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Exposures- Ch.33 AEC

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kkaitlyn96's version from 2017-04-02 17:13

Section 1

Question Answer
AECAutomatic exposure control
AEDAutomatic exposure device
AEC and AED does whatmeasures radiation reaching IR, when amt is reached, exposure is terminated
When was AEC and AED introduced?1942
When AEC is being used what can and cannot be controlled by the technologist?mAs cannot be controlled, mA can be controlled
Ionization chamber configurationcenter, left, right chambers
What are the types of AED's?Photodetector, Ion chamber, Solid state detector
memorize

Section 2

Question Answer
What is the order of the patient, detector and IR when using a photodetector?pt, IR, detector
What does a photodetector use?crystals to emit light through photoemission
What is the process of a photodetector?screen absorbs photons and release light, light goes to photomultiplier/photodiode, makes electrons ands sends electrons to a capacitor, once it gets to a preset value it then terminates the exposure
What does the photodetector measure?What exits the IR
The light quantity is proportional to ___the quantity of photons
Why does the detector need to be placed underneath the IR?photoemission sensors are not radiolucent
electrical signal=photons
memorize

Section 3

Question Answer
What is the order of the patient, chamber, and IR when using ion chambers?pt, chamber, IR
What type is the ion chamber?entrance type
What does the ion chamber contain and why?gas or air to read the ionization (voltage) of the photons
What is the process of the ion chamber?When radiation interacts with gas/air it frees electrons, the electrons get attracted to wire and create and electrical charge that travels to the timer circuit when the timer circuit has enough it terminates the exposure
Why can the chamber be placed before the IR?it is radiolucent
electrical signal=radiation recieved
memorize

Section 4

Question Answer
What does the solid state detector used?silicon/ germanium crystals
What does the solid state detector do?measures the amount of radiation that passes through the crystals, when they receive enough they terminate the exposure
Density controlsadjustment of radiation recieved, changes are usually in increments of 25%
When should density controls not be used?part thickness or kVp changes
Ionization cells- When more than one cell is activated what cell will have the most influence on density?Cell receiving the most amount of radiation
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Section 5

Question Answer
Subject densityimpact patient has on IR density exposure
Subject contrastdifference in tissue contrast
Increase in anatomy tissue, AEC does what?overexposure
If an area of interest is denser than surrounding areas then the image will be _________ with AECunderexposed with improper positioning
Sm. collimation = more dense= ___exposureoverexposure
lg. collimation= _________ scatter= ___ exposureunderexposure
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Section 6

Question Answer
Minimum time responelength of time needed for the AEC to respond to ionization and to send a signal to terminate the exposure
AEC's have a minimum response time of ___.001sec
Exposures that last less than .001 sec will result in overexposure
Backup timermaximum exposure time for a system
Backup timer LawGenerators terminate at 600mAs when kVp is above 50
The backup timer should be set ___% the manual exposure150-200%
memorize

Section 7

Question Answer
APRAutomatically Programmed Radiography
What is APRAEC system combined with technique chart computerized, and pre programmed selection of exams and positions
Is AEC repeatable?No
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