EXPOSURE FACTORS

An SID of ___ to____ inches is sufficient to minimize the penumbra effect.

36 to 40 inches

______is the time in fractions of a second during which the anode is positively charged.

Exposure time

_______ is a quality factor that regulates the energy of the x-ray beam.

Kilovoltage

________ is defined as the differences in radiographic density between adjacent areas on a radiographic image.

Radiographic contrast

Subject density is the

ability of the different tissue densities to absorb x-rays.

With increasing density, the tissue will

appear whiter, or more radiopaque, as it absorbs more of the radiation.

A short scale of contrast has

black and white shades, with only a few shades of gray in between.

Radiographic density is the degree of

blackness on a radiograph.

High kVp techniques are most useful for studies of

body regions with many different tissue densities (ex. thorax).

mAs is the actual number of x-rays that are

coming down to the target.

Use of high kVp results in a

darker image (low or decreased contrast, long scale of contrast)

The kVp setting must be high enough to penetrate the patient, but not so high as to

decrease contrast.

The extent to which x-rays penetrate the various tissues depends on the

differences in atomic number and thickness.

Contrast is necessary to

differentiate anatomic structures of an image.

source image distance (SID) or film focal distance (FFD) is the

distance between the source of the x-ray and the film.

The film focal distance refers to the

distance between the target in the x-ray tube and the surface of the x-ray detector.

object image distance (OID) is the

distance from the object being imaged to the film or recording surface as is the case for digital radiography

kVp is the

energy of the x-ray.

Radiographs that show a long scale of contrast have a

few black and white shades, with many shades of gray.

The longer the exposure time, the greater is the number of electrons that

flow from cathode to anode, the greater the number of x-ray photons produced.

Bone, containing mainly calcium and phosphorous, has a

higher average atomic number

Using low kVp settings produces a

higher contrast (short scale of contrast) image

Increasing the kilovoltage will also

increase radiographic density, or film blackness

Increasing the kilovoltage will also increase radiographic density, or film blackness, because of the

increased x-ray photons passing through the patient.

The penumbra effect can be decreased by

increasing the source image distance

Three main factors influence the amount of penumbra on a radiograph.

large focal spot source image distance (SID) or film focal distance (FFD). object image distance (OID).

darker image (low or decreased contrast, long scale of contrast) shows

little difference in opacity between bone, soft tissue, and fat.

Foreshortening occurs mainly when imaging the

long bones, such as the humerus and femur.

A blurred image is generally a result of

long exposure time combined with motion of the patient.

most recent x-ray machines have a common dial for time of exposure and milliamperage, called the

mAs setting.

your goal is to have the highest_______ and the lowest _______to arrive at the desired mAs.

milliamperage setting;time setting

higher contrast/short scale of contrast) image is

more black and white in appearance with few grays

when mA is increased, the temperature of the filament is increased, producing

more electrons to form the electron cloud.

The penumbra is decreased by keeping the

object image distance (OID) as short as possible.

Foreshortening occurs when the

object is not parallel to the recording surface.

Increasing the OID increases the

penumbra and greatly magnifies the size of the object.

A loss of detail is also caused by the

penumbra effect.

When x-rays pass out of the x-ray tube, stray x-rays cause fuzziness which is known as

penumbra.

when you decrease the milliamperage setting, there is a reduction in _______

radiographic density (or a lighter film).

When you increase the milliamperage setting, _______ is increased;

radiographic density (or film blackness)

On radiographs, air and lung tissue will appear

radiolucent or black,

The kilovoltage setting affects the

scale of contrast or the number of shades of gray

Foreshortening distorts size by

shortening the length of the object.

You always want the ________to decrease patient motion blur which results in loss of detail.

shortest exposure time

A blurred image can be controlled by using the

shortest possible exposure.

The higher the voltage, the faster the electrons are accelerating, the greater the energy of the x-ray beam,

the greater the amount of patient tissue that can be penetrated.

The larger the focal spot, the more pronounced

the penumbra effect.

The milliamperage setting controls the quantity of electrons boiled off the filament in the x-ray tube, in other words,

the quantity of x-rays that will be produced at the target area.

The penumbra effect can be decreased by increasing the source image distance because

the x-rays from the focal spot spread less after they pass the object on the way to the film.

So kVp is adjusted based on the

thickness of the body part.

The three exposure factors are

time of exposure, milliamperage, and kilovoltage.