The Clinical Application Of Energy Spectrum CT In Improving The Image Quality Of CT Colonography

Objective:To apply energy spectrum CT to intestinal content labeling CT Colonography(CTC),to explore the improvement of Virtual Monoenergetic Imaging(VMI)on the image quality of CTC,to study the value of energy spectrum imaging in CTC,and to compare it with Quality Control(QC)images to determine the best VMI to show the colon and its adjacent organs,so as to analyze the feasibility of applying energy spectrum CT to CTC.Methods:A total of 30 patients who underwent CT colonography in Inner Mongolia International Medical Hospital from August 2016 to November 2019 were collected.The patients’ intestines were prepared with iohexol and barium sulfate combined with Bisacodyl for three days,and then inflated and dilated on an empty stomach.CT scans were performed in supine position and prone position in turn,and the obtained images were reconstructed by AW4.7 workstation for Multiplanar Reformation(MPR)and VMI and QC images.The subjective scores and noise values of axial and MPR VMI and QC images,and the Signal to Noise Ratio(SNR)and Contrast to Noise Ratio(CNR)of colon,liver,spleen,pancreas,kidney,adrenal gland,prostate and uterus were compared to comprehensively evaluate the effect of energy spectrum CT on the quality of CTC images.Results:1.47 cases of Extracolonic Finding(ECF)were found in 30 patients.According to C-RADS E score,there were 7 cases of E1,21 of E2,2 of E3,and 0 of E4.The classification of organ system is as follows:vascular(42.55%),genitourinary(21.28%),liver(19.15%),gynecologic(6.38%),gastrointestinal(4.26%),spine(4.26%)and adrenal(2.13%).2.The consistency of subjective scores of the two observers was very good in axial position and MPR,and the Kappa values were 0.879 and 0.851,respectively,while the CT values of abdominal fat,SD value of abdominal fat density,colonic intestinal wall CT value and adrenal CT value were very consistent,and the ICC values were 0.934-0.950,0.978-0.997,0.756-0.816 and 0.835-0.874,respectively.The CT values of liver,spleen,pancreas,kidney,prostate and uterus were consistent.The ICC values were 0.5760.665,0.645-0.743,0.602-0.688,0.702-0.769,0.631-0.753 and 0.567-0.704 respectively.3.The average subjective score in axial QC image and 40-140keV(gradient 10)VMI image was 3.37±0.69,3.10±0.68,3.47±0.72,3.9±0.60,4.53±0.50,4.37±0.55,4.27±0.51,4.17±0.49,3.98±0.54,3.8±0.55,3.70±0.59,3.5±0.72,respectively.The subjective average of QC image and 40-140keV level VMI image in MPR images were 2.85±0.86,2.57±0.89,2.97±0.89,3.48±0.79,4.02±0.65,3.95±0.65,3.85 ±0.66,3.81 ±0.62,3.62±0.67,3.52 ±0.68,3.42 ±0.67,3.32 ±0.70 respectively.Both axial and MPR images were reconstructed at 70keV level,and the subjective score of image quality was the highest.4.In both axial and MPR images,the image noise decreased from 40keV to 140keV VMI as a whole,and when the 70keV virtual single energy images reached a relatively low point,this value was significantly lower than that of QC images(taxial=15.373,P<0.01,tMPR=87.204,P<0.01),and then increased and decreased again to the lowest point of 140keV.5.The SNR and CNR of colon wall showed an increasing trend from 40keV to 140keV single energy image,and reached the highest value in 70keV virtual single energy image,then decreased and increased again.The SNR and CNR of 70keV virtual single energy images were significantly higher than those of QC images(P<0.01).6.The change trend of SNR and CNR of liver,spleen,pancreas,kidney,prostate and uterus was similar,from 40keV to 140keV VMI showed an increasing trend,to 70keV virtual single-energy image reached a relative high point,and then decreased and rose again to 140keV VMI reached the highest value.The SNR and CNR of 70keV virtual single energy images were significantly higher than those of QC images(P<0.01).7.The adrenal SNR and CNR showed an increasing trend from 40keV to 140keV single-energy images,and reached the highest value in 70keV virtual single-energy images,then decreased and rose to a relative high point,and then decreased again.And the SNR and CNR of 70keV virtual single energy images are significantly higher than those of QC image(P<0.01).Conclusion:Energy spectrum CT has the ability to improve the CTC image quality of intestinal content labeling,and the best images to show the colon wall and extracolonic abdominal and pelvic organs is 70keV virtual single energy images.