Snapshot Freeze - GE Revolution CT User Manual

7 SnapShot Freeze

The SnapShot Freeze (SSF) feature can be utilized to reduce coronary artery motion artifacts
that may occur in cardiac exams. SSF is an available recon option with cardiac axial scanning,
for both Hi Res and non-Hi Res acquisition modes.
When SSF reconstruction is selected, a special 3-phase image series is generated for
subsequent motion correction processing on the AW workstation (or AW Server) with the
CardIQ Xpress Process application.
SSF is prescribed at a specified target phase location appropriate for coronary imaging. In the
case of higher heart rate exams, you may, for example, wish to prescribe SSF at both a 75% R-
to-R target phase (mid-diastole) as well as a ~45% R-to-R target location (approximate end-
systole).
All Cardiac Axial scan acquisitions are inherently SSF compatible, meaning that for at least the
target phase location corresponding to the center of the acquisition window, SSF is available.
However, when prescribing an acquisition with a given phase range (70-80% R-to-R for
example), if coronary motion correction is also desired across this full phase range, ensure that
Widen for SSF is explicitly enabled as part of the scan Acquisition Window prescription
(Otherwise, in the example above, SSF recon may only be available at the 75% phase
location.).
Constraints
SnapShot Freeze is not available with the following:
•
Cardiac Axial PLUS mode reconstruction
• 0.625 Z, overlapped reconstruction 2.5 mm
•
DFOV < 15cm
•
ASiR-V 90-100%
• Multi-phase reconstruction
Considerations
• Appropriate cardiac target phase selection (mid-diastole and/or end-systole) is essential for
optimal performance.
• Ensure a sufficient acquisition phase range for the anticipated SSF target phase(s). For
ease of use, utilize the
•
For a single-beat/single-table position acquisition, position the heart well within the wide-
coverage Cardiac Axial scan.
•
For an acquisition series that requires more than one axial scan location given clinical
coverage needs (perhaps a bypass graft assessment for example), ensure that the native
coronaries are well within the coverage of one axial scan to prevent having a higher motion
vessel near an axial scan boundary.
•
Avoid an excessive image noise level. Select the appropriate kV / mA technique (using the
AEC Noise Index parameter) for optimal performance, and utilize ASiR-V as needed.
Chapter 13 Cardiac
Widen for SSF option within Auto Gating.
Revolution CT User Manual
Direction 5480385-1EN, Revision 1
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