Radiology, image characterisitcs, localization technique

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radiolucent

dark or black, air space is this

radioopaque

light or white, structures are dense adn absorbe or ressit passage of xray beam, enamel, dentin, bone

the quality of dental radiographs is determined by its

image characterisitcs, ideal radiograph is not too light or too dark

diagnostic radiograph

great deal of information, exhibit proper density and contrast, have sharp outlines, are of same shape and size of object radiographed

visual characteristics

density and contrast

density

overall blackness or darkness, heavier deposits of black silver particles causes the darkness

degrees of blackness is

contrast

Influency factors

Milliamperage(mA), kVp, exposure time, and subject thickness

milliamperage

produces more x-ray that expose the film and increases film density. this is increased, density increase, the darker the image

operating kVp

increase this, increase film density by increasing the mean or average energy of x-rays adn by producing x-ray of higher energy. increase this, increase density, darker image

exposure time

increase exposure time, increases film density by increasing total number of x-ray that reach film surface. increase this, increases density, causes darker image

subject thickness

few x-rays reach film in patient with increased amount of soft tissue or thick, dense bones, less density and appears lighter. adjustments in mA, kVp, exposure time compensate for variations in size of patients and subject thickness

high contrast

very dare areas and very light areas, the two are strikingly different. black and white.

low contrast

many shades of gray.

film contrast

refers to the characterisitcs of film that influence radiographic contrast, chararateristics that influence contrast include the inherent qualities of the film and film processing

subject contrast

characteristics of teh subject that influence radiographic contrast, this is determined by thickeness adn density and composition of subject. can be altered by increasign and decreasing kVp

Only one exposure factor has direct influence on the contrast of dental radiograph, this one factor is

kVp, increasing kVp, affects film contrast, by producing higher energy x-rays. xrays with higher energy are better able to penetrate tissue. appears as varying shades of gray, low contrast. higher kvp, lower contrast, lower kvp, Higher contrast

scales of contrast

range of useful densities seen on dental radiograph. has short scale and long scale

short-scale contrast

shows only two densities areas of black and white,, lower kVp, high contrast

long scale contrast

dental radiograph that exhibits many densities or many shades of gray, has long contrast scale, higher kVp, lower contrast

stepwedge

uniform layered thickness to show long scale and short scal contrast, made of aluminum

geometric characteristics

sharpness, magification, distortion, must be minimized to produce acurate radiographic image

sharpness

refers to the capability of the x-ray film to reproduce the distinct outlines of an object. small details of an object are reproduced on dental radiograph

penumbra

fuzzy, unclear area that surrounds a radiographic image. unsharpness, or blurring, edges of radiographic image

umbra

shadow

influencing factors of sharpness

focal spot size, film composition, movement

focal spot

tungsten target of anodes, small area converts bombarding electrons into x-ray photons.

the smaller the focal spot

the sharper the image apears

the larger the focal spot

the loss of image sharpness

filim composition

the composition of the film emulsion influences sharpness. sharpness is relative to the size of the crystals found in film emulsion. faster film contains larger crystal that produce less images sharpness,

slower filim contains

smaller crystals that produce more image sharpness

movement

influences film sharpness. loss of image sharpness occurs if either the film or the patient moves during x -ray exposure
this results in unsharpness

magnification

radiographic image that appears larger than the actual size of the object it represents

influencing factors of magnification

target film distance, object film distance

target-film distance

is distance between the source of x-rays(focal spot on the tungsten target) and the film. when longer PID used, more paralllel rays from middle of xray beam strike object rather than diverging x-ray from periphery of beam.
longer PID results in less image magnification

shorter PID and target film distance results in

more image magnification

object film distance

distance between the object being radiographed (the tooth) and the dental x-ray film. tooth and film should always be placed close together as possible.

the closer the tooth to the film

less image enlargment there will be on the film.

increase in object film distance results in an

increase in image magnification, this is bad

distortion

variation in true size and shape of the object being radiographed. results from unequal magnification of different parts of the same object, improper film alignment or beam angulation

influencing factors of distortion

object film distance and x-ray beam angulation

object film distance

minimize dimensional distortion, ojbect and film must be parallel to each other, not parallel, angular relationship results,

angular relationship produces

variation of distances between the tooth adn film that results in distored image, distorted image may appear too long or too short

x-ray beam angulation

minimize dimensional distortion, xray beam must be directed perpendicular to the tooth and the film, central ray of the x-ray beam must be as nearly perpendicular to the tooth and film as possible to record adjacent structures to their true spatial relationships

to limit distortion

film and tooth are positioned parallel to each other, and xray beam is directed perpendicular to the tooth and film

to limit magnification

the longest target film distance and shortest object film distance are used

portion of a processed radiograph that appears dark or black is termed

radiolucent

portion of a processed radiograph that appears light or white is termed

radiopaque

which of the following appears most radiolucent on dental radiograph?

