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28 Cards in this Set
- Front
- Back
- 3rd side (hint)
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How does a line voltage compensator work? |
keep supply voltage constant. mains power supply voltage can fluctuate. BY CHANGING THE NUMBER OF TURNS OVER WHICH THE INPUT VOLTAGE IS APPLIED |
BY CHANGING.. THE # |
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GRID TUBES COMPARED TO STANDARD TUBE |
The focusing cup is given a very strong bias (voltage) in a standard tube the focusing cup has a fixed bias voltage |
focusing cup |
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Benefit/disadvantage of grid tube when used as a switching device |
can provide very fast switching of the x ray beam. can only be used with a tube current less that 500mA |
500 mA |
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what happens to thyristor to stop a circuit? |
at the end of exposure a negative signal is send to the control of the thyristor. whichever thyristor is conducting will finish its half cycle and then the power is terminated from the xray unit due to the negative control signal |
Neg control signal |
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thermal cut outs |
switches off sections of the unit if a present temp is reached. prevents over heating |
sections switched off |
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anode rating chart |
allows operator to determine whether the exposure is "safe" prevents tube from over heating |
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slipping clutches |
stops the tube/equipment when it senses a obstructing object. protects both patient and radiographer |
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mobile radiography practices |
min pt exposure max distance protection for people who cant be moved working in a enviroment not designed for x rays remove unnecessary personal |
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Mammography vs General x ray equipment |
Smaller focal spot. target is molybdenum anode is grounded tube tilted |
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Smaller focal spot. target is molybdenum anode is grounded tube tilted how does these things benefit mammo? |
1= because we are x raying much finer anatomy structures. 2= molybdemum provides the low energry x rays photons that are required 3=so not to attract off axis electrons therefore increase the size of focal spot 4=vertical edge of x raybeam so we do not x ray chestwall |
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focal spot changes in relation with receptor. effect of image res |
smaller focal spot at ANODE side. the image resolution increased towards anode side. smaller anatomical features match with the small focal spot. nipple alligned with anode side. |
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multi field image intensifier (DEFINITION) |
Allows the use of 2 or 3 different diameter input phosphors. |
diameter phosphors |
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advantage to multi field image intensifier |
allows area to be magnified- if smaller input phosphors is used as the size of the output phosphor remains the same |
magnified. output the same |
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disadvantage to multi field image intensifier |
ABC will increase mA to produce the same brightness on image. otherwise image would have quantum mottle. increase in brightness (mA) increase in dose. |
ABC-mA |
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purpose and how an ABC device works |
Automatic brightness control maintains brightness of fluoroscopic images. by monitoring the intensity of the output phosphor changes mA to maintain this level |
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purpose of input phosphor |
converts x rays into light photons 1 x ray lots of light photons |
x rays lightphotons |
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purpose of photocathode |
converts light into electrons 1 light into lots of electrons |
light electrons |
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purpose of electrostatic focussing lenses |
confines the electron beam accelerates electron beam |
electron beam |
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purpose of output phosphor |
converts electrons into light photons 1 electron into lots of light photons |
electrons light photons |
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continuous vs pulse fluro (30 frames) |
continuous-always exposing through scan time. pulse- pulses of exposure at a rate of 30 pulses per second. ` |
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exposure time for Continuous fluro vs pulse (30 frames) |
1=0.333 s or 33 mS 2=0.1 s or 10 mS |
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advantage of pulse fluro |
less chance of patient movement die to reduce exposure time. less patient dose. |
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disadvantage to pulse fluro |
if the frame rate of the monitor is greater than the pulse rate of the x ray unit we get "Flickering" |
flickering. |
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list of equipment DSA |
CCD ACD |
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CCD |
positioned at exit of output phosphor of II. converts light into electrical signals |
output phosphors. light--electrical signals |
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ACD |
positioned between CCD and computer system. converts analogue signal into digitial signal |
analogue digital |
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Computer system |
After ACD displays and stores image. |
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Laser camper |
after computer system. writes image to film |
image--film |
