Takeshi Nakaura MD, Presenter: Nothing to Disclose

Kazuo Awai MD, Abstract Co-Author: Nothing to Disclose

Yumi Yanaga MD, Abstract Co-Author: Nothing to Disclose

Kazunori Harada, Abstract Co-Author: Nothing to Disclose

Shouzaburou Uemura, Abstract Co-Author: Nothing to Disclose

Yasuyuki Yamashita MD, Abstract Co-Author: Nothing to Disclose

Junichi Sata, Abstract Co-Author: Nothing to Disclose

The use of the smallest diagnostically appropriate amount of contrast media is highly desirable for patients with chronic kidney disease (CKD). The purpose of this study was to evaluate the feasibility of 40 percent reduced contrast dose protocol in hepatic dynamic CT with a low tube voltage-, high tube current-time product technique at 256-row CT.

This prospective study had institutional review board approval; informed consent was waived. We assigned 151 patients to 2 protocols according to the severity of CKD defined by estimated glomerular filtration rate (eGFR). For patients with eGFR above or equal to 60 ml/min/1.73m2, they were scanned at standard 120 kVp protocol with the standard dose contrast material (600 mgI/kg) during 30 sec. For patients with eGFR less than 60 ml/min/1.73m2, they were scanned at tube voltage 80 kV and tube current-time product 550-1100mAs/slice with the small amount of contrast media (360 mgI/kg) during 30 sec. We evaluated estimated effective dose (ED), image noise, attenuation and contrast-to-noise ratio (CNR) of the aorta in arterial phase, liver and portal vein in portal phase. Two independent readers assessed overall image quality, beam-hardening artifacts and vessel enhancement by using a 3-point scale. The 2 protocols were compared with Student t-test and two-sided Mann-Whitney’s U-test test.

One hundred seventeen patients were scanned using 120 kVp and 34 patients were scanned using 80 kVp. Estimated ED was 21% and 23% lower at 80 kVp than at 120 kVp. Image noise at 80 kVp was significantly higher than at 120 kVp, however, attenuations of the aorta, portal vein and liver were significantly greater at 80 kVp than at 120 kVp (P<0.01). There were no significant differences in CNR of the aorta, portal vein and liver between 80 kVp and 120 kVp (28.4 ± 7.3 vs 29.6 ± 7.3, P=0.41; 11.8 ± 3.7 vs 11.5 ± 2.9, P=0.62 and 5.8 ± 2.9 vs 5.9 ± 2.1, P=0.83; respectively). There were no significant differencse in the visual scores.

For hepatic dynamic CT of patients with CKD, the setting of 80 kVp and a high tube current-time product offers almost the same image quality under 40% reduced contrast media with over 20% reduced radiation dose as compared with standard 120 kVp protocol at 256-row CT.

Low kVp scan using 256-row CT is applicable for hepatic dynamic CT of patients with renal dysfunction.

Nakaura, T, Awai, K, Yanaga, Y, Harada, K, Uemura, S, Yamashita, Y, Sata, J, Hepatic Dynamic CT in Patients with Renal Dysfunction: Forty-Percent Contrast-Dose Reduction Using Low Tube Voltage and High Tube Current Time Setting at 256-Row Computed Tomography.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9013853.html