Image production & evaluation

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Comparison of Technical Factors Required

Single-Phase (x mAs)
Three-Phase, 6-Pulse (2/3x mAs)
Three-Phase, 12-Pulse (1/2x mAs)

With three-phase equipment, the voltage never drops to

zero

With three-phase equipment x-ray intensity is

significantly greater.

When changing from single-phase to three-phase, six-pulse equipment,

two thirds of the original mAs are required to produce a radiograph with similar density

When going from three-phase, six-pulse to single-phase, add

one-third more mAs.

When changing from single-phase to 3-phase, 12-pulse equipment,

only one-half of the original mAs is required.

Going from three-phase, 12-pulse to single-phase requires

twice the mAs.

changing from single-phase to three-phase, 12-pulse equipment; therefore the new mAs should be

half the original

The amount of replenisher solution added as a film enters the automatic processor is related to the

1. size of the film.
2. number of films processed.

Each film passing through the processor solutions

takes with it a certain amount of solution

Replenishment is also essential for

maintaining each solution's level of concentration, to maintain solution activity and avoid chemical fog from exhausted solutions.

One way to determine the quantity of replenisher solution to be added is by

the length of the film entering the processor.

A microswitch initiates and terminates replenishment as

it senses the beginning and end of each film.

Replenishment is also determined by

the number of films (volume) processed.

The greater the number of films processed,

the lower the required replenishment rate

Greater latitude is available to the radiographer when using

1. high kVp factors.
2. a slow film-screen combination.

Which of the following adult radiographic examinations usually require(s) use of a grid?

1. Ribs
2. Vertebrae
3. Shoulder

anatomic parts measuring in excess of 10 cm require

a grid.

The major exception to this rule is

the chest

The larger the part,

the more scattered radiation is generated.

Parts generally requiring the use of a grid include

the skull, spine, ribs, pelvis, shoulder, and femur.

osteomalacia, fibrosarcoma, and paralytic ileus (obstruction), result in a

decrease in body tissue density.

The technical factors mAs, kVp, and grid ratio have no effect on

recorded detail.

A radiograph exposed using a 12:1 ratio grid may exhibit a loss of density at its lateral edges because the

SID was too great

If the grid failed to move during the exposure, there would be

grid lines throughout.

If the central ray was off-center, there would be

uniform loss of density.

If the x-ray tube is angled significantly across the lead strips of a focused grid, there is

uniform loss of density (grid cutoff)

Insufficient or excessive distance with focused grids causes

loss of density (grid cutoff) along the periphery of the image.

An increase in exposure factors is usually required in which of the following circumstances?

1. Edema
2. Ascites
3. Acromegaly

acromegaly

an increase in bone size and density

The fact that x-ray intensity across the primary beam can vary as much as 45% describes the

anode heel effect

The anode heel effect becomes more pronounced as

the SID decreases, as IR size increases, and as target angle decreases.

A higher milliamperage with a short exposure time is generally

preferable

Which of the following methods can be effectively used to decrease differential absorption, providing a longer scale of contrast in the diagnostic range?

1. Using high kVp and low mAs factors
2. Using compensating filtration

The photoelectric effect

the interaction between x-ray photons and matter that occurs at low kVp levels—levels that tend to produce short-scale contrast.

Which of the following function(s) to reduce the amount of scattered radiation reaching the IR?

1. Grid devices
2. Beam restrictors

Which portion of the characteristic curve would most likely represent a density of 1.0?

Straight-line portion

A characteristic curve is used to

predict the speed, contrast, and exposure latitude of a particular film emulsion.

A characteristic curve compares

the exposure, given the film with the resultant density

A characteristic curve has three portions:

the toe, the straight-line portion (region of correct exposure), and the shoulder

The toe

occurs immediately after base-plus fog, whose density must not exceed 0.2.

straight-line portion

follows the toe; portion of correct exposure and extends from about 0.25 to 2.5

The curve then bends and levels off at the

shoulder (Dmax) portion of the curve.

Which of the following factors affect(s) both radiographic density and intensifying screen speed?

1. Thickness of phosphor layer
2. Type of phosphors used

Factors that affect screen speed will also affect

radiographic density.

Rare earth-type phosphors

absorb x-rays more efficiently and convert their energy into fluorescent light; they therefore affect both screen speed and radiographic density

The thickness of the phosphor layer affects

speed and density similarly: As the thickness of the phosphor layer increases, speed and density increase.

The spongy layer behind each intensifying screen helps ensure

good screen-film contact and therefore good recorded detail. The spongy layer is unrelated to radiographic density.

Which of the following can affect histogram appearance?

1. Centering accuracy
2. Positioning accuracy
3. Processing algorithm accuracy

The CR laser scanner recognizes the various tissue density values and constructs a

representative gray-scale histogram

A histogram is a

graphic representation showing the distribution of pixel values

Histogram analysis and use of the appropriate LUT together function to

produce predictable image quality in CR.

