Influence of heart rate on image quality to identify the best cardiac phase in 16-slice coronary CT angiography.
OBJECTIVE
To identify the best cardiac phase in different patient's heart rate on 16-slice coronary CT angiography.


METHODS
The patients who had undergone coronary CT angiography with 16 multi-detector rows CT at Siriraj Hospital between September 2003 and August 2004. For each patient, the image reconstruction based on relative timing was performed placed at center of 35% to 85% of the R-R interval with step increments 10%. The authors created six data sets (35%, 45%, 55%, 65%, 75%, and 85% of R-R interval) throughout the cardiac cycle. The coronary arteries were reviewed based on cross-sectional images and reformat images. The authors inspected all data sets and selected the cardiac phase that contained the best image quality for each coronary artery.


RESULTS
Five hundred sixty four vessels were evaluated in the 141 patients (83 men, 58 women). The mean patient age was 63.3 +/- 16.7 years (range 4-89 years). Mean patient heart rate was 65.7 +/- 16.5 beats per minute (bpm), range 46-104 bpm. The most coronary arteries were well demonstrated at center of 75% of R-R interval (66.8%). Ninety-eight patients (69.5%) required one phase that provided best overall image quality and motion free delineation for four coronary arteries. Forty-three patients (30.5%) required combination of data from each phase to achieve motion free images.


CONCLUSIONS
The best cardiac phase of evaluate coronary artery in 16 slices coronary CT angiography in the patient's heart rate below 70 bpm is 75% of cardiac cycle (mid to late diastole). In patients with a heart rate 71-80 bpm, the authors required a combination of images from 45% and 75% of cardiac cycle to completely evaluate all coronary arteries. In patients with a heart rate above 80 bpm, 45% of cardiac cycle (end-systole) is the best phase.
Department of Radiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Sureeporn
S
Mayurasakorn
Thanongchai
T
Siriapisith
Jitladda
J
Wasinrat
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D017023:Coronary Angiography / Q000295:instrumentation*; D003331:Coronary Vessels / Q000033:anatomy & histology / Q000502:physiology*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects