Panoramic radiography OPG

Seminar no: 12

Dr Sanjana RavindraOral Medicine and RadiologyRajarajeswari Dental College

and Hospital, Bangalore

CONTENT

S Introduction

History

Terminologies

Principle

Concepts in panoramic radiology

Equipment

References

Positioning requirements

Anatomical landmarks

Errors

Indications

Advantages & disadvantages

Modifications

Department library

References

INTRODUCTION

INTRODUCTION

INTRAORAL

Intraoral periapical

radiography

Bitewing radiography

Occlusal radiography

EXTRAORAL

2D radiography

3D radiography

Dental radiography is the art and science of making shadow pictures of the teeth and surrounding structures.

PANORAMIC RADIOGRAPHYPanoramic

radiography

Orthopantomography

Pantomography

Rotational radiography

SYNONYMS

A radiographic procedure that produces a single tomographic image

of facial structures including both maxillary and mandibular arches and

their supporting structures

PAN TOMO GRAPHY

wide to writeslice

HISTORY

The use of an

intraoral source of radiation

The use of an

extraoral source of radiation

Horst Beger ;Germany- The radiation is directed from inside the mouth through the jaws and exposes a film molded to the outside of the face of the patient.

Dr. Walter ott: Intraoral x ray tube in 1946.

Dr. Sidney Blackman : Panograph

Dr. H.Numata - He placed a curved film in the mouth lingual to the teeth and used a slit or narrow x ray beam that rotated around the patient’s jaws to expose the film.

HISTORY

Status x-ray intra oral source machine

HISTORY

HISTORY

In 1933 Dr. H Numata of Japan - first to propose the rotational panoramic

radiography method

In 1946 Dr. Yrjo. V. Paatero Proposed, experimented in 1948 and demonstrated (1949) a slit beam

method of panoramic radiography for dental arches

HISTORY

While the patient moved by means of a rotating chair; the exposure was made by a narrow beam of x rays emitted through a slit collimator.A separate radiograph was taken for each jaw. The x ray source was stationary.

In 1949; Paatero observed that panoramic radiographs could be taken with PARABOLOGRAPHIC technique : by placing the film extraorally; the film cassette and patient revolves with same velocity on a single vertical axis and the x ray source remained stationary.

The patient sits or stands immobile while the x ray tube rotates behind the neck and a curved film cassette moves around the face; rotating on its own axis.

ORTHORADIAL JAW PANTAMOGRAPHY/ ORTHOPANTAMOGRAPHIC SYSTEM

OPG 3 : First commercially manufactured

orthopantamogram (1961)

OPG 5: First unit to use light lines to accurately

position patient’s arch(1979)

OPG 10: rare screens1995 - DXIS, the world wide first dental digital

panoramic x-rays system

White and company marketed first panoramic machine –Panorex

TERMINOLOGIES

AMPERE: the unit of intensity of an electric current produced by 1 volt(V) acting through a resistence of 1 ohm

ATTENUATION: the process by which a beam of radiation is reduced in energy when passing through matter

COLLIMATOR: beam- limiting device for restricting the field of x-ray photons in a beam to a desired shape and size

FOCAL SPOT: that part of the target of anx-ray tube that is bombarded by the focussed electron stream when the tube is energized

RADIATION ABSORBED DOSE(rad): a unit of measurement for the absorbed dose of any type of ionizing radiation in any medium

TARGET (x-ray tube): the part of the anode in an x-ray tube toward which electrons from the cathode are focussed and attracted and where they interact to produce x-radiation.

TOMOGRAPHY

TOMOGRAPHY

Tomography is a specialized technique for producing radiographs showing only a section or slice of a

patient

Each tomograph shows the tissues within that section sharply defined and in focus. The section is thus referred to as the focal plane or focal trough.

Structures outside the section (i.e. the rest of the loaf) are blurred and out of focus. By taking multiple slices, three-dimensional information about the whole patient can be obtained.

Production of each conventional tomographic

slice requires controlled, accurate movement of

both the X-ray tubehead and the film during the

exposure, thereby differing from all the techniques

The main clinical indications for conventional tomographic sectional images in dentistry include:

Assessment of jaw height, thickness and texture before inserting implants

Postoperative evaluation of implants

Assessment of the size, position and extent of antral tumours

Evaluation of grossly comminuted facial fractures to determine all the fracture sites

Assessment of the extent of orbital blow-out fractures

As an additional investigation of the TMJ and condylar head — particularly useful if patients are unable to open their mouths, since most other radiographs of the TMJ require the mouth to be open

In conjunction with arthrography of the TMJ.

