Elsevier

Academic Radiology

Volume 10, Issue 4, April 2003, Pages 386-401
Academic Radiology

Special Report
Advances in Cardiac Imaging with 16-Section CT Systems

https://doi.org/10.1016/S1076-6332(03)80027-2Get rights and content

Abstract

Rationale and Objectives

The authors present advances in electrocardiographically (ECG) gated cardiac spiral scanning with recently introduced 16-section computed tomographic (CT) equipment.

Materials and Methods

The authors discuss the technical principles of ECG-gated cardiac scanning. They give an overview on system properties and on the detector design. They describe ECG-gated scan- and image-reconstruction techniques and ECG-controlled dose modulation (“ECG pulsing”) for a reduction of the patient dose. They discuss key parameters for image quality and present simulation and phantom studies and they give preliminary values for the patient dose.

Results

An extension of the adaptive cardiac volume reconstruction for ECG-gated spiral CT provides adequate image quality for up to 16 sections. With the smallest reconstructed section width (about 0.83 mm) and overlapping image reconstruction, cylindrical holes 0.6–0.7 mm in diameter can be resolved in a transverse resolution phantom independent of the heart rate. For coronary CT angiography, the influence of transverse resolution is most pronounced for coronary segments that are only slightly tilted relative to the scan plane. In this case, visualization of stents and plaques is considerably improved with 1.0-mm or smaller section width. For 0.42-second gantry rotation time, temporal resolution reaches its optimum (105 msec) at a heart rate of 81 beats per minute. Effective patient dose for the standard protocols recommended by the manufacturer ranges from 0.45 mSv (male) for ECG-triggered calcium scoring to 7.1 mSv (male) for high-resolution ECG-gated coronary CT angiography. With ECG pulsing, the dose is reduced by 30%–50% depending on the patient's heart rate.

Conclusion

Clinical experience will be needed to evaluate fully the potential of 16-section technology for cardiac imaging.

Section snippets

System Properties and Detector Design

Until 2001, 0.5-second gantry rotation was the limit for commercially available CT systems. The CT scanner we evaluated for cardiac applications additionally offers 0.42-second gantry rotation to improve the temporal resolution of images. Like some commonly used four-section CT systems (23), this scanner has an adaptive array detector, which consists of 24 detector rows. The 16 central rows define a 0.75-mm collimated section width in the center of rotation, and the four outer rows on both

Image Quality and Artifacts

Recent publications (21, 30) have demonstrated that consideration of the cone-beam geometry becomes mandatory for general-purpose CT scanning with eight or more sections to avoid severe cone-beam artifacts. The question of cone correction also arises for cardiac CT with eight or more sections. Established ECG-gated multisection spiral reconstruction methods for four-section CT systems, such as the ACV algorithm, disregard the cone angle of the measurement rays: The rays are treated as if they

Discussion

In conclusion, the results of our patient studies support the use of 1-mm sections and medium-smooth kernels for initial clinical evaluation and as an input for three-dimensional volume rendering. A combination of 0.75-mm sections and sharp kernels should be used to depict severely calcified coronary branches or coronary stents. We achieved considerably improved visualization of calcified and noncalcified plaques and of stents with use of submillimeter section widths and optimized in-plane

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