PANORAMIC IMAGING

Question 1

Tomography -

Answer 1

imaging by sectioning, through a body, by moving an x-ray

source and the film in opposite directions during the exposure.

Question 2

Panorama

Answer 2

An unobstructed and wide view of an

extensive area in all directions

Question 3

2 methods used to obtain a panoramic radiograpph

Answer 3

status x and opg

Question 4

principle of panoramic imaging

Answer 4

It is a curvilinear variant of conventional tomography and
is based on the principal of the reciprocal movement of an x-ray
source and an image receptor around a central point or plane
called the image layer in which the object of interest is located

Question 5

Mostly used diagnostic problems including broad coverage

Answer 5

trauma including jaw fractures, location of 3rd molars, extensive dental or osseous disease, known or susoected large lesions, tooth development or and eruption, retained teeth or root tips, tmj pain, developmental anomalies.

Question 6

center of rotation

Answer 6

• Single –center rotation
• Double-center rotation
• Triple-center rotation
• Sliding center rotation

Question 7

single center of rotation

Answer 7

This technique used the stationary rotation center of the beam,
placed at one side of the jaws. The rotation center is then shifted
symmetrically by moving the patient. This projection technique
produced the split image.

Question 8

double center of rotation

Answer 8

The center of rotation was positioned anteriorly to the

location of the third molar opposite the side being examined

Question 9

3 centers of rotation

arc of jaws divided into?

Answer 9

 A condyle to first premolar posterior segment
 A canine to canine anterior segment
 A contralateral opposite segment

Question 10

triple centers of rotation

Answer 10

two are bilaterally
situated slightly postero lateral to the third molars, and the third one is situated
in the midline posterior to the incisor

Question 11

sliding or moving center of rotation.

Answer 11

The center of rotation changes as the film and tube head rotate
around the patient. the rotational change allows the image layer to
conform to the elliptical shape of the dental arches.

Question 12

what is a focal trough

Answer 12

It is a three dimensional curved zone in which structures are
clearly demonstrated on a panoramic radiograph.

Question 13

Image layer thickness depends on:

Answer 13

the effective

projection radius and the width of the beam

Question 14

what happens to Objects in front of or behind the focal trough

Answer 14

blurred, magnified or reduced in size

Question 15

Machines available in market

Answer 15

 The orthopantomograph 100 (Instrumentarium)
 The Orthophos Plus (sirona)
 The Orthoralix S (Gendex division Dentsply International)
 ProMax (PLANMECA)

Question 16

Positions of tube head and film

Answer 16

The Tube head always rotates behind the patient’s head as the
film rotates in the front of the patient

Question 17

Head positioner:

Answer 17

consists of chin rest, notched Bite-block,

forehead rest and lateral head supports

Question 18

what determines exposure factors

Answer 18

Exposure factors are determined by the manufacturer who suggests the (Kvp and Milliamperage).
The Kvp and milliamperage settings are adjustable and can be varied to accommodate patients of different sizes

Question 19

what factor is fixed in Panoramic xray and not in a intaroral xray

Answer 19

The Exposure time is fixed and can‟t be changed

Question 20

Examples of modifications in Panoramic xray

Answer 20

1. a Cephalometric attachment to allow exposure for frontal and lateral images of the TMJs and standard view of skull.
2. The computer controlled multimodality machines in which the direction and speed of movement of the tube head and film are highly variable, allows to be programmed to make tomographic
   views like maxillary sinuses and cross sectional views of maxilla and mandible.

Question 21

Components of Panoramic Xray unit

Answer 21

xray tube head
head positioner
image receptor
exposure parameters

Question 22

OPG films

Answer 22

 Screen film –it is sensitive to light emitted from intensifying screens.
 Screen films sensitive to green light-Kodak T-Mat G and Ortho G films.
 Screen film sensitive to blue light- Kodak X-Omat RP and Ektamat G films

Question 23

OPG film sizes

Answer 23

5x12 inch

6x12inch

Question 24

purpose of intensifying screen

Answer 24

 It increases the intensity of radiation on the film.

