4. Prime Factors Flashcards
controls both the quantity and quality of the x-ray beam
Kilovoltage (kVp)
Increasing kilovoltage on an x-ray control panel will cause an
______ in the speed and energy of the electrons applied across
the x-ray tube.
increase
Kilovoltage affects the _____ of the x-ray beam because more interactions occur at the target as kVp increases
quantity
Kilovoltage affects
the _____ of the x-ray beam because each electron has more
energy, resulting in a beam with greater penetrability.
quality
The quantity (intensity) of x-ray photons increases very quickly with \_\_\_\_\_\_ in kVp
increases
Both the _____ and _____ x-ray beam will vary significantly with changes in the kilovoltage applied across the x-ray tube
quantity,
quality
Because changes in kilovoltage create changes in beam
penetrability, _____ is the primary controller of the differences in radiographic densities and this is known
as contrast
kVp
15% rule states that an increase in kVp by 15% will cause a ______ in exposure, the same effect as ______ the mA or ______ exposure time
doubling,
doubling,
doubling
The intensity of x-rays varies greatly with
changes in
distance
The measurement of the x-ray
intensity is obtained using a _______
dosimeter
X-ray intensity (exposure) is
measured in ______ or
more commonly in diagnostic
radiology in
Roentgens (R),
milliroentgens (mR)
The actual number of photons created
remains ______ but the distribution of the photons _____ with the distance
unchanged,
varies
states that the intensity of radiation at a given distance from the point source is inversely proportional to the square of the distance
inverse square law
As the distance increases, intensity ______, which causes a ______ in
exposure to the image
receptor
decreases,
decrease
The formula is sometimes known as the _________ and is based on the principle of the inverse square law.
exposure (film density) maintenance formula
As the distance decreases, intensity _____ which in turn causes an ______ in radiographic film density
increases,
increase
a direct relationship is necessary to compensate for the changes in intensity and film density
Direct square Law
Changes in the distance will create _____ in the x-ray intensity and the radiographic density
changes
With digital image detector systems, the traditional relationship between the image quality properties of density and contrast to ___, ___ and _____ does not exist
mAs,
kVp,
distance
it is possible to change the mAs, kVp and distance and have ______on the density (brightness) or contrast on the display
monitor
no effect
Despite the ability to control density and contrast through _______, it is still critical to provide the digital image receptor with an appropriate exposure for a given procedure
post-processing parameters
Setting the appropriate
mAs, kVp and distance is the ______ radiographer
responsibility
Three (3) factors that affect x-ray emission are under the direct control of the radiographer:
- ) milliamperage-second (mAs)
- ) kilovoltage (kVp)
- ) distance (d)
is a measure of the number of x-ray
photons in the useful beam
X-ray quantity
X-ray quantity also called as
x-ray output, intensity or exposure
unit of measurement of x-ray quantity
Roentgen (R)
Factors that affect x-ray quantity are:
mAs, kVp, distance and Filtration
measurement of the penetrating ability
of the x-ray beam
X-ray quality
describes the distance an x-ray beam
travels in matter
Penetrability
Highly penetrating x-rays are termed as
hard x-rays
Low penetrating x-rays are termed as
soft x-rays
X-ray quality is numerically represented by the
Half-Value Layer (HVL)
is that thickness
of absorbing material needed to reduce the x-ray intensity (quantity) to half its original value
Half-Value Layer (HVL) of an x-ray beam
The factors that affect x-ray quality are:
kVp,
Filtration
is a measurement of x-ray tube current – the number of electrons crossing the tube from cathode to anode per second
Milliamperage (mA)
is directly proportional to tube current
Milliamperage
mA _____, so does the number of electrons able to cross the tube
doubles
The number of electrons reaching the target is also
controlled by the_____ the tube is energized
length of time
Like milliamperage (mA), ______ is directly
proportional to the number of electrons crossing the
tube and is therefore directly proportional to the number of x-rays created
exposure time
number of electrons crossing the tube
tube current
how long the electrons are allowed to cross
exposure time
a product of the number of electrons crossing the tube (tube current) and how long the electrons are allowed to cross (exposure time)
The number of x-rays that will be created at the target
is the unit used to describe the product of tube current and exposure time
Milliamperage-second (mAs)
milliamperage (mA) x seconds (s) =
Milliamperage-second (mAs)
is the primary controller of x-ray quantity
mAs
On the radiographic image, the _____ are the result of an x-ray exposure to the film and intensifying screens
densities
While the relationship between mAs and exposure (mR) is a ______ proportional one, the relationship of these 2 factors to film density is much more complex
directly
Film density is determined by
the amount of silver
deposition in the emulsion due to the film type, exposure conditions, exposure (mR), and processing
durable protection layer
Supercoat
radiation and light-sensitive layer
Emulsion
adheres layers together
Adhesive
polyester layer that gives the film physical stability
Film base
expresses the relationship between exposure and density, with log relative exposure plotted on the x-axis and density (D) plotted on the x-ray axis (y-axis)
D log E sensitometric curve
Since density is primarily determined by the amount of exposure a film receives, and since exposure is directly proportional to mAs, _____ is used as the primary controller of radiographic film density
mAs
As mAs increases, x-ray exposure ______
proportionally then radiographic density also ______.
increases,
increases
The relationship of a film’s reaction to exposure was described in ____ by _______ who studied the reaction of a photographic film to light is equal to the product of the intensity of the light and the duration of the exposure
1875,
Bunsen & Roscoe
The reaction of a photographic film to light is equal to the product of the intensity of the light and the duration of the exposure, this concept is called the
Reciprocity law
OD (Optical Density) of a radiograph is proportional only to the total energy imparted to the radiographic film
Reciprocity law
If applied to x-rays, the ______ can be restated as the density on an x-ray film should remain unchanged as long as the intensity and duration of the x-ray exposure (controlled by mAs) remains unchanged
Reciprocity law
This law generally is true for x-ray films exposed is from light and not x-rays
Reciprocity law
The reciprocity law fails for exposures made at ________
extremely short exposure times (less than 1/100 second)
or extremely long exposure times (more than a second)
Radiographic film density should remain _______ as
long as the total exposure to the film remains unchanged
unchanged
is the primary controlling
factor that will affect the x-ray quantity and
radiographic density
Milliamperage-second (mAs)
device that measures the degree of darkening of the radiographic film
Densitometer
modality that uses soft x-rays
Mammography
range of the density that offers diagnostic value
0.25-2.5
distance for vertical grid
72 inches
distance for horizontal grid
40 inches
