Appendices Flashcards
Units for:
absorbed dose
dose equivalent
absorbed dose = rad (or Gy)
dose equivalent = rem (or Sv)
___ is the SI unit of absorbed dose.
One is equal to 1 joule/kg = 100 rad
Gray (Gy)
1 Gy = ? rad
100
___ is the special unit of absorbed dose.
One is equal to 100 erg/gram or 0.01 joule/kg or 0.01 Gy
Rad
1 rad = ? Gy
0.01
Rem is the special unit of ___.
any of them quantities expressed as a dose equivalent
1 rem = ? Sv
0.01
Dose equivalent in rems = ? x ?
absorbed dose in rad x quality factor
What is the SI unit of any quantities expressed as dose equivalent?
Sv
What is the Quality factor (Q) for x-, gamma, or beta radiation?
1
What does rad stand for?
Radiation Absorbed Dose
Dose rate is expressed in ?/?
Absorbed dose rate is expressed as ?/?
rems/hr
rad/hr
Relationship between intensity and distance of the x-rays:
The intensity of radiation varies ____ with the ____.
inversely
square of the distance
“Inverse square law”
Using the inverse square law, when the distance from an x-ray source is doubled, what happens to the intensity?
What happens if the distance is reduced by half?
reduces to 1/4 of the original
intensity quadruples
___ is the collision between an x-ray photon and an inner orbital electron of an atom which results in the electron getting kicked out of orbit and the photon losing its energy
photoelectric effect
What is the photoelectric effect?
the collision between an x-ray photon and an inner orbital electron of an atom which results in the electron getting kicked out of orbit and the photon losing its energy
___ is the interaction of an x-ray photon with an outer shell orbital electron of the absorber atom which produces a recoil electron and a photon energy which is less than that of the incident photon.
Compton scattering
In Compton scattering does the x-ray photon interact with inner or outer orbital electron?
outer
In photoelectric effect, is the x-ray photon interacting with inner or outer orbital electron?
inner
What is the final result of Compton scattering?
Energy is lost
a recoil electron is produced which has a lower photon energy than that of the incident photon
___ is where the incident photon is annihilated in the vicinity of the nucleus of the absorbing atom with subsequent production of an electron and positron pair.
Pair production
What are the three methods by which energy is lost from an x-ray?
photoelectric effect
Compton scattering
pair production
The photoelectric effect is the most important at (high/low) energies which are utilized to produce fluoroscopic images
low
(up to 100 kVp)
The HVL (half-value layer) is used in determining which two things?
- quality (average penetrating ability of the x-ray beam)
- barrier thickness (amount of shielding needed to attenuate radiation to the required degree)
What is the quality of an x-ray beam?
the average penetrating ability
___ is the thickness or layer of a specified material which attenuates the x-ray beam to such an extent that the exposure is reduced to one half.
HVL
(half-value layer)
HVL is usually expressed in what units?
Barrier thickness is expressed in what units?
HVL = mm aluminum
Barrier = mm lead (or other specific material)
Deep dose equivalent
external, whole-body exposure
the dose equivalent at a tissue depth of 1cm
Dose equivalent to an embryo/fetus during entire pregnancy of occupationally exposed person should not exceed ___.
0.5 rem (5 mSv)
Once pregnancy is known, radiation dose of embryo/fetus of occupationally exposed person should be no greater than ___ rem in any month.
0.05 rem in any month
The main purpose of gonad shielding is to protect the gonads from exposure to the ___ when the gonads are within the limits of the ___.
primary x-ray beam
properly collimated x-ray beam
Are flat contact shields a good gonad shield for fluoro?
No
Is a shaped contact shield a good gonad shield for fluoro?
Yes
it stays put when repositioning
Is shadow shield a good gonad shield for fluoro?
No
but is good for sterile field and incapacitated pts
The energy imparted by ionizing radiation per unit mass of irradiated material
absorbed dose
The sum of the individual doses received in a given period of time by a specified population to a specified radiation source
collective dose
The product of the absorbed dose in tissue, quality factor, and all necessary modifying factors at the location of interest
dose equivalent
Health effect, the severity of which VARIES with the dose and for which a threshold IS believed to exist.
Nonstochastic effect
Health effects that occur randomly and for which the PROBABILITY of the effect occurring (not its severity) is assumed to be a linear function of dose WITHOUT threshold.
Stochastic effects
Annual whole body occupational dose limits
5 rems
Total filtration: at least ___mm Al equivalent or HVL must be at least ___mm Al at normal operating voltage
2.5
2.5
These restrict the useful beam to less than the size of the barrier.
Collimators
adjustable diaphragms, shutters
Collimators must provide the same degree of protection as the ___.
tube housing
Bucky slot cover must be ____ thick.
0.25 mm lead equivalent
For how long should written records of repairs and/or maintenance of the x-ray equipment be kept?
