Chapter 22: Panoramic Imaging

How do you correctly position the pt.?

*Instruct the pt. to bite on the bite guide with the anterior teeth* occluding edge to edge or place the chin completely forward into the chin rest and against the forehead rest.

What are the advantages of panoramic radiography?

- May be performed on pt's who can not tolerate placement of an intraoral films/sensor packet -Requires minimal pt. instruction and cooperation -Infection control protocol minimized -Mounting time is eliminated -Aids in explaining treatment plan to pt's.

What are the disadvantages of panoramic radiography?

-*The size and shape of the focal trough is pre-determined* by the manufacturer, therefore not all pt's will image equally well. -*Superimposition of structures* (e.g. the spinal column) may make interpretation difficult. -*Soft tissue shadows* present on the resulting image. May mimic pathology -*Ghost images* present on the image may hide pathology.

What are the disadvantages of panoramic radiography?

-Increased *image distortion* -*Reduced image sharpness* -The amount of vertical and horizontal *distortion is not constant* - it varies from one part of the radiographs to another. -*increased occurrence of overlapping* of the proximal contact areas, especially in the *premolar* region -*Focal trough size and shape limits imagery* to only those structures which "fit" into the image layer. Teeth with labial or lingual tilting may not image well.

What are the advantages of panoramic radiography?

-Increased coverage of supporting structures of the oral cavity -Reduced pt. radiation dose over an intraoral full mouth series of radiographs -Can be performed in less time than the exposure of a FMX -Simple procedure to perform -Minimal pt. discomfort

How do you prevent artifacts and Ghost images?

-Make sure all objects made of metal or dense material is removed. -Glasses necklaces, earrings, piercings, chin rest, etc

How should the lead apron be worn for a panoramic radiograph?

-Make sure that the lead apron is not interfering with the x-ray beam -Do not use a thyroid collar and make sure the apron doesn't ride too high p the neck

What are the disadvantages of panoramic radiography?

-Not useful in detecting incipient carious lesions -Not useful in detecting early periodontal changes -Simple procedure may be overused inappropriately -Length of exposure time may limit its use on young children and other pt's who cannot remain still throughout the exposure cycle. -Cost of panoramic unit is significant

What does the superior-inferior position consist of?

-The Frankfort plane -The ala-tragus line -Superior-inferior position -Superior-inferior positioning error

What are the components of the pano x-ray machine?

-Tube head -Rotation Center -Panoramic Rotational Systems. -Plane of focus - Focal trough

This component is similar to an intraoral component; as each has a filament used to produced electrons and a target used to produce x-rays.

-X-ray tubehead (A)

List three machine parts that may be recorded on panoramic radiographs.

1 Chin rest 2. Side head positioner guides 3. Biteblock

What are the 5 pt. positions?

1. Anterior-Posterior position (anterior arch) 2. lateral position (posterior arch) 3. Superior-inferior position (chin position) 4. Patient postion 5. Patient posture position

What is wrong in this image?

1. Artifact 2. Ghost image

What are the 3 panoramic rotational systems?

1. Double centered rotational system 2. Triple centered rotational systems 3. Moving-center rotation

What are the purposes and uses of panoramic imaging?

1. Examining large areas of the face and jaws. 2. Locating impacted teeth or retained root tips 3. Evaluating trauma lesions, and diseases of the jaws 4. Assessing growth, eruption pattern, and development

List three air spaces that may be recorded on panoramic radiographs.

1. Palatoglossal 2. Nasopharyngeal 3. Glossopharyngeal

What are 2 things to take into consideration when aligning the midsagittal plane?

1. Tilting 2. Rotation

Why are 2 separate exposures necessary?

2 separate exposures are necessary resulting in a "split-film" image.

Identify the approx. age of the pt.

6-7 Mand 1st molars are erupted

What is the incorrect position?

Anterior teeth appear narrowed and blurred on the panoramic image when the pt's teeth are positioned *too far forward* on the bite block.

What is the incorrect position?

Anterior teeth appear widened and blurred on the panoramic image when the pt's teeth are positioned *too far back* on the bite block

________ 18All jewelry (earrings and necklaces) must be removed before exposure.

Both panoramic and intraoral imaging

________ 9The tubehead contains a filament used to produce electrons and a target used to produce x-rays.

Both panoramic and intraoral imaging

What can an open lip line mimic?

Can mimic caries of the anterior teeth.

A device that is used to hold the extraoral film and intensifying screens

Cassette

What is wrong in this image?

Cervical spine is slumped -Could have been eliminated by having the pt. sit straight and align or stretch the neck

This is used in the panoramic x-ray, however, differs from the one used in the intraoral x-ray tubehead

Collimator

What will be apparent if the pt's head is tilted?

