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Radiographs were first discoevred in 1895 by....who say his own hand bones
Wilhelm Roentgen
he was exploring the properties of Hittorf-Crookes cathod ray tube
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The short the wavelength the ______ penetrating it is.
more
shorter wavelengths are more penetrating because there are more waves of radiation hitting the target in a certain time period
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bundles of energy (photons, which move at the speed of light) that consist of particles and waves of electromagnetic radiation.
particulate radiation
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as photons interact with electrons in the xray tube head, they remove the electrons from atoms. this produces the negative or positive imbalanced ions of
ionizing radiation
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sudden deceleration of negatively charged electron as it passes near a positive nucleus, become attracted to it
Bremsstrahlung or braking radiation
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xray radiation which is absorbed by the patient result in radioopaque areas. this absorption is called
attenuated
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photons may exit the patient, and are exposed on radiographic films as radio_____ areas.
radiolucent areas
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classic scatter radiation also called _______ or _______ occurs when a low energy xray photon that is unable to eject an electron from an atom excites the e instead. the photo fails to survive, though the excited e produces a new photo to be ejected from the atom
coherent or Thompson effect
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when a high-speed photo ejectcauses an outer orbit electron to drop down in the auses an outer orbit electron to drop down in the space left empty by the ejected electron.
Characteristic radiation or photoelectric effect
This action emits energy. The electron that was originally ejected from the inner orbit is called a recoil electron.
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result of a high-energy photon ejecting a loosely bound outer orbit electron after the two collide. in this case, energy is being absorbed
Compton effect
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when xray photons intermingle with water and oxygen of human tissue, the result is
free radicals
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Tissue Sensitivity
High: Lymphocytes, bone marrow, reproductive cells, thyroid glands in children, intestine, endocrine glands, skin, oral mucosa
Moderate: developing bone and cartilage, connective tissue, small vasculature
Low: mature bone and cartilage, salivary glands, thyroid glands in adults, kidneys, liver, muscles, nerve tissue
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What is the most sensitive tissue to radiation?
lymphocytes
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How sensitive is bone marrow to radiation?
High
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How sensitive is reproductive cells to radiation
high
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How sensitive are children's thyroid glands to radiation
high
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How sensitive are intestines to radiation
high
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How sensitive are endocrine glands to radiation
high
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How sensitive is skin to radiation
high
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How sensitive is oral mucosa to radiation
high
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How sensitive is developing bone and cartilage to radiation
moderate
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How sensitive is connective tissue to radiation
moderate
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How sensitive are small vasculatures to radiation
moderate
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How sensitive is matuer bone and cartilage to radiation
low
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How sensitive are salivary glands to radiation
low
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How sensitive are thyroid cells in adults to radiation
low
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How sensitive are kidneysto radiation
low
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How sensitive is the liver to radiation
low
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How sensitive are muscles to radiation
low
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How sensitive is nerve tissue to radiation
low
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the safest place to stand when exposing xrays to a patient is
90-135 degree at the side of patient and away from primary beam
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lead aprons should be how thick?
.25 mm
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how far away should you stand from an xray beam?
6 ft
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what is the maximum permissible dose (MPD) for dental personnel?
5.0 rem/year
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what is the maximum permissible dose for the general public?
.5 rem/year
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maximum accumulated exposure accounts for age....
5 for every year of their age after the 18th year.
formula: 5(age - 18)
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amount of radiation absorbed that would cause biological death
lethal dose
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the period from the time of exposure to the actual occurrence of a biological effect from radiation
latent period
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two ways to measure radiation:
Roentgen (R), rads, and rems
and
SI system, coulombs per kilogram. Gray, Sievert, and coulombs/kg
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100 rad = ? Gy
100 rad = 1 Gy
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100 rems = ? Sv
100 rems = 1 Sv
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1 R = ? C/kg
1 R = 2.58 x 10(-4) C/kg
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cathode contains the..
filament, which produces electrons
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filament produces
electrons
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when the heated filament "boils off" electrons in a cloud which surrounds the filament
Thermionic emission
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Cathode is controlled by
milliamperage
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percentage of electrons converted into radiographic electrons, and heat
1% radiographic
99% heat
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Cathod charge, Anode charge...?
- To remember whether the cathode and anode are positive or negative, and in which direction the electrons travel, think about wanting a grade of
- C- to go to an A+!!
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anode contains
focal spot on tungsten target
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regulation states that aluminum filter must be ___ mm for xray exposure below 70 kVp, and ___ mm for exposures greater than 70 kPv
- less than 70 kPv = 1.5 mm
- greater than 70 kPv = 2.5 mm
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utilization of lead diaphragms to restrict the size of the beam
Collimation
does so through a round or rectangular aperture (opening) of the position indication device (PID)
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wire sensor that is placed like a regular radiographic film in the oral cavity.
