Low radiation coronary calcium scoring by dual-source CT with tube current optimization based on patient body size

Abstract

Reducing tube voltage from 120 kV to 100 kV during noncontrast CT for the detection of coronary artery calcium reduces patient radiation exposure. We investigated whether coronary calcium scoring by multidetector row CT can be performed at reduced tube current, resulting in lower radiation dose to the patient. Sixty-six outpatients were scanned on the same visit by dual-source CT (DSCT) with a standard protocol (120 kVp, 150 mAs), followed by a scan with reduced tube current: 85 mAs for patients with body mass index (BMI) ≤ 30 kg/m(2) and weight ≤ 85 kg, and 120 mAs for patients with BMI > 30 kg/m(2) or weight > 85 kg. Low-dose scans were scored by an experienced reader blinded to the standard scan. Agatston scores (ASs) and calcium volume for standard versus low-dose scans were 236± 581 versus 234 ± 586 (P = 0.65, NS), and 189 ± 460 mm(3) versus 184 ± 455 mm(3) with excellent correlation (r = 1.0, P < 0.0001), and no significant difference (P = 0.14, NS). Effective radiation dose for the low-dose protocol (1.0 ± 0.2 mSv) was significantly lower than for the standard protocol (1.7 ± 0.2 mSv; P < 0.0001). Image noise was higher for the low-dose scan (18.8 ± 5.5 HUvs 15.2 ± 4.8 HU; P < 0.0001), but both were within target limits. Noncontrast CT for measurement of coronary artery calcium with lower tube current optimized for patient body size is equivalent to standard methods at 40% lower radiation dose, indicating that radiation dose can be lowered for coronary calcium scanning.