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799 Cards in this Set

  • Front
  • Back
What is electromagnetic radiation?
the propagation of energy thru space as oscillating electromagnetic fields.
What are the physical characteristics of electromagnetic radiation?
mass = 0
charge = 0
speed = c (speed of light)
What is the shorthand abbreviation of electromagnetic?
em
What are 6 examples of electromagnetic radiation?
radio waves
infrared
visible light
ultraviolet light
x-rays
γ-rays
How is wavelength related to photon energy?
inversely: the smaller the wavelength, the higher the energy of the photon and vice versa.
Which types of electromagnetic radiation have the highest photon energy?
x-rays and γ-rays
Which type of electromagnetic radiation has the lowest photon energy?
radiowaves
List the 6 types of em radiation from longest wavelength to shortest wavelength.
radiowaves
infrared
visible
ultraviolet
x-rays & γ-rays
How is em frequency related to em wavelength?
Inversely: the higher the frequency, the shorter the wavelength and vice versa.
How do you read:

E ∝ 1/λ
energy is inversely related to wavelength
What is ionizing radiation?
radiations that have sufficient energy to cause ionization of the medium thru which they pass.
What type of radiation is of concern in radiation biology, therapy, and safety?
ionizing radiation
What are the two categories of ionizing radiation?
particulate
electromagnetic
What is particulate ionizing radiation?
both α and β particles
What are two physical attributes of α and β particles?
they both have mass and charge
What are 3 kinds of electromagnetic ionizing radiation?
x-rays, γ-rays, and uv rays
Is all electromagnetic radiation ionizing?
No, just the em radiation that has higher energy
What is the difference between x-rays and γ-rays?
x-rays originate from outside the nucleus by interaction of high speed particles.
γ-rays originate from within the nucleus of spontaneously decaying atoms
In an x-ray tube, what are the high speed particles that produce x-rays?
electrons
What is required in order to produce x-rays in an x-ray tube?
A source of electrons,
a method to accelerate the electrons to high speed,
and interaction of the electrons with a target
What are the basic components of an x-ray tube?
target
filament
glass tube
cathode
anode
What is a filament?
a thin coild wire that serves as the source of electrons in an x-ray tube.
What is a filament made of?
Tungsten
What are two features that a filament must have?
It must provide a large number of electrons
It must be able to withstand high temperatures (high melting point)
Is the filament part of the cathode or anode assembly of the x-ray tube?
cathode
Is the cathode negative or positive relative to the anode?
The cathode is negatively charged relative to the anode.
What is thermionic emission?
The process by which electrons are produced
What is involved in thermionic emission?
a low voltage current is forced thru the filament, generating heat. Heat overcomes a Work Function and results in the release of free electrons as a cloud around the filament.
What keeps the electron cloud produced by thermionic emission from dispersing?
a negatively charged focusing cup
How are electrons accelerated in an x-ray tube?
A high potential difference is applied across the tube.
What is the definition of voltage?
potential difference
What causes electrons to travel from the filament to the target?
The negatively charged electrons are attracted to the positively charged target
Is the anode positively or negatively charged?
positive
What component of the x-ray tube does the anode contain?
The target
Is the potential difference applied to every x-ray tube the same?
No, it varies with the type and capabilities of the equipment.
What is the diagnostic range of potential difference?
40-140 kVp
What is the therapeutic range of potential difference?
MV
Where does interaction of electrons occur w/in an x-ray tube?
At the target
What is the focal spot?
A small area of the target where electrons actually interact.
Why must a tube have a vacuum environment?
To prevent incidental interaction between the electron beam with air atoms.
What is the housing of an x-ray tube made of?
glass (Pyrex)
What is the whole x-ray tube enclosed within?
Lead shielding
From the target, what is the direction of x-rays?
All directions
What feature of the x-ray tube allows the exit of an x-ray beam?
window
What are the 2 processes by which electrons interact within a target to produce x-rays?
Transition
Bremststrahlung
What type of x-rays do "transition" electron interactions produce?
x-rays of a very specific energy range
(specific)
What types of x-rays do Bremsstrahlung electron interactions produce?
x-rays over a broad energy range (general)
Do all the x-rays produced by an x-ray tube have the same amount of energy?
No, an x-ray beam is composed of both characteristic and general x-rays and is thus composed of x-rays that cover a spectrum of energies (wavelengths)
Is x-ray production an efficient process?
No, not really.
What are the primary reasons that x-ray tubes fairly inefficient?
Excitation: many of the electron interactions result in excitation of the target atoms rather than x-ray production.
Bremsstrahlung: The energy spectrum associated with general x-rays includes em radiation that is below the x-ray energy range.
What are the consequences of x-ray tube inefficiency?
99% of incoming electron energy is actually converted to heat.
1% of incoming electron energy is converted to x-rays
What is the major limiting factor in x-ray production, tube design, construction, and use?
Heat production/dissipation
What is contrast?
the degree of blackness on a radiograph
What is the radiographic gray scale?
The range of differences seen in film blackness that are present on a radiograph
whal is a long gray scale?
A radiograph with a large number of shades of gray
what is latitude?
A radiograph with numerous shades of film blackness.
How is "degree of blackness" measured?
in terms of optical density; can be assigned a numerical value
As the spectrum moves from white, through multiple shades of gray to black the optical density __________.
increases
T/F: A high contrast film will have many shades of gray.
False: A high contrast film will have few shades of gray.
T/F: A long latitude film will show many shades of gray.
True
What is fog?
extraneous film exposure that is superimposed over the image.
Fog causes a __________ in overall radiographic contrast.
decrease
What are 3 causes of fog?
1. scatter radiation
2. safelight mismatch
3. chemical fogging
When does fog caused by safelight mismatching occur?
during processing, after the image has been made.
When and how does chemical fogging occur?
during development of the radiograph:
- excessive developer temps/times
- improper solution concentrations
What are 2 potential causes of artifacts?
1. Pressure (e.g. bending film before developing causes focal exposure of the film)
2. static electricity: causes linear/branching black streaks across film.
What is subject contrast a result of?
Differential absorption of x-rays by the various tissues of the body.
What are 3 tissue characteristics that determine subject contrast?
1. density of tissue
2. tissue thickness
3. anatomic number (Z)
What are the 5 basic subject densities?
1. air
2. fat
3. soft tissue
4. bone
5. metal
Which subject density absorbs the least amount of radiation?
air
Which subject density absorbs the largest amount of radiation?
metal
What is the line focus principle?
Has to do with the target angle and the actual vs. effective spot.
but what exactly is it?
What is the difference between the actual focal spot and the effective focal spot?
The effective focal spot is the apparent size of the actual focal spot as is viewed by the patient.
What is a benefit and consequence of a larger actual focal spot?
benefit: greater x-ray output capability
con: less detail is visible
What is a benefit and consequence of a smaller actual focal spot?
benefit: enhanced detail visible
con: the target absorbs more of the primary x-ray beam, decreasing the x-ray output capability
Why is design of the anode important?
It significantly relates to output capabilities of the tube and cost of the equipment.
What are the 2 types of anodes?
1. stationary
2. rotating
Describe stationary anodes
basically small, fixed targets embedded in the end of a fixed metal rod
What are the limits of stationary anodes?
-Heat must be transferred directly from the target thru the anode assembly before it can dissipate externally.
-x-ray output is limited b/c of limited heat dissipation
What are the uses of stationary anodes?
-highly portable (more lightweight)
-radiation therapy: number of x-rays in the beam is less important and supplemental cooling is possible.
This is a high speed, rotating disc. The filament is offset and "aimed" at the periphery of the disc.
Rotating anode
Benefits of rotating anodes
-much greater capability to dissipate heat
-x-ray output can be much greater
uses of rotating anodes
where greater output is important;
may be fixed diagnostic, low portability diagnostic, or special procedures
How many filaments do most rotating anode tubes have? Why?
2 to allow/generate a small and a large focal spot.
In dual focal spot tubes, what does a smaller focal spot provide?
more detail/resolution
In dual focal spot tubes, which focal spot is used for most routine work?
the larger focal spot.
How does the target angle affect the size of the actual focal spot?
As the angle from the perpendicular (patient) increases, the actual focal spot decreases in size.
How does the target angle affect the size of the effective focal spot?
As the angle from the perpendicular (patient) increases, the effective focal spot increases in size.
What are 2 characteristics of the x-ray beam that are significant and controllable?
1. quantity
2. quality
In terms of x-ray beam characteristics, what does quantity refer to?
the number of x-rays within the beam
In terms of x-ray beam characteristics, what does quality refer to?
the energy of the x-rays within the beam
How does penetrability relate to x-ray beam quality?
Higher energy x-rays can penetrate thicker or more dense objects.
What is electron energy determined by?
tube voltage (kV)
What does the kVp selector do?
changes the voltage difference (potential) across the x-ray tube.
Where is the kVp selector found?
on the control panel
Explain how increasing the kVp on the control panel changes the image seen on a radiograph.
Increasing the kVp increases the voltage across the tube, which increases the energy of the electrons transversing the tube. Higher energy electrons strike the target with more energy and generate higher energy x-rays. Higher energy x-rays can penetrate thicker or more dense objects. More penetration creates a darker image.
What two factors control quantity of x-rays within the beam?
1. # of electrons
2. # of interactions per electron
How are the number of interactions per electron determined?
The energy of the electrons, which is controlled by the kV.
What are the number of electrons determined by?
-The number of electrons emitted from the filament. This is determined by the current (I in mA) through the filament, which is controlled by the mA selector on the control panel.
-The length of time electrons flow across the tube, which is controlled by the exposure timer on the control panel.
The _______ selector controls the peak magnitude of the high voltage across the tube.
kVp
The _______ _______ controls the time that high voltage is applied to the tube.
exposure timer
The ________ selector controls the current thru the filament.
mA selector
This refers to the quantity of x-rays within the beam.
mAs
How is mAs calculated?
It's the mathematical product of the filament current (mA) and the exposure time (seconds).
How many mAs are there if the filament current is 300mA and the exposure time is 1/30sec?
10mAs
How many mAs are there if the filament current is 100mA and the exposure time is 1/10sec?
10mAs.
This controls/affects the quantity or intensity of the x-ray beam.
mAs
This controls/affects primarily the quality of the x-ray beam, but also affects quantity.
kVp
What 7 controls are included in an x-ray machine control panel?
1. On-off switch
2. Line Voltage Comp (+/-)
3. kVp selector
4. mA selecto
5. exposure timer(s)
6.mAs selector
7. mA Meter (+/-)
What does the line voltage comp on an x-ray machine control panel do?
Adjusts the machine to match/standardize the incoming power supply. This must be adjusted in less sophisticated equipment. It is accomplished automatically in more sophisticated equipment.
How is a mAs selector different from a mA selector?
mA selects for the amount of current going through the filament.
mAs replaces both the mA selector and the exposure timer. Instead, the machine automatically sets the maximum mA and shortest exposure time for the kVp selected.
What does an mA meter do?
It documents the current flow during an exposure.
This is filtration by the glass in the x-ray tube and the surrounding oil
inherent filtration
This is filtration by intentionally added metal
Added filtration
What is included in the total filtration of an x-ray beam?
both inherent and added filtration
What does filtration do?
It selectively absorbs more of the lower-energy x-ray photons.
