Coronary CT Angiography with 80 kV Tube Voltage and Low Iodine Concentration Contrast Agent in Patients with Low Body Weight

Background: Coronary CT angiography (CTA) is gaining widespread acceptance for the non-invasive evaluation of coronary arteries. However, radiation exposure and administration of iodinated contrast agents are still reasons of some concern. The 80 kV tube voltage increases the attenuation of iodine, allowing to use lower iodine concentration contrast agents for coronary CTA.

Objective: We evaluated the diagnostic accuracy of coronary CTA performed with 64-slice scanner, 80 kV tube voltage, iterative reconstruction algorithm and ultra-low concentration contrast medium to reduce iodine load and radiation dose.

Methods: We enrolled 45 patients with low body weight and indication for elective invasive coronary angiography (ICA). All patients received an 80 ml bolus of Iodixanol-270 at an infusion rate of 5 mL/s and underwent coronary CTA (80 kV and 500-550 mA) with prospective ECG-triggering. Image quality score, type of artifacts, coronary CTA evaluability, diagnostic accuracy and radiation exposure were assessed.

Results: Pre-test probability of CAD was low-to-intermediate (48%). Accordingly, the prevalence of obstructive CAD was 47% (21 out of 45 patients). Most (93%) of the patients were pre-treated with intravenous metoprolol before scanning and achieved a heart rate suitable for prospective ECG-triggering coronary CTA (53 ± 3 bpm). The mean effective dose and iodine load were 1.1 ± 0.4 mSv and 21.6 gI, respectively. We rated 443 out of 720 coronary segments as being of excellent image quality. In a segment-based model, coronary evaluability (number of coronary segments evaluable/total number of coronary segments), was 97% (699/720 segments). In a segment-based analysis, sensitivity, specificity, positive predictive value, negative predictive value and accuracy for >50% coronary stenosis identification vs. ICA were 89%, 99%, 89%, 99% and 99%, respectively. In a patient-based analysis, sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 94%, 89%, 83%, 96% and 91%, respectively.

Conclusions: In patients with low body weight, image quality and diagnostic accuracy of ultra-low radiation dose and low-iodine load coronary CTA are good and similar to values reported in the literature for standard tube voltage and iodine load protocols.