Radiography Chapter 17: Panoramic examination

what dictates that the fastest speed screen-film comination be used to reduce the mount of radiation exposure to the patient?

ALARA

Which plane is used to position a patient correctly within the superior-inferior dimension of the focal trough?

Ala-tragus line and Frankfort plane

Prior to exposing a panoramic radiograph, a patient should be asked to swallow and rest his or her tongue flat against the palate. Expanding the tongue to fill in the oral cavity helps to eliminate a negative shadow on the resulting radiographic image.

Both statements are true

Rare-earth intensifying screens require less radiation than calcium tungstate screens to produce a latent image on film because calcium tungstate intensifying screens produce visible blue light when exposed to radiation

Both the statement and reason are correct but not related

A panoramic radiograph is valuable when diagnosing each of the following except one. A. A cyst B. An impacted molar C. recurrent caries D. Supernumerary teeth

C. recurrent caries

Film based panoramic x-ray machines use extraoral film in conjunction with a pair of intensifying screens housed within a light-tight ________

Cassette

Image receptor placed correctly to record area of interest, equal portion of maxilla and mandible recorded, occlusal/incisal plane of teeth is parallel to edge of image receptor, occlusal plane straight or slightly curved upward toward posterior, and most posterior contact point between adjacent teeth recorded

Characteristics of a quality bitewing radiograph

Image receptor placed correctly to record area of interest, entire tooth plus at least 2 mm beyond incisal/occlusal edges of crowns and beyond root apex recorded, occlusal/incisal plane of teeth is parallel to edge of image receptor, embossed dot (fil) positioned toward incisal/occlusal edge, and in full mouth survey, each tooth should be recorded at least once, preferably twice.

Characteristics of a quality periapical radiograph

Which of the following positioning errors results in an exaggerated "smile" appearance of the arches?

Chin tipped too far down

Which error results from a failure to direct the central rays of the x-ray beam toward the middle of the image receptor?

Conecutting

What image indicates an overexposed radiograph?

Dark

Which of the following panoramic image receptors does NOT need to be placed into a cassette prior to exposure?

Digital sensor

What error can be avoided by correctly using the paralleling technique?

Elongating the image of the tooth

When using the bisecting technique what errors results from inadequate vertical angulation?

Elongation

Corrective actions for not recording apical structures

Ensure that image receptor is positioned correctly into the image receptor positioner and that the patient is biting down all the way on the bite block or tab. Tip the image receptor toward the middle of the oral cavity where the midline of the palatal vault is the highest to facilitate the patients ability to securely occlude on the biteblock; increase vertical angulation.

Arches too superior result in a characteristic

Exaggerated "Frown" appearance

Arches too inferior

Exaggerated "smile" appearance

What does panoramic radiographs play a role in

Examining large areas of the face and jaws, locating impacted teeth or retained root tips, evaluating trama, lesions and diseases of the jaw and assessing growth and development

What causes film log?

Exposure to scatter radiation, use of old, expired film and chemical fume contamination

The teeth closer to the image receptor will appear blurry and magnified

False

Which of the following panoramic image receptors must be paired with intensifying screens to produce a radiographic image?

Film

What does herringbone error indicate?

Film packet was placed in the oral cavity backwards

What indicates that a film was not properly washed?

Film turns brown

estimated position between the x-ray source and the image receptor where the dental arches must be positioned to be recorded distinctly on the panoramic radiograph

Focal layer

What term is given to the area where structures will be imaged with relative clarity, whereas structures outside this area are blurred out of the image?

Focal trough

an imaginary plane or line from the orbital ridge to the external opening of the ear; will be parallel to the floor

Frank-fort plane

What can make interpreting panoramic images difficult?

Ghost images, negative shadows, and other artififacts

what describees films that stick together inside and automatic processor?

Green

What does the Cassette do for the film?

Holds the screens in close contact, and protects the film from white light exposure.

Patient not standing up straight

Improving patient posture

frankfort plane/ala-tragus line incorrectly aligned

Incorrect Superior-inferior positioning

Embossed indentification dot positioned toward apical area where it can interfere with diagnosis

Incorrect position of film identification dot

Characteristic errors result from incorrect vertical and horizontal angulations and centering the x-ray beam over the image receptor; elongaton, foreshortening, and conecut errors

Incorrect positioning of the tube head and PID

Arches too inferior (Chin tipped down) causes root apices of mandibular anterior teeth to slant out of focal trough;

Incorrect superior-inferior positioning

transfer x-ray energy into visible light ; panoramic extraoral film requires this; work in pairs; based on the principle that crystals of certain salts will fluoresce and emit energy in the form of blue or green light when they absorb x-rays

Intensifying screens

What error causes more severely overlapped proximal surface contacts between first and second molar than between the first and second premolar?

Mesiodistal projection of horizontal angulation

What may be a possible corrective action for retaking a periaplical radiograph that did not image the roots fo the teeth of interest?

Move the image receptor in toward the midline of the oral cavity, request that the patient bite down securely on the image receptor holder biteblock, ensure that the image receptor is not resting on the tongue

The panoramic PID is collimated to what shape?

