Toothbuds

Question 1

Sharpness is

Answer 1

How well the boundaries of a structure can be seen

Question 2

Resolution is

Answer 2

How well adjacent small objects can be differentiated

Question 3

Both sharpness and resolution is increased by:

Answer 3

• small focal spot
• Increase source-to-film distance
• Decrease tooth-to-film distance

Question 4

Contrast is defined as

Answer 4

Difference in densities between light and dark areas on film

Question 5

Contrast resolution is the ability to?

Answer 5

Ability to distinguish gray levels on an image

Question 6

What are bits on contrast resolution?

Answer 6

Term used to identify gray levels (computing). Number of shades of grey = 2 bits; e.g. 8 bits = 256 shades of grey

Question 7

Contrast resolution depends on which factors?

Answer 7

Tissue type, film/sensor, computer displace, etc

Question 8

Spatial resolution is the capacity to?

Answer 8

To distinguish fine detail on an image

Question 9

Spatial resolution is described in?

Answer 9

Line pairs per millimetres (lp per mm) or dots per inch (DPI)

Question 10

PSP films can resolve _____ per mm

Answer 10

8-24

Question 11

Spatial resolution depends on which factors?

Answer 11

Sensor/film, size of focal spot, distance between source, objective and image

Question 12

Angulation

Answer 12

Angle of central beam with respect to teeth or film

Question 13

Vertical angulation

Answer 13

Angle measured from occlusal plane to central beam

Question 14

Positive vertical angulation

Answer 14

X-ray cone point downwards; use for maxillary teeth

Question 15

Negative vertical angulation

Answer 15

X-ray cone pointing upwards; use for mandibular teeth

Question 16

What is bisecting angle technique

Answer 16

• Triangle made by long axis of tooth, film, and x-ray beam
• Bisector line divides triangle into two equal triangles
• X-ray beam must be perpendicular with bisector line
• If done correctly, no distortion of image

Question 17

Parallel angle technique

Answer 17

• Long axis of tooth and film are parallel

- X-ray beam is perpendicular

Question 18

Elongation as an error is when?

Answer 18

Too little vertical angulation

Question 19

Foreshortening as an error is when?

Answer 19

Too much vertical angulation

Question 20

Horizontal angulation is what?

Answer 20

The angle measured with respect to proximal surface of teeth and central beam

Question 21

Ideally, central beam should be?

Answer 21

Parallel to proximal surface of teeth

Question 22

If you take radiograph with beam at an angle to proximal surface of teeth, what do you get?

Answer 22

Overlap between teeth (see front of one tooth and the back of the adjacent tooth)

Question 23

Horizontal angulation is described using the _______ (e.g. tube head was placed too distal).

Answer 23

Relative tube-head position

Question 24

What is orientation

Answer 24

Orientation of a particular feature to central beam can affect radiographic appearance

Question 25

Magnification in radiography?

Answer 25

Increases in size of image on radiograph compared with actual size of tooth.

Question 26

What is distortion caused by?

Answer 26

Caused by tooth being too far film and close to source

Question 27

How to keep accurate size and shape of radiograph?

Answer 27

Make source as far from object as possible and object as close to plate

Question 28

Image Shape Distortion?

Answer 28

Unequal magnification of different parts of the same objects

Question 29

When not all parts of the tooth are the same distance, it forms?

Answer 29

Focal spot

Question 30

where is focal spot common in?

Answer 30

Common in maxillary molars due to splayed roots. This gives appearance of buccal roots seeming short; palatal roots seeming normal.

Question 31

How is image shape distortion minimized?

Answer 31

Parallel angle technique

Question 32

Blurring is caused by?

Answer 32

Caused by patient or x-ray tube movement during exposure

Question 33

Soft tissue shadow is caused by?

Answer 33

Teeth can be superimposed on soft tissue structures (e.g. alar of nose)

Question 34

What are characteristics of an ideal image?

Answer 34

• Proper visual characteristics (e.g. density, contrast, sharpness, etc)
• Minimal geometric characteristics (e.g. magnification, distortion, blurring, etc)
• Anatomically accurate
• Adequate coverage of region of interest

Question 35

5 rules for high quality radiograph

Answer 35

1. Focal spot as small as possible (on machine)
2. Tube-to-tooth distance as long as possible
3. Tooth-to-film distance as short as possible
4. Film parallel to the tooth
5. X-ray beam perpendicular to tooth and film (parallel technique)