2 extra-oral radiography[1]

05/03/2305/03/23 Ossama El-ShallOssama El-Shall

Extra-oral Radiography

Dr. Ossama EL-ShallDr. Ossama EL-ShallProfessor and Chairman, Oral Professor and Chairman, Oral

Medicine, Periodontology, Diagnosis Medicine, Periodontology, Diagnosis and Radiology Dept., Faculty of and Radiology Dept., Faculty of

Dental Medicine Al-Azhar University , Dental Medicine Al-Azhar University , Cairo Egypt.Cairo Egypt.

E.mail address: [email protected] address: [email protected]


ContentsExtra-oral filmsIntensifying screenIntensifying screenCassettesExtra-Oral radiographic projections,Extra-Oral radiographic projections, (Plain radiographs).(Plain radiographs).Specialized radiographyExamination of salivary glandsExamination of maxillary sinusExamination of TMJ


Extra oral filmsExtra-oral films are the films placed extra-orally during exposure in order to exam the mandible, the maxilla, the TMJ and all the facial bones.

Extra-oral films usually supplied in special light tight boxes in quantities of 50 or 100 films and loaded in a special light protected holder (cassette) inside the dark room.


Extra-oral films used in dental purposes supplied in two main sizes:

1- 5X7 and 8X10 inches for examination of skull and jaws

2- 5X12 or 6X12 inches for panoramic radiography.


General indications of use of extra-oral films

1- Patients who cannot open their mouths sufficiently for insertion of intra-oral films due to any causes such as trauma of truisms.

2- Unco-operative patient such as mentally retarded and children.3- Examination of large pathologic involvement, such as large

cyst.4- Obtaining a large generalized view of jaws, sinuses and bones.5- Examination of fracture lines and extension of fracture in skull

bone.6- Localization of foreign bodies.7- Examination and diagnosis of TMJ disorder.8- Obtaining of generalized view of unerupted, impacted or

supernumerary teeth.


Types of extra-oral films.Types of extra-oral films.

Screen filmsScreen films

Non screen filmsNon screen films


Screen filmScreen filmIs used in combination with intensifying Is used in combination with intensifying screens. screens. These films are different from other dental These films are different from other dental films in that they are designed to be films in that they are designed to be particularly sensitive to particularly sensitive to visible lightvisible light rather rather than to X-radiation. than to X-radiation. This is because they are used by being placed This is because they are used by being placed between two intensifying screens. between two intensifying screens. The intensifying screens absorb X rays and The intensifying screens absorb X rays and emit visible light that exposes the screen film. emit visible light that exposes the screen film.


Non screen filmsNon screen films

Or direct exposure films; Or direct exposure films; they are more sensitive to x rays than to light.they are more sensitive to x rays than to light. It requires a longer exposure time as it It requires a longer exposure time as it depends on the depends on the x rays onlyx rays only to affect the film to affect the film not on any emitted light. not on any emitted light. It may be used for thin bones only such as It may be used for thin bones only such as long bone and mandible. long bone and mandible. However its use in dental radiography is not However its use in dental radiography is not recommended.recommended.


Extra-oral film Extra-oral film equipmentsequipments

Intensifying screenIntensifying screen

Cassette Cassette


Intensifying screenIntensifying screen

It is a device used to intensifies the It is a device used to intensifies the photographic effect of X-rays and thus photographic effect of X-rays and thus shortens the exposure time that otherwise shortens the exposure time that otherwise would be long to suit the thickness and would be long to suit the thickness and density of tissues in case of extra-oral density of tissues in case of extra-oral radiography. radiography.


The use of intensifying screen is based on three main principles:

X radiation have a biological damaging effect that should be protected through decrease the exposure time.Certain substances can cause fluorescence if it absorb X radiation.Photographic film is sensitive to both X radiation and visible light.


When x-rays strike intensifying screen, they immediately activate it so it emits light which is going together with the x-rays to expose the film.Thus the light produced by the screen intensifies the effect of the x-rays on the film and helps reduction of exposure time.The intensity of this fluorescence is directly proportional to the intensity of the exiting x-ray.


= phosphor crystal

film

Mechanism of action of the screen


Composition of intensifying screen:

Plastic or cardboard base.Reflecting layer: It is a layer of titanium oxide that covers the base of the screen and lies beneath the phosphor layer. Its function is to reflect any light emitted from the phosphor layer back to the film and thus increase the effect of the screen.The phosphor layer: It is the light sensitive crystals layer, it formed from Calcium tungestate or Barium lead sulphate (conventional type that emit a blue light) or formed from a rare earth phosphors as Gadolinium or Lanthanium (rare earth type that emit green light).Protective layer: made up of a plastic layer with smooth surface.


