CHAPTER 5 Flashcards
It is a photographic factor that also affects the visibility of recorded detail.
Radiographic contrast
It is the degree of difference between adjacent densities
Contrast
The ability to distinguish between densities enables differences in ___________ to be visualized
Anatomic tissues
An image that has SUFFICIENT density, but no differences intensity would appear as a ___________
Homogeneous object
The appearance of homogeneous object would indicate that the ABSORPTION CHARACTERISTICS of the objects are ___________
Equal
It is produced when the x-ray beam has sufficient be penetrated the tissue
Diagnostic image
The penetrability of the primary x-ray beam is controlled by ___________
Kilovoltage
It is the controlling factor for contrast on an image
kVp
So it is the original graphic must determine when considering the amount amount of contrast on an image for the most appropriate for the anatomy to be image
Short or long scale of gray
The number of densities from black to white on a radiographic image is an indication of the ___________
Range of the scale of contrast
It describe the number of different densities between black and white on the image
Long – scale and short - scale
The choice of _____________ will NOT affect radiographic contrast
mAs or SID
Low KVP examinations penetrate fewer thickness and have only a few steps between black and white and so produce _____________
Short-scale contrast images
When the primary beam penetrate through tissue with adjacent densities, which have a great differences in contrast, the image is described as
High contrast
A short scale contrast image has fewer steps between black and white, and it is a _____________ image
High contrast image
Low KVP examination produce _____________ contrast images
Short-scale
So this is the preferred scale of contrast with imaging bone anatomy
Short scale contrast images
A zebra is a great example of _____________ because it has black and white stripes
High contrast
Imaging the abdomen requires a _____________ scale of gray
Long
This image will have a fewer differences in contrast Because the differences between adjacent densities are small. And this is referred to as a
Long – scale contrast image
Which has many steps between black and white and is a low contrast image
Long – scale contrast image
Using _____________ will produce more shades of Grey, which will allow for better visualization of abdomen anatomy
higher KVP
I herd of elephants is an excellent example of a _____________ scale
Long gray scale
It is made up of the total amount of contrast acquired from both the subject contrast and film contrast
Radiographic contrast
It is the difference in OD between different areas on the film
Film contrast
It describes the different amounts of exit radiation through different parts parts of the body
Subject contrast
Is the primary controlling factor for a radiographic contrast?
kVp
Is the range of densities the film capable of recording?
Film contrast
Film contrast is represented as the _____________
Slope of the characteristic curve
Four factors with effect film contrast are
1) intensifying screens
2) film density
3) characteristic curve
4) processing
It creates a higher contrast image due to the exposure of light to the film
Intensify screens (IS)
Film density is changed when there is a change in the _____________
Film contrast
There is an _____________ of densities for each film, which allows maximum visualization
Optimum range of densities
Images which have too much or two little densities demonstrate a _____________ in contrast
Decrease
Densities which fall in the toe or shoulder portion, decrease the contrast on the image. the slope of the characteristic curves also affects _____________
Contrast
As the slope becomes steeper, the range of the diagnostic densities become COMPRESSED and the contrast is _____________
INCREASED
Various _____________ factors will affect the amount of contrast on the film
Processing factors
Increasing the amount of time, the film is in the developer, the developer temperature or developer replenishment rate will _____________ the amount of chemical fog on the image
increase
In each of the changes will increase the base fog and _____________ the contrast of the image
DECREASE
It depends on DIFFERENTIAL ABSORPTION of the x-ray beam
Subject contrast
It occurs because different areas of the body have DIFFERENT TRANSMISSION and ATTENUATION effect on the x-ray beam
Differential absorption
Structures in the body that HIGHLY ATTENUATES x-ray photons, such as bone are called as
Radiopaque Structures
The tissues, that only PARTIALLY ATTENUATE x-ray photons and allow a majority of them to be transmitted such as lung are called as
Radiolucent
So this are the factors that affect differential absorption and subject contrast
Thickness of the tissue
The atomic number and type of the tissue
Density of the tissue
kVp setting
Contrast media
Scatter radiation
Kilo voltage
Tissue composition
Contrast medium
Subject contrast
Film type
Direct exposure or intensifying screens
Processing conditions
Film (image receptor) contrast
There is the part of the body that attenuates more x-rays
THICKER parts of the body
An increase of _____________ centimeter in soft tissues thickness decreases the exit radiation by about a factor of _____________
4 CM
Factor of 2
Two parts of the body with different tissue thickness will produce a difference in _____________ contrast
Subject contrast
As body part thickness INCREASES, the amount of attenuation also _____________
INCREASES
When there is little difference in the thickness of adjustment, body parts the subject contrast will be _____________
Decreased
Tissues with HIGHER ATOMIC NUMBERS have GREATER ATTENUATION VALUES than tissues with lower atomic number
True
Bone has a greater attenuation
True
The density of the body parts in _____________ affects the amount of attenuation
grams per cubic centimeter (g/cm3)
Fat has low density than soft tissues so, _____________cm of soft tissues attenuates more than an equal thickness of fat
1cm
It refers to the quantity of matter per unit of volume
Mass density
When the difference in density between adjustment tissue is great, the subject contrast will be _____________(1), and when the differences in density are SMALL, the subject contrast is _____________ (2)
1) INCREASED
2) DECREASED
It controls the energy of the x-ray beam
kVp
_____________-energy x-ray photons have less differential absorption because they are more penetrating
HIGHER ENERGY X-RAY PHOTONS
Higher energy x-ray, photons also produce more _____________ scattering than lower energy x-rays
Compton
The combination of less differential absorption and more scattering results in _____________ subject contrast at HIGHER energies
LESS subject contrast
INCREASING the average energy of the x-ray beam by increasing thekVp or the beam filtration _____________ the subject contrast
LOWER
_____________ It results an x-ray photons with less energy and more differential absorption will occur resulting in _____________ subject contrast
1) LOWER kVp
2) HIGHER subject contras
_____________ it utilizes a lower kvp to INCREASE the subject contrast of the breast tissue
Mammography
By adding this, it serves as adding a higher atomic number to the vessels or organs in the body, which increases the differential absorption and results in body structures becoming more visible.