What absorbs low energy x-rays?
filters and patients
Why do filters produce cleaner images?
They absorb lower energy x-ray photons that tend to scatter more.
What does a collimator do?
restricts the x-ray beam to a confined region.
Where are collimators located?
outside the tube housing and can be in the shape of a diaphragm or cone
t/f: collimation of the x-ray beam may be adjustable.
True, if the collimator has adjustable filters, collimation is adjustable.
How can you reduce the VOLUME of patient tissue that is irradiated?
Use a collimator
What does proper collimation do to contrast?
improves it
What are Light Beam Collimators
A light that shows the area of exposure that a collimator will allow to the patient
Which radiographs should show evidence of collimation?
every exposed film
How does scatter radiation affect image quality?
It reduces image quality by decreasing image contrast.
How do collimators improve image contrast?
They reduce scatter radiation that would otherwise decrease image contrast.
Where are grids typically located?
below the table top of the x-ray unit.
What do grids do?
They absorb scatter radiation before it reaches the film
How is scatter radiation produced?
it is the result of Compton interactions of x-rays with matter. When these interactions occur, x-ray photons are deflected in different directions.
The _______ the body part, the _______ the chance of a photon being scattered.
thicker, greater
When should a grid be used?
With any tissue greater than 10cm thick.
What are grids composed of?
hundreds of alternating lead strips separated by either aluminum (best) or fiber interspace material.
Why is the grid enclosed in a protective cover?
to provide strength and durability.
The lead strips in a ________ focused grid are ________ to be in alignment with the ________ path of x-ray photons.
focused, angled, path
When grids are used, _______ x-rays are needed.
more
To increase the number of x-ray photons when a grid is used, what should be increased?
mAs
How can mAs be increased?
Increase either kVp or exposure time
Why is alignment of the grid critical?
Because the interspace material is matched to the divergent path of the x-ray beam. (Primary radiation penetrates the interspace material and exposes the film.)
What are 4 ways that grids can be misaligned?
1. inverted grid
2. tilted grid
3. grid too close to x-ray tube
4. lateral decentering
What does grid cut-off result from?
An improperly aligned grid.
What does grid cut-off look like?
An underexposed image with misaligned grid lines
Name 2 grid misalignments that result in the same cut-off appearance.
1. grid too close to tube & inverted grid
OR
2. tilted grid & lateral decentering
Define grid ration
height (h) of grid strip divided by thickness (width) of interspace material (D)
Which grid is more effective at cleaning up scatter, high-ratio or low-ratio?
high-ratio
What is a "bucky tray"?
A mechanism that will move the grid during an exposure that causes the lines of the grid to be blurred and therefore, not seen on the radiographic image.
What are the best quality grids and when used, can the grid be seen on the radiograph image?
best quality: 103 lines/inch
benefit: the strips are so thin, the lines are barely noticeable on the radiograph
These are rigid, light-tight devices that hold the x-ray film in contact with the intensifying screen.
cassettes
What is the function of screens?
to convert x-rays to visible light
What exposes radiograph film?
visible light
Why are screens used?
It is more efficient to expose film with visible light than x-rays, so there is a marked reduction in the amount of radiation needed to make an exposure when a screen is used.
Where are screens located?
on the inside covers of the cassette
How many screens do most cassettes have?
2, one for each side of the film
T/F: screens must be held in tight contact with the film.
True
what is the mechanism by which screens convert x-rays to visible light?
The x-ray photon will strike a phosphor crystal in the screen. The excited phosphor will then emit a specific wavelength of light that exposes the film.
From the tube side, what layers separate the x-ray beam from the film?
-cassette
-screen w/ phosphor layer
-film
How does the thickness of the screen affect the radiographic image?
The thicker the screen, the more light is diffused and the lesser the resolution of the image.
How are detail and sensitivity related in the context of screens?
inversely
________ detail screens require larger amounts of radiation to give adequate exposure.
high
What designates the sensitivity of a screen?
its speed
The higher the speed the _______ the sensitivity of a screen.
greater
The higher the speed the _______ the detail of a screen.
lesser
As efficiency of a screen increases, resolution _______
decreases
Your technique using a 200 speed cassette is 10 mAs. You are changing to a 400 speed cassette. What is your new mAs?
=10mAs x 200/400
=5 mAs
check: mAs must decrease to keep resolution the same as the speed increases.
Your technique using a 800 speed cassette is 2.5mAs. You are changing to a 100 speed cassette. What is your new mAs?
=2.5mAs x 800/100
=2.5 x 8
=20mAs
check: mAs must increase to account for lower resolution provided by screen speed.
Which screen provides better detail, 100 or 200 speed?
100 speed
What speed screens are used for orthopedic radiology and imaging birds and reptiles?
low speed
Which speed cassettes are often used for routine work such as thorax and abdomen?
200-400 speed
If your x-ray machine is of low output (low mA), then would you select a high or low screen system? Why?
high speed b/c it requires less radiation to make exposures
Increased detail can be achieved by using a ______ emulsion film and a ______ screen cassette.
single, single
A single screen cassette and a single emulsion film will generally require ______ as much exposure as a double screened cassette/double emulsion film.
twice
what is the advantage of a single screen system?
better detail
Which elements do most current intensifying screen phosphors contain?
one of the following:
Yttrium Tantalate,
Barium - Blue,
Lanthanum - Blue,
Gadolinium -Green,
Calcium Tungsten - Blue
The different elements of screen phosphors will produce different ______ light. It is important that the film is __________ to the _____ light emitted by the screens.
color, sensitive, color
What is "spectral matching"?
Matching the color sensitivity of the film to the color produced by the phosphore element.
What is emulsion composed of?
grossly: a gelatin material embedded within a layer of silver halide crystals.
microscopic crystals: 95% silver bromide, 5% silver iodide, the crystals are flat and triangular (~1um on a side).
what happens when an x-ray hits an emulsion crystal?
The x-ray deposits its energy w/in the silver halide crystal, releasing a number of electrons (ionization), which travel through the crystal.
These are areas where migrating electrons are trapped within silver halide crystals.
sensitivity specks
What happens after electrons get to the sensitivity speck?
The electrons join with Ag+ to form a silver metal speck(s). During image processing, the crystals with silver deposited at the sensitivity speck will develop into black grains. The crystals that have not been irradiated will remain crystalline and inactive.
What are 2 characteristics by which films vary?
1. sensitivity
2. degree of contrast
How can the sensitivity and contrast of 2 films be compared?
Use of an aluminum block cut w/ varying thickness. The thick portions will attenuate more of the radiation than the thinner sections.
The degree of blackness is measured in terms of ________ ________.
optical density
T/F: a high contrast film will have many shades of gray.
False. A high contrast film will have few shades of gray.
T/F: a film with long latitude also has high contrast.
False. A film with long latitude shows many different shades of gray while film with high contrast quickly changes from black to white with fewer shades of gray in between.
What is a latent image?
An exposed, but undeveloped image. It is not visible to the eye.
What is a manifest image?
The processed x-ray film with an image that is visible to the eye.
What color will areas of a manifest image be that were exposed to irradiation?
shades of black and grey
What color are radiolucent areas of an x-ray film?
black
What color are radiopaque areas of an x-ray film?
white
What are the 4 basic steps of film processing?
1. developing
2. fixing
3. rinsing
4. drying
Which step of film processing converts exposed silver halide crystal into metallic silver? What color is metallic silver?
Developing
black
What creates the black and grey areas on a processed film?
metallic silver
What step of film processing removes the unexposed silver crystals from the film?
fixing
What step of film processing removes residual chemicals from the film?
rinsing
What will happen if the fixing chemical is not completely removed from the film?
The chemical, thiosulfate, will slowly oxidize and cause the image to discolor to a brown color.
How is the film dried during film processing?
By blowing warm dry air over both surfaces of the film.
Why do timing and temperature settings have to be carefully controlled during film processin?
To make sure that only the exposed crystals are converted.
What can happen if the film is placed in the developer for too long?
The unexposed crystals can also be converted to metallic silver.
What can happen if the temperature of the developer is too low?
the exposed crystals will not be converted to metallic silver
What are 2 common reasons for nondiagnostic quality radiographs?
1. inappropriate technique
2. poor positioning
What are 3 things that every radiograph should be critically evaluated for?
1. technique
2. positioning
3. collimation
What are 3 things that poor quality radiographs can lead to?
1. missed lesions
2. misinterpretation
3. future repeat studies
This can be thought of as controlling x-ray "penetration".
kVp
This controls the overall number of x-rays produced and can be thought of as "exposure".
mAs
Typically, the _____ should be at the highest value for the machine. This will allow for the ________ exposure possible.
mA, shortest
What is the first step in identifying technique problems of a radiograph?
Evaluate the peripheral areas of the exposed portion of the radiograph.
If a radiograph is underexposed, what will the appearance be? How should it be corrected?
The peripherally exposed areas should be black. If not, then the film is underexposed and should be corrected by increasing mAs.
If a radiograph is underpenetrated, what will the appearance be? How should it be corrected?
Structures are too white. kVp should be increased.
If a radiograph is overpenetrated or overexposed what will the appearance be? How should it be corrected?
the structures are too black. Either decrease kVp or decrease mAs or a combination of both.
Doubling the mAs will _____ the film blackness.
double
Increasing the kVp 10-15% will _______ the film blackness.
double
~2 x mAs = ______ increase in kVp
10-15%
~1/2 mAs = _______ decrease in kVp
10-15%
kVp is responsible for the _____ of _____.
scale, contrast
What do low kVp settings produce?
A short scale of contrast with few shades of gray within the image.
What scale of contrast is desired for musculoskeletal radiography?
a short scale
What is the ideal kVp range for musculoskeletal radiography?
<70
What is the ideal contrast scale and kVp for abdomen radiography?
medium contrast scale, 75-90 kVp
What is the ideal contrast scale and kVp for thorax radiography?
long contrast scale, 90-110 kVp
This increase in kVp will cause a doubling of the optical density (film blackening).
10-15%
The human eye is only able to detect around a _____ percent change in optical density.
30%
If the film is under/overexposed, at the very least how much must you adjust the kVp to obtain an optical difference?
15% divided by 3 = 5%
When the radiographic technique appears to be substantially off, it is not unusual to have to change the kVp by ____ to _____ % OR ______/_____ the mAs, as required.
15-20%, double/half
What is proper positioning dependent on?
The x-ray beam centering on the structures of interest and the straightness of the animal.
What does proper positioning/collimation require from the DVM/technician?
palpation of the patient, basic knowledge of anatomy
When taking a lateral radiograph of the thorax, what is considered the center?
caudal to scapula, (2 fingers caudal to scapula in large dogs)
When taking a lateral radiograph of the thorax, what structures should be evaluated for straightness?
rib heads superimposed
When taking a lateral radiograph of the thorax, what should the collimator be opened to?
Open to the thoracic inlet, this should include the caudal aspect of the lungs
When taking a VD/DV radiograph of the thorax, what is considered the center?
caudal to scapula, (2 fingers caudal to scapula in large dogs)
When taking a VD/DV radiograph of the thorax, what structures should be evaluated for straightness?
transverse processes of vertebrae and hips (although hips are usually excluded from a thoracic radiograph)
When taking a VD/DV radiograph of the thorax, what are the landmarks for collimation?
