Panoramic radiography Flashcards
what is the most common extra-oral radiograph in dentistry?
panoramic radiography
what is tomography?
allows slices of the subject to be viewed separately
what are the 2 types of tomography?
Conventional
Computed
what is the difference between conventional and computed tomography?
conventional is one slice
computed is multiples slices
what is panoramic radiography?
Form of conventional tomography where it captures and displays the curved shape of the jaws as a 2D image
panoramic radiography technique
Patient stands in ? of machine
X-ray source ? patient
Receptor ? patient
Both rotate at the same time ?* (they remain ? each other)
Whole thing takes ? so ? affects image greatly
middle
behind
in front of
180*
opposite
14 seconds
movement
modified version of linear tomography
X-ray source and receptor move in ? directions
Structures in the focal slice remain projected on the same point on the receptor and appear ?
Structures outside the focal slice are continually projected on different parts of the receptor and appear ?
the focal trough in panoramic radiographs are ?
opposite
clear
blurry
the jaws
panoramic radiography captures the full thickness of the jaw but the focal trough is a thin band where the image is clearest
as you go bucally or lingually to the focal trough the image quality ?
decreases
where is the focal trough thinner? why? impact?
the incisor region due to speed of rotation -> common for incisors to be blurry
what is a limitation of panoramic radiography (focal trough)?
ectopic teeth may be far out of the focal trough so appear missing
what is the default choice for panoramic radiography?
orthogonal programme
what does orthogonal programme aim to do? how?
provide an optimal view of the dentition
○ X-ray angulation changed to more orthogonal (90* to teeth)
advantages of orthogonal programme panoramic radiographs? 3
Reduced overlap -> proximal caries
Improved view of pre molars
Interdental periodontal bone levels represented more accurately
disadvantages of orthogonal programme panoramic radiographs? 2
Distorts other structures
Narrower field of view -> may miss condyles
describe the magnification within the focal trough?
image is magnified 25%
describe the magnification of structures lingual to the focal trough
magnified more
describe the magnification of structures buccal to the focal trough
magnified less
describe the distortion of structures within the focal trough
not distorted as horizontal magnification matches vertical
describe the distortion of teeth positioned lingual to the focal trough
appear wider
as closer to x-ray source
describe the distortion of teeth positioned buccal to the focal trough
appear narrower
further from x-ray source and closer to receptor
what is field limitation?
instead of doing a full size panoramic radiograph, when appropriate reduce the area to reduce the dose
what are the 4 main components of a panoramic machine?
X-ray tube head
Receptor
Control panel
Patient-positioning apparatus
what are the 2 patient-positioning aparatus?
bite peg
light beam markers
what does the bite peg do (patient positioning)
ensures edge-to-edge occlusion and both arches are in the focal trough plane
when is it impossible to get edge to edge occlusion on the bite peg?
class III occlusion
Patient too far forwards -> incisors appear ?
narrower as buccal to focal trough
Patient too far backwards -> incisors appear ?
wider as lingual to focal trough
here the incisors appear narrow, why is this?
patient too far forwards
here the incisors appear wider, why is this?
patient too far back
light beam markers
the horizontal line matches what?
Frankfort plane (infraorbital margin -> EAM)
beam markers
if the chin is down (frankfort plane above horizontal line) what happens to the occlusal plane?
smiling occlusal plane
beam markers
if the chin is up (frankfort plane below horizontal line) what happens to the occlusal plane?
flat occlusal plane
look at this example where the Frankfort plane is horizontal
what has caused this wrong occlusal plane?
smiling occlusal plane
chin down
Frankfort plane below horizontal line
what has caused this wrong occlusal plane?
flat occlusal plane
chin up
Frankfrot plane above horizontal line
beam markers for patient positioning
Vertical midline matches?
mid-sagittal plane
beam markers for patient positioning
if the mid sagittal plane is not centred what happens?
distortion of one/both sides
beam markers for patient positioning
if the mid-sagital plane is not vertical what happens?
distortion and occlusal plane cant
beam markers for patient positioning
canine lines match what?
maxillary canines
what causes this excessive cervical spine shadow?
patient slumped
preparation for panoramic radiographs 3
Remove metal foreign bodies from head and neck e.g. piercings
Keep patient as upright as possible
- Patient slumped -> excessive cervical spine shadow
Advise patient
- Tongue to roof of mouth
- Stand still
- Don’t talk or swallow
what causes part of the image to be cut out?
sharp horizontal movement
what causes a smeared image?
slow horizontal movement
what causes Zigzag of mandible and teeth?
vertical movement of mandible
what causes this?
patient movement
what caused this air gap?
tongue not to palate
what has caused the left soft palate to be wiggly?
tongue movement
what has caused this zigzag pattern?
vertical mandible movement
what has caused this smear?
patient moving
what has caused part of the image to be cut out?
Brief sharp horizontal movement
are lead aprons required in dental radiography?
no
what is a quality standards checklist?
list of things to check on panoramic radiographic image
look at this quality standards checklist
