Dofka Dental Terminology Chapter 9 - Radiology

radiant

energy waves produced or given off by a source

x-ray tube

also known as a vacuum tube, produces x-rays

cathode

negative pole, electrode in the vacuum tube that serves as electron source

filament

tungsten coil in the cathode focusing cup

anode

positive pole, target for the electrons

focal spot

target area where x-rays are projected to make the primary beam, or central beam, small spot produces better image

collimator

device used to regulate the beam's exit from tube into parallel rays and avoid stray radiation, usually made of a lead washer

aperture

opening in the lead collimator disk that regulates size of primary beam

filter

aluminum disks that are placed between collimator and the exit of the window of the tube to absorb weak radiation

inherent filtration

all filtration (tube wall, insulating oil, aluminum disks) that filter weaker, longer-wavelength x-rays

added filtration

filtration placed outside the tube head to meet safety standards

total filtration

sum of inherent and added filtration, express in mm of aluminum equivalent

milliampere control

one-thousand of an ampere, increase amount of electrons available and darkens radiograph, known as mA

kilovolt power

controls force that attracts electrons to anode, helps determine penetrating power and energy of the radiation rays

exposure time

duration f of the interval during which current will pass through the xray tube, stated as fractions or impulses

target-film distance

distance of the film surface from the source of radiation

target-object distance

distance between the anode target and the object to be radiographed

film speed

A (slowest) to F (fastest) speed, faster film requires less radiation exposure time for patient

primary radiation

central ray of radiation emitting from the tube head and PID, desired radiation and is used to expose radiographapic film

secondary radiation

radiation given off from other matter that is exposed to the primary beam

scattered radiation

radiation deflected from its path during its passage through matter, may be deflected and diffused in all directions, becoming weakened

stray radiation

also called leakage, any radiation other than useful beam produced from the tube head

remnant radiation

radiation rays that reach the film target after passing through the subject to be radiographed, forms latent image on the film emulsion

sensitivity

ability of x-rays to penetrate and possibly ionize

cumulative effect

long-term outcome of radiation, repetition increases and intensifies the ionizing effect on cells for a buildup of damage

latent period

interval between exposure and the effect

mutation effect

abnormal growth or development as a result of radiation causing a genetic change

acute radiation exposure

ration occuring from a massive short-term ionizing dose, such as accidental exposure

chronic radiation exposure

accumulated radiation effects from continual or frequent small exposures absorbed over a period of time

ALARA

as low as reasonably achievable, policy of using the lowest amount possible

maximum permissible dose

highest rate of exposure permissible for the occupationally exposed person

roentgen

basic unit of exposure to radiation

rad

unit of absorbed radiation dose equal to 100 ergs per gram to gram of tissue

rem

unit of ionizing radiation needed to produce same biological effect as one roentgen (R) of radiation

erythema dose

radiation overdose that produces temporary redness of the skin

dosimeter

radiation monitoring device to indicate exposure and measure accumulated doses of radiation, can be in form of film/badge/pen, ring

lead apron/thyrocervical collar

patient apparael with lead protection for genetic (sex) cells and thyroid glands

lead barriers/shields

devices used by operators to block out scattered radiation

periapical film packet

used for view of entire tooth or teeth

size 1 film

adult anterior film

size 0 film

pedodontic film

size 2 film

adult posterior film

bitewing film packet

used to record the crown and interproximal views of both arches while in occlusion, can be size 3 film

occlusal film packet

may be used intraorally or extraorally, size 4 film

extraoral films

radiographs exposed outside the oral cavity, larger in size, can be incased in film cassettes (if not digital) panoramic or cephalometric films

cephalometric

also called headplates, side view, used in ortho, oral surgery and sometimes prosthetic dentistry

cephalostat

device used to stabilize patients head in a plane parallel to the film

panoramic radiograph

produces entire dentition with surrounding structures on the film, extraoral film

intensifying screen

layer of fluorescent crystals within cassette that give off bluish light when exposed to radiation

contrast

variations in shades form black to white, increase in kVp helps to produce this effect, long scale contrast exhibits many variations in shades

density

amount of film blackening, increase or decrease in density is accomplished by increase or decrease in mA

detail

point-to-point delineation or view of tiny structures in a radiograph image.

