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89 Cards in this Set
- Front
- Back
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well-defined unilocular
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one cavity
border is well-defined, most benign lesions are unilocular |
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well-defined multilocular
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border is well defined with several cavities
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well defined honeycomb or soap bubble
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multilocular
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diffuce radiolucency
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cannot follow the border of the radiolucency, 90 % of the time is is cancer
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first diagnosis if there is a loss of cortical plate
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cancer
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hamular process
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bony projection that arises from the sphenoid bone and extends downward and slightly posteriorly
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hamular process on radiograph
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proximity to the posterior surface of the maxillary tuberosity,
varies greatly in length, width and shape among patients usually has a bulbous point, but sometimes tapered |
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coronoid process on radiographs
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the image of the mandible on maxillary pa's
its tapered or triangular radiopacity below the molar teeth and maxilla |
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superior gray scale resolution in digital photography
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the human eye can only appreciate 32 shades of gray, the traditional radiograph differentiates 16-25 shades of gray, while the digital image uses up 256 shades of gray
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storage phosphor imaging system
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uses reversible imaging plate rather than a sensor (more flexible)
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direct digital imaging system
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uses an intraoral sensor attached to a fiberoptic cable
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indirect digital imaging system
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scans an existing radiograph and digitizes the image
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charge-coupled device (ccd)
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the most common digital image receptor
solid state detector with silicon chip embedded in it the circuit in the chip is sensitive to the X-rays |
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primary radiation
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the radiation produced at the anode of the X-ray tube that is attenuated by the filter and object
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secondary radiation
(scatter) |
interactions of the primary beam with the atoms in the object being imaged
it is a major source of image degredation |
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when x-radiation passes thorough a patient, what three interactions can happen
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coherent scatter
photo electric absorption compton scattering |
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most scattered x rays in diagnostic xray imaging arises from:
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compton scattering
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what reduces the amount of scatter radiation?
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leaded rectangular done (reduces the size of the beam)
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collmination
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the control of the size and shape of the X-ray beam
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how big can the diameter of a circular beam be
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2.75 inches
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short wavelength xrays
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great penetrating power,
produced at higher kilovoltage form the image on the film |
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long wavelength xrays
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produced at lower kilovoltages
lower penetrating power are useless rays |
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what filters out long wavelength rays?
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aluminum discs
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filtration
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removal of parts of the X-ray spectrum using absorbing materials in the X-ray beam
reduces patient does, contrast and film density |
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inherent filtration
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filtration by any parts of the X-ray tube through which the beam must pass
parts include the glass envelope, and oil |
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added filtration
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obtained by placing thin sheets of aluminum in the conn to filter the beam further
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total filtration
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inherent + added filtration
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recommended total filtration
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equivalent of 0.5 mm (below 50 kvp) and 2.5 mm (over 70 kvp) of aluminum
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how far should the operator stand from the patient when taking xrays
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6 feet
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where should the operator stand to avoid the primary beam when taking xrays
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90-135 degree angle to the beam
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EKTA speed film
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provides the most effective way to reduce exposure time, amount of radiation reaching the patient and amount of scatter radiation to the operator
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what is the max dose of radiation for someone who works near radiation
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5 rem (.1rem per week)
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what is the max dose for normal people
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.5 rem
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what can too much radiation exposure cause?
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carcinomas, genetic mutations, different leukemias, cataracts
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mechanisms that cause carcinogenesis and genetic mutations
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frame shift mutations
synergism with checimal carcinogens altered dna repair enzymes |
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radiosensitive cells
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small lymphocytes
bone marrow reproductive cells prostate gland hemopoietic tissue |
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what is the most sensitive to radiation?
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hemopoietic tissue
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radioresistant cells
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mature bone
muscle nerve |
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what is the most resistant to radiation?
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muscle
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radiation absorbed dose (rad)
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a measure of the energy imparted any any type of ionizing radiation to a mass of any type of matter
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equivelant dose
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the correct unit of measurement used by the dentist to compare the biologic-risk effects/estimates of different radiation damage to a tissue or organ
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effective dose
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used to estimate the risk in humans
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exposure
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a measure of radiation quantity
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roetgen (R)
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traditional unit of radiation exposure measured in air
only applies to X-rays and gamma rays |
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what has more energy?
X-rays or light |
X-rays
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cephalometrics
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(lateral head radiograph) radiographs used to study craniofacial growth, diagnosis, planning ortho, and evaluation of treated cases
assess tooth to tooth, bone to bone and tooth to bone relationships |
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serial cephalometric films show what?
