Dental Terminology Ch. 9

Radiography

X-rays

Radiant energy waves that are produced, charged and emitted from a common center in the dental radiation tube, charged electrons are tiny energy bundles or waves of photons with extremely short wavelengths that are used to penetrate matter and expose photographic film surfaces, discovered by Wilhelm Conrad Roentgen, and sometimes called Roentgen waves

X-ray tube

AKA Vacuum tube, produces X-rays

Cathode

(negative pole) Electrode in the vacuum tube that serves as the electron source

Filament

(fine thread) Tungsten coil in the cathode focusing cup thhat generates the electrons

Anode

(positive pole) The target for the electron barrage to convert thte electron force into photons

Focal spot

Target area where rays are projected to make the primary beam, or central beam; the smaller focal spot produces a better image

Collimator

(to align) A device used to regulate the size of the beam leaving the tube in parallel rays, helping to avoid stray radiation, also termed a diaphragm, it is usually shaped similar to a lead washer on the connecting end of the PID that also has lined walls to assist collimation

PID

Position indicating device

Aperture

(Opening or port) Opening in the lead collimator disk that regulates the size of the primary beam

Filter

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

Three types of filtration

Inherent, added, and total filtration

Inherent filtration

All filtration (tube wall, insulating oil, aluminum disks) devices that filter weak, longer wavelength X-rays

Added filtration system

Filtration placed outside the tube head to meet safety standards

Total filtration

The sum of the inherent and added filtration, expressed in millimeters of aluminum equivalent

Milliampere control

(mA) AKA milliampere; an increase in milliamperage increases the number of electrons available and darkens the radiograph

Kilovolt Power

(kVp) Controls the force that attracts the electrons to the anode; helps to determine the penetrating power and the quality/energy of the radiation rays

Exposure time

Duration of the interval during which current will passthrough the X-ray tube; this period may be stated as fractions of a second or impulses, (50 pulses to a second) the amount of exposure that a patient actually receives is measured in milliampere seconds

(mAs) (mA x exposure time = mAs)

Target film distance

(source-film distance, or focus-film distance) distance of the film surface from the source of radiation

Target-object distance

(source-object distance or focus-object distance) distance between the anode target and the object to be radiographed

Film speed

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

Different types of X-ray radiation

Are generated during radiography

Primary radiation

Central ray of radiation emitting from the tube head and PID. Primary radiation is the desired radiation and is used to expose radiographic 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 or diffused in all directions, becoming attenuated (weakened) or another form of secondary radiation

Stray radiation

Aka leakage, any radiation other than the useful beam produced from the tube head, a faulty or broken tube head may be the source of stray radiation

Remnant radiation

Radiation rays that reach the film target after passing through the subject part being radiographed, these rays form the latent image on the film emulsion

Sensitivity

Ability of X-rays to penetrate and possibly ionize, reproductive cells are more radiosensitive than the radioresistant body tissues (somatic) cells, younger cells are more sensitive than other, thicker cells

Cumulative effect

Long-term outcome of radiation, Repetition increases and intensifies the ionizing effect on cells for a buildup of damage, the latent period of exposure is the time interval between the exposure and the effect or detection

Mutation effect

Abnormal growth or development due to radiation causing a genetic change

2 types of X-radiation exposure that will damage the body cells are

Acute and chronic radiation exposure

Acute radiation exposure

Radiation occurring from a massive short-term ionizing dose, such as an accidental exposure or explosion of radiation material

Chronic radiation exposure

Accumulated radiation cell damage from continual or frequent small exposures absorbed over a period of time (thus the need for questioning the patient as to when the last X-ray was taken)

Roentgen (R)

The basic unit of exposure to radiation; the amount of X-radiation or gamma radiation needed to ionize 1 cc of air at standard pressure and temperature conditions

Rad (radiation absorbed does)

The basic unit of absorbed radiation does equal to 100 ergs per gram of tissue or 1 gad = cGy

Rem (roentgen equivalent measure

The unit of ionizing radiation needed to produce the same biological effect as 1 roentgen of radiation

rbe (relative biological effectiveness)

Unit of measurement used to determine amount of biological absorption effects on body tissues by different types of radiation energy

Coulomb

International electromagnetic measurement abbreviated as C; 1 C per kilogram (C/kg) is equal to 3880 roentgens