Open to thoracic inlet; this should include the caudal aspect of the lungs
When taking a lateral radiograph of the abdomen, what is considered the center?
caudal to the last rib
When taking a lateral radiograph of the abdomen, what structures should be evaluated for straightness?
spinous processes of lumbar vertebrae
When taking a lateral radiograph of the abdomen, what are the landmarks for collimation?
open to hip joint, this should include the entire diaphragm
When taking a VD/DV radiograph of the abdomen, what is considered the center?
Caudal to the last rib
When taking a VD/DV radiograph of the abdomen, what structures should be evaluated for straightness?
dependent on anatomical area
When taking a lateral radiograph of the abdomen, what are the landmarks for collimation?
open to hip joint, this should include the entire diaphragm
When taking a musculoskeletal radiograph, what is considered the center?
Directly on the joint or middle of long bone
When taking a musculoskeletal radiograph, what structures should be evaluated for straightness?
dependent on anatomical area
When taking a musculoskeletal radiograph, what are the landmarks for collimation?
Tight collimation of the joint only. For long bone studies, the entire joint above and below centered area should be included.
What is radiation?
Energy that is radiated or transmitted in the form of rays, waves, or particles.
Which type of radiation has biological implications?
ionizing
Name 2 types of diagnostic imaging that use non-ionizing radiation.
1. ultrasound
2. magnetic resonance imaging (MRI)
Name 3 types of diagnostic imaging that use ionizing radiation.
1. radiography
2. computed tomography (CT)
3. nuclear medicine
What are 3 areas where medical professionals are exposed to radiation?
1. environmental sources
2. Medical treatments for self
3. Occupational (for a patient)
What are 3 major sources of environmental radiation?
1. cosmic radiation
2. Earth's crust
3. human-made
T/F: Tobacco can be a source of radiation.
True: tobacco is a type of human-made environmental radiation.
What type of radiation is emitted from solar flaring on the sun?
Particulate radiation (largely protons)
What filters out a lot of cosmic radiation?
the atmosphere
Why does environmental radiation intensity vary with latitude?
Due to the earth's magnetic fields. Radiation is most intense at the North & South poles and least intense at the equator.
T/F: Cosmic radiation does not vary with altitude.
False. Intensity increases with altitude
T/F: radiation from the Earth's crust varies regionally.
True
What is the largest contributing factor of background radiation dose?
Radon - a radioactive noble gas formed from the decay of uranium. It is colorless and odorless.
What is the second most frequent cause of lung cancer, after cigarette smoking?
radon inhalation
What is the total average annual effective dose of radiation for the US population?
~360mrem
What type of occupational radiation exposure is NOT acceptable?
Accidental primary exposure
What type of occupational radiation exposure IS acceptable?
Secondary exposure - results from scatter from patient, but should use collimation to decrease scatter, lead shielding does not block out all radiation. May also result from tube leakage.
What is the radiation dose limit for non-occupational general exposure?
300mrem/year Excluding natural background radiation/medical exposures.
What is the radiation dose limit for non-occupational medical exposure? What population of people does this apply to?
LD50 for humans = (300-400 rad) or 350,000mrem
healthy young adults w/o medical intervention
What are the radiation dose limits for occupational exposure?
Whole body = <5 rem/year
Hands/feet = 50 rem/year (50,000mrem)
pregnant workers (if declared) = fetal dose limit = <500mrem for total gestation period
What are 3 units of radiation measurement in the International System?
1. Gray (Gy)
2. Sievens (Si)
3. Becquerel (Bq)
What are 3 units of radiation measurement in the old system?
1. radiation absorbed dose (rad)
2. Roentgen equivalent man (rem)
3. effective dose (rem)
This type of radiation measurement is used to measure the amount of energy actually absorbed in tissue. It is valid for any type of radiation. It is purely a quantitative value.
radiation absorbed dose (rad)
T/F: The measurement of rads describes the biological effects of different radiations.
False. Rads is purely quantitative. Although it can be used for any type of radiation, it does NOT describe the biological effects of different radiations.
T/F: All types of radiation have the same biological effect at the same dose.
False. Some types of radiation have a greater biological effect than others at the SAME dose.
T/F: Different types of radiation have different potencies.
True
This can be used to create a common scale allowing comparisons between different types of radiation to be made easily.
radiation weighting factor (WR)
What does "rem" stand for in the context of radiation?
radiation dose equivalent
How is rem calculated?
=absorbed dose (in rads) x weighting factor (WR)
What measurement is used to relate the absorbed dose in tissue to the effective biological damage of the radiation?
rem
The radiation dose equivalent is expressed in terms of Roentgen equivalent man (rem) of the old system. How many rems are in one Sievert?
100 rem = 1 Sv
What is the weighting factor of x-rays?
1
Which is smaller a Sievert or a rem?
1 rem = 1/100 Sv
What is the weighting factor of gamma rays?
1
What is the weighting factor of alpha particles?
20
T/F: Different tissue types have different "radiosensitivities" and can respond differently to the same radiation dose.
True
List the following organs in order of most to least sensitivity to radiation:
gonads
GI
bone marrow
thyroid
breast
lung
everything else
bone surface
gonads
breast
GI
bone marrow
lung
thyroid
bone surface
everything else
What is the most accurate representation of radiation exposure? Why?
Effective dose b/c it takes into account the type of radiation (WR), and the target tissue (tissue WR) being exposed.
What kinds of DNA disruption can irradiation result in?
-Complete repair
-incorrect repair (& subsequent mutations)
-Lack of repair (cell death, mutation, carcinogenesis)
What are some potential results of radiation burns?
erythema (reddening of skin), tissue necrosis, cataracts
Which effect of radiation exposure has a threshold dose?
deterministic effects
Which effect of radiation exposure does not have a threshold dose?
stochastic effects
T/F: With stochastic effects, the effect becomes more severe as the absorbed dose increases.
False. Stochastic effects do not have a threshold dose AND, although the probability of an effect increases with absorbed dose, the actual effect maintains the same severity.
What are two examples of stochastic effects?
carcinogenesis
heritable genetic mutation
With which kind of radiation effect does severity increase with increased dose?
Deterministic effects
Deterministic effects of radiation primarily occur at _____ radiation doses (> _____)
high, >50 rad
T/F: Stochastic effects are only a concern at >50 rad.
False. Stochastic effects are a concern at all doses, even lower ones (<50 rad)
Which radiation effects are primarily of concern to patients?
Deterministic effects
Which radiation effects are applicable to EVERYONE?
stochastic effects
What are fetal effects of radiation dependent on?
-dose
-dose rate
-stage of gestation
What is the dose limit of fetuses per month?
50mrem/month
When can radiation exposure result in fetal death?
Before implantation (0-2 weeks post-conception)
When can radiation exposure result in congenital malformation and carcinogenesis?
2-8 weeks post conception (during organogenesis)
When can radiation exposure result in mental retardation and carcinogenesis?
8-15 weeks post conception (during organogenesis)
When can radiation exposure result only in carcinogenesis? When do these people get cancer?
>25 weeks (fetal period)
Cancer as a child/teenager
What is ALARA? What does it stand for?
A set of guidelines to help doctors protect themselves. As Low As Reasonably Achievable
If you double your distance from the radiation source, what happens to the dose to which you are exposed?
It is decreased by 4x
At 1 meter from a patient, how much scatter radiation will you receive as compared to the patient?
0.1% of the patient's dose of scatter radiation
What is the ideal distance for you to be from the patient undergoing radiation?
>2 meters
T/F: Using cassette holders helps minimize the employee's exposure to radiation.
True
How much can lead aprons/gloves reduce scatter radiation?
1/20th of the dose
What type of radiation do lead aprons/gloves protect the wearer from?
scatter radiation only
Why should a thyroid shield be worn?
Cancer of the thyroid can be induced by relatively low doses of radiation.
How can you check the effectiveness of shielding aprons/gloves?
Make radiographs of them.
What are film badges sensitive to?
Radiation, light, and heat
When are film badges most likely to overestimate the amount of radiation you have been exposed to?
When you wear it outside.
T/F: It doesn't matter where you wear the film badge, so long as you wear it when you are making radiographs.
False: Always wear the film badge on top of the lead shield, never underneath it.
Where should badges be worn if you are pregnant?
One badge should be worn outside the apron. A second badge should be worn under the lead at the level of the abdomen to measure fetal exposure.
T/F: film badges should be worn by employees undergoing medical diagnostic procedures.
False: there are separate and different dose limits for occupational radiation vs. medical radiation (for self)
What are the 3 basic guidelines of ALARA?
-limit time exposed
-maximize distance from radiation
-wear shielding
T/F: the majority of energy from ionizing radiation that is absorbed by the patient is deposited as heat.
True. Heat from ionized radiation is of little biological significance compared to the heat generated by normal metabolic processes.
Radiation induced injury begins with _______ changes at the ______ and _______ level.
chemical, atomic, molecular
T/F: DNA, RNA, and protein can be directly injured with ionization.
True
Indirect injury of ionizing radiation is caused by ______ _________.
free radicals
How many rads are in a gray?
1 gray = 100 rads
What is a rad?
A radiation absorbed dose
What are 5 types of particulate radiation?
1. alpha
2. proton
3. electron
4. positron
5. neuron
What units are used to measure radiation dose equivalents?
rems, Sieverts, and weighting factors
What does a rad describe?
The amount of energy deposited in a gram of tissue.
How do rads relate to rems?
rem (or Sievert) = rads x weighting factor
What is an effective dose equivalent? What units is it reported in?
The weighted dose equivalent for the whole body. It takes into account variations in dose and sensitivity to radiation for the different parts/organs of the body. It is the single best measure of a person's radiation exposure. It is reported in units of rem.
A whole body dose of _____ rem at one time results in a 50% death rate.
500
T/F: The same dose, given at 1 rem/month for 50 years may show no detectable injury.
True
What is the basis of radiation therapy?
A whole body dose of 6000 rem would be lethal, while the same dose, applied at 500 rem, 3 times per week, to a focal area, results in only local effects.
What are the 2 types of radiographic geometry?
1. image geometry
2. exposure geometry
What are 3 phenomena related to radiographic image geometry?
1. magnification
2. distortion
3. unsharpness
What are 2 phenomena related to radiographic exposure geometry?
1. inverse square law
2. heel effect
What are the 3 big degrading factors of image accuracy?
1. magnification
2. distortion
3. unsharpness
What 3 factors affect size of the radiographic image?
1. actual size of the object/subject
2. subject-film distance
3. tube-film distance
What does SFD refer to?
The distance b/w the subject and the film.
The greater the SFD, the _____ will be the degree of magnification.
greater
What does TFD refer to?
The distance between the x-ray tube (focal spot) and the film.
The less the TFD, the _____ will be the degree of magnification.
greater
Why is magnification detrimental to radiographic image quality?
1. size of the image
2. unsharpness of the image
3. distortion of the image
How should magnification be minimized?
Minimize SFD and maximize TFD.
What limits TFD?
The output capabilities of the machine (mAs).
What is the standard TFD, especially with stationary equipment?
40"
What can be misrepresented if an image is distorted?
size, shape, and position
What are 2 causes of distortion?