3 years
What test/s are the phantom and penetrometer (aluminum step wedge) used to run?
to test the brightness/contrast optimization of the TV monitor
How often should you test the brightness/contrast optimization of the TV monitor?
Each day before the first exam
Interlocks should provide what?
protection from accidental exposure to operators when a barrier is not in place or not centered to the primary beam
What is a penetrometer?
aluminum step wedge
What is a nominal focal spot?
the manufacturer’s stated anode target size
___ is the projected focal size measured along the central axis of the x-ray tube at the image receptor
measured focal spot
___ is the length and width of the x-ray beam as projected down the central axis of the x-ray tube
effective focal spot
What is the actual focal spot?
the actual area on the anode that is struck by the x-ray beam
For under the table tubes, maximum intensities are received below the tabletop at angles of ___ and ___ degrees.
In above the table, ___ degrees is where the most intensity is received.
135, 120
30
Minimum intensities are receive at scatter angles of ___, ___, and ___ in that order.
45, 60, 90
For all types of radiologic procedures, what are the 3 general actions for reducing radiation dose exposure?
- eliminate medically unnecessary procedures
- Process films properly
- have a quality assurance program
___ is a barrier to attenuate the useful beam.
___ is a barrier to attenuate stray radiation.
primary protective barrier
secondary protective barrier
___ is the term for all the radiation which passes through the window, aperture, cone or other collimating device of the tube housing
useful beam
___ is radiation not serving any useful purpose (includes leakage and secondary radiations)
stray radiation
What are all the types of radiation detected by a film badge? (5)
x-rays
gamma
beta
thermal neutrons
fast neutrons
Range for a film badge
0.0 - 700 rad
Minimum energy detected for film badge for gamma and beta rays
10 keV for gamma
200 keV for beta
Does a film badge provide a permanent record?
YES
How can a film badge produce a false reading?
heat, pressure, certain vapors
What types of radiation does a TLD detect? (5)
x-ray
gamma
beta
thermal neutrons
fast neutrons
Range of a TLD
10 mrad - 10^5 rad
Minimum energy detected for a TLD
10 keV
Is a TLD reusable?
Yes
Biggest advantage to pocket ionization chamber monitor?
Quick information available (immediate)
Range of pocket ionization chamber monitor for x-rays
0.001 - 200 mrad
What is an aberration?
an undesirable characteristic of a lens or optical system preventing exact reproduction of the original subject
___ is the energy imparted by ionizing radiation per unit of mass of irradiated material.
absorbed dose
What material is one of the best absorber of x-rays?
lead
___ is the part of the television scanning system used to reproduce the subject
active trace
___ is the unit of electrical current that determines the quantity of x-rays produced at the anode (target) of the x-ray tube
ampere
___ is also referred to as the target.
anode
The anode is usually composed of ___
tungsten
When electrons accelerated from the cathode hit the anode, what happens to them?
their kinetic energy is converted to x-rays
___ appears as small, dark spots on the output screen of the image intensified tube.
image intensifier tube artifact
___ is the process by which an x-ray beam of radiation is reduced in intensity by absorption or scattering when passing through material.
attenuation
The Law of Bergonie and Trubondeau states what?
the radiosensitivity of tissues depends on:
- the number of undifferentiated cells it contains
- the degree of mitotic activity in the tissue
- the length of time the cells of the tissue stay in active proliferation
The basic principle of the Law of Bergonie and Tribondeau is that the more ___ the tissue, the greater the radiosensitivity.
undifferentiated the cell line within
Where is the blind spot within the eye?
where the optic nerve enters the retina
___ is the electrode in the x-ray tube from which electrons are emitted.
cathode
___ Gy = ___ rad
0.01 Gy = 1 cGy = 1 rad
___ is what graphically demonstrates the relationship between the density and radiation dose
characteristic curve
A closed circuit is the distribution of television signal by means of ___.
coaxial cable or microwave
___ is a highly corrected lens used to collect light from some source and project it into space as a family of parallel-light beams
collimating lens
___ is a device for restricting/ confining/limiting a beam of radiation within an assigned solid angle
collimator
___ is transmitted from the camera and consists of video, blanking, and synchronizing pulses
composite video signal
What is a compression cone?
attachment used in fluoro of the GI tract
permits examiner to apply pressure to various parts and displace some overlying structures to improve visualization
Compton effect/scattering is an interaction between an incoming x-ray photon and an (inner/outer) shell electron
OUTER
What happens in Compton scattering after the x-ray photon interacts with the outer shell electron of the atom?
the photon surrenders a portion of it kinetic energy to dislodge the electron from its orbit
it then continues on its way but in a new direction
___ accounts for most of the scatter radiation produced in diagnostic studies
Compton effect
In the eye ___ cells allow us to see light, while ___ allow us to see color.
rods = light
cones = color
Contrast for modern image intensifiers exceeds __ : __
15 : 1
The absorption of x-rays in barium and iodine is much (less/greater) than that in bone and tissue.
