{..Orthopantomogram..}

{..Orthopantomogram..}

The orthopantomogram (OPG) accounts for 1.7% of radiographic examinations at our institution. A third of these referrals are from Accident and Emergency and the bulk of these are for the assessment of maxillofacial trauma. The vast majority of the remaining examinations comprise referrals for dental assessment and wisdom teeth assessment.

Radiographic interpretation of the OPG is dependent on the recognition of normal anatomy, an understanding of the technique involved, and an awareness of the tomographic artifacts that may arise from this technique.

TECHNIQUE

The OPG is more commonly known as a dental panoramic tomogram (DPT) .The technique involves conventional tomography and slit beam scanning so that the curved mandible is displayed as a flattened two-dimensional image, hence the term ‘panoramic’. It involves the following principals:
The patient remains stationary as the x ray tube and film both rotate around the patient
There is a continuous vertical beam of x rays during an exposure cycle, which is directed at a slight upward angulation of 8 degrees.
The patient has to be “positioned” correctly in the focal trough to allow the required dental features to be in focus.
The typical radiation dose is 0.016Sv (the equivalent to one chest x ray).
LIMITATIONS
The patient must also be positioned in the centre of the focal trough. Failure of positioning may result in horizontal magnification variations, which are most marked in the anterior region of the mandible: patient positioned too far forward results in more narrow anterior teeth; patient positioned too far back results in wider anterior teeth; if the patient is rotated, the structures on the side that it is rotated to will appear smaller in width compared to the opposing side ([ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]).
There is also superimposition of soft tissues, bony structures, air shadows and foreign objects. These will be discussed later in the anatomy section.

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

Patient Rotation

Imaging findings or procedure details

THE ABC GUIDE

A large number of anatomical structures appear on an OPG. For clarity, the following systematic approach to assessment is suggested:

A Anatomy, air shadows and artefacts
B Bony structures
C Check areas and calcification
D Dentition

A - ANATOMY
This section will demonstrate the soft tissue structures and air shadows that may be seen on an OPG, and introduce the concept of ‘ghost’ shadows. The bony anatomy of the OPG will be discussed in the next section.
SOFT TISSUES AND AIR SHADOWS
[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] demonstrates the main soft tissue structures seen on an OPG. These are usually outlined by air within the nasopharynx and oropharynx. On a technical note, the patient should place the tongue against the palate during the exposure. This is to prevent excessive radiolucency appearing in the glossopharyngeal air space, which may obscure bony detail.
GHOST SHADOWS
Ghost shadows are the projected image of a real bony structure to the opposite side of the image. These artefactual images will appear more indistinct, magnified and slightly higher (due to the upward angulation of the x ray tube) than the original structure. All bony structures have a ghost shadow. The main ghost shadows visible on an OPG are those of the hard palate, posterior mandible and cervical spine ([ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]).
Foreign bodies, commonly ear rings, may also cause ghost shadows ([ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]).

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

soft tissue

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

Ghost images

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

........... to be continued

موضوع جدا رائع

يسلمو

في انتظار المزيد...

very nice

thank you for your effort

waiting for the rest of the subject

regards,

زهرة البنفسج كتب:: موضوع جدا رائع

يسلمو

في انتظار المزيد...

أهلا ..

الله يسلمك

.

نورتِ

Dr.Dorsy كتب:: very nice

thank you for your effort

waiting for the rest of the subject

regards,

Welcome my dear,

.

flower

B - BONY STRUCTURES

For convenience, the radiographic anatomy of the bony structures has been divided into those related to the mandible ([ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]), maxilla and temporal bone ([ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]) and those of the surrounding structures ([ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]).
A standard OPG will depict the whole mandible. The head of the
mandibular condyle is often obscured by the superimposition of the skull
base. It is important not to confuse normal structures for pathology.
For example, the mental foramen may be superimposed over the apex of the
lower second molar and may mimic a periapical inflammatory lesion.
Also, check that the inferior dental canal is well shown.
An OPG will also depict the maxillary sinuses in a predominantly
lateral profile. The floor and lateral walls of the maxillary antrum are
usually well seen, but the superior (infraorbital) is also often
discernible. The zygomatic buttress is also seen as a radio-opaque line
at the lateral aspect of the antrum ([ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]).

Mandibular structures

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

Figure 6

Maxillary, Temporal and Zygomatic structures

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

Figure 7

To be continued, ....