Operating instructions

HeartView CT
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Temporal Resolution
Temporal resolution, also called time resolution, repre-
sents the time window of the data that is used for
image reconstruction. It is essential for cardiac CT
imaging. The higher the temporal resolution, the
fewer the motion artifacts. With the SOMATOM Sensa-
tion Cardiac, for example, temporal resolution down to
83 ms (depending on the scanner) can be achieved.
Technical Principles
Basically, there are two different technical approaches
for cardiac CT acquisition:
• Prospectively ECG-triggered sequential scanning.
• Retrospectively ECG-gated spiral scanning.
In both cases, an ECG is recorded and used to either ini-
tiate prospective image acquisition (ECG triggering), or
to perform retrospective image reconstruction (ECG
gating). Only scan data acquired in a user-selectable
phase of the cardiac cycle is used for image reconstruc-
tion. The temporal relation of the image data interval
relative to the R-waves is predefined, which can be
either relative (given as a certain percentage of the RR-
interval time) or absolute (given in ms) and either for-
ward or reverse.