Comparison of image quality of 64-slice multidetector CT coronary CT angiography using automated and manual multiphase methods for the determination of optimal phases for image reconstruction in patients with various mean heart rates

This study aimed to compare the effects of the automated and manual methods for determining the optimal phase of image reconstruction with the use of 64-slice coronary CT angiography (CCTA). In 63 patients, the optimal trigger delay was determined using an automated technique (PhaseXact) and by manual phase selection from the images reconstructed at a 10 ms and 1% increment of the R-R interval. The image quality was evaluated using four-step grading. The mean heart rate in all the patients was 70 ± 10.1 bpm (range: 52-98 bpm). The frequency of obtaining diagnostic quality images was highest with the manual absolute timing method (97.6% of 753 segments), while it was 94.7% with manual relative timing and 91.9% with an automated method. The mean image quality score (1.3 ± 0.2) based on the manual absolute timing was significantly better (P = 0.002, one-way ANOVA; P < 0.05, Scheffe's test) than the scores determined with the use of the other two techniques (manual relative timing, 1.4 ± 0.3; automated method, 1.5 ± 0.4). The best quality coronary CT images were obtained using image reconstruction with manual absolute timing for the ECG-trigger delay, while an automated method and manual relative timing provided diagnostic quality images in most of the segments.