Direct digital imaging
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scans and digitizes a radiographic film onto the monitor, this method uses a CCD camera to scan in the radiograph
Indirect digital imaging
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utilizes reusable imaging plate that is coated with phosphor.
Storage phosphor imager
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Cathodes control the milliamperage which in turn controls the amount of electrons boiling off...which in turns effects the
quantity of radiation
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work capcity of an xray unit is measured in volts or..kilovots peak (kVp). this controls the
quality of radiation
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Increasing kilovoltage results in
shorter more frequent wavelengths
decreasing kilovolt peak yields high contrasts, which increasing kVp yields low contrast.
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Decreasing the kVp to 65-70 kVp will...
allow for more contrast between black and white, excellent for caries detection
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Increasing the kVp will (75-90 kVp)
decrease the contrast, more shades of gray, excellent for determing bone levels
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Contrast and kVp are in what type of mathmatical relationship?
inverse, as one goes up the other goes down
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radiographic films are coated on both sides with green gelatin called emulsion, emulsions are made up of...
silver halide crystals (silver bromide and silver iodide)
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Film speeds range from A to F. The high speed films requires less radiation exposures....but most dental radiographic films are
D and E speed.
E speed film needs about fifty percent less exposure than D-speed film
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Film size..
0
1
2
3
4
- 0: children
- 1: mixed dentition, or anterior
- 2: adult dentitions, both perapicals and bitewings
- 3: long bitewings
- 4: occlusal films
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SLOB rule (Same Lingual, Oppisite Buccal)
to determine where an object is in a radiograph
- 1 film taken normally
- 2 film taken (for example) 20 degrees mesially
- if the object moves mesially as well it is on the lingual side
- if the object moves distally it is on the buccal aspect
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too much vertical angulation results in
short teeth
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not enough vertical angulation equates to
elongated teeth
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umbra is the main shadow, the side shadows are called
pneumbra
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A small focal point will yield a
sharper radiographic image
(more parallel rays, less rifraf)
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object (tooth) to film distance should be
short, to decrease magnification
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source (xray) to film distance should be
increased to reduce magnification
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Manual processing films temperature and time
- 68 F for 5 min
- or
- 72 F for 4 min
( automatic processors function at a higher temperature)
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developing solution is a combination of
hydroquinone and elon
- hydroquinone: producing contrast, changes the latent image in the silver halide crystals to black metallic silver.
- elon: generating details, prodcues gray tones of the latent image.
Sodium carbonate or potassium hydroxide softens and swells the emulsion to provide an access for hydroquin and elon to contact the silver bromide crystals.
Sodium sulfite, preserves, reduces oxidation
potassium bromide and potassium iodidie are restrainers that reduce the action potential of developing solution
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hydroquinone
found in developing solution, produces contrast by changing the latent image of the silver halide crystals to black metallic silver
-
elon
elon: generating details, prodcues gray tones of the latent image.
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softens and swells the emulsion to provide an access for hydroquin and elon to contact the silver
bromide crystals.
Sodium carbonate or potassium hydroxide softens and swells the emulsion to provide an access for hydroquin and elon to contact the silver bromide crystals.
-
Sodium sulfite
in developing solution, preserves and reduces oxidation
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potassium bromide and potassium iodidie
restrainers that reduce the action potential of developing solution
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fixer solution is composed of
ammonium or sodium thiosulfate: fixing agent that eliminates unexposed, under developed silver halide crystals
acetic acid or sulfuric acid: neutralizes the developing solution to inhibit its action
Sodium sulfite: reservative
aluminum chloride or alumnium sulfide: to shrink emulsion
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a dark room needs to be what size?
16 square feet in size
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saftey light in dark room needs to be
set 4 ft above working surfaces and 15 watts or less
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If a radiograph comes back clear with nothing on it then
it was never exposed
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if a radiograph is completely black than
it was exposed to light
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if a radiograph is too dark then
temperature of developing solutions is too warm
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a green film indicates
it was not fixed enough
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black streaks on a film indicate
bent film
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white streaks on a film indicate
scratch, torn emulsion
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the inverted Y is composed of
anterior wall of nasal floor and the wall of the sinus
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automatic processing requires what temp and tiem?
83 F for 5 min
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lead disk that shapes and directs the beam
Collimation
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what directs the xray beam from the cathode to the anode
focusing cup, found in cathode and directs the beam to the anode
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acidifier of fixing solution
acetic acid
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swells and softens emulsions
sodium carbonate
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shrinks and hardens emulsions
ammonium sulfate
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what chemical is found in both developing and fixer solutions?
sodium sulfite, preservative
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