Intensifying Screen Composition

-Base (thick white line) = plastic for support

-Reflecting layer (red line) = reflects

light back

toward film-Phosphor layer (green line) = rare earth -Protecting coat (thin white line) = plastic

(10)

(this side toward film)


Types of intensifying screens:I- According to the phosphor layers:

Conventional screens: the phosphor layer made of Calcium tungestate or Barium lead sulphate and it emit a blue light. For example: Kodak X-Omatic screens.Rare earth screens: the phosphor layer made of rare earth phosphors, Gadolinium or Lanthanium and it emit a green light. For example: Kodak Lanex screens.


II- According to speed: (phosphor crystal size)

Slow: has the smallest crystals and give the best image details.Intermediate: Have larger crystals and less detail.Fast: The largest crystals and least details.


= phosphor crystal

film

Light Emission from the screen


Loaded Screen film

film


Cassettes

Cassette holder is another equipment necessary for the extra-oral films.

The extra-oral film is sandwiched between 2 intensifying screens of matching size and type and secured in a cassette holder.


Cassette and its contents

1. Cassette front: made of plastic, aluminum or carbon fibers to allows more rays to pass and thus reducing patient exposure.

2. Two intensifying screens.3. The screen film4. Felt padding: to assure intimate and even

contact between film & screens5. Cassette back: made of lead


Cross section of loaded cassette

Cassette front

Screen

Film

Screen

Felt padding

Cassette back


Cassette/Film


Types of cassettes according to their uses

1. Rigid cassette for skull views.

2. Rigid or flexible cassette for panoramic films

3. Occlusal cassettes for occlusal films when they are used extraorally.


Cassettes

Hold intensifying screens (2) in tight contact with film

Rigid (metal) or soft (vinyl)

Rigid metal cassette

Flexible vinyl cassette


Extra-Oral radiographic projections.Extra-Oral radiographic projections.

(Plain radiographs).(Plain radiographs).

Lateral skull projectionLateral skull projectionPosteroanterior projection: (PA). Posteroanterior projection: (PA). Mandibular Lateral oblique projections.Mandibular Lateral oblique projections.Water’s view: (occiptomental projection).Water’s view: (occiptomental projection).Reverse-Towne projection.Reverse-Towne projection.Submentovertx projection: (base view).Submentovertx projection: (base view).


Plain radiographs.Plain radiographs.Frankfort plane:Frankfort plane: It extended from the It extended from the anterior border of the external auditory anterior border of the external auditory meatus to the infra-orbital rim.meatus to the infra-orbital rim.

The canthomeatal line:The canthomeatal line: It is the line between It is the line between the central points of the external auditory the central points of the external auditory meatus to the outer canthus of the eye. It meatus to the outer canthus of the eye. It makes 10 degree with the frankfort plane. makes 10 degree with the frankfort plane. (radiographic base line)(radiographic base line)


Frankfort planeFrankfort planeCanthomeatal lineCanthomeatal line


Concerning the nomenclature of the Concerning the nomenclature of the film projection, the film projection, the firstfirst word of the word of the description is description is where the tube is;where the tube is; the the secondsecond word is word is where the film iswhere the film is i.e. PA i.e. PA film has the tube at the back of the film has the tube at the back of the head (P) and the film is placed by the head (P) and the film is placed by the face (anterior).face (anterior).


Lateral skull projectionLateral skull projection Lateral cephalometric, True lateral, Dead lateralLateral cephalometric, True lateral, Dead lateral

It used to survey the skull and facial bones for evidence of trauma, disease, or developmental abnormality.

This view reveals the nasopharyngeal soft tissues, paranasal sinuses, and hard palate.

Orthodontists use it to assess facial growth, and in oral surgery and prosthetics it establishes pretreatment and post-treatment records.


Lateral skull projectionLateral skull projection


Film placement: the film is positioned vertically in a cassette-holding device.

Head position: the head should be positioned with the side of the face near the cassette, the interpupillary line perpendicular to the film, and the midsagittal plane parallel to the plane of the film.

Projection of the central ray: It directed toward the external auditory meatus and perpendicular to the plane of the film and midsagittal plane. Therefore, superimposition of both sides of the skull, facial bones and mandible.

Lateral Cephalometric Identify trauma, abnormalitiesAssess facial growth; treatment record

film at set distance from MSPfilm horizontal

extraoral x-ray unit

MSP

floor

MSP


Patient and film position during lateral projection


Cephalometric MachineCephalometric Machine


Position of the patient in the cephalometric machine for lateral cephalometric film


Radiographic and photographic projections Radiographic and photographic projections superimposedsuperimposed


Posteroanterior projection: (PA)Posteroanterior projection: (PA)It is so named because the X-ray beam passes in a posterior-to-anterior direction through the skull.

It used to examine the skull for disease, trauma or developmental abnormalities.

It provides a good record to detect progressive changes in the mediolateral dimensions of the skull.

It also offers a good visualization of facial structures, including the frontal and ethmoid sinuses, nasal fossae, and orbits.


PAPA


Film placement: the cassette is positioned vertically in a hold in device in front to patient.

