Chapter 8: Panoramic Imaging Flashcards
Panoramic imaging is like a bridge between?
Intraoral projection and tomography
What is the gold standards for dentists
panoramic
Some limitations of panoramic imaging include
- magnification
- double image
Pantomography:
- technique for producing a single image of the facial structures that includes both the maxillary and mandibular dental arches and their supporting structures
An xray source and a image receptor rotate around the patient’s head and create a curved?
Focal trough
The focal trough is a zone in which?
The included objects are displayed clearly
Focal trough: vertical/horizontal collimated xray beam?
Vertical
The focal trough is the area in which structures will appear most sharply and clearly. Which structures can be distorted, magnified , or reduced?
The ones that fall in front of or behind the focal trough
Regarding the shape and size of the focal trough?
Varies between manufactures
Indications of panoramic imaging:
- overall evaluation of dentition
- examine for intraosseous pathology: cyst, tumours, infections
- evaluation for TMJ
- evaluation for position of impacted teeth
- evaluation of eruption of permanent dentition
- dentomaxillofacial trauma
- developmental disturbances of maxillofacial skeleton
- dental specialties: restorative dentistry, oral and maxillofacial surgery, periodontics, orthodontics, implantology, forensic and legal dentistry
Advantages of panoramic imaging:
- broad coverage of facial bones and teeth
- low radiation dose, ET
- ease of panoramic radiographic technique
- used in patients who cant tolerate Intraoral radiography
- quick and convenient Radiographic technique
- make comparisons between left and right sides
- useful visual aid in patient education
- affordable for the patient. Not expensive
Disadvantages of panoramic imaging:
- lower resolution images
- don’t provide the fine details (caries, periapical disease)
- magnification across image is unequal, 25% , geometric distortion
- superimposition, double and ghost images
- requires accurate patient positioning
- costly machines
The X-ray tube produces fine beam ____ collimated?
Vertically
The moving source and receptor generate a zone of sharpness called
Focal trough
Only a ___ is exposed and sweeps the area of interested synchronised with the movement of the receptor
Vertical fine line
Focal trough image layer:
3D curved zone where the structures lying within this zone are reasonably well defined on the final panoramic image
The 3 principles of panoramic imaging are?
- Focal trough
- Image distortion
- Imaging
Objects outside the focal trough are?
Blurred, magnified, reduced in size and unrecognisable
Shape and width of focal trough are determined by?
- the path and velocity of the receptor and X-ray tube head
- alignment of the xray beam
- collimator width
Image distortion is unreliable for
Linear or angular measurements
Factors of image distortion:
- xray beam angulation
- xray source to object distance
- path of rotational center (patient’s head has to be in the middle)
- position of the object within the focal trough
- patient anatomy
- positioning of the patient in the unit
Depending on their location, objects may cast three different types of images?
- Real images
- Ghost images
- Double images
Real images:
- where do the objects lie?
Between center of rotation and receptor
CR O R
Objects within the focal trough?
Sharp
Objects away from the focal trough?
Blurred
Double images?
- where do the objects lie?
- examples
- posterior to the moving center of rotation and are intercepted twice by the xray beam
- hyoid bone, epiglottis, cervical spine
O CR R
Ghost images?
- where do the objects lie?
- examples
- between the xray beam source and center of rotation, appear on opposite side of its true anatomic location
- mandibular ramus, hyoid bone, cervical spine, metallic accessories
XRAY BEAM O CR
Panoramic machines:
- several brands highly versatile
- make frontal and lateral images of TMJs
- capable of producing tomographic views
- cephalometric attachment
- available in CCD digital configurations
Patient positioning:
- remove dental appliances, earrings, necklaces, hairpins, metallic objects (to avoid bright ghost images)
- anteroposterior position: bite block to stabilise head
- laser beam to facilitate the alignment
- patient’s back and spine as erected as possible
- patient’s neck extended
Regarding patient postioning:
- the mid sagital plane has to be ?
- frankfurt plane and anteroposterior position within?
- occlusal plane:
- canthomeatal line parallel with?