1. Unequal magnification of different parts of the same object.
2. Location in beam: relative to the central axis of the beam
What is distortion of size and shape due to?
unequal magnification of different parts of the same object.
What is distortion of position due to?
Unequal magnification of distances between parts
What practices are followed to minimize distortion?
-minimize magnification
-keep linear objects parallel to the film and perpendicular to the x-ray beam
-try to center objects in the center of the x-ray beam
-utilize 2 views as a minimum
What is unsharpness due to?
loss of relative detail
What is unsharpness influenced by?
-recording system
-penumbra
-absorption
-motion
What recording systems minimize scatter radiation?
collimation & grids
What is umbra?
the edge of the actual image
What is penumbra?
a partial shadow of the object at the edge of the actual image, resulting in blurring (unsharpness) of the edge of an image.
The following are synonyms of what word:
edge gradient
rim of partial illumination
partial shadow
penumbra
What is penumbra caused by?
definition/projection of the edge of an object by x-rays coming from different angles.
Why does penumbra occur?
It is due to the fact that the focal spot has finite dimensions, and acts as multiple point sources of x-rays, each of which strikes an object at slightly different angles.
How can penumbra be minimized?
Decrease magnification
Decrease focal spot size
In order to minimize penumbra and make magnified radiographs of very small objects, what must be done?
Decrease focal spot size
What is absorption unsharpness due to?
the shape of the object and the resultant pattern of absorption at the edge of the object.
How can absorption unsharpness be controlled?
It can't be; just recognize that it occurs
What is motion unsharpness due to?
movement of patient/tube/film during exposure
How can motion unsharpness be minimized?
Restrain the patient (physical/chemical)
and shorten exposure time
In order to get a higher mA, must the focal spot be smaller or larger? What is the consequence?
larger; more penumbra
What is the inverse square law?
The intensity of the x-ray beam is directly proportional to the mAs and inversely proportional to the square of the distance.
Why is the intensity of the x-ray beam inversely proportional to the square of the distance?
With increasing distance, the beam covers a larger area with the same number of x-rays. (At twice the distance, the beam covers 4x the area)
What is the significance of the inverse square law?
Can convert/adjust a known exposure at a known distance to a new exposure at a new distance if the TFD is to be changed.
What is the heel effect?
The uneven intensity of the x-ray beam within the field.
Where does the x-ray beam have the greatest intensity? Where does it have the least intensity?
Greatest intensity: the side of the target closest to the cathode
Least intensity: the side of the target closest to the anode
Why do x-rays that emerge from the anode side of the target have less intensity than those from the cathode side?
The x-rays that emerge from the anode side, penetrate more of the target before they escape it and are directed at the patient.
What is the heel effect influenced by?
-angle of the target (steeper angle produces more pronounced effects)
-field size (the variation in intensity is less dramatic toward the center of the x-ray field and more pronounced at the periphery)
How can the heel effect be minimized when radiographing large patients with dramatic differences in thickness in the same field?
Position the thicker end of the patient toward the cathode end of the tube where the x-ray beam is more intense.
What is medical imaging?
Application of physics to create images that reflect anatomy, physiology, and pathology of internal structures of the body using external detectors.
What external detector is used in radiography?
x-rays
What external detector is used in ultrasound?
ultrasound waves
What external detector is used in scintigraphy?
y-rays
What external detector is used in MRI?
Magnetic radiowaves
What are 8 modes of radiography?
1. conventional surveys
2. conventional special techniques
3. fluoroscopy
4. linear tomography
5. magnification
6. stereoscopy (uncommon use now)
7. xeroradiography (uncommon use now
8. computed tomography (common)
What are 4 special techniques used in conventional radiography?
1. contrast studies
2. positional radiography
3. compression radiography
4. stress radiography
What is "mew" (u)?
an absorption coefficient that describes how the composition of an object relates to interaction of x-ray beams in tissues.
The intensity of an x-ray beam as it emerges from the subject is ______ proportional to the original intensity of the beam and ________ proportional to the thickness of the object and absorption coefficient of the tissue.
directly, inversely
What is an attenuation coefficient?
A mathematical factor relating to a material's absorption of x-rays.
What does tissue density refer to?
The tissue's inherent composition (which determines u) rather than its actual physical density. It determines absorption of the x-ray beam.
short scale = ______ _______
high contrast
long scale = ________ ________
low contrast
Explain the concept of a differential interface.
Specific structures are visible radiographically if surrounded by "tissue" of a different density.
Explain the concept of silhouette sign.
Margins of objects of the same tissue density that are in contact cannot be visualized separately.
Explain the summation effect.
Radiographic densities/opacities are additive. (Example: an infected tympanic bulla superimposed over a normal tympanic bulla will not be diagnostic of which/both are inflamed.)
What are 2 potential consequences of the summation effect?
1. superimposed objects: distortion of shape and/or radioopaque/radiolucency
2. superimposed shadows: allows visualization of an opacity that might not otherwise be visible or truly present
Describe how a fluid-air interface within a cavity can be recognized radiographically.
From above, a cavity containing both fluid and air may or may not be recognizable. If both air and fluid are present in the bladder, the air will show up as a small, more radiolucent oval in the center if there is more fluid than air. If there is more air than fluid, the radiolucency may cover the whole image of the bladder. However, it could be recognized by a beam directed horizontally at the bladder. In that case, all the fluid would settle to the bottom and there would be a sharply marginated line at the fluid-air interface.
What do radiographic signs provide?
An objective, analytic means of evaluating and verbalizing structures on radiographs
By what categories can all findings/objects on a radiograph be described?
density
geometry
function
What does "density" refer to?
Inherent tissue density, NOT opacity/lucency due to size.
What characteristics are included in radiographic geometry?
size
shape
number
position
margination
T/F: Evaluation of function can normally be done via a survey radiograph.
False. Evaluation of function usually requires some sort of special procedure.
What are some functional characteristics of organs?
integrity
patency
motility
excretion
Sequential radiographs are useful for documenting ________ ________ over time.
functional changes
Sequential radiographs over ______ is necessary for documenting bone healing.
weeks
Sequential radiographs over ______ is necessary for documenting GI transit.
hours
Sequential radiographs over ______ is necessary for documenting urinary excretion
minutes
Sequential radiographs over ______ is necessary for documenting blood flow.
seconds
What are the 3 components of radiographic interpretation?
1. Radiograph Quality
2. Interpretation
3. Correlation
What is a diagnostic quality radiograph?
-one that does not obscure lesions that are present,
-one that does not create the impression of lesions that are not present
This should be prepared for abdominal radiography in order to obtain a diagnostic quality radiograph. Why?
The stomach and colon should be empty b/c ingesta and fecal material can obscure subtle changes in most of the abdomen.
Overexposure will "____ ____" subtle lesions.
"burn out"
What is the contrast scale influenced by?
-object composition
-mAs-kVp relationship
-Film-screen system
Why should radiographs always be taken from 2 views?
A single radiograph is a 2D image of a 3D object. You may be able to imagine what the object would look like from a different view, but lesions are unfamiliar objects and may only be understood and recognized from an alternate view.
T/F: Radiographs are easily damaged.
True
Where should radiographs be viewed?
In an isolated, quiet environment w/o distractions.
What do dividers do in a radiographic view box?
They focus the light into boxes.
What do rapid ballasts do in radiographic view boxes?
They "jump start" illuminators so that they do NOT flicker for awhile before being switched on.
What tint of fluorescent bulbs is preferable for viewing radiographs? Why?
Green tint improves contrast
What is a hot-light? What is it used for?
It is a focal, intense light source that is used to view overexposed (dark) areas on the film.
What should you do to protect a radiograph from a hot-light? Why?
Maintain some distance from the light and keep moving the film as you move it so that the film doesn't melt.
For all lateral radiographs, how should you view them?
With the head of the animal to your left and the tail to your right.
For all VD/DV radiographs, how should you view them?
As if ventrodorsal with the head directed upward and as if you were shaking hands with them (their right to your left)
For all cranio-caudal and caudo-cranial radiographs, how should you view them? What is the exception?
As if you were viewing them from cranially and shaking their hand (their right to your left)
Exception: bilateral studies for comparing extremities
When describing radiographic findings, how should you refer to the position of an abnormality?
Refer to the position on the patient, rather than it's relative position to the viewer. i.e, the patient's right side, the viewer's right side.
What should you avoid doing once you recognize one abnormality on a radiograph?
Avoid stopping your search, instead, continue to read the whole film.
What is a strategy to make sure that you evaluate an entire radiographic image?
Cover the film from periphery to center or in reverse and make a mental check list as you evaluate each organ.
T/F: it is easy to differentiate normal and abnormal as long as you know what normal looks like.
False. It is difficult to differentiate normal and abnormal because there is a broad range of normal due to differences of species, breed, age, etc.
T/F: some abnormalities are obvious but clinically insignificant.
True
T/F: some abnormalities are subtle but clinically very significant.
True
What are the pros and cons of bias in interpreting radiographs?
pro: helpful for finding subtle lesions
con: detrimental in over-interpreting some findings
What is a gamut?
A list of differential diagnoses that can account for, or produce, the radiographic findings observed.
T/F: Radiographic findings sometimes provide a definitive diagnosis.
True, albeit infrequently
What must be legally included in radiographic film identification?
-the label must be permanent
-label must be applied prior to development (conventional radiography)
-ownership of the radiograph
-date the radiograph was made
-Patient ID
T/F: At present digital imaging labels can not be manipulated, are consistent and standardized.
False. At present, digital imaging labels CAN be manipulated, are NOT consistent, and have NOT been well standardized.
T/F: a conventional radiograph that has been labeled with pen after development will legally stand up in court.
False.
What are lead letters used for?
Identifying sides and directions of radiographic images.
Examples: L, R, VD, DV, DLPaMO, DMPaLO, etc
T/F: You may rely fully on lead letters as you are interpreting a radiograph.
False. The letters are often erroneously placed.
What are 3 labeling types that can be used to apply legal labels to conventional radiographic films?
1. leaded tape
2. Marker sets
3. photoprinter
What is the preferred labeling system for conventional radiography? Why?
photoprinter b/c it does not limit collimation, is usually legible, can provide information about the view, and quality
What types of labeling systems used for conventional radiography limit collimation? Why?
leaded tape & marker sets b/c they must be included in the x-ray field
When should lead letters appear backwards on a radiographic film?
When the film is flipped over (different from the way that it was taken)
How can you tell that a radiograph was a right lateral?
The label is legible when the image is in the standard position (head to left and tail to right, with dorsum up and ventrum down).
With a left lateral radiograph, which side of the animal is closest to the cassette/viewbox?
the left
What is another way to say "left-to-right lateral"?
right lateral
With a "right-to-left lateral" which side of the animal is closest to the cassette/viewbox?
The left
How can you tell if a radiographic view is VD?
With the image properly positioned, the patient's right side is to the viewer's left, and the label is legible.
If the head is up and the patient's right side is to your right side, what is the view of the radiographic?
DV
When a radiographic view is VD, which side of the animal is closest to the x-ray tube?
the ventrum
In small animals, what is the direction of conventional lateral extremity views?
From medial to lateral
If on a lateral view of a small animal extremity, the label is legible, the proximal side is directed upward, and the patient's head is to the viewer's left, is a right or a left limb being viewed?