Head position: the head is centered in the front of the cassette with the canthomeatal line parallel to the floor and the tip of the nose and forehad are in contact with the cassette.

Projection of the central ray: the central ray is directed perpendicular to the plane of the film and coincident with the midsagittal plane of the head at the level of the bridge of the nose.


Patient head position in relation to the cassette during P.A projection

Posteroanterior (PA) SkullIdentify trauma, pathology, ordevelopmental abnormalities

FP

floor

MSP



Position of the patient for posteroanterior projection produced by cepalometric machine


Taken with intraoral x-ray machine. (Note round collimation). Not recommended, but possible.


It is a variant of the postero-anterior view.

It particularly used for evaluation of maxillary sinuses, in addition to frontal and ethmoid sinuses, the orbit, nasal cavity and the coronoid process of the mandible.

Water’s view Water’s view (Occiptomental projection)(Occiptomental projection)


Film placement: the cassette is positioned vertically.

Head position: the sagittal plane of the head is perpendicular to the plane of the film. The chin is raised to elevate the canthomeatal line 37 degrees above horizontal plane. A bite block is used to secure max. jaw opening.

Projection of the central ray: the central ray

should be perpendicular to the film, through the midsagittal plane, at the level of the maxillary sinus.



Water’s view (Occiptomental projection)

Waters

Evaluate the maxillary sinus

MSP

floor


(Sinus view)

tip of nose 1” from cassette

CR

FP


Position of the patient for Water’s view using cephalometric machine


Mandibular posterio-anterior viewMandibular posterio-anterior view(Reverse-Towne projection)(Reverse-Towne projection)

It used to examine a patient with a It used to examine a patient with a suspected fracture of the condylar suspected fracture of the condylar neck,neck, especially in cases of medially especially in cases of medially displaced condyle.displaced condyle.


Film placement: the cassette is positioned in a holding device in front to the patient.

Head position: the head is centered in front of the cassette with the canthomeatal line oriented downward 25 degree. The patient instructed to open his mouth as wide as possible to help visualize the condyles.

Projection of the central ray: the central ray is directed to the film in the sagittal plane through the occipital bone.


CM lineCM line RaysRays


Mandibular posterioanterior view(Reverse-Towne projection)


Mandibular posterioanterior view(Reverse-Towne projection)


Position of the patient for Reverse-Towne Reverse-Towne projectionprojection using cephalometric machine


N.B: Town’s projection is the antero-posterior one. It clearly defines all but the most superior parts of the condylar processes. Thus it often gives critical diagnostic aid in determining the presence of unilateral or bilateral condylar fractures, especially for the fractures running in the sagittal plane.


Submentovertx projectionSubmentovertx projection (base view) (base view)

This view used to exam the base of the skull, condyles, sphenoid sinus, curvature of the mandible, fractured zygomatic arch, and foramina of the base of the skull.


Film placement: the cassette is placed vertically in a holding device.

Head position: patient’s head is fully extended backward as far as possible with the vertex of the skull touches the center of the cassette.

Projection of central ray: the central ray is directed from below the mandible upward toward the vertex of the skull.



Submentovertx projection: (base view)Submentovertx projection: (base view)



Submentovertx projection Submentovertx projection (base view)(base view)

(Reverse-Towne projection)Occiptomental projectionPA

Water’s view Mandibular Posterioanterior view


Mandibular Lateral oblique projections.

They are two lateral oblique projections used to examine the mandible: one for the body and one for the ramus.

The film used in these projections usually a 5X7 inch (13X18cm) screen film and the cassette should be hand held by the patient.

Although these views have been replaced by panoramic radiographs, dentists still use them when an image with greater resolution is needed.


Mandibular body projection This projection demonstrates the premolar-molar region and

the inferior border of the mandible.

Head position: the head is tilted toward the side being examined.

Film Placement: the cassette is placed against the patient’s

cheek and centered over the first molar, its lower border parallel with the inferior border of the mandible extending at least 2cm below it and the patient can hold the cassette.

Projection of the central ray: The central ray is directed toward the first molar region from a point 2cm below the angle on the tube side.


The central ray is directed toward the first molar region from a point 2cm below the angle on the tube side.


Mandibular body projection


Mandibular Ramus Projection Mandibular Ramus Projection

It gives a view of the ramus from the angle of the mandible to the condyle.It is useful for examination of the third molar regions of the maxilla and mandible.


Head position: The head is tilted toward the side of the mandible being examined until a line between the mandible angle next to the tube and the condyle away from the tube (condyle of the side to be examined) is parallel with the floor. The patient asked to protrude his mandible to avoid superimposition of the cervical spine.

Film placement: The cassette is placed over the ramus and far enough posteriorly to include the condyle.

The lower border of the cassette should be parallel to the inferior border of the mandible and at least 2cm below it.

