Liver perfusion CT during hepatic arteriography for the hepatocellular carcinoma: dose reduction and quantitative evaluation for normal- and ultralow-dose protocol.

OBJECTIVES

The purpose of this study was to investigate whether substantial reduction of the computed tomography (CT) dose is possible in liver CT perfusion imaging by comparing the results of ultralow-dose CT perfusion imaging with those of conventional CT perfusion imaging the same patients and under the same conditions.

MATERIALS AND METHODS

The study was composed following two parts: computer simulation and patients study. In computer simulation, noise was added to the images so that the standard deviation (SD) of the CT values in the liver parenchyma became various values using ImageJ. Time density curves (TDCs) were created from the simulated data, and the influence of difference in the SDs on the shapes of the TDCs was investigated. In the patient study, CT perfusion during intra-arterial injection was performed in 30 consecutive patients undergoing transcatheter arterial chemoembolization. CT perfusion images were acquired twice, at 100 mA (CTDI(vol), 300 mGy) for normal and at 20 mA (CTDI(vol), 60 mGy) for the ultralow radiation doses, under the same conditions.

RESULTS

No change was observed in the shape of the TDCs and peak values in the analysis of simulation images. A very good correlation was observed between the normal- and ultralow-dose CT images for all analyzed values (R(2)=0.9885 for blood flow, 0.9269 for blood volume, and 0.8424 for mean transit time).

CONCLUSIONS

Our results demonstrated that there was no significant difference in the analysis results of perfusion CT between ultralow-dose CT performed using 20% of the conventional dose and normal-dose CT perfusion.