Two hundred and ten patients underwent prospectively triggered coronary CTA for suspected or known coronary artery disease (CAD). Patients with heart rate >75 bps before the scan despite ?-blocker administration and with arrhythmia were excluded. From January to September 2010, 60 patients underwent coronary CTA using a non-tailored protocol (120 kV; 200 mAs) and served as our ¡®control¡¯ group. From September 2010 to April 2012, based on the body mass index (BMI) of the examined patients (BMI subgroups of < 25; 25-28; 28-30, and ¡Ý 30 kg/m2) current tube voltage and tube current were: (1) slightly, (2) moderately or (3) strongly reduced, resulting into the 3 following BMI-adapted acquisition groups: (1) a ¡®standard¡¯ (100/120 kV; 100-200 mAs; n = 50), 2) a ¡®low dose¡¯ (100/120 kV; 75-150 mAs; n = 50), and 3) an ¡®ultra-low dose¡¯ (100/120 kV; 50-100 mAs; n = 50) protocol.
Patients examined using the non-tailored protocol exhibited the highest radiation exposure (3.2 ¡À 0.4 mSv), followed by the standard (1.6 ¡À 0.7 mSv), low-dose (1.2 ¡À 0.6 mSv) and ultra-low dose protocol (0.7 ¡À 0.3 mSv) (radiation savings of 50 % , 63 % and 78 % respectively). Overall image quality was similar with standard dose (1.9 ¡À 0.6) and low-dose (2.0 ¡À 0.5) compared to the non-tailored group (1.9 ¡À 0.5) (p = NS for all). In the ultra-low dose group however, image quality was significant reduced (2.7 ¡À 0.6), p < 0.05 versus all other groups).
Using BMI-adapted low dose acquisitions image quality can be maintained with simultaneous radiation savings of ¡«65 % (dose of ¡«1 mSv). This appears to be the lower limit for diagnostic coronary CTA, whereas ultra-low dose acquisitions result in significant image degradation.