Panoramic imaging principles

Question 1

What are the indications for panoramic radiographs?

(7)

Answer 1

▪ Overall evaluation of dentition
▪ Intraosseous pathology (cysts, tumors, infections,
etc)
▪ Gross evaluation of the temporomandibular joints
▪ Evaluation of position of impacted teeth (3rd molars)
▪ Evaluation of dental development and eruption
▪ Dentomaxillofacial trauma
▪ Developmental disturbances of the maxillofacial
skeleton

want to see mandle, max, teeth; can count how many caries/how many PAs needed

Question 2

Advantages of panoramic over FMS?

(6)

Answer 2

1. Relatively low radiation dose
2. Broad coverage of facial bones and teeth
3. Easier technique
4. Can be used in patients with trismus or in
   patients who cannot tolerate intraoral
   radiographs
5. Quick and convenient radiographic
   technique
6. Useful visual aid in patient education

Question 3

Disadvantages of panoramic over FMS?

(6)

Answer 3

1. Lower-resolution images (not possible
   to detect small carious lesions or early
   periapical disease)
2. Overlap in the premolar area
3. Magnification across image is unequal,
   making linear measurements unreliable
4. Image is superimposition of real,
   double, and ghost images
5. Requires accurate patient positioning to
   avoid positioning errors and artifacts
6. Difficult to image both jaws when
   patient has severe maxillomandibular
   discrepancy

PA has better resolution

Question 4

What pano unit do we use at UMKC clinic?

Answer 4

Question 5

name for each star?

Answer 5

remember name of ones with stars!!!

Question 6

How does panoramic radiograph work?

Describe center of rotation:

Answer 6

x-ray tube head and recptor rotate around it

Question 7

Continuous movement of panoramic

Answer 7

Source starts on the R side –> continues behind head –> ends up on the L side

source never in FRONT of pt

Question 8

When the source is on the ____ side, the left side of the mandible is being imaged.

Answer 8

right

(always opposite due to magnification effects)

Question 9

Is the panoramic sensor (receptor) ever in the back of the patient?

Answer 9

never

Question 10

Is the panoramic xray tubehead (source) ever in front of the patient?

Answer 10

never

Question 11

additional info:

Answer 11

Always imaging same receptor (/column?)

Question 12

What is the focal trough?

Answer 12

a 3D curved zone in which structures are reasonably well defined

you should put mandible and maxilla here (to get well-defined image)

Question 13

Where should dental arches be positioned to achieve sharpest images?

Answer 13

focal trough

Question 14

KNOW:

Objects outside the focal trough are…

Answer 14

blurred, magnified, or reduced in size and are sometimes distorted to the extent of not being recognizable

Question 15

Structures positioned in the center of the focal trough are…

Answer 15

the clearest

(those progressively farther from the
center of the focal trough become progressively less clear)

Question 16

Getting progressively farther from the focal trough structures become….

Answer 16

progressively less clear

ANTERIOR worse than POSTERIOR

Question 17

How can you make sure pt is in focal trough?

Answer 17

bite in grooves of bite block

further anterior = more blurred

Question 18

_____ refers to the
imaginary pivot point (or points)
around which the x-ray source and
the image receptor rotate during
exposure.

Answer 18

Center of Rotation

Question 19

What does a constant pivot point result in?

Answer 19

results in a simple circular focal trough

we cannot follow the shape of the
mandible if circle (we want oval so more centers of rotation)

we want ours OVAL (so we have multiple centers of rotations)

Question 20

How many centers of rotation for panoramic?

