Aec Considerations Of Patient Size, Shape, Composition, And Age; Dynamic Aec Scanning; How To Tell If The Dose Has Changed; Summary - GE Revolution CT User Manual

2.4.7 AEC considerations of patient size, shape, composition, and age

For a given AEC image noise/quality criterion setting, larger patients and more attenuating body
regions may result in a higher scanner radiation output. Smaller patients and less attenuating
body regions may result in a lower scanner radiation output.
While AEC can be an effective dose-reduction tool for pediatric patients, special care should be
taken with this patient group. The GE Healthcare online education module available on the
Image Gently website describes issues to consider when using our AEC features with pediatric
patients.

2.4.8 Dynamic AEC scanning

When a scanning protocol contains multiple X-ray tube rotations at the same table location, the
effect on patient dose of incorrect selection of protocol settings will be multiplied by the number
of rotations. For such protocols, operators must take extra care when setting manual mAs or
AEC parameters to achieve the desired level of image noise/quality criterion. For example, in
perfusion scanning, the image noise can often be much higher (yielding a lower dose) than for
routine diagnostic scanning of the same region because the primary application of perfusion
scan data is for quantitative analysis and characterization of perfusion parameters rather than
for diagnostic visualization. The manufacturer's reference protocol provides an indication as to
whether use of AEC is or is not recommended with these scan modes.

2.4.9 How to tell if the dose has changed

For every patient, and any time AEC settings are changed, in order to confirm a correct level of
scanner radiation output for that patient's size and exam protocol, users should examine the
projected CTDI
confirmation of system settings. When a large patient is scanned at a particular setting of image
noise/quality criterion, the CTDI
AEC settings. Projected CTDI
the user interface prior to confirmation of settings for scanning. After scanning, the values are
updated to reflect the average of the actual mAs values used in the scan and are displayed on
the user interface as well as recorded in the DICOM secondary screen capture and DICOM
radiation dose structured reports.

2.4.10 Summary

AEC is a versatile and powerful tool designed to tailor the scanner's radiation output to each
patient based on the patient's size, age, shape and attenuation and the user's requested level of
image noise/quality criterion. AEC technology uses estimated patient attenuation values to
adjust the mA dynamically in order to achieve the requested level of image noise/quality
criterion. However, AEC settings must be chosen with the same care used to choose all other
parameters that affect radiation dose to the patient. Before the scan parameters are confirmed,
careful attention must be paid to CTDI
radiation output associated with the prescribed protocol must be checked and confirmed prior to
scanning. Used properly, AEC is a key technology to help ensure that the appropriate radiation
dose is used for every patient.
Chapter 11 Scan
and DLP displayed prior to performing the scan, as a step in operator
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and DLP will be higher than for a smaller patient at the same
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and DLP values are displayed on the scanner's dose display on
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and DLP displayed on the user interface; scanner
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