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50 Cards in this Set
- Front
- Back
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components of xray system
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wall switch
x ray tube control panal power supply |
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control panal
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used to select exposure settings
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power supply
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receives standard AC from the wall swithch, converts it into DC and provides voltage according to the exposure selected that energizes the x ray tube
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direct current
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E- flow in one direction only
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alternating current
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E- flow in alternating directions
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what does control panal consist of?
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main on/off swith
exposure button timeer mA and kVp xray emission light |
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standard x ray production
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60 cycles/ sec
110 or 220 volts |
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what increases or decreases voltage
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transformers
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process of conversion of AC to Dc for x ray
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rectification
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what type or rectificaion are most waves?
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half wave, self rectifying. only half a cycle is used to produce an x ray
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constant potential machines
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use full wave rectificaion
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full wave rectificaion
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conventional 60 cycle AC hi voltage current is repaced with hi frequency power supply or constant potential is created between anode and cathode
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advantages of full wave rectification of a constant potential machine
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longer scale contrast and low pateint dose
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how are xrays produced
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by electric current
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electic current
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flow of e- in a conductor
use amperes most dental machines operate between 7-15 mA |
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what does flow of e- depend on
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prssure of voltage (volts)
ristance of conductor to the flow of electir current (ohms) |
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potential difference or voltage
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difference in elecrical potential energy between two points due to the excess of e- at one point relatie to another
volts |
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kVp (dilovolt peak)
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peak voltage or potential difference between anode and cathode reached during a cylcle
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electron volts
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actual kinetic energy of a cathode electron traveling from cathode to anode
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components of xray tube head
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metal house
immersion oil x ray tube unlad glass window aluminum filter lead collimator BID transfomer |
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components of xray tube head
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transformer and the x ray tube lie within the xray tueb head and an insultaing material surround transformer
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why are xray tube and transformers immersed in oil/
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for insulation, cooling, and prevention of spard from one component t oanother the tube head
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coolige tube
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xray tube
evacuated lead glass within tube head has anode and cathode |
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what does xray cathode consist of?
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tungsten filament generates e - when heated
and molybdenum focusing cup |
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what does xray anode consist of?
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tungsten target in an copper stem. Target converts enery of e- from filament into xray photon
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how is x ray insuffeint?
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99% heat only 1% photon
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Why is tungsten used?
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hi melting pt
hi atomic number low vapor pressure hi thermal conductivity |
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why is tungsten embedded in a copper stem at anode/
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because copper is a good thermal conductor and reduces the risk of target melting
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small area on the target with most e- strike to make xray
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forcal spot on anode
the smaller the focal point, the sharper the image |
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anode position vs cathodes
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anode target is angled 15-20 degrees to cathode to reduce the actural focal spot
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actual focal spot
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rectangular in shape
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effective focal spot
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source of radiation, appears square when vein within x ray beam
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line focus princple
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method of reducing the actual focal spot sinze on target in x ray tubes of angling the target to get a smaller effective focal spot thean actual focal spot causing sharper image
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primary functions of power supply
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lo voltage current to heat x ray tube filament, to genterate a hi difference between anode and cathode by hi voltage transfomrer
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transformer
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change V from low to hi or hi to lo wo loss of energy
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transformer components
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copper wrappeed around opposed ends of iron core
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Step up transformers
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more turns in secondary coil
increase voltage decrease current |
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step down transformers
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fewer turns in secondary coil
decrase voltage increase current |
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purpose of step down transformer
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reduce voltage of AC to 10 V and incrase current to 3-6 ameres to heat filament
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what regulates step down transfomere
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mA swithch, regualtes temp of filament and filament is source of e-
the hotter the filament the greater the number of e- |
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what is required to acclerated e- from cathode to anode to create x ray?
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hi voltage
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what selctes voltage?
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kVp. it applies voltage to hi end transformer
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autotransformer
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converts primary voltage from input source into the secondary voltage
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types of exposure timers
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mechanical and electronic
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x ray timiing circuit
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delays start of exposure time for half sec, actual time of exposure, seconds or impuslses
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the longer the exposure. . .
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the grater the number of x rays produced
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most xray machine timers
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60 cycles, Ac, half way, self rectified
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what controls number of e-
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mA
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what controls x ray phonton spped, enery and tissue penetration?
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kVp
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what is x ray exposure time
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mA
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