Image Characteristic & Interpretation
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DENTAL X-RAY IMAGE CHARACTERISTICS
Dr. Walid Samir SalemBDS, MS, MHPE
lecturer, Oral Surgery Department
Member, Dental education unitCollege of Dentistry, Qassim
University
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Dental X-ray image characteristic include both visual & geomatric characteristics.
Visual characteristic:•Density.•Contrast.
Geometric characteristics:•Sharpness.•Magnification.•Distortion.
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Dark Gray to Black
RADIOLUCENT
A structure that lack density appear radiolucent e.g. soft tissue & spaces
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White to Light Gray
RADIOPAQUE
Radiobaque structures are dense & absorb X-ray, e.g. enamel, dentine, & bone.
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I) Density Represents the degree of darkening of an exposed x-ray film (white to black)
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The overall density of the film affects the diagnostic value of the film (ideal density, too light, too dark)
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1.Exposure factors:•mA• kV• Exposure time
2. Object thickness3. Object density4. Film fog
Density influenced by:
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Exposure factors (mA, kVp, exposure time). An unnecessary increase in any of these factors results in an increase in film density.
Object thickness: the larger the patient’s head, the more x-rays that are needed to produce an ideal film density Object density: determined by type of material (metal, tooth structure, composite, etc.) and by amount of material
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Film Fog
fog
Increased film density from causes other than exposure to the primary x-ray beam (scatter, improper safelighting, improper film storage, expired film)
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The difference in densities (blackness) between various regions on a radiograph
II) Contrast
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High Contrast
Short Scale
Black and White(Few shades of gray)
Best for caries detection
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Low Contrast
Long Scale
Many shades of gray
Best for periapical or periodontal evaluation
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Contrast influenced by:
1.Subject contrast
2. kVp
3. Film contrast
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Subject contrastResults from varying object densities within patient, this is determined by: thickness, density & composition of the subject
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kVp
Affects energy (penetrating ability) of x-rays.
40 50 60 70 80 90 100
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Film contrast:
It refers to the characteristics of the film that influence the radiographic contrast, it is incorporated into film by manufacturer.
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Film Fog
fog
Film fog makes the whole film darker, making it harder to see the density differences (contrast)
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I) Sharpness
Measures how well the details (boundaries/edges) of an object are reproduced on a radiograph.The fuzzy unclear area that surround the image is termed penumbra.
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Penumbra
(pene=almost + umbra= shadow)
Def.: Zone of unsharpness
along the edge of images in a
radiograph
The larger the penumbra, the
less sharp the image will be
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Penumbra Umbra(complete shadow)
Target (focal spot)
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Sharpness influenced by:
1. Focal spot size
2. Source–object (teeth) distance3. Object (teeth)-film distance4. Intensifying screens5. Film crystal size6. Motion
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Decrease focal spot size, increase sharpness
Target
Object
Umbra
Penumbra
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Increase source-object distance, increase sharpness
Target
Umbra Penumbra
Teeth
film
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Decrease object-film distance, increase sharpness
Target
Umbra Penumbra
Teeth
film
film
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Intensifying screens decrease sharpness
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The faster film contain larger crystal size that produce less image sharpness, and vice versa.Unsharpness occur because the large crystals don’t produce object outline as well as smaller.
Film crystal size
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Patient motion decreases sharpness
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II)Magnification
Increase in size
Magnification affected by: Source-object distance Object-film distance
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Target 16” Target
8”
Target 16”
Magnification Increase source-object distance, decrease magnification
Decrease object-film distance, decrease magnification
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III) DistortionChange in the true shape or size of the object
Distortion affected by:
1. Film-teeth relationship
2. Beam alignment
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Paralleling
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Bisecting angle
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Ideal Radiograph
1.Image same size as object
2.Image same shape as
object
3.Image has good detail
4.Image has good density
and contrast
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Mandibular molar periapical film comes closest to satisfying properties of an ideal radiograph(either paralleling or bisecting)
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RADIOGRAPHIC INTERPRETATION BASIC
Dr. Walid Samir SalemBDS, MS, MHPE
lecturer, Oral Surgery DepartmentMember, Dental education unit
College of Dentistry, Qassim University
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Objectives:
•The importance of radiographic interpretation.•The difference between interpretation & diagnosis.•Rules of radiographic interpretation.•Image analysis.•Steps of interpretation.
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The importance of interpretation:
Radiographic interpretation is an essential part of the diagnostic process. The ability to evaluate & recognize what is revealed by a radiograph enable us to detect diseases, lesions & conditions which can’t be identified clinically.
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Interpretation Vs. Diagnosis:Interpretation refers to an explanation of what is viewed on a radiograph while diagnosis refers to the identification of disease by examination or analysis.In other words the interpretation is a step in the diagnosis.
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Rules of radiographic interpretation
1. The area to be examined must be completely shown at optimal angulations
2. All the boundaries of the area of interest must be shown with normal structures around it.
3. Knowing and familiarity with all normal anatomical landmarks as well as all various pathological conditions that may affect the area of interest.
4. Optimum viewing condition.
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Viewing condition:
Ideally, should include the following:Ambient light in the room should be
reduced.Intraoral radiographs should be
mounted.Light from the view-box should be of
equal intensity across the viewing surface.
The size of the view-box should accommodate the size of the film.
A magnifying lens allows detailed examination of small regions of the film.
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Image Analysis:
The first step in image analysis is to use a systemic approach to identify all the normal anatomy present in an image.Avoid limiting your attention to one particular region of the film.
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Steps of interpretation
Localization. Observation. General consideration. Interpretation. Correlation.
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Localization
I. Localized or generalizedII. Position in the jawIII.Single or multipleIV. Size
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How to identify the position of the periapical film?
Embossed dot identify right from left and the anatomical land mark to identify the jaw and the area.
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Upper left
Lower left
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Upper right premolar
Lower anterior
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Observation
All shadows, other than the localized shadows of the normal landmarks must be observed.
For example: shadows in crowns, cervical area, roots, restorations, size of root canals, periodontal membrane space, periapical area, alveolar crest, foreign bodies, integrity of bone …………
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General consideration
A radiograph shows only 2 dimensions of a 3 dimensional object (width and height but not the depth)
Cervical burnout: usually appears as cervical RL and misinterpreted by caries; this occurs due to less density and more penetration of rays.
Pulp exposure never to be determined from radiograph but only the proximity to the pulp.
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Interpretation
Studying the features of teeth and bone:
Teeth
Study the whole tooth,(crown, root enamel, pulp….), number of teeth and finally supporting structures, (Periodontal membrane space, lamina dura, alveolar crest)
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Bone
Changes in bone may include:1- Changes in density.2- Changes in the margin3- Changes inside the lesion.4- Effect on surrounding tissues.5- Changes in structure
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Correlation The final step is to correlate all of
the radiographic features to reach a radiographic differential diagnosis.
Then to draw a final diagnosis, we have to correlate other data as case history, clinical examination, and other diagnostic aids with the radiographic differential diagnosis.
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