Exam 2 Flashcards
What % change in mAs makes a visible difference in density?
30%
If 5% if an incident beam is transmitted through a body part then 95% of the beam was?
Absorbed, scattered and also attenuated
Principle function of grid
To increase radiographic contrast (because it is reducing scatter
When scatter radiation is removed image ____ improves.
contrast
The ____ protects the emulsion from scratches, pressure and contamination for relatively rough manipulation of x-ray film exposure.
Overcoat
Film that has emulsion coated on both sides is called?
Double Emulsion
Reduction of radiation intensity due to scattering and absorption is called…
Attenuation
Maintaining density when changing from screen to a grid technique
Multiply mAs by the Grid Factor
Patient does is ____ with added filtration?
Reduced
What is a compensating filter?
Shaped aluminum slide into collimator
The ____ is the foundation of radiographic film whose primary purpose is to provide a rigid structure on to which the emulsion can be coated.
Base
When kVp and/or filtration increases, beam quality _____.
increases (filtration lowers PT dose)
What kind of PT requires less radiographic technique and thin but appears to look/be healthy
Hyposthenic
Photon interaction free ____ from the silver & bromide atoms in the silver halide ____..
Electrons Crystal
With exposure to both x-ray and light ____ interactions occur in the emulsion.
photon
A low-contrast emulsion contains ____ silver halide grains that have a wider range of sizes.
Larger
What is AEC?
Automatic Exposure Control Proper density meets multiplier and it terminates
Reduction of radiation intensity due to scattering and absorption is called ____.
Attenuation
What focal spot provides for a shorter exposure time minimizing motion blur?
Large
Base & Emulsion Diagram
Original Base
1869 - Glass Not practical: too heavy, Breakability, Awkwardness in handling
Quantum Mottle refers to? and is a principal contributor to what?
-principal contributor to radiographie noise -random nature by which x-rays interact w/image receptor
The ____ of an x-ray beam is called x-ray quality.
penetrability
If the Grid Ratio increases then OD?
Decreases
What is the relationship in the characteristic curve?
Relationship between OD & Radiation Exposure
Short scale contrast means
Few shades of gray, Low kVp (i.e..extremity x-ray)
Latitude refers to…
The range of exposures over which the IR responds with OD’s in the diagnostically useful range.
Grid Ratio and PT Doe
Higher grid ratio, higher lead content Higher the lead content, higher the exposure factors needed Higher the exposure factors, higher the patient dose
What part of the image formation occurs during exposure?
Latent Image Formation
Grids are constructed with radiopaque ____ and radiolucent ____ materials.
Strips Interspace
The higher the grid ratio the better the ____ which increases ____.
“clean up” which increases radiographic contrast
Tight collimation, low kVp and PT compression increase ____.
contrast
Thicker body parts result in greater ____.
Attenuation
Too long of a scale of contrast what would you do?
Increase kVp by 15% and divide the mAs by half.
If the speed of the IR is doubled; what will you do maintain the density?
The mAs must be halved and no change is required in kVp
Base & Emulsion are two basic components of ____ ____.
Radiographic Film
What type of PT is big & overweight in frame?
Hypersthenic
The ____ has high subject contrast; the ____ has low subject contrast.
Chest Abdomen
If the thickness of the part increases then OD?
Decreases
If you increase kVp then OD?
Increases
Factors affecting film speed.
-Concentration of silver halide crystals -Thickness of emulsion -Shape -Tabular grains: flat providing, more surface area to volume ratio
x-rays transmitted w/out interaction and scattered (or compton interaction) radiation are called ____ ____ ____.
image forming x-rays
How does speed affect detail?
Faster speed results in less detail. Slower speed results in more detail.
Thicker body parts result in greater ____.
Attenuation
What would display the most radiographic density?
Air
Low Noise Accompanies….
Slow image receptors high spatial resolution high contrast resolution
Size of phosphor crystals thickness of phosphor layer and its composition determine screen ____.
characteristics
A x-ray beam that could pass through ____ tissue would have high penetrability & quality.
dense
Latitude and Contrast are ____ ____ and wide latitude means the mAs can what?
Inversely Proportional and mAs can vary more and still produce a diagnostic image.
True or False: The use of radiographic intensifying screens with film allows reduced technique and therefore reduced PT dose. However, the image is more blurred than it would be after exposure without screen.
