January 20- Extra Oral Techniques Flashcards

1
Q

What are some ways Panorramic Images are used in a Clinical Setting

A

• Fractures, wisdom tooth assessment, lesions, eruption and development, retained teeth/root tips, TMJ, developmental anomalies

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2
Q

What are the different types of Panoramic image receptors?

A
  • Film and rare-earth intensifying screens cassettes
  • PSP plate cassettes
  • Solid state sensor cassettes designed to fit into

existing equipment

• Specially designed solid state sensors

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3
Q

How does a Panoramic X-ray machine work (Very Simply)

A

The X-ray Tube and receptor rotate around the persons head at the same rate in a counterclockwise motion. As the X-ray passes through the structures they are projected onto the the screen/receptor producing a panoramic image.

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4
Q

What is the Focal Trough?

A
  • This is a 3D curved zone where the structures lying within the zone are well defined on the final pan image.
  • Roughly a parabolic shape designed to conform to the shape of the dental arches in the majority of the population
  • Laser lights aid the operator in aligning the patients dentition optimally in the focal trough
  • Objects outside the focal trough are blurred, magnified and distorted
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5
Q

Where should the dental arches be located in regards to the focal trough?

A

• The key to taking a good pan, is

to get the patients dental

arches as close to the middle

part of the focal trough

(darkest part) as possible.

• If structures are not in the

middle of the layer they appear

distorted.

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6
Q

What happens when structures are outside the focal trough?

A

The edge of the layer (focal trough) is like a “cliff” where structures “fall off-out” and disappear from the image.

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7
Q

How do you correctly position a patient to ensure their dental arch lies within the Focal Trough?

A

Orient the patient so that their mandibular incisors are within the notch in the Pan machines “alignment stick”

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8
Q

What happens when a patients dental archs are aligned
A. at inner part of the focal trough

B. at the outer part of the focal trough

A
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9
Q

What is the common Vertical Angulation of the X-ray in Pan X-ray machines. And what effect does this angulation have on the images produced.

A

the common vertical angulation is 8 degrees to the horizonal, This angulation causes structures IN FRONT of the rotational center to appear HIGHER and structures BEHIND to appear Lower

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10
Q

What effect does Verticle Angulation have on resultant Pan radiographs?

A

Verticle angulation can cause misrepresentation of the distances between structures
ie: the distance between the apex of the root and the mandubular canal

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11
Q

In a Pan radiograph what is a Single Real Image? And when are they formed?

A
  • single real images result when a structure is located in front of the centre of rotation (i.e. between the image receptor and the rotation centre) and is intercepted only once by the x-ray beam
  • The majority of the images seen on a panoramic image

are this type e.g. maxillary sinus, floor of orbit, soft tissue

of nose etc

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12
Q

In Panoramic radiographs what is a Double Real Image? And when are they formed?

A

Double Real Images are produced if a structure is located in front of the centre of rotation and is intercepted twice by the x-ray beam.

  • These images are produced by structures in the posterior midline such as the hard and soft palate, hyoid bone, epiglottis and the cervical spine that fall into a diamond shaped zone produced by the the movement pattern of the x-ray beam.
  • One image is the exact mirror image of the other
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13
Q

in Panoramic Radiographs what is a Ghost Image and how are they formed?

A
  • Ghost images are formed when the anatomical structure is located behind the rotation centre of the x-ray beam. i.e. they are between the x-ray source and the rotation centre.
  • Ghost images are not mirror images, appear on the opposite side, are more blurred, larger and superior than the real counterpart.
  • These usually result from external objects such as earrings and necklaces, but can also occur with dense anatomical structures that are in the midline such as the angle of the mandible, the hard palate and the cervical vertebrae.
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14
Q

What is this an example of?

A

This is an example of an artifact (earrings) GHOST IMAGE.
Note how the earrings are distorted and where they are projected.

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15
Q

what has caused this misrepresentation in the panoramic image?

A

Verticle Angulation of the X-ray beam

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16
Q

Who made the best deck of flashcards?

A. Ben “the Hulk” Hughes

B. Logan “The horror” Orr

C. Justin “the Master” McMurray

D. Trent “the Terrific” Orth

E. Dallin “Okay” Kay

A

E. Yup, thats right….ME, now get back to work!

17
Q

What are 8 steps of how to take a pano image?

A
  1. Adjust machine settings to patient build and height
  2. Lead apron (and thyroid collar at some clinics)
  3. Ear-rings and dentures/appliances out
  4. Patient stands upright, holding handles, biting into groove in biteblock with chin on chin rest
  5. Immobilize head with temple supports
  6. Use the light beam markers to check mid-sagittal plane is vertical and the Frankfort plane is horizontal.
  7. Have pt put tongue on roof of mouth, close lips, be very still.
  8. Expose and watch patient
18
Q

IF the patient moves durng the exposure, what should you do?

A

Stop the exposure

19
Q

Getting the patients teeth in the _____ _____ is crucial to accurate patient positioning for a clear image.

A

Focal trough

20
Q

This patient positioning error in a pano image makes the anterior teeth appear narrow.

A

Patient too for forward. In front of focal trough.

21
Q

This patient positioning error in a pano image makes the anterior teeth appear widened, magnified, and out of focus.

A

Patient too far back. Behind focal trough.

22
Q

This patient positioning error makes the right jaw minimized and the left jaw magnified.

A

Head rotated to the right.

23
Q

This patient positioning error causes a prominent ghost image of the spine.

A

Patient slumped and/or patient unable to straighten neck due to arthritis.

24
Q

In this patieint positioning error the frankfort plane is not horizontal, the mandibular symphsis is missing, the lower anterior teeth are distorted, excessive ghosting of contralateral mandibles and cervical spine occurs, the lower incisors out of focus, and the occlusal plane makes a “smiley face”

A

Chin tipped too low

25
Q

In this patient positioning error, the hard palate is superimposed over roots of the maxillary teeth and overlapping contacts of many teeth are seen. The occlusal plane makes a “grumpy face”

A

Chin tipped too high

26
Q

Lateral cephalograms can be used to assess what 4 things?

A
  1. Orthodontic/orthognathic surgery planning;
  2. Soft tissue profile of the face (filter – tissue)
  3. Bone of the face and skull
  4. Trauma and disease
27
Q

Cephalometric imaging aids othrodontics in these three ways?

A
  1. Orthodontic records
  2. Craniofacial growth
  3. Orthodontic follow ups
28
Q

Posterioanterior projections (PA projections) are used for what three things?

A
  1. Evaluate facial growth
  2. Trauma and disease
  3. Developmental abnormalities … orbits, sinuses and nasal cavity
29
Q

The submentovertex projection technique is used to identify these four things?

A

Identify position of the:

  1. Condyles
  2. Base of the skull
  3. Zygomatic arch fracture
  4. Lateral wall of the sinus
30
Q

The ______ _____ projection helps to identify the

  1. Maxillary sinus area
  2. Frontal and ethmoid sinuses
  3. The orbits contour
  4. The nasal cavity
A

Waters view

31
Q

The Reverse Towne projection is used to detect what?

A

Fractures in the Condylar neck and Ramus area

32
Q

What are the names of the following projections shown in the attached table, from left to right (far left #1, farthest right #5)

A
  1. Lateral Cephalometric
  2. Submentovertex (SMV)
  3. Waters view
  4. Posterioanterior (PA)
  5. Reverse Towne