TOMOGRAPHY

TOMOGRAPHY

TOMOGRAPHIC MOVEMENT

All other structures will appear blurred or out of focus

The point (O) at the centre of this rotating movement will appear in focus on the resultant radiograph, since its shadow will appear in the same

place on the film throughout the exposure.

During the exposure, the X-ray tubehead moves in one direction around the patient while the film moves in the opposite direction.

Tomography requires controlled, accurate movement of both the X-ray tubehead and the film. They are therefore linked together.

TYPES OF TOMOGRAPHIC MOVEMENT

Linear Circular Elliptical Spiral

Hypocycloidal.

BROAD-BEAM LINEAR TOMOGRAPHY

A very thin X-ray beam producing one point (O) — the centre of rotation — in focus on the film.

To produce a section or slice of the patient in focus, a broad X-ray beam is used.

For each part of the beam, there is a separate centre of rotation, all of which lie in the same focal plane.

The resultant tomograph will therefore show all these points sharply defined

WIDTH/THICKNESS OF THE FOCAL PLANE

The thickness of the focal plane is determined by the

amount of movement, or angle of swing, of the

equipment.

The larger the angle of swing, the thinner the section in

focus, while the smaller the angle of swing the thicker the

section.

PRINCIPLE

Rotational panoramic radiography is accomplished by rotating a narrow beam of radiation in a horizontal

plane around an invisible rotational axis that is positioned intraorally

Here, a vertical narrow beam is used compared to larger circular/

rectangular x-ray beams used in conventional intraoral radiography

This is a curvilinear variant of conventional tomography, and is also based on the principle of the reciprocal movement of an X-ray source and an image receptor around a central point or plane, called the image layer.)

In panoramic radiography the image confirms to the shape of the dental arches.

PRINCIPLE

PRINCIPLE

• Movement of the film and tube head

produces an image through the process –

Tomography

• Tomography – radiographic technique

that allows the imaging of one layer or

section of the body while blurring images

from structures in other planes

In panoramic radiography, this image conforms to the shape of dental arches

WORKING PRINCIPLE

Principle of projection in the plane of rotation

Principle of projection in the vertical plane

Principle of layer formation

The panoramic radiograph is unique in that the foci of the projection in the vertical and horizontal dimensions are not the

same.

In horizontal dimension it is the rotation center of the beam that constitutes the functional focus.

In vertical dimension it is the x-ray source.

1. Principle of Projection in the plane of Rotation

Rotational panoramic radiography was developed to obtain a

projection geometry similar to a central projection.

In central projection the divergent rays

have a common origin at a focal spot and

film is perpendicular to the central ray.

Central projection with intraoral source.

In panoramic radiography, the film or cassette carrier and the tube head are connected and rotate simultaneously around a patient during exposure.

The pivotal point or axis, around which the cassette carrier and X-ray tube head rotate is termed a rotational center.

Three basic rotational centers used in panoramic x-ray

machines

1. Double – center rotation

2. Triple –center rotation

3. Moving –center rotation

A, Double-center rotation machines have tworotational centers, one for the right and one forthe left side of the jawsB, Triple-center rotation machines have three

centers of rotation and create an uninterruptedradiographic image of the jawsC, Moving-center rotation machines rotatearound a continuously moving center that issimilar to the arches, creating an uninterruptedimage of the jaws

PRINCIPLE

Double – center rotation Triple – center rotation Moving – center rotation

Single center of rotation

cassette shield with

narrow vertical slit

tube head

rotation

film/cassette

movement

Double Center of rotation

Triple-center

rotation

●

●

●

Beam first rotates around a laterally positioned

rotation center which serves as a functional focus

while major part of the opposite is exposed

●

●

●

●

The anterior region is now exposed with this second

rotational center as the functional focus

●

●

●

●

Rotation center is once more shifted so that the

projection of the jaws is symmetric on both sides

●

2. Principle of projection in the Vertical plane

Vertical dimension is unaffected by the rotation of the beam in the horizontal plane.

In this dimension, the x-ray source serves as the functional focus of the projection.