Right
If on a lateral view of a small animal extremity, the label is legible, the proximal side is directed upward, and the patient's head is to the viewer's right, is a right or a left limb being viewed?
left
If on a lateral view of a large animal extremity, the label is legible, the proximal side is directed upward, and the patient's head is to the viewer's left, is a right or a left limb being viewed?
left
If on a lateral view of a large animal extremity, the label is legible, the proximal side is directed upward, and the patient's head is to the viewer's right, is a right or a left limb being viewed?
right
In large animals, what is the direction of conventional lateral extremity views?
lateral to medial
What does Cr-Cd stand for?
A cranial-caudal view, usually of an extremity.
What does D-Pa/Pl stand for?
Dorsal Palmar - Plantar view
What is the extra convention that is used for labeling Cr-Cd and D-Pa/Pl views of extremities?
Always place a marker/printer block along the lateral aspect of the extremity.
What is the labeling convention for oblique views of extremities, including the skull?
place lead letters on both sides to identify parts projected/isolated
Should lead markers be placed right-side up or right-side down on the cassette/table when taking a radiograph?
Right side up.
What is a synonym and the preferred term for "absorption coefficient"?
Attenuation coefficient
What is the #1 use of contrast medium?
To overcome silhouette effects.
What radiographic signs can be evaluated when contrast media is used?
Geometry & function
What radiographic sign can NOT be evaluated when contrast media is used?
density
What criteria are evaluated when choosing a contrast medium?
-safety
-specificity
-radiopacity
-reproducibility
-cost
What are two types of CM?
positive (pCM)
negative (nCM)
What is negative contrast media?
CM of lesser radiopacity than normal tissue.
What are 3 types of negative CM?
1. gas
2. CO2
3. air
Which negative CM is the safest? Why?
CO2 b/c it will dissolve in blood
Which negative CM is most likely to embolize in blood?
air
What is the rationale for using negative CM?
By filling the lumen of an organ with gas, it is possible to improve visualization of structures in or adjacent to the gas filled cavity.
What are the most common uses of negative CM?
For pneumocystography (bladder) and pneumocolon
T/F: nCM provides more contrast differential with adjacent structures than pCM.
False. Positive CM provides more contrast with adjacent structures
What is positive CM?
CM of greater opacity than normal tissues
What types of positive CM are used routinely?
Barium (Ba) and Iodine (I)
T/F: Attenuation coefficients of Ba and I are greater than normal body tissues.
True
What are common uses of pCM intraluminally or intracavitary?
alimentary tract studies, angiography, cystography, urethrography, myelography
What are common uses of pCM systemically?
intravenous urography, cholecystography
What are some problems that may be associated w/ pCM?
Inappropriate agent, concentration, or formulation, toxicity
What are barium sulfate products used for primarily?
alimentary tract contrast studies
What are the 3 major groups of BaSO4 based on physical consistency?
powder
paste (cream)
liquid
Why is the use of bulk BaSO4 powder discouraged?
B/c they require more time and effort and result in a suspension of lower quality than slightly more expensive cream and liquid preparations.
T/F: BaSO4 paste is used ONLY to study the esophagus.
True
What characteristic of BaSO4 paste allows radiographic visualization of the esophagus after the swallowed bolus has passed?
It's thick and creamy consistency coats the esophageal mucosa as it passes.
What is the consistency of BaSO4 paste analogous to?
toothpaste or whipped cream
What is the quality of liquid BaSO4 preparations for GI studies dependent on?
Their ability to stay in suspension.
What factors contribute to the quality of liquid BaSO4 suspensions?
particle size, suspending agent
What are 4 factors that contribute to the value of liquid BaSO4?
particle size
suspending agent
flavoring agents
concentration
Describe commercially prepared liquid BaSO4 products.
They are micronized, have suspending and flavoring agents, are premixed and are sold in liquid form in cans or plastic screw-top bottles.
What is the CM "of choice" for liquied BaSO4?
commercially prepared liquid BaSO4
T/F: Some commercially prepared BaSO4 products must be diluted.
True; this depends on the agents included and on the study to be performed.
A liquid BaSO4 product of about ____%____ is preferred.
40% w/w
What should be the least influential factor in choice of a BaSO4 product?
the cost
T/F: BaSO4 products are nontoxic w/in the lumen of the bowel.
True
This can be caused by leakage of BaSO4 from the alimentary tract into the pleural or peritoneal cavity.
Chronic, granulomatous inflammation
What serious problem is caused by aspiration of a large volume of BaSO4?
problems w/ air exchange, which can be lethal
What is aspiration of a small volume of BaSO4 cleared by?
muco-ciliary transport
T/F: BaSO4 has been used for bronchography.
True
T/F: inorganic iodides are systemically toxic
true
How is toxicity of inorganic iodine diminished?
By stable binding of I to a less toxic, organic molecule
What can "organic iodides" be used for?
various applications including: angiography, intravenous urography, cystography, urethrography, cholecystography, myelography, alimentary tract studies, bronchography, etc.
What type of agents are used for urographic CM?
agents that are water-soluble, tri-iodinated, benzoic acid derivatives.
Aka: aqueous, organic, iodinated (Ag Org I) CM
What are the 2 most commonly used anions in urographic CM?
1. iothalamate
2. diatrizoate
What are 2 cation compounds used in urographic CM?
1. Na
2. Methylglucamine (meglumine) (a short, organic radical)
What is the composition of Urographic CM?
May be a single solution of one specific compound or may be a mixture of Na or meglumine salts with the same anion.
T/F: the concentration of urographic CM can vary between products.
True
What accounts for the physiological and toxicologic effects of urographic and angiographic CMs?
Most of these CMs are very hypertonic (~1500 milliosmolar = ~ 5x more osmolar than normal serum)
A container of Conray 400 says in its generic name, "Na Iothalamate (66.8%)." What does 66.8% refer to?
The % of medium in solution, NOT the amount of iodine
T/F: All urographic and angiographic CMs used in veterinary medicine have been approved for such use by the FDA.
False, in the list given, only Renografin-76 is specifically approved by the FDA for veterinary medicine.
What product of urographic/angiographic CMs do most practicing veterinarians keep on their shelves?
The product with the highest concentration. They then dilute it as necessary.
How is Ag Org I CM excreted when it is administered systemically?
Almost entirely by the kidneys through glomerular filtration b/c it has very low binding in the blood and is neither secreted nor reabsorbed by the tubules
What are some uses of Ag Org I CM?
angiography, venography,
intravenous urography,
cystography, urethrography,
peritoneography,
fistulography, lymphangiography
What are some mechanisms by which Ag Org I CM used for urographic and angiographic studies produce complications?
hemodynamic
chemotoxic
idiosyncratic
T/F: CM reactions are infrequent and usually mild.
True
T/F: CM reactions are potentially lethal.
True
What are some mild reactions associated with Ag Org I CM?
Nausea and vomiting are fairly common. Limited utricaria.
What is urticaria?
a vascular reaction of the skin that is commonly immunologically based or may be due to direct exposure to a chemical. It is marked by a transient appearance of slightly elevated patches which are redder or paler than the surround skin and often attended by severe itching, (aka hives)
What are some intermediate reactions assoc. w/ Ag Org I CM?
anaphylactic: wheezing, bronchospasm, severe urticaria
How are anaphylactic reactions to Ag Org I CM treated?
Antihistamines, corticosteroids
What are some severe reactions assoc. w/ Ag Org I CM?
cardiovascular collapse: hypotension, tachycardia, dyspnea, cyanosis, death
How is cardiovascular collapse that results in reaction to Ag Org I CM treated?
Epinephrine (immediately), corticosteroids, antihistamines, fluids, etc.
What is oliguria?
reduced daily output of urine.
What is anuria?
No output of urine due to complete suppression of urine formation by the kidney
Why should patients be hydrated before administering Ag Org I CM?
Administration of CM to dehydration that are also azotemic or have a multiple myeloma (aka immunoblastic sarcoma) may develop acute oliguria or anuria.
What are some possible contraindications of Ag Org I CM?
-multiple myeloma (aka immunoblastic sarcoma) w/ or w/o dehydration
-concurrent renal failure
-Dehydration w/ azotemia
When may Ag Org I CM be used in the alimentary tract?
For suspected perforation of the alimentary tract.
Why should BaSO4 not be used when the alimentary tract may be perforated?
BaSO4 is not absorbed in body cavities and causes a chronic, granulomatous reaction.
Why may Ag Org I CM be used in perforated alimentary tracts?
They cause an acute, mild inflammatory response and are absorbed and excreted.
Why should Ag Org I CM NOT be used for routine alimentary contrast studies?
-It is more expensive than BaSO4
-It is very hypertonic, thus retains and/or pulls fluid into the bowel lumen leading to patient dehydration
-Irritates the bowel due to rapid transit time, and can induce vomiting
Which CM are more hypertonic, ionic or non-ionic?
non-ionic
How do myelographic CM differ from those commonly used for urography and angiography?
Myelographic CM: newer, non-ionic, with lowered osmolality, and less frequent side effects.
What complications are associated with myelographic CM?
apnea (if injection is too rapid)
seizures (esp. large breed dogs, esp. cervical myelograms)
What is the application of myelographic CM?
intrathecal
What does intrathecal mean?
within a sheath; through the theca of the spinal cord, into the subarachnoid space
What are 2 generic names of myelographic CM?
1. Iohexol
2. Iopamidol
Define digital radiography (DR).
Imaging technique that uses x-ray energy and computers to create radiographic images.
There are 2 basic methods of digital radiography, what are they?
1. indirect
2. direct
What do IDR, computed radiography, and CR all refer to?
Indirect digital radiography
Explain how images are formed using indirect digital radiography.
1. When exposed to x-rays, crystals in a phosphor screen temporarily change their chemical state and store energy.
2. The latent image is read when the plate is scanned with a red laser light. The electrons release their energy and return to ground state by emitting visible light, which is measured by light-sensitive detectors in the scanner.
3. Light energy is converted to electrical energy, which is converted to digital image data by computer software.
Why do plates for IDR need to be erased after each exposure?
To eliminate residual energy and avoid "ghost" images
What does DDR or DR stand for?
Direct digital radiography
Explain the process of direct digital radiography.
1. Uses amorphous selenium in a flat panel (usually glass) to convert absorbed x-ray energy directly into liberated electrons. The number of electrons trapped is linearly related to x-ray intensity.
2. Electrons are stored in a thin-film transistor array.
3. Electrical energy from each pixel in the array is transferred to a computer workstation directly by way of a wired connection.
4. Electrical energy is converted to digital image data by computer software.
What does PACS stand for?
Picture Archiving and Communication System
What is PACS?
A central server that stores digital images from either IDR or DDR workstations. The server is used for long-term storage and can be accessed by users from multiple computer stations, usually through a web browser.
Using PACS workstations and software, users can do what?
-image manipulations as needed for interpretation
-annotate images to emphasize pathology
-record an interpretation and store it w/ images
-convert selected images to jpeg files
-email selected images to practitioners
-burn images onto CD's
-print images onto paper (for perfect calibration for orthopedic services)
What are 8 advantages of digital radiography vs. conventional radiography?
