Feasibility study of contrast-enhanced hepatic CT with low tube voltage using iterative model reconstruction technique

Abstract

Objective To investigate the feasibility of contrast-enhanced CT with low tube voltage using iterative model reconstruction(IMR) technique. Methods Sixty patients were randomly assigned into 2 groups (group A and group B, 30 each) according to random number table. All patients underwent contrast-enhanced hepatic CT. Group A was scanned with 100 kV at arterial phase(AP) and 120 kV at portal vein phase (PVP), while group B was scanned with 120 kV at AP and 100 kV at PVP. All protocols were performed at the same tube current of 250 mAs. Raw data were reconstructed with IMR for AP images in group A and PVP images in group B; and reconstructed with FBP for AP images in group B and PVP images in group A. Images of 4 different groups were obtained: A1(AP, 100 kV, IMR), B1(AP, 120 kV, FBP), A2(PVP, 120 kV, FBP) and B2(PVP, 100 kV, IMR). Subjective evaluation indexes for image quality including low-contrast detectability, lesion edge sharpness, image distortion and diagnostic confidence. Objective evaluation indexes included CT attenuation of hepatic parenchyma, image noise, SNR and CNR, which were assessed and compared between groups A1 and B1, groups A2 and B2. Effective radiation doses were calculated. Results Effective dose in group A1 was reduced 35.1% compared to B1 (t=11.05, P 0.05). Significantly lower image noise and higher SNR/CNR were found in group A1 compared to group B1(t=12.889, 15.458, 1.325, P<0.01), as well as in group B2 compared to group A2(t=15.163, 15.308, 3.136, P<0.01). Conclusions Significant radiation dose reduction and image quality improvement in contrast-enhanced hepatic CT can be reached by using low tube voltage protocol combining with IMR technique. Key words: Iterative model reconstruction(IMR); Hepatic; Tomography, X-ray computed; Radiation dosage; Image quality