Degree of accuracy in positioning and centering

can have a significant effect on histogram appearance (as well as patient dose)

Change is affected in

average exposure level and exposure's latitude; these changes will be reflected in the images informational numbers ("S number," "Exposure Index," etc)

Other factors affecting histogram appearance and, therefore, these informational numbers, include

selection of the correct processing algorithm (e.g., chest vs femur vs cervical spine), changes in scatter, SID, OID, and collimation.

How would the introduction of a 6-inch OID affect image contrast?

Contrast would be increased

ID can affect contrast when it is used as

an air gap.

If a 6-inch air gap (OID) is introduced between the part and IR

much of the scattered radiation emitted from the body will not reach the IR

The OID is thus acting as a

low-ratio grid and increasing image contrast.

A technique chart should include which of the following information?

1. Recommended SID
2. Grid ratio
3. Screen-film combination

Technique charts are

exposure factor guides that help technologists produce radiographs with consistent density and contrast

They suggest a group of exposure factors to be used at

a particular SID with a particular grid ratio, screen-film combination, focal spot size, and central ray angulation.

Technique charts do not take into account

the nature of the part (disease, atrophy, etc)

Recorded detail is directly related to

source-image distance (SID)

As SID increases, so does

recorded detail, because magnification is decreased

SID is directly related to

recorded detail.

As focal spot size increases, recorded detail

decreases because more penumbra is produced.

Focal spot size is thus inversely related to

radiographic sharpness or recorded detail.

Tube current affects

radiographic density and is unrelated to recorded detail.

In which of the following ways can higher radiographic contrast be obtained in abdominal radiography?

1. By using lower kilovoltage
2. By using a contrast medium
3. By limiting the field size

Higher contrast is

shorter scale contrast; it is present in an image that has few shades of gray between white and black.

High radiographic contrast is, in part, a result of

lower energy photons (lower kVp).

High radiographic contrast also results when

radiographing anatomic parts that have high subject contrast, such as the chest.

The abdomen has low

subject contrast, and therefore abdominal radiographs will tend to have very low contrast unless technical factors are selected to increase contrast.

To produce high radiographic contrast in abdominal radiography,

lower kVp should be used.

To better demonstrate high contrast within a viscus

a contrast medium such as barium, iodine, or air can be used.

Restricting the size of the field will also function to

increase contrast because less scattered radiation will be generated.

Which of the following pathologic conditions are considered additive conditions with respect to selection of exposure factors?

1. Osteoma
2. Bronchiectasis
3. Pneumonia

Osteoma

or exostosis, is a (usually benign) bony tumor that can develop on bone

Bronchiectasis

is a chronic dilatation of the bronchi with accumulation of fluid

Pneumonia

is inflammation of the lung(s) with accumulation of fluid.

A grid is usually employed

1. when radiographing a large or dense body part.
2. when using high kilovoltage.

The function of the developer solution chemicals is to

reduce the latent image to a manifest image

The latent image is

the invisible image produced within the film emulsion as a result of exposure to radiation

unexposed crystals are removed from the film during

the fixing process.

Penetration and contrast are a function of

kilovoltage

Inadequate penetration and high contrast are a result of insufficient

kVp

How can the radiographer reduce the amount of scattered radiation generated during a radiographic examination?

1. Use optimum kVp.
2. Collimate closely.

The amount of scattered radiation generated in a given exposure increases as three factors increase:

the kVp, the field size, and the thickness and density of the tissues.

Geometric unsharpness is influenced by which of the following?

1. Distance from object to image
2. Distance from focus to object
3. Distance from focus to image

As focal-object distance and SID decrease, so does

magnification

OID may be said to be directly proportional to

magnification.

Focal-object distance and SID are inversely proportional to

magnification

If single-emulsion film was loaded into its cassette with the emulsion facing away from the intensifying screen, the resulting image would demonstrate

decreased density

Single-emulsion film is used for particular examinations, such as

mammography

Single-emulsion film is used

with a cassette that has a single intensifying screen and provides better detail than typical double-emulsion film and two-screen cassettes

It is essential that the light-sensitive emulsion be placed against the

light-emitting screen

Single-emulsion film has an antihalation backing that

efficiently absorbs reflected (crossover) light.

if the film were loaded with the antihalation side against the light-emitting screen, the film emulsion would

receive very little exposure

The processor rollers that are out of solution and function to transfer the film from one solution to another are the

crossover rollers

Turnaround assemblies

are located at the bottom of each solution tank and function to direct the film from a downward to an upward motion

Guide shoes

also called deflector plates, serve to keep the film on its proper course by directing or guiding it around corners.

