Chapter 25; Panoramic Imaging

Describe the purpose and uses of panoramic imaging

- overall view of maxilla/mandible - supplemental to bitewings and PA images - evaluate impacted teeth - evaluate eruption patterns, growth, development - detect disease, lesions, conditions of the jaw - examine the extent of large lesions - evaluate trauma - panoramic images are not as defined/sharp as intraoral projections - panoramic images should NOT be used to diagnose caries or periodontal disease

Describe the fundamentals of panoramic imaging

- receptor and x-ray tubehead move around the patient - x-ray tubehead moves one way, receptor moves the opposite way - patient stands in a stationary position - tomography: imaging of one layer of the body while blurring the images of structures in other planes - image conforms to the shape of the dental arches

A real image results when...

a structure lies between the receptor and moving rotation center, this is a "true" image and appears in the correct anatomic location with varying degrees of sharpness and distortion structures found within the focal trough appear sharp on the resultant image while structures outside of the focal trough appear blurred

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

a. focal trough In panoramic imaging, the focal trough is a theoretical concept used to determine where the dental arches must be positioned to obtain the sharpest image

A ghost image results when...

an anatomic structure or object is located outside of the focal plane and close to the x-ray source, this resembles the true image and is found on the opposite side of the receptor, it appears blurred, magnified, and higher than the actual counterpart due to negative vertical angulation of the x-ray beam examples that cause ghost images; ramus of the mandible, hard palate, and earrings

A double image results when...

anatomic structures that are located behind the moving rotation center is penetrated twice by the x-ray beam, a double image has the same proportions as the real image and is located in the same location on the opposite of the recetpr this appears as a mirror image, or the reverse of the real image examples; epiglottis, hyoid bone, cervical spine

Which imaginary plane passes from the bottom of the eye socket through the top of the ear canal? a. midsagittal b. Frankfort c. frontal d. axial

b. Frankfort

A cassette holder with two intensifying screens is used panoramic imaging, intraoral imaging, or both?

both

A screen film is used panoramic imaging, intraoral imaging, or both?

both

The midsagittal plane must be positioned perpendicular to the floor panoramic imaging, intraoral imaging, or both?

both

The tubehead contains a filament used to produce electrons and a target used to produce x-rays panoramic imaging, intraoral imaging, or both?

both

The x-ray film must be loaded into a cassette in a darkroom under safelight conditions panoramic imaging, intraoral imaging, or both?

both

Which describes a use of a panoramic image? a. evaluation of caries b. evaluation of periodontal disease c. evaluation of impacted molars d. evaluation of periapical disease

c. evaluation of impacted molars Panoramic imaging is not diagnostic for periodontal disease, caries, or periapical disease/lesions

Rare earth intensifying screens are recommended in film-based 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

Give examples of Frankfort plane positioning errors, and discuss what steps can be taken to correct such errors

chin tipped up: the Frankfort plane is angled upward which results in...the condyles are not visible or appear near the lateral edge of the image, the hard palate and floor of the nasal cavity appear superimposed over the maxillary roots, the maxillary incisors and blurred and magnified, loss of detail in the maxillary incisor region, and a "reverse smile line" is seen on the image solution: position the patient so the Frankfort plane is parallel to the floor chin tipped down: the Frankfort plane is angled downward which results in...the condyles are positioned higher on the image, the hyoid bone forms and single widened line, the mandibular incisors appear blurred (roots may appear short), loss of detail in the anterior apical region, an exaggerated smile line or "jack-o-lantern" appearance is seen on the image solution: position the patient so the Frankfort plane is parallel to the floor

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

d. all of the above

Discuss the patient preparations necessary before exposure of a panoramic projection

explain the imaging process: explain the procedure to the patient place lead apron: place a lead apron around the patient without a thyroid collar, place the apron low enough so it does not block the x-ray beam, use a double-sided lead apron (front and back side) remove all objects: request that the patient remove all objects within the head and neck region that may obscure with the imaging process, items include eyeglasses, earrings, intraoral/extraoral piercings, necklaces, hearing aids, hairpins, and any intraoral protheses (partials, dentures, etc.)

