Panaromic radiography

transcript

PANAROMIC RADIOGRAPHY

ByDr. Revath Vyas

MDS III year

CONTENTS• Introduction• Synonyms• Historical Development• Basic concept of tomography• Practical application of working principle• Focal Trough• Equipment and Patient positioning• Establishing exposure factors• Panoramic films, intensifying screens and Cassette• Normal Anatomy • Real and Ghost images• Advantages• Disadvantages• Common errors made in Panoramic Radiographs• Interpretation• Conclusion• References 2/60

SYNONYMS• Panoramic Imaging • Pantomography• Orthopantomograph• Rotational Panoramic Radiography• Dental Panoramic tomography

• The value of any diagnostic procedure depends on the amount and validity of the information that can be derived from it.

• The importance of intra oral radiograph in dental diagnosis is well documented. However, the intra oral radiograph is some what limited in the structures it covers.

• Panoramic radiographs do not replace the conventional dental film but when used as a supplemental diagnostic technique, it gives a good outcome due to its increased overall coverage of the dental arches and associated structures, reduced radiation dosage to the patient and simplicity of operation

Introduction

Panorama – “an unobstructed wide angle view of a region” 3/60

Historical backgroundThe first attempts to image the whole jaw was made with intraoral radiation sources at the beginning of 19th century in 1922.

Dr Host Beger of Germany Uses a small x-ray tube that can be introduced into thepatient’s mouth-patient, source &film are stationary.

Koch and Sterzel of Essen Germany (panoramix).Siemens corp. Erlangen, Germany (staters-x)Philips Medical systems, Inc, Holland (shot oralix)

1933 - Dr. H. Numata of Japan was the first to propose extraoral technique - He used intraoral curved films with the source rotating.

1948 - Dr. Yrjoveli Paotero used a long curved film inserted lingual to the teeth with the patient rotating - PARABOLOGRAPHY

1949 - Film extra orally – film and patient moved while source was stationary - PANTOMOGRAPHY

1950 – Robert J Nelson used Paotero’s parabolographic technique, used an intraoral film,with the source moving for posterior projections and patient+film stationary and vise versa for anteriors

1959 – Patero modified this technique with extraoral films – called it as Orthopantomography and the first orthopantomograph of clinical importance approved in 1960

First Orthopantomograph machine became available in 1961Comercially available Orthopantomograph machines are manufactured by Palomex ( Siemens Corp. Germany).Orthopantomo N-70 (Hilda Electric co) and Panoramax (Asahi Roentgen Co.)

Working principle• Employs scanography (slit beam) & tomography• Tomography: A term derived from greek words tomos

meaning “slice or section” and graphia meaning “picture”

Practical application of the working principle

ABCD move past the film with the same velocity in opposite direction – hence are sharply recorded on the film.

To obtain optimal image definition, it is crucial that the speed of the film passing the collimator slit is maintained equal to the speed at which the xray beam sweeps through the objects of interest.

• Stationary rotation centre Centers of Rotation

• Single rotation centre • Double rotation centre

3. Triple center of rotation – Panoram ; Panora4. Multiple centers of rotation – Ellipso pantomograph

VERTICAL PROJECTION

HORIZONTAL PROJECTION

Focal trough• It is an imaginary three- dimensional curved zone in which

structures are clearly demonstrated on a panoramic radiograph

Form And Thickness Of Image Layer

• A constant film speed in relation to the beam places the center of the image layer at a defined distance from the rotation center.

• The distance from the rotation center of the beam to the center of the image layer may be called the effective projection radius. The thickness of the image layer is dependent on the length of this radius.

• The longer the radius thicker the image layer, and is inversely proportional to the width of the beam.

Number of OPG units available which vary depending on

• Number of rotation centers• Size and shape of the focal trough• Type of films used

Equipment

• Units that follow the principle of stationary x ray source with rotating object and receptor.

• Eg : Tomax panaromic unit

Koch and Sterzel of Essen Germany (panoramix).Siemens corp. Erlangen, Germany (staters-x)Philips Medical systems, Inc, Holland (shot oralix)

• Orthopantomograph 10 E unit

• Patient in the sitting position.

• Panellipse unit• Patient in the standing

position.

