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/m2 and weight ?85 kg, and 120 mAs for patients with BMI > 30 kg/m2 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?¡À 581 versus 234 ¡À 586 (P = 0.65, NS), and 189 ¡À 460 mm3 versus 184 ¡À 455 mm3 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 ¡À 0.2 mSv) was significantly lower than for the standard protocol (1.7 ¡À 0.2 mSv; P < 0.0001). Image noise was higher for the low-dose scan (18.8 ¡À 5.5 HU?vs 15.2 ¡À 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.