Maximum permissible dose (MPD)

Highest rate of exposure permissible for the occupationally exposed person, formula is (5 rem per year) - {age-18} X 5 rem per year + MPD

Erythema dose

Radiation overdose that produces temporary redness of the skin

ALARA

(as low as reasonably achievable) A policy of using the lowest amount of radiation exposure possible, measures to accomplish this include proper exposure and protection aids, use of fast films, good techniques in exposure and developing, questioning the patient regarding recent exposure, and the correct calculations or control settings

Dosimeter

(giving measure) operator’s radiation-monitoring device with ionizing chamber or a device to indicate exposure and measure accumulated doses of radiation, available in the form of a film badge, pen, ring, and so on

Lead apron/tyrocervical collar

Patient apparel with lead protection for genetic cells in the torso and the thyroid glands in the cervical area

Lead barriers, shields

Devices used by operators to block out scattered radiation

Phantom

Practice mannequin containing tooth and head structures to imitate the actual condition, a popular model is DXTTR, aka dexter

Periapical Film packet

Size 0 (pedodontic size), 1 (adult anterior), or 2 (adult anterior and posterior); used for the intraoral periapical view of the entire tooth or teeth in a given area along with adjacent tissues and oral structures, this film may also be placed in a device or loop to expose an intraoral bitewing view and may be ordered in a double film packet, if desired

Bitewing film packet

(aka interproximal radiograph, size 3): film used to record crown and interproximal views of both arches while in occlusion; used intraorally with attached bite tab, other film sizes may be adapted to accomplish this task

Film speeds

Film are rated A to F according to the amount of exposure needed, with A needing the most time, aka D-Ultra-speed, E-Ektavision, and F-Insight

Occlusal film packet

Size 4; film that may be used intraorally or extra orally to expose large areas, these film packets may contain more than 1 film and are marked and color-coded to identify the amount of film enclosed

Extraoral films

Radiographs exposed outside the oral cavity; larger in size and loaded in a film cassette or wrapped for protection from light rays

Cephalometric films

Aka headplates, these extraoral radiographs of the head are used in orthodontic, oral surgery, and sometimes in prosthodontic dentistry

Cephalostat

A device used to stabilize the patient’s head in a plane parallel to the film and tat right angles to the central ray of the X-ray beam, it is used for large radiographs of the head

Panoramic radiograph

A special radiograph capturing a view of the entire dentition with the surrounding structures on one film, the extraoral film is placed in the machine’s cassette and rotates around the patient at the same speed as the tube head rotation, providing a panoramic view, popular in orthodontics and oral surgery

What do panoramic and cephalographs have in common?

Completed using special mounted machines

Intensifying screen

A lining of calcium tungstate phosphors or rare earth within the cassette that gives off a bluish light (calcium tungstate) or green glow (rare earth) when exposed to radiation

CCD

(charge coupled device) sensor that is a solid-state sensor that may or may not be wired to the computer workstation, the sensor and sensor wire are barrier wrapped and inserted into a positioning device for insertion and exposure in the mouth, the same placement and alignment technique used for conventional film exposure are applied

PSP

(photostimulable phosphor device) Is a cordless, indirect sensor plate that absorbs radiation to complete a latent image

Radiograph Image Receptor Comparison

Contrast radiography

Variations in shades from black to white, a radiograph exhibiting many variations in shades is considered to possess long-scale contrast, increased kilovoltage helps to produce this effect

Density/brightness radiography

amount of film blackening associated with the percentage of light transmitted through a film, an increase or decrease in density is accomplished by an increase or decrease in milliamperage and exposure time (mA/second)

Detail radiographysmoothness

Point-to-point delineation or view of tiny structures in a radiograph image, proper exposure, handling factors, and kVp selection provide good detail

Definition/smoothness

Outline sharpness and clarity of image exhibited on a radiograph, movement of the film, patient, or tube head is the most common cause of poor definition or fuzzy outline called Penumbra (nearly shadow) proper digital machine filtration of electronic noise can improve the sharpness and smoothing of the digital image

Radiolucent

(ray shine) describes a radiograph that appears dark, or the ability of a substance to permit passage of X-rays, thereby causing the radiographic film to darken

Radiopaque

(ray dark) The portion of the radiograph that appears light, or the ability of a substance to resist X-ray penetration, thereby causing a light area on the film