True
Variable collimators are the most commonly used ____ ____ ____.
beam restricting device
____ focal spot size is reserved for fine-detail radiography, in which the quantity of x-rays is relatively low.
Small
If the IR speed increases then OD?
Increases
How does Quantum Mottle appear on the image?
Quantum Mottle has a grainy appearance associated with using a low # of x-rays to produce
Main disadvantage of crossed grid
grid cut-off (orthopedic work)
Why is it important to keep exposure time as sure as possible?
To minimize motion blur
Why does an x-ray tube have 2 focal spot sizes?
Small Focal Spot - improves spatial resolution of high-contrast anatomy Large Focal Spot - useful when a high-intensity x-ray beam is required for thick anatomy.
To produce a long scale of contrast, a technologist would set a technique as follows
High kVp & High mAs
A ____ material emits light for a period of time after stimulation.
Phosphorescent
Tight collimation lowering kVp & PT compression increase ____.
contrast
What is the key when using a machine with AEC?
Positioning
What is inherent filtration?
-glass or metal envelope of x-ray tube -variable-aperture light-localizing collimator
Linear or Parallel Grid cleans scatter ….
in one direction - only transverse - across long axis of grid
High quality radiograph
faithfully reproduces structure and tissue
What is large focal-spot?
-generally used -assures sufficient mAs can be used thick dense part -shorter exposure: minimizes motion blur
Primary control for contrast is ____.
kVp (as kVp increases both quantity and quality of x-radiation increases so a higher portion of the primary beam reaches the image receptor)
Primary Control of contrast is ____.
kVp
Crossed Grid
Cleans up both directions of grid
What is contrast resolution?
The ability to distinguish anatomic structures of similar subject contrast.
What influences image receptor (film) contrast?
-contrast medium -thickness -atomic #
Gelatin makes up the ____ of protective covering on radiographic film.
overcoat
Grid Ratio
Height of grid strip divided by thickness of interspace material. H/D
General size & shape of a PT is referred to as?
Body Habitus
____ filters are shapes of Al mounted onto a transparent panel that slides in the grooves beneath the collimator?
compensating filter
The formation of the latent image is sometimes called the ____ effect.
Photographic
Name 3 common factors that determine amount of scatter absorbed with a grid.
-Angle of scattered photons -Height of grid strips & width H/D -Interspace Material
Attenuation
Reduction in x-ray intensity that results from absorption & scattering
Types of secondary radiation (2)
Scatter Radiation Leakage Radiation
The least dense body tissue is…
Fat
What is differential absorption?
Different degrees of absorption in different tissues that result in image contrast and formation of the x-ray image.
What subject factors attenuate the x-ray?
Chunky Parts & Parts with High Atomic Number (chunky + high atomic # = no remnant x-rays on the IR)
Film Contrast
characteristic inherent in film itself to emphasize high for low contrast imaging
When radiograph is over penetrated what happens?
Trabecular “burned out”
True our False kVp is the most important influence of film contrast.
True
Fast Image Receptors have…
High Noise Low Spatial Resolution Low Contrast Resolution
A radiographic can be adequately penetrated yet….
still be under or overexposed
How many components does radiographic noise have and what are their names?
4 components: film graininess structure mottle quantum mottle scatter radiation
Speed, contrast and sensitivity of screen film is determined by what 3 factors?
size, shape and distribution of silver halide crystals
If you increase SID then OD?
Decreases
Air gap technique
for trauma scatter goes in opposite direction
Grid surface x-ray absorption formula
% x-ray absorption width of grid strip / width of grid strip + width of grid interspace x 100
Properly exposed radiographs take place where? (Amounts?)
Straight Line Portion *Intermediate Levels 0.25 to 2.5 (a bit higher for mammo.)
Image Quality
The fidelity with which the anatomical structure that is being examined is rendered on the radiograph.
Density can be measured using a ____.
Densitometer
SHALL
Short Scale High contrast (low kVp B&W) Long scale Low contrast (high kVp Gray)
When mAs increases ____ increases
density
Cellulose Triacetate
-Same characteristics, not as flammable -Did not store well for long periods -Fire resistant, when burned releases nitrogen dioxide, a poisonous gas
Safelight
Red can be used for green or blue sensitive film.