1. No film or processing costs
2. no film storage space needed
3. Faster turnaround time
4. mobile units are available for field service
5. Decreased need for retakes w/ software correction techniques, CAN SEE SOFT TISSUE & BONE DETAIL IN A SINGLE IMAGE
6. Images can be manipulated to emphasize areas of concern and aid diagnosis
7. Images can be reviewed by multiple users at the same time (PACS)
8. Easier to share images with others
What are 6 disadvantages of digital radiography vs. conventional radiography?
1. Expensive to purchase/lease
2. image interpretation requires a high quality computer monitor and software
3. Detector panels for DDR systems are connected to the x-ray machine by an electrical cord - can be difficult to maneuver & easy to damge.
4. panels are more fragile and more expensive to replace than cassettes
5. lower spatial resolution
6. cannot compensate for poor positioning, improper labeling or incorrect use of technique chart
What is fluoroscopy?
An imaging technique that uses x-ray energy and an image intensifier to visualize MOVING internal structures.
Where is the x-ray tube positioned in fluoroscopy?
underneath the table and patient
What do fluoroscopy x-rays project to?
An image intensifier centered above the area of interest.
Explain how fluoroscopy images are captured and displayed.
1. x-ray photons cause crystals in the image intensifier's input screen to emit light (fluoresce).
2. The light energy is converted to electrons after striking a photocathode.
3. The electrons are accelerated across the fluoroscopic tube by a series of electrostatic lenses.
4. High-energy electrons are converted back to light energy when they strike fluorescent crystals in the output screen.
5. The light image coming from the output screen is smaller and brighter than the image originally recorded by the input screen.
6. This intensified light image is displayed on a television monitor or recorded on a video tape. Info can also be digitized and stored on a computer.
How can overlying bones be digitally subtracted for contrast studies?
Using a feature called "masking" in fluoroscopy.
What are 3 advantages of fluoroscopy?
1. allows real-time viewing of structures in motion
2. permits interactive adjustments of fixation devices, biopsy needles, or indwelling tubes
3. images can be acquired digitally and manipulated with computer software
Name 6 common applications of fluoroscopy in vetmed.
1. Assess motility of anatomic structures
2. Guide placement of needles/catheters prior to injection of contrast agents (e.g. myelography, angiography)
3. guide placement of implants (e.g. pacemakers, balloon catheters, bone pins)
4. guide fine needle aspirates and biopsies (e.g. spine, lung, bone)
5. check placement of feeding tubes
6. evaluate morphology and integrity of collapsible anatomic structures.
Define "computed topography".
A digital imaging technique that uses x-ray energy and computer processing to make cross-sectional (transverse) images of structures.
What does CT stand for?
computed topography
Describe how CT images are formed.
1. The x-ray tube is housed w/in a ring-shaped gantry.
2. A motorized table advances the patient through the gantry for each slice.
3. Slices are made when the x-ray tube rotates in a circle around the patient. The energy of transmitted x-rays is recorded opposite the patient by detectors.
4. Detectors convert x-ray energy to an electrical signal.
5. A computer converts the electrical signal to numerical (digital) data.
6. Digital data are converted to shades of grey based on relative tissue density.
In CT, white represents ____ dense tissue; black represents _____ dense tissue.
more, less
Advantages of CT vs radiography.
1. better contrast resolution (can detect more subtle tissue density differences)
2. Eliminates problem of superimposition
3. Digital image data can be manipulated by computer graphics programs
T/F: Transverse (CT) images can be added together to allow the creation of images in sagittal, dorsal, and oblique planes.
True
T/F: Transverse (CT) images can be added together to create 3D and color-enhanced images.
True
What are 4 common uses of CT in vetmed?
1. Diagnosing suspected intracranial disease
2. staging neoplasms (size, invasion, spread to regional lymph nodes, etc.)
3. guiding biopsies
4. planning surgical procedures in complex anatomic regions
What does MRI stand for?
Magnetic Resonance Imaging
What is magnetic resonance imaging?
An imaging technique that uses a strong magnetic field and pulses of radiofrequency energy to cause tissues to emit characteristic energy signals.
What is the most common application of MRIs?
brain disease
Describe the process of taking MRIs.
1. A motorized table centers the patient in a tube-shaped/open-gantry in which there is a constant strong magnetic field.
2. While inside the gantry, hydrogen atoms from the patient's tissues align themselves w/ the magnetic field.
3. Tissues are intermittently exposed to brief pulses of radiofrequency energy to temporarily knock the hydrogen atoms out of alignment
4. A weak energy signal (resonance) is released from the tissues as the hydrogen atoms realign themselves with the magnetic field.
5. A receiver coil is placed near the anatomic region of interest to record the signal coming from the tissues.
6. The strength of the returning signal varies based on inherent tissue factors, strength of magnetic field, and technique settings.
7. A computer converts the signal intensity to varying shades of grey in the image.
What are 2 inherent tissue factors that causes MRI signals to vary?
1. concentration of hydrogen atoms
2. interactions of the hydrogen atoms with each other.
What 3 computer technique settings cause MRI signals to vary?
1. duration of each radio-pulse
2. frequency of radio pulses
3. how long the signal is recorded by the receiver coil after the pulse occurs.
In MRI, tissues with _____ signal intensity are assigned whiter colors.
higher
In MRI, tissues with _____ signal intensity are assigned darker grey colors.
lower
In MRI, tissues with ____ signal appear black.
no
Give 2 examples of tissue that appear black on MRIs.
air
bone
What are 3 advantages of MRI vs. CT?
1. highly sensitive for subtle changes in soft tissues
2. allows images to be created in any plane desired, w/o having to move the patient
3. does not expose the patient to ionizing radiation
Name 2 common applications for MRI in vetmed.
1. intracranial disease
2. equine soft tissue injuries (ex: deep digital flexor tendon, navicular bursa)
What does NI stand for?
Nuclear Imaging
What is nuclear imaging?
An imaging technique based on the selective accumulation of radioactive chemicals within tissues.
What are radiopharmaceuticals?
radioactive chemicals
What are 3 synonyms of nuclear imaging?
1. nuclear scintigraphy
2. nuclear scans
3. scintigrams
Describe the process of nuclear imaging.
1. A small volume of radopharmaceutical is injected into the patient.
2. The radiopharmaceutical may be used alone or attached to a chemical that will be selectively accumulated by the tissue of interest.
3. The radiopharmaceutical emits gamma radiation as it decays to an inert form
4. A gamma camera records the gamma radiation emitted and converts it to an electrical signal
5. A computer converts the electrical signal to digital information that is used to create the image.
6. Following the procedure, the patient is kept in an isolated holding area until the radiation emissions are reduced to background levels (1-3 days)
What is the most common radiopharmaceutical used in vetmed?
technetium 99m
Why is technetium 99m preferred in vetmed?
1. Radioactive decay is very fast (t1/2=~6hrs)
2. The energy of the gamma rays emitted is relatively low
What are hotspots on NI?
Tissues w/ a high concentration of radiopharmaceuticals that appear dark.
What are coldspots on NI?
Tissues w/ low concentration of radiopharmaceuticals that appear white.
With new software with computer enhancement of nuclear imaging, what can be the appearance of hotspots?
bright red or yellow as desired
What are 5 advantages of nuclear imaging?
1. fast
2. relatively inexpensive
3. can be performed w/ only light sedation
4. provides a quantitative measure of tissue or organ function
5. highly sensitive for early changes in physiology
What are common applications for nuclear imaging in vetmed?
1. localizing causes of lameness
2. diagnosing suspected thyroid hyperactivity or neoplasia
3. locating sites of bone metastasis
4. Quantifying liver/kidney function (ex: porto-caval shunt fractions, glomerular filtration rate)
Why has ultrasound become so popular?
Because it differentiates soft tissue better than radiology and does not use ionizing radiation exposure.
What is the frequency range of audible sound?
15,000 - 20,000 Hz
What is the frequency range of medical ultrasound?
2-20 million Hz (highly specialized even goes up to 50 million Hz)
What part of the ultrasound machine creates the sound waves?
the transducer
What does an ultrasound transducer do?
transmits sound waves and receives reflected sound waves.
Where are sound waves reflected?
At interfaces between tissues that differ in density.
This is the speed of sound in tissue x density of tissue.
acoustic impedence
T/F: the speed of sound is basically the same in all soft tissues.
True
The greater the difference in tissue density, the ______ the amount of reflection.
greater
Describe the amount of reflection and the appearance of a soft tissue-air interface when using ultrasound.
complete reflection
shadow deep to the interface
Describe the amount of reflection and the appearance of a soft tissue-bone interface when using ultrasound.
near complete reflection
shadow deep to interface (usually black shadow)
Describe the amount of reflection and the appearance of a soft tissue-fluid interface when using ultrasound.
no attenuation of sound wave through fluid
acoustic enhancement
What is acoustic enhancement?
On the other side of the fluid, the tissue appearance is more white than the tissues on either side.
What causes acoustic enhancement?
There is no attenuation of sound waves in fluid so once the sound waves exit the fluid, they are stronger than surrounding sound waves.
What is the B-mode of ultrasound image display?
brightness mode
What is the M-mode of ultrasound image display?
motion mode
In the B-mode how are returning echoes displayed on the ultrasound screen?
as dots
In the B-mode, the brightness of each dot corresponds to the strength of the _______ _____.
returning echo
In the B-mode, the location of each dot corresponds to the _____ of the reflecting interface.
location
T/F: in the motion mode of ultrasound, the image is one-dimensional.
True
How is time and depth displayed on an M-mode ultrasound image?
x-axis: time
y-axis: depth
What is the M-mode ultrasound used for?
echocardiography - can measure exact systole and exact dystole this way
What is the shape of a linear array U/S transducer? What type of contact area is required?
shape: rectangular
image: rectangular
contact area: large
What is the shape of a curved linear array U/S transducer? What type of contact area is required?
shape: curved rectangle
image: sector image w/ curved, flat top
contact area: large
What is the shape of a U/S sector transducer? What type of contact area is required?
shape: sector (pie-shape)
contact area: smaller than for linear arrays
T/F: Higher U/S frequencies result in better penetration.
False. Higher U/S frequencies result in better resolution.
T/F: Lower U/S frequencies result in better penetration.
True.
What U/S frequency should be used?
The highest frequency which allows adequate penetration of the body part.
How should a patient be prepared for U/S?
1. Remove hair
2. Gel (coupling agent - better interface b/w skin and transducer)
3. dorsal or lateral recumbancy
4. Avoid anything that would introduce gas into the stomach/colon.
What is echogenicity?
The intensity of the reflected U/S sound.
What are 4 words that describe U/S echogenecity?
1. hypoechoic
2. hyperechoic
3. isoechoic
4. anechoic
What does hypoechoic mean?
On a U/S image, this is darker than surrounding tissue.
What does hyperechoic mean?
On a U/S image, this is brighter than surrounding tissue.
What does isoechoic mean?
On a U/S image, this has the same echogenicity as surrounding tissue.
What does anechoic mean?
On a U/S image, this is black b/c it has no internal echoes.
Place the following organs in order of most echogenic to least echogenic:
renal cortex
renal medulla
renal sinus
prostate
liver
spleen
renal sinus
prostate
spleen
liver
renal cortex
renal medulla
T/F: As in radiography, organs should be examine with at least 2 ultrasound views.
True
What are 2 ways that U/S images can be oriented?
