Applied Research Of Contrast-Enhanced Hepatic CT With Low Tube Voltage Using Iterative Model Reconstruction Technique

CT enhanced scan is an important method to diagnose hepatic disease, particularly hepatic cancer patients who had done surgery, they need for repeated review, then increase the radiation dose to the patient, over time the cumulative effect of multiple doses of the body will cause great harm [1].Simply optimize scanning protocols such as automatic control tube current, reduce the tube voltage can also reduce the radiation dose, but usually affects the image quality. Due to the hepatic and other organs lack of good natural contrast, conventional filtered back projection(FBP) reconstruction techniques will increase noise and artifact while reduce radiation dose,thereby reducing the image quality and then impact diagnosis disease [2]. Some scholars have been reported for FBP, iterative reconstruction(IR) technology can maintain the image quality in low radiation dose conditions [3], but the majority of commercial iterative reconstruction technique is a partial iteration, noise reduction in a limited extent, The image is distorted heavier [4,5].The iterative model reconstruction(IMR) technology is a new all-iterative reconstruction technique, could further reduce image noise and improve image quality [6].The Study is investigating feasibility of Contrast-Enhanced Hepatic CT with Low Tube Voltage Using Iterative Model Reconstruction Technique. Objective:To investigate the feasibility of contrast-enhanced CT with low tube voltage using iterative model reconstruction(IMR) technique. Materials and Methods:60 patients were randomly assigned into 2 groups(group A and group B, 30 for each) according to random number table. All patients underwent contrast-enhanced hepatic CT. Group A was scanned with 100 k V at arterial phase(AP) and 120 k V at portal vein phase(PVP), while group B was scanned with 120 k V at AP and 100 k V at PVP. All protocols were performed at the same tube current of 250 m As. 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 acquired: A1(AP,100 k V,IMR), B1(AP,120 k V,FBP),A2(PVP,120 k V,FBP) and B2(PVP,100 k V,IMR). Subjective image quality including low-contrast detectability, lesion edge sharpness, image distortion and diagnostic confidence as well as objective image quality including CT attenuation of hepatic parenchyma, image noise, SNR and CNR were assessed and compared between group A1 and group B1, group A2 and group B2. Effective radiation dose was recorded. Results:Effective radiation dose in group A1 was reduced 35.1% compared to B1(t=11.05,P<0.001), while reduced37.7% in group B2 compared to A2(t=11.64,P<0.001). Subjective image quality score of low-contrast detectability and lesion edge sharpness were significantly higher in group A1 compared to B1(Z=6.391,3.200,P<0.01), as well as in group B2 compared to A2(Z=6.559,3.409,P<0.01). No difference were found in image distortion and diagnostic confidence between group A1 and B1, group A2 and B2, respectively(all,p>0.05). Significant lower image noise and higher SNR/CNR were found in group A1 compared to B1(t=12.889, t=15.458,t=1.325,P<0.01), as well as in group B2 compared A2(t=15.163, t=15.308,t=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.