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amount and direction of growth
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submental vertical view
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diagnose basilar skull fractures
provides diagnostic info about zygoma, zygomatic arches and mandible taken from below mandible and film above the head |
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water's view
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showing anterior view of paranasal sinuses and mid face and orbits
film is against patients face and source is behind patients head |
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towne's view
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visualize condyles and neck of mandible
film is under head with source from the front at 30 degrees from frankfort plane-directed right at the condyles |
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conventional tmj radiographs
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show the condyles in the glenoid fossa, range of the condyles antero-posterior movement and areas of bone destruction of the condylar heads
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developer solution
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converts invisible image into visible image
reduces silver halide crystals to black metallic silver |
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4 chemicals that are in developing solution
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developing agent (hydroquinone
antioxadant preservative (sodium sulfite) accelerator (sodium carbonate) restrainer (potassium bromide) |
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developing agent
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Hydroquinone
changes exposed silver halide crystals to black metallic silver gives detail to the X-ray |
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antioxidant preservative
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sodium sulfite
prevents developer solution from oxidizing int the presence of air |
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accelerator
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sodium carbonate
alkali that activates the developing agents and maintains the alkalinity of the developer softens gelatin of emulsion |
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restrainer
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potassium bromide
control the action of the developing agent so it does not develop the unexposed silver halide crystals to produce fog |
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xray fixing solution
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fixer
stops development and remove remaining unexposed crystals |
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what four chemicals are in fixer?
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clearing agent (sodium or ammonium thiosulfate)
antioxidant preservative (sodium sulfite) acidifier (acetic acid) hardner (potassium alum |
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clearing agent
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sodium or ammonium thiosulfate
commonly called hypo dissolves and removes underdeveloped silver halide crystals |
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antioxidant preservative
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sodium sulfite
prevents decomposition of the fixer chemical |
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acidifier
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acetic acid
necessary for the correct action of the other chemicals neutralizes any alkaline developer still on the film |
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hardner
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potassium alum
shrinks and hardens the gelatin in the emulsion shortens drying time protects the emulsion from abrasion |
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brown film
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not fixed long enough
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advantages of bisecting angle technique
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decreased exposure time
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disadvantages of bisecting angle technique
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image may be distorted
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buccal object rule
slob rule |
same lingual opposite buccal
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inverse square law
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original intensity= new distance2
new intensity original distance2 |
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focal spot
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small area of tungston on the anode from which emanates and receives the impact of the speeding electrons
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target
tungston target |
a tungsten wafer embedded in the anode face at the point of electron bombardment
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target film distance
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distance from the xray source (focal spot) to the film (dertimined by the length of the cone)
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two sizes of cones
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20 cm - 8 inches
41 cm - 16 inches |
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half value layer (HVL)
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the amount of material required to reduce the intensity of an X-ray beam to half
normaly aluminum or copper thickness, may also be other materials or media |
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what does hvl incicate
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quality of an X-ray beam
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what does the focal spot influence
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image sharpness/definition
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intensifying screens
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devices used in extra oral radiography (pano, ceph)the convert X-ray energy into light which exposes the screen film
reduces amount of radiation exposure |
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what does the operator control?
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kvp kilovoltage
mA miliamperage exposure time |
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kVp
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the quality oor penetrating power of the X-ray beam that controls the speed of electrons
suitable range of kVp 64-100 |
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how does kVp influence the X-ray beam and radiograph
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contrast and determines the penetrating ability of the X-ray beam
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what affect does increasing or decreasing kvp have?
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increasing kvp reduces subject contrast
decreasing kvp increases subject contrast |
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miliamperage mA
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controls the number of X-rays produced
suitable ranges 7-15 controlled by the temperature of the tungsten target |
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exposure time
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the length of time X-rays are produced
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density
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overall darkness of a radiograph
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how to affect density
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increases as mA, kVp, or exposure time increase
decreases as mA, kVp, or exposure time decrease |
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contrast
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difference in the degree of blackness between adjacent areas on a radiograph
affected by kVp only higher kvp produces low contrast |
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5 rules to create accurate images
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1. use smallest focal spot
2. use longest source-film distance 3. place film as close to structure as possible 4. direct central ray at right angle to film 5. keep film parallel to structure |
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what does a long cone do?
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minimizes image magnification
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X-rays are generated when a stream of electrons (produced by the filament) travels from the cathode anode and is suddenly stopped by its impact on the tungsten target
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filament
molybdenum cup electron stream tungsten target focal spot copper sleeve vaccum xray beam leaded glass housing |
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occult diseases
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includes small carious lesions, cysts and tumors that don't have signs or symptoms
X-rays should not be done to look for these |