Slight negative angulation; passes beneath occipital area (-4 to -7 degrees)

3. Principle of layer formation

In Rotational panoramic radiography, the film is not stationary. Film is attached to the rotating system and

moves in the same direction as the beam, although at a slower speed.

If film speed is slow, this affects the length of the image recorded on the film, so that the registered

image is foreshortened in the direction of the movement.

By carefully choosing the speed of the moving film, it is possible to reduce the horizontal

magnification until it just matches the vertical magnification for one particular curved plane within the

object.

A. Successive rays do not

project a given point in

the sharply depicted

plane at the same spot

along the film path. As

the beam moves

through positions 1,2

&3, the projection of a

point moves through

positions A, B&C

along the film path.

A. If film moves at

the same speed at

which the

projection of the

object point

moves along the

film path, the

object will be

recorded as a

single point on the

film.

Principles of Panoramic Image Formation

Two adjacent disks are rotating at the same speed in opposite directions as an x-ray beam passes

through their centers of rotation.

Lead collimators in the shape of a slit, located at the x-ray source and at the image receptor, limit the

central ray to a narrow vertical beam.

Radiopaque objects A, B, C, and D stand upright on disk 1 and rotate past the slit.

ILLUSTRATION

The objects are displayed sharply on the receptor because they are

moving past the slit at the same rate and in the same direction as

the receptor.

ILLUSTRATION II

The same relationship of moving film to image is achieved if disk 1 is held stationary and the x-ray source is

rotated so that the central ray constantly passes through the center of rotation of disk 1 and simultaneously,

both disk 2 and the lead collimator (Pb) rotate around the center of disk 1.

Although disk 2 moves, the receptor on this disk also rotates past the slit.

To obtain optimal image definition, it is crucial that the speed of the receptor passing the collimator slit (Pb) be

maintained equal to the speed at which the x-ray beam sweeps through the objects of interest.

As the tubehead rotates around the patient, the x-ray

beam passes through different parts of the jaws,

producing multiple images that appear as one

continuous image on the film (“panoramic view”). When

you click the mouse, the tubehead will rotate around the

patient and produce the images. The red dots represent

the sliding rotation center.

The film above shows the left side of the patient

on the left. We normally look at the film as if we

were facing the patient, so that the patient’s

right side is on our left. Click the mouse to

rotate the film into the correct orientation for

viewing .

In panoramic radiography, the film or cassette carrier and the tube

head are connected and rotate simultaneously around a patient

during exposure. The pivotal point or axis around which the cassette

carrier and the X-ray tube head rotate is termed as rotation center.

The Rotation center concept has advanced from Stationary to

Continuously moving to combined stationary and moving rotation

centers.

ROTATION CENTER

TWO CENTERS OF ROTATION:

This follows the principle that the individual right

and left sides of the arc formed by the teeth and jaws

closely form a part of a circle. It was suggested that

the center of rotation be positioned somewhat

anteriorly to the location of the third molar opposite

the side being examined.

This double rotational principle was used in

Panorex machine.

THREE CENTERS OF ROTATION

Three centers of rotation system divide the arc

of the jaws into three areas:

- A condyle to the first bicuspid posterior

segment

-A cuspid to cuspid anterior segment

- A contralateral posterior segment

These three curved segments have three

different centers: two are bilaterally

situated slightly postero-lateral to the

third molars and the third is situated in

the midline posterior to the incisors.

The X ray beam can be shifted from one

center to the other without any

interruption and a continuous image can

be made from condyle to condyle.

Most panoramic machines now use a continously moving centre of rotation rather

than multiple fixed locations.

All these machines employ a moving rotational center that traces a path of the

shape of an ellipse. Therefore this system is also called “ellipso-pantomography”

MOVING ROTATIONAL CENTER:

IMAGE LAYER or FOCAL TROUGH

The image layer is a three-dimensional curved zone, where the

structures lying within this layer are reasonably well defined on

final panoramic image.

Objects outside the image layer are blurred, magnified, or reduced

in size and are sometimes distorted to the extent of not being

recognizable.

In panoramic tomography, focal trough is designed to be

approximately horseshoe shaped, corresponding to the shape of

the dental arches.

Focal trough

• The focal trough is narrowest at

the anterior region

• The focal layer usually follows

the actual anatomy of the

human jaw

Arc path

Velocity of the receptor

and x-ray tube head,

Alignment of the x-ray beam, and

Collimator width.

The factors that affect its size are :

Distance from rotation center of the beam to the central plane

of the image layer has been called the effective projection

radius.

The thickness of the layer depends on the length of this radius;

the longer this radius, the thicker the layer.

Thus altered film speed relative to beam changes the position

and thickness of the layer.

A constant film speed in relation to the

beam places the central plane of the

image layer at a defined distance from

the rotation center of the beam.

If the speed of the film is increased,

the position of the layer shifts away

from the rotation center.

If the speed of the film is decreased,

the position of the layer shifts towards

the rotation center.

EQUIPMENT

EQUIPMENT

X-ray tube head

Head positioner

Exposure controls

Image receptors

X-ray tube head

Head positioner

Exposure controls

Image receptors

TUBEHEAD ASSEMBLY

Tightly sealed, heavy metal housing

Metal housing

Insulating oil

Alluminium Disc

Lead collimation

Position indicating

device

Consists of a tube head which is similar to an intraoral x-ray

tube head

collimated beamCollimator

target(x-ray source)

COLLIMATION

Dental x-ray beams are usually collimated to a circle 23/4 inches (7cm.) in diameter.

metallic barrier with a aperture - reduce thesize of an x-ray beam and thereby thevolume of irradiated tissue within the patient

lead plate with a central hole - fits directly over the opening of the metal housing where the x-rays exit.

restrict the size & shape of the x-ray beam - reduce exposure to the patient.

COLLIMATOR

intraoral

collimation

panoramic

collimation

In order to limit the exposure to the patient, the x-ray beam is collimated. The collimator controls the size and shape of the x-ray beam.

Intraorally, the x-ray beam is either round or rectangular and is large enough to cover the entire intraoral film.

The collimator for panoramic radiography produces a narrow, rectangular x-ray beam that exposes a small portion of the film as the tubehead and

film rotate around the patient.

HEAD POSITIONER:

Chin rest

Notched bite-block

Forehead rest

Lateral head support guides

EXPOSURE PARAMETERS

• Kvp - 72 ; mA - 8 ; Exposure time 18 sec

Dose to the patient - 0.103mR

• Kvp - 80 ; mA 15 ; Exposure time 15 sec

Dose to the patient - 0.116mR

• In case of full mouth examination with 14 intraoral films

Dose to the patient 0.712mR

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

The Exposure time is fixed and can‟t be changed

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.

Two sizes:

5x12 inch

6x12inch

SCREEN FILMS

INTENSIFYING SCREENS

Phosphors are materials which convert photon energy to light.

Intensifying screens make use of the principle of fluorescence (emission of visible light).

Certain inorganic salts or phosphors (e.g. Magnesium Oxide or Titanium Dioxide or Calcium Tungstate) have the property of absorbing X-ray photons and emitting visible light.

An intensifying screen is a plastic sheet coated with fluorescent material called phosphors

Less than 1% of the incident x-rays interact with the film to contribute to the latent image

The sensitivity of film to direct x-ray exposure is low

Intensifying screens convert the remnant radiation to visible light to produce the latent image

Act as an amplifier of the remnant radiation

An intensifying screen and film combination makes the image receptor system 10 to 60 times more sensitive than when the film is used alone.

Hence, large exposure doses will be required to produce an image

Hence, lower radiation dose will be sufficient to produce an image

Conventional radiographic cassettes have a pair of intensifying screen that sandwich the film.

This design uses double emulsion films.

Radiographic assembly

X-ray

Patient

X-rays containing information of the patient

Strike the intensifying screen

Screen absorb energy from the x-ray beam and converts it to a light pattern that has the same information as the striking x-ray beam

Light forms latent image on film

It holds the Extraoral film and intensifying film.

It may be-

rigid or flexible

curved or straight

It must be light –tight to protect the film from exposure.

One intensifying screen is placed on each side of

film and held in place when the cassette is

closed.

CASSETTE

These transmits an electric signal to the controlling computer,which displays the image on

computer screen.

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.