Diminution (reduction in size) will be apparent on the side closer to the film, and magnification will be apparent on the side closer to the x-ray tube head.

Which rotational system has 2 rotational centers: 1 for the left and 1 for the right side of the jaws.

Double centered rotational system

Each panoramic unit has these that are determined by the manufacturer, who provides suggested Ma, and kVp

Exposure factors

The x-ray beam is focused on imaging the structures that are positioned farthest away from the film. T/F

False, structures closest to the film.

Also known as the image layer can be defined as a 3D curved zone in which structures are clearly demonstrated on a panoramic image.

Focal trough

An imaginary plane that passes through the top of the ear canal and the bottom of the eye socket parallel to the floor

Frankfort plane

A radiopaque artifact seen on a panoramic image, is produced when a radiodense object is penetrated twice by the x-ray beam.

Ghost image

How should you tell the pt. to position their lips?

Have the pt. close the lips together around the biteblock, this will avoid recording an image of the lip line across the anterior teeth

How to you correctly position the pt. in lateral position?

Have the pt. line up with the midsagittal line, close the head positioner guides or some panoramic machines have laser light beams to guide the pt.

This consists of a chin rest, notched bite-block, forehead rest, and lateral head supports or guids

Head positioner

Plane of focus within the focal trough

Illustrated here is one moment in the continuous exposure. At this precise moment, the tube head is positioned on the right side, allowing the x-ray beam to penetrate the right side, then continue on to penetrate the left side and carry the images of the structures penetrated to the receptor. At this moment the right side is farther from the image receptor than the left side. At this moment in the exposure sequence, the left side will be recorded on the image, while the right side will be blurred out as a ghost image.

In the Anterior-Posterior Positioning if the arches are *too far forward* or the arches are positioned away from the x-ray tube head and toward the film, is this correct positioning or incorrect?

Incorrect positioning: The anterior teeth are outside the focal trough and will appear blurred and diminished.

In the Anterior-Posterior Positioning if the arches are positioned toward the x-ray tube head and away from the film, is this correct positioning or incorrect?

Incorrect positioning: The arches too far backward, placing the anterior teeth closer to the x-ray tube head and farther away from the film. -the anterior teeth are outside the focal trough and will appear blurred and magnified.

2 basic types of these are used: calcium tungstate and rare earth

Intensifying screen

________ 11The collimator is a lead plate with a small, round or rectangular opening.

Intraoral

________ 12The vertical angulation of the tubehead is variable.

Intraoral imaging

________ 17A lead apron with a thyroid collar must be placed on the patient.

Intraoral imaging

What happens if the pt. is positioned *too far forward* in the focal trough?

It causes the anterior teeth to be *blurred and narrowed or diminished in width.

What kind of error is rotation or incorrect horizontal positioning

Lateral position

What is wrong with this image?

Lips are open and tongue is not held agains roof of the mouth -Apical region of maxillary anteriors are obscured by radiolucent palatoglossal air space.

An imaginary line or plane passing through the center of the body that divides it into right and left halves

Midsagittal plane

In what rotational system the rotational center allows the x-ray beam to continuously focus as the tube head and the image receptor simultaneously move?

Moving-Center rotational systems

Shows a wide view of the maxilla and the mandible

Panoramic

________ 14A screen film is used.

Panoramic

________ 15A cassette holder with two intensifying screens is used.

Panoramic

________ 16The x-ray film must be loaded into a cassette in a darkroom under safelight conditions.

Panoramic

________ 19The midsagittal plane must be positioned perpendicular to the floor.

Panoramic

An extraoral technique that is used to examine the maxilla and the mandible on a single projection

Panoramic imaging

________ 10The collimator is a lead plate with an opening in the shape of a narrow vertical slit.

Panoramic imaging

________ 13A head positioner is used to position the patient's head.

Panoramic imaging

________ 20The vertebral column must be perfectly straight.

Panoramic imaging

________ 6The receptor and the tubehead rotate around the patient.

Panoramic imaging

________ 7This type of image is used to examine the extent of large lesions.

Panoramic imaging

________ 8The dental arches must be aligned to the focal trough.

Panoramic imaging

Receptor used in panoramic examination, shows a wide view of the maxilla and the mandible

Panoramic receptor

Where should you tell the pt. to place their tongue during a pano?

Place the entire dorsal surface of the tongue against the palate, have the pt. swallow, suck in the cheeks.

If the root apices of the mandibular anterior teeth slant out of the focal trough, what is the error?

Pt's chin is too low

If on a pano a pt's posterior teeth appear to be slightly widened on the side that the condyle is tilted up and the mandible appears enlarged on the the same side the condyle is tilted up, what is the error?

