Scatter Radiation 1

Question 1

Scatter Radiation

Answer 1

is any radiation that has been changed from its original path.
• It occurs as a result of x-rays interacting with atoms of matter
Greatest source of scatter radiation is the patient

Question 2

Primary X-rays or useful beam

Answer 2

The x-rays between the source and the patient

Question 3

Secondary or remnant X-rays

Answer 3

The x-rays between the patient and the image receptor

Secondary x-rays are made up of both primary and scattered x- rays

Question 4

Scatter Effect

Answer 4

The more scatter, the more noise or fog in the image, losing quality in the image.

Question 5

What does scatter radiation do to an image?

Answer 5

Scattered radiation reduces image quality and causes a loss of radiographic contrast due to a graying or clouding of the image, commonly called fog (film/screen) or noise (digital).

Question 6

The amount of scatter radiation that is created is affected by what 4 factors?

Answer 6

1. Area of radiation field
   2.kVp
2. Part thickness
3. Tissue density

Question 7

Area of radiation field

Answer 7

The greater the area of field, the greater the amount of scattered radiation that is produced (and vice versa).

Question 8

KVp

Answer 8

As kVp is increased, the production of scattered radiation increases, and a higher percentage of these x-rays will reach the image receptor.

Question 9

Part thickness

Answer 9

The thicker the part, the more scattered radiation will be produced because more matter is present to interact with x-rays.

Question 10

Tissue density

Answer 10

The greater the tissue density, the greater the amount of scattered radiation because more atoms are in the path of the x-ray beam.

Question 11

A comparison of two regions of the body with different tissue densities in terms of radiation exiting the part:

Answer 11

1. Chest – 50% scattered radiation; 50% primary
2. Abdomen – 90% scattered radiation; 10% primary

Question 12

Grid

Answer 12

Invented in 1913 by Dr. Gustave Bucky in Chicago.
• This device should be used anytime: • part thickness exceeds 10 cm
• and/or above 70 kVp.
• This is the most common device to prevent scatter radiation from reaching the image receptor.

Question 13

What types of materials are grids made out of?

Answer 13

1. Radiolucent
2. Radiopaque

Question 14

Radiopaque strips

Answer 14

0.05 mm wide

Question 15

Radiolucent strips

Answer 15

0.33 mm wide

Question 16

The principle behind the grid is

Answer 16

Primary x-rays can pass through the radiolucent interspace material while scattered x-rays are absorbed in the radiopaque strips.

Question 17

What are the main types of grids?

Answer 17

1. Linear
2. Crosshatch or cellular
3. Multi-hole
4. Virtual

Question 18

Linear

Answer 18

consists of one set of lead strips that run in a straight line in one direction.
These are most often installed in table Bucky’s.

Question 19

What are the 2 basic types of linear grids?

Answer 19

1. Parallel
2. Focused

Question 20

Parallel linear grid

Answer 20

When viewed from the side, the lead strips run parallel to each other.
• Used for small size image receptors, long SID, or mobile radiography

Question 21

Focused linear grids

Answer 21

Lead strips are focused toward a convergence point, a process known as canting.
• This is found in most exposure rooms and used for routine SID’s and any image receptor size.

Question 22

Where are focus grids found?

Answer 22

In table bucky’s because the tube can be locked over the center of the grid and image receptor.

Question 23

Criss-cross, cross hatch,or cellular grids

Answer 23

Most efficient grid for removing scattered radiation because there are two sets of lead strips mounted at 45 or 90 degrees to each other.

Question 24

Disadvantages of cross hatch grids

Answer 24

no angling of the x-ray beam, higher patient dose, and centering is critical.

Question 25

What are the 2 types of cross hatch grids?

Answer 25

1. Orthogonal
2. Rhombic

Question 26

Orthogonal cross hatch grid

Answer 26

Lead strips are mounted at 90 degree angles to each other.

Question 27

Rhombic cross hatch grid

Answer 27

Lead strips are mounted at 45 degree angles to each other.

Question 28

Multi hole grids

Answer 28

This type of grid was developed to be used with early CR systems to prevent Moire’ artifacts.

Question 29

What are moire or zebra patterned artifacts?

Answer 29

when the grid lines and the CR scan lines are similar in number and run in the same direction.

Question 30

Virtual grid

Answer 30

Not a physical grid like the previous types
• It is a software program that reduces gray shades created by scatter in DR images.
• This system can reduce patient dose up to 50%

Question 31

Lead content

Answer 31

the amount of lead used in the construction of a grid and measured in units of grams/cm2.

Question 32

Grid focusing distance

Answer 32

Formally called grid radius

This is the proper SID that a focused grid will operate due to the alignment of the lead strips with the x-ray beam.

Question 33

Grid cutoff

Answer 33

absorption of primary or useful radiation by the grid, resulting in an underexposed radiograph.

Question 34

Stationary Grid

Answer 34

the grid does not move during the exposure. Results in grid lines in the resulting image.

Question 35

Grid Lines

Answer 35

shadows of lead strips appearing on the radiograph.

Question 36

Moving Grid

Answer 36

– invented in 1920 by Dr. Hollis Potter.
• It is designed to eliminate grid lines by moving the grid during the exposure, and can be found in three basic types:
1. Single -stroke
2. Recipromatic
3.Reciprocating

A moving grid requires a 15% increase in mAs over a stationary grid.

Question 37

Single stroke

Answer 37

Spring activated and found only in older equipment

Question 38

Reciprocating

Answer 38

Grid is moved by a solenoid

Question 39

Recipromatic

Answer 39

Uses an electric motor to move the grid

Question 40

Potter Bucky diaphragm

Answer 40

Formal name for the assembly that contains the grid, the device that moves the grid, and the metal tray that holds the image receptor and mounted below the tabletop of a radiographic unit.
Known as Bucky for short

Question 41

Grid latitude

Answer 41

Margin of error for centering the primary beam to the grid