definition

outline sharpness and clarity of image, movement of film or patient or tubehead is most common cause of fuzzy outline

penumbra

poor definition or fuzzy outline of forms, caused by movement

radilopaque

the portion of the radiograph that appears light, the ability of a substance to resist x-ray penetration causing a light area on a film

radiolucent

the portion of the radiograph that appears dark, the ability of a substance to permit passage of x-rays causing the area on the film to darken

bisecting angle

central x-ray beam is directly perpendicular with an imaginary bisecting line of the angle formed by the plane of the film and the long axis of the tooth

paralleling

film packet is placed parallel to the long axis of the tooth and at a 90 degree (right) angle to the film

CCD

charged couple device-solid state sensor that may or may not be wired to a computer work station, barrier-wrapped, inserted into mouth for exposure, once exposed, information is transported to workstation and image is viewable

PSP

photostimulable phosphor device (also called phosphor storage plates) indirect sensor storage plate that absorbs radiation to complete a latent image, after exposure, the plate is placed into a scanner to transfer image to patient's dental records

indirect dental radiography dental image

xray image already processed by usual method, scanned by adaptor, or digital camera can record picture of film then transfer image to database

electronic image processing

operators manipulation of the image, can consist of changing contrats, brightness, reverse image, grayness, compare or obtain information

digital subtraction radiography

digital comparison of the image to a previous radiograph, subtracting all that is the same and comparing the remainder

sagittal plane

also called midsaggital plan-imaginary vertical line bisecting the face into right and left half, helps determine position of the patient during exposure

ala tragus line

imaginary line from ala (wing) of nose to the tragus (skin projection anterior to acoustic meatus) center of the ear, aids in position patient in bisecting angle technique

horizontal angulation

direction of central x-ray beam in a horizontal plane, must be placed perpendicular to the film front and teeth alignment, error is overlapping and/or cone-cutting

vertical angulation

direction of central x-ray beam in up and down position, improper results in elongation or foreshortening

negative angulation

angulation by positioning the PID upward, mandibular exposures are made with this, also called minus angulation

positive angulation

angulation by positioning the PID downward, maxillary exposures are made with this, also called plus angulation

PID

position indicating devices formerly called a cone, long cone 12-18 inches, short cone 8 inches

film-holding instrument

device used to place and retain the film during exposure

biteblock

a device inserted between the teeth o hold the film during exposure, made of foam, wood or plastic

bite loop/tab

paper tab or celluloid circle placed around the periapical film, enabling film to be used in a bitewing position

film safe container

lead lined container used to hold exposed film until processing, protects it from exposures or scattered xrays

full mouth survey

multiple exposures of the oral cavity showing crown and root area in a series of radiographic views, gives view of entire mouth when mounted

bitewing survey

two or four film exposures of posterior view to observe crowns of maxillary and mandibular posterior teeth

edentulous survey

radiographic survey of a patient without teeth

developing

chemical process to bring out contrast on films, developing brings out th latent image on the films silver halines that were affected or darkened by radiation

accelerator

solution used to swell the film emulsion during the processing

activator

solution used to aid other chemicals in the processing activity

replenisher solution

super concentrated developing solution that is added to the developing tank to restore fluid levels

underdeveloping

insufficient processing from weak chemicals, too short of time or too cold of temperature resulting in light, difficult to view films

overdeveloping

overprocessing that results in radiographs that are too dark, from too long of time, too high of temperature

rinsing

water bath used to remove chemical liquids from films during solution exchanges

fixing

chemical process that stops the developer actions and "fixes" the image making it permanently visible

drying

procedure to dry films after chemical and water baths

safelight

special light or filtered light that can remain on during the developing process

duplicating radiograph

using cabinet like unit and special duplicating films to make a duplicate exposure of already processed radiograph

horizontal window

used to place posterior film in a mount

vertical window

window in the mount used to place anterior film

bitewing window

used to place bitewing exposures

identification dot

depressed or raised area on the surface of the film. convex-dot out xrays read R to L, concave-dot in-xrays read L to R

viewbox

box or wall mounted frame with fluroscent lights used to view xrays

elongation

image of tooth appearing longer, caused by insufficient vertical angulation

foreshortening

tooth structures appear shorter than actual size, caused by excessive vertical angulation

overlapping

film error showing distortion of overlap of crowns of adjacent teeth, cause by improper horizontal angulation

cone-cutting

blank area produced by improper placement of central beam, causing lack of exposure, PID not being centered properly on film

reticulation

crackling of film emulsion caused by wide temperature differences between processing solutions, gives a stained glass effect

fog

darkening of or blemish on film that may be caused by old film, old or contaminated solutions, safelight issues, scattered radiation or improper storages of films

herringbone effect

fish-bone effect on the film surface resulting from improper placement of film, film placed in backward position shows a lead foil backing in the visual image.