Charles Shaughnessy

Optimal cardiac phase in prospectively gated axial cardiac CT scans

To improve temporal resolution in prospectively gated axial cardiac CT scans, short scan (half-scan, partial scan) is used for image reconstruction. While some vendors offer scanners with 16cm collimation, capable of collecting entire heart data in a single rotation, the majority of routine cardiac scans are still done with 4cm collimation. In case of a prospective axial cardiac scanning, four or more axial acquisitions are performed at staggered patient table positions to cover the entire heart. At each acquisition, raw data is collected at the prescribed phase of cardiac R-R interval with the range of the x-ray source angles covering one or less than one rotation. If this angle range is greater than what is required for a short scan reconstruction, it allows some room for optimizing the reconstruction phase. Often, such optimization is done by manually reviewing images at slightly different reconstruction phase angles, and selecting the images with the least pronounced motion artifacts. Considering there are at least four acquisitions for each prospective cardiac scan, this may become a tedious time-consuming process. This paper proposes an automated process to select the best short-scan view range within full rotation acquisitions that minimizes motion artifacts at each table position. The proposed method was tested with a motion phantom which was connected to an ECG simulator and clinical cardiac data. Results show that the proposed method reliably provides reduction of motion artifact in reconstructed images.