Image Production - Automatic exposure control
What is the back up timer response time?
1 ms (0.001 second)
What is the variance allowed in automatic exposure control (AEC) detector consistency?
No more than 30% difference in pixel values
Does AEC help with contrast?
No, just mAs
when using AEC what is selected to fine tune for differences in field size?
Optical density
This term refers to the shortest exposure time that the system can produce
minimum response time
What is the shortest exposure time that an automatic exposure control (AEC) system can produce?
minimum response time
what technique factors does AEC use?
Uses a fixed kVp and machine controls mAs.
Which may be used as the typical backup settings for automatic exposure control (AEC)?
1.5 times the expected exposure time or 150%-200%
Changing +/- controls on the AEC allows exposure times to be increased or decreased, each step normally represents how much of a change in receptor exposure?
25%
what are regulations requirements if the AEC fails to terminate exposure?
A 600 mAs safety override
Which image quality factor is more consistent when automatic exposure control (AEC) is used to produce an image?
Exposure receptor
Which technical factor is controlled by automatic exposure control (AEC)?
Exposure time
Which component of a radiographic imaging system measures the quantity of radiation that reaches the image receptor?
Automatic Exposure Control (AEC)
Which term refers to the exposure detectors located between the patient and the image receptor (IR
Automatic Exposure Control (AEC)
This refers to the maximum length of time the x-ray exposure continues when using an AEC system
Backup timer
What does AEC require be selected for part being imaged?
Correct ionization chambers
What action is important when using automatic exposure control (AEC)?
Correctly position the part over the selected detector
What type of device is AEC considered?
Entrance type devices
What does AEC rely so patient is overexposed or underexposed?
Excellent position skills and that that part being imaged is positioned over the ionization sensors.
Phototimer AEC are consider what type of devices?
Exit-type devices because the detectors are positioned behind the IR
(often referred to as "density control") allows the radiographer to adjust the pre-programmed radiation detection values of the AEC system
Exposure adjustment control
Which automatic exposure control (AEC) feature is used to adjust image receptor exposure based on patient factors?
Exposure adjustment control
What changes result in a decrease in exposure time when using automatic exposure control (AEC) to produce a radiographic image?
Increase in kV and mA. Decrease in grid ratio.
This allows the radiographer to adjust the amount of preset radiation detection values
density controls
What measures the amount of radiation transmitted to the IR?
detectors
The automatic exposure control (AEC) is a device that measures the quantity of radiation that reaches what structure?
image receptor
This is a hollow cell that contains air and is connected to the timer circuit via an electrical wire
ionization chamber
Which type of detectors are most commonly used in automatic exposure control (AEC) system?
ionization chambers
This is important for selecting while using AEC for anatomical part
kVp
Which control can be used to accommodate any unusual patient characteristics or to overcome slowly changing calibration or sensitivity of the automatic exposure control (AEC)?
optical density
This is an electronic device that converts visible light energy into electrical energy
photomultiplier tube
This uses a fluorescent screen and a device that converts the light to electricity
phototimer
What does automatic exposure control (AEC) measure?
predetermine electrical charge (Ionization)
What does AEC control reaching the IR?
quantity of radiation
Varying kVp does what when using AEC?
results in faster or shorter exposure times.
what does the backup timer do in the event of AEC malfunctioning?
terminates the exposure, preventing patient from being overexposed.
