Chapter 10: Image Acquisition
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Automatic Exposure Control (AEC)
The Automatic Exposure Control automatically terminates an X-ray exposure to produce optimum qual-
ity images. AEC automatically compensates for changes in patient thickness, opacity, and different tech-
nique 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 under-
exposed images. Conversely, positioning the heaviest patient area over the receptor sensing area may
cause overexposed image areas. You should become familiar with the size and location of each receptor.
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.
Acquisition Screens
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.
Figure 10-18
Example AEC setup of a normal chest exposure
