intraoral imaging technique

Question 1

GEOMETRIC CHARACTERISTICS

Answer 1

1. Image sharpness
2. Image magnification
3. Image shape distortion

Question 2

Unsharpness

Answer 2

Fuzzy, unsharp margin of
radiographic image.
Due to Penumbra or edge gradient from photons interacting at the objects edge

Question 3

3 Rules to Maximize Sharpness

Answer 3

Rule #1.
Radiation source should be as small as possible.
Rule #2.
Source-to-object distance should be as long as possible.
Rule #3.
Object-to-receptor distance should be as short as possible.

Question 4

how does a small radiation source produce sharper images, can we control this?

Answer 4

fewer photons at the edge of the object= smaller pneumbra
Out of our control, up to manufacturer

Question 5

increased source to object distance effect, can we control this?

Answer 5

results in more parallel photons at the edge of the object, would be more divergent if distance shorter causing a larger pneumbra
can be controlled with cone length

Question 6

object to receptor distance, can we control?

Answer 6

want it to be short to decrease divergence of photons from object edge to receptor= decreased pneumbra
controlled with receptor placement

Question 7

MAGNIFICATION (Equal Enlargement)

Answer 7

Enlargement of radiographic image, compared to actual size of object. Image shows true shape of object

Question 8

2 Rules to Minimize Magnification

Answer 8

Rule #1.
Source-to-object distance should be as long as possible.
Rule #2
Source-to-receptor distance should be as short as possible.

Question 9

long source to object distance for magnification

Answer 9

reduces divergence of photons

Question 10

short object to receptor distance for magnification

Answer 10

reduces photon divergence from object to receptor

Question 11

5 RULES FOR ACCURATE IMAGE FORMATION

Answer 11

1. Focal spot as small as possible.
2. Source-object distance as long as possible.
3. Object-receptor distance as short as possible.
4. Object parallel to receptor.
5. Beam perpendicular to object and receptor.

Question 12

PROJECTION TECHNIQUES FOR PERIAPICAL RADIOGRAPHY

Answer 12

PROJECTION TECHNIQUES FOR PERIAPICAL RADIOGRAPHY
1. Paralleling Technique – use long cone
2. Bisecting Angle Technique – use long or short cone

Question 13

2 Rules to Minimize Distortion

Answer 13

Rule #1:
Object and receptor should be parallel.
Rule #2:
Beam should be perpendicular to object and receptor.

Question 14

PARALLELING TECHNIQUE

Answer 14

PARALLELING TECHNIQUE
1. Receptor parallel to tooth: must also get apices
increased object-receptor distance can be offset with increased source-receptor distance (long cone)
2. Beam perpendicular to tooth/receptor.

Question 15

alignment of beam and receptor, if not done?

Answer 15

if not done will result in a cone cut

Question 16

what is the preffered imaging method? if it cannot be done what is used?

Answer 16

 Paralleling technique is the preferred method.
 If the paralleling technique cannot be used, the bisecting angle technique may be used.

Question 17

BISECTING ANGLE TECHNIQUE Based on

Answer 17

Based on Rule of Isometry:
If two triangles have two equal angles and a
common side, then the two triangles are equal.

Question 18

BISECTING ANGLE TECHNIQUE

Answer 18

The angle formed by plane of tooth and plane of receptor is bisected, and the beam is directed perpendicular to the bisecting line.

Question 19

PROJECTION ERRORS IN PERIAPICAL RADIOGRAPHY

Answer 19

Vertical Angulation
Horizontal Angulation
Alignment of Beam and Receptor

Question 20

FORESHORTENING due to?

Answer 20

Tooth not parallel to receptor, and beam directed perpendicular to receptor.
results in tooth appearing shorter than is actually is

Question 21

ELONGATION due to?
.

Answer 21

Tooth not parallel to receptor, and beam directed perpendicular to tooth.
results in tooth appearing longer than it actually is

Question 22

Improper horizontal
angulation results in?

Answer 22

overlapping of contacts.

Question 23

Improper alignment of
beam and receptor results
in?

Answer 23

Improper alignment of
beam and receptor results
in cone cutting.

Question 24

what do we want to see with BWs

Answer 24

Crowns, open interproximal areas and alveolar bone support, Caries, periodontal condition, calculus, crown margins

Question 25

BW angulation

Answer 25

slight + angulation of the source due to curve of wilson

Question 26

BW HA errors? when to retake

Answer 26

results in overlapped contacts retake it half the enamel thickness is overlapped

Question 27

methods of localization

Answer 27

1. Right angle method
2. Tube shift method (SLOB)
   Buccal object rule

Question 28

Right Angle
Method of localization

Answer 28

two radiographs are taken with the receptors perpindicular to one another
ex: PA and occlusal

Question 29

Tube Shift Method

Answer 29

take a normal PA then shift the tube in a M or D direction for another PA
if the object moves with the tube: lingual
if object moves in opposite: buccal