Pt's head is tilted: Mandible appears tilted on film and a widened inter-occlusal gap between teeth on the side that is tilted up.

A radiopaque superimposition of the cervical spine in center of the film, usually obscuring the anteriors, occurs because of what positioning error?

Pt. not standing upright

By having the pt. place the entire dorsal surface of he tongue against the plate reduces what?

Reduces the radiolucency caused by the palatoglossal air space. This is the space between the tongue and the roof of the mouth, this radiolucency can obscure the root apices of the maxillary teeth.

Lateral horizontal positioning error is referred to as what?

Rotation

Allows the x-ray beam to continuously focus as the tube head and the image receptor simultaneously move.

Rotation Center

As the beam scans the object , the dental arches, a continuous image is recorded on the moving image receptor referred to as what?

Rotation Center

Which component of the pano x-ray machine is the moving x-ray source that passes through the center of rotation in a horizontal plane towards the path of the moving image receptor.

Rotation Center

The pivotal point, or axis, around which the receptor and the x-ray tubehead rotate is termed this.

Rotation center

This is used in panoramic imaging; this film is sensitive to the light emitted from intensifying screens.

Screen film

The imaginary plane or line from the orbital ridge to the acoustic meatus of the ear is referred to as what?

The Frankfort plane

The wing like projection on the side of the nose and the hole in front of the acoustic meatus refers to what line?

The ala-tragus line

What happens if the midsagittal plane is not positioned perpendicular to the floor?

The anatomy of condyles, sinus, and teeth on the side closer to the image receptor to appear narrowed and the anatomy of the condyles, sinus and teeth on the side farther away from the image receptor will be magnified and widened.

What happens if the pt. is *too far backward* toward the tube head?

The anterior teeth will be *blurred and magnified in width*

A cone shaped radiopacity obscuring the mandible is what error?

The lead apron is too high

If the image has a reversed smile, or a frown, the bottom of the nasal cavity and hard palate are widened into a radiopaque band that obscures the apices of the maxillary teeth, what is the error?

The pt's chin is pointed up

If the root apices of the maxillary anterior teeth slant out of the focal trough, what is the error?

The pt's chin is pointed up

If the image appears to have an exaggerated smile, the mandibular condyles slant inward and the nasopharyngeal air space appears larger and darker, reducing the quality of the image, what is the error?

The pt's chin is too low

If the teeth on the left appear blurred and diminished, and the teeth on the right side appear blurred and magnified, what is the incorrect positioning?

The pt's head is rotated to the left, making the left side closer to the film and the right side closer to the x-ray tube head

If the teeth on the right appear blurred and diminished and the teeth on the left side appear blurred and magnified, what is the incorrect positioning?

The pt's head is rotated to the right making the right side closer to the film and the left side closer to the x-ray tube head

If the pt. is not standing straight or they are slumping over, what happens to the image?

The radiation, which strikes the pt. from behind, is attenuated (weakened) by the compressed vertebra, resulting in a wide radiopacity superimposed over the anterior teeth

Focal trough of the panoramic x-ray unit

This is a 3D curved zone in which structures are reasonably well defined on the panoramic radiographs, and it is important for obtaining high quality images on the structures of interest.

Lateral vertical positioning error is referred to as what?

Tilting

An imaging technique that allows the imaging of one layer, or section, of the body while blurring the images of structures in other planes

Tomography

In what rotational system has 3 centers of rotation create an uninterrupted radiographic image.

Triple center rotating system

As the tube head and film rotate, the x-ray beam is re-focused to image the next section of anatomy. T/F

True

In panoramic imaging, the receptor and the x-ray tubehead move around the pt. in opposite directions. T/F

True

Some panoramic machines have a laser light beam positioned by manufactures recommendation. T/F

True

The closer to the center of the trough (dark zone) an anatomic structure is positioned, the more clearly it is imaged on the resulting radiograph. T/F

True

The image *closest to the image receptor will be the sharpest image*, the image farthest from the image receptor will be a ghost image. T/F

True

There is a spot called a *focal trough* in which the image *will be the sharpest*. T/F

True

This is similar to an intraoral x-ray tubehead; each has a filament used to produce electrons and a target used to produce x-rays

Tubehead

Where is the plane of focus?

Within the focal trough

________ 4 A thyroid collar is not recommended in panoramic imaging because: a. it blocks the x-ray beam and obscures information b. there is a relatively low dose of radiation to the thyroid gland in panoramic imaging c. it is impossible to sterilize the thyroid collar d. all of the above

a. it blocks the x-ray beam and obscures information

________ 2 The zone in which structures are clearly demonstrated on a panoramic image is termed: a. the focal trough b. the rotation center c. the ghost image d. the midsagittal plane

a. the focal trough

Which of these is an advantage of a panoramic radiograph when 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 region is recorded.

