AEC Assignment
Phototimer AEC devices convert the radiation to light energy.
True
The amount of electric charge produced in an AEC detector depends on the amount of radiation absorbed by the detector.
True
When using AEC, the exit radiation is converted into an electrical signal.
True
Which of the following is the most critical aspect of successfully performing an examination using AEC?
centering the anatomy of interest over the selected detector(s)
The primary purpose of AEC is to:
control the amount of radiation reaching the IR (Although AEC can result in reduced patient exposure, its purpose is to control the amount of radiation reaching the IR.)
If the back-up time is shorter than the actual exposure needed for a properly exposed image:
the image receptor will be underexposed (If the back-up time is too short, the exposure will terminate prematurely, resulting in the IR being underexposed.)
Once the electric charge from an AEC detector reaches a preset level:
the exposure will stop
The original type of AEC detector was the:
phototimer
The shortest exposure time that a radiographic tube with AEC can have is the:
minimum response time
When the radiographer has the opportunity to set the back-up time, it should be approximately _____ of the expected exposure time.
150%
There is typically a configuration of at least ___ AEC detectors in place.
3
If the back-up time is set by the equipment, the exposure time should end when the mAs reaches:
600
All APR settings use the AEC.
False
If an AEC has three detectors, only one of the three can be selected for an exposure.
False
It is safe to assume that APR setting have been developed to produce the best quality images with the least amount of exposure.
False
Once a part has been selected using APR, the exposure factors can NOT be adjusted.
False
The mAs readout is of little value to the radiographer.
False
Using the plus or minus density controls should be done frequently to produce optimal images with AEC.
False
These can be adjusted to increase or decrease the amount of radiation needed to terminate the exposure using AEC.
Density controls change the exposure time by a specific amount.
Using a higher kVp during an AEC examination results in:
a shorter exposure time (Higher kVp allows more radiation to penetrate the part and reach the AEC detector, reducing the time of exposure. With higher kVp, the patient exposure is reduced.)
An ionization chamber is a hollow device that contains:
air
When your patient for an AP abdomen is very large, using AEC will result in:
appropriate exposure to the IR (Assuming all is set up correctly, AEC should not terminate the exposure until the preset level is reached, regardless of the patient's thickness.)
With digital imaging using AEC, if an AP thoracic spine is imaged using an outside instead of center detector, the brightness in the area of interest will be ______ and the quantum noise will be ____. (Assuming all other factors are appropriate)
appropriate; increased
With digital imaging using AEC, if an AP thoracic spine is imaged with the density setting changed form 0 to -2, the brightness in the area of interest is ____ and the ____ is increased. (Assuming all other factors are appropriate)
appropriate; quantum noise
What does AEC stand for?
automatic exposure control
The maximum length of time that an exposure lasts when using AEC is the:
back-up time
When a patient for a unilateral AP hip image has a metal prosthesis covering the detector, how will the bony anatomy appear with CR/DR imaging?
dark (Because the detector is covered by metal, it will be very difficult for the detector to measure enough exit radiation to terminate the exposure. The patient and the IR will be overexposed.)
When using AEC with digital imaging, errors resulting in an overexposure to the IR result in:
images with appropriate brightness, overexposed patients (Typically the computer can compensate for overexposure to the digital IR, displaying an image with appropriate brightness. However, the overexposure to the patient cannot be adjusted and it is up to the radiographer to use the AEC system properly)
Using a lower mA station during an AEC examination results in:
increased exposure time (Lowering the mA does not affect the mAs but does result in an increase in exposure time so the detector has time to reach its preset level.)
Today's AEC system is most likely to use a/an:
ionization chamber
When using AEC, the kVp:
is set as appropriate for the study
When using AEC , the radiographer is responsible for determining:
kVp
The actual amount of exposure used for an image when AEC is being used is the:
mAs readout
The device that converts the light energy to an electrical signal is the:
photodiode, photomultiplier tube
The two types of detectors used in AEC are:
phototimers and ionization chambers
Anatomically programmed radiography (APR) is a system in which the radiographer selects:
preset settings based on the part being imaged
The reason to have a back-up time is to:
protect the patient from excessive radiation, keep the tube from excessive heat-loading
When there is a significant amount of scatter radiation reaching the detector, the exposure time will be:
shorter than needed
If the radiographer is doing an upright chest using AEC but the table bucky is selected:
the back-up time will be reached, the patient will be exposed to excessive radiation, the IR will be overexposed (If the AEC detectors in the table are waiting to get enough radiation to terminate the exposure, they will never get to that point if the tube is directed at the upright bucky. The result will be a very long exposure (probably the back-up time being reached) and excessive mAs used.)
If the AEC detectors are not completely covered by the part being imaged and are exposed to primary radiation:
the exposure will terminate very quickly
If the patient for an AP thoracic spine is centered so that the spine is not over the top of the detector:
the image will be too light (If the spine is not over the top of the detector, then the lung is, allowing the radiation to easily penetrate and the exposure to terminate quickly. The result is that the lungs are correctly exposed but the spine is underexposed, producing an overall light image.)
The detector(s) selected for an image should be:
the ones that are superimposed by the anatomic structure of interest
The AEC minimum response time may cause a problem when:
the patient is unable to hold still for the exposure
The predetermined level of radiation exposure needed to terminate the exposure when using AEC is set by:
the people who service the equipment
AEC controls the amount of radiation reaching the IR by controlling the:
time of exposure
With digital imaging using AEC, if an AP thoracic spine is imaged with the density setting changed from 0 to +2, the brightness in the area of interest will be ____ and the exposure time is ____. (Assuming all other factors are appropriate)
unchanged; longer
With digital imaging using AEC, if an AP thoracic spine is imaged using 110 kVp instead of the appropriate 80 kVp, the brightness in the area of interest is _____ and the patient exposure is _____. (Assuming all other factors are appropriate)
unchanged; lower
AEC devices should be calibrated:
when the unit is first installed, at regular intervals, when there is a change in the type of IR being used
