Purpose

To reduce radiation dose to patients undergoing multiphasic CT of the liver by exploiting the intrinsic properties of iodine enhancement at low kVp.

Material and methods

59 oncology patients underwent multiphasic CT of the liver using a 256 slices scanner either with our standard acquisition protocol (100 kVp in all phases; N=27) or an optimised weight-based acquisition protocol in the arterial phase (80 kVp in patients <=80 kg; N=21, average BMI 23,2 and 100 kVp in patients >80 kg; N=11, average BMI 30,1). High-concentration contrast agent @1.3 ml/kg, @3 ml/s (Iomeprol 400 mgI/ml) and automatic tube current modulation were used in all patients. The standard dose and the optimised protocols were compared with t-test for average CTDI_vol, liver dose, peak aortic enhancement at the coeliac trunk. Five radiologists completed a 6-item Image Quality Score.

Significance threshold p <0.05.

Results

With the optimised protocol, patients <=80 kg showed significant increase in peak aortic enhancement (466±134HU vs 324±59HU; p=0,003) and significant reduction in average CTDI_vol (14±4.8 vs 8.6±1.5 mGy; p=0,000001) and liver dose (17.7±5.9 vs 10.7±1.8 mSv; p=0,002) for the arterial phase. As expected, patients >=80 kg did not show any significant difference in aortic enhancement and radiation dose compared to the standard protocol. No significant difference in image quality was reported.

Conclusion

Our optimised protocol using 80 kVp and high iodine concentration resulted in an improvement of aortic attenuation and radiation dose reduction in patients <=80 kg. Our tailored approach increases peak aortic enhancement by 44% and reduces liver dose by 40% in the arterial phase without sacrificing clarity.