Extraoral Radiography - Panoramic

What is the purpose of a screening image in dental radiography?

To provide a broad overview of the general state of dentition and surrounding structures

What anatomical structures are typically included in a panoramic screening image?

Dentition, paradental bone, TMJs, maxillary sinuses, parts of the orbits, cervical spine, and skull base

What is one of the main uses of panoramic radiographs related to joints?

To assess the temporomandibular joints (TMJs)

What type of teeth can panoramic radiographs help evaluate?

Developing, supernumerary, and impacted teeth

How are panoramic radiographs useful in trauma cases?

They help identify dentoalveolar and maxillofacial fractures

What role do panoramic images play in assessing osseous pathology?

They help in the identification and localization of bone pathologies

How can developmental disturbances of the maxillofacial skeleton be evaluated radiographically?

Through panoramic screening images

What are some inherent limitations of panoramic images, similar to other 2D radiography?

Superimposition, magnification, and distortion

What is one major advantage of panoramic radiography in terms of anatomical coverage?

Broad coverage of the facial bones and teeth

How does the radiation dose of panoramic imaging compare to FMX?

Panoramic imaging has a lower radiation dose than FMX

Why is panoramic imaging considered more convenient than FMX?

It’s easier to perform, quicker, and more comfortable for the patient

In what situations is panoramic radiography especially useful over intraoral radiographs?

For patients with trismus or who cannot tolerate intraoral radiography

How is panoramic imaging useful in patient communication?

It serves as a visual aid for patient education and case presentations

What is one key disadvantage of panoramic images compared to FMX regarding image clarity?

They have lower resolution and less fine detail

Why are measurements unreliable on panoramic radiographs?

Due to unequal magnification across the image

What can make interpretation of panoramic images challenging?

Superimposition of real, double, and ghost images

Why is accurate patient positioning important in panoramic radiography?

To avoid errors and artifacts in the final image

What anatomical challenge can make panoramic imaging difficult?

Imaging both jaws in patients with severe maxillomandibular discrepancies

What was the original name Paatero gave to panoramic radiography?

Parablography.

What term did "parablography" evolve into before becoming orthopantomography?

Pantography

What was the final name Paatero gave to his panoramic imaging technique?

Orthoradial jaw pantomography, abbreviated as orthopantomography (OPG)

Under what trade name was panoramic radiography first produced commercially in the U.S.?

Panorex

Who were responsible for the commercial production of panoramic radiography in the U.S.?

Hudson, Kumpula, and Nelsen

Which company produced the Panorex unit?

S.S. White Co. (Pennwalt Corporation)

What does conventional tomography produce?

Radiographs showing a section or slice of a patient

What is the focal plane or image layer in conventional tomography?

The slice of anatomy that is in focus

What happens to structures outside the focal plane in conventional tomography?

They are blurred and not clearly visible

How is the image slice created in conventional tomography?

By controlled movement of the x-ray source and receptor during exposure

Is conventional tomography still used today?

No, it is no longer used

What modern imaging techniques are derived from conventional tomography?

Panoramic tomography and computed tomography (CT)

What connects the x-ray source and receptor in panoramic tomography?

A C-arm (gantry)

How do the source and receptor move during panoramic tomography?

They rotate around a rotation center and move synchronously in opposite directions around the head

What is the shape of the x-ray beam in panoramic tomography?

Narrow and slit-shaped

How is the receptor shaped to match the x-ray beam?

It is collimated to match the beam

What is special about the rotation center in panoramic tomography?

It is constantly moving

What does the movement of the rotation center help create?

A focal trough that matches the shape of the jaws

Why does a narrow, slit beam produce sharper images than a wide beam in panoramic tomography?

Because it reduces the amount of scattered radiation and improves image resolution.

What does the receptor collimator do in panoramic tomography?

It only allows the beam-sized portion of the receptor to be exposed at a time

How does a PSP/film receptor move during panoramic imaging?

It moves at the same rate as the x-ray beam through structures in the focal plane

How do direct digital sensors function in panoramic tomography?

They match the size/shape of the x-ray beam and are read out at the same speed the beam moves through structures in the focal plan

In panoramic imaging, how do the x-ray tube and receptor move?

The x-ray tube orbits around the back of the head, while the receptor orbits around the front of the face

Which side is the x-ray tube on during panoramic imaging?

The opposite side of the patient from the side being imaged

Where is the focal trough located in relation to the rotation center?

In front of the rotation center, closer to the receptor

What does a single center of rotation produce in panoramic imaging?

A half-circle, arc-like, non-anatomic focal trough

How is an anatomically shaped focal trough created in panoramic imaging?

By continuous movement of the rotation center

Where is the rotation center when the left TMJ is imaged?

Near the lingual surface of the right mandibular body

Where does the rotation center move when the midline is being imaged?

Anteriorly along an arc ending lingual to the mandibular symphysis

How is the arc of rotation reversed in panoramic imaging?

It reverses as the opposite side of the jaw is imaged

How is a panoramic image formed?

segment by segment in the vertical dimension

What is the hallmark sign of patient motion during a panoramic image?

Irregular or wavy vertical lines that should be straight and smooth

How does the width of the focal trough differ between anterior and posterior regions?

It is narrower in the anterior (~10 mm) and wider in the posterior (~30 mm)

Where are objects most sharply imaged in a panoramic radiograph?

In the center of the focal trough

What happens to objects located outside the focal trough?

