Panoramic Imaging Principles Flashcards
what are the indications for panoramics
- 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
what are advantages of panoramic over FMS
- 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
what are disadvantages of panoramic over FMS
- 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
how does pano work
- direction of receptor past collimator
- direction of xray source around patient
- direction of receptor and collimator around patient
what is the continuous movement of pano source
- starts on the R side
- continues behind head
- ends up on the L side
when the source is on the right side, the ____ side of the mandible is being imaged
left
the sensor is never______
in the back of the patient
the x ray tubehead is never ______
in front of the patient
what is the focal trough
a three dimensional curved zone in which structures are reasonably well defined
- where dental arches must be positioned to achieve sharpest images
describe objects outside the focal trough
blurred, magnified or reduced in size and are sometimes distorted to the extend of not being recognizable
what structures are the clearest in the focal trough
structures positioned in the center of the focal trough
what is the issue with the center of rotation and what is the solution
- not just one
- we cannot follow the shape of the mandible
- solution: multiple and constantly moving centers of rotation
what is the pano unit that we use downstairs
orthophos XG sirona
objects closer to the receptor will be:
narrowed
objects closer to the source will be:
widened
buccal objects will be projected:
lower
lingual objects are projected:
higher
what is the beam angulation and why
about -4 degrees to avoid projection of the occipital bone
structures closer to the source are projected:
higher up on the image
distance between the _____ and the _____can be misrepresented on a pano
root apex and mandibular canal
horizontal magnification is determined by:
the position of the object within the focal trough
lingual to the focal trough ->
closer to the source -> appears wider
buccal to the focal trough ->
appears narrow
the magnitude of the horizontal distortion depends on the:
distance of the object from the center of the focal trough
describe horizontal magnification in the anterior region
increases as the object moves away from the center of the focal trough
is the degree of magnification higher in the posterior or anterior
anterior
horizontal measurements made on pano images are:
unreliable
what are real images
every anatomical structure positioned between the center of rotation and the receptor
what are ghost images created by
objects located between the x ray source and the center of rotation
where do ghost images appear
on the opposite side at a higher level, blurred and magnifiedw
what are the anatomical structures that cast a ghost image
- inferior border of the mandible
- angle
- ramus
- hyoid
- cervical spine
- jewelry
- palate
what are the characterisitcs of the ghost shadows
- appears on the appposite side
- positioned higher than real structure
- more blurred than the real structure
- vertical components is highly magnified
what are double images
objects that lie posterior to the center of rotation and that are intercepted twice by the x ray beam
what are the anatomical structures that are double images
- hyoid bone
- epiglottis
- cervical spine
- cast images on the right and left side of the image
all double images are _____
real images
what is the positioning of the patient in panos
- 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