PC1000Panoramic

Corporation

PROLINE 2002

Planmeca

ROTOGRAPH

Villa Sistemi Medicali

PANTOS

ARCOGRAPH

PANOURA ULTRA &

12Yoshida

ORTHORALIX

SDGendex

GX-PANGendex

OP5Siemens

OP10Siemens

ORTHOPHOS PLUSSirona

ORTHOPHOS 3

SironaAVANTEX

PANELIPSE

I & IIGE

EQUIPMENT

• Panoramic x-ray tube head • Head positioner • Cephalometric component• Exposure controls• Cassettes• Films

Planmecca pro EC

• The panoramic x-ray tube head is very similar to an intra oral x-ray tube head each has a filament used to produce electrons and a target used to produce x-rays.

• Collimator used in the panoramic tube head differs from the collimator used in intra oral x-ray tube head. Collimator used in panoramic x-ray machine is a lead plate with an opening in the shape of a narrow vertical slit through which x-ray beam emerges as a narrow band. Beam passes through the patients and then exposes the film through another vertical slit in the cassette carrier. Narrow x-ray beam emerging from the collimater minimizes patient exposure to x-radiation.

• Each head positioner consists of a chin rest, notched bite-block, forehead rest, and lateral head supports or guides.

Patient positioning• Patient should remove jackets or any bulky

clothing and metallic items from the head and neck region.

• Patient should sit or stand erect with back straight.

• The mid sagittal plane should be aligned with the vertical centerline of chin rest.

• The frankfort’s horizontal plane should be perpendicular to the floor

• The patient is asked to bite on the bite block with the upper and lower incisors.

• The red guide light determines whether the jaws are in the image layer – it should fall on the mesial aspect of the canine tooth

• Explain to the patient how the machine works.• Have patient close the lips and place the tongue

against the roof of the mouth.

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 filmsDose to the patient 0.712mR

Intensifying screens and films• Intensifying screen is

a device that transfers X-ray energy into visible light; visible light in turn exposes screen film.

• Consists of base, phosphor layer, protective layer

• Base – Polyster plastic, measuring about 0.25mm.

• Reflecting coat - Titanium dioxide or magnesium oxide, measuring about 0.0254 mm.

• Phosphor layer – calcium tungstate, or rare earth materials. ( 40-100 mm)

» Terbium activated gadolinium oxy-sulphide» Thalium activated lanthanum oxybromide» Niobium activated Yttrium tantalate

• Protective coat – Polymer coat made up of cellulose (15-25 µm thick )

• Film screen combinations :

• SEmulsions sensitive to blue light – standard silver halide emulsions

Sensitive to green light – Orthochromatic emulsions

Sensitive to red light – panchromatic emusions

Sensitive to UV light – modified silver halide emulsions

• Cassettes : – Cassette is a device that is used to hold the extra

oral film and intensifying screens.– Cassettes may be rigid or flexible curved or

straight.– All the cassettes must be light tight to avoid film

from exposure

Real Ghost

Single DoubleGhost Image : Objects with high attenuationsmay in certain instances be observed in two positions in panoramic radiograph only one ofthese images is intended and the other is usuallyrejected to as a ghost image.

Ghost image in recognized by:

Unsharpness which is in horizontal dimension;Always projected at a higher position in the radiograph than its

real counterpart (because beam is directed from below)Image is always reversed.

Ghost images are formed of more radiodense objects because it is formed by objects that are out of focus and are usually obscured , hence more radiolucent objects fail to project in the radiograph as images.

Normal Anatomy• Real Or Actual Shadows:

These include:– Teeth– Mandible– Maxilla, including floor, anterior and posterior walls of the antrum– Hard palate– Zygomatic arches and zygoma– Styloid processes – Hyoid bone – Nasal septum and conchae– Orbital rim– Base of skull

• Important Soft Tissue Shadows:1. Tongue2. Soft Palate and uvula3. Lip Line4. Ear lobes

NoseNasolabial folds

• Air Shadows:

1. Palatoglossal air space 2. Nasopharyngeal3. Glossopharyngeal

• Ghost or Artefactual Shadows:

– Cervical vertebrae– Body, angle and ramus of the contra lateral side of the

mandible– Palate.

Ext. Auditory meatus

Mandibular condyle

Articular eminence

Coronoid process

Zygomatic bone

Ptregomaxillary FissureInf. orbital rimFloor of Max. sinus

Ant. wall of Max. sinusHard palate

Nasal fossa

Inf. Orbital canal and foramen

Zyg. process of Max.

Panoramic Innominate line (Infra temporal surface of Zyg. bone

Lat. ptreg. plate

Glenoid fossa

Inf. border of Man.

C- Spine

Mental foramen Hyoid bone

Inf. Alveolar canal

Ext. oblique ridge

Inf. nasal concha

Inferior nasal meatus

Dorsal surface of the tongue

Post. Wall of the pharynx

Soft palate

Lower lipUpper lip

Middle meatus

Ghost image of opposite Mandible.

