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4 Cardiac Modulated mA
The goal of Cardiac AEC modulation with the cardiac scan modes, similar to AEC modulation
for non-cardiac modes, is to deliver a patient exposure that is appropriate to the combination of
the patient attenuation and the diagnostic imaging task. In AEC with Cardiac mode, the
advantages of patient-specific exposure modulation control, and the scanning and image
reconstruction techniques unique to cardiac imaging mode combine to enable low dose cardiac
imaging of the patient.
Similar to other AEC-related scan modes, a scout of the patient is required when using AEC
with Cardiac modes. The AEC feature then uses the patient attenuation information extracted
from the scout and combines this unique information with the user-prescribed scan parameters
contained in the protocol to derive an appropriate scan technique. Similar to standard AEC
mode, a user-prescribed Noise Index is the scan parameter input that plays the major role in
determining the final patient exposure solution derived by the feature. In general, a higher Noise
Index results in a reconstructed image dataset with higher overall image noise but at a lower
patient exposure; conversely, a lower Noise Index results in lower overall image noise but at the
cost of generally higher overall patient exposure. The user must balance the competing
requirements of image noise and patient dose to arrive at a Noise Index that accomplishes the
diagnostic imaging task at a dose that is as low as reasonably achievable.
In ECG-gated mA modulation for cardiac, the AEC algorithm determines the required peak mA
of the exposure profile to satisfy the user requested Noise Index for the reconstructed image.
The peak value is derived from the patient attenuation information extracted from the scout
projections, combined with the user requested scan parameters.
The AEC algorithm recognizes the fact that the user is in cardiac mode and adjusts the scan
technique for an equivalent non-cardiac AEC scan to account for the unique challenges
imposed by cardiac scan acquisition and reconstruction techniques.
See
Scan
chapter for detailed information on non-Cardiac AEC.
Revolution CT User Manual
Direction 5480385-1EN, Revision 1
Chapter 13 Cardiac 355