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xray boards

radiation factors

QuestionAnswer
what quantity of radiation exposure to the reproductive organs is required to cause temporary infertility? 200 rad
what dose of radiation can cause menstrual changes in women and decrees the number of sperm in a man? 10 rad
what dose of radiation will cause sterility? 500 rad
focal spot blur is greatest where? directly along the course of the central ray
what is the fx of the fixer? * remove the unexposed silver bromide crystals * harden the emulsion
darker image means more optical density
as SID decreases, exposure rate _____ (inc or dec) increases
as SID decreases, optical density ____ (inc or dec) increases
T/F: female oogonia reproduce only during fetal life true
T/F: male spermataogonia reproduce continuously true
T/F: both male and female stem cells reproduce only during fetal life false; male repro continuously, female only during fetal life.
what is the annual dose-equivalent limit for the skin and hands of an occupationally exposed individual? 50 rem
what is the annual dose-equivalent limit for the lense of the eye of an occupationally exposed 15 rem
how many rem per quarter? 3 rem
no more than __ rem in a year 5
which of the following will require an increase in x-ray photon energy/pemetration? * fobrisarcoma * osteomalacia * paralytic ileus * ascites ascites: body tissue density has increased, in the others it has decreased
what is the formula for finding ESE? rad / time = x / 1 min
what is the device that directs the light emitted from the image intensifier to varous viewing and imaging apparatus? beam splitter
what influences geometric unsharpness? OID SOD SID
as OID increases, magnification ____ (inc/dec) increases
OID is directly or indirectly related to magnification? directly
as focal object distance and SID are inversely proportional or directly porportional? inversley
as focal onject distance and SID decrease, magnification ____ increases
what is base-plus fog small amount of measurable density on unexposed and processed film. it is a result of environmental, background radiation that is present during film manufacture, transport, and storage
what contributes to base-plus fog? chemical fog base tint background radiation
which portion of the characteristic curve would most likely represent a density of 1.0 straight-line portion
what is the characteristic cureve used to predict? the speed, contrast, and exposure latitude of a particular film emulsion
what does the the toe of the characteristic curve represent immediately after base-plus fog
what does the shoulder portion of the characteristic curve represent Dmax
what effect wil a stained intensifying screen have on the finished radiograph? decreased density:
patient does increases as fluoroscopic FSS increases FSS decreases FOV increases FOV decreases FOV decreases
the shorter the SID, the ____ the skin dose greater
high kVp _____ skin dose decreases
radiation output from the diagnostic xray tube is measured in what units? roentgen
what is a rad? radiation absorbed dose it measusres the energy deposited in any material
what is rem? radiation equivalent man it includes relative biologic effectiveness
Becqueral the SI unit of measurement for radioactivity
if a large quantity of radiation is delivered to a body over a short period of time, the effect_____ will be greater than if it were delivered in increments
exposed silver halide crystals are changed to balck metallic silver by what? reducers
what keeps the emulsion swelling to a minimum? hardner
what is hydroquinone and phenidone? automatic processor developer agents
what provides the necessary alkalinity for the developer solutions? activator
how does the use of rare earth intensifying screens contribute to lowering the pt dose? it permits the use of lower mAs
delivery of large exposures to a cold anode, or the use of exposures exceeding the tube limit may casuse: cracking the anode rotor bearing damage
if you can't achieve a short OID, what can you do to minimize magnification? a longer SID
what is the approximate intensity (quantity) of scattered radiation at 1 m from the patient? .1% the entrance dose; if the entrance dose for this image is 320mR, then the intensity 1m from the pt is .32 mR
what is the source of electrons withing the xray tube? thermionic emissions
why is filtration added to the xray beam? to porduce an xray beam with higher average energy;
what is the filtration on the primary beam? 2.5mm Al
what amount of the filtration of the beam is accounted for in the glass envelope .5 mm Al
what amount of filtration does the collimator provide? 1.0 mm Al
what 3 methods of filtration are considered inherent filtration? primary beam glass envelope collimarot
in digital imaging, xrays form an ______ ______ on the image receptor electronic image
what are the 4 tanks in the processor? 1. developer 2. fixer 3. wash 4. dryer
what happens in the developer tank? the exposed silver bromide crystals are reduced to black metallic silver
what happens in the fixer tank? the unexposed silver grains are removed from the film by the clearing agent
what happens in the wash section? the chemicals are removed from the film to preserve the image
what are stochastic effects of radiation? genetic alterations carcinogenesis nonthreshold and randomly occuring effevts
the chance occurance of stochastic effects is directly related to the ____ ____ radiation dose
what are nonstochastic effects of radiation? predictable, threshold responses; a certain amount of radiation must be received before the effect will occur, and the greater the does, the more sever the effect
primary radiation barriers must be at least how high? 7'
off-focus or extra focal radiation may be minimized by ____ restricting the x-ray beam as close to its source as possible
the annual limit for occupationally exposed individuals is valid for what type of radiations? beta, x, and gamma radiations
the ratio between the height of the lead strips and the width of the distance between them grid ratio the thickness of the strips is unrelated to the grid ratio
what is the formula for grid ratio height of strips devided by the distance apart
which cell type has the least radiosensitivity in the adult human? nerve cells
which cell type has the greatest radiosensitivity in the adult human? lymphocytes
the atomic number (Z) of the tissues is directly related to it's ______ _______ attenuation coefficient
differential absorption contirbutes to the various shades of ____? gray on the finished xray image
air has an effective Z number of _____ 7.78
fat has an effective Z number of 6.46
water has an effective Z number of 7.51
muscle has an effective Z number of 7.64
bone has an effective Z number of 12.31
what is the formula for pixel size? FOV / matrix size
if the matrix size is increased, the pixel size is ______ decreased
if the FOV increases, the pizel size ______ increases
pixel size is directly or inversley related to resolution inversley
as pixel size increases, resolution ______ decreases
grid cut off due to off centering would result in ____ overall loss of density
photoelectric effect a relatively low-energy photon uses all its energy to eject an inner-shell electron, leaving a vacancy. An electron from the shell above drops down to fill the vacancy, and in doing so gives up a characteristic ray. most harmful to patients, trsfd to tis
compton scatter a high-energy incident photon ejects an outer-shell electron. In doing so, the incident photon is deflected with reduced energy, but it usually retains most of its energy and exits the body as an energetic scattered ray.
