Optimization of temporal resolution in CT using retrospective ECG-gating

Purpose: Spiral CT of the heart using the established ways of ECG synchroni zation is hampered by the relatively long acquisition times of 250 to 500 m s. This only allows to acquire diastolic images in patients with moderate h eart rates. In this work, algorithms for time-optimized retrospective cardi ac gating are presented,and their potential to improve temporal resolution is investigated. Material and methods: These algorithms use data from multiple gantry rotati ons for image reconstruction,which is possible for multi-scans at fixed sli ce positions as well as for overlapping spiral scans. Temporal resolution w as quantified using computer simulations and compared to experimental data from pigs. Results: Using a conventional sub-second CT scanner, considerably higher te mporal resolutions are possible with spiral scanning. A temporal resolution of 170 ms already provides systolic images with little motion artifacts. H igher temporal resolutions of up to 70 ms are demonstrated for multi-scans, wh ich allows to depict ventricle wall movement over the complete cardiac cycle. Discussion: The method of time-optimized retrospective cardiac gating broad ens the spectrum of conventional spiral-CT for cardiac imaging. It can be d irectly transferred to multi-slice scanners. Here it can be used clinically because of reduced scan time. Potential applications are the determination of functional cardiac parameters like ejection fraction and the detection of disorders of ventricle wall movement.