DIGITAL IMAGE RECEPTORS

CCD (charge coupled device) or

PSP (photostimulable storage phosphor)

PC1000 PROLIN ROTOGRAP PANTO ARCOGR PANOURA ORTHOR

Panoramic E 2002 H S APH ULTRA& ALIX

Corporation Planmeca Villa Sistemi Bluex Imago 12 SD

Medicali Yoshida Gendex

GX-PAN

Gendex

OP5

Siemens

OP10

Siemens

ORTHO

PHOS

PLUS

Sirona

ORTHOPH

OS 3

Sirona

AVANTEX

BMT

PANELIPS

E

I & II

GE17/60

CONCEPTS

CONCEPT 1: STRUCTURES ARE FLATTENED AND SPREAD OUT

CONCEPT 2 : MIDLINE STRUCTURES MAY PROJECT AS SINGLE IMAGES OR DOUBLE IMAGES

CONCEPT 3 : GHOST IMAGES

CONCEPT 4 : SOFT TISSUE OUTLINES ARE SEEN

CONCEPT 5 : AIR SPACES ARE SEEN

CONCEPT 6- RELATIVE RADIOLUCENCIES AND RADIOPACITIES ARE SEEN

CONCEPT 7: PANORAMIC RADIOGRAPHS ARE UNIQUE

CONCEPTS IN PANORAMIC RADIOGRAPHY

Panoramic imaging produces numerous anatomical relationships in the image that are not found in any other kind of radiographic projection.

The structures of the maxillofacial complex as

well as the spine are portrayed as if they were

split vertically in half down the midsagittal

plane with each half folded outwards such

that the nose remains in the middle ;the right

and left sides of the jaws are on each side of

the film.

The spine ;having been split in half appears

beyond the rami at the extreme right and left

hand edges of the film

CONCEPT 1: STRUCTURES ARE FLATTENED AND SPREAD OUT

The midline of the film corresponds to the anterior midline of the patient and right and left hand edges correspond to the posterior midline of the patient.

The right and left halves of the jaws and maxillofacial complex can be seen side by side on the film without one half being superimposed on the other.

DESIRABLE EFFECTS

UNDESIRABLE EFFECTS

Improper positioning of the patient in the machine.

Eg: when the chin is tipped too low and the patient is positioned little back in the machine ;the hyoid bone is spread out and projected up; right on top of the mandible.

CONCEPT 2 : MIDLINE STRUCTURES MAY PROJECT AS SINGLE IMAGES

OR DOUBLE IMAGES

A real single image is formed when the anatomical structure is located in front of the rotation

center

Double images – occurs in the central portion of the oral and maxillofacial region in a diamond

shaped zone where objects are intercepted twice by beam

Five characteristics of double image

1. One image is mirror image of other

2. Both images are real images

3. Each image have similar proportions

4. Each image have same location on the opposite side

5. Double images only occur with midline objects

falling in the diamond shaped zone in midline


OR DOUBLE IMAGES

Structures that produce double

images

Hard and soft palate, palatal

torus, body of the hyoid bone,

epiglottis, and cervical spine


OR DOUBLE IMAGES

Formed when the object is located between the x-ray source and the center of rotation


Six characteristics of ghost image

1. Image has the same general shape as its real counterpart

2. Image appears on the opposite side of radiograph from

its counterpart

3. Image appears higher up on the radiograph than its real

counterpart

4. Image is more blurred than its real counterpart

5. Vertical component of ghost image is more blurred than

the horizontal component

6. Vertical component of ghost image is always larger than

its counterpart

Common ghost images:

• Spine

• Earrings, necklaces

• Inferior border of the

mandible

• Rami of mandible


Panoramic radiograph of an edentulous patient. The true image of the right mandibular angle is outlined by white arrows. The ghost image of the same structure is outlined using black arrows.

Detail of panoramic radiograph showing how theshadow of the spine can obscure detail of themandibular anterior teeth if the patientís neck is notkept erect during panoramic radiography

Bilateral earrings and their ghost images

Appearance of the earrings is dependent upontheir relative position with respect to the incomingX-ray beam. In this case, the right earrings arerotated so both the real and ghost images differ inappearance from the earring on the other side.

Sharp opaque images on the left side of the image are buckshot. The indistinct opaque images on the right side are ghost images

Tongue rings have become evermore frequent.The patient is often reluctant to remove thisdevice. It can case a radiopaque shadowupwards superimposed in the midline over thenasal passageway.

A lead apron raised up on the right shoulder has cast a radiopaque image on the left side of the image in the premolar region.

Sometimes it is not a bad idea to leave dentures with entirely radiolucent bases in place to facilitate patient positioning for panoramic radiography. In such cases the artificial teeth are usually radiopaque ñ but rarely hide important details so long as the patient is properly positioned.

