Optimal electrocardiographically triggered phase for reducing motion artifact at electron-beam CT in the coronary artery

Rationale and Objectives. The authors performed this study to (a) investiga te coronary movement with electron-beam computed tomography (CT) and (b) fi nd the optimal electrocardiographic (ECG) triggering phase for eliminating motion artifact. Materials and Methods. One hundred fifty-one patients without arrhythmia we re examined with electron-beam CT. First, movie scans were obtained to crea te displacement and velocity graphs of coronary artery movement. Then, a vo lume scan with an exposure time of 100 msec was obtained with various ECG t rigger settings. Results. Movement patterns of coronary arteries varied with heart rate. Opt imal triggering phase was before atrial systole (near 71% of the R-R interv al) when heart rate was slower than 68 beats per minute and at ventricular end systole when heart rate was fast. Rate of severe motion artifacts decre ased from 43% to 0% when triggering was altered from 80% of the R-R interva l to the individual optimal value. Experimental values of the optimal phase at different heart rates were derived, and severe motion artifact was only 3.0% with these values. Conclusion, ECG triggering set according to the heart rate enables a great reduction in motion artifacts at electron-beam CT with a 100-msec exposure time. The results may have implications for magnetic resonance imaging of t he coronary arte rv.