Projection of the central ray: The central ray is directed posteriorly towards the center of the ramus of the side of interest from a point 2cm below the inferior border of the first molar region of the other side


Mandibular Ramus Projection Mandibular Ramus Projection


Thank you all for listening

Dr. Ossama El-ShallAssociate professor of Oral Medicine & Periodontology,

Faculty of Dental Medicine, Al-Azhar University, Cairo, Egypt.

E-mail address: [email protected]


Specialized radiography


Specialized radiography.Specialized radiography.Panoramic radiography.Computed Tomography.Sialography.Ultrasonography.Magnetic resonance image.Nuclear medicine. (Radio nuclide imaging ) Digital imaging.Arthrography.Electronic thermography.Endoscopy.


Panoramic radiography rotational radiography, or curved surface

tomography

It is a radiographic technique for producing a single image of the facial structures that includes both maxillary and mandibular arches and their supporting structures.

PanoramaPanorama Panoramic radiography is an extraoral Panoramic radiography is an extraoral radiographic technique that is used to radiographic technique that is used to examine the upper and lower jaws on a examine the upper and lower jaws on a single filmsingle film . .

The film and the tubehead rotate The film and the tubehead rotate around the patient, producing a series around the patient, producing a series of individual imagesof individual images . .



As Tomographic principles, the x-ray tube and film cassette rotate in opposite directions around the patient’s head to produce a specific curved image of the maxilla and mandible on the film.



Panoramic principles are combination of Scanography and Tomography principles.

In order to understand the principle of panoramic radiography, we have to explain the meaning and principles of both Tomography and Scanography


Tomography

Conventional film-based tomography is a special radiographic technique designed to image more clearly objects lying in a plane of interest.

This is accomplished by focusing on the plane of interest and blurring the image of structures lying superficial and deep to this plane.

Word Tome in Greek = Section


Conventional tomography is applied primarily to high contrast anatomy, such as encountered in dental implant diagnostics.

In the other word, we can define the tomography as a radiographic presentation of a layer within the body while body structures above and below that layer are blurred out of focus.


Tomographic methods are divided into 2 major categories:

I- Conventional tomography.

II- Computerized tomography (C.T).


Scanography

Scanography is a process by which an x-ray tube and a dental film are linked together through a mechanical linkage and rotate around a fixed object (patient’s head).


In panoramic technique, during exposure, the x-ray source moves in one direction while the film moves in the opposite direction

The area of the object in the center of this movement will appears in focus and very sharp on the resultant radiograph as its shadow.

All other structures will appears blurred or out of focus



Advantage of panoramic radiography

1. Give a complete image for both jaws as well as cervicofacial bones to exam any abnormality such as, fractures, tumors, cysts, impaction anomalous of teeth , etc……..

2. Simple technique, as it requires less co-operation of the patient especially handicapped, children, and jaw-fractured patients.

3. Low patient radiation dose; it is about 3 times less than the amount received via full mouth Periapical survey (14 films).


4. Quick procedure, the time required to complete a panoramic radiographic examination is quite short, usually in the range of 3-4 minutes; this includes the time necessary for positioning and the actual exposure cycle (about22 sec.)

5. Panoramic films are readily accepted by patients as a visual aid in case presentation and for patient education.


Disadvantages:

The resultant Image does not resolve the fine anatomical details that may be seen on intra-oral Periapical radiographs.

Interproximal caries and changes of lamina dura can not be diagnosed in most cases due to lack of fine details and sharpness.

Magnification, geometric distortion and overlapped images of teeth, especially in the premolar region.


4. Due to superimposition of the spine, specially in short-necked patients, there is always lack of clarity in the central portion of the film (Ghost shadow appearance of the spine)

5. Soft tissues and air shadows can overlie the required hard tissue

6. High coast, 2-4 times that of an intra-oral X-ray machine.


Indications:

1. Overall view of the teeth and facial bones.2. Evaluations of trauma, extensive disease, tumor

extension, fracture, and gross swelling.3. It reveals fractures of the mandible from the

midline to the neck of the condyle.4. Cases of truisms, to locate or exam impaction,

pathology or fracture.5. It reveals the maxillary sinuses floor of the orbits

and nasal bone.


6. Uncooperative patient, such as children, or handicapped.

7. Full mouth survey instead of full mouth X-ray, 14 film.

8. Bilateral comparison of any pathology.

9. Orthodontic treatment

10. Evaluation of tooth development (especially in the mixed dentition), retained teeth or root tips (in edentulous patients), and developmental anomalies.


Contra-indications:

Panoramic films are not suitable for diagnostic examinations requiring high image resolution, such as detection of early bone loss, dental caries, periodontal diseases, or analysis of trabecular bone changes associated with early Periapical lesions.


Patient preparation and position for panoramic radiography

Remove all Radiopaque things such as; hairpins, earrings, removable partial dentures …..

Set the patient in upright position putting the head in focal trough guided by Bite block placed between upper and lower incisal edges.

So this brings the arches in the center of focal trough leading to correct anteroposterior direction of image.


