Practical Tips and Tricks for Salvaging ECG-gated Cardiac CT from Motion Artifacts

Despite technical advances and careful preparation, motion artifacts are commonly encountered in cardiac CT. Artifacts due to patient motion or breathing are not correctable and may necessitate repeat scanning; however, cardiac motion artifacts may be mitigated without repeating the scan. Cardiac motion artifacts may manifest as blur, transition, interpolation, or duplication. Blur artifact due to mismatch between cardiac motion speed and the scanner's temporal resolution can be mitigated by using a different cardiac phase, a motion-correction algorithm, or multisegment reconstruction. Transition artifact at the interface between different scanned segments with different R-R interval lengths may be mitigated by using a different cardiac phase or edge-correction algorithms. Interpolation artifact results when the pitch is too high for the heart rate (HR) at some point of a retrogated scan, either due to the patient taking a deep breath, missing electrocardiographic (ECG) synchronization (sync)-points, or long ECG pauses after premature atrial contractions (PACs) or premature ventricular contractions (PVCs). The scanner fills the data gaps by interpolating (ie, "smearing") data from above and below the gap. Duplication artifact results when the pitch is too low for the HR at some point of a retrogated scan, due to contrast material injection, medications, premature or extra beats, or spurious ECG sync-points. Interpolation and duplication artifacts can often be mitigated by manipulating ECG sync-points. In sync-point editing, sync-points are added (eg, for a missed R wave) or deleted (eg, tagging of a tall T wave, exercise spike, or bifid R waves) such that every R wave (and only R waves) are tagged. In sync-point composing, sync-points are artificially manipulated to improve image quality in arrhythmias with variable R-R intervals (eg, PACs or PVCs, atrial fibrillation). ^©RSNA, 2025 Supplemental material is available for this article. See the invited commentary by Ufuk and Landeras in this issue.