Exam 2 Flashcards
What are the 3 characteristics of radiation?
o X-ray beam quality
o X-ray quantity
o X-ray bream intensity
What exposure factors are controlled on older panels?
- kVp control settings
- mA control settings
- Time setting
What determines the energy penetrating power of radiation?
Wavelength
What wavelength equals more penetrating power?
Short
What wavelength equals less penetrating power?
Longer
mean energy of the x-ray beam (wavelength + energy)
Quality
What is the quality of x-rays controlled by?
Kilovoltage
What type of quality beam is the outcome of increased kV and faster electrons?
High quality beam
How much kV does current dental radiography use?
65-100 kV
Increase kV + density increases = what image?
Darker image
Decrease kV+ density increases = what image?
Lighter image
Higher kV = what contrast?
Low contrast
Lower kV = what contrast?
High contrast
Low contrast =
shades of gray
High contrast =
black and white
Greater than or equal to 90 = what kVp?
High kVp
65-70 = what kVp?
Low kVp
What is the only thing that adjusts contrast?
kVp
What scale of contrast = 2 densities?
Short scale
What scale of contrast = lots of density?
Long scale
Device used to demonstrate short-scale contrast and long-scale contrast
Stepwedge
What is stepwedge used for?
Quality control
Machine calibration
What contrast is good for detecting periodontal disease and periapical lesions?
Low contrast
What contrast is good for detection of caries?
High contrast
time x-rays are being produced
Exposure time
Longer exposure time = more x-rays = what image?
Darker image
Shorter exposure time = less x-rays = what image?
Lighter image
What are older machines measured in?
Impulses
What are new machines measured in?
Hundredths/seconds
What is x-ray beam quantity controlled by?
Milliamperage
What dictates number of electrons passing through cathode filament?
Amperage
What mA = increase in number of electrons from cathode to anode?
Increased mA
kVp =
quality
mA =
Quantity
What regulates temperature of cathode filament?
Milliamperage
What mA = increased temperature (more electrons)?
Higher mA
What mA = decreased temperature?
Lower mA
Increased number of electrons =
More x-rays
Increase mA + increased density = what image?
Darker image
Decreased mA + decreased density =
Lighter image
What is adjustable?
Exposure time
What do we base exposure time off of?
Patient size
product of quantity and quality per unit of area per unit of time to exposure
Intensity
What is intensity affected by?
kV
mA
exposure time
distance
What regulates penetrating power by controlling speed of electrons?
kV
What kV = more energy and shorter wavelength?
Higher kV
What kV = increased intensity?
Increased kV
What regulates penetrating power by controlling number of electrons and x-rays produced?
mA
What mA = more energy?
Higher mA
What mA = increased intensity?
Increased mA
target to patient’s skin
Target-surface distance
Explains how distance affects the intensity of the x-ray beam
inverse square law
If distance is doubled, beam is ___ less intense
1/4
If distance is tripled, beam is ___ less intense
1/9
Amount of material we need to reduce x-ray beam intensity by half
Half-value layer (HVL)
What material do we need for HVL?
Aluminum filters
What does HVL measurement depend on?
The penetrating quality beam
What HVL = more penetrating beam?
Higher HVL
What are the geometric characteristics?
o Sharpness
o Magnification
o Distortion
Capability of the receptor to be able to reproduce the distinct outlines of an image
Sharpness
lack of sharpness, blurring of an edge
Penumbra
What is sharpness influenced by?
Focal spot size
Film composition
Movement
o Tungsten target of anode
o Determined by the manufacturer of x-ray equipment
Focal spot size
What focal spot = sharper image?
Smaller focal spot
What film = larger crystals = less sharpness?
Faster film
What film = smaller crystals = more sharpness?
Slower film
What crystals produce sharper lines?
Smaller crystals
What results in loss of sharpness?
Tube head movement
Receptor movement
Patient movement
What = non-diagnostic image?
Movement
Image that appears larger than actual size
Magnification
What is magnification influenced by?
Object-receptor distance
Target-receptor distance
What results from distortion?
Foreshortening
Elongation
What influences distortion?
Objected-receptor alignment
Why would we use bisecting technique over paralleling?
shallow pallet
hard time biting
rubber dam
formed by two lines diverging from a point
angle
imaginary line that splits angle into two equal halves
bisector
shape that is formed when three points are connected by three straight lines, makes three different angles
triangle
triangle with all even sides, angles all the same
Equilateral triangle
equal triangles
Congruent triangles
side of triangle that sits opposite of 90-degree right angle
Hypotenuse
Two triangles are equal if the triangles have two equal angles and share a common side
Rule of isometry
What is the central ray perpendicular to in bisecting technique?
Imaginary bisector
what is a result of Vertical angulation being too high?
Foreshortening
What is a result of Vertical angulation being too low?
Elongation
What are the bisecting technique devices?
Rinn BAI System
Stabe
Snap-A-Ray
What is the result of incorrect horizontal angulation?
overlap
What results in positive vertical angulation?
Angling PID down
What results in negative vertical angulation?
Angling PID up
What type of angling degree do we use when exposing bitewings?
Positive 10-degrees
What artifacts need removed for x-rays?
Jewelry
Glasses
Dentures
How do we prep our equipment?
o Set out holding device
o Control settings
What is the receptor position for bisecting technique?
1/8th inch beyond incisal or occlusal, apical end against palate
What are the 5 bisecting technique rules?
- receptor placement
- receptor position
- vertical angulation
- horizontal angulation
- receptor exposure
What needs to be parallel to the floor for the maxillary arch?
ala tragus
What needs to be parallel to the floor for the mandibular arch?
Occlusal plane
What is the point of entry clue for Maxillary centrals?
midline + ala tragus
What is the point of entry clue for maxillary canines?
canine fossa + ala tragus
What is the point of entry clue for maxillary premolars?
inner canthus of eye + ala tragus
What is the point of entry clue for mandibular centrals?
midline + symphysis of chin
What is the point of entry clue for mandibular canines?
midline + symphysis of chin
What is the point of entry clue for mandibular premolars?
inner canthus of eye + symphysis of chin
What is the point of entry clue for mandibular molars?
outer canthus of eye + symphysis of chin
What is the point of entry clue for bitewings?
premolars/molars + occlusal plane
What are advantages of bisecting technique?
o No beam alignment device
o Decreased exposure time
What are disadvantages of bisecting technique?
o Dimensional distortion
o Angulation problems
What error occurs?
- Appear blank/white, no anatomy
- Appears clear
Unexposed receptor
What error occurs?
- Film appears black
Film exposed to white light
What error occurs?
- Appears dark or high in density
Overexposed
What error occurs?
- Appears light or low in density
Underexposed
What error occurs?
- No apices seen on receptor
- Excessive radiolucent area
Root apex missing
What error occurs?
- Occlusal plane tipped/tilted
Dropped corner/downhill composition
What error occurs?
- Contact of one area superimposed over contact of adjacent tooth
Overlap
What error occurs?
- Partial image loss
- Clear or white unexposed area
Cone cut
What error occurs?
- Blunted roots
Foreshortening
What error occurs?
- Long, stretched out structures
Elongation
What error occurs?
- Not enough max. or mand. Anatomy
- No crestal bone visible in image
Vertical placement
What error occurs?
- Appropriate anatomy not seen or centered in image
Horizontal placement
What error occurs?
- Bent = distorted image (stretched)
Bending/creasing of film
What error occurs?
- Radiolucent or radiopaque artifacts, scratches
Debris
What error occurs?
- Finger present in image
Phalangioma
What error occurs?
- Film or indirect digital imaging
Double exposure
What error occurs?
- Blurry image
Movement
What error occurs?
- Film: herringbone pattern
- Digital sensors: blank or white
Receptor backwards/reversed
What error occurs?
- Radiopaque outline of cord
Wire/cord