Two ear rods to adjust midsagital plane in correct position to avoid any horizontal distortion of magnification of one side more than other.

Chin positioning to adjust Frankfort plane parallel to floor.

Demonstrate the machine movement to the patient especially to the children.

Instruct the patient to look forward and don’t follow the tube by his eyes.

Leaded apron






Computerized TomographyC.T.


C.T.1. Simply the computed tomographic scanner consists of a

multiple radiographic tubes with narrow beams that are mounted in a circular gantry opposite an array of scintillation receptors designed to accept these beams.

2. The patient is placed in the center of the gantry and the gantry rotates, allowing the x-ray beams to irradiate patient from various angles.

3. The receptors record the radiation passing through each small section of the patient and convert it into electric impulses, which are sent to a computer for storage and manipulation.




4. It provides excellent imaging of TMJ, salivary gland, facial fractures and lesions, and tumor extension and assists in the positioning of implants.

5. It completely eliminates the superimposition of images of structures superficial or deep to the area of interest within the patient.

6. It give a good differentiation between tissues due to its high contrast resolution

7. The main disadvantages of it that, anything denser than enamel produces serious artifacts. This causes some problems when examining the jaws of patients with metal restorations or implants.


Fracture zygomatic arch Rt. side


Coronal scanning of TMJ


Chronic sinusitis in max. sinus


Sialography

It is a technique whereby a radio-opaque contrast medium is injected into the main parotid or submandibular salivary gland duct via a cannula, in order to demonstrate the anatomy of the duct system.


Indications: 1-1- Chronic inflammatory diseases of salivary glands: Chronic inflammatory diseases of salivary glands:

A-A- Chronic obstructive inflammation : Abnormalitis in the main duct Chronic obstructive inflammation : Abnormalitis in the main duct due to obstructive agent either due to obstructive agent either calculus or non-calcifiedcalculus or non-calcified..

Sialography will aid in planning surgery i.e. deciding whether total or Sialography will aid in planning surgery i.e. deciding whether total or partial excision of gland should be performed.partial excision of gland should be performed.

B-B- Chronic non-obstructive: Sjogran’s syndrome & Recurrent parotitis. Chronic non-obstructive: Sjogran’s syndrome & Recurrent parotitis.

2-2- Detection of tumors. Detection of tumors.

3- 3- Detection of residual stones, residual tumor, fistula, or Detection of residual stones, residual tumor, fistula, or retention cyst following surgical procedure in salivary gland.retention cyst following surgical procedure in salivary gland.

4-4- Detection of congenital defect such as atrophy and Detection of congenital defect such as atrophy and hyperatrophy.hyperatrophy.


Contraindications:

1- Sensitivity to iodine compounds of the contrast materials.

2- During acute inflammation of salivary system; where may be disrupted leading to escape of contrast material from ducts into parenchyma inducing severe foreign body reaction and pain.

3- The iodinated contrast medium may interfere with thyroid function tests; hence they should be performed prior to sialography.


Complications:

1- Spread of infection, discomfort, and pain.

2- Extravasations of contrast medium may result in foreign body reaction.


Radio-opaque contrast materials:

It is a diagnostic agent appears Radiopaque in radiographs. It injected in the salivary glands and its duct systems to exam them radiographically.

Specifications of contrast media:1. Sufficient radio-opacity to represent the fine structures.2. Must have physiologic properties similar to saliva, to

facilitate penetration into the fine ducts.3. Low viscosity to allow filling of the ductal system.4. Rapid absorption of the residues by blood and excretion

by the kidney and salivary gland.5. Non-toxic and easy to detoxicated by the liver.


It may be one of the following:

Water-soluble.

Fat- soluble.

Suspension media.


Water soluble (most preferable), e.g.: Renografin, Sinografin, Hypaque.

They have the following advantages:1. Low viscosity, so they can fill the ductal system with

little pressure.2. Rabidly absorbed by blood.3. Similar to saliva.4. Little pain and discomfort.5. Little inflammation.


Fat soluble; e.g.: Lipiodol, Pantopaque,

They are:1. Highly viscous, need more pressure to injection (painful).2. Give high radio-opacity.3. Take a long period to eliminate from the gland, so it

gives an enough time to take the radiograph, and in the same time cause inflammation and discomfort.

4. Unstable; it easily to oxidized in the presence of air.

Suspension contrast media; e.g. Hytrast. It has a good radio-opacity and high viscosity.


Procedures of Sialography:

1. Primary plain film evaluation. Post. ant., Occlusal, and lateral oblique.

2. Injection or filling phase, and radiograph for Sialography.

3. Evacuation phase: stimulated more by using lemon juice.


Sialography of submandibular gland


Sialography of parotid gland


Stone within the Wharton’s duct of submandibular gland


Stone in Wharton’s duct.Stone in Wharton’s duct.