1. longitudinal
2. transverse
This U/S view has the cranial end to the viewer's left, the caudal end to the viewer's right, the dorsal side at the top, and the ventral side at the bottom.
longitudinal image
This U/S image has the right side of the animal to the viewer's left, the left to the viewer's right, the ventral side at the top of the image, and the dorsal side at the bottom of the image.
transverse image
These are the primary areas of the body that are examined by U/S.
abdomen
thorax
musculoskeletal
ocular
guided biopsies
These are 6 uses of U/S for the abdominal cavity.
1. Diffuse organ disease
2. Focal organ disease
3. Abnormal mineralization
4. Small organs that are not visualized w/ radiography
5. pregancy
6. Free fluid
Give 3 examples of diffuse organ diseases in the abdomen.
1. hepatic lipidosis
2. splenic lymphosarcoma
3. chronic renal disease
Give 3 examples of focal organ disease in the abdomen.
1. neoplastic masses
2. abscesses and hematomas
3. cysts
Give 2 examples of abnormal abdominal mineralizations.
1. cystic calculi
2. renal calculi
Give 4 examples of small abdominal organs that are not visualized radiographically.
1. pancreas
2. adrenal glands
3. lymph nodes
4. blood vessels
What non-cardiac thoracic abnormalities can be viewed with U/S?
1. pleural effusion
2. mediastinal mass
3. pulmonary & chest wall mass
4. diaphragmatic hernia
What will occur if the area of interest is not in the center of the x-ray beam? Why?
There will be distortion due to divergence of the x-ray beam at the outer margins of the x-ray field of view.
How can a person viewing a radiograph determine the bone outlines of overlying bones?
Follow the cortical margins.
Through what process does bone form?
Mesenchymal cell transformation
What are the 2 main processes involved in mesenchymal cell transformation?
1. endochondral ossification
2. intramembranous ossification
Where does endochondral ossification take place?
At physeal growth plates
Where does intramembranous ossification take place?
in flat bones, e.g. the skull
This is the ends of long bones.
epiphysis
This is a growth plate
physis
This is between a diaphysis and a physis.
metaphysis
This is the shaft/middle of bone.
Diaphysis
This is the secondary center of ossification at a ligamentous or tendinous attachement.
apophysis
What are 9 components of a systematic orthopedic radiograph interpretation?
1. check labels & image annotation
2. evaluate position & posture
3. evaluate soft tissues
4. check all periosteal margins
5. check all bony cortices and subchondral bone
6. check for changes in opacity in the medullary cavity
7. Check joint capsule attachments for bone production/destruction
8. Check physeal closures as they relate to the age of the animal
9. Check overall alignment and relationship of bones
In what ways can soft tissues change?
-opacity (radiographically)
-size
What can gas in the tissues result from?
-Disruption of the skin surface w/ open communication with air
-gas producing organism
-iatrogenic (post-op or following perineural anesthesia (nerve blocks))
Name 3 mechanisms of soft tissue mineralization.
1. dystrophic mineralization
2. metastatic mineralization
3. neoplastic mineralization
This is mineralization of dead, devitalized or degenerative soft tissues.
dystrophic mineralization
What are some causes of dystrophic mineralization?
-blunt trauma
-calcinosis circumscripta
-parasite migration
-inflammation
-granulomatous disease
-site of injections (esp. corticosteroids)
-thermal injury
-chondrocalcinosis
-secondary to degenerative joint disease
This is mineralization of normal soft tissue that occurs due to sustained elevated serum calcium and/or phosphorous levels (above 70).
metastatic mineralization
What are some nonvisceral tissues that can undergo metastatic mineralization?
-intima of arteries
-periarticular soft tissues
-ocular tissues
-subcutaneous tissue
What are some visceral tissues that can undergo metastatic mineralization?
-stomach mucosa
-lungs
-kidneys
-heart
What are some causes of metastatic mineralization?
-chronic renal failure
-malignant neoplasia
-hypoadrenocorticism
-hyperparathyroidism
-hypervitaminosis D
-hypervitaminosis A
This is bone-producing neoplasia (osteosarcoma) in soft tissue.
Neoplastic mineralization
What is the decrease size of soft tissues typically due to?
muscle atrophy
What are 2 potential causes of muscle atrophy?
1. chronic lameness
2. neurogenic (either denervation/lack of stimulation)
T/F: Disuse atrophy of muscles occurs slower when it is caused by chronic lameness rather than from lack of neurogenic stimulation.
True
T/F: radiographic bone changes often lag behind clinical lameness.
True
T/F: In some instances, it is impossible to reach a definitive diagnosis based solely on radiographic abnormalities.
True
When determining the significance of a bony lesion of unknown etiology, what factors should be considered?
-location of the bone lesion
-opacity of the lesion
-rate of change of the lesion
-pattern of bone lysis
-pattern of periosteal reactions
-aggressiveness of the lesion
T/F: an aggressive bone lesion may need a biopsy to guide immediate therapy.
true
This bone lesion may indicate metabolic or nutritional diseases. Extensive changes (30-60% decrease) in mineral content is necessary before radiographic changes can be seen.
Generalized lesion
This type of lesion is easier to detect than generalized lesions b/c of the contrast b/w normal and abnormal bone.
focal lesion
T/F: Diseases that are characterized radiographically by increased bone opacity have less bone production than reabsorption.
False: Diseases that are characterized radiographically by increased bone opacity have MORE bone production than reabsorption.
How long after an insult do lytic bone changes become evident radiographically?
5-7 days
How long after an insult do productive bone changes become evident radiographically?
10-14 days
This is a general term used to describe a generalized decreased bone opacity on radiographs.
osteopenia
What are the signs of osteopenia on radiographs?
-diminished bone opacity
-cortical thinning
-endosteal reabsorption
-relative increase in opacity of cortical bone and vertebral endplates
-double cortical line usually assoc. w/ rapid bone loss
-bone deformity
-lass of lamina dura around teeth
What are 2 causes of osteopenia?
1. osteoporosis
2. osteomalacia
This is a loss of bone mass.
osteoporosis
This is a loss of mineralization of the bone matrix.
osteomalacia
In this type of osteopenia, the bone is normal, but there is not enough of it.
osteoporosis
In this type of osteopenia, the osteoid matrix is present, but it is not completely mineralized.
osteomalacia
What do bones characterized by osteomalacia feel like grossly and look like radiographically?
-The bone becomes soft.
-There are wide, transverse lucencies ("looser lines")
T/F: Bone lysis may be aggressive, semi-aggressive, or nonaggressive.
True
What are some radiographic characteristics of aggressive bone lesions?
The margins may be indistinct and there is not a clear demarcation b/w the lesion and normal bone. There may be a wide zone of transition. They have rapid bony loss, and result in cortical lysis.
These bone lesions may have sharp margins, narrow transition zones.
nonaggressive
This type of bone lysis is characterized by one large area of lysis.
geographic lysis
This type of bone lysis is characterized by many small-medium size lytic areas. The pattern is regional and the lytic areas may have indistinct margins. There may be a long transition zone.
Moth-eaten lysis
This type of bone lysis is characterized by pinpoint areas of lysis which are indistinct and fade into normal bone. A transition zone is NOT apparent.
permeative lysis
T/F: Permeative lysis is usually due to a malignant tumor.
True
T/F: most lesions will have a mixed pattern of lysis.
True
How does one make an assessment of a mixed pattern of bone lysis?
Based on the most aggressive characteristic of the lysis
What is a periosteal reaction?
A healing response which occurs when the periosteum is elevated from the bony cortex by blood, pus, neoplastic tissue, granulomatous tissue, edema, or simply stripped from the cortex during trauma or surgery.
How many layers are in the periosteum? What are they?
1. outer fibrous layer
2. inter cambian layer
This layer of periosteum has osteogenic properties.
cambian layer
What are Sharpey's fibers?
Fibers along which new bone forms from the cambian layer of periosteum
How are periosteal reactions categorized by?
aggressiveness, activity, duration
What are 3 classifications rating the aggressiveness of periosteal reactions?
1. non-aggressive
2. semi-aggressive
3. aggressive
T/F: Aggressiveness of a periosteal reaction is not necessarily synonymous with malignant.
True
A _____ _____ lesion will lift the periosteum away from the cortex faster and farther leaving a larger space for the bone to fill in and therefore, produce a more interrupted/spiculated appearance.
more aggressive
An ______ periosteal reaction will have a distinct margin.
inactive
_____ periosteal reactions have a fuzzy, indistinct margin in which the edge of the periosteum may be difficult to identify.
Active
The ________ of a periosteal lesion can be estimated by the relative opacity of the periosteal reaction.
duration
A young periosteal reaction will have the opacity of this.
soft tissue
As a periosteal lesion ages, it will become more _____ and _____ like.
dense, bone
This periosteal reaction can be lifted from the cortex and new bone completely fills the space between the cambian layer and the cortex.
solid (homogenous)
If the surface of a homogenous periosteal reaction is smooth and has a clear margin, what is its classification and why?
nonagressive & inactive b/c the lesion is healed or nearly healed
Solid periosteal reactions usually signify _____ disease.
benign
This periosteal reaction is layered like an onion.
Lamellated
What does a lamellated periosteal reaction indicate?
A cyclic/intermittent elevation of the periosteum.
A lamellated periosteal reaction usually indicates a _________ lesion and can be seen with forms of osteomyelitis and some tumors.
semi-aggressive
This type of periosteal reaction is caused by the periosteum being elevated from the cortex faster than it is able to fill in below the periosteum.
spiculated periosteal reactions
In spiculated periosteal reactions, along what will the bone form?
Sharpey's fibers
In spiculated periosteal reactions, what can keep bone from filling in the space between the spicules?
pus, granulomatous tissue or tumor cells
This periosteal reaction usually indicates a semi-aggressive or aggressive lesion.
spiculated periosteal reaction
T/F: long thin spicules indicate a less aggressive process than short thick spicules.
False: short thick spicules indicate a less aggressive process than long thin spicules
Why might a spiculated periosteal reaction have a sunburst appearance?
-the periosteum is being elevated from a local point by a rapidly enlarging lesion, such as a tumor.
-may also occur when the periosteum is elevated over the rounded mass.
-also, b/c the new bone grows perpendicular to the periosteum.
A sunburst appearance of a periosteal reaction indicates a _______ process.
aggressive
This type of periosteal reaction represents a disease process that is expanding very rapidly. It may break through the periosteum and may destroy the forming bone spicules.
Amorphous periosteal reaction
Translate "amorphous periosteal reaction"
An periosteal reaction w/o form
Describe the appearance of new bone in amorphous periosteal reactions.
clumps, clouds, or wispy strands that may intermingle with a spiculated pattern.
What is the usual cause of an amorphous periosteal reaction?
a bone tumor
T/F: there are often areas of bony lysis associated with amorphous periosteal reactions.
True
This is a tringular cuff at the edge of an aggressive periosteal elevation.
Codman's triangle
In Codman's Triangle, is new bone growth solid or does it show evidence of lysis?
It is usually a solid reaction
What is degenerative joint disease usually caused by?
It is usually secondary to trauma or an abnormal joint
What are some possible etiologies of DJD?
trauma, infection, excessive activity, faulty conformation, or faulty gait
What does DJD stand for?
Degenerative Joint Disease
What clinical features are associated with DJD?