air space

an example of a radiopaque structure seen on dental x-ray is

bone, enamel and dentin

the overall blackness or darkness of a dental radiograph is termed

density

increasing the mA will cause

an increase in density, the film apears darker

increasing the operating kVp will cause

increase in density, film appears darker

increasing exposure time will cause

an increase in density, film appears darker

dental patient has thick soft tissues and dense bones. to compensate for this increase in subject thickness and provide a film of diagnostic density, the dental radiographer may

increase exposure time, increase mA, increase kVp

the difference in the degress of blackness between adjacent areas on a dental radiograph is term

contrast

when viewed on a light soruce, a dental radiograph that demonstrates many shades of gray is said to have

low contrast

when views on a light source, a dental radiograph that demonstrates very dark areas adn very light areas is said to have

high contrast

the one exposure fator that has a direct influence on the contrast of a dental radiograph

is kVp

the type of contrast preferred in dental radiography is

low contrast

the stepwedge is used for

demonstrations of longscale and shortscale, monitor quality control of film processing, demonstrate film densities

the capability of the x-ray film to reproduce distinct outlines of an object is termed

sharpness

the unsharpness or blurred edges seen on radiographic image is termed

penumbra

geometric characteristic that refers to a radiographic image that appears larger than its acutal size is term

magnification

a variation in the true size and shape of object being radiographed is termed

distortion

Principles of shadow casting

1. source of radiation should be as small as possible
2. tube to ojbectdistance shoudl be as great as possible
3. object to film distance should be as small as possible
4. film shoudl be parallell to the long axis of teeth
5. the central ray should be perpendicular to the film
6. the central ray should be directed between the teeth
7. the x-ray tube, patient, and film should be motionless

umbra

shadow

paralleling obeys most all principles of shadow casting except which principle?

principe #3, object to film distance should be as small as possible. this is only principle of shadow casting that bisecting technique does better

method used to locate the position of a tooth or object in the jaws

localization technique

pupose and use of localization technique

two dimensional picture of 3 dim object, depicts superior-inferior and anterior posterior relationships, but doest not depict buccal lingual relationship

localization technique can locate the following

foreign bodies, impacted tooth, unerupted tooth, retained roots, root positions, salivary stones, jaw fractures, broken needles, and instruments, filling materials

two basic technique are used to localize objects:

buccal object rule and right angle technique

what rule governs the orientation of structure portrayed in two radiographs exposed at different angulations
1st use proper technique, 2nd change verical and horizontal angulation

buccal object rule(slob)

when dental structure or obejct seen int eh second radiograph appears to have moved in the same direction as teh shift of teh PID, the structure or object in question is positioned to teh

lingual, same=lingual

when dental structure or object seen in second radiograph appears to ahve moved in direction opposite the shift of the PID, the structure or object in question is positioned to teh

buccal, opposite=buccal mostly maxillary

another rule for orientatino of structures seen in two radiographs

right angle technique

superior inferior and anterior posterior relationship for the

right angle technique

how is technique used

occlusal film (anterior posterior)is exposed directing the central ray at a right angle, or perpendicular(supeior inferior) to the film, mainly for located on mandibule

What are 3 main uses of dental radiograph

detect disease, confirm disease, legal document

filmless imaging system, method of capturing radiographic image using a sensor, breaking it into electronic pieces, and presenting and storing the image using computer

digitial radiography

Radiation then onto film, then developing process bring latent to visible, then making the radiograph is called

radiology imaging

radiation onto sensor(phosphur plate), making digital image to visible image, scanned on computer

digital imaging

the greater the pixels the greater teh

sharpening

is a solid state detector that contains silicon chip witha n electronic circuit embedded in it, is senstive to xrays or light

CDC, change coupled device. our is phosphorus

the cdc has this part instead of silver crystals

pixels

imaging is how many impulse per second compaired to conventional 60=sec

1/100 sec. 100 impulse=sec
is 50-80% less radiation

two types of digital imaging

direct and storage phsophur(indirect)

Direct uses a

CDC,

indirect uses a

PSP, storage phosphur, phot stimulate phosphur image

have wireless rare earth phosphur coated plates

indirect digital imaging

phosphur plate store the ___image

latent image

the _____stimulates the fluorescent signal which is converted into a digital image

laser scanner

measurement of the ability of digital system to capture the detail in an image

line pairs/millimeter

how are existing readiographs converted to digital image

cdc camera scans radiographs, digitizes the info, sent to computer, view on monitor or printed, archived old records

how many linepairs does digital radiograph have?

12-20 ln pairs/mm, beginning at 10lp mm, new machine 20+

digital imaging can detect how many shade of grade scale resolution

256 shades compared to 16-25 shades of radiography, and human eye of 32 shades

computer enhancements are

colorization, zoom, digital subtraction, density, decay sensor

advantages to digital imaging

superior gray scale, reduction exposure speed of viewing, decrease in equipment costs(processing), efficiency, enhancement of image, patient education tool

disavantages

cost, image quality, sensor size, infection cotnrol, legal issue, manipulated images

Legal issue in radiology laws

radiation control for health and safety act 1968
consumer patient radiation health and safety act 1981
invidual state and local laws

risk management policies and procedures

instructor's approval of radiographic selection, sign your clinic book, fill out the exposure record
informed consent of patient, dentist's authorization

standard of care is the

quality fo care that is provided by dental practioners in a similar locatily under the same or similar conditions, negligence if not follow standard of care

documentaiton

informed consent, signed treament plan, number and type of radiographs to be taken
number and type of radiographs
exposure record, treatemtn record
diagnostic information obtained, recorded by dentist, referrals indicated

ownership of radiographs

dentist or owens community college
patient may request radiographs
copy made if second copy unavailable
must be writeen in record
forward to their dentist

refusal of radiographs

patient refusal of dental radiographs, compromises the patien'ts diagnosis and treatment
the patient can not sign a relsease consent to negligent care is invalid
section instructor will assist you with any difficult clients

patient management

convey confidence, be prepared, you know what you are doing!

helpful hint to avoid gag reflex

never metion gag!! do reasure the patient, begin anterior, do suggest breathing, do try to distract the patient. do try tactile stimulation, do use topical anesthetic, avoid the palace, demonstrate placement

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