PANORAMIC RADIOGRAPHY

Pantomograph 1951

Pantomography

Rotational radiography

History

– Dr. H. Numata (1933)– Dr. Y.V. Paatero (1946)

OPG

• Ortho - straight

• Panoramic - An obstructed or a complete view of the object in every direction

• Tomography – An exray technique for making radiographs of layers of tissue in depth, without the interference of tissue above and below that level

Single image of facial structures that

includes maxillary

and mandibular arches

and their supporting

structures.

Advantages…

• Broad anatomic coverage

• Low patient radiation dose

• Convenience of examination

• Used in patients unable to open mouth

Panoramic X-ray procedure

• requires less time

• causes no discomfort• is radiation hygienic• is painless and non-traumatic

• Panoramic x-rays use film/screen imaging systems which require 82% less radiation than an FMX

• Studies vary, but most agree that the newest panoramic x-rays machines will produce a film with the same radiation as one to two periapicals

• It is difficult for a patient to understand 16 to 22 different pictures of their teeth

• A panoramic film can be easily understood and helps to explain the diagnosis and treatment plan to the patient

• The median time required for X-ray examination

– Intraoral full mouth series 20 min

– two bitewings 5 min.

– panoramic: 3 min

• Some patients cannot tolerate intra oral films: a gagger or an apprehensive patient.

• Quicker diagnostics for an emergency patient.

Disadvantages

• Does not show fine anatomic details

• Magnification

• Distortion

• Overlapped image of teeth

• Expensive

Indications

• Evaluation of trauma

• Third molars

• Large lesions

• Tooth development

• Developmental anomalies

• Intolerant to intraoral procedures

OPG IS A

SCREENING RADIOGRAPH

Ext. Auditory meatus

Mandibular condyle

Articular eminence

Coronoid process

Zygomatic bone

Ptregomaxillary Fissure

Inf. orbital rimFloor of Maxillary sinus

Ant. wall of Maxillary sinusHard palate

Nasal fossa

Inf. Orbital canal and foramen

Zyg. process of Maxilla

Panoramic Innominate line (Infra temporal surface of Zyg. bone

Lat. ptreg. plate

Man. fossa

Inf. border of Mandible

C- Spine

Mental foramen Hyoid bone Inf. Alveolar canalExt. oblique ridge

All this diagnostic information is missed in intraoral X-rays

Hard Tissue

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)

All this diagnostic information is missed in intraoral X-rays

Factors for interpretation

• Principles of image formation

• Techniques of patient positioning

• Radiographic appearance of normal anatomic structures.

Primary slot

Aluminium filter

Secondary slot

Film / digital sensor

Filament

Focal spot

mAkV

Anode (+) Cathode (-)

Radiation beam

Principles of Image formation

Film

Object

Sou

rce

Principle

• X ray source is rotated, so the central ray constantly passes through the centre of rotation of disc 1.

• Both disc 2 and the film collimator rotate about the centre of disc 1.

• While disc 2 moves, film on this disc rotates past the slit.

Rotating X-ray source

Rotating andmoving receptor

Image layer(focal trough)

Moving X-raybeam

Focal trough

• Focal trough is a three dimensional

image layer in which structures are

reasonably well defined on panoramic

radiograph.

Focal troughFocal trough

Patient positioning

• Removal of all metallic objects

• Demonstrate the machine

• Draped with leaded apron

• Dental arches located in focal trough

• Midline positioning

• Chin placed in the chin rest

• Back and spine erect.