| Objective: To explore the application value of spectral CT on multi-parameter imaging combined with anterior and posterior asir-v technique in portal vein examination to reduce the radiation dose and contrast agent usage.Methods: A total of 67 patients underwent CT portal vein examination in the First Affiliated Hospital of Anhui Medical University were collected and randomly divided into experimental group(32 cases)and control group(35 cases).In the experimental group,low iodine concentration(300mg I/ml)and low usage(1.0ml/kg)contrast agent were used and scanned with energy spectrum combined with anterior40% weight asir-v in portal phase,and conventional mode was used in plain scan,arterial phase and delayed phase.In the control group,high iodine concentration(350mg I/ml)and conventional usage(1.5ml/kg)contrast agent were used and scanned with conventional mode in plain scan and three-phase enhancement.The original spectral data of portal phase in the experimental group were uploaded to GE ADW4.7 workstation,and the following operations were carried out:(1)The optimal CNR program was selected to obtain the optimal CNR single energy value of the portal vein,and then the optimal CNR single energy image of the portal vein with posterior100% weight asir-v was reconstructed from the host.(2)The material suppressed iodine(MSI)program was selected to obtain the MSI image as the virtual non-contrast(VNC)image.Then two senior doctors used double-blind method to evaluate the image quality of portal vein in the experimental group and the control group,and the image quality of true non-contrast(TNC)and VNC in the experimental group.The subjective score,CT value,noise,signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR)of liver parenchyma and portal vein were compared between the experimental group and the control group.And the subjective score,CT value,noise and SNR of liver parenchyma,spleen parenchyma and pancreatic parenchyma in the TNC and VNC images of the experimental group were also compared.The number of lesions detected by TNC and VNC were counted by the experienced doctor,and the detection rate of lesions were compared.The effective dose and iodine intake were calculated and compared.When P < 0.05,the difference was statistically significant,otherwise,the difference was not statistically significant.Results(1)Comparison of portal vein image quality between the experimental group and the control group: the subjective score of portal vein image quality was 3.86 ± 0.51 in the experimental group and 4.11 ± 0.62 in the control group.There was no significant difference between the two groups(t =-1.72,P = 0.88).The differences of the CT values and noise of liver parenchyma,main portal vein,right branch and left branch were statistically significant(P<0.05),The CT values in the experimental group were higher than those in the control group,but the noise were lower 。 The differences of the SNR of liver parenchyma,main portal vein,right branch and left branch(experimental group: 14.04 ± 2.85,21.34 ± 6.74,20.45 ± 6.02,22.90 ± 6.63,control group: 6.60 ± 1.69,6.89 ± 1.40,7.46 ± 1.76,7.56 ± 1.73)and the CNR of main portal vein,right branch and left branch(experimental group: 13.60 ± 7.20,11.71 ± 6.99,11.51 ± 6.80,control group: 3.14 ± 1.35,3.16 ± 1.40,3.03 ± 1.19)were statistically significant,The experimental group were higher than the control group(T values were 13.14,11.90,11.74,12.68,8.06,6.80,6.95,P < 0.05).(2)The comparison of image quality between TNC and VNC in the experimental group: the image quality subjective score of TNC was 4.97 ± 0.12,and that of VNC was 4.47 ±0.49,the difference was statistically significant,the subjective score of TNC was slightly higher than that of VNC(t = 5.95,P < 0.05).The CT values of left lobe of liver,right lobe of liver,spleen and pancreas(TNC: 63.23 ± 7.64 HU,62.06 ± 7.55 HU,54.37 ± 2.82 HU,47.63 ± 8.08 HU,VNC: 58.58 ± 8.43 HU,55.35 ± 6.20 HU,47.89 ±2.86 HU,41.83 ± 6.87HU)were statistically significant,the CT values of TNC were higher than that of VNC(T values were 3.66,9.06,9.64,6.19,P < 0.05).The noise and SNR of left lobe of liver,right lobe of liver,spleen and pancreas were statistically significant(P < 0.05),The noise of TNC were higher than that of VNC,but the SNR were lower.There was no significant difference in the detection rate of lesions(P >0.05).In the experimental group,the iodine intake was reduced by 43%,and the effective dosage in portal phase was reduced by 48%.Conclusions: Multiparametric imaging with spectral CT combined with anterior and posterior asir-v technique is highly useful in portal vein examination.Among them,imaging with the optimal CNR single energy combined anterior and posterior asir-v technique can achieve portal vein image quality comparable to conventional techniques at low radiation dosage and low iodine intake.And the VNC can be used to replace the TNC,which further reduces the radiation dosage and also reduces the scanning time. |
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