Where denture bases are radiopaque the denture should always be removed prior to panoramic radiology being performed. Otherwise the primary image of the denture base will exclude necessary details from the interpretation.

This patient has not removed the eyeglasses and also has a unilateral earring on the left side. The primary image of the eyeglasses while not desired, probably does not obscure relevant information. The left earring has cast a ghost image over the maxillary right tuberosity region and obscures important information concerning an unerupted third molar tooth.

CONCEPT 4 : SOFT TISSUE OUTLINES ARE SEEN

Due to attenuation of the beam of radiations

Posterior and superior regions

Seen best in edentulous patients

Common soft tissue structures seen:

Ear, nose, epiglottis, cartilage, soft palate, uvula,tongue,posteriorpharyngeal wall etc

CONCEPT 5 : AIR SPACES ARE SEEN

• Hypopharynx, nasopharynx, oropharynx, maxillary sinus and nasal fossa.

• Occasionally mastoid air cells, external auditory canal, ethmoid air cells

CONCEPT 6- RELATIVE RADIOLUCENCIES AND RADIOPACITIES ARE SEEN

• Important to separate shadows originating from machine and

patient

• In patient - 3 basic components –hard tissue(teeth and bone),

soft tissue (including cartilage and fluid) and air

CONCEPT 7: PANORAMIC RADIOGRAPHS ARE UNIQUE

• Interpretive potential is more than full mouth iopar

• Interrelationship of structures are more accurate

• Excellent resource in patients with trismus and trauma

• Excellent projection of variety of structures in a single film

PROCEDURE

Explain the procedure to the patient

Make the patient wear a lead apron without a thyroid collar, and remove all objects from the head which will interfere with film exposure. Also have the patient remove jacket or bulky sweater, this allows more room between the bottom of the cassette holder and the patient’s shoulder

Patients should be asked to remove any earrings, jewellery, hair pins, spectacles, dentures or orthodontic appliances

Load the panoramic film in the dark room, and cover the bite block with a diposable plastic cover slip

Set the exposure factors and adjust the height of the machine to accommodate the patient.

• Instruct the patient to sit or stand with the back straight and erect, and ask him to bite on the plastic bite block.

• The upper and the lower front teeth must be placed in an end-to-end position in the groove of the bite block.

Less magnification horizontally (narrowing) more magnification horizontally (widening)

The midsagittal plane should be perpendicular to the floor and aligned with the vertical center of the chin rest, and the Frankfurt plane should be parallel to the floor, thus obtaining the correct position for the occlusal plane. (the patient’s head is tilted downwards so that the tragus ala line is 5° down and forward.)

If the patient has a low palatal vault, increase the occlusal plane angulation slightly, if the patient has a high palatal vault decrease the occlusal plane slightly. The indicator lights in the machine help as a guide and the patients head should be immobilized by the head band.

R L

Center the lower border of the mandible on the chin rest and is equidistant from each side.

Instruct the patient to position the tongue on the palate and ask him to remain still while the machine is rotating during exposure. Also explain that the cassette holder will not strike him, although it may gently rub his ear and head at the limits of the excursion.

After the exposure is complete the film is subjected to routine processing.

CLINICAL INDICATIONS

Selection criteriaIn the UK, the Selection Criteria in Dental Radiography booklet recommends a

dental panoramic tomograph (DPT) in general dental practice in the following circumstances:

As part of an orthodontic assessment where there is a clinical need to know the state of the dentition and the presence/absence of teeth • To assess bony lesions or an unerupted tooth that are too large to be demonstrated on intraoral films

• Prior to dental surgery under general anaesthesia

• As part of an assessment of periodontal bone support where there is pocketing greater than 5 mm

• Assessment of third molars, at a time when consideration needs to be given to whether they should be removed or not.Fractures of all parts of the mandible except the anterior region

• Antral disease — particularly to the floor, posterior and medial walls of the antra

• Destructive diseases of the articular surfaces of theTMJ

• Vertical alveolar bone height as part of preimplant planning.

The Selection Criteria booklet specifically states that 'panoramic radiographs should only be taken in the presence of

clinical signs and symptoms', and goes on to say that 'there is no justification for review panoramic examinations at

arbitrary intervals

As adjunct for full mouth IOPAR

Evaluation of tooth development (mixed dentition)

Assist and assess orthodontic treatment

Evaluate location of 3rd molar

Extensive disease – large lesions which cannot be seen in the intra oral radiographs

Evaluation of developmental anomalies, cysts, tumours

Evaluation of fractures following trauma

Assess underlying bone for pre and post prosthodontic treatment

Initial evaluation image in determining the need for other projections

To study the maxillary antrum

ADVANTAGES

ADVANTAGES Patient convenience and compliance.