Ultrasonography

1. This technique used sound as sonar to image structures deep within the soft tissues. The sound used for diagnosis lie above the audible range and is referred to as ultrasound.

2. As sound passes through any material, it meets a certain level of resistance.

3. Hence, Ultrasonography could be defined as the imaging of deep structures by measuring the reflection or transmission of the ultra-sonic waves.


Mechanism of action:

1. A transducer first produces Sound waves. Transducer constructed of a piezoelectric materials, such as lead zirconate titanate, which converts electrical signals into sound waves, which are transmitted into the tissues as a series of pulses.

2. The transducer also receives sound waves, which are reflected from back from the tissues, and converts them into electrical signals for processing into an image.


3. As sound travels through the tissues it loses energy by absorption, but a small proportion of the sound is reflected back from the boundaries of tissues. The reflected waves are received by the transducer and displayed on a monitor and recorded.

4. Air and bone do not readily transmit ultrasound wanes hence limiting the usefulness of ultrasound imaging in the maxillofacial region. It is, however, of value in the examination of space occupying lesions in the soft tissues, including for examination of the paroted gland, cervical lymph nodes, and oral soft tissues as lips and tongue.


Ultrasound echoes


Magnetic Resonance Imaging.(MRI)

Magnetic resonance imaging is a technique, which uses a combination of magnetic fields and radio-frequency waves to generate images of the body.


Able to image soft tissue without contrast agents

Magnetic Resonance

1. Magnetic field aligns atoms (Hydrogen)2. Radiowaves alter alignment3. Atoms realign, releasing energy4. Computer produces image

NO IONIZING RADIATION


Instead of detecting tissues by the x-ray, magnetic resonance detects the presence of hydrogen nuclei through their resonance in a magnetic filed.

Human tissues consist of molecules containing hydrogen nuclei (protons). Each proton has an axial spin and, because of its charge, behaves as a small magnet, have both north and south poles.

Normally the protons are randomly arranged; however, when the patient is placed in a strong magnetic field, the direction of the spine of the protons aligns with that of the filed.


The application of a pulsed resonant radio-frequency waves, causes the protons to tilt away from the magnetic filed. Once radio-frequency waves are turned off, the protons return to their preferred alignment with the magnetic filed, and gives off the acquired radio wave signals.

Magnetic Resonance Imaging is the process of locating these individual protons radio-signals in a three dimensional visual image.



To produce a MR image. The patient is placed inside a large magnet, which induce a relatively strong static magnetic field. This cause the nuclei of many atoms in the body, including hydrogen to align them with the magnetic filed.

Magnetic resonance imaging specifically image the presence of H2 nuclei, water, lipids and the degree of H2 are bound with molecules. So the tightly bound hydrogen atoms as in bone appears black as that of cortical plate, and loosely bound or mobile H2 atoms such that of salivary glands and liquids appears gray.



Magnetic Resonance

radiofrequency coils

Magnet(0.5 – 2.0 tesla = 5,000 – 20,000 gauss)

sliding table





Advantages: Excellent soft tissues imaging especially T.M.J and

salivary glands without radiation exposure or contrast media injection.

Disadvantages: 1. Long scan time.2. Some patients can not stay motionless for long

times.3. Noisy MR scanner4. Any vascular clips can move due to magnetic filed.5. High coast.


Radio Nuclide Imaging or Scintiscaning

It involves the injection of radioactive compounds with special affinity for particular tissues and later detection of them by means of external detectors and imaging systems.

It reflects the early biochemical changes occurred in bone metabolism that may precede architectural changes. So this technique has the potential to detect the earliest stages of bone loss.


The radioactive compounds called radio pharmaceuticals (isotopes). After injection them intravenously they uptake by the target tissues and concentrate in them. Then they located in this target tissues by means of a special detector such as gamma camera.

For examination of bone metabolism; used a bone seeking radiopharmaceutical such as Diphosphonate compound 99M Tc.


Gamma camera


Scintiscaning


Arthrography

It is technique for radiographic examination of a joint following the introduction of a contrast medium into the joint spaces to observe indirectly the non-mineralized components of T.M.J.

It is indicated to exam the damage of intra-articular soft tissues of T.M.J., displacement of the discs, and synovial perforations or adhesions.




Electronic Thermography

Thermography; It is methods of temperature pattern resduation and analysis.Its use in diagnosis based on fact that; the disease processes and/or abnormal conditions may result in different temperature patterns because of alterations in blood supply or the presence of inflammation.Sensors used to record temperature may be, small electronic probe called thermisters.It used to determining T.M.J. changes or pocket temperature.


Endoscopy

It is a technique used for examination of the maxillary sinus; by introducing an endoscope into the sinus to allow visualization of its interior and the mucous membrane linings; as it gives information, which are not shown by any other method.


