Panoramic Imaging Principles

Question 1

what are the indications for panoramics

Answer 1

• overall evaluation of dentition
• intraosseous pathology
• gross evaluations of the TMJ
• evaluation of position of impacted teeth - 3rd moalrs
• evaluation of dental development and eruption
• dentomaxillofacial trauma
• developmental disturbances of the maxillofacial skeleton

Question 2

what are advantages of panoramic over FMS

Answer 2

• relatively low radiation dose
• broad coverage of facial bones and teeth
• easier technique
• can be used in patients with trismus or in patients who cannot tolerate intraoral radiographs
• quick and convenient radiographic technique
• useful visual aid in patient education

Question 3

what are disadvantages of panoramic over FMS

Answer 3

• lower resolution images (no possible to detect small carious lesions or early periapical disese)
• overlap in the premolar area
• magnification across image is unequal, making linear measurements unreliable
• image is superimposition of real, double and ghost images
• requires accurate patient positioning to avoid positioning errors and artifacts
• difficult to image both jaws when patient has severe maxillomandibular discrepancy

Question 4

how does pano work

Answer 4

• direction of receptor past collimator
• direction of xray source around patient
• direction of receptor and collimator around patient

Question 5

what is the continuous movement of pano source

Answer 5

• starts on the R side
• continues behind head
• ends up on the L side

Question 6

when the source is on the right side, the ____ side of the mandible is being imaged

Answer 6

left

Question 7

the sensor is never______

Answer 7

in the back of the patient

Question 8

the x ray tubehead is never ______

Answer 8

in front of the patient

Question 9

what is the focal trough

Answer 9

a three dimensional curved zone in which structures are reasonably well defined
- where dental arches must be positioned to achieve sharpest images

Question 10

describe objects outside the focal trough

Answer 10

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

Question 11

what structures are the clearest in the focal trough

Answer 11

structures positioned in the center of the focal trough

Question 12

what is the issue with the center of rotation and what is the solution

Answer 12

• not just one
• we cannot follow the shape of the mandible
• solution: multiple and constantly moving centers of rotation

Question 13

what is the pano unit that we use downstairs

Answer 13

orthophos XG sirona

Question 14

objects closer to the receptor will be:

Answer 14

narrowed

Question 15

objects closer to the source will be:

Answer 15

widened

Question 16

buccal objects will be projected:

Answer 16

lower

Question 17

lingual objects are projected:

Answer 17

higher

Question 18

what is the beam angulation and why

Answer 18

about -4 degrees to avoid projection of the occipital bone

Question 19

structures closer to the source are projected:

Answer 19

higher up on the image

Question 20

distance between the _____ and the _____can be misrepresented on a pano

Answer 20

root apex and mandibular canal

Question 21

horizontal magnification is determined by:

Answer 21

the position of the object within the focal trough

Question 22

lingual to the focal trough ->

Answer 22

closer to the source -> appears wider

Question 23

buccal to the focal trough ->

Answer 23

appears narrow

Question 24

the magnitude of the horizontal distortion depends on the:

Answer 24

distance of the object from the center of the focal trough

Question 25

describe horizontal magnification in the anterior region

Answer 25

increases as the object moves away from the center of the focal trough

Question 26

is the degree of magnification higher in the posterior or anterior

Answer 26

anterior

Question 26

horizontal measurements made on pano images are:

Answer 26

unreliable

Question 27

what are real images

Answer 27

every anatomical structure positioned between the center of rotation and the receptor

Question 28

what are ghost images created by

Answer 28

objects located between the x ray source and the center of rotation

Question 29

where do ghost images appear

Answer 29

on the opposite side at a higher level, blurred and magnifiedw

Question 30

what are the anatomical structures that cast a ghost image

Answer 30

- inferior border of the mandible - angle - ramus - hyoid - cervical spine - jewelry - palate

Question 31

what are the characterisitcs of the ghost shadows

Answer 31

- appears on the appposite side - positioned higher than real structure - more blurred than the real structure - vertical components is highly magnified

Question 32

what are double images

Answer 32

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

Question 33

what are the anatomical structures that are double images

Answer 33

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

Question 34

all double images are _____

Answer 34

real images

Question 35

what is the positioning of the patient in panos

Answer 35

- remove jewlery, glasses, and dentures - place lead apron - bite in biteblock groove - stand patient upright - align the center laser line - align the frankfurt horizontal plane - close side guides - have the pt close their lips, swallow and keep tongue on the palate and hold still - expose the radiograph