Radiology

x-radiation:

a high-energy radiation produced by the collision of a beam of electrons with the tungsten target

What does ALARA stand for?

As Low As Reasonably Achievable

who discovered x-rays?

Wilhelm Conrad Roentgen

what were x-rays originally called?

Roentgen rays

when was digital dental radiography introduced?

1987

t/f: during early years of film, only one side had emulsion coating requiring long exposure times

true

electrons have a ______ charge

negative

Protons have a _______ charge.

positive

Neutrons have a ________ charge

neutral

an atom has a nucleus, what is it made of?

protons & neutrons

what revolves around the nucleus of an atom?

electrons

when atoms gain or lose an electron they become unstable are are called ________

ions

what is ionization?

the formation of ion pairs

what is ionizing radiation? what are the two types?

radiation that produces ions; particulate & electromagnetic

t/f: particulate radiation has mass

true

this type of ionizing radiation travels at high speeds in a straight line

particulate radiation

this type of ionizing radiation travels in waves through space and has no mass

electromagnetic radiation

what is wavelength?

the distance between two adjacent wave crests

what is frequency?

the number of waves that pass a given point per unit time

what is velocity?

speed of the wave

the shorter the wavelength the _________ the radiation

stronger

what does insulating oil in the tube head do?

surrounds the x-ray tube and transformers inside the tubehead; absorbs the heat created by the production of x-rays

what does the tubehead seal do?

seals the oil in the tubehead and acts as a filter to the x-ray beam

what is the purpose of the transformer in a x-ray machine?

controls voltage of incoming electricity

this part of an x ray machine is under a vacuum, and prevents x-ryas from escaping in all directions. it has a small non-lead "window" that allows x-rays to exit.

leaded glass housing

electrons in a tube head travel from the ________ to the _________

cathode; anode

the cathode supplies what to produce x-rays?

electrons

when heated, this filament produces electrons in the cathode

tungsten filament

what does the anode consist of?

tungsten target and copper stem

What does the tungsten target do?

Stops electrons so energy can be converted to x-rays

at what voltage are electrons sent from the cathode to the anode? what can the clinician do to control this?

65,000 to 100,000; adjust kV setting

less than ___ % of electrons are converted to x-rays the remaining _____% are lost as heat dissipated through copper stem

1%; 99%

this type of radiation is produced when high-speed electrons are stopped or slowed down by tungsten atoms of a dental x-ray tube - majority of production

general radiation

this type of radiation is produced when a bombarding electron from the tube filament collides with an orbiting K electron of the tungsten target

characteristic radiation

what is coherent scatter?

new x-rays scattered in different directions than the original (8%)

what is photoelectric effect?

x-ray is absorbed and vanishes (30%)

what is compton scatter?

new, weaker x-rays are formed and scattered in new directions (62%)

Kilovoltage (kV) controls the __________ of electrons and ___________ of x rays

speed; quality

Increased kVp = _______ contrast

decreased; many shades of grey

decreased kVp = _________ contrast

increased; more black/white

if a clinician increases the kVp from 65 to 80 they are increasing the __________ of electrons

speed

3 multiple choice options

what does kV affect on radiographs?

contrast

what range of mA does dental radiography use?

7 to 15 mA

increased mA = ___________ image

darker

decreased mA = ____________ image

lighter

when kVp and mA are increased, exposure time must be ___________

decreased

mA affects the ___________ of the x-rays

quantity

what are examples of the inverse square law?

when the distance is doubled the beam is 1/4 as intense; when the distance is halved the beam is 4 times as intense

Define the inverse square law

the intensity of radiation is inversely proportional to the square of the distance from the source of radiation

what is half-value layer (HVL)?

the thickness of material that , when placed in the path of the x-ray beam, reduces the exposure rate by one-half (aluminum filter)

what is penumbra?

the fuzzy or blurred area that surrounds an image

what can increase magnification?

short PID - short target / receptor distance

what is the most common type of cell damage in humans from x-rays?

free radical formation

what is the latent period?

period of time from exposure to visible damage

is a shorter latent period or longer latent period better?

longer

all of the following are radiosensitive cells except one, choose the exception:

nerve, liver, muscle

3 multiple choice options

all of the following are radioresistant cells except one, choose the exception:

skin

3 multiple choice options

what is the unit of measure for amount of radiation in the air?

Coulombs/kg

what is the unit of measure for amount of radiation absorbed by the tissue?

Grey (Gy)

what is the unit of measure for the effect of radiation on the tissue?

Sievert (Sv)

What is the MPD for an occupationally exposed person?

5 rem/year (5000 mrem) or 0.05 Sv/year (50 mSv)

what is the MPD for a non occupationally exposed person?

0.5 rem/year (500 mrem) or 0.005 Sv/year (5 mSv)

what is the purpose of the aluminum disk placed between the collimator and tubehead seal?

filters out lower energy x-rays from the beam

how thick does the aluminum filtration disk need to be?

at least 2.5mm

what does the collimator do?

restricts the size and shape of x-ray beam

t/f: the shorter the pid the less divergence of the beam

false; longer

the operator must stay at least ___ feet away from the tubehead during exposure

6

what angle should the operator be standing relative to the x-ray beam

90-135 degrees

how much vertical angulation should be used for taking bite-wings

+10 degrees if not using Rinn or XCP

what radiographic technique is mostly likely to produce the best image?

paralleling technique

what is the paralleling technique?

when the image receptor plane is parallel to the long axis of the tooth and the central x ray beam is perpendicular

what is the bisecting technique?

when the angle of the long axis of the tooth and the plane of the receptor are not parallel

what are common errors associated with the bisecting technique?

vertical angulation, horizontal angulation, cone cut

what is excessive vertical angulation?

image is foreshortened

what is inadequate vertical angulation?

image is elongated

when taking a PAN, this imaginary plane (top of ear to bottom of eye socket) needs to be parallel with the floor

Frankfort

after exposing a pan, you notice the anterior teeth are blurred and narrow, what error occurred?

patient was too far forward on the bite block

after exposing a pan, you notice the anterior teeth are blurred and magnified, what error occurred?

patient was too far back on bite block

after exposing a pan, you notice the teeth make a "smile", what error occurred?

patients chin tipped too low

after exposing a pan, you notice the teeth make a "frown", what error occurred?

patients chin tipped too high

what is a ghost image on a panoramic?

it is a opaque shadow of a object located on the opposite side of the patient

what is a waters projection used to evaluate?

maxillary sinus area

what does film emulsion consist of?

gelatin and silver halide crystals

what is latent image formation?

when x-rays strike and ionize some of the silver halide crystals on the x-ray film

t/f: the lead foil sheet has a pattern that will be visible if film is placed improperly

true

t/f: A speed is the slowest film and F speed is the fastest film

true

t/f: there is no rinse step between developer and fixer when using an automatic processor

true