and distortion Proper degree of density and contrast |
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Film Density
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Degree of blackness on a film
Determined by the relative transmissions of the X-ray through parts of the object and absorption of the ex-rays in the film |
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Film Contrast
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Difference in the degrees of blackness on the film between adjacent area
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How do you decrease film density?
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If the film is too dark, that means there is too much penetration
Therefore decrease kVp or decrease exposure time or decrease mA |
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What control on the machine determines contrast of the film?
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Only kVp controls contrast of the film
Increase kVp to decrease contrast |
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What is the object contrast determined by?
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Transmission of X-rays through an object
And the objects density |
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What is the film contrast determined by?
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Absorption of x-rays in film emulsion
Properties of the film Intensifying screens Film processing Viewing conditions |
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Image Detail
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Visual quality of a radiograph that depends on definition or sharpness
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Umbra
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The sharp areas of a film
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Penumbra
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Unsharpness or blurring that surrounds the edge of a radiographic image
Keep penumbra small |
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How do you keep Penumbra small?
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By a small focal spot
Angulation of the target Increased FFD Decreased OFD |
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What is the major factor in getting the sharpest radiograph image
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Using a small focal spot
There is a limiting factor of heat produced |
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FFD
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Focal Film Distance
Distance from the focal spot to the film The longer the distance the more parallel the rays are going to be, the less magnification of the image |
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OFD
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Distance of the film to the object being radiographed
Decrease OFD to decrease penumbra |
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Inverse Square Law
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The intensity of radiation is inversely proportional to the square of the distance
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How many impulses of radiation do you have in 1sec?
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60 impulses/sec
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Effective focal spot
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Angled of the target at 20* to make it smaller than the actual focal spot creating a sharper image since decreasing the actual focal spot would increase heat production
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Intensity
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Product of the quality and quantity of the mean per unit of area per unit of exposure time
Affected by kVp, mA, exposure time and FFD |
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What occurs to the intensity if you increase the FFD by a factor of 2
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You decrease intensity by a factor of 1/4
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What emulsion is on the film?
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Silver bromide (halide) emulsion
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Orientation dot
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Dot on the outside of the intraoral film indicating placement of film towards to source of radiation
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Attenuation
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Lead foil backing of intraoral film absorbs the unnecessary unused radiation
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What is the purpose of the Lead Foil Backing in Intraoral film?
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Two purposes
Main purpose is to absorb the unused radiation Also protects the film from backscatter radiation from secondary radiation |
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Size 0 Film
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Pediatric Film
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Size 1 Film
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Narrow Anterior Film
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Size 2 Film
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Standard Periapical Film
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Size 4 Film
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Occlusal film
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Size 3 Film
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Bitewing film
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What is the advantage of using faster film?
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Less radiation to the patient
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What is the main factor determining film speed?
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Size of the sliver halide crystals
The larger the silver halide crystals, the more sensitive the film |
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Film Fog
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When any part of the film is darkened by sources other than primary radiation causing degradation of the film
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What happens if your duplicating film comes out too light?
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Decrease exposure time
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What are the possibilites that can occur during photon interaction with the patient?
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No Interaction - photon goes through the atom and doesnt scatter or cause ionization
Thompson Scatter - (Coherent/unmodified scatter) Photoelectric effect - causes ionization Compton effect - causes ionization |
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What is the advantage of using faster film?
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Less radiation to the patient
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What is the main factor determining film speed?
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Size of the sliver halide crystals
The larger the silver halide crystals, the more sensitive the film |
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What is the advantage of using faster film?
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Less radiation to the patient
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Film Fog
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When any part of the film is darkened by sources other than primary radiation causing degradation of the film
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What happens if your duplicating film comes out too light?
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Decrease exposure time
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What is the main factor determining film speed?
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Size of the sliver halide crystals
The larger the silver halide crystals, the more sensitive the film |
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What are the possibilites that can occur during photon interaction with the patient?
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No Interaction - photon goes through the atom and doesnt scatter or cause ionization
Thompson Scatter - (Coherent/unmodified scatter) Photoelectric effect - causes ionization Compton effect - causes ionization |
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Film Fog
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When any part of the film is darkened by sources other than primary radiation causing degradation of the film
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What happens if your duplicating film comes out too light?
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Decrease exposure time
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What are the possibilites that can occur during photon interaction with the patient?
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No Interaction - photon goes through the atom and doesnt scatter or cause ionization
Thompson Scatter - (Coherent/unmodified scatter) Photoelectric effect - causes ionization Compton effect - causes ionization |
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What is the advantage of using faster film?
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Less radiation to the patient
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What is the main factor determining film speed?
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Size of the sliver halide crystals
The larger the silver halide crystals, the more sensitive the film |
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Film Fog
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When any part of the film is darkened by sources other than primary radiation causing degradation of the film
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What happens if your duplicating film comes out too light?
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Decrease exposure time
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What are the possibilities that can occur during photon interaction with the patient?
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No Interaction - photon goes through the atom and doesnt scatter or cause ionization
Thompson Scatter - (Coherent/unmodified scatter) Photoelectric effect - causes ionization Compton effect - causes ionization |
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Thompson scatter or coherent scatter
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Entry of a photon of an X-ray, which has very low energy.
It gives up some of its energy to the electron electron becomes excited, but the electron does not leave the atom. There is no ionization of the atom Some scatter radiation given off |
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Photoelectric effect
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Entry of photon of X-ray
Dislodges inner electron Inner electron leaves No scatter Just ionization |
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Compton effect
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Most predominate interaction
Entry of photon of X-ray Completely knocks out outer electron You get ionization of atom but there is excess energy which gives scatter radition |
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Exposure
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A measure of the ionization in air produced by X-radiation or gamma radiation
1coulomb/kg = 3876R |
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Dose
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Amount of energy absorbed per unit mass of tissue at a particular site
Measured in RAD (radiation absorbed dose) |
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Scientific notation of Units of Radiation Measurement
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R Coloumbs (1C = 3876R)
RAD Gray (1gray = 100rad) REM Sievert (1sv = 100rem) |
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Dose Response Curve
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Illustrates the possible biologic responses to harmful agents such as ionizing radiation
Low-dose ionizating radiation is a linear, non-threshold relationship |
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Linear Relationship - Dose Response Curve
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Every time we give the patient a dose of radiation, there is some kind of response.
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Non-threshold relationship - DOse REsponse Curve
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Buildup to threshold is not necessary to elicit a response.
One exposure, even the slightest, will elicit a response |
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Latent Period
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Time that elapses between the exposure to ionizing radiation and the appearance of clinical symptoms
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Dose Rate
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Rate at which exposure to ionizing radiation occurs and absorption takes place
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What cells are highly sensitive to radiation?
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Young, rapidly dividing, non-differentiated cells
Such as thoss in bone marrow, testes, lymphoid organs and mucous membrane |
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What cells have intermediate sensitivity to radiation
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Ones that divide occasionally in response as a demand for more cells
Such as growing cartilage, growing bone and fine vasculature |
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What cells have low sensitivity to radiation?
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Ones that are mature and are incapable of division
Such as neurons, striated muscles and salivary glands |
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MPD
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Maximum Permissible Dose
Amount of whole body radiation that an occupationally exposed person can be exposed to without any harm 1 year = 5000mrem = 50mSv 1 week = 100mrem |