- centred within the focal trough
- the focal trough
- lower anteriorly, angled 20-30 degrees below the horizontal
- the floor
If the patient is positioned too far posterior?
- ____ mesiodistal dimensions through the ____ sextant
- teeth appear?
- magnified, anterior
- fat teeth
FP
If the patient is positioned too far anterior?
- ____ mesiodistal dimensions through the ____ sextant
- teeth appear?
- reduced, anterior
- thin
AT
If there’s a poor _______, ___ distortion in the ____ region
Midline positioning, horizontal, posterior
Premolar regions: excessive overlap, and nondiagnostic , unacceptable images
If there’s a failure in the ____, ____ are unequally ____ in the ____ dimension
mid sagittal plane positioning , right and left sides , magnified, horizontal
Digital receptors are being used increasingly to:
View screen
Modify image characteristics: contrast, density
Image receptors:
- export digital image
- digital storage
- intensifying screens: reduce distortion
- mechanism for automatically marking the patient’s left or right sides on the image
- patient’s name, age, date
- dentists name
Interpreting panoramic images:
- compared to intraoral
- regarding recognising anatomical structures
- problems And what can cause them
- more complex than intraoral images when interpreting
- difficult to recognise normal anatomic structures
- mid face complex anatomy , superimposition, and real, double, and ghost images
- machine, patient movement, patient positioning, unusual anatomy
What are two dimensional representations of three dimensional structures ?
Conventional xray projections
What are curved image slices, and has less superimposition of structures?
Panoramic views
Panoramic image represents the ___ jaw that is ____ onto the flat plane
Curved, unfolded
Posterior regions represents which view?
Lateral, sagital
Anterior sextant represents which view?
Coronal (AP) view
4 things interpreted in a panoramic xray?
Teeth
Midfacial region
Mandible
Soft tissues
Teeth in a panoramic xray:
- demonstrates the complete dentition
- identification of all erupted and developing teeth (number, position, anatomy)
- restorations
- gross caries and periapcial disease may be evident
- impacted third molars
excessively wide or narrow anterior teeth means?
malposition of patient in focal trough
Teeth wider on one side or the other means?
patient’s sagittal plane is rotated
proximal surfaces of which teeth often overlap ?
Premolars
Mid-facial region contains a complex mixture of bones, air cavities, and soft tissues which include:
- temporal
- zygoma
- mandible
- frontal
- maxilla
- sphenoid
- ethmoid
- vomer
- nasal
- nasal conchae
- palate
Major sites for examination in the midfacial region?
7
1.maxillary cortical boundary
2. Pterygomaxillary fissure
3. Maxillary sinuses
4. Zygomatic complex
5. Nasal cavity
6. TMJ
7. Maxillary dentition/alveolus
Maxillary cortical boundary:
From the superior portion of the pterygomaxillary fissure down to the tuberosity
Pterygomaxillary fissure:
Inverted teardrop appearance, mucoceles and carcinomas destroy the posterior maxillary border
Maxillary sinuses:
Well visualised, borders (posterior, anterior, floor, roof)
Symmetry, borders present and intact
Zygomatic complex:
Frontal, zygomatic, and maxillary bones
Nasal cavity:
Nasal septum and inferior concha
Areas in the mandible:
- pharyngeal airway
- posterior wall of the naso pharynx
- cervical vertebra
- earlobe and ear decorations
- nasal cartilage and decorations
- soft palate and uvula
- dorsum of the tongue
Major areas of interest in the mandible:
- condylar process and TMJ: mandibular condyle, slightly anterior (patient protrusion), condyle shape, glenoid fossa
- coronoid process
- ramus/angle: fracture lines, symmetry
- body and angles/ramus: mandibular canals, mental foramina, anterior loop of mandibular canal, mental protuberance (radio opaque)
- anterior sextant
- mandibular dentition/alveolus
Soft tissues:
Tongue arching, lip markings, soft palate, nasal septum, earlobes, nose, Nasolacrimal folds, epiglottis, thyroid cartilage
Soft tissues:
Tongue arching, lip markings, soft palate, nasal septum, earlobes, nose, Nasolacrimal folds, epiglottis, thyroid cartilage
