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Physics > Test 1 > Flashcards

Test 1 Flashcards

1
Q

Patient thickness affects image quality by affecting

A

magnification, radiographic contrast, focal spot blue

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2
Q

The best way to minimize magnification is to use a

A

long SID

small OID

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3
Q

The most commonly used beam restricting device is the

A

variable collimator

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4
Q

The purpose of a grid is to achieve

A

improved image contrast

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5
Q

Which is the linear grid with the widest latitude for catering and focus?

A

6:1

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6
Q

If 10% of the viewbox light is transmitted though an area of film, what is the optical density in that area?

A

1

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7
Q

The three primary geometric factors affecting image quality are

A

magnification, distortion, and focal spot blur

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8
Q

Focal spot blue can be reduced by using a

A

small focal spot

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9
Q

? is defined as the ability to image two separate objects and visually detect one from the other

A

resolution

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10
Q

What is the formula for optical density?

A

OD=log10 (I0/It)

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11
Q

Which kVP selection would result in the most scattered x-rays in the image forming beam?

A

90 kVP

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12
Q

Decreasing the kVP will increae

A

patient dose

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13
Q

Contrast resolution is improved by

A

tight collimation, lower kVP, patient compression

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14
Q

The use of a compression device will increaee

A

Contrast

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15
Q

The use of ? improves contrast and reduces patient dose.

A

collimation

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16
Q

How can you improve image contrast with a heavy patient without increasing patient dose?

A

use tight collimation

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17
Q

Image contrast improves when more of ? radiation is removed.

A

scattered

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18
Q

Foreshortening is caused by

A

a(n) angled body part when the beam is perpendicular to the image receptor

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19
Q

A grid is constructed with ? strips and ? interspace material.

A

radiopaque

radiolucent

20
Q

A radiograph with a long scale of contrast will also have ? latitude and ? contrast.

A

wide, low

21
Q

Grids are designed to remove scattered x-rays before they reach

A

the image receptor

22
Q

What is the grid ratio of a grid with 3mm height, 0.025mm thick lead grid strips, and 0.3 mm thick interspace material?

A

10:1

23
Q

Optical density is directly controlled by changing the

A

mAs

24
Q

Subject contrast is affected by

A

patient thickness

25
Q

The three primary factors influencing the intensity of scatter in the image forming beam

A

kVP, fieldd size, and patient thickness

26
Q

The positive beam limiting device (PBL) ensures that the x-ray beam is collimated to

A

the image receptor size

27
Q

? is the degree of difference in optical density (OD) between areas of an image.

A

contrast

28
Q

The amount of scatter absorption in a grid depend on

A

The angle of the scattered photon
The height of the grid strips
The width of the interspace material

29
Q

The purpose of a grid is to achieve

A

improved image contrast

30
Q

The interspace material in grids is made of

A

aluminum, plastic

31
Q

Grids generally have a frequency of

A

60-110

32
Q

The most critical consideration when uing a crossed grid is

A

alignment (positioning latitude)

33
Q

How could contrast be improved on a bedside radiograph of a very large

A

use a grid
lower the kVp
use tight collimation

34
Q

Spatial resolution improves with decreased

A

screen blur, motion blue, geometric blur

35
Q

Radiographic ? is random fluctuation in the optical density of a radiograph

A

noise

36
Q

The slope of the ? portion of the characteristic curve shows the film contrast.

A

straight line

37
Q

A film with a characteristic curve showing a high slope would be useful when ? is needed

A

high contrast

38
Q

The three primary geometric factors affecting image quality are

A

magnification
distortion
focal spot blur

39
Q

Distortion can be reduced by

A

placing the object plane parallel to the image plane

40
Q

How could contrast be improved on a bedside radiograph of a very large patient?

A

use a grid
lower the kVp
use tight collimation

41
Q

Radiographic image quality is improved when the ? is increased

A

Source image distance

42
Q

Higher speed image receptors generally produce images with

A

increased noise

43
Q

An image receptor with ? can be use over a greater range of exposures

A

wide latitude

44
Q

The densities above 2.5 on a film are represented in the ? portion of the characteristic curve.

A

base and fog

45
Q

sharpness of detail can be improved by increasing

A

SID

46
Q

Lowering kVp ? patient dose and ? image contrast.

A

Increases, increases

Physics (7 decks)

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