The crossover rollers

are located at the top of the processor, out of the solution, and direct the film from one solution tank to the next. These are the racks that need daily cleaning to avoid chemical or emulsion buildup on their surface. Chemical or emulsion buildup on roller surfaces can cause film artifacts.

Which type of error results in grid cutoff at the periphery of the radiographic image?

Off-focus

If the x-ray beam is not centered to the grid, or if the x-ray tube and grid surface are not parallel (level), there will be a fairly uniform decrease in

radiographic density across the entire image.

if the grid is not used within its recommended SID (focus) range (ie, if the SID is too great or too little), there will be

a decrease in density at the periphery of the image.

All of the following are related to recorded detail

A. motion.
B. film-screen contact.
C. SID.

Motion

is said to be the greatest enemy of recorded detail because it completely obliterates image sharpness

Poor screen-film contact

reduces recorded detail because of the degree of light diffusion in the areas of poor contact. Areas of poor contact appear blurry.

A decrease in source-image distance causes

magnification and blurriness of recorded detail.

Which of the following conditions require(s) a decrease in technical factors?

1. Emphysema
2. Osteomalacia

Subcutaneous emphysema

is a pathologic distention of tissues with air

pulmonary emphysema

a chronic disease characterized by overdistention of the alveoli with air.

Osteomalacia

a softening of bone so that it becomes flexible, brittle, and deformed

Atelectasis

a collapsed or airless lung; it requires an increase in exposure factors.

If the quantity of black metallic silver on a particular radiograph is such that it allows 1% of the illuminator light to pass through the image, that image has a density of

2.0

If 10% of the illuminator's light passes through the image, that image has a density of

1.0

What should be done to correct for magnification when using air-gap technique?

Increase SID

OID is used to effect

an increase in contrast in the absence of a grid, usually in chest radiography

OID acts as a

low-ratio grid and increases image contrast.

the SID needs to be increased 7 inches for every

1 inch of OID.

With a 6-inch OID, the SID is usually increased from 6 feet to

10 feet (120 inches)

Geometric unsharpness is most likely to be greater

at the cathode end of the image

The x-ray tube anode is designed according to the

line focus principle, that is, with the focal track beveled

This allows a larger actual focal spot to project a

smaller effective focal spot, resulting in improved recorded detail with less blur

because of the target angle,

penumbral blur varies along the longitudinal tube axis, being greater at the cathode end of the image and less at the anode end of the image.

Which of the following will have an effect on radiographic contrast?

1. Beam restriction
2. Grids

Radiographic contrast is described as

the difference between densities, or scale of grays, in the radiographic image.

the function of grids is to

collect scattered radiation, they serve to shorten the scale of contrast.

Beam restrictors function to

limit the x-ray field size, thereby reducing the production of scattered radiation and shortening the scale of contrast.

Focal spot size

one of the geometric factors affecting recorded detail; it has no effect on the scale of contrast.

It is the function of radiographic contrast to

make details visible

The sum of subject contrast and film contrast equals

radiographic contrast.

When the collimated field must extend past the edge of the body, allowing primary radiation to strike the tabletop, as in a lateral lumbar spine, what may be done to prevent excessive radiographic density due to undercutting?

Use lead rubber to absorb tabletop primary radiation

When the primary beam is restricted to an area near the periphery of the body, sometimes

part of the illuminated area overhangs the edge of the body

If the exposure is then made, scattered radiation from the tabletop (where there is no absorber) will undercut the part, causing

excessive image density.

If, however, a lead rubber mat is placed on the overhanging illuminated area, most of this scatter will be

absorbed.

This is frequently helpful in

lateral lumbar spines and AP shoulders

Improper spectral matching between rare earth intensifying screens and film emulsion results in

insufficient density

If, for example, a blue-sensitive emulsion were matched with green-emitting screens, the resulting radiograph would be

underexposed because the blue-sensitive film emulsion was not responsive to the green-emitting phosphors.

In which of the following examinations would a cassette front with very low absorption properties be especially desirable?

Mammography

Because mammographic techniques operate at very low kVp levels, the cassette front material

becomes especially important.

The use of soft, low-energy x-ray photons is the underlying principle of

mammography; any attenuation of the beam would be most undesirable

Special plastics that resist impact and heat softening, such as polystyrene and polycarbonate, are frequently used as

cassette front material

The presence of dust or scratches on intensifying screens will cause

decreased density in those areas of the image

If intensifying-screen phosphors are covered with dust

either they will not fluoresce or their fluorescence will not reach the IR emulsion

if the screen is scratched and phosphors are removed,

there will be no fluorescence to expose the IR.

The principal quantitative factor regulating radiographic (or optical) density is

mAs

The mAs selected is directly proportional to

radiographic density (ie, if the mAs is cut in half, radiographic density will be halved)

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