OMFPR 4: Making a Radiographic Image

Detail

Contrast resolution

Magnification and distortion

Diagnostic radiograph parameters

Image quality

Reliability of image to represent true state of anatomic region

Small

X-rays should originate from a _____ focal spot.

Long

SOD should be as ____ as possible.

Short

ORD should be as ____ as possible.

Parallel

Long axis of object should be _________ to receptor/film.

Perpendicular

Central ray should be ____________ to receptor.

Small

Does small or large focal spot produce sharper images with higher spatial resolution?

SOD

___ should be as long as possible.

Intra-oral radiography: collimated extensions: 8 inches, 12 inches, or 16 inches

How is a long SOD clinically achieved?

ORD (object to receptor distance)

___ should be as short as possible.

Closest

Place anatomy of interest ______ to receptor.

Parallelism

___________ between object and receptor decreases distortion and improves image sharpness.

Perpendicular

The central ray of the x-ray beam should be __________ to the long axis of the tooth to reduce geometric distortion.

Foreshortening

Central ray is perpendicular to the image receptor but the object is not parallel with the image receptor

Elongation

Central ray is perpendicular to the object but not to the image receptor

Foreshortening

Foreshortening

Elongation

Paralleling technique

The central ray is directed at right angle to the central axes of object and receptor

Bisecting-angle technique

Central ray is directed at a right angle to the imaginary plane that bisects the angle formed by the image receptor and the central axis of the object

Paralleling

Preferred method for minimizing distortion

Sharpness

How well a boundary between two areas of differing radiodensity is revealed

Spatial resolution

Ability of an imaging system to differentiate between two nearby objects

Spatial resolution

How well a radiograph reveals small objects that are close together

Detail

Sharpness and resolution

Blurry vs. sharp

Density

Overall degree of darkening of a radiograph

Radiolucent

Radiolucent or radiopaque:

Air space, foramen, canal, suture, fossa, soft tissue

Radiopaque

Radiolucent or radiopaque:

Cortical bone, lamina dura, dentin, enamel, metal restorations

Cancellous bone

What structure falls between radiolucent and radiopaque?

mA

Exposure time

Filtration

Collimation

Distance

Factors affecting density

mA

Exposure time

Factors that increase density / darker image

Filtration

Collimation

Distance

Factors that decrease density / lighter image

Lighter

Artifacts (lead aprons, film reversal, earrings, thyroid collars) lead to _______ areas in the film.

Contrast

Difference in densities between the light and dark regions in a radiograph

Low vs. high contrast

Long scale (low contrast)

Long or short scale:

Small gradual change among different optical densities

High kVp

Short scale (high contrast)

Long or short scale:

Large or abrupt differences among optical densities

Low kVp

Good vs. poor contrast

Fog

Scatter radiation (Compton or coherent interactions) produces ___.

Use a 3D imaging modality

CBCT

How to gather 3D radiologic information?

Right angle technique

Tube shift technique (SLOB rule, BOR / Clark's rule)

Special studies

Radiographic techniques in localization

Right angle technique

Obtain 2 radiographs at 90 degrees to each other of the area of interest e.g. periapical and occlusal radiographs, lateral cephalometric and postero-anterior view of skull

Same

Lingual

Opposite

Buccal

For tube shift technique, what is the SLOB rule for localization?

Lingual

Object moves in same direction as x-ray tubehead. Is it lingual or buccal?

Buccal

Object moves in opposite direction as x-ray tubehead. Is it lingual or buccal?

Lingual

Is the impacted tooth buccal or lingual?

Buccal

Where is the impacted premolar located relative to the first molar?

Lingual

Evaluate the position of the impacted premolar.