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Chapter 7:
Automatic Exposure Control (AEC)
The Automatic Exposure Control automatically terminates an X-ray exposure to produce optimum
quality images. AEC automatically compensates for changes in patient thickness, opacity, and different
technique factors of mA, kVp, and SID. Proper patient positioning is very important. In extreme cases of
misalignment, some radiation bypasses the patient and ends the exposure prematurely, causing
underexposed images. Conversely, positioning the heaviest patient area over the detector sensing area
may cause overexposed image areas. You should become familiar with the size and location of each
detector. With such knowledge, you can develop proper positioning techniques of each anatomical area
and be able to duplicate your positioning for every patient. This also helps you produce uniform quality
images regardless of patient thickness or opacity. This system feature, AEC, automatically selects the
mAs and exposure time, eliminating the need for you to select them.
Many default techniques are AEC based in order to optimize image processing. The exposure time and
mAs are automatically selected when you are in AEC mode, producing uniform quality images.
Topics covered include:
•
Acquisition Screens
•
Ion Chamber Detectors
•
Applications for Detector Sensing Areas
•
AEC Limitation Messages
•
Acquire AEC Images
Acquisition Screens
Figure 7-1 shows an example of an AEC exposure setup. For AEC mode, exposure time and mAs are not
selectable; therefore, these parameters are empty on the Acquisition screen. This example provides an
example an AEC exposure with Chest AP selected.
Definium 5000 X-Ray System
Operator Manual
(p. 7-1)
(p. 7-4)
(p. 7-4)
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5197809-1EN
© 2008 General Electric Company. All rights reserved.
Chapter 7: Automatic Exposure Control (AEC)
Rev. 4 (13 February 2008)
7-1
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