3: Basic Principles

Question 1

Mask, collimators, diaphragms and lead backing are used for what in radiography?

Answer 1

Reducing scatter

Question 2

Close contact between the film and metal intensity by screens is essential to obtain what?

Answer 2

Sharp images

Question 3

A thin sheet of lead or lead sandwiched between sheets of tin is placed between the film and object being radiographer. What kind of effect does this provide?

Answer 3

Intensifying

Question 4

What is one of the main advantages of gamma rays over X-rays for radiography?

Answer 4

No electric supply needed

Question 5

What is depleted uranium used in industrial radiography for?

Answer 5

Shielding in isotope cameras

Question 6

The quality of radiation refers to what?

Answer 6

Penetrating ability of x or gamma rays

Question 7

When using a 400 kV X-ray machine, what range of steel thickness could you radiograph with?

Answer 7

19-76 mm

Question 8

With 1000 keV, what range of steel thickness could you inspect?

Answer 8

25-127 mm

Question 9

What keV or less may scatter in air path?

Answer 9

15 keV or less

Question 10

When inspecting a thin foil up to 3 mm of steel, what range of keV should you be using?

Answer 10

5-50 keV

Question 11

With 50-150 keV, what thickness of steel can you inspect?

Answer 11

3-19 mm

Question 12

With 100-200 keV, what range of steel could you inspect?

Answer 12

6-50 mm

Question 13

With 2000-6000 keV, what thickness of steel can you inspect?

Answer 13

50-203 mm

Question 14

When you have steel that’s between 75-457 mm, what voltage should you be using?

Answer 14

15-24 MeV

Question 15

Blurring of an image due to subject moved is called what?

Answer 15

Motion unsharpness

Question 16

If a radiograph is produced with too short a SFD and yet processed to give good density, what imperfection is it likely to have?

Answer 16

Lack of sharpness

Question 17

Collimators should be selected by…

Answer 17

Their size, shape and ability to limit beam to only the area being radiographed

Question 18

The elimination of unwanted portions of the d or gamma ray beam at its source by use of shielding is called what?

Answer 18

Collimation

Question 19

What is the purpose of masking a specimen with lead is to what?

Answer 19

Reduce undercut caused by scattered radiation

Question 20

An exposure device housing a radio isotope for industrial radiography can be called a what?

Answer 20

Camera

Question 21

What is computed radiography?

Answer 21

A flexible phosphorus imaging plate - that absorbs radiation energy which is stored and won’t be released until stimulated - used with a laser scanning device.

Question 22

How does computed radiography work?

Answer 22

The laser scan stimulates the phosphorus which causes the stored charges to emit blue light which is collected by a photomultiplier tube, converted to electrical signals that are digitized

Question 23

What is the process called in computed radiography?

Answer 23

Photo-stimulated luminescence

Question 24

How do digital detectors work?

Answer 24

Radiation energy is captured by an absorbing material (such as caesium iodide), which coverts radiation into visible light, then absorbed by a low-noise photodiode array which converts light into an electric charge.

Question 25

What are digital detectors?

Answer 25

Electronic decides that convert radiation (x and gamma) into different analog signals that are digitized and transferred to a computer as a digital radiographic image.

Question 26

What is undercut or internal scatter?

Answer 26

Secondary radiation produced by the object under test.

Question 27

Where does the greatest amount of scatter come from?

Answer 27

The specimen under inspection

Question 28

What is back scatter?

Answer 28

Secondary radiation that is produced by materials that are behind the specimen

Question 29

What is side scatter?

Answer 29

Usually produced from primary radiation this is scattered by walls or object located beside or around the object