Ch13: AEC Flashcards
What is the function of the Automatic Exposure device? (AEC)
exposure is terminated when the AEC chamber reaches a certain radiation amount
absorbs remnant radiation exiting the patient
What technical factor varies with AEC
time
What is minimum response time?
the minimum amount of time required for the equipment to complete an exposure
What is back up time?
maximum amount of time an exposure can run before being terminated
safety feature built into equipment
150-200 percent of expected time for set mAs
Describe density controls when using AEC
the tech can adjust the amount of radiation the chambers will receive to terminate the exposure, allows the exposure to run longer or shorter than program
Usually a -2, -1, +1, +2
if routinely used, means issue with machine
explain the importance of appropriate detector selection
if wrong one is set, can run an exposure indefinitely
exposure time will hit back up time and shut off b/c chosen AEC/IR is not receiving xray radiation
what factors affect image quality when using AEC
patient size
part
density
pathology
OID
SID
collimation
define anatomically programmed radiography
What do you do if minimum response time is too short (in the case of peds)?
Use a free detector
use a fixed technique
Define Minimum response time
shortest possible exposure time that a machine needs to make an exposure
Can vary with equipment, (0.001 s)
Define Ionization Chamber
chamber/cell in front of the image receptor that measures the amount of exposure the IR is receiving
What is another name(s) for ionization chamber?
AEC cells
photo-timer
radiation detectors
How many AEC cells are on a typical bucky?
3-5
What is a benefit to having a back up timer?
prevents overexposure of a patient
prevents the equipment from overheating
all good in case the tube is aligned to the wrong bucky
Why do you need to watch closely your EI?
digital imaging causes the image on the screen to seem okay, but the EI can still be too high or low
