Low-contrast-dose protocol in cardiac CT: 20% contrast dose reduction using 100 kVp and high-tube-current-time setting in 256-slice CT.

BACKGROUND

The use of the smallest contrast dose is highly desirable in performing cardiac computed tomography (CT), especially for patients with cardiovascular diseases to prevent contrast-induced nephropathy.

PURPOSE

To evaluate the feasibility of 20% reduced contrast dose protocol in cardiac CT using 100 kVp and high-tube-current-time product setting.

MATERIAL AND METHODS

Fifty patients were scanned with our conventional 120 kVp protocol, and the other 50 patients underwent scans using a tube voltage of 100 kVp, a high-tube-current-time product, and a 20% reduced contrast dose. We evaluated estimated effective dose (ED), CT attenuation, image noise, and contrast-to-noise ratio (CNR) of the ascending aorta. We also evaluated CT attenuation of the coronary arteries. Two radiologists independently assessed image quality of coronary arteries.

RESULTS

There was no significant difference in the ED between the 100 kVp and 120 kVp protocols (21.7 mSv ± 1.6 vs. 21.8 mSv ± 1.1, P=0.65). There was no significant difference in the CNR of the ascending aorta between the 100 kVp and 120 kVp protocols (18.8 ± 3.5 vs. 18.7 ± 3.8, P=0.98). Mean CT attenuation of the coronary arteries of the 100 kVp protocols was significantly higher than that of 120 kVp protocols (P<0.05). There was no significant difference in the overall image quality of the coronary artery between the 100 kVp and 120 kVp protocols (3.7 ± 0.4 vs. 3.7 ± 0.5, P=0.65).

CONCLUSION

For cardiac CT a voltage setting of 100 kVp and a high-tube-current-time product enable 20% reduction in the contrast dose without affecting the quality of coronary artery images compared with a 120 kVp and standard-contrast-dose CT protocol.