Rad Flashcards by Kate Niznik

Define xradiation

High energy, electromagnetic radiation produced by the collision of electrons with a metal target

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Primary radiation

X-ray beam produced at the target of anode, exits tube head
Aka useful beam

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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

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Low energy photon interacts with outer shell electron. No change in atom and no ionization

Coherent scatter

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Insulating oil is used to

Prevent overheating

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Where does thermionic emission occur

Cathode-filament wire

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What is thermionic emission

The heating of the filament that leads to the release of electrons

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Cathode is

Negatively charged

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Anode is

Positively charged

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Step up transformer increases voltage

65,000-100,000

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Step down transformer decreases voltage

3-5 volts

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What is collimation

Limits radiation dose to patient by limiting the amount of tissue that is exposed

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What does collimator do

Restricts the size and shape of X-ray beam

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Alara

As low as reasonably achievable

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Maximum accumulated dose is determined by

Age

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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)

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Safety code 30

Radiation protection in dentistry

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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

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Is paralleling or bisecting more accurate

Paralleling

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What is bitewing technique used to examine

Interproximal surfaces of teeth
Top of crestal bone
Clinical crowns

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If horizontal angulation is incorrect it results in

Overlap

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If vertical angulation is incorrect what results

Distortion

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If PID is positioned below occlusal plane and ray is directed upward the vertical angulation is

Negative

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Overlap refers to

Area of one tooth Superimposed over adjacent tooth

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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

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