Chapter 26 and 27

A change in kVp, as an exposure factor, affects

-average beam energy -beam intensity -the amount of scatter production

Contrast decreases with

-excessive density -inadequate density -a wider range of densities

An increase in x-ray beam filtration

-increases the number of compton interactions -reduces contrast -increases the average photon energy

A radiograph that demonstrates minimal differences between densities is called

-long scale -low contrast -decreased contrast

In the event of making a single exposure that is critical to the exam success, most experiences technologists will

-overexpose the IR slightly -provide enough exposure to permit viewing with a bright light or adequate histogram analysis B and C

A radiograph that demonstrates considerable differences between densities is called

-short scale -high contrast -increased contrast

The recorded detail of a radiographic image is visible because of

-sufficient contrast -sufficient density

Optimum exposure to an IR is

1 mR plus or minus 33%

What rule is used as a guide to maintain the same density when kVp changes?

15% rule

The minimum change necessary to cause a visible shift in density is ________ percent of mAs.

25-30

Depending upon the kVp range, a visible change in contrast will not be seen unless kVp is minimally changed

4-12%

Which statement is false? As mAs increases, exposure increases As mAs decreases, density decreases As mAs increases, density decreases As mAs decreases, exposure increases

As mAs decreases, exposure increases

The anode heel effect is more pronounced with

a 10 degree target angle

The brightness of the image on a viewing monitor is

a function of the monitor

Which generator produces the greatest amount of radiographic density per mAs? single phase, 2 pulse three-phase, 6-pulse three-phase, 12-pulse a high frequency generator

a high frequency generator

When digital imaging receptors are used,

an exposure of 90 kVp would require a grid

The total amount of irradiated material is a function of

body part thickness and area of exposure

kVp controls the proportional relationship

compton and photoelectric interactions

When changing your SID from 72" to 56"

decrease your mAs by 50%

The 15% rule changes

density and contrast

The effect of mAs upon IR exposure is

directly proportional

The concept of contrast as it is displayed on a soft-copy monitor for digital images is described as

dynamic range

All of the following would affect radiographic contrast except -field size -SID and OID -receptor characteristics -focal spot selection

focal spot selection

A radiograph that demonstrates considerable sifferences between densities is called

high contrast

A radiograph with few shades of gray exhibits

high contrast

When choosing between two radiographic grids, the k factor is different. Choosing a grid with the higher k factor will produce an image with

high contrast

Focal spot blooming occurs with

high mAs

When the tissue structure of the ankle joint is considered, the dramatic tissue difference between the muscles and bones of the ankle produce

high subject contrast

With digital imaging systems, the primary factors affecting final image contrast are the

histogram and look up table (LUT)

Contrast increases with all of the following except -decreased kVp -decreased field size -decreased part thickness -increased scatter

increased scatter

As kVp increases, the percentage of Compton interactions ____ and contrast _____.

increases; decreases

As kVp ______, a _____ range of photon energies is produced.

increases; wider

Which does not increase contrast? -increasing grid ratio -increasing the amount of irradiated tissue -decreasing filtration -decreasing kVp

increasing the amount of irradiated tissue

The density maintenance formula mathematically resembles the

inverse square law

The relationship between exposure and SID is

inversely proportional to the square of the distance

Because of the "heel effect" x-ray beam intensity

is greater under the cathode side of the tube

The principal controlling factor of contrast is

kVp

What factor influences the average energy of photons reaching the IR?

kVp

In order to reduce patient entrance skin exposure (ESE), higher kVp exposures are a consideration. It is important to remember that

kVp values that are too high produce more scatter and reduce contrast

A radiograph that demonstrates minimal differences between density shades is called

low contrast

Which type of radiograph provides the most energy?

low contrast images

The principal controlling factor of radiographic image density is

mAs

What factor influences the number of photons reaching the IR?

mAs

As you analyze an image, you come to the conclusion that it must have more exposure. As a general rule, you should increase

mAs by 2x

What should you expect to occur with a decrease in kVp?

more photoelectric interactions

The greatest factor in the production of scatter radiation is

patient thickness

The difference between two adjacent densities is

radiographic contrast

A flouroscopic examination that uses barium as a contrast material would typically produce images with

short scale contrast

Which generator produces the least amount of radiographic density per mAs? single phase, 2 pulse three-phase, 6-pulse three-phase, 12-pulse a high frequency generator

single phase, 2 pulse

What conclusion can you reach regarding an image with an S# of 750 and good radiographic image density on the display monitor?

the image is likely to demonstrate noise or quantum mottle

High contrast is directly related to

the number of photoelectric interactions

Image brightness on an image display monitor is controlled by

window level