Projection Geometry

Question 1

What 3 problems arise in 2D images of 3D objects?

Answer 1

1. Unsharpness
2. Magnification
3. Distortion

Question 2

What is spatial resolution?

Answer 2

Degree of how well an image can display two objects that are close together.

Question 3

What is sharpness?

Answer 3

Degree of how well image can display boundary between two differing radiodensities.

Question 4

What is penubra?

Answer 4

Space of partial illumination between perfect shadow and full light. Basically is a blurry edge.

Question 5

How to reduce penumbra?

Answer 5

1. Small focal spot
2. Increase distance between focal spot and object.
3. Lower distance between object and image receptor.

Question 6

What is parallax? Only relevant in?

Answer 6

Apparent change in position or size of subject when viewed from different perspectives. Only happens in film.

Question 7

What is image size distortion? How do we prevent this?

Answer 7

equal magnification (+ or -) of the object. Increase source to object distance.

Question 8

What is image shape distortion? How do we prevent this?

Answer 8

Unequal magnification in different parts of same object. Decrease object to receptor distance.

Question 9

Receptor should be what do the long axis of the tooth?

Answer 9

Parallel.

Question 10

What is the slob rule for imaging location?

Answer 10

Same Lingual, Opposite buccal.