Oral Radio (Mental Dental) Flashcards
What dissipates heat in tubehead of xray machine?
Copper
How xray beam weakens as it travels through matter
Attenuation
Atomic nuclei or subatomic particles moving at high velocity
Alpha and beta particles from radioactive decay are examples
Particulate radiation
Movement of energy as a combination of electrical and magnetic fields
SHorter wavelength= higher energy
Electromagnetic radiation
_____ xray production
Primary source of x-ray photons
Electron stikes a target and brakes giving off energy
Generates continuous specturm of energy
Bremsstrahlung radiation
____ xray production
Secondary source of xray photons
Electron accidentally knock into another electron and drops into a lower energy orbital
Emits a photon of specific energy
Characteristic xray production
_______
-tungsten filament that produces electrons
Molybdenum focusing cp focuses beam onto small focal spot
Cathode (negative)
_____
-Tungsten target that converts electrons to xray photons
Copper stem dissipates heat
Anode
Does x radiation begin at cathode or anode?
Cathode to anode
What does the glass in the xray tube do?
Insulation
What does aluminum do in the xray tube?
Filtration
What does lead in the xray tube do?
Collimation
_____
-Quality of electrons
Number of photons
Density: darkness of image
Intensity
______
-Quality of electrons
Energy of photons
Contrast: difference among gray values
Energy
DOes exposure time affect intensity or energy?
INtensity
What setting of xrays is most frequently changed?
Exposure time
Does tube current affect intesnity or energy?
INtensity
Does tube potential (kVp) affect intensity or energy?
Both
Involves aluminum
Removes lower energy photons from the beam to reduce exposure
Conceptually similar to beam hardening
Filtration
Involves lead
Reduces beam size to reduce pt exposure
Rectangular collimation is best method to reduce radiation dose
Collimation
What is the best method to reduce radiation dose to pt?
Rectangular collimation
To get a sharper image and less magnification, how do you position source and receptor?
Longer PID, close receptor
_____ is the shadow behind an image
-Clear portion of the xray
Umbra
_____ is the side shadow
-More blurry image
Penumbra
Do you want focal spot size to be larger or smaller to create a sharper image
Smaller
Do you want source to object distance to be longer or shorter to create a sharper image?
Longer
Do you want object to image distance to be longer or shorter for a sharper image?
Shorter
IF you increase exposure time, how is density and energy affected?
INcreased density (darkness)
If you increase mA, how are density and energy affected?
Density increased
If you increase kVp, how are density and contrast affected?
INcreased density; decreased contraact
If you increase filter, how are density and contrast affected?
Decreased density(lighter); increased contrast
If you increase distance, how are density and energy affected?
decreased density (lighter)
Incident photon contacts an outer electron
Decreases energy
About 8% of interactions in a dental x-ray beam
Coherent scattering
INcident photon contacts an inner electron and forms an ion pair
Increases contrast
About 30% of interactions in a dental x-ray beam
Photoelectric absorption
Incident photon contacts an outer electron and forms ion pair
Decreases contrast
About 62% of interactions in a dental xray beam
Compton scattering
______
Energy procduced by xray tuve
Measured in Roentgen
Exposure
Energy abosrbed in tissue
MEasrued in Gray
Absorbed dose
Energy absorbed in tissue multiplied by radiation weighting factor
Measured in Sieverts
Equivalent dose
Energy absorbed in tissue multiplied by tissue weighting factor
Measured in Sievert
Effective dose
___ effects
Threshold dose must be achieved before any effects will be seen
-Hair loss, cataracts, skin damage, oral mucosisits
Not seen in dental xrays
Deterministic effects
____ effects
Linear no threshold model: there is no threshold dose
Stochastic effects
DIrect or indirect radiation: accounts for 1/3 of biologic effects
Direct
DIrect or indirect radiation: accounts for 2/3 of biologic effects
Indirect
T/F: Cells that are mitotically active are more radiosensitive
Tru
What is the occupational exposure limit of radiaition?
50 mSv / yr
Is there more or less radiation with digital radiographs?
Less radiation
_____ is in developer solution and is first electron donor that reduces silver ions to metallic silver at latent image site
Phenidone
_____ in delveloper solution provides an electron to reduce oxidized phenidone to original active state
Hydroquinone
____ is part of xray film with silver halide crystals in a gelatin material
Film emulsion
____ is the main portion of the fixer solution that acts as a cleaning agent, removes undeveloped silver halide crystals
Ammonium thiosulfate
Barium fluorohalide plates capture and store x-ray energy from dental exposure
PSP
SIlicon sensor chips captures xray and rapidly displays image on monitor
CCD/ CMOS
Angled PA ceph of skull
Best film of paranasal sciences
Water’s view
Angled PA ceph of skull
Best film to visualize condyles
Towne’s view
Base projection of skull
Best film to visualize basilar skull and zygomatic fractures
Submentovertex view
Central rsy of xray beam aimed perpendicular to the imaginary bisector between long axis of tooth and long axis of receptor
Bisecting angle technique
REceptor is placed parallel to long axis of tooth
Central ray of xray beam aimed perpendicular to long axis of both tooth and receptor
Paralleling technique
What is the most common error in radiology?
Elongation
INcreased radiographic density is caused by which of the following?
Decreased kVp
Decreased mA
Decreased targetobject distance
Increased object-image distance
Decreased target-object distance
If an unwrapped xray film is exposed to ambient light for a second and then processed it _____
Will be darker than normal
Will be lighter than normal
Completely black
completely clear
Completely black
Which dental tissue is most likely to interact with xrays via photoelectric absorption?
Enamel: densest tissue
Which of the following is the most radiosensitive type of cell?
Skeletal muscle fiber
Endothelial cell
Neuron
Macrophage
Basal epithelial cell
Basal epithelial cells (stem cells constantly dividing)
Which of the following influences the mean energy of xray beam?
mA
Exposure time
Amount of filtration
Collimation
Amount of filtration
