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xray boards
radiation factors
| Question | Answer |
|---|---|
| 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
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