In patients with trismus and gagging.

Minimum time required -3 to 4 min.

Maxilla, mandible and supporting structures seen.

Radiation dose is low -1/3 of IOPAR

Visual aid in patient education.

Better visual relationship of teeth with each other and adjacent structures.

Assessment of unerupted teeth.

Demonstrates periodontal disease in general way.

In localization of an object with other views.

DISADVANTAGES/ LIMITATIONS

DISADVANTAGES

Does not display fine anatomic details

Does not display fine carious lesions, periapical disease, fine structures of

periodontium.

Proximal surface of premolars overlap

Unequal magnification and geometric distortion

Presence of overlapping structures like spine.

Clinically important objects outside the line of focus distorted or not present

NORMAL PANORAMIC

ANATOMY

DIAGNOSTIC REGION

Zone 1: Dentition

Zone 2: Nose and Sinus

Zone 3: Mandibular Body

Zone 4: TMJ

Zone 5: Ramus-Spine

Zone 6: Hyoid

1

1. Condylar head 2. Sigmoid notch 3. Coronoid 4. External oblique ridge

5. Mandibular canal

2

3

4

5

6. Post. Border of Ramus 8. Lower border7. Gonial Angle

6

7

9. Mental ridge 11. Mental foramen 10. Genial tubercle

13. Lingula

12. Internal Oblique Ridge

14. Hyoid bone

8

9

1011

1213

15

15. Glenoid fossa

19. Floor of Max.Sinus

17. Zygomatic Arch16. Articular eminence 18.Post. wall max. sinus

20. Zygomatic process of max. forming inominate line

21. Hard palate 22. Floor of the orbit 23. Nasal septum 24. Incisive foramen

25. Inferior choncha 26. Meatus 27. Frontal process of Z.bone

16

1718

19

2021

2223

2925

24

26

28.Pterygo max. fissure

30. Maxillary tuberosity29.Spine of the sphenoid bone 31. Lateral pterygoid plate

31

30

28

27

32

32. External acoustic meatus 34. Shadow of ear lobe33. Styloid process

35. nose 36. Shadow of Cervical spine

33

34

35

36 36

36. Cervical vertebrae

37

37. Nasopharyngeal space 38. Shadow of uvula

39

38

39. Submandibular fossa

Inf. nasal concha (turbinate)

Inf. nasal meatus

Dorsal surface of the tonguePost. Wall of the pharynx

Soft palate

Lower lip

Upper lip

Middle meatus

Ghost image of opposite Man.

Soft tissue (edentulous)

COMMON ERRORS

Patient preparation errors

Metallic artifacts

Lead apron artifact

Thyroid collar

Patient positioning errors

Patient’s chin positioned too high or tipped up

• Hard palate and floor of the nasal cavity

appear superimposed over roots of

maxillary teeth

• Loss of detail in maxillary incisor region

• Maxillary incisor appear blurred and

magnified

• A reverse smile line is apparent on

radiograph


Patient’s chin positioned too low or tipped down

• Mandibular incisors appear blurred

• Loss of detail in anterior apical region

• Condyles may not be visible

• An exaggerated smile line is apparent

on radiograph


Positioning of teeth – anterior to focal trough

Positioning of teeth – posterior to focal trough


Mid-saggital plane error


Positioning of the spine


Positioning of the lips and tongue


Distortion due to patient movement

• Prolonged exposure of the same area

with increase in horizontal dimension

• A part of the object may be missing

• If patient moves up or down –

indentation of lower border of

mandible

• Blurring and unsharpness

Cassette positioning errors

• Alternating vertical dark and light

bands appear on radiograph due to

improper movement of slit in

cassette holder


Cassette placed too high Cassette placed too low


Double exposure Cassette placed backwards

Static electricity appears as black lines or dots on the film, often having a tree-branch appearance. It is caused by removing the film from the box or cassette too quickly, creating static discharge.

Static Electricity

Static Electricity

R L

This film shows two major errors, one of which is the interesting aliigator-like static electricity at the top of the film. The small black circles at the bottom of the film are also caused by static

The film is extremely underexposed. This was probably caused by placing the film outside the intensifying screens (not between them) in a flexible cassette.

