The optimal time point in RR interval for data reconstructioin to visualize coronary arteries by multi slice computed tomography.

Purpose: Multislice spiral CT is a newly developed technology that allows the non-invasive detection of coronary stenoses and plaques. The acquired raw data are reconstructed at a given time point in the RR interval of the heart cycle. Thus, determination of this time point is a key factor for picture quality and for reliable diagnostic results. This study was performed to investigate the optimal time point for reconstruction within the RR interval. Materials and Methods: The coronary arteries of 13 patients were examined with CT. Raw data were reconstructed 250, 350, 450 and 550 ms before the following R wave (absolute reverse retrospective ECG gating) for each patient. Data were then analyzed with a volume rendering mode on a SIEMENS 3 D-Virtuoso workstation. A total of 91 segments (segments 1 and 2 of the RCA, segments 5, 6, 7 and proximal and distal parts of segment 11) were assessed and image quality was classified. Results: Visualization of the left main coronary artery was of a good quality at all time points, segments 6 and 7 of the LAD as well as the proximal and distal parts of segment 11 of the RCX had the best quality at 450 ms absolute reverse retrospective ECG gating. The segments 1 and 2 of the RCA were of best quality 550% ms absolute reverse to the R peak. Conclusions: Classification of image quality of coronary artery CT scans after retrospectively ECG gated reconstruction is highly determined by the time point of reconstruction in the heart cycle. The optimization of this time point increases diagnostic accuracy and helps to avoid misinterpretation due to image artifacts.