The most dense body tissue is…
Bone
Short scale of contrast means you would?
decrease kVp 15% & double the mAs
The ____ layer adds to the light efficiency of intensifying screens.
Reflective
____ makes anatomy more visible.
Contrast
Cellulose Nitrate
-1st lightweight base -Developed WWI -Extremely flammable -Hospital fire’s -1930 cleveland hospital (150 ppl killed started in storage area
If the developing time increases then OD?
Increases
What is the velocity of all electromagnetic radiation?
3 x 10-8 m/s
____ ____ holds the silver halide crystals.
Gelatin Emulsion
2 terms that can be used for spatial resolution
Detail & Recorded Detail
Grid Frequency
of grid strips or lines per inch
When kVp increases ____ increases
density
What is attenuation?
Reduction in energy of beam.
Advantages of moving grids
blurs out grid lines; moves fast enough to clean page w/out lines on image
A high-contrast emulsion contains ____ silver halide grains with a relatively uniform grain size.
Smaller
Factors that affect film contrast
-silver halide crystals size shape and distribution -High Contrast Emulsion: Small crystals, uniform size -Low Contrast Emulsion: Large crystals, wider range of sizes (shades of gray)
Beam quality is measured by ____ ____ ____.
Half Value Layer/Filtration
Size of phosphor crystals, thickness of phosphor layer & its composition determine screen ____.
characteristics
Radiographic Contrast is a product of what 2 factors.
Image Receptor Contrast Subject Contrast
Name the factors that control/affect detail?
Film Speed Focal Spot Size SID OID Motion Distortion
Grid use increases ____ and decreases.
unwanted, non-diagnostic density contrast
Variable collimators are the most commonly used?
Beam Restricting Device
Do filters have an affect on density?
Yes, it filters out the low energy photon therefore density is increased.
Focusing distance is associated with which of the following?
Grids (Focusing distance or Focal Range is used to specify optimal OD)
Formula for maintaining density from one grid to another
old mAs/new mAs = oldGF/newGF
Film Resolution
-ability to image an object faithfully -measured in line pairs per mm
____ contrast film contains smaller crystals of uniform size.
High
Positive Beam Limiting
Feature of radiographic collimators that automatically adjusts the radiation field to the size of the image receptor.
Unexposed x-ray film that has been processed appears _____ and easily transmits _____ but not _____.
Lucent Light Not Images
Speed
Ability of an image receptor to respond to low x-ray exposure.
High kVp/mAs produces
low contrast long scale, many shades gray wide latitude
A parallel grid’s main disadvantage is ____.
Grid cut-off
The thicker the PT the more x-radiation is required to penetrate the PT exposure and for this reason the Rad Tech. must use ____ to measure the thickness.
Calipers
An ____ ____ is an example of both luminescence & fluorescence.
Intensifying screen
Sensitometry
Study of the relationship between the: -intensity of exposure of the film and the -blackness after processing
Image with high number of x-rays will have ____ quantum mottle.
Lower
How does beam limitation affect density?
It reduces the density and the amount of scatter.
Use of collimation ____ contrast and ____ PT dose.
improves reduces
The only x-rays transmitted through a grid are those ……
traveling in the direction of the interspace. X-rays scattered obliquely through the interspace are absorbed.
What happens to PT dose when kVp is increased?
It is reduced
Subject (PT) Factors
Selection of radiographic technique that properly compensates for PT’s size, shape and tissue composition.
Speed, contrast and sensitivity of screen-film is determined by what 3 factors?
The size, shape and distribution of silver halide crystals.
Aluminum or plastic make up the ____ in grids.
Interspace material
What is added filtration?
Inserted into the collimator.
When scatter radiation is removed image ____ improves.
contrast
Lowering kVp ____ PT dose and image contrast.
will increase
____ is the sensitivity of the screen-film combo to x-rays and light.
Speed
What are the two main parts of sensitometry used to describe characteristic curve?
1.) Exposure to the film. 2.) % of light transmitted through the processed film
The purpose of a filter is to ____ ____ ____.
Reduce PT Dose
Focal-Spot sizes and values
Small 0.5mm, 0.6mm Large 1.0mm, 1.3mm
Biggest enemy of radiographic contrast is?
