Digital And Film

Question 1

What size of receptors are used for periapicals, bitewings and occlusal radiographs?

Answer 1

Anterior periapical - size 0
Posterior periapical - size 2
Bitewings - size 2
Occlusal - size 4

Question 2

How is the x ray beam converted into an image?

Answer 2

When the x ray beam passes through an object, some of the photons are attenuated, creating an x ray shadow

Dark areas- no attenuation

Question 3

How many binary digits (greyscale depth) should a digital radiograph have?

Answer 3

At least 8 binary digits (256 shades of grey)

(White is 255)

Question 4

What environment should digital radiographs be viewed?

Answer 4

Subdued lighting with no glare
On clean monitor, high enough brightness, suitable contrast level.

Question 5

What is SMPTE test pattern?

Answer 5

Society of motion picture and television engineers

Tests resolution, contrast and brightness of monitor

Question 6

What are the 2 types of Intra oral digital receptors?

Answer 6

Solid state (connected to computed, image created instantly)

Phosphor plates (put in scanner after exposure to be read- phosphor crystals in receptor are excited by the x ray- latent image)

Question 7

What are the components of an Intra oral film packet?

Answer 7

Outer packaging - prevents ingress of saliva, indicates which side is the front

Lead foil - absorbs some excess x ray photos

Inner wrapper - black paper, protects from light exposure, damage by fingers, saliva

Radio graphic film - photons react with emulsion on film to produce latent image which becomes visible after chemical processing

Question 8

What makes up the emulsion on the radio graphic film?

Answer 8

Silver halide crystals embedded in gelatin border
- crystals become sensitised upon interaction with x ray (and visible light)
- during processing, sensitised crystals - dark area, non-sensitised crystals- light areas

Question 9

What is the relevance of film speed?

Answer 9

Relates to amount of x ray exposure required to produce adequate image

Increased speed = decreased radiation required

Large crystals = increased speed = poorer image quality

Question 10

What is an intensifying screen?

Answer 10

Extra oral radiographs

Reduces radiation dose but also reduces detail

Question 11

What are the steps of film processing?

Answer 11

Developing
Washing
Fixing
Washing
Drying

Question 12

In film, what causes a pale image?

Answer 12

Developing issue - film removed from solution too early, solution too cold/ dilute

Question 13

In film, what causes a yellow/ brown image?

Answer 13

Inadequate fixing (non-sensitised crystals are left behind)