Common errors• Errors in preparing the patient for film exposure• Errors in film exposure and processing.• Errors in handling the film.

Errors in preparing the patient for exposure• Errors caused when metallic objects

are not removed

Improper positioning of the patient

When the lips are not closed - lip shadow is seen.

When the chin is tipped too high - the maxillary teeth roots are superimposed,- the maxillary incisors appear blurred,- flattening of occlusal plane ( reverse smile line)

When chin is placed downward

When the chin is tipped too high - the mandibular incisors appear blurred,- the apices of the lower incisors are out of focus and blurred- one/both condyles may cut off from the radiograph- increased curvature of the occlusal plane (exaggerated smile line)

When patient is positioned too far forward – anterior to the focal trough

-The anterior teeth appear blurred, narrower and out of focus.- Spine is superimposed on the ramus area

When patient is positioned too far backward – posterior to the focal trough

-The anterior teeth appear blurred, broader and out of focus.- Ghost image of the mandibular spine is more prominent.

When patient’s head is tilted

-One side condyle appears larger than the other side.- The side tilted towards the xray tube is enlarged.

When the patient’s spine is not straight

It appears as a radio-opaque artifact in the centre of the film superimposed on the anterior region

Other Artifacts and Errors

IINTERPRETATION

Interpretation

Zone 1 : The teeth and the surrounding boneZone 2 : Nose&sinusZone 3: The inferior cortex of the mandibular body.

- Principles and practice of panoramic radiology by langland langlais & Morris47/60

Zone 4: The condyles are centered in this zone.

Zone 5: Ramus and Spine

Zone 6: The hyoid bone.

- Principles and practice of panoramic radiology by langland langlais & Morris48/60

• The Orthopantomograph should be viewed as if looking at the patient i.e. with the image of the patient’s left side on the operators right.

• Should be viewed on a view box with sufficient light.

• A thorough knowledge of the normal anatomical landmarks and the superimposed structures is mandatory.

• The potential artifacts associated with the patient and machine movement, patient positioning and unusual patient anatomy have to be identified and understood.

- Oral Radiology, Principles and interpretation; White & Pharoah (6th Edition)49/60

INTERPRETATION• Assess the periphery and corners of the image• Examine the outer cortices of the mandible• Examine the cortices of the maxilla• Examine the zygomatic bones and arches• Assess the internal density of the maxillary sinuses• Assess the structures of the nasal cavity and the palates• Examine bone the pattern of the maxilla and mandible• Alveolar processes and teeth

S Perschbacher. Interpretation of panoramic radiographs.Australian Dental Journal 2012; 57:(1 Suppl): 40–45

Condylar process and temporomandibular joint

Coronoid process Ramus

Body and angle followed by mandibular dentition and supporting alveolus

Mandible

Midfacial regionCortical boundary of the maxilla including the

posterior border

Pterygomaxillary fissure – maxillary sinuses

Zygomatic complex (inferior and lateral borders of orbit, zygomatic process, anterior portion of arch)

Nasal cavity --- conchae – Maxillary dentition and supporting alveolus

Cortical boundary of the maxilla including the posterior border

Pterygomaxillary fissure – maxillary sinuses

Zygomatic complex (inferior and lateral borders of orbit, zygomatic process, anterior portion of arch)

Nasal cavity --- conchae – Maxillary dentition and supporting alveolus

Advancements A new panoramic radiography system, in which a large

number of vertical strip images can be acquired with a semiconductor detector used to reconstruct high-quality images using the concept of tomosynthesis.

It uses SCAN-300FPC detector with 20 frames/degree of rotation.

Development of a new dental panoramic radiographic system based on a tomosynthesis method .Dentomaxillofacial Radiology (2010)

Cone beam computed tomography

Conclusion• Panoramic radiographs have proved to be good

adjuvant radiographs to conventional intraoral radiographs mainly because they produce a single tomographic image of facial structures that include both maxilla and mandible and their supporting structures..

• The diagnostic value of these films is increased considerably if clinicians are aware of their limitations and apply a systematic approach to its interpretation.

References• Principles of dental imaging – Langland Langlais & Morris• Oral radiology , Principles and Interpretation – White & Pharoah ( 4th , 5th & 6th edition)• Essentials if Dental Radiology – Eric Whaites (3rd Edition )• Textbook of Oral Radiology – Anil Govindrao Ghom.• Textbook of Dental and Maxillofacial Radiology – Freny R Karjodhkar ( 2nd edition )

Panaromic radiography

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