Examination of salivary glands

1. Plain radiography:1. Intra-oral Occlusal films.2. Extra-oral: lateral oblique, Post. ant.;

2. Sialography.3. Ultrasonography.4. C.T.5. MRI.


Examination of maxillary sinus

1. Plain radiography1. Intra-oral films: periapical and Occlusal.2. Extra-oral films: Water’s and true lateral

2. Tomography.3. Endoscopy.


Imaging of the Temporomandibular joint.

The TMJ is technically one of the most The TMJ is technically one of the most difficult areas of the body to visualize well difficult areas of the body to visualize well because of multiple adjacent osseous because of multiple adjacent osseous structures. The common imaging modalities structures. The common imaging modalities performed to exam the TMJ are:performed to exam the TMJ are:


Tomography.Tomography.Arthrography.Arthrography.Transcranial views.Transcranial views.Transorbital views.Transorbital views.Skull views: Waters, Submentovertex and Skull views: Waters, Submentovertex and Reverse-Towne projections.Reverse-Towne projections.Panoramic views.Panoramic views.Magnetic resonance imaging.Magnetic resonance imaging.Computed Tomography.Computed Tomography.


Anatomy of TMJLateral view



Transcranial viewsTranscranial views

It provides a reasonably true projection It provides a reasonably true projection through the long axis of the joint.through the long axis of the joint.

Cassette position:Cassette position: Against the facial skin Against the facial skin surface on the side of interest, parallel to surface on the side of interest, parallel to the sagittal plane.the sagittal plane.


Central x-ray:Central x-ray: the tube on the contra lateral side the tube on the contra lateral side of the skull and the central beam directed of the skull and the central beam directed

downward 25 degrees, downward 25 degrees, anteriorly 20 degrees and anteriorly 20 degrees and is centered on the TMJ.is centered on the TMJ.


The central ray is oriented anteriorly 20 degree s centered on the TMJ of interest.

The central beam downward 25 degrees, The central beam downward 25 degrees, anteriorly 20 degrees and is centered on the anteriorly 20 degrees and is centered on the

TMJ.TMJ.


The central beam is projected across the The central beam is projected across the cranium above the petrous ridge of the cranium above the petrous ridge of the temporal bone on the film side and exits temporal bone on the film side and exits through the long axis of the condyle. through the long axis of the condyle.



The routine Transcranial radiographic series The routine Transcranial radiographic series includes projections of both left and right joints in includes projections of both left and right joints in

the closed and wide-open jaw positions.the closed and wide-open jaw positions.



The observer must remember that the The observer must remember that the Transcranial view displays only the lateral Transcranial view displays only the lateral aspects of the condylar head and the aspects of the condylar head and the articular fossa in profile.articular fossa in profile.

Thus, Transcranial radiography may show Thus, Transcranial radiography may show minute, subtle bony irregularities on the minute, subtle bony irregularities on the lateral bony surfaces but is far less lateral bony surfaces but is far less instructive of similar changes that occur in instructive of similar changes that occur in the central and medial joint areas.the central and medial joint areas.


Transorbital viewsTransorbital views Zimmer projectionZimmer projection

It is the conventional frontal TMJ projection It is the conventional frontal TMJ projection that is most routinely successful in delineating that is most routinely successful in delineating the joint with minimal superimpositions.the joint with minimal superimpositions.The advantages of this projection are The advantages of this projection are

1-1- The lack of major superimpositions over most The lack of major superimpositions over most of condylar processof condylar process

2-2- Production of true frontal projection of the Production of true frontal projection of the condyle, through directing the central ray condyle, through directing the central ray perpendicular to the long axis of the condyleperpendicular to the long axis of the condyle

3-3- Simple tech. Simple tech.


Head positionHead position: patient seat upright and tip the head : patient seat upright and tip the head downward about 10 degrees so the canthomeatal line is downward about 10 degrees so the canthomeatal line is horizontal. horizontal.

turn head 20° to the side of interest. turn head 20° to the side of interest.

Cassette positionCassette position: behind the patient‘s head so that the : behind the patient‘s head so that the central ray is projected to its center and perpendicular on central ray is projected to its center and perpendicular on it.it.

The central raysThe central rays:directed through the ipsilateral orbit and :directed through the ipsilateral orbit and through the TMJ of interest, exiting from the skull behind through the TMJ of interest, exiting from the skull behind the mastoid process. the mastoid process.

x-ray tube directed +35° , from the front through the floor x-ray tube directed +35° , from the front through the floor of the left orbit and left TMJof the left orbit and left TMJ

Ask patient to open the mouth as wide as possible Ask patient to open the mouth as wide as possible


Digital imaging.It is a conversion of dental radiograph into digital data in forms of numbers; small points or subdivisions called pixels or picture elements.

This pixels are posed in rows and columns called matrix and each pixel is assigned a gray scale value i.e. a digital value corresponding to the point on the x-ray.

The quality of any digitized radiograph depends on the number of pixels and the number of gray levels, which make up the image.