Narrow slit

what will result in radiographs that are blank?

No exposure to x-rays, Placing films in fixer first, extended time in warm water rinse

image receptor was placed too far back in the oral cavity. Due to the curvature and narrowing of the arches in the anterior region, it is sometimes difficult to place the image receptor far enough anterior with out impinging on sensitive mucosa (when tori present)

Not recording anterior structures

Image receptor not placed high enough on max arch or low enough on mand arch in the pts oral cavity to image the root apices. Often occurs when a patient does not occlude completely and securely on the image receptor biteblock; in adequate vertical angulation

Not recording apical structures

image receptor is placed too high (maxillary arch) to low (mandibular arch). The use of image receptor positioners will most likely make this impossible; the cause is more often the result of excessive vertical angulation

Not recording coronal structures

image receptor was placed too far forward in the patients oral cavity. When a patient presents with a small oral cavity or a hypersensitive gag reflex it may be difficult to place the image receptor far enough posterior.

Not recording posterior structures

Most common error; incorrect rotation of the tube head and PID in the horizontal plane. Superimposition of the proximal surfaces of adjacent teeth occurs when the central rays of the x-ray beam are not directed perpendicular through the interproximal spaces to the image receptor. Overlapped contacts result when central rays ofthe xray beam are directed obliquely toward the image receptor from the distal or form the mesial ; mesiodistal overlap; distomesial overlap)

Overlapped proximal contacts

what image receptor will get lighter in response to prolonged white light exposure?

PSP plate

technique for producing a broad view image of the entire dentition of both the maxilla and mandible with surrounding alveolar bone, the sinuses, and the temporomandibular joints on a single radiograph

Panoramic radiography

What is the best way to fill in the air space between the tongue and the roof of the mouth?

Raising the flat, dorsal surface of the tongue to the palate utilizes the soft tissue image of the tongue to fill in this space and create a more even density to the image.

no radiograph should be retaken until a through investigation determines the exact cause of the error and the appropriate corrective action is identified and can be implemented is known as the?

Retake policy statement

image receptor film packet positioned so that the nack side faced the teeth and the radiation source. The radiograph will be significantly underexposed. When placed on a view box and examined closely, a pattern representing the embossed lead foil that is in the back of a film packet can be detected

Reversed film error ((herringbone error)

more sensitive to this type of fluorescent light than to radiation

Screen film

Edge of the image receptor was not parallel with the incisal or occlusal plane of the teeth or the image receptor positioner biteblock or tab was not placed flush against the occlusal surfaces. This error results when the top edge of the image receptor contacts the lingual gingiva or the the curvature of the palate when the pt occludes or when image receptor is incorrectly placed on top of the tongue

Slanting or tilted instead of straight occlusal plane

Errors that diminish the diagnostic quality of radiographs usually fall into the following categories:

Technique errors, processing errors, and handling errors

All panoramic radiographs have to 10 to 30 percent magnification. It is desirable to keep the magnification less in the anterior region than in the posterior region.

The first statement is true the second statement is false

Each of the following should be included in a policy statement on retaking undiagnostic radiographs except one a. the cause of the error must be indentified b. the solution to the problem must be established c. the corrective action can be implemented d. the radiation exposure can be reduced

The radiation exposure can be reduced

Why is a thyroid collar not used with a panoramic x-ray

The thyroid collar would get in the way of the primary beam and block the radiation from reaching the tissues

Special radiographic technique used to record images of structures located within a selected plane of tissue, while blurring structures outside the selected plane making them less visable.

Tomography

Panoramic film should be loaded into the cassette just prior to use because storing film inside cassesttes until ready for use may increase the likelihood of generating artifacts?

True

Which of these is an advantage of a panoramic radiograph as compared to an intraoral radiograph? a. a larger region is recorded b. the image is magnified c. distortion is eliminated d. definition is improved

a. A larger image is recorded

Which of the following is not a dimension of the focal trough? a. intraoral-extraoral b. anterior-posterior c. lateral (right-left) d. superior-inferior

a. intraoral-extraoral

an imaginary plane or line from the ala to the tragus; must be positioned 5 degrees down toward the floor

ala-tragus line

3 dimensions of the focal trough are

anterior-posterior, lateral or left-right, and superior-inferior or up-down.

Compressed vertebrae in slumped position absorbs radiation and appears

as a wide radiopacity at center inferior border of image

what are characteristics of a quality periapical radiograph?

at least 2mm beyond teeth crowns and root tips is recorded, occlusal/incisal edges of teeth are parallel to edge of the image receptor, image is free of magnification, distortion, and film fog or digital noise

Corrective actions for not recording posterior structures

communicate with pt to gain acceptance and assistance with placing the image receptor

