Journal of Cardiovascular Computed Tomography (2011) 5, 149-157
Ryo Nakazato, MD, PhD, Balaji K. Tamarappoo, MD, PhD, Thomas W. Smith, MD, Victor Y. Cheng, MD, Damini Dey, PhD, Haim Shmilovich, MD, Ariel Gutstein, MD, Swaminatha Gurudevan, MD, Sean W. Hayes, MD, Louise E. J. Thomson, MBChB, John D. Friedman, MD, Daniel S. Berman, MD
BACKGROUND: Electrocardiographic (ECG)-based tube current modulation during cardiac CT reduces radiation exposure but significantly increases noise in parts of the cardiac cycle where tube current is minimized.
OBJECTIVE: We evaluated the effect of maximal ECG-based tube current reduction on left ventric- ular (LV) regional wall motion assessment and ejection fraction (EF) by comparing low-radiation hel- ical dual-source CT (DSCT) to 2-dimensional transthoracic echocardiography (2D-TTE).
METHODS: We studied 83 consecutive patients (15 with prior myocardial infarction) who underwent helically acquired DSCT coronary angiography with maximal ECG-based tube current modulation (low-radiation helical DSCT) and 2D-TTE within a 6-month period (median, 1 day), without any change in clinical status between the studies. In all patients, full tube current was applied only at 70% of the R-R interval, with minimal tube current (4% of maximum) in all other parts of the cardiac cycle. Reduced tube voltage (100 kVp) was combined with the maximal dose modulation in 34 patients. DSCT datasets were evaluated by a blinded, experienced cardiologist. Regional wall motion was assessed with the stan¬dard 17-segment model, with each segment scored as normal, hypokinetic, akinetic, and dyskinetic.
RESULTS: Mean effective radiation dose for the low-radiation helical DSCT was 5.2 ± 1.7 mSv. Regional wall motion was evaluable in all segments on low-radiation helical DSCT. There was excellent