Helical; Cardiac Axial - GE Revolution CT User Manual

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Detector coverage: 40, 80, 120, 140, 160 mm
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Variable image thickness selections: 0.625, 1.25, 2.5, and 5.0 mm
• Sample rates: 984 Hz-8571Hz
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Revolution CT can acquire up to 512 axial slices per rotation

5.5 Helical

Helical imaging features:
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All kV and mA stations available, dependent on generator and tube limitations
• Maximum scan time: 60 seconds
•
Rotation speeds: 0.28, 0.35, 0.5, 1.0 second
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Detector coverage: 40 mm, 80 mm
• Variable image thickness selections: 0.625, 1.25, 2.5, 3.75, and 5.0 mm
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Sample rates: 984 Hz-8571 Hz
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Pitches: 0.516:1, 0.984:1, 0.992:1, and 1.375:1
Helical Image Interval
The system has the ability to generate diagnostic images at small spacing for helical scan
mode. Images can be reconstructed at a minimum interval of 10% of the reconstructed slice
thickness. The average number of slices (images) per gantry rotation is calculated by dividing
the total number of reconstructed slices (images) by the number of rotations during the data
acquisition.

5.6 Cardiac Axial

Cardiovascular imaging utilizes ECG-gating to target specific phases of the cardiac cycle, and a
weighted reconstruction algorithm to increase temporal resolution. In this mode, projection data
is acquired for at least one rotation, with an effective image temporal resolution of approximately
half of the gantry rotation time.
Cardiac Axial acquisition is a prospectively ECG-gated scan mode, where the heart rate is
monitored and the R-Peak triggers the acquisition of data for a specified range of phases in the
cardiac cycle (using R-peak to R-peak phase percent or ms after R-peak). The system coverage
of up to 160 mm at one table location is enough to cover many cardiovascular applications in a
single scan. However, if more than one table location is required, the system will determine
required collimations and table locations based on user specified scan range, scan field of view,
the primary recon display field of view (DFOV), and image offsets (A/P and R/L). The system
also allows the user to control the amount of scan overlap based on user selection (min,
medium, or full) to balance image quality and dose (see User Manual for description of these
settings).
The Heart Rate Variation Allowance parameter (specified in BPM, typically based on the
maximum beat to beat variation during a short breath-hold) can be used to increase the scan
duration in order to ensure requested phases are acquired in the presence of heart rate
Chapter 21 General Information
Revolution CT User Manual
Direction 5480385-1EN, Revision 1
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