Image quality and radiation dose of low tube voltage 3rd generation dual-source coronary CT angiography in obese patients: a phantom study

Objectives To assess the influence of tube potential on radiation dose and image quality of third-generation dual-source coronary CT angiography (CTA) in a phantom simulating an obese patient. Methods A thoracic phantom was equipped with tubular inserts containing iodine solution and water. A soft-tissue-equivalent ring around the phantom simulated an obese patient. Images were acquired at tube potentials of 80, 100, 120 and 140 kV with second-generation dual-source CT (DSCT) and 70–150 kV (in 10-kV increments) with third-generation DSCT. Contrast-to-noise ratio (CNR) was calculated and CT dose index was recorded. Results With second-generation DSCT, CNR was highest for 120 kV (19.0) and decreased with lower tube potential (12.0 at 80 kV) owing to disproportionately increased image noise. With third-generation DSCT, 70- and 80-kV acquisitions showed a smaller increase in noise. CNRs for third-generation DSCT were highest for 70 and 80 kV (21.1 and 21.2, respectively). Compared to 120 kV, radiation dose was 68 % and 49 % lower at 70 kV and 80 kV, respectively. Conclusion Third-generation DSCT enables one to perform coronary CTA at 70–80 kV in obese patients without compromising CNR and thus reduces radiation dose by 49–68 %. Key points • Low tube potential CT angiography is currently not suitable for obese patients . • Third-generation DSCT offers substantially increased tube power at low tube potential . • This enables one to perform coronary CT angiography at 70–80 kV in obese patients . • Signal-to-noise ratio is maintained owing to increased tube current . • This approach can be expected to reduce radiation dose by 49–68 % .