Lowering radiation exposure in CT angiography using automated tube potential selection and optimized iodine delivery rate.

OBJECTIVE

The purpose of this study was to determine the effectiveness of a radiation dose reduction strategy for CT angiography by the combination of higher iodine delivery rate and automated tube potential selection with adjusted reference values for tube current-exposure time product, as well as to measure the impact of this approach on image quality.

SUBJECTS AND METHODS

One hundred consecutive patients underwent high-pitch CT angiography of the thorax and abdomen using either 90 mL of iomeprol 300 (n = 44, protocol A) or 90 mL of iomeprol 400 (n = 56, protocol B) at the same flow rate. Automated tube potential selection was used with reference tube current-time products of 330 mAs and 250 mAs for protocols A and B, respectively. Twenty vascular segments were analyzed for attenuation and image noise by two readers. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated for all segments. The dose-length product (DLP) was documented to calculate effective dose and was compared between protocols both globally and for body mass index (BMI) subgroups.

RESULTS

There were no differences in sex, height, weight, or BMI between both groups. Images from patients scanned with protocol B showed higher levels of image noise but also higher signal in all vascular segments. As a result, there were no differences in SNR between both groups. Conversely, CNR was significantly higher for almost all vascular segments in the group scanned using protocol B. Furthermore, DLP was significantly lower when protocol B was used, particularly in patients with a BMI of less than 30.

CONCLUSION

In CT angiography, a combination of higher iodine delivery rate and automated tube potential selection with adjusted reference values for the tube current-time product allows reductions in radiation dose by approximately 30% without compromising image quality.