Question 25

types of intensifying screens

Answer 25

Calcium tungstate-emits blue light (faster)

Rare earth screens-emits green light

Question 26

Cassette

Answer 26

It holds the Extraoral film and intensifying film

Question 27

Image receptors in didgital opg

Answer 27

CCD

PSP

Question 28

What can a user modfy images

Answer 28

Both the digital modalities allow the user to perform post processing modifications on the image including linear contrast and density adjustments, black/white reversal, magnification, edge enhancement and color rendering.

Question 29

What software is used?

Answer 29

DICOM(Digital Imaging and Communication in

Medicine)

Question 30

Patient positioning

Answer 30

-Patient must be as straight as possible.
– The patient’s neck should be extended.
– Anterior teeth should be in the notch on the bite stick.
-The midsagittal plane should be perpendicular to the floor and aligned with the vertical center of the chin rest.
-Frankfort plane should be parallel to the floor, thus obtaining the correct position for the occlusal plane.
– Tragus of the ear must be aligned with the plastic guides.
-center the lower border of the mandible on the chin rest and is equidistant from each side

Question 31

Indications

Answer 31

As a substitute for full mouth intraoral periapical radiographs
Evaluation of trauma
Evaluation of tooth development in mixed dentition for children
Orthodontic treatment
Developmental anomalies
Third molars
 Large lesions like cyst, tumors.
Detection of fractures
 Generalized disease
 Inability to tolerate intraoral films
 Assessment for surgical procedure

Question 32

Contraindications

Answer 32

 Panoramic film are not as Defined or sharp as the images seen
on intraoral films. Can’t use where require
 Fine anatomical details
 Small carious lesions
 Fine structures of the marginal periodontium
 Periapical diseases
 For equal magnification

Question 33

Advantages

Answer 33

 Well-tolerated by patients
 Minimal time to expose when compared to intraoral
radiographs
 Broad anatomical coverage
 Relatively low patient dose
 For object localization in conjunction with occlusal
radiography

Question 34

Disadvantages

Answer 34

 Resolution is not as good as intraoral films.
 This results in loss of detail
 Superimposition of real/double images
 Only objects in focal trough are seen clearly
 Distortion of image
– Overlapped teeth
– Magnification
– Objects of interest outside of focal trough are distorted
and blurred

Question 35

how much magnification can be done

Answer 35

20 - 30% horizontal and vertical

Question 36

Bony landmarks of maxilla and surrounding structures

Answer 36

 Mastoid process
 styloid process
 External auditory meatus
 mandibular fossa
 Articular eminence
 Lateral pterygoid plate
 Pterygomaxillary fissure
 Maxillary tuberosity
 Infraorbital foramen
 Orbit
 Incisive canal and foramen
 Anterior nasal spine
 Nasal cavity
 Nasal septum
 Hard palate
 Maxillary sinus and its floor
 Zygomatic process of maxilla
 Zygoma 
 Hamulus
 Dentition

Question 37

Bony landmarks of amndible and surrounding structures

Answer 37

 Mandibular condyle 
 Condylar notch
 Coronoid process
 Ramus
 Mandibular foramen
 Lingula
 Mandibular canal
 Mental foramen
 Mental ridge
 Mental fossa
 Lingual foramen
 Genial tubercle
 Inferior border of mandible
 Mylohyoid ridge
 Internal oblique ridge
 External oblique ridge
 Angle of the mandible
 dentition

Question 38

Air spaces

Answer 38

Nasopharyngeal
Palatoglossal
Glossopharyngeal

Question 39

Soft tissue images

Answer 39

Tongue
Ear lobes
nasal cartilage
soft palate
nasolabial folds
soft palate and uvula
lip line

Question 40

Ghost spaces

Answer 40

 Cervical vertebrae
 Body, condyle and ramus of the contralateral side of 
the mandible
 Palate
 Chin rest
 (R)or(L) markers of the machine
 Neck chains
 Napkin chains
 Earrings, tongue rings
 Shoulder straps of protective apron

Question 41

Common double images include

Answer 41

– hard palate
– soft palate
– hyoid bone