Density 2

Question 1

What concept is occurring when a 10 MeV x-ray invades a nucleus?

Answer 1

Photodisintegration

Question 2

What happens to the energy during photo disintegration?

Answer 2

Is absorbed by the nucleus and nuclear fragments are emitted

Question 3

What type of conditions contribute to scatter radiation production?

Answer 3

1 high kVp
2 thick soft tissue (water density)
3 large field size

Question 4

What is the solution for a large field size that has the potential to produce a lot of scatter?

Answer 4

Collimation

Question 5

What are some scatter control methods?

Answer 5

1 optimum kVp
2 collimation to control field size
3 air-gap technique
4 scatter-absorbing grids
5 recumbent radiography

Question 6

What is probably the best way to take an x-ray of a larger patient to ultimately reduce overall scatter?

Answer 6

Take it recumbent

Question 7

What kind of filter is a grid?

Answer 7

Selective lead filter (between patient and film)

Question 8

Who invented the scatter-absorbing grid?

Answer 8

Gustave Bucky in 1913

Question 9

When is a grid needed?

Answer 9

When patient part measures greater than 10cm or when using techniques above 70 kVp

Question 10

How does the grid affect the appearance of the film?

Answer 10

Improves contrast

Question 11

What specific benefit does the grid NOT have?

Answer 11

Does NOT protect the patient

Question 12

What is the orientation of the lead lines found in a grid?

Answer 12

Linear***, crosshatched, or rhombic crosshatched pattern

Question 13

What separates the thin lead lines of the grid?

Answer 13

Thin strips of aluminum or carbon fiber

Question 14

What are the two types of a linear grid?

Answer 14

Parallel and focused

Question 15

Which type of grid design involves a grid cut-off and an underexposed appearance of the film?

Answer 15

Parallel

Question 16

What is the benefit of a focused grid?

Answer 16

Grid cut-off is eliminated

Question 17

What is the grid ratio?

Answer 17

Measure of the height of the lead strips divided by the distance between them (h/d)

Question 18

When there is an increased grid ratio, what measurement must be increased to compensate?

Answer 18

mAs

Question 19

How does a higher grid ratio affect contrast?

Answer 19

Higher contrast

Question 20

What is the recommended grid ratio?

Answer 20

12: 1 focused grid used with a single phase generator
10: 1 focused grid used with high frequency generator

Question 21

What is grid frequency?

Answer 21

Measure of the number of lead lines per inch or centimeter

Question 22

What is the downside to a higher grid frequency?

Answer 22

Patient dose increases

Question 23

What is the benefit to a higher grid frequency?

Answer 23

Less grid lines on film

Question 24

How does the removal of scatter by a grid affect film density?

Answer 24

Decreases it (lighter film)

Question 25

If the film appears too light when using a grid to remove scatter, what measurement must be changed to compensate?

Answer 25

Increase mAs (to increase density)

Question 26

How does an increase in grid ratio affect film density?

Answer 26

Decreases it (lighter film)

Question 27

What effect does decreased film size have on density and why?

Answer 27

Decreased density (because scatter is eliminated)

Question 28

If you take a 14 x 17 and change it to a 5x5 via collimation, how is the appearance of the film changed?

Answer 28

Lighter film (decreased density)

Question 29

What is spot filming?

Answer 29

Using smaller films and tight collimation to improve contrast

Question 30

What technique can be a substitute for a grid?

Answer 30

Air-gap technique

Question 31

How big of an air-gap is comparable to a 7:1 grid ratio in a scatter clean-up?

Answer 31

4”-6”

Question 32

Why is the air-gap technique not recommended?

Answer 32

Changes must be then be made to technique, tube placement, etc.

Question 33

The air gap produces what kind of contrast: short or long scale?

Answer 33

Short scale

Question 34

What is the maximum distance for an air-gap due to magnification?

Answer 34

10”

Question 35

How does laying a patient recumbent prevent scatter?

Answer 35

Decreases diameter of the patient (lower kVp and mAs needed)

Question 36

What is the purpose of compression bands?

Answer 36

Compression of tissues to reduce scatter and improve contrast

Question 37

What is the purpose of lead vinyl blockers?

Answer 37

Cover areas of film on film cassettes where multiple exposures are made on a single film