Cardiac imaging in diagnostic VCT using multi-sector data acquisition and image reconstruction : step-and-shoot scan vs. helical scan

Since the advent of multi-slice CT, helical scan has played an increasingly important role in cardiac imaging. With the availability of diagnostic volumetric CT, step-and-shoot scan has been becoming popular recently. Step-and-shoot scan decouples patient table motion from heart beating, and thus the temporal window for data acquisition and image reconstruction can be optimized, resulting in significantly reduced radiation dose, improved tolerance to heart beat rate variation and inter-cycle cardiac motion inconsistency. Multi-sector data acquisition and image reconstruction have been utilized in helical cardiac imaging to improve temporal resolution, but suffers from the coupling of heart beating and patient table motion. Recognizing the clinical demands, the multi-sector data acquisition scheme for step-and-shoot scan is investigated in this paper. The most outstanding feature of the multi-sector data acquisition combined with the step-and-shoot scan is the decoupling of patient table proceeding from heart beating, which offers the opportunities of employing prospective ECG-gating to improve dose efficiency and fine adjusting cardiac imaging phase to suppress artifacts caused by inter-cycle cardiac motion inconsistency. The improvement in temporal resolution and the resultant suppression of motion artifacts are evaluated via motion phantoms driven by artificial ECG signals. Both theoretical analysis and experimental evaluation show promising results for multi-sector data acquisition scheme to be employed with the step-and-shoot scan. With the ever-increasing gantry rotation speed and detector longitudinal coverage in state-of-the-art VCT scanners, it is expected that the step-and-shoot scan with multi-sector data acquisition scheme would play an increasingly important role in cardiac imaging using diagnostic VCT scanners.