Rad Flashcards
Define xradiation
High energy, electromagnetic radiation produced by the collision of electrons with a metal target
Primary radiation
X-ray beam produced at the target of anode, exits tube head
Aka useful beam
Outer shell electron collides with X-ray photon, photon gives up energy to eject electron from orbit. Photon loses energy and continues in different direction at lower energy
Compton scatter
Low energy photon interacts with outer shell electron. No change in atom and no ionization
Coherent scatter
Insulating oil is used to
Prevent overheating
Where does thermionic emission occur
Cathode-filament wire
What is thermionic emission
The heating of the filament that leads to the release of electrons
Cathode is
Negatively charged
Anode is
Positively charged
Step up transformer increases voltage
65,000-100,000
Step down transformer decreases voltage
3-5 volts
What is collimation
Limits radiation dose to patient by limiting the amount of tissue that is exposed
What does collimator do
Restricts the size and shape of X-ray beam
Alara
As low as reasonably achievable
Maximum accumulated dose is determined by
Age
What is maximum permissible dose
Max dose body is permitted to receive in a specific amount of time with little to no injury
5 rem/year (0.05msv)
Safety code 30
Radiation protection in dentistry
5 rules to paralleling technique
Film placement in prescribed area
Film parallel to axis
Vertical angulation central ray directed perpendicular to film
Horizontal angulation through contacts
Film exposure X-ray beam centered so all areas exposed
Is paralleling or bisecting more accurate
Paralleling
What is bitewing technique used to examine
Interproximal surfaces of teeth
Top of crestal bone
Clinical crowns
If horizontal angulation is incorrect it results in
Overlap
If vertical angulation is incorrect what results
Distortion
If PID is positioned below occlusal plane and ray is directed upward the vertical angulation is
Negative
Overlap refers to
Area of one tooth Superimposed over adjacent tooth
X-rays discovered what year by whom
1895
Wilhelm roentgen
What is free radical formation
Primary means by which xradiation causes cell damage
Free radical formation happens when X-ray photon
Ionizes with water
What is dose response curve
Response and damage of tissues with the dose or amount of radiation received
What are stochastic effects
Direct function of dose
Due to ionization radiation on chromosomes (cancer)
No dose threshold
What are non stochastic effects
Somatic effects that have a threshold
Caused by significant cell damage
Increase in severity as dose increases
(Loss of hair, infertility, cataracts)
Latent period
Time between exposure and observable clinical signs
Injury period
Follows latent period
Cellular damage may result
Sequence of radiation injury
Latent period
Injury period
Recovery period
Somatic cells refer to all cells except
Reproductive
Genetic cells
Reproductive cells
Genetic effects of radiation are seen
In offspring not seen in the individual radiated
Cells most resistant to rad exposure
Mature bone, muscle and nerve
Roentgen “R” units of measurement measure
Exposure
Energy produced by gamma radiation
Also known as coulomb
Free radical
Tall or group of atoms that has one unpaired electron
Unstable and highly reactive
Threshold curve
Below a certain level (threshold) no response is seen
Linear curve
Response is proportional to the dose
Linear non threshold curve
Response is seen at any dose
Most sensitive cells to radiation
Small lymphocyte
Bone marrow
Reproductive
Young cells
Secondary radiation
When primary beam interacts with matter. Less penetrating
Leakage radiation
Improperly sealed or non lead lined tube head
Quality of X-ray is controlled by
Kvp
X-rays with shorter wavelengths have more penetrating power thus more/less kvp?
More/higher
Kvp controls speed and energy of
Electrons
Kv for digital radiography
60-70 kv
Less than 65 kv =
More than 100 kv =
Less than 65= inadequate penetration
More than = over penetration
Higher kv should be used when
When area to be examined is thick or dense
Density refers to the overall
Blackness or darkness of an image
Density is affected whenever there is a change in what
Kvp, ma, exposure time
High density results in film being
Very black
Low density results in image being
Very light
Contrast refers to how
Sharply dark or light areas are differentiated
An adjustment in what leads to change in contrast
Kv
Low kv results in what kind of contrast
High contrast (not many shades of grey)
High kv results in what kind of contrast
Low contrast. Many shades of grey
To compensate for the penetration power of the X-ray beam, exposure time must be adjusted if
The kvp is adjusted
If lvp is decreased exposure time must be
Increased
Ma measure the ___ of an X-ray
Quantity
Higher ma equals more
Electrons
Ma settings usually set at
7-15
If ma is increased beyond 15 what happens
Excessive heat production
If ma is increased the exposure time must be ___ to maintain density
Decreased
Target surface distance describes
Distance from source of radiation to clients skin
Target-object distance
Source of radiation to tooth
Half value layer
To reduce intensity of beam, aluminum filters are placed in path inside tube head
Film composition: components of film
Film base
Adhesive layer
Film emulsion
Protective layer
The film base withstands what and provides what for emulsion
Heat, moisture and chemical exposure
(Slight blue tint for image quality)
Provides strength and support for emulsion
Adhesive layer attaches
Emulsion to base
Film emulsion allows greater
Film sensitivity to xradiation
Film emulsion: gelatin
Evenly suspends
Silver halide crystals over film base
Absorbs processing solution allowing chemicals to react with crystals
Film emulsion: silver halide crystals
Absorbs?
Absorbs radiation during exposure and store energy from radiation
Latent image describes
An existing but not yet developed film
Larger crystals results in a faster/slower speed film
Faster
Intraoral film packet has emulsion
On both sides
Plastic film wrapper protects
Film from lights
Intraoral film packet lead foil can be found behind
Film shielding
Intraoral film packet tube side
Solid white and has I’d dot
Extraoral films two types
Screen and non screen
Screen films require screen for exposure and requires
Less radiation to expose films
Intensifying screens are smooth plastic sheets coated with fluorescent crystals; purpose?
Intensifies efffect of X-ray on the film
Less radiation is required
Non- screen films do not require an intensifying screen for exposure instead emulsion is sensitive; is this recommended
No because it requires more exposure time
Duplicating films may be used for
Teaching aids
Referrals
Insurance purposes
Duplicating films what only exists on one side of film
Emulsion
Radiolucent appears
Black or dark
-air, pulp, pdl space
Radiopaque appears
White or light
-restorations, enamel, bone
Lead lined storage containers prevent
Film fogging
If ma is increased the image will appear
Darker
If kvp is decreased the image will appear
Lighter
If exposure time is decreased the film density___ resulting in a ___ image
Decreases
Lighter
Short scale contrast refers to
Black and white only shows 2 densities
Low kvp= high contrast which is short or long scale contrast
Short scale
Long scale contrast refers to
Many shades of grey
Sharpness refers to
Reproduction of distinct outlines of an object
Sharpness is influenced by
Focal spot size
Film composition
Movement
Penumbra
Fuzzy/blurry image
Smaller focal spot results in
Sharper image
Longer pid results in more/less magnification
Less
Distortion refers to
Elongation or foreshortening
Manual film processing steps
Development
Rinsing
Fixation
Washing
Drying
Film processing: reduction
Halide portion of the exposed energized halide crystals are removed
Film processing: selective reduction
Reduction of energized, exposed halide crystals into black metallic silver while the unexposed halide crystals are removed from film
Reduction of crystals results with
Black metallic silver images
Manual film processing: rinsing
Film rinsed to remove and remaining developer solution and stops development
Manual film processing: fixation
Removes unexposed silver halide crystals. Emulsion is hardened
Manual film processing: development
Emulsion is softened
Chemical reaction that reduces exposed silver halide crystals into black metallic silver (creates dark areas on radiograph)
Manual film processing: washing
Remaining chemical solutions removed with water bath
Quality assurance film fog
Fog = expired
Reference radiographs
Processed under ideal conditions and then used to compare film densities of daily processed X-rays
Stepwedge serves as
Quality assurance
Who is responsible for classifying high level/low level
EPA environmental protection agency