They become blurred, distorted, and may appear magnified or reduced in size—sometimes to the point of being unrecognizable

What factors determine the shape of the focal trough?

Path and velocity of receptor and source, x-ray beam alignment, and collimator width

What is the vertical angulation of the x-ray beam in panoramic imaging?

Approximately 8–10° upward (caudocranial)

How are posterior/lingual/palatal structures projected in the image?

They appear higher due to their proximity to the source

Can the spatial relationships on a panoramic image always be trusted to represent true anatomy?

No — the projection can distort relationships, e.g., between the IAC and molar roots

What causes distortion of object size and shape in panoramic images?

Beam divergence and the panoramic technique itself

Why are linear and angular measurements considered unreliable on panoramic images?

Because distortion and magnification are unequal across the image

What factors influence the degree of distortion in panoramic imaging?

• X-ray beam angulation

• Rotational center path

• Source-to-object distance

• Position of the object in the focal trough

• Patient anatomy and positioning

What determines vertical magnification in panoramic images?

The source-to-object distance

Is vertical magnification consistent for all objects within the focal trough?

Yes, it’s relatively constant (about 15–30%)

Is vertical magnification significantly affected by minor changes in patient position?

No, it is minimally impacted

What happens to objects at the center of the focal trough?

They appear the sharpest

What happens to objects outside the focal trough?

They become blurred, distorted, and may appear magnified or reduced

What determines the shape of the focal trough?

The path and velocity of the receptor and source, x-ray beam alignment, and collimator width

What is the typical vertical angulation of the x-ray beam in panoramic radiography?

8–10° upward (caudocranial

How are lingual/palatal structures projected on the image

They appear higher on the image

Why can spatial relationships on a panoramic image be unreliable?

Due to the angulation and magnification distortions

What determines vertical magnification in a panoramic radiograph?

Source-to-object distance

How consistent is vertical magnification for objects in the focal trough?

Fairly constant (~15–30%)

What happens to objects lingual to the focal trough?

They appear wider (closer to source)

What happens to objects buccal to the focal trough?

They appear narrower (closer to receptor)

Are anterior or posterior structures more affected by horizontal magnification changes?

Anterior structures

Where are real images formed?

Between rotation centers and the receptor.

Where are ghost images formed?

Between the rotation centers and the x-ray source

What are double images?

Two real images of structures imaged twice (e.g., hyoid bone, cervical spine, epiglottis

What is the appearance of the complete dentition on a panoramic image?

It appears similar to intraoral radiographs but with lower resolution

What dental issues can be seen in a panoramic radiograph?

Severe caries, periapical disease, and periodontal disease

What subtle dental issues might be missed on a panoramic radiograph?

Subtle caries or lamina dura and periodontal ligament spaces

How does interproximal overlap of teeth affect a panoramic image?

It can interfere with caries detection

What are some key structures visible in the maxilla on a panoramic radiograph?

Cortices, alveolus, hard palate, pterygomaxillary fissure, and maxillary sinuses

What is the pterygomaxillary fissure and its borders?

• Posterior border: lateral pterygoid plate

• Anterior border: maxillary sinus

What is the zygomatic process of the maxilla?

It is visible on panoramic images as a bony projection posterior to the maxillary arch

What other midface structures are visible on a panoramic radiograph?

Orbits, nasal cavity, nasopalatine canal, and incisive foramen

What mandibular structures are visible on a panoramic radiograph?

TMJ condyle, coronoid process, ramus, body and angle of mandible, alveolus, and inferior alveolar canal

What are some key mandibular foramina visible on a panoramic image?

Mandibular foramen and mental foramen

What should the patient do to prepare for a panoramic radiograph?

Remove earrings, jewelry, glasses, dentures, or appliances

How should the patient position themselves?

• Spine straight

• Bite upper and lower incisors edge-to-edge into bite tab groove

• Chin rested in chin support

• Head immobilized using temple supports

• Lips closed, tongue pressed against the hard palate.

What should the laser beam indicate about the patient’s positioning?

• Mid-sagittal plane should be vertical.

• Frankfort plane (tragus-outer canthus line) should be horizontal.

• Canine light should be between the upper lateral incisor and canine.

How long does the exposure take?

4–18 seconds

What happens if the patient's head is too far forward?

The incisors will be posterior to the focal trough, and the patient will be closer to the source, leading to magnification

What happens if the patient's head is too far back?

The incisors will be anterior to the focal trough, and the patient will be closer to the receptor, leading to minification

What does it mean if the patient's head is rotated?

One side of the image will have horizontal magnification (closer to source) and the other side will have horizontal minification (closer to receptor)

How does a canted head affect the image?

It tilts the line between the orbital floors and condyles, which affects the positioning of occlusal and hard palate planes

What happens when the patient’s tongue is not against the roof of the mouth?

A dark radiolucent air space may appear over the maxillary apices

What positioning error occurs when the patient’s spine is misaligned?

The cervical spine may appear as a ghost image over the chin or mandibular symphyseal region

What happens if the chin is tipped up?

The occlusal plane will be oriented lower anteriorly, and the image may show inverted occlusal plane, blurred nasal cavity, or apices

What happens if the chin is tipped down?

The occlusal plane will be oriented higher anteriorly, and the image may show exaggerated smile, anterior teeth overlap, and possible missing condyles

Define “real image”

Single image that lies between the center of rotation and receptor