ERRORS IN FILM EXPOSURE & DEVELOPMENT

LIGHT RADIOGRAPHS

Under Exposure

insufficient mA

Insufficient kVP

Under development

Depleted developer solution

Diluted/contaminated developer

Excessive fixation

DARK RADIOGRAPHS

Over Exposure

Excessive mA

Excessive kVP

Over development

developer conc. too high

Inadequate fixation

Improper safe light

MODIFICATION

Reverse Panoral Radiograph

Disadvantages

• Positioning of the patient is critical and difficult.

• Exposure to the eyes is more.

This technique of reverse panoral

radiography is one way in which a

panoramic X-ray machine is used to

provide a clearer and less distorted view

of the ascending ramus and it’s process

and the adjacent structures with the

mouth open or closed.

Computed Panoramic Tomography with Scanner Simulated Luminescence

Images obtained by panoramic tomography are characteristically blurred and not detailed enough to show fine bony abnormalities.

This new computed system is used to temporarily store the X-ray energy pattern.

The image receptor converts the latent image into digital signals which are processed and recorded onto the film.

Advantages

1. Reduced radiation exposure.

2. Better diagnostic quality.

3. Contrast and spatial frequency enhancement

DEPARTMENT LIBRARY

DEPARTMENT OF ORAL MEDICINE AND RADIOLOGY (RRDCH)

CONVENTIONAL DIGITAL

kVp – 60-90

mA - 3-16

Focal spot – 0.5mm

Magnification – 19% (1:1.19)

kVp – 85

mA - 10

Focal spot – 0.5mm

Magnification – 20% (1:1.2)

REFERENCES

REFERENCES

1. Rondon RHN , Pereira YCL , do Nascimento GC.Imaging Sci Dent 2014; 44 : 1-6.

2. Newadkar UR, Chaudhari L, Khalekar YK. Common errors on panoramic radiograph: A time to reflect and review and not to sweep them under the carpet!. SRM J Res

Dent Sci 2016;7:146-9.

3. Langland OE, Langlais RP, McDavid WD, Del Balso AM. Normal panoramic anatomy. In: Langland OE, Langlais RP, McDavid WD, Del Balso AM (eds). Panoramic

Radiology (2nd edn). Philadelphia: Lea & Febiger, 1989, pp 183–223.

4. Langland OE, Langlais RP, McDavid WD, Del Balso AM. Characteristics of different panoramic machines. In: Langland OE, Langlais RP, McDavid WD, Del Balso AM

(eds). Panoramic Radiology (2nd edn). Philadelphia: Lea & Febiger, 1989, pp 76–101.

5. Langland OE, Langlais RP, McDavid WD, Del Balso AM. Trouble shooting errors in panoramic techniques. In: Langland OE, Langlais RP, McDavid WD, Del Balso AM

(eds). Panoramic Radiology (2nd edn). Philadelphia: Lea and Febiger, 1989, pp 224–272.

6. Monsour PA, Mendoza AR. Panoramic ghost images as an aid in the localization of soft tissue calcifications. Oral Surg Oral Med Oral Pathol 1990; 69: 748–756.

7. Kaugars GE, Collet WK. Panoramic ghosts. Oral Surg Oral Med Oral Pathol 1987; 63: 103–108.

8. White S C, Pharoah M J. Oral Radiology Principles and Interpretation, 6th Ed. Mosby. 2006;175-190

9. Karjodkar F R. Textbook of Dental and Maxillofacial Radiology, 2st Ed. Jaypee Brothers Medical Publishers (P) Ltd. 2006:206-222

10. Haring JI, Jansen L. Dental Radiography Principles and Techniques, 2nd Ed. W. B. Saunders Company. 2001;125-130

11. Langland O, Langlais R P, Preece J W. Principles of Dental Imaging, 2nd Ed. Lippincott Williams & Wilkins. 2002:201-258.

12. Waites E. Essentials of Dental Radiography and Radiology, 3rd Ed. Churchill Livingstone. 2003: 161-176

13. Rushton VE, Rout J. Panoramic Radiology. Quintessentials publishing Co. Ltd London, 2006:2-67

14. Goaz PW, White SC. Oral radiology Principles and Interpretation 2nded.New Dehli B.I. Publications;1998:314-337

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