Chapter 12

Question 1

Scatter, in diagnostic x-ray is primarily due to _________ effect

Answer 1

Compton

Question 2

What two major factors affect scatter production?

Answer 2

Tissue volume and kVp

Question 3

Tissue volume is dependent on:

Answer 3

Part thickness and field size

Question 4

What causes fog?

Answer 4

Scatter (unwanted radiation)

Question 5

What two things does beam restriction do?

Answer 5

Limits patient dose
Reduces scatter production

Question 6

True/False: Beam restriction and collimation are interchangable terms

Answer 6

True

Question 7

What is the relationship between collimation and field size?

Answer 7

Inverse proportional

Question 8

How does collimation affect contrast?

Answer 8

Less collimation = more scatter

Question 9

How does collimation affect mAs?

Answer 9

The more collimation = the more mAs needed

Question 10

Beam restricting devices

Answer 10

Aperture Diaphragms
Cones/Cylinders
Collimators

Question 11

Flat peice of lead with a small hole in it, it attaches to the collimator

Answer 11

Aperture diaphragms

Question 12

Long tube/cone that attaches to the collimator; most often used for dental imaging or small parts such as nasal bones and fingers

Answer 12

Cones/cylinders

Question 13

Most used form of beam restriction

Answer 13

Collimator

Question 14

How many lead shutters are in a collimator?

Answer 14

2-3 that can be adjusted using collimator controls

Question 15

Automatically sets the field size depending on what exam is being completed

Answer 15

Positive Beam-limiting Device (PBL)

Question 16

When was the grid invented?

Answer 16

1913

Question 17

Who invented the grid?

Answer 17

Gustave Bucky

Question 18

Drawback of using a grid

Answer 18

Requires more mAs

Question 19

What is grid frequency?

Answer 19

Number of lead strips per unit length

Question 20

What is grid ratio?

Answer 20

Ratio of the height of the lead strips and the distance between them

Question 21

Two types of linear grids

Answer 21

Long
Short

Question 22

These grids have lead lines that run parallel with the long axis of the grid

Answer 22

Long

Question 23

These grids have lead lines that run perp to the long axis of the grid

Answer 23

Short

Question 24

What is grid pattern?

Answer 24

Linear pattern of the lead lines within a grid

Question 25

2 types of grid patterns

Answer 25

Linear Cross-hatched

Question 26

Difference between linear and cross-hatched grids

Answer 26

Linear - lines running in one direction Cross hatched - lines running in two different directions, perp to each other

Question 27

What type of grid removes more scatter - linear or cross hatched?

Answer 27

Cross-hatched

Question 28

What is grid focus?

Answer 28

Refers to the orientation of the lead lines to one another

Question 29

2 types of grid focus

Answer 29

Parallel Focused

Question 30

Difference between parallel and focused grids?

Answer 30

Parallel - lines are parallel and used primarily in fluoro and mobile x-ray Focused - lines are angled to match beam divergence - designed to be used at specific distances

Question 31

Type of grid that is stationary, same size as IR, and usually taped to secure it to IR

Answer 31

Wafer grid

Question 32

Type of grid that is stationary, IR with a permanent grid mounted to the front surface

Answer 32

Grid cassette

Question 33

Type of grid that is stationary, designed to hold the IR so no tape is needed - most common type

Answer 33

Grid cap

Question 34

This type of grid moves slightly while the image is being taken

Answer 34

Reciprocating grid

Question 35

The decrease in the number of transmitted photons that reach the IR due to grid misalignment

Answer 35

Grid cutoff

Question 36

Grid cutoff caused by the grid being placed upside down

Answer 36

Upside-down focused

Question 37

Most common type of grid cutoff - the IR with grid is tilted and CR is not

Answer 37

Off-level

Question 38

What type of cutoff can occur with both focused and parallel grids?

Answer 38

Off-level

Question 39

Grid cutoff caused when the CR is not aligned to the center of the IR

Answer 39

Off-center

Question 40

Grid cutoff occurs when SID is outside of the focal range of the focused grid

Answer 40

Off-focus

Question 41

Zebra stripe pattern that occurs when the grid frequency of a stationary grid used in CR imaging is similar to the laser scanning frequency of the CR reader

Answer 41

Moire Effect

Question 42

How to eliminate the Moire effect

Answer 42

Use higher frequency grids or moving grids

Question 43

What is the Air Gap Technique

Answer 43

By increasing OID, we able to limit the amount of scatter that reaches the IR

Question 44

Increasing OID also increases:

Answer 44

Magnification