Which dimension of the focal trough does the biteblock of the panoramic x-ray machine assist the operator with positioning? a.Anterior-posterior b.Lateral (left-right) c.Superior-inferior

a.Anterior-posterior

What is the term given to a structure that is recorded a second time, with less sharpness, and on the opposite side? a.Ghost image b.Focal trough c.Split image d.Tomograph

a.Ghost image

Which of the following appears radiolucent on a panoramic radiograph? a.Nasal cavity b.Nasal septum c.Nasal spine d. Hard palate

a.Nasal cavity

All panoramic radiographs have 10 to 30 percent magnification. It is desirable to keep the magnification less in the anterior region and greater in the posterior region. a.The first statement is true. The second statement is false. b.The first statement is false. The second statement is true. c.Both statements are true. d.Both statements are false.

a.The first statement is true. The second statement is false.

Which of the following positioning errors results in anterior teeth that are blurry and narrowed in size? a.Too far forward in the focal trough b.Too far backward in the focal trough c.Too far to the left in the focal trough d.Too far to the right in the focal trough

a.Too far forward in the focal trough

________ 5 The imaginary line that passes from the bottom of the eye socket through the top of the ear canal is termed: a. the midsagittal plane b. the Frankfort plane c. the vertebral plane d. the orbital plane

b. the Frankfort plane

Which of the following appears radiopaque on the panoramic radiograph? a.External auditory meatus b.Zygomatic process of the maxilla c.Mental fossa d.Mandibular foramen

b.Zygomatic process of the maxilla

The appearance of a large radiolucency that obscures the maxillary teeth apices results when a.the lips are not closed around the biteblock during exposure. b.the tongue is not resting on the palate during exposure. c.the lead thyroid collar gets in the way of the primary beam. d.facial jewelry (e.g., oral piercing) is not removed prior to exposure.

b.the tongue is not resting on the palate during exposure.

________ 1 Which of the following describes a use of a panoramic image? a. diagnosis of caries b. evaluation of periodontal disease c. evaluation of impacted molars d. evaluation of periapical disease

c. evaluation of impacted molars

________ 3 Rare earth intensifying screens are recommended in panoramic imaging because: a. rare earth screens emit a blue light b. rare earth screens provide a more diagnostic image c. rare earth screens require less x-ray exposure for the patient d. the images convert faster in automatic processors

c. rare earth screens require less x-ray exposure for the patient

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? a.Ghost image b.Artifact c.Focal trough d.Tomography

c.Focal trough

Which of the following could be called a negative shadow? a.Tongue b.Ghost image c.Glossopharyngeal air space d.Biteblock

c.Glossopharyngeal air space

The panoramic PID is collimated to what shape? a.Round b.Rectangular c.Narrow slit

c.Narrow slit

A panoramic radiograph is valuable when diagnosing each of the following EXCEPT one. Which one is theEXCEPTION? a.A cyst b.An impacted molar c.Recurrent caries d.A supernumerary tooth

c.Recurrent caries

Which of these is a limitation of a panoramic radiograph when compared to an intraoral radiograph? a.Larger radiation dose to the patient. b.Increased time required for exposure. c.Superimposition of structures may make interpretation difficult. d.Requires an increase in patient instruction and cooperation with the procedure.

c.Superimposition of structures may make interpretation difficult.

Which of the following planes is used to position the patient correctly within the superior-inferior (up-down)dimension? a.Ala-tragus line b.Frankfort plane c.Midsaggital plane d.Both (a) and (b)

d.Both (a) and (b)

When the dental arches are rotated to the left, the teeth on the right side will be positioned closer to the image receptor.The teeth closer to the image receptor will appear blurry and magnified. a.The first statement is true. The second statement is false. b.The first statement is false. The second statement is true. c.Both statements are true. d.Both statements are false.

d.Both statements are false.

Which of the following positioning errors results in an exaggerated "smile" appearance of the arches? a.Midsaggital plane tipped to the left b.Midsaggital plane tipped to the right c.Chin tipped too far up d.Chin tipped too far down

d.Chin tipped too far down

What is the term given to the technique where a slice of tissue is exposed distinctly, whereas structures out side the designated area are blurred out of the image? a.Ghost image b.Artifact c.Focal trough d.Tomography

d.Tomography

Each of the following is a component of the panoramic x-ray machine EXCEPT one. Which one is theEXCEPTION? 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

Does the line that you use, the frankfort plane or the ala-tragus line, depend on what machine you use?

yes