4: RT Imaging

Question 1

What is the phenomena in which grains of silver clump together?

Answer 1

Graininess

Question 2

The emulsion or image layer of the unexposed film contains grains of what?

Answer 2

Silver bromide

Question 3

A graph showing the relationship between the material thickness, kilo voltage and time is called what?

Answer 3

An exposure chart

Question 4

Film selection for an X-ray exposure depends on what? (3)

Answer 4

1. Thickness of part
2. Material of specimen
3. Voltage range of X-ray machine

Question 5

A high speed film is one which…

Answer 5

Needs low exposure for a given density

Question 6

The sharpness of a radiographic image’s outline (the abruptness of density transition) is termed radiographic what?

Answer 6

Definition

Question 7

Radiographic contrast is the…

Answer 7

Sum if the film and subject contrast

Question 8

In general grain size in a slow speed film is _________ a fast film.

Answer 8

Smaller than

Question 9

When comparing the speeds of 2 films using their characteristic curves (density vs log relative exposure) the faster film curve will lie _______ the slower film.

Answer 9

Left of

Question 10

The slope of a characteristic curve for an industrial X-ray film indicates what?

Answer 10

Contrast

Question 11

The metallic silver formed when an X-ray film is exposed but not developed is called what?

Answer 11

The latent image

Question 12

In radiographic film, imaging the suspension of silver halide crystals in a gelatinous binding agent is called a what?

Answer 12

Emulsion

Question 13

What is inherent unsharpness a direct result of?

Answer 13

Secondary electrons generated in film emulsion making silver halide grains viewable

Question 14

How are grains, speed and sharpness related?

Answer 14

Larger grains = faster speed = more unsharpness

Question 15

The higher the film…

Answer 15

The larger the grains and the less exposure time is required

Question 16

What is the most common and uncommon film types?

Answer 16

Class l is most common until thicker components, fine grains

Class lll most uncommon, mostly concrete shots (material 3+” thick), coarse grains

Question 17

A characteristic curve determines what?

Answer 17

FILM CONTRAST

Question 18

What is latitude?

Answer 18

Ability of film to cover range of thicknesses for a given exposure (dependant on films contrast level and relative speed)

Question 19

What does a characteristic curve show?

Answer 19

How film responds to different amounts of exposure

Question 20

Exposure charts are plotted against what?

Answer 20

Thickness

Question 21

What are 2 ways to prepare an exposure chart?

Answer 21

1. With a densitometer (how we did in class)

2. With a characteristic curve

Question 22

For density of 2, how much light is being transmitted through?

Answer 22

One

Question 23

What is subject contrast?

Answer 23

Ratio of intensities passing through 2 material thicknesses

Question 24

What are 3 characteristics of a good film base?

Answer 24

1. Water/chemical resistant
2. Non-combustible
3. Dimensionally designed for easy drying

Question 25

What happens to the crystals/grains of a film when exposed?

Answer 25

Exposure to radiation causes a change in physical structure

Question 26

Once development starts, a reaction occurs causing exposed silver grains to convert to what?

Answer 26

Black metallic silver

Question 27

What are single coated films often used for?

Answer 27

Critical inspections where super fine detail is required

Question 28

What is the substrate/subbing layer and what is its purpose?

Answer 28

Layer between actual film base and the emulsion. Sole purpose to hold emulsion to film base.

Question 29

What is the super coat/outside layer for?

Answer 29

Scratch and pressure resistance gelatin protection to emulsion

Question 30

Why would blue dye be added to film base?

Answer 30

To improve viewing of undeveloped images

Question 31

The higher the film class..

Answer 31

Somewhat lesser the image quality

Question 32

In general, the faster the speed = lower the ________ = _________ of latitude

Answer 32

Faster the speed = lower the contrast = wider range of latitude

Question 33

What are 2 other names for a characteristic curve?

Answer 33

1. H & D Curve | 2. Sensitometric Curve

Question 34

What is plotted against what in a characteristic curve?

Answer 34

Densities plotted against logarithms of relative exposures

Question 35

Exposure charts show the relationship between what?

Answer 35

Material thickness, energy (kV) and exposure (mAm)

Question 36

What is the difference between a gamma and an X-ray exposure chart?

Answer 36

For gamma there’s no variable factor that corresponds to kilo voltage.