Review Article
Cardiac CT: How much can temporal resolution, spatial resolution, and volume coverage be improved?

https://doi.org/10.1016/j.jcct.2009.04.004Get rights and content

Abstract

In this article, we review the current status and discuss potential further improvements and limitations of system parameters relevant for cardiac CT, in particular spatial resolution, temporal resolution, and volume coverage.

Section snippets

Challenges for cardiac CT

Scan data acquisition in computed tomography (CT) imaging of the heart is controlled by the patient's electrocardiogram (ECG) to provide images in the same relative phase of the cardiac cycle. Cardiac CT requires high temporal resolution, ie, short exposure time of the individual images, to avoid image distortion by cardiac motion. Excellent spatial resolution (at best submillimeter) is a prerequisite for adequate visualization of the heart's small anatomical structures, such as the coronary

Spatial resolution

The in-plane spatial resolution of a CT system is limited by the number of active detector channels in a detector row and by their aperture, ie, the width of each individual detector channel. With 700–900 detector channels covering a scan field of view (SFOV) of usually 500 mm, the in-plane sampling distance, ie, the distance between 2 detector channels, is 0.56–0.71 mm in the isocenter of the scanner. Modern CT scanners use techniques such as quarter detector offset or in-plane flying focal spot

Temporal Resolution

In ECG-synchronized cardiac MDCT, scan data acquisition and image reconstruction are controlled by the patient's ECG. In prospectively ECG-triggered sequential CT, the patient's ECG signal is used to trigger axial scans at different z-positions (different anatomical levels) with a user-defined temporal offset relative to the R waves.25, 26 A volume image of the heart consists of several image slabs reconstructed from axial scan data acquired in multiple consecutive heart beats. The number of

Volume Coverage

With typical MDCT detector z-coverages of 40 mm and recently up to 80 mm (the z-direction is the patient's longitudinal direction), an ECG-synchronized volume image of the heart still consists of several image slabs reconstructed from data acquired in multiple consecutive heart beats (Fig. 6 and Fig. 7). As a consequence of insufficient temporal resolution and variations of the heart motion from one cardiac cycle to the next, in particular in the case of arrhythmia, these image slabs can be

Conclusion

We presented various approaches to improve temporal resolution, spatial resolution, and volume coverage in ECG-synchronized cardiac CT, and we discussed the technical and practical limitations. Technical progress alone, however, does not necessarily translate into better diagnostic or prognostic value of cardiac imaging or into improved patient outcomes. Complementary to the ongoing refinement of imaging techniques clinical studies are required as a basis for establishing cardiac CT in routine

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    Conflict of interest: The authors are employees of Siemens Healthcare, Forchheim, Germany.

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