Why?
greater
because contrast has higher atomic numbers
What is a dead-man switch?
constructed so a closed-circuit contact can only be maintained by continuous pressure by the operator
___ is film blackening or the amount of light transmitted through the film.
density
___ is the allowable out-of-focus condition in the image plane that may be tolerated and still maintain a specific resolving power
depth of focus
What would a 100% duty factor indicate?
continual usage
___ is the section of a photomultiplier tube in which secondary electrons are emitted, thus providing amplification
dynode
___ is the sensitive layer of photographic film that contains tiny crystals of a silver compound embedded in a layer of gelatin
emulsion
The F-number denotes the relative speed of ____.
It is equal to its ___ divided by its ___.
a camera lens
focal length / diameter
Flux gain is an increase in ___ expressed as a ratio of ___.
of light photons at the output screen : # light photons produced at the input phosphor
output image brightness from an image intensifier
___ is the apparent size of the radiation source when viewed from the central axis of the useful radiation beam
effective focal spot
___ is when the circular image is entirely within the rectangular frame.
Underframing
___ is when the entire rectangular frame is filled with the circular image extending beyond the edges of the fram
overframing
___ is the original method for expressing the increase in luminescence of the image intensifier tube as compared to a standard fluoro screen
gain
___ is the average of all gamma measurements in the diagnostic density range for x-ray films
average gradient
___ is the SI unit of absorbed dose
Gy
Generally, the higher the grid ratio, the (better/worse) the scatter and the (higher/lower) the pt radiation dose.
better
higher
___ is a grid that does move during an exposure to eliminate blur/grid lines form the image.
___ is a grid which does not move during the exposure.
Bucky
Stationary grid
___ was established in 1928 and prepares recommendations to deal with the basic principles of radiation protection.
International Commission on Radiological Protection
(IRCP)
An image intensifier converts an x-ray image into ___, then to ___ then back to a ___ of smaller size and increased brightness.
a light image
an electron image
a light image
Inverse square law
the intensity of the radiation is inversely proportional to the square of the distance from the source
___ is the factor used to correct idealized vertical resolving power to that which would be realized in actual usage.
Generally taken to be ___.
Kell Factor
0.7
___ determines the maximum penetrating ability of x-rays and refers to the “quality” of x-rays
kVp
Lag is an undesirable quality of most ___.
vidicon (television) tubes
___ is the ratio of the image size to the object size.
lateral magnification
Longer latitude films have (lower/greater) contrast
lower
Line Pair unit is used to express ___ or ___.
resolution
resolving power
The Linear Hypothesis implies what?
any amount of radiation can cause some damage
___ is the units used to express the electron current flowing across the x-ray tube from the cathode to the anode.
mA
___ is the increase in output image brightness from an image intensifier tube that results from reduction in image size.
minification gain
___ is the nonprofit corporation concerned with the scientific and technical aspects of radiation PROTECTION.
National Council on Radiation Protection and Measurements (NCRP)
Does the severity of the resulting health effect varying mean it’s stochastic or nonstochastic?
Nonstochastic
___ is an object used to simulate the absorption and scatter characteristics of the pt’s body for radiation measurement purposes.
phantom
A photocathode is a material rich in ___ that can be made to emit ___ under that action of incident light.
electrons
electrons
___ is a type of vacuum tube used to achieve electron gains.
photomultiplier
Entrance vs exit pupil
The image of the limiting aperture in a lens of optical system…
Entrance: formed by all of the optical elements AHEAD of that limiting aperture
Exit: formed by all the lenses BEYOND that limiting aperture
___ is the modifying factor used to derive dose equivalent from absorbed dose.
Quality factor (Q)
The quantum sink of a correctly tuned fluoroscopy system with closed-circuit TV camera is what?
x-ray photons absorbed by the image intensifier input phosphor
___ is the measure of the deficiency of conversion of incoming x-ray photons to light photons
quantum yield
___ is an instrument used to expose film to precisely controlled steps of increasing light intensity
sensitometer
___ is a radiograph taken during a fluoroscopic exam for the purpose of providing a permanent record of an area of interest or to verify the filling of a void with contrast media
spot film
Do stochastic or nonstochastic effects occur randomly in nature?
stochastic
Are cancer and hereditary effects stochastic or nonstochastic?
stochastic
___ is the operation of camera shutters at the same frequency as x-ray pulses
cinefluorography
the x-ray tube target is the ___
anode
___ is a dose monitoring system utilizing certain inorganic crystals such as LiF.
TLD
Minification gain x flux gain = ?
total brightness gain
A video camera tube converts a ___ into a ___.
visible image
electronic signal
Equation for pixel size
Pixel size = FOV / matrix