-a primary cause
-slow onset, but progressive in nature
-intermittent lameness
-acute lameness assoc. with inflammation of the synovial tissues
This type of swelling is seen with acute inflammation or synovitis of joints.
intracapsular soft tissue swelling
What is "joint effusion"?
intracapsular soft tissue swelling
What is the primary location of joint effusion?
Centered on the joint space, but may displace fat pads at times.
What can happen to joint space in DJD? Why?
The width of the joint space can decrease due to destruction of the articular cartilage.
What are osteophytes?
new bone
What do periarticular osteophytes result from? Why do they form?
Articular cartilage proliferation in non-weight bearing areas of a joint in an attempt to stabilize the joint.
What is the pathogenesis of periarticular osteophyte formation?
1. excessive buildup of cartilage will outgrow the ability of the synovial fluid to supply sufficient nutrients
2. The cartilage will die.
3. Blood vessels will invade the dead cartilage
4. The dead cartilage will be replaced by bone
When will osteophytes be apparent on radiographs?
After they ossify
Where do perichondral osteophytes form, what are they formed from, and what is their shape?
location: chondrosynovial junction
formed from: fibrocartilage
shape: a collar at that junction
Subchondral osteosclerosis is evident as _____ opacity of the subchondral bone and can be due to _______ of trabeculae.
increased, hypertrophy
Subchondral osteosclerosis is associated with _____ disease.
joint
What is usually associated with the direct bone-on-bone contact of subchondral osteosclerosis?
loss of articular cartilage
What are enthesophytes?
New bone projections at the attachment of a ligament or joint capsule to bone. = spurs
What is enthesis?
the attachment of soft tissue to bone
Elevation of the periosteum at the joint capsule attachment results in the formation of this.
bone spur = enthesophytes
In a joint, what soft tissues can be mineralized?
joint capsule and ligaments
What can cause subchondral osteolysis?
infection, immunological disorders, excessive wear, degenerative joint disease
This is characterized by decreased opacity in the subchondral bone that can be caused by necrosis of bone following loss of articular cartilage.
subchondral osteolysis
This can be formed by proliferative synovium invading the subchondral bone.
subchondral bone cysts
Where are subchondral cysts commonly seen?
in the canine stifle in the intercondylar region
What are joint mice?
A detached fragment of articular cartilage that may mineralize if it is invaded by blood vessels.
T/F: Joint mice are occasionally observed in the joint.
True
This may arise from an avulsed fragment of articular cartilage (OCD) or chip fractures.
joint mouse (mice)
Which screen-film systems are satisfactory for most spinal studies?
high speed, rare-earth
Why is higher output equipment preferable for neuroradiography?
higher mAs and kVp capabilities
What is a good starting point for neuroradiography? Why?
-survey radiographs
-they themselves might be diagnostic, or provide information about useful follow-up techniques
When should patients who need neuroradiography not be put under general anesthesia?
-medical contraindications
-patient self protection (i.e. spinal fracture-luxation instability)
-some follow-up studies
Why is the spinal cord not visible on survey radiographs?
It is low density and surrounded by bone.
How is spinal cord diseases inferred from radiographs w/o contrast studies?
changes in the bony vertebral column
What is sectional radiography of a small animal spine dependent on?
clinical localization of a suspected lesion
T/F: initial radiographs should be made on an entire spinal section (C or T-L or L-S).
True. Follow-up radiographs that are well collimated, more detailed can be centered on questionable areas for further assessment.
For spinal radiography, when small animal patients are placed in lateral recumbency, _____ to _______ traction is applied to ______ and _____ in positioning.
slight to moderate,
maintain and assist
T/F: When a small animal is placed in lateral recumbency for spinal radiography, the spine should be parallel with the table.
True
For spinal radiographs in small animals, it is especially important that the ______ section of the spinal column be _____ to the table.
cervical, parallel
What is necessary to avoid in order to achieve true lateral radiographs of the spine?
-avoid rotational obliquity,
-don't view the whole spinal column in one radiograph - instead center study on problem areas.
For spinal radiography, which position is preferred, VD or DV? Why?
VD because that positions the spinal column closest to the film, and allows better alignment of the spine (w/o curvature or obliquity).
How can you recognize a true VD?
Assess whether the spinous processes are projected end-on and whether the sternum and spine are superimposed.
T/F: due to normal kyphotic-lordotic curvature of the spine intervertebral disk spaces and vertebral end-plates are never uniformly projected.
True
How can good geometric projection of the intervertebral disk spaces of the C-spine and L7-S1 space be obtained?
By angling the x-ray beam slightly from caudal to cranial when making a VD view of the spine.
Narrow, deep chested breeds have large differences in _______ (____) between T vs. L vertebral segments and between _______ vs. _______ regions of C spine.
thickness (depth)
cranial vs. caudal
What techniques may be necessitated when taking VD spinal radiographs of narrow, deep chested breeds?
-different exposure techniques for the same section
-use the heel effect
For which section of the spine, are oblique views especially useful for? Why?
-C-spine
-They provide better visualization of intervertebral foramina C2-3 thru C7-T1 without superimposition of articular processes.
What radiographic view allows the dens to be visualized?
Obliquity of C1-C2 20 degrees from lateral.
What is the general vertebral formula (for dogs)?
C7:T13:L7:S3:Cdx
What density are intervertebral disk spaces and intervertebral foramina?
soft-tissue density
T/F:vertebrae are normally positioned in smooth continuous alignment with relatively gradual curves.
true
T/F: Bone vertebrae should normally be smooth and sharply marginated
true
In which section of the spinal column are articular processes large and have a tendency to obscure intervertebral foramina on the lateral view?
cervical
Which section of the spinal column tends to have narrow intervertebral disk spaces?
Thoracic, thru T9-T10
Which section of the spinal column tends to have large intervertebral disk spaces?
lumbar
Why might the vertebral bodies of L3 and L4 be irregular and indistinct?
Due to attachment of the diaphragmatic crura.
Small Animal: Generally vertebrae are narrower, longer, and finer in appearance in the ____ vs more squared in the _____.
cat, dog
What 7 things should specifically be looked for when interpreting a spinal radiograph?
1. number of vertebrae in the section
2. Alignment of vertebral bodies & vertebral canal
3. Changes in size, shape, and opacity of vertebral canal
4. Changes in size, shape, and opacity of each intervertebral disk space
5. Vertebral bodies, pedicles, laminae, and processes for changes in geometry and opacity
6. Morphology and opacity of vertebral end plates
7. Articular facets for sizes of joint spaces
What is myelography?
spinal radiography following the introduction of CM into the spinal subarachnoid space.
This procedure is used to provide visualization of the contour of the spinal cord, since it is not visible on survey radiographs.
myelography
T/F: Myelography will continue to be widely used in veterinary hospitals and private practice.
False: it is being replaced more and more with CT and MRI even though it is still a valuable technique for understanding spinal cord compressive morphology.
T/F: Myelography can only be performed when fluoroscopy is available to guide the needle.
False: Myelography can be readily performed w/o fluoroscopy, but it is greatly enhanced by fluoroscopy.
What are the two CMs that are preferred for myelography?
iohexol and iopamidol
These are newer generation, non-ionic, organic, iodinated contrast media with less frequent and less severe side effects than former media. (Used for myelography)
iohexol and iopamidol
what injection site is used for most myelographs?
L5-6 or L4-5.
For what procedure should the animal's head be elevated when finished? Why?
Myelography. To minimize the CM around the brain.
What are 2 severe complications that might result from myelography?
1. apnea
2. seizures
How might you avoid apnea when doing myelography?
Avoid making the injection too rapidly.
When might seizures occur that result from myelography?
Following anesthetic recovery.
The ________ space is thin and thus not visible entirely as a sheath of contrast medium encircling the spinal cord.
subarachnoid
If the spinal cord is normal, columns of CM are relatively _____ and run _____ thru the course of the vertebral canal.
thin, uniformly
Where does the spinal cord start to narrow?
around L5
For which regions is myelography an unreliable technique for finding compressive spinal cord lesions?
Caudal to L6
This artifact may occur from direct injection with needle tip misplacement or leakage from the subarachnoid space thru the needle tract after removal of the needle.
CM in the epidural space
What is the appearance of CM in the epidural space?
Uneven, irregular columns of CM and large volumes may exit vertebral column via nerve root sheaths.
What are 5 artifacts that could occur in myelography?
1. epidural CM
2. L Venous sinuses
3. CM in Central canal
4. Air Bubbles in subarachnoid space
5. incomplete filling (due to curvatures of the spine)
What are 3 general patterns that describe abnormalities noticed with myelography?
1. extradural
2. intramedullary
3. intradural-extramedullary
This type of lesion is peripheral to the dura and is visible with myelography.
extradural
In myelography, this type of lesion causes a deviation of the column of CM away from bony margin of the vertebral canal and is usually associated w/ thinning of the CM column and narrowing of the spinal cord.
extradural
What are 4 examples of extradural lesions?
1. herniated intervertebral disk
2. hyperplastic ligaments
3. vertebral neoplasia
4. hematoma
This type of lesion is a focal enlargement of the spinal cord.
intramedullary
What is epidurography?
Myelography, except that it is used to evaluate compressive lesions caudal to L6, and it is injected into the spinal epidural space instead of the subarachnoid space.
T/F: In epidurography, CM columns are relatively wider than in myelography and are uniformly shaped.
False: In epidurography, CM columns are relatively wider than in myelography and are NONuniform.
T/F: 2 radiographic views should always be used for epidurography examinations.
False: Only a lateral view needs to be made; a DV view can be made, but it requires additional injection and is of little value
Why are undulations and irregular pooling normally seen in epidurography?
due to epidural fat
What is a major abnormal change that may be seen in epidurography?
focal indentation/deviation w/ thinning of CM column
What is percutaneous puncture?
Placement of a needle into an intervertebral disk space or vertebral body by a percutaneous approach using fluoroscopic guidance
For what 2 procedures is percutaneous puncture used?
1. disk aspiration
2. biopsy
How would a DVM obtain a sample of an intervertebral disk in order to do a culture/sensitivity test for diskospondylitis?
percutaneous puncture
T/F: To obtain a quality image of the entire equine cervical spine, it is necessary to take 2-3 radiographs with overlapping fields.
True
When might an equine C-spine have a mild stair-step presentation b/w adjacent vertebrae?
When the neck is flexed
What are ratios used to measure in spinal radiography of equines?
Ratios of measurements describing intravertebral and intervertebral sizes are used to suggest whether or not the cervical spinal cord may be reliably compressed.
T/F: neural elements of the skull are visible on survey radiographs.
False: They are not visible
Without special procedures, neuroradiographic diagnosis is based indirectly on recognition of _____ ______.
skull abnormalities
Name the positions that a dog's head can be placed in for survey radiography of the skull.
1. lateral
2. VD/DV
3. Lateral oblique
4. Open Mouth VD: Nasal
5. Frontal: Rostro-Caudal
6. Fronto-occipital
7. Foramen magnum
8: Rostro-Caudal open mouth (Basilar)
On a survey radiograph of a dog skull, what should be noted about the neurocranium?
size, shape, and relative opacity
What is the normal appearance of tympanic bullae?
Thin-walled, smoothly marginated bony rim, interior is relatively radiolucent, bilaterally symmetric