Two basic techniques used by conventional and digital methods for exposure of intraoral radiographs

Bisecting angle and paralleling

Bisecting angle

The central X-ray beam is directly perpendicular with an imaginary bisecting line of the angle formed by the plane of the film and long axis of the tooth, aka the short cone technique

Paralleling

The film packet is placed parallel to the long axis of the tooth and at a right angle to the central X-ray beam, aka the extension cone or tight-angle technique

Sagittal plane

AKA midsagittal plane; imaginary vertical line bisecting the face into a right and left half

Ala-tragus line

Imaginary line from the ala (wing) of the nose to the tragus, center of ear, this line is important for positioning the patient in the bisecting-angle technique

Frankfort Plane

Imaginary line from the tragus of the ear to the floor of the orbit that is used to align the maxillary arch parallel to the floor; used mostly for extraoral films, many machines that expose large extraoral films and digital images have a stabilizing chin rest or an aiming light to ensure this directional position.

Positive angulation

Angulation achieved by positioning the PID downward; also called plus angulation, maxillary exposures are incisors (+40 degrees), cuspids (+45 degrees), bicuspids/premolars (+30 degrees), and molars (+20 degrees)

Negative angulation

Angulation achieved by positioning the PID upward; aka minus angulation, mandibular exposures are incisors (-15 degrees), cuspids (-20 degrees), bicuspids/premolars (-10 degrees), and molars (-5 degrees)

Zero angulation

Angulation achieved by PID placement parallel to the floor

Horizontal angulation

Direction of the central X-ray beam in a horizontal plane, the central beam must be placed perpendicular to the film front and teeth alignment, the error observed with improper horizontal angulation is called overlapping or cone cutting

Vertical angulation

Direction of the central X-ray beam in an up or down position, improper vertical angulation results in foreshortening or elongation errors.

PID

Position indicated device, formerly called a cone; may be a long cone (12-16 in) or a short cone (8 in); may be a round or rectangular, open-ended tube

Film-holding instrument

Device used to place and retain the film or sensor in the oral cavity during exposure,

VIP

Versatile Intraoral Positioner, by UpRad

Rinn BAI

For the bisecting angle technique

XCP

Extension Cone Paralleling device

Rinn XCP-DS

for sensor use

Rinn XCP

For endodontic views

Colors for locator or aiming rings

blue, yellow, red, green

Blue for locator or aiming rings

anterior placement

Yellow locator or aiming rings

Posterior placement

Red locator or aiming rings

Bitewing placement

Green locator or aiming rings

Endodontic placement

Biteblock

A device inserted between the teeth to hold the film during exposure; made of foam, wood or plastic

Individual film holder

A grip device that will hold 1 film or 1 sensor for exposure in the mouth, mostly used in a small mouth or difficult areas, the loaded film holder is put into position and help by the patient’s bit or finger pressure

Bite loop/tab

Paper tab or a celluloid circle placed around periapical film, enabling the film to be used in a bitewing position, this combination is used in place of a commercially manufactured interproximal film, some bite loops are constructed to assist with stabilizing and holding the digital sensors in the film-holding device

Film-safe container

A lead-lined container used to hold exposed films until processing; protects the film from exposure to scattered or secondary rays during exposure of films

Full mouth survey (FMS or FMX)

Multiple exposures of the oral cavity showing crown and root area in a series of radiographic views, when arranged in proper sequence, these films or images give a survey or view of the condition of the entire mouth

Bitewing survey (BWS or BWX)

Two or four film exposures of the posterior view to observe the crowns of maxillary and mandibular posterior teeth, anterior bitewing exposure is also possible

Edentulous survey

Radiographic survey of a patient without teeth

Radiograph processing

A procedure for bringing out the latent image on a film and making the exposure permanent, involves developing, rinsing, fixing, washing, and drying

Developing in film processing

Chemical process using the chemical elon to bring out contrast and another chemical, hydroquinone, to show contrast in films, developing brings out the latent image on the film’s silver halines that were affected or darkened by radiation

Accelerator in film processing

Solution used to swell the film emulsion during the processing

Activator in film processing

Solution used to aid other chemicals in the processing activity

Replenisher solution in film processing

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

Rinsing in film processing

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

Fixing in film processing

Chemical process that stops the developer action and “fixes” the image, making it permanently visible