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radiology > panoramic radiography: principles and technique > Flashcards

panoramic radiography: principles and technique Flashcards

1
Q

What is the definition of panorama?

A

An unbroken view of the whole region surrounding an observer

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2
Q

What is tomography?

A
  • “Slice image”
  • Image of structures lying in a predetermined plane of tissue, blurring detail in images in other planes
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3
Q

What happens when a panoramic image is taken?

A

X-ray source and receptor rotate synchronously around the stationary patient

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3
Q

To capture the curve of the jaw, what must the X-ray tube and receptor do?

A

Have to rotate sequentially about three pivot points, called fixed rotation

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4
Q

What is the pivotal point or axis around which the receptor and x-ray tube rotates?

A

Rotation center

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5
Q

What is the function of the collimator?

A

Restrict x-ray beam to reduce exposure

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5
Q

Does a fixed center of rotation have a high or low radiation dose?

A

High

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5
Q

What does a continuously moving center of rotation mean?

A

X-ray source moves behind the patient, the center of rotation moves along the arc

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6
Q

What X-ray tube head is used in a panoramic unit?

A

IO tube head

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7
Q

Where is the beam collimated in a panoramic machine? 2 answers.

A

X-ray tube
Detector

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8
Q

How do structures appear outside of the focal trough?

A

Blurred, magnified, or reduced in size

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8
Q

What does the shape of the focal trough vary with? 2 answers.

A

Brand of equipment
Image protocol/what type of image you are taking

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9
Q

Does the basic principles of image formation change when using films or digital CCD/PSP?

A

NO

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9
Q

Is the image formed sequentially?

A

Yes

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9
Q

The purpose of laser lights on a panoramic unit is to position the patient’s dentition where?

A

In the focal trough

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10
Q

What is the focal trough?

A

Wide, 3D curved zone where structures in the center of it will be sharp well defined images

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11
Q

What are structures between the receptor and center of rotation called?

A

Real images

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12
Q

What are structures between the center of rotation and the x-ray source called?

A

Ghost images

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13
Q

How can ghost images appear? 3 answers.

A
  • Higher level
  • Contralateral
  • Blurred/significantly magnified
14
Q

How do you decrease magnification? 2 answers.

A
  • Increase source to object distance
  • Decrease in object to image receptor distance
15
Q

How do you increase magnification?

A
  • Decrease source to object distance
  • Increase in object and image receptor distance
16
Q

What are many ghost images from?

A

Normal anatomic structures

17
Q

Can ghost images of normal anatomic structures be a normal finding?

A

yes

18
Q

When are double images created?

A

Occurs when objects lie posterior to the center of rotation and are intercepted twice by the x-ray beam

19
Q

What are 3 anatomic structures that create double images?

A
  • C-spine
  • Hyoid
  • Epiglottis
20
Q

What are four image distortion factors that can occur in pan images?

A
  • X-ray beam angulation
  • X-ray source to object distance
  • Path of rotational center
  • Position of the object within the focal trough
21
Q

What does horizontal magnification depend on?

A

Position of the object within the focal trough

22
Q

What are a few disadvantages of a pan? 4 answers.

A
  • Lower resolution
  • Unequal magnification, no linear measurements
  • Real, ghost, and double images
  • Patient position can lead to errors/artifacts
23
Q

What causes vertical projection angles?

A

Negative angulation, objects closer to the source are at a higher level

24
Q

What are a few advantages of a pan? 4 answers.

A
  • Broad coverage of face/teeth
  • Low radiation dose
  • Good for patients who are intolerant to intraoral radiography
  • Patient education and case presentation
25
Q

How should a patient be positioned for a pan? 3 answers.

A
  • Upright
  • All metal items removed
  • Stay still
26
Q

What are the 5 major positioning criteria?

A
  • Mid-sagittal plane
  • Occlusal plane/Frankfort plane
  • Anterior posterior jaw on bite block
  • Cervical spine
  • Tongue and lips
27
Q

What is the mid-sagittal plane of a pan?

A

Plane should be perpendicular to the floor

28
Q

What is the occlusal or Frankfort plane of a pan?

A

Imaginary line connecting the infraorbital margin and the external auditory meatus, should be parallel to the floor

29
Q

What is the canine lines of a pan?

A

Imaginary line connecting the inner cactus of the eye and canine

30
Q

What is the anterior-posterior plane of a pan?

A

Bite block position, anterior teeth should be in groove to maintain the focal trough

31
Q

What is the cervical spine/neck position of a pan?

A

Proper neck extension, using dental upward force on the mastoid eminences

32
Q

What does slumping cause in a pan image?

A

Ghost image

33
Q

What is the lip and tongue position of a pan?

A

Patient should swallow and hold the tongue against the roof of the mouth

34
Q

What are the 7 diagnostically acceptable pan image requirements?

A
  • Condyles are completely captured and are perpendicular to the inferior aspect of image
  • Hard palate is flat and parallel to floor
  • No asymmetry between left and right rami
  • Even and minimal distortion of teeth
  • No palatoglossal air shadow
  • Spinal shadow not obscuring
  • Aur shadow not obscuring
35
Q

What must all operators wear when using a hand held x-ray device, according to the VA Department of Health?

A

Protective lead apron

36
Q

How should you hold a NOMAD PID?

A

With both hands and have backscatter shield parallel to floor

37
Q

Image quality will ____ as you move the PID and ring away from the patient.

A

Degrade

38
Q

When is the backscatter shield most effective? 3 answers.

A
  • Shield is at outer edge of cone
  • Close to subject
  • Parallel to operator
39
Q

What does the inverse square law state?

A

Intensity of beam is inversely proportional to the square of distance from source

radiology (5 decks)

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