Projection Geometry

Question 1

What are the 3 geometric factors that affect the quality of radiograph?

Answer 1

Image Sharpness
Image Magnification
Image shape distortion

Question 2

Fuzzy, unsharp margin of radiographic image.

Penumbra or edge gradient

Answer 2

Unsharpness

Question 3

____ is the area around the margin of the object being radiographed; amount of unsharpness

Answer 3

Penumbra

Question 4

Rule #1 to maximize sharpness of radiographic images:

Answer 4

Radiation source should be as small as possible.

Question 5

Rule #2 to maximize sharpness of radiographic images:

Answer 5

Source-to-object distance should be as long as possible.

Question 6

Rule #3 to maximize sharpness of radiographic images:

Answer 6

Object-to-receptor distance should be as short as possible.

Question 7

How do we increase source to object distance to increase sharpness?

Answer 7

Increase length of collimator

Question 8

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

Answer 8

MAGNIFICATION (Equal Enlargement)

Question 9

Rule #1 to minimize magnification of radiographic images:

Answer 9

Source-to-object distance should be as long as possible.

Question 10

Rule #2 to minimize magnification of radiographic images:

Answer 10

Object-to-receptor distance should be as short as possible.

Question 11

Variation from true shape of object.
Unequal magnification of parts of object.
Improper alignment of receptor, object, beam.

Answer 11

DISTORTION (Unequal Enlargement)

Question 12

Rule #1 to minimize distortion of radiographic images:

Answer 12

Object and receptor should be parallel.

Question 13

Rule #2 to minimize distortion of radiographic images:

Answer 13

Beam should be perpendicular to object and receptor.

Question 14

What are the 2 intraoral projection techniques for PA radiography?

Answer 14

Paralleling

Bisecting Angle

Question 15

\_\_\_\_\_\_ technique
1.Receptor parallel to tooth 
increased object-receptor distance 
increased source-receptor distance
2.   Beam perpendicular to tooth/receptor.

Answer 15

Paralleling technique

Question 16

In the paralleling technique, do you want to use a long or short cone?

Answer 16

Long cone

Question 17

Is the bisecting angle or paralleling technique the preferred method?

Answer 17

Paralleling

Question 18

_____ technique:
Based on Rule of Isometry:
If two triangles have two equal angles and a common side, then the two triangles are equal.
The angle formed by plane of tooth and plane of receptor is bisected, and the beam is directed perpendicular to the bisecting line.

Answer 18

Bisecting angle technique

Question 19

Tooth not parallel to receptor, and beam directed perpendicular to receptor.

Answer 19

FORESHORTENING

Question 20

Tooth not parallel to receptor, and beam directed perpendicular to tooth.

Answer 20

ELONGATION

Question 21

Improper _______ angulation results in overlapping of contacts.

Answer 21

horizontal angulation

Question 22

Improper alignment of beam and receptor results in ______.

Answer 22

cone cutting

Question 23

_______ technique:
Crowns, interproximal areas and alveolar bone support
Caries, periodontal condition, calculus, crown margins
Premolar and molar bitewing

Answer 23

BITEWING TECHNIQUE

Question 24

: periapical and bitewing radiographs showing all teeth

Answer 24

FULL MOUTH SERIES

Question 25

What are the 2 methods for radiographic localization?

Answer 25

Right angle method

Tube Shift method (SLOB)

Question 26

____ method of localization:

Radiographs taken at right angles of each other provides better localization

Answer 26

Right angle method

Question 27

According to the SLOB method, if the tubehead is moved to the mesial and the object also moves to the mesial on the radiograph, is it on the buccal or lingual?

Answer 27

Lingual

Question 28

According to the SLOB method, if the tubehead is moved to the mesial and the object moves to the distalbon the radiograph, is it on the buccal or lingual?

Answer 28

Buccal