In conventional intra-oral radiograph film In conventional intra-oral radiograph film consists of silver halide grains in a gelatine matrix. consists of silver halide grains in a gelatine matrix. When this film is exposed to X-ray photons the When this film is exposed to X-ray photons the silver halide crystals are sensitized and are silver halide crystals are sensitized and are reduced to black during the developing process. reduced to black during the developing process. The film acts as both the radiation detector and The film acts as both the radiation detector and the image display.the image display.

With extra-oral films indirect action receptors With extra-oral films indirect action receptors are used to help record the image. This types of are used to help record the image. This types of film is sensitive to light photons which are emitted film is sensitive to light photons which are emitted by adjacent intensifying screens. Although the film by adjacent intensifying screens. Although the film is constructed of silver halide crystals these are is constructed of silver halide crystals these are primarily sensitive to light rather than X-rays.primarily sensitive to light rather than X-rays.

Digital imaging.


In digital radiography, instead of the silver halide grain In digital radiography, instead of the silver halide grain the image is constructed using pixels or small light the image is constructed using pixels or small light sensitive elements. These pixels can be a range of shades sensitive elements. These pixels can be a range of shades of grey depending on the exposure, and are arranged in of grey depending on the exposure, and are arranged in grids and rows on the sensor, unlike the random grids and rows on the sensor, unlike the random distribution of the crystals in standard film.distribution of the crystals in standard film.

However, unlike film the sensors are only the radiation However, unlike film the sensors are only the radiation detector and the image is displayed on a monitor.detector and the image is displayed on a monitor.

The signal that is produced by the sensor is an The signal that is produced by the sensor is an analogue signal, i.e. a voltage that varies as a analogue signal, i.e. a voltage that varies as a function of time. The sensor is connected to the function of time. The sensor is connected to the computer and the signal is sampled at regular computer and the signal is sampled at regular intervals. The output of each pixel is quantified intervals. The output of each pixel is quantified and converted to numbers by a frame grabber and converted to numbers by a frame grabber within the computer. The range of numbers is within the computer. The range of numbers is normally from 0 to 256 with 0 representing black, normally from 0 to 256 with 0 representing black, 256 representing white and all others are shades 256 representing white and all others are shades of grey. of grey.


Digital radiography may be: Direct Digital Radiography: (DDR) It is a film less radiographic imaging system which

involves the electronic generation of high-resolution computer monitor images or thermal print image from an intra-oral sensor.

Indirect Digital Radiography: (IDR) On which dental film will used to give the

information through scanner to the digital computer system. (Digora system), (Computer assisted densitometric image analysis system, CADIA), Subtraction radiography).



Full mouth series. Red rectangle highlights selected film


Magnified image


Adjust brightness, contrast

contrast

brightness


“Flashlight” feature


Measuring curved root


Combining intraoral/radiograhic


Colorization

05/03/2305/03/23 Ossama El-ShallOssama El-ShallDigital extra-oral images


Digital Subtraction Radiography

+


Application of digital subtraction radiography for detection and quantification of periodontal bone healing in a clinical research setting;

(a), base-line image. (b), 1-year follow-up image. (c), subtraction image showing bone gain (arrow).


(a) Original base-line image taken immediately post-surgery,

(b) Follow-up image taken after placement of final restoration,

(c) Subtraction image showing bone loss at alveolar crest and bone gain at the bone-implant interface.


Thank you all for listening

Dr. Ossama El-Shall

Professor of Oral Medicine & Periodontology, Faculty of Dental

Medicine, Al-Azhar University, Cairo, Egypt.

E-mail address: [email protected]



•Digital radiographs are one of the newest X-ray techniques around. Because it is so new and because the machines can be so expensive, your dentist may not have it yet; but watch for this process to become standard in the future. With digital radiographs, film is replaced with a flat electronic pad or sensor. The X-rays hit the pad the same way they hit the film. But instead of developing the film in a dark room, the image is electronically sent directly to a computer where the image appears on the screen. The image can then be stored on the computer or printed out. One of the great advantages of this process is that radiographs can be digitally compared to previous radiographs in a process called subtraction radiography. The computer can digitally compare the two images, subtract out everything that is the same and give a clear image of anything that is different. This means that tiny changes that may not be noticeable with the naked eye can be caught earlier and more clearly with digital-subtraction radiography. Subtraction radiography requires a specialized projection technique and additional software.


Arrange the bitewings to form a smile with the external oblique ridge at the extreme right and left with premolars toward the midline and molars away from the midline.


Arrange the horizontal posterior periapicals around the bitewings, matching the restorations and missing teeth. Look for maxillary posterior structures like the zygomatic process and maxillary sinus and mandibular structures like the external oblique ridge and mental foramen.


Arrange the horizontal posterior periapicals around the bitewings, matching the restorations and missing teeth. Look for maxillary posterior structures like the zygomatic process and maxillary sinus and mandibular structures like the external oblique ridge and mental foramen.


Science

2 extra-oral radiography[1]