Central rays of the xray beam were not directed toward the center of the image receptor and therefore the beam diameter could not completely encircle and expose the entire surface area of the receptor incorrectly assembled image receptor positioner that results in directing the central rays of the xray beam to the wrong place. not rotating a rectangular PID so that the long and short dimensions are appropriately aligned to match the long and short dimensions of the image receptor

conecut error

Each of the following is a component of a panoramic x-ray machine except one. a. rotational x-ray tube head b. cassette holder or built in digital sensor c. head positioner guides d. variable exposure timer

d. variable exposure timer

Corrective actions for not recording coronal structures

decrease vertical angulation. If correctly directing the central rays of the x-ray beam perpendicular to the image receptor when using the paralleling techniqueand perpendicular to the imaginary bisecotr when using the bisecting technique does not record enough coronal structures, decrease the vertical angulation slightly

Corrective actions for reversed film error

determine the front side of the film packet prior to placing into the image receptor holder. Read printed side of the film packet for direction

Corrective actions for elongation/foreshortening of the image

direct the central rays of the x-ray beam perpendicular to the imaginary bisector between the long axes of the teeth and the plane of the image receptor. If relying on predetermined vertical angulation settings, ensure that the patients occlusal plane is parallel, and that the midsagital plane is perpendicular to the floor

Insufficent vertical angulation with the PID not positioned steep enough away from 0 Degrees results in elongation, excessive vertical angulation with the PID positioned too steep enough away from 0 degrees results in foreshortening

elongation/foreshortening of the image (bisecting technique error)

Corrective actions for overlapped proximal contacts

examine to determine whether the overlap is more severe in the anterior or the posterior region of the image. to correct mesiodistal overlap rotate the tube head and PID to direct the central rays of the xray beam more toward the anterior teeth. Determine the contact points prior to positioning the image receptor. Place image receptor parallel to the contact points of interest so that the central rays of the xray beam will intersect the image receptor perpendicularly through those contacts.

When the dental arches are rotated to the left, the teeth on the right side will be positioned closer to the image receptor.

false

Area of image sharpness

focal trough

used to position the patient correctly

head positioner guides

narrowed appearance of teeth on the side closer to the image receptor and a magnification of the teeth on the side closer to the x-ray tube

incorrect lateral positioning- arches tilted too far to one or the other side of the focal trough

Advantages to panoramic radiographs

increase recording area, reduced patient radiation dose over a film based intraoral full mouth series of radiographs, can be performed in less time than exposure of a full mouth series of radiographs, requires minimal patient instruction and cooperation, may be substitute for pts that cannot tolerate placement of intraoral image receptors, infection control protocol minimized, aids in explaining tx plan to pts

Limitiations to panoramic radiographs

increased image distortion; amount of vertical and horizontal distortion is not constant, reduced image sharpness and detail that limits ability to detect disease in early stages, focal trough size and shape which limits recording with clarity only those structures that "fit" into image layer, increased occurance of overlapping of proximal contact areas, especially in premolar regions, superimposition of structures, length of exposure time, perception of simple procedure that may lead to inappropriate overuse

What is the greatest limitation of panoramic radiographs?

lack of image detail

corrective actions to not recording anterior structures

move the receptor in toward the midline of the oral cavity away from the lingual surfaces of the teeth of interest. this creates more room for the sensor and avoids it coming in contact with soft tissue and being uncomfortable

The most basic technique error is?

not imaging the correct teeth

diseases that may exist without signs and symptoms

occult disease

corrective actions for incorrect position of film identification dot

pay attention when placing the film packet into the film holding device to position the dot toward the incisal or occlusal region where it is less likelyy to interfere with interpretation of the image

All panoramic machines have 4 basic components

rotational x-ray tube head, cassette holder or digital image receptor, head positioner guides to assist with locating the patient within the focal trough, and exposure control panel.

What will result in black artifacts on the radiograph?

static electricity, bent film and glove powder

Corrective actions for slanting or tilting

straighten the image receptor by positioning away from the lingual surfaces of the teeth. Place the image receptor in toward the midline of the palate. utilize highest region of the palatal vault to stand the image receptor up parallel to the long axes of the teeth.

Which of these is a limitation of a panoramic radiograph as compared to a full mouth series of intraoral radiographs? a. larger radiation dose to the patient b. increased time required to obtain the radiographic image c. superimposition of structures that may make interpretation difficult d. requires an increase in patient instruction and cooperation with the procedure.

superimposition of structures that may make interpretation difficult

Controls the penetrating ability of the beam

the kVp

The open air space between the tongue and the roof of the mouth will create a large radiolucency on the image that will obscure

the root apices of the maxillary teeth

What is the term given to the technique in which a slice of tissue is exposed distinctly, whereas structures outside the designated area are blurred out of the image?

tomography

Which of the following positions within the focal trough results in anterior teeth that are blurry and narrowed in size?

too far foward

Rectangular collimation is recommended when using digital sensors because a rectangular PID reduces more scatter radiation than a circular PID

true

What will result in radiographs that are too light?

underexposing; old, expired film, underdeveloping.

If a patient leaves lips open what will happen to the pano?

will create an image that can mimic caries of the anterior teeth

The x-ray tube used in panoramic x-ray machines generates electrons to produce

x-ray energy

When the film is sandwiched tightly between a pair of two intensifying screens the ________ cause the _______on the screens to ______ and return the emitted light to the film emulsion to produce the ___________

x-rays; crystals; fluoresce; Radiographic image