Contrast agent
This are commonly used as contrast agents because they have high atomic numbers and high densities. (2)
1) iodine
2) barium
Are Radiopaque substances which absorb the x-ray for
Barium and iodine
The INCREASED attenuation makes the structure containing the contrast agent appear LIGHTER than surrounding tissues and_________ subject contrast.
INCREASES SUBJECT CONTRAST
This is also used as a contrast agent where in it increases differential absorption because it’s lower density increases transmission through the air- field structures.
AIR
It is a radioLucent contrast agent, which allows us to visualize long tissue as well as the ribs and mediastenum outline.
AIR
Increases or decreases
Air _________ subject contrast and provides a short scale of contrast to better visualized structure.
INCREASES
Radiograph showing decreased density because of the _________ x-ray beam attenuation by use of a positive contrast agent.
INCREASE
It’s refers to a radiation that has undergone one or more Compton interactions in the body
Scatter
Ask KVP INCREASED, the percentage of Compton interactions _________
Also INCREASES
The presence of scatter _________ radiographic contrast because the scatter INCREASES the film fog, the result in a LONG SCALE OF GRAY.
Reduces
Our devices used to absorb and reduce the scatter before it reaches the film thereby, INCREASING THE CONTRAST.
Grids
This are used when imaging with a high KVP
Grids
LOW KVP imaging does NOT produce the high percentage of Compton interactions and does not require a grid to absorb the scatter before it reaches the film
Remember: LOW KVP DOESNT REQUIRE GRIDS
Factors that influence contrast are
mAs
SID
filtration
beam restrictions
Grids
Collimation
OID
anatomic part
Contrast and processing
It changes the exposure to the image, receptor and density of the image, thereby affecting contrast
mAs
when the exposure is change sufficiently enough to move the film density out of the diagnostic range, whether under exposed or overexposed, the image contrast is ____________
DECREASED
mAs
As the SID changes the intensity of the beam also changes…
..
It governs the amount of change which will occur under the SID
Inverse square law
Greater distances from the image receptor will cause LESS density on the image because the intensity of the beam is diminished resulting in ____________
DECREASED CONTRAST
SID
(Increase or decrease)
Using shorter SID will ____________ contrast. This occurs because the intensity of the beam is greater when the SID is closer to the image receptor
INCREASE
It’s all types will altered the image receptor exposure contrast.
Filtration
Act to absorb the weaker photons that produce a more energetic beam
Filtration
The INCREASED beam energy will cost more and interactions and scatter radiations, both of which will ____________ contrast
DECREASE
Affect contrast as a result of their absorption of scatter radiation that exits the patient.
Radiographic grids
A grid is placed between the ____________ and the ____________
PATIENT and the IMAGE RECEPTOR
Increase or decrease
The effect of less scatter or unwanted density on the image is to ____________ the radiographic contrast
Increase
The more efficient agreed is an absorbing scatter, the____________ it’s effect on radiographic contrast
Greater
It changes in the size of the x-ray field effect the amount of the tissue irradiated
Collimation
The increased amount of scatter radiation, reaching the image receptor results in less radiographic contrast
Collimation
The decreased amount of scatter radiation, reaching the image receptor results in greater geographic contrast
Collimation
Object to image Receptor Distance
When sufficient distance between the object and the image receptor exists an/a ____________ is created preventing the scatter radiation from striking the image receptor.
Air gap
Whenever the amount of scatter radiation Reaching the image receptor is REDUCED, the radiographic contrast is INCREASED
OID (Object-to-Image- Receptor Distances)