thompson scatter another name for classical scatter
what are examples of primary barriers? lead walls and doors
primary barriers must be how high, and how many inches thick? 7' high, 1/16th" thick (1.5mm)
what is secondary radiation? leakage or scattered radiation
what are examples of secondary radiation barriers? portions of the wall above 7' the control booth
what is the required thickness of secondary radiation barriers? 1/32th" o
what is the single most important factor regulating rad contrast is? kVp the lower the kVp, the shorter the scale of contrast
the lower the kVp, the _____ the scale of contrast shorter
what is the primary source of scattered radiation? the patient
as the size of the irradiated field decreases, scattered radiation production and patient hazard ______ (inc or dec) decreases
if the amount of scattered rad decreases, then the radiographic contrast is ____ (ligher or lower) higher (shorter scale)
long scale low contrast
short scale high contrast
what voltage ripple is produced by single-phase equipment? 100% voltage ripple
what is a photon the smallest quantity of any type of electromagnetic radiation
the Hz stands for ___ and represents _____ Hertz cycles per second 1 Hz = 1 cycle/s
what determines the quantity of flourescent light emitted from a flourescent screen? thickness of phosphor lyer type of phosphor used kV range used
effective dose equivalent whole body dose
spinning top test to test timer efficiency full wave = 12 dots at 1/10s, 6 dots at .05s 10 dots at 1/12s, 3 dots at .025s for 3 phase, the size of the arc is measured and equated to exp time
rare earth phosphurs gadolinium lanthanum yttrium (musch faster than calcium tungstate)
using a rare earth phosphors allows the radiographer to use _______ significantly lower mAs
what unit of measure expresses the amoung or energy deposited in tussue? Rad (Gy) the unit of absorbed does
quantity of ionization in the air roentgen
radiation dose to biologic material rem
inverse square law as the distance btwn the radiation source and the IR decreases, the exposure rate increases
inverse square law formula old mAs/new mAs = old distance / new distance
Voltage ripple the percentage drop from maximum voltage each pulse of current experiences
controlled area 1. that is occupied by people trained in radiation safety. 2.that is occupied by people who wear radiation monitors. 3.whose occupancy factor is 1.
The use of which of the following is (are) essential in magnification radiography? 1. High-ratio grid 2. Fractional focal spot 3. Direct exposure film Fractional focal spot
Pair production an interaction that occurs only at energies of 1.02MeV, and therefore it does not occur in daig rad
classical scatter a low-energy photon interacts with an atom but causes no ionization; the incident photon disappears into the atom, and is then immediately released as a photon of identical energy but changed direction.
Occupational exposure received by the radiographer is mostly from Compton scatter.
The high-voltage, or step-up, transformer functions to increase voltage to the necessary kilovoltage It decreases the amperage to milliamperag
one of the biggest advantages of CR/Dr is lattitude
CR relationship between the exposure given the photostimulable phosphor (PSP) and it's resulting luminescence linear
what affects recorded detail on traditional film/screen imaging FSS SID OID film/screen speed motion
the effect of focal spot size is principally on ____ ____ radiographic sharpness
according to the NCRP, the whole body dose equivalent limit is 50mSv 5 rem 5000 mrem
according to the NCRP, the annual whole body dose equivalent for students under the age of 18 yrs 1 mSv 100 mrem .01 rem
The annual occupational dose equivalent limit for the lens of the eye, a particularly radiosensitive organ, is 150 mSv (15 rem or 15,000 mrem)
The annual occupational dose equivalent limit for the skin and extremities is 500 mSv (50 rem or 50,000 mrem
The total gestational dose equivalent limit for embryo/fetus of a pregnant radiographer 5 mSv (0.5 rem or 500 mrem
The device used to test the accuracy of the x-ray timer is the spinning top
line focus principle illustrates that as the target abgle decreases, the effective focal spot size decreases, providing improved recorded detail
steep, small target angle increases or decreases the heel affect? increases
LET refers to the rate at which energy is transferred from ionizing radiation to soft tissue
as screen speed in increased, exposure factors must be ______ to maintain the original image dinsity? decreased. a change from 100 to 200 speed usually requires the mAs be halved. 400 to 200 would require twice the mAs
As the CR laser scanner recognizes various tissue densities, it constructs a graphic representation of pixel value distribultion called a histogram
sensitometry method of quality control for daily monitoring of the automatic film processor
densitometer a device used to read optical density
crossover rollers should be cleaned daily to prevern accumulation of crystallized solution on the rollers
what is needed to construct a sensitometric curve pentrometer densitometer
pentrometer aluminum step wedge used
brensstrahlung radiation A high-speed electron entering the tungsten target is attracted to the positive nucleus of a tungsten atom and, in the process, is decelerated
Created by: jenorton1