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Flashcards in Scatter Radiation Study Guide Deck (78)
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1

What characteristics are important to image quality?

contrast and contrast resolution

2

What is contrast?

differences of light and dark on an x-ray image

3

What is the number of shades of gray on an image?

scale of contrast

4

The ability to image adjacent similiar tissues is defined as?

contrast resolution

5

What three factors contribute to the production of scatter radiation?

increased kVp
increased x-ray field size
increased patient thickness

6

What is designed to minimize the production of scatter by limiting field size to only the anatomy of interest?

Beam restricting devices

7

The three principle types of beam restricting devices are?

aperture diaphragms, cone or cylinders and collimators

8

What two types of x-rays are responsible for Optical Density and contrast on an image?

1. those that pass through the patient without interacting (transmitted)
2. those that are compton scatter within the patient

9

Define Remnant x-rays:

x-rays that exit the patient

10

Define Image forming x-rays:

x-rays that exit and interact with the image receptor

11

What does collimation do?

reduces patient dose and improves contrast resolution

12

As scatter radiation increases what happens to the image?

it loses contrast and becomes gray/dull

13

If kVp increases what happens to relative amount of scatter?

it increases

14

If kVp decreases what happens to patient dose?

it increases

15

As the thickness of the patient increases what happens to the probability of scatter?

it increases

16

One way to reduce the production of scatter is by imaging a thinner part by using?

constriction bands or compression paddles

17

If radiation field size increases what happens to the tissue being irradiated? Amount of scatter being produced?

it increases
it increases

18

What device helps to minimize the amount of scatter produced?

beam restrictors

19

What device helps clean up the scatter that has been produced?

grids

20

What type of beam restricting device is the simplest one that consists of a lead plate with a hole cut in it. The size of the opening determines the field size?

Aperture Diaphragms

21

X-rays being produced on other parts of the anode than the focal spot is called?

off- focus x-rays

22

What x-rays increase blur in the image?

off focus x-rays

23

What does positive beam limitation do?

automatically collimates to the size of the IR used.

24

Under NO circumstance should the x-ray beam?

exceed the size of the IR

25

When the beam is restricted the technique should? why?

increase to compensate for the loss of x-rays in the beam reaching the IR

26

Scatter makes?

Fog

27

Fog is?

Density

28

Removing scatter does what to the optical density?

decreases which makes the image lighter therefore mAs must increase

29

What is designed to transmit only x-rays whose direction is on a straight line to the IR?

Grid

30

Grids have three important dimensions:

1. thickness of the lead strips (T)
2.thickness of the interspace or interspace distance (D)
3.height of the grid strip (h)