Discuss the advantages of panoramic imaging

field size: covers entire maxilla/mandible, more structures can be viewed on a panoramic image than an FMX, lesions and jaw conditions can be seen simplicity: exposure is relatively simple, minimal amounts of time and training are required patient cooperation: no discomfort is involved, easier for children to sit still during exposure of a panoramic image minimal exposure: a panoramic image only requires minimal amounts of radiation exposure for the patient

Discuss the disadvantages of panoramic imaging

image quality: not as sharp as intraoral projection, cannot be used to diagnose caries, periodontal disease, or periapical lesions focal trough limitations: objects of interest outside of the focal trough cannot be seen distortion: even with proper technique, certain amounts of magnification, distortion, and overlapping are present on a panoramic image equipment cost: cost of a panoramic x-ray unit is high compared to the cost of an intraoral x-ray unit

A lead apron with a thyroid collar must be placed on the patient panoramic imaging, intraoral imaging, or both?

intraoral imaging

The collimator is a lead plate with a small, round, or rectangular opening panoramic imaging, intraoral imaging, or both?

intraoral imaging

The vertical angulation of the tubehead is variable panoramic imaging, intraoral imaging, or both?

intraoral imaging

A head positioner is used to position the patient's head panoramic imaging, intraoral imaging, or both?

panoramic imaging

Earrings and necklaces must be removed before exposure panoramic imaging, intraoral imaging, or both?

panoramic imaging

The collimator is a lead plate with an opening in the shape of a narrow vertical slit panoramic imaging, intraoral imaging, or both?

panoramic imaging

The dental arches must be aligned to the focal trough panoramic imaging, intraoral imaging, or both?

panoramic imaging

The receptor and the tubehead rotate around the patient panoramic imaging, intraoral imaging, or both?

panoramic imaging

This type of image is used to examine the extent of large lesions panoramic imaging, intraoral imaging, or both?

panoramic imaging

The vertebral column must be perfectly straight panoramic imaging, intraoral imaging, or both?

panoramic imaging ideally both

Describe the equipment used in panoramic imaging

panoramic x-ray unit x-ray tubehead head positioner exposure controls collimator; a lead plate with an opening in the shape of a vertical slit, this reduces patient exposure tubehead; in a fixed position, beam directed slightly upward (-10 degrees), rotates behind the patient head positioner: chin rest, notched bite-block, forehead rest, and lateral head supports/guides exposure time: ranges from 10-30 seconds

Discuss the patient positioning steps necessary before exposure of a panoramic projection

position spine: patient will sit or stand "as tall as possible" with the shoulders back, the spine must be perfectly straight position teeth: patient bites in the grooves on the bite-block to align the teeth in the focal trough, position maxillary and mandibular anterior in an end-to-end position in the bite-block groove position head: position the midsagittal plane perpendicular to the floor, position the frankfort plane parallel to the floor, patient's head cannot be tipped up or down position lips and tongue: tongue on the roof of the mouth, "swallow and feel the tongue rise up to the roof of the mouth" to accomplish this, patient closes lips around the bite-block final instructions and exposure: instruct patient to remain still while the machine is rotating during exposure, expose the receptor

Discuss the equipment preparations necessary before exposure of a panoramic projection

prepare receptor: if using film only, load panoramic cassette in darkroom under safelight conditions, place an extraoral film and two intensifying screens in the cassette and close securely, load cassette into the cassette carrier of the panoramic unit prepare bite-block: cover the bite-block with a disposable plastic cover slip, bite-block must be sterilized in between uses if a plastic cover is not used choose exposure settings: set exposure factors (kv, mA, time) according to manufacturer recommendations, use the size of the patient to determine exposure settings adjust machine height: adjust the machine to accommodate the height of the patient, and align all moveable parts