Ch 18 Grids

Question 1

What does a grid do

Answer 1

Cleans up scatter/fog
Improves contrast in the image

Question 2

High KVP = what scale contrast

Answer 2

Low contrast, long scale

Question 3

Low kvp = what contrast

Answer 3

High contrast, short scale

Question 4

When do we use a grid

Answer 4

KVP is above 60
Body part is more than 10 cm

Question 5

What are the strips in a grid made of

Answer 5

Thin lead foil

Question 6

What is the interspace material in a grid made of

Answer 6

Aluminum

Question 7

What are oscillating grids

Answer 7

Grids that move back & forth to keep grid lines out of images - magnet pulls back

Question 8

Who invented the grid

Answer 8

Gustav Buckey

Question 9

Do grids also absorb useful photons

Answer 9

Yes

Question 10

The ratio of the height of the lead strips to the distance between the strips

Answer 10

Grid Ratio

Question 11

Grid ratio formula

Answer 11

Height divided by distance

Question 12

Higher ratio grids allow more or less scatter through

Answer 12

Less

Question 13

Disadvantages of high ratio grids

Answer 13

Require more accurate positioning
More prone to grid errors

Question 14

The higher the grid frequency the thinner or thicker the strips

Answer 14

Thinner

Question 15

Number of grid lines per inch or centimeter

Answer 15

Grid frequency

Question 16

Lead strips, running in only One Direction

Answer 16

Linear grids

Question 17

Lead lines run at right angles to one another

Answer 17

Criss cross or cross hatched grids

Question 18

Parallel grid

Answer 18

Lead and interspace material run parallel to one another

Question 19

Focused grids

Answer 19

Lead lines and interspace material are angled to match the divergence of the beam

Question 20

Which grids are best used with long SID

Answer 20

Parallel grids

Question 21

Distance between the grid and the convergence point

Answer 21

grid radius

Question 22

Reciprocating grid

Answer 22

Motor drives the grid back and forth

Question 23

What type of grids are used in portable

Answer 23

Stationary grids

Question 24

What can a mounted grid also be called

Answer 24

Potter Bucky Diaphragm

Question 25

GCF no grid

Answer 25

1 x Mas

Question 26

5:1 GCF

Answer 26

2 x Mas

Question 27

6:1 GCF

Answer 27

3 x MAs

Question 28

8:1 GCF

Answer 28

4 x MAs

Question 29

12:1 GCF

Answer 29

5 x MAs

Question 30

16:1 GCF

Answer 30

6 x MAs

Question 31

Formula for GCF

Answer 31

Mas1/Mas2 = GCF1/GCF2

Question 32

Focused grid is used upside down on the IR

Answer 32

Upside Down grid error

Question 33

What happens with an upside down grid error

Answer 33

Good exposure in the center but you lose detail in the peripheries

Question 34

Occurrs when the xray beam is angled across the lead strips

Answer 34

Off level grid error

Question 35

IR or tube is misaligned - image appears elongated - usually only occurs with stationary grids - only can occur with a parallel grid

Answer 35

Off level grid error

Question 36

Occurs when the CR of the xray beam is not aligned from side to side with the center of a focused grid

Answer 36

Off center grid error

Question 37

Lateral decentering - creates image similar in appearance to off level grid error

Answer 37

Off center grid error

Question 38

Types of grid error

Answer 38

Off center
Off level
Upside down
Off focus

Question 39

Occurs when using an SID outside of the recommended range

Answer 39

Off focus grid error

Question 40

What does off focus grid error cause

Answer 40

Cutoff - lighter along the peripheries

Question 41

Causes a zebra effect

Answer 41

Moire Effect

Question 42

Observing grid lines on the image - mainly with CR

Answer 42

Moire Effect

Question 43

Another method for limiting scatter to reaching the IR - based on OID

Answer 43

Air Gap Technique

Question 44

Air gap technique will also cause this - unwanted

Answer 44

Magnification