Answer 20

not just ONE center of rotation
(multiple and constantly moving centers of rotations)

we cannot follow the shape of the
mandible if circle

only 1 center of rotation,

Not a perfect circle so has MULTIPLE and contantly moving centers of rotation

Question 21

Image Analysis:

Objects closer to the receptor will be ______

Answer 21

narrowed

green: narrow
yellow: magnified but not a lot (stable)
red: further away from receptor looks wider in image

Question 22

Image Analysis:

Objects closer to the source will be _____

Answer 22

widened

green: narrow
yellow: magnified but not a lot (stable)
red: further away from receptor looks wider in image (lingual = wider)

Question 24

Buccal objects will be projected _____

Answer 24

lower

(bc anterior)

Question 25

Lingual objects will be projected _____

Answer 25

higher ## Footnote (bc posterior)

Question 26

What should the beam angulation be for panoramic?

Answer 26

-4 degrees to avoid projection of the occipital bone

Question 27

Structures closer to the **source** are projected _________ on the image, relative to structures that are positioned farther away from the source ## Footnote (more posterior in mouth?

Answer 27

higher ## Footnote due to -4 angulation?

Question 28

# KNOW: Distance between the root apex and the ____________ can be misrepresented on a panoramic radiograph

Answer 28

mandibular canal ## Footnote buccal (further from source; closer to receptor) = lower

Question 29

___________ magnification is determined by the position of the object within the focal trough.

Answer 29

Horizontal

Question 30

Lingual to the focal trough → closer to the source→ Appears ________

Answer 30

wider

Question 31

Buccal to the focal trough→ Appear _______

Answer 31

narrow

Question 32

The _____________ of the horizontal distortion depends on the distance of the object from the center of the focal trough ## Footnote futher back from ring = narrow (????)

Answer 32

magnitude

Question 33

The magnitude of ____________ distortion varies between the anterior and posterior regions of the jaws.

Answer 33

horizontal

Question 34

In the ____________ region, horizontal magnification increases markedly as the object moves away from the center of the focal trough

Answer 34

anterior

Question 35

Where is the degree of the magnification **greater**: posterior or anterior region?

Answer 35

anterior ## Footnote less degree in posterior

Question 36

T/F: Two identical objects located in the anterior and posterior regions may have different horizontal magnifications.

Answer 36

TRUE

Question 37

Horizontal measurements made on panoramic radiographs are...

Answer 37

unreliable

Question 38

3 Images Pano RX create:

Answer 38

1. real 2. ghost 3. double

Question 39

What are real images?

Answer 39

Every anatomical structure positioned between the center of rotation and the **receptor**. ## Footnote change as rotate around pt

Question 40

What are ghost images?

Answer 40

Created by objects located between the x-ray **source** and the center of rotation. ## Footnote (tubehead and COR; on other side?

Question 41

Where do ghost images appear in relation to the real image?

Answer 41

* Appear on the opposite side * at a higher level (than real) * blurred (more than real) * magnified (more than real)

Question 43

Anatomical structures that cast a ghost image include:

Answer 43

- Inferior border of the mandible - angle - ramus - hyoid - cervical spine - jewelry (earrings, hairpins, necklace)(this would not be an anatomical feature tho) - palate

Question 44

What are the characteristics of ghost shadows?

Answer 44

▪ Appears on the opposite side ▪ Positioned higher than real structure ▪ More blurred than the real structure ▪ Vertical component is highly magnified

Question 45

What are double images?

Answer 45

Objects that lie posterior to the center of rotation and that are intercepted twice by the x-ray beam

Question 46

What are examples of structures that can have double images?

Answer 46

- hyoid bone - epiglottis - cervical spine - all of which cast images on both the right and left side of the image.

Question 47

Are double images real or ghost?

Answer 47

real

Question 48

What are the steps for positioning for a pano?

Answer 48

1. Remove jewelry, glasses and dentures 2. Place lead apron 3. Bite in bite block groove 4. Stand patient upright 5. Align the center laser line 6. Align the Frankfurt horizontal plane 7. Close side guides 8. Have the Pt. close their lips, swallow & keep tongue on the palate and hold still 9. Expose the radiograph

Question 49

When do you use the chin rest during a pano?

Answer 49

The chin rest if used if the patient has no or only a few anterior teeth.