Scatter or Fog
Grid cleans up what?
scatter
Grids are constricted with radiopaque ____ & radiolucent ___ materials.
Radiopaque Strips Radiolucent Interspace
Gelatin makes up the ____ of protective covering on Radiograph film.
overcoat
A radiograph that has small differences in OD are ____ ____ radiographs.
low contrast
If you increase mAs then OD?
Increases
Manifest Image
Processed image (aka latent image)
Contrast Resolution
Ability to distinguish anatomical structures of similar subject contrast ie. Liver/Spleen or Gray Matter/White Matter
Less Grid Frequency translate to
more distinct grid lines on film
When OD is out side the diagnostic range what is lost? and why?
Contrast, because the image is in the “Toe” or “Shoulder” of the characteristic curve.
A term borrowed from electrical engineering is called…
noise
Resolution
The ability to image 2 separate objects and visually distinguish one from the other.
If the Mass Density increases then the OD?
Decreases
Radiographic Contrast = ____ x ____
Image Receptor Contrast x Subject Contrast
Screens Spectral Matching
-Calcium Tungstate emits blue or blue violet -Exposed w/ silver halide film -Rare earth - green sensitive film (orthochromatic film) -Colors not matched: speed of system greatly reduced increased PT dose
Phosphorescence
Phosphor continues to emit light after stimulation.
Which of the following is most likely to result from the intro. of a grid to a particular exam?
Increased PT does and Increased Contrast
Contrast is the degree of difference in ____ between areas of an image.
Optical Density
What factors the visibility of detail?
Image contrast and Optical density
Image with low number of x-rays will have ____ quantum mottle.
Higher
An x-ray beam that could pass through ____ tissue would have high penetrability & quality.
dense
Name 2 important characteristics of radiographic film base.
lucency dimensional stability
High Spatial Resolution and High Contrast Resolution require?
Low Noise and Slow Image Receptors
In the 1950’s a stronger and thinner film base was introduced. What material was this film base made of?
Polyester
What improves as screen blur decreases, motion blur decreases and geometric blur decreases?
Spatial Resolution
____ are designed to remove scattered x-rays before they reach the IR?
Grids
Rule for Grid Use
Use for parts 8cm and up smaller? no grid larger? grid shoulder or knee optional
4 Subject Factors for OD & Contrast
Thickness of the part Density of the part Atomic # of the part Motion
What is between the emulsion and the base of radiographic film that holds it together during the process?
Adhesive Layer
The body tissue with the highest absorption…
Bone
An ____ ____ is an example of both luminescence and fluorescence,
Intensifying screen
An increase of 15% in kVp is equivalent to increasing mAs by ____.
Double (100% increase)
Focused grid is designed to
minimize grid cut-off
Film base can maintain its size and shape during use and processing so that it doesn’t contribute to image distortion. This characteristic is best defined as ____ stability.
Dimensional
A radiograph can be under or over penetrated yet still…
have adequate density
Quantum mottle is similar to the ____.
sowing seeds of grass
Latent Image
Unprocessed but exposed (photoelectric effect)
Grid strips height divided by width (distance) of interspace determines ____ ____.
Grid Ratio
What is small focal-spot size for?
Fine Detail (x-ray quantity low)
mAs =
of photons
____ ____ holds the silver halide crystals.
Gelatin Emulsion
True or False
High contrast is also known as a short scale of contrast, which produces an image composed with more B&W’s and not as many shades of gray.
True
What when raised increases the penetrating quality of the central ray?
Filtration and kVp (Both)
Photons interactions free ____ from the silver and bromide atoms in the silver halide ____.
electrons crystal
Exposed processed x-ray film can be ____.
Opaque
What focal spot provides for a shorter exposure time minimizing motion blur?
Large
x-rays transmitted without interaction & scatter (or compton interaction) radiation care called ____.
Image forming x-rays
Film Contrast
Characteristic inherent in film itself to emphasize high or low contrast imaging.
Disadvantages of moving grids
bulky, complicated subject to failure increases OFD poor design can cause motion longer minimum exposure time advantages outweigh disadvantages
Most x-ray tubes are equipped with two?
focal spots sizes
After photons interact releasing negatively charged e where do these e migrate to?
Sensitivity Center
Contrast
Differences in Optical Density (degree of diff btw the light and dark areas of a radiograph)
Name two important characteristics of radiographic film base.
lucency & dimensional stability
When an image is under penetrated what happens?
Trabeculae “whited out”
Because of the anode heel affect density is less @ which end of the x-ray beam?
Anode
Radiographic Contrast is the product of ____ contrast & ____ contrast.
Image Receptor Subject
2 basic parts of Radiographic Film
Base and Emulsion
PT does is increased with a ____ in kVp.
Decrease
The effects described as differential absorption are?
1) Responsible for radiographic contrast 2) Result of attenuating char. of tissue. 3) Minimized by using High kVp
The ____ of an x-ray beam is called x-ray quality. (HVL decrease total # of x-rays)
penetrability
Properly exposed film appears ____ and heavily exposed film appears ____.
with various shades of gray black
A radiograph that has marked differences in OD is a ____ ____ radiograph.
high contrast
To produce a long scale of contrast, a technologist would set a technique as follows:
High kVp and High mAs
Speed of the image receptor is ____ but it very much influences ____.
Not apparent on the radiographic image Resolution and Noise
Factors Affecting Film Speed
-Thickness of the emulsion -Concentration of Silver Halide Crystals -Shape–>used to be fate 3 dimensional then changed to–> -Tabular Grains -flat providing more surface area and volume ratio
What controls PT radiation dose?
mA (or x-ray quantity)
High spatial resolution and high contrast resolution require?
Low Noise & Slow Image Receptors
Off-Level Grid
Grid not perp. to CR x-rays abnormally angulated grid cut-off across entire radiograph reduced density
kVp is the primary control of ____ & ____
x-ray beam quality and beam penetrability
A technologist is standing next to a portable examination of the abdomen at 50” and receives 3rem. The image is of poor quality and the technologist must return to repeat the exam. This time he stands at 70” what is the rem now?
I1/I2 = (D2/D1)2
3/x = (70/50)2
3/x = 4900/2500
4900x = 7500
x = 7500/4900
x = 1.53 rem
The emulsion consists of a homogenous mixture of ____ & ____.`
Gelatin and Silver Halide Crystals
One difference between large & small focal spots is the _____?
capacity to produce x-rays
Name 3 common factors that determine amount of scatter absorbed with a grid.
Angle of scattered photons. Height of grid strips. Width of interspace material.
Almost 99% of latent image is created by ____ from the screens.
Light
Velocity of Light is constant and symbolized?
3 x 10-8 m/s
When raised ____ & ____ increases the penetrating quality of the central ray.
Filtration & kVp
What part of the image formation occurs during exposure?
Latent Image Formation
Grid Material
Lead
Developing stage
stage of processing during which the latent image is converted to a manifest or visible image
What is the primary controlling factor for contrast?
kVp
mAs controls
Optical Density
Polyester
-Introduced in 1950 -Thinner, stronger, more fire resistant, less toxic -Stronger than cellulose triacetate -Stands up to processing, handling, and storage better
Silver bromide and silver iodide make up the ____ in film emulsion.
Crystals Bromide 98% Iodide 2%
Grid Purpose
-designed to transmit x-rays whose direction if on line from source (primary) -x-rays at an angle (scattered) are absorbed by grid materials -decreases scatter to the film -principle function to increase radiographic contrast
Radiographic noise is …
the random fluctuation in the OD of the image
What effect does doubling the SID have on density?
Density will be reduced by 1/4
Subject Contrast
Determined by the size, shape and x-ray attenuating characteristics of the anatomy being examined & energy (kVp)
On a focused grid grid strips are placed
at angle = primary beam
____ contrast film contains smaller crystals of uniform size.
High
If the collimation increases then OD?
Decreases
Radiographic Film contains OD’s that range from ____ to ____.
0 Clear/Lucent (unexposed/ processed film transmits light not images) 4 Black/Opaque (processed exposed)
kVp & mAs directly affect
density
What is the most common error when grid cut off appears across the image?
grid is off-level
Together the filtering effect of the x-ray tube’s glass envelope and its oil coolant are referred to as? (3 forms)
Inherent Filtration (.5 mm Al) Added Filtration (1 mm Al) Compensating Filtration (1 mm Al) (2.5 mm Al)
How does kVp relate to differential absorption?
Higher kVp will allow more photons to transfer through.
What has the greatest effect on contrast?
kVp
Grid Covering
thin aluminum casing
Primary control of OD is ____.
mAs (as mAs increases radiation quantity increases therefore the # of x-rays @ the image receptor increases for higher OD)
Main disadvantage of parallel grid
grid cut-off (have to use correct SID)
4 Film Factors
-Density or OD -Contrast (depends on kVp) -Speed (film screen mostly) -Latitude
How does filtration affect the primary beam?
It increases the average energy of the primary beam.
Silver Bromide & Silver Iodide make up the ____ in film emulsion.
Silver Halide Crystals
Types of moving grid mechanisms include (2)
Reciprocating and Oscillating
____ are designed to remove scattered x-rays B4 they reach the IR.
Grids
The ____ beam refers to the x-rays that remain as the useful beam exits the PT. It consists of x-rays scattered away from the IR and image forming IR.
Exit
Sthenic
Strong or Active
With exposure to both x-ray & light ____ interaction occurs on the emulsion?
Photon
Spatial Resolution
Ability to image small objects that have high subject contrast (bone-soft tissue interface)
Examples of Low, Moderate and High Contrast
Low - Abdomen Moderate - Elbow (Fat Pads) High - Hand
What recess motion blur?
short exposure time
____ is the most critical consideration when using a crossed grid.
alignment
If the x-ray is totally absorbed its interaction is ____.
Photoelectric
Because of WWI something needed to change in the acquisition of images in diagnostic imaging ____.
Radiographic Film was developed
Most important characteristics of radiographic image quality are?
Spatial Resolution Contrast Resolution Noise Artifacts
Contrast is the degree of difference in ____ ____ between areas of an image.
Optical Density
A group of atomic silver is called a?
Latent Image Center
3 types of x-ray filtration are?
Inherent Added Compensating 2.5mm Al
OD has a ____ ____ ____ that can be calculated if?
Precise Numeric Value If the level of light incident on a processed ilm and the level of light transmitted through that film are measured
Beam quality is affected by____.
kvP and Filtration
The degree of blackening of the x-ray image is ____.
Density
Base & emulsion are 2 basic components of ____.
Radiographic Film
Latitude can be thought of as…
the margin of error for technical factors
A ____ material emits light for a period of time after stimulation.
phosphorescent
In the toe and shoulder of characteristic curve large variations in ____ result in a small change to ____.
exposure OD
Aluminum or plastic make-up the ____ in grids.
Interspace Material
Fluorescence
Visible Light is only emitted while the phosphor is stimulated.
kVp in relation to density is not…
linear
Grid strips height divided by width (distance) of interspace material determines ____.
Grid Ratio
How does kVp control OD?
Helps determine the # of x-rays (in the image forming beam) hence the average OD
____ is the material with which x-rays or light photons from intensifying screens interact and transfer information.
Emulsion
The image forming x-rays include those which have been…
remnant and scatter
What happens to PT does when kVp is increased?
Reduced
Spatial Resolution improves as….does what?
Motion, Screen, Geometric blur DECREASE
On a focused grid grid strips are placed
at angle = primary beam
Thermionic Emission at the filament creates a?
space charge
Almost 99% of latent image is created by ____ from the screen.
Light
Emulsion is enclosed by a protective covering of gelatin called ____.
Overcoat
PT dose is ____ w/ added filtration
Reduced
Biggest enemy of Radiographic Contrast?
Scatter or Fog
When kVp and/or filtration increases beam quality ____.
increases
The ____ layer adds to the light emitting efficiency of intensifying screens.
Reflective
What is the controlling factor of density?
mAs
Image Receptor Contrast
Inherent in the screen-film combo. and is influenced somewhat by processing of the film.
When the grid frequency is higher it….
allows more to be captured
High kVp results in reduced ____ ____
image contrast
Grid interspace material can be made of ____ or ____.
Plastic (most often) Aluminum
____ ensures the x-ray beam is collimated to the IR size.
Positive beam limiting device
True or False The size and concentration of silver halide crystals primarily affect film speed.
True
____ makes up the base of radiographic film.
polyester
The ____ principle function is to provide mechanical support for silver halide crystals by holding them uniformly dispersed in place.
